Novel amphoteric super-slow-release polycarboxylic acid slump retaining agent and preparation method thereof

Abstract

The invention relates to the technical field of concrete, in particular to a novel amphoteric super-slow-release polycarboxylic acid slump retaining agent and a preparation method thereof. The method comprises the following steps: mixing and dissolving an unsaturated polyether macromonomer with water, adding a pH regulator, a first part of acrylic acid and an acrylic acid derivative, stirring, adding a first part of a reducing agent and an initiator, dropwise adding a dropwise adding solution A and a dropwise adding solution B at the same time, and carrying out a heat preservation reaction after dropwise adding is completed. The initiator is a composite initiation system composed of peroxides and azo; the dropping liquid A comprises a second part of acrylic acid, unsaturated carboxylic ester and phosphate monomers, and the dropping liquid B comprises a second part of a reducing agent and a chain transfer agent. According to the method, ordered copolymerization of multiple functional monomers is realized through a composite initiation and step-by-step dropwise adding process, and the prepared slump retaining agent has excellent initial dispersity and super-long slump retaining capacity, and is suitable for long-distance transportation and long-time construction concrete engineering.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a novel amphoteric ultra-slow-release polycarboxylate slump retainer and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the large-scale development of infrastructure construction, the demand for concrete continues to grow, and its application scope is becoming increasingly widespread. In some large-scale engineering projects, such as urban rail transit, high-rise buildings, and bridge construction, the transportation distance and time for concrete are constantly increasing. According to relevant statistics, in some large cities, the distance for transporting concrete from the mixing plant to the construction site can reach tens of kilometers, and it is not uncommon for the transportation time to exceed one hour. In addition, various factors during the construction process, such as waiting time for pouring and pumping time, also lead to an increase in the storage time of concrete before pouring. These factors make concrete more prone to slump loss during transportation and storage, thus affecting its workability.

[0003] The problem of concrete slump loss is becoming increasingly prominent in current construction projects, seriously affecting the workability of concrete and the quality of the project. Therefore, developing an ultra-long polycarboxylate slump retainer to effectively solve the problem of concrete slump loss is of significant practical importance and market demand. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a novel amphoteric ultra-slow-release polycarboxylate slump retainer, comprising the following steps: mixing and dissolving an unsaturated polyether macromonomer with water; adding a pH adjuster, a first portion of acrylic acid and an acrylic acid derivative; continuing stirring; then adding a first portion of a reducing agent and an initiator; simultaneously adding dropwise solution A and dropwise solution B; and continuing the reaction at a constant temperature after the addition is complete; the polycarboxylate slump retainer is obtained upon completion of the reaction. The initiator is a composite initiation system of peroxide initiators and azo initiators; The drop solution A is a mixed aqueous solution containing a second part of acrylic acid, unsaturated carboxylic acid esters and phosphate ester monomers, and the drop solution B is a mixed aqueous solution containing a second part of reducing agent and chain transfer agent.

[0005] In a further preferred embodiment, water is added after the reaction is complete to obtain a polycarboxylate slump retainer with a solid content of 50%.

[0006] Furthermore, the weight ratio of the peroxide initiator to the azo initiator is 1:1 to 2.

[0007] Furthermore, the weight ratio of the first portion of acrylic acid, the acrylic acid derivative, the second portion of acrylic acid, and the phosphate ester monomer is (0.3-0.7):(0.3-0.4):(1.0-1.2):1.

[0008] Furthermore, the acrylic acid derivative is one or a combination of several of sodium acrylate, sodium propylene sulfonate, and methacrylate monomers; The phosphate ester monomer is one or a combination of several of the following: polyphosphate ester, ethylene phosphate, propylene phosphate, 2-methacryloyloxyethyl phosphate choline, and 2-hydroxyethyl methacrylate phosphate.

[0009] Furthermore, the peroxide initiator is selected from one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, and benzoyl peroxide; The azo initiator is selected from one or more of the following: azobisisobutyrazoline hydrochloride, azobiscyanopentanoic acid, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobismethylpentanonitrile sulfonate.

[0010] Furthermore, the unsaturated polyether macromonomer is one or a combination of several of 4-hydroxybutylvinyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether, and vinyl butyl ether polyoxyethylene ether, and the molecular weight of the unsaturated polyether macromonomer is 1000 to 5000. The unsaturated carboxylic acid ester is one or a combination of several of the following: hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, ethyl acrylate, and unsaturated polyesters.

