Preparation method of concrete anti-segregation agent

Abstract

The invention relates to the technical field of concrete admixtures, discloses a preparation method of a concrete anti-segregation agent, and aims to solve the problems of more side reactions, uncontrollable reaction process and disordered product molecular structures caused by unstable active functional group monomers in the existing water phase polymerization process. According to the core technical scheme, the method comprises the following steps: firstly, pretreating an anchoring functional group monomer and a pH-responsive shielding functional monomer in an aqueous medium to form a reversible shielding association body; and then, sequentially introducing the chain segment carrying the shielded anchoring functional group and the chain segment carrying the dispersed long side chain to the main chain of the polymer in stages by adopting a sequential dropwise addition polymerization process. The side reaction is effectively inhibited through the monomer pretreatment step, and the stability of the polymerization process is ensured; the accurate regulation and control of the microstructure of the polymer are realized through a sequential polymerization process, and the finally prepared anti-segregation agent shows excellent water retention anti-segregation performance and dispersing performance in concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, specifically to a method for preparing a concrete anti-segregation agent. Background Technology

[0002] Concrete, as the most crucial building material in modern engineering construction, is of paramount importance in terms of its workability, mechanical properties, and long-term durability. To improve the performance of fresh concrete, such as enhancing its fluidity and resistance to bleeding and segregation, chemical admixtures are typically added. Especially when preparing high-performance or self-compacting concrete, the high amount of cementitious materials and low water-cement ratio make the paste susceptible to segregation, severely impacting the homogeneity and final structural strength of the concrete.

[0003] To address this issue, existing technologies typically employ thickeners or anti-segregation agents to enhance the cohesiveness and water retention of cement paste. However, traditional thickeners often exhibit antagonistic effects when used in conjunction with high-efficiency water-reducing agents (such as polycarboxylate superplasticizers). The viscosity increase effect introduced by the thickener may weaken the dispersion effect of the water-reducing agent, leading to a loss of concrete fluidity, and vice versa. This approach, involving the physical compounding of multiple additives, not only increases the complexity of formulation design but also makes it difficult to guarantee stable and synergistic performance in the final product.

[0004] To overcome the limitations of physical compounding, the development of multifunctional polymers integrating multiple functions such as water reduction and dispersion, thickening and anti-segregation has become a current research direction. These polymers are typically synthesized by copolymerizing monomers with different functional groups. However, the preparation process of such multifunctional polymers itself faces significant technical bottlenecks. On the one hand, certain functional monomers used to achieve strong anchoring of cement particles (such as monomers containing silane groups) are chemically extremely unstable in the aqueous free radical polymerization reaction environment, easily undergoing side reactions such as hydrolysis or self-condensation, forming insoluble substances, and even causing the entire reaction system to gel. This makes it difficult to effectively and completely introduce the target functional groups into the polymer molecular chain, leading to unstable product performance or even preparation failure.

[0005] On the other hand, even if the monomer stability issue is resolved, conventional one-pot copolymerization processes, which mix all monomers in a single reaction, typically only yield random copolymers with randomly distributed functional groups. In this disordered molecular structure, the effects of different functional groups may interfere with each other. For example, large, dispersed side chains may sterically obstruct anchoring groups, hindering their effective bonding with cement particles. This structural disorder limits the synergistic effect of the functional groups, causing the overall performance of the polymer to fall far short of its theoretical optimal level. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a concrete anti-segregation agent, aiming to solve the technical problems of poor reaction stability, disordered product structure, and uncontrollable performance when combining multiple chemical monomers with different functions, especially active monomers that are unstable in aqueous solutions, into the same polymer molecular chain through copolymerization.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a concrete anti-segregation agent, comprising synthesizing a multifunctional polymer with ordered molecular structure in an aqueous medium through specific monomer pretreatment technology and sequential polymerization process. The method includes the following steps:

[0009] First, a monomer pretreatment step is performed. Anchored functional group monomers and pH-responsive shielding functional monomers are mixed in an aqueous medium. In this step, specific functional groups on the pH-responsive shielding functional monomers and active groups on the anchored functional group monomers form intermolecular shielding associations. The formation of these shielding associations improves the chemical stability of the active groups on the anchored functional group monomers in the subsequent weakly acidic polymerization environment, inhibiting premature hydrolysis or self-condensation side reactions, thereby ensuring the smooth progress of the polymerization reaction.

[0010] Next, the polymerization solution is prepared. The shielding associative polymer formed above is mixed with the first part of the flexible viscous main chain monomer to form dropwise solution I. Simultaneously, the rigidly dispersed long-side-chain macromonomer is mixed with the remaining second part of the flexible viscous main chain monomer to form dropwise solution II. The flexible viscous main chain monomer is added stepwise to control the monomer concentration at different polymerization stages.