[0011] Furthermore, the chain transfer agent is one or a combination of several of the following: mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptoethanol, mercaptopropanol, and sodium hypophosphite. The reducing agent is one or a combination of several of the following: vitamin C, E51, ferrous sulfate heptahydrate, sodium hypophosphite, sodium metabisulfite, and L-ascorbic acid. The pH adjuster is one or a combination of sodium hydroxide, potassium hydroxide, and triethylamine.

[0012] Furthermore, by weight, the unsaturated polyether macromonomer comprises 200-250 parts, the total amount of acrylic acid comprises 7.5-15 parts, the acrylic acid derivative comprises 1.5-3.5 parts, the unsaturated carboxylic acid ester comprises 30-50 parts, the phosphate ester monomer comprises 2-10 parts, the chain transfer agent comprises 0.5-1.5 parts, the initiator comprises 1.5-3.0 parts, the total amount of reducing agent comprises 1.0-2.0 parts, and the pH adjuster comprises 1.5-3.0 parts; The total amount of acrylic acid includes the first portion of acrylic acid and the second portion of acrylic acid, and the total amount of reducing agent includes the first portion of reducing agent and the second portion of reducing agent.

[0013] Furthermore, the dropping time of the added solution A is 50-70 minutes, and the dropping time of the added solution B is 60-80 minutes; the heat preservation reaction time is 1-1.5 hours, and the dropping and heat preservation reaction processes are carried out at 25-45°C.

[0014] The present invention also provides a novel amphoteric ultra-slow-release polycarboxylate slump retainer, which is prepared by the preparation method described above.

[0015] Compared with the prior art, the preparation method of the novel amphoteric ultra-slow-release polycarboxylate slump retainer provided by the present invention has the following beneficial effects: This invention mixes the first part, acrylic acid and acrylic acid derivatives, with polyether macromonomers before initiation, allowing these functional groups to enter the chain growth process in the early stages of polymerization, which is beneficial for forming polymer segments with specific adsorption and dispersion functions. Furthermore, by independently adding dropwise solution A containing the second part, acrylic acid, unsaturated carboxylic acid esters, and phosphate ester monomers, the subsequent incorporation rate and sequence of different functional monomers can be controlled, thereby adjusting the distribution and ratio of hydrophilic groups, slow-release groups, and zwitterionic groups on the polymer chain, ultimately synthesizing a molecular structure with the expected "ultra-slow-release" performance. The composite initiation system composed of peroxide and azo initiators exhibits a synergistic effect. The peroxide initiator decomposes and initiates at lower temperatures, while the azo initiator continuously provides free radicals after the reaction system is heated. The combination of the two makes the entire polymerization process stable and complete, improving monomer conversion and reducing side reactions and unreacted monomer residues, thus obtaining a polycarboxylic acid slump retainer product with a more concentrated molecular weight distribution and more stable performance. The polycarboxylate slump retainer prepared by this invention can significantly improve the initial dispersibility and long-term slump retention capacity in concrete even at relatively low dosages. The preparation process of this invention is simple to operate; all reactions are carried out in the aqueous phase under mild conditions, requiring no complex equipment or harsh conditions. It has low energy consumption, is easy to scale up for industrial production, and can stably produce high-performance slump retainer products that meet the technical requirements of long-distance transportation and long-term pumping construction in modern concrete engineering. Furthermore, the production process does not involve harmful substances such as formaldehyde and ammonia, meeting green and environmentally friendly production requirements.

[0016] In the preferred embodiment, by strictly limiting the amounts of the first portion of acrylic acid, acrylic acid derivatives, the second portion of acrylic acid, and phosphate ester monomers to a specific ratio range, this ratio ensures the optimized arrangement and density of carboxyl groups, sulfonic acid groups, and phosphocholine amphoteric groups on the polymer backbone. The initial addition of the first portion of acrylic acid and its derivatives lays the foundation for strong adsorption and initial dispersion in the early stages of polymerization, while the dropwise addition of the second portion of acrylic acid and amphoteric phosphate monomers constructs molecular chain segments for sustained release and long-term stable dispersion. This specific ratio allows the adsorption-coordination effect of carboxyl groups, the strong electrostatic repulsion of sulfonic acid groups, and the environmentally adaptable hydrophilic effect of amphoteric phosphate groups to form a highly efficient complementarity in time and space, thereby unifying the contradiction between rapid onset and long-term maintenance at the molecular level. This achieves a synergistic effect of initial dispersion and ultra-long-term slump retention that cannot be achieved by traditional single-group slump retainers. Detailed Implementation