[0011] Then, the sequential polymerization step is performed. Under the action of the initiator, the temperature and pH of the reaction system are controlled within a preset range. First, dropwise solution I is continuously added to the reaction system to carry out the first stage of polymerization. This stage aims to preferentially introduce segments carrying shielded anchored functional groups into the polymer backbone. After the first stage of polymerization is completed, without interruption, dropwise solution II is immediately and continuously added to the same reaction system to carry out the second stage of polymerization. Because rigid dispersed long-side-chain macromonomers have large molecular volumes and steric hindrance, introducing them in the later stages of the polymerization reaction helps to improve their grafting efficiency and facilitates the formation of an ordered molecular conformation with anchored groups near the backbone and dispersed groups far from the backbone. After the second stage of polymerization is completed, the polymer product is obtained.

[0012] Finally, a post-processing step is performed. The obtained polymer product is subjected to a post-curing reaction to ensure the conversion rate of each monomer. After post-curing, magnesium sulfate, an auxiliary component, is added to the polymer product and mixed thoroughly to obtain the final concrete anti-segregation agent.

[0013] In one specific embodiment of the present invention:

[0014] The anchoring functional group monomer is vinyltrimethoxysilane or vinyltriethoxysilane. The flexible tackifying main chain monomer is acrylamide. The rigid dispersing long side chain macromonomer is isopentenyl polyoxyethylene ether. The pH-responsive shielding functional monomer is N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid.

[0015] In another specific embodiment of the present invention, the weight parts of the raw materials are as follows: 1-5 parts of anchoring functional group monomer; 20-30 parts of flexible thickening main chain monomer; 60-75 parts of rigid dispersion long side chain macromonomer; and 1-4 parts of pH responsive shielding functional monomer.

[0016] The monomer pretreatment step is carried out at room temperature with a mixing time of 15-20 minutes. The polymerization reaction is initiated by a redox initiator system. In the first and second stage polymerization reactions, the pH of the reaction system is maintained at 5.0-6.0, and the reaction temperature is maintained at 85-92℃. The post-maturation reaction is carried out at a temperature of 90-95℃ for 50-70 minutes.

[0017] This invention provides a method for preparing a concrete anti-segregation agent. It has the following beneficial effects:

[0018] 1. This invention significantly improves the stability and controllability of the entire preparation method by pretreating the anchoring functional group monomer and the pH-responsive shielding functional monomer before the polymerization reaction. This pretreatment step causes the active groups that are unstable in the aqueous medium to form intermolecular shielding associations, effectively suppressing side reactions such as hydrolysis and self-condensation in the subsequent weakly acidic polymerization environment. This avoids process problems such as gelation of the reaction system and ensures that the key functional groups can be successfully and completely introduced into the polymer molecular chain.

[0019] 2. The sequential dropwise polymerization process employed in this invention enables effective control over the microstructure of the final polymer product. By introducing monomers with different functions and molecular volumes into the reaction system in stages and sequentially—that is, first constructing a main chain rich in anchoring groups, and then grafting large-volume dispersed long side chains—it helps to form polymer molecules with well-defined functional partitions and a regular, ordered structure, rather than random copolymers produced by traditional copolymerization methods. This ordered molecular conformation provides a structural basis for the stable performance of the final product.

[0020] 3. The method provided by this invention combines the above-mentioned monomer shielding technology with sequential polymerization process to successfully integrate three different functions for interface anchoring, slurry thickening and particle dispersion into a single polymer structure through stable covalent bonds. This fundamentally solves the problems of poor compatibility, performance antagonism and unstable effect caused by physical blending of multiple additives in the prior art, and provides a complete and efficient technical approach for preparing multifunctional concrete admixtures with synergistic performance enhancement. Detailed Implementation

[0021] 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, and 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.

[0022] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0023] Vinyltrimethoxysilane, CAS No.: 2768-02-7;

[0024] 2-Acrylamide-2-methylpropanesulfonic acid, CAS No.: 15214-89-8;

[0025] Acrylamide, CAS No.: 79-06-1;

[0026] Isoprene polyoxyethylene ether, CAS No.: 62601-60-9;

[0027] Ammonium persulfate, CAS No.: 7727-54-0;

[0028] Sodium bisulfite, CAS No.: 7631-90-5;

[0029] Citric acid, CAS No.: 77-92-9;

[0030] Magnesium sulfate, CAS No.: 10034-99-8.

[0031] Examples 1-3:

[0032] Example 1:

[0033] A method for preparing a concrete anti-segregation agent, the specific steps of which are as follows:

[0034] S1. In a beaker, take 150g of deionized water, add 1.0g of N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid (AMPS), stir to dissolve, then add 1.0g of vinyltrimethoxysilane (VTMS), and stir continuously at room temperature for 15 minutes to form a shielding associative compound.