[0017] 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. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:1 ratio) were added dropwise. Then, the pre-prepared drop solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 65 min and 75 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0019] Example 2 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a ratio of 1:2) were added dropwise. Then, the pre-prepared drop solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 65 min and 75 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0020] Example 3 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 1.5 parts of acrylic acid, and 1.5 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a ratio of 1:2) were added dropwise. Then, the pre-prepared drop solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 65 min and 75 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0021] Example 4 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 2.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of an initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a ratio of 1:2) were added dropwise. Then, the pre-prepared drop solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 65 min and 75 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0022] Example 5 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 1.2 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a ratio of 1:2) were added dropwise. Then, the pre-prepared drop solution A (containing 5 parts of acrylic acid, 20 parts of hydroxyethyl acrylate, 10 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 65 min and 75 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0023] Example 6 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate. Continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of an initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:2 ratio). Then start adding the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 20 parts of hydroxyethyl acrylate, 10 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol). The dropping times for dropping solution A and dropping solution B are 65 minutes and 75 minutes, respectively. After the dropping is completed, continue the reaction for 1 to 1.5 hours. After the reaction is completed, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0024] Comparative Example 1 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution and 1.5 parts of acrylic acid, and continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 1.5 parts of hydrogen peroxide, and then start adding the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) at 50 minutes and 60 minutes respectively. After the addition is complete, continue the reaction for 1 to 1.5 hours. After the reaction is complete, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0025] Compared to Example 1, Comparative Example 1 did not use sodium propylene sulfonate and 2-methacryloyloxyethyl phosphocholine, but only one initiator, which was the basic process.

[0026] Comparative Example 2 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution and 1.5 parts of acrylic acid were added, and stirring was continued for 10 min. After adding 0.9 parts of 1% ferrous sulfate heptahydrate and 1.5 parts of hydrogen peroxide, the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 50 min and 60 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0027] Compared to Example 1, Comparative Example 2 did not use sodium propylene sulfonate and used only one initiator.

[0028] Comparative Example 3 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate. Continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 1.5 parts of hydrogen peroxide. Then start adding the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) at 50 minutes and 60 minutes respectively. After the addition is complete, continue the reaction for 1 to 1.5 hours. After the reaction is complete, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0029] Compared to Example 1, Comparative Example 3 used only one initiator.

[0030] Comparative Example 4 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate. Continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of an initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:1 ratio). Then start adding the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) at 50 minutes and 60 minutes respectively. After the addition is complete, continue the reaction for 1 to 1.5 hours. After the reaction is complete, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0031] Compared to Example 1, Comparative Example 4 did not contain 2-methacryloyloxyethyl phosphocholine.

[0032] Comparative Example 5 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water were added to a 1L four-necked flask and stirred until completely dissolved. Then, 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate were added, and stirring was continued for 10 min. Then, 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:1 ratio) were added dropwise. Then, the pre-prepared drop solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and drop solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol) were added dropwise at 50 min and 60 min, respectively. After the addition was completed, the reaction was continued for 1 to 1.5 h. After the reaction was completed, a certain amount of water was added to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0033] Compared with Example 1, Comparative Example 5 had a different dropping time.

[0034] Comparative Example 6 It is a commercially available common polycarboxylate slump retainer.

[0035] Comparative Example 7 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution, 3.5 parts of acrylic acid, and 2 parts of sodium propylene sulfonate. Continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of an initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:3 ratio). Then start adding the pre-prepared dropping solution A (containing 6 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 12 parts of hydroxypropyl acrylate, 5 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and dropping solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol). The dropping times for dropping solution A and dropping solution B are 65 minutes and 75 minutes, respectively. After the dropping is completed, continue the reaction for 1 to 1.5 hours. After the reaction is completed, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0036] Compared to Example 1, the weight ratio of peroxide initiator to azo initiator in Comparative Example 7 was 1:3.