[0035] S2. Add 8.0 g of acrylamide (AM, 40% of the total amount) to the solution obtained in S1 above, and stir until completely dissolved to obtain dropwise solution I.

[0036] S3. In another beaker, dissolve 60.0 g of isopentenyl polyoxyethylene ether (IPEG) and 12.0 g of acrylamide (AM, 60% of the total amount) in 200 g of deionized water and stir until homogeneous to obtain dropwise solution II.

[0037] S4. In a four-necked flask equipped with a stirrer, condenser, and thermometer, add 300g of deionized water, purge with nitrogen for 30 minutes, and then heat to 85°C. Adjust the pH of the system to 5.0 using citric acid. Then, simultaneously and uniformly add solution I, 5% ammonium persulfate (APS) solution, and 10% sodium bisulfite (SBS) solution. Complete the addition of solution I within 50 minutes, maintaining the reaction temperature at 85°C by adjusting the initiator dropping rate.

[0038] S5. After the addition of solution I is complete, immediately begin the uniform addition of solution II, while continuing the addition of the initiator. Complete the addition of solution II within 80 minutes, and maintain the reaction temperature at 85°C.

[0039] S6. After all additions are complete, maintain the reaction system at 90°C for 50 minutes. Cool to below 50°C, add 1.0g of magnesium sulfate pre-dissolved in a small amount of water, and stir until homogeneous to obtain the product.

[0040] Example 2:

[0041] A method for preparing a concrete anti-segregation agent, the raw material dosage and process parameters are basically the same as in Example 1, the difference being:

[0042] The raw materials used are: vinyltrimethoxysilane 3.0g, acrylamide 25.0g, isopentenyl polyoxyethylene ether 68.0g, N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid 2.5g, and magnesium sulfate 2.0g.

[0043] The process parameters are as follows: the polymerization reaction pH is 5.5, the reaction temperature is maintained at 88℃, and the post-curing reaction is held at 92℃ for 60 minutes.

[0044] The remaining steps are the same as in Example 1, and the product is obtained.

[0045] Example 3:

[0046] A method for preparing a concrete anti-segregation agent, the raw material dosage and process parameters are basically the same as in Example 1, the difference being:

[0047] The raw materials used are: vinyltrimethoxysilane 5.0g, acrylamide 30.0g, isopentenyl polyoxyethylene ether 75.0g, N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid 4.0g, and magnesium sulfate 3.0g.

[0048] The process parameters are as follows: the polymerization reaction pH is 6.0, the reaction temperature is maintained at 92℃, and the post-curing reaction is held at 95℃ for 70 minutes.

[0049] The remaining steps are the same as in Example 1, and the product is obtained.

[0050] Comparative Examples 1-2:

[0051] Comparative Example 1:

[0052] Compared with Example 2, the difference is that this comparative example uses the traditional one-pot copolymerization method, that is, all monomers, including vinyltrimethoxysilane, acrylamide, isopentenyl polyoxyethylene ether and N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid, are added to the reactor at one time for polymerization, instead of using the sequential drop-addition polymerization process of the present invention. All other preparation conditions are the same.

[0053] Comparative Example 2:

[0054] Compared with Example 2, the difference is that the pretreatment process of step S1 was omitted in this comparative example. That is, vinyltrimethoxysilane was not pre-screened and associated with N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid, but was directly mixed with other monomers and then subjected to sequential drop-add polymerization. The remaining preparation steps and conditions are the same.

[0055] Test Example 1: Cement Paste Flowability and Bleeding Rate Test

[0056] This test case aims to evaluate the effects of antisegregation agents prepared by different methods on the workability of cement paste, specifically its dispersion and water retention properties.

[0057] Experimental Materials and Equipment: Cement: P.O42.5 ordinary Portland cement. Experimental Water: Deionized water. Equipment: Cement paste mixer, truncated cone mold (height 60mm, upper diameter 36mm, lower diameter 60mm), glass plate, 100mL graduated cylinder, stopwatch.

[0058] Sample preparation:

[0059] The liquid products obtained in Examples 1-3 and Comparative Examples 1-2 were all precisely diluted with deionized water to a solid content of 20.0% and used as samples for testing.

[0060] Experimental steps:

[0061] a) Weigh 300g of cement. Based on a water-cement ratio of 0.29, the required total water is 87g. Assuming the admixture dosage is 1.0% of the cement mass (based on solids content), the required admixture solids content is 3.0g, which translates to 15.0g for a sample with 20.0% solids content. Therefore, the actual amount of mixing water added is 87g - 15.0g = 72.0g.

[0062] b) Add 72.0g of mixing water and 15.0g of the sample to be tested to the cement paste mixing pot, start the mixer, and add 300g of cement evenly into the pot within 30 seconds.