[0037] Comparative Example 8 Add 215 parts of ethylene glycol monovinyl polyethylene glycol ether and some water to a 1L four-necked flask and stir until completely dissolved. Then add 1.7 parts of 32% sodium hydroxide solution, 5.5 parts of acrylic acid, and 4 parts of sodium propylene sulfonate. Continue stirring for 10 minutes. Add 0.9 parts of 1% ferrous sulfate heptahydrate and 2.5 parts of an initiator mixture (hydrogen peroxide and azobisisobutyronitrile in a 1:1 ratio). Then start adding pre-prepared dropwise solution A (containing 10 parts of acrylic acid, 24 parts of hydroxyethyl acrylate, 14 parts of hydroxypropyl acrylate, 12 parts of 2-methacryloyloxyethyl phosphocholine, and 10 parts of water) and dropwise solution B (containing 0.5 parts of L-ascorbic acid and 0.72 parts of mercaptoethanol). The dropwise addition times for dropwise solution A and dropwise solution B are 65 minutes and 75 minutes, respectively. After the addition is complete, continue the reaction for 1 to 1.5 hours. After the reaction is complete, add a certain amount of water to obtain a polycarboxylic acid slump-preserving solution with a solid content of 50%.

[0038] Performance testing To evaluate the slump retention properties of the ultra-slow-release polycarboxylate slump retainer of the present invention, the polycarboxylate slump retainers synthesized in Examples 1-6 and Comparative Examples 1-8 were subjected to concrete performance tests.

[0039] The method for determining concrete composition is as described in GB / 8076—2008 "Concrete Admixtures".

[0040] The cement used was Jin Yang P·042.5R cement; the crushed stone particle size was 5-25mm; the washed sand had a fineness modulus of 2.5; the manufactured sand contained 0.4% mud; the fly ash was grade II; and the mineral powder was S95. A concrete mixer was used for testing. The concrete mix proportion was: cement:washed sand:manufactured sand:crushed stone:fly ash:mineral powder:water = 170:150:650:1040:90:60:160. The concrete test results are shown in Table 1 below.

[0041] Table 1

[0042] As shown in Table 1, the slump retention rates of Examples 1-6 of the present invention were all above 93.5% after 3 hours, with Example 3 reaching as high as 97.8%. In contrast, the slump retention rates of the comparative examples (Comparative Examples 1, 3, and 4) lacking key components were all below 92.5% after 3 hours, while the commercially available product (Comparative Example 6) only reached 89.1%. This directly proves that the present invention effectively solves the problem of rapid loss of concrete workability over time by synergistically introducing sodium propylene sulfonate and 2-methacryloyloxyethyl phosphocholine amphoteric monomers, combined with a peroxide and azo compound initiation system.

[0043] As shown in the test results of Example 3 in Table 1, by adjusting the initial functional unit feeding ratio, the initial workability of the concrete can be fine-tuned while maintaining an excellent slump retention rate (97.8%). This provides a flexible and customizable technical solution for concrete projects that are adapted to different transportation distances, construction environments, or raw material characteristics.

[0044] In Table 1, the 3-hour spread retention rate of Example 1 was 94.1%, which was much higher than that of Comparative Example 1 (78.6%) and Comparative Example 6 (85.5%). This shows that the slump retainer of the present invention not only effectively inhibits slump loss, but also has a significant effect on maintaining the spread of concrete, indicating that it can maintain the rheological properties of concrete more comprehensively.

[0045] Comparative Example 7 adjusted the weight ratio of peroxide-based to azo initiators to 1:3, increasing the proportion of azo initiators. Its 3-hour slump retention was only 88.9%, and its 3-hour spread retention was 80.4%, significantly lower than Example 1 (slump retention 95.7%, spread retention 94.1%). This indicates that when the initiator ratio deviates from the preferred range of this invention (1:1-2), the synergistic effect of the composite initiation system weakens, the free radical generation sequence and concentration distribution become unbalanced, leading to an unstable polymerization process, decreased molecular chain structure uniformity, and consequently affecting the long-term dispersion stability of the slump retainer. This result confirms the importance of the composite initiator ratio in maintaining reaction controllability and product performance.

[0046] Comparative Example 8 significantly increased the feed amounts of acrylic acid, sodium propylene sulfonate, and phosphate monomers, resulting in higher initial slump and spread (240 mm and 625 mm, respectively). However, the slump retention rate dropped to 83.3% after 3 hours, and the spread retention rate was only 67.2%, indicating significantly inferior long-term slump retention performance compared to Example 1. This demonstrates that when the proportion of functional monomers exceeds the preferred range defined in this invention, the distribution of hydrophilic groups, sulfonic acid groups, and amphoteric phosphate groups on the polymer chain becomes unbalanced, leading to excessively rapid early adsorption and insufficient sustained-release capacity in the later stages, thus failing to achieve synergy between initial dispersion and ultra-long-term slump retention. This comparison further clarifies the crucial role of controlling the proportion of each functional monomer within a specific range in achieving "ultra-sustaining release" performance.

[0047] Although this document frequently uses terms such as unsaturated polyether macromonomers, acrylic acid, acrylic acid derivatives, unsaturated carboxylic acid esters, and phosphate ester monomers, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would be contrary to the spirit of this invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a novel amphoteric ultra-slow-release polycarboxylate slump retainer, characterized in that, Includes the following steps: Unsaturated polyether macromonomers are mixed and dissolved in water. A pH adjuster, acrylic acid and acrylic acid derivatives (part 1), and stirring are added. The mixture is stirred continuously. Then, a reducing agent (part 1) and an initiator are added, and dropwise additions A and B are added simultaneously. After the addition is complete, the reaction is kept at a constant temperature. The polycarboxylic acid slump stabilizer is obtained after the reaction is complete. The initiator is a composite initiation system of peroxide initiators and azo initiators; The drop solution A is a mixed aqueous solution containing a second part of acrylic acid, unsaturated carboxylic acid esters and phosphate ester monomers, and the drop solution B is a mixed aqueous solution containing a second part of reducing agent and chain transfer agent.

2. The preparation method according to claim 1, characterized in that: The weight ratio of the peroxide initiator to the azo initiator is 1:1 to 2.

3. The preparation method according to claim 1, characterized in that: The weight ratio of the first portion of acrylic acid, the acrylic acid derivative, the second portion of acrylic acid, and the phosphate ester monomer is (0.3-0.7):(0.3-0.4):(1.0-1.2):

1.

4. The preparation method according to claim 1, characterized in that: The acrylic acid derivative is one or a combination of several of sodium acrylate, sodium propylene sulfonate, and methacrylate monomers; The phosphate ester monomer is one or a combination of several of the following: polyphosphate ester, ethylene phosphate, propylene phosphate, 2-methacryloyloxyethyl phosphate choline, and 2-hydroxyethyl methacrylate phosphate.

5. The preparation method according to claim 1, characterized in that: The peroxide initiator is selected from one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, and benzoyl peroxide; The azo initiator is selected from one or more of the following: azobisisobutyrazoline hydrochloride, azobiscyanopentanoic acid, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobismethylpentanonitrile sulfonate.

6. The preparation method according to claim 1, characterized in that: The unsaturated polyether macromonomer is one or a combination of several of 4-hydroxybutylvinyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether, and vinyl butyl ether polyoxyethylene ether, and the molecular weight of the unsaturated polyether macromonomer is 1000 to 5000. The unsaturated carboxylic acid ester is one or a combination of several of the following: hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, ethyl acrylate, and unsaturated polyesters.

7. The preparation method according to claim 1, characterized in that: The chain transfer agent is one or a combination of several of the following: mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptoethanol, mercaptopropanol, and sodium hypophosphite. The reducing agent is one or a combination of several of the following: vitamin C, E51, ferrous sulfate heptahydrate, sodium hypophosphite, sodium metabisulfite, and L-ascorbic acid. The pH adjuster is one or a combination of sodium hydroxide, potassium hydroxide, and triethylamine.

8. The preparation method according to claim 1, characterized in that: By weight, the unsaturated polyether macromonomer comprises 200-250 parts, the total amount of acrylic acid comprises 7.5-15 parts, the acrylic acid derivative comprises 1.5-3.5 parts, the unsaturated carboxylic acid ester comprises 30-50 parts, the phosphate ester monomer comprises 2-10 parts, the chain transfer agent comprises 0.5-1.5 parts, the initiator comprises 1.5-3.0 parts, the total amount of reducing agent comprises 1.0-2.0 parts, and the pH adjuster comprises 1.5-3.0 parts; The total amount of acrylic acid includes the first portion of acrylic acid and the second portion of acrylic acid, and the total amount of reducing agent includes the first portion of reducing agent and the second portion of reducing agent.

9. The preparation method according to claim 1, characterized in that: The dropping time of the added solution A is 50-70 minutes, and the dropping time of the added solution B is 60-80 minutes; the heat preservation reaction time is 1-1.5 hours, and the dropping and heat preservation reaction processes are carried out at 25-45°C.

10. A novel amphoteric ultra-slow-release polycarboxylate slump retainer, characterized in that: It is prepared by any one of claims 1 to 9.

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