[0063] c) Immediately start the mixing program: Mix slowly for 120 seconds, stop for 15 seconds. Then, mix rapidly for 120 seconds to complete the slurry preparation.

[0064] d) Flowability Test: Place the truncated cone mold in the center of a clean glass plate and moisten the inner wall of the mold with a damp cloth. Fill the mold with the mixed cement paste in one go and level it. Lift the mold vertically upwards. After the paste stops flowing, use a steel ruler to measure the diameter of the spread body in two mutually perpendicular directions, and take the average value as the initial flowability.

[0065] e) Bleeding Rate Test: Quickly fill a 100mL graduated cylinder with the fluidity test fluidized bed paste to the 100mL mark, and seal the cylinder to prevent water evaporation. Place the graduated cylinder on a stable, vibration-free surface and let it stand for 2 hours. Record the volume of water separated from the surface of the paste. The bleeding rate is calculated using the following formula: Bleeding Rate (%) = (Bleeding Volume / Total Water Content in the Paste) × 100%

[0066] Experimental data:

[0067] Table 1: Test Results of Cement Paste Performance of Each Sample

[0068] Test sample Initial flowability (mm) 2-hour water excretion rate (%) Example 1 278 0.15 Example 2 286 0 Example 3 281 0.05 Comparative Example 1 225 3.8 Comparative Example 2 190 7.5

[0069] In summary, the test results in Table 1 show that the products of Examples 1, 2, and 3 obtained using the preparation method provided by this invention all exhibit extremely low bleeding rates while achieving high fluidity in cement paste. This indicates that the polymer products prepared by the method of this invention successfully combine rigid dispersive long side chains that provide electrostatic repulsion and steric hindrance, with flexible thickening main chains that can adsorb and bind free water. The synergistic effect of these two functions achieves efficient dispersion and water retention and anti-segregation effects in cement paste.

[0070] Example 2 was compared with Comparative Example 1, both using the same raw material ratios, but Comparative Example 1 employed a traditional one-pot polymerization method. The results showed that the slurry fluidity of the product from Comparative Example 1 was significantly reduced, while the bleeding rate increased substantially. This is because the sequential dropwise polymerization process employed in this invention, by introducing different monomers in stages, regulates the polymerization process, which is beneficial for forming an ordered molecular structure where rigid dispersed side chains are effectively grafted onto the flexible main chain. In contrast, one-pot polymerization leads to random copolymerization of the monomers, resulting in a disordered molecular structure. The steric hindrance effect and the random distribution of functional groups limit the effective realization of its properties.

[0071] Example 2 was compared with Comparative Example 2, both of which used sequential polymerization, but Comparative Example 2 omitted the pretreatment step for anchoring functional group monomers. The results showed that the product of Comparative Example 2 exhibited severely degraded properties, with the lowest flowability and the highest bleeding rate. This directly confirms the crucial role of the pretreatment step. The shielding associative complex formed through pretreatment protects the chemical stability of the anchoring functional group monomers during aqueous polymerization, ensuring their effective introduction into the polymer chain. Without this step, unstable anchoring functional groups undergo side reactions, leading to serious defects in the molecular structure of the final product and failing to achieve the expected technical effects.

[0072] Test Example 2: Concrete Setting Time and Compressive Strength Test

[0073] This test case aims to evaluate the impact of antisegregation agents prepared by different methods on the macroscopic engineering properties of concrete, specifically setting characteristics and mechanical strength development.

[0074] Experimental materials and equipment:

[0075] Cement: P.O42.5 ordinary Portland cement.

[0076] Fine aggregate: medium sand.

[0077] Coarse aggregate: 5-20mm continuously graded crushed stone.

[0078] Equipment: Horizontal shaft concrete mixer, concrete permeability tester (for determining setting time), standard cube mold (100mm×100mm×100mm), pressure testing machine, standard curing room.

[0079] Sample preparation: The liquid products obtained in Examples 1-3 and Comparative Examples 1-2 were all precisely diluted with deionized water to a solid content of 20.0% and used as samples to be tested.

[0080] Experimental steps:

[0081] Concrete mix proportion (unit: kg / m³) 3Components: Cement 450, Sand 650, Aggregate 1100, Water 165. The admixture dosage is 1.0% of the cement mass (based on solid content), that is, 4.5 kg of admixture solid content is added per cubic meter of concrete. This translates to 22.5 kg of sample to be tested with a solid content of 20.0%.

[0082] Add the weighed sand, gravel, and half of the water to the mixer and mix for 30 seconds. Add the cement and mix for 30 seconds. Finally, add the remaining water and the sample to be tested, and continue mixing for 120 seconds to complete the preparation of the concrete mixture.

[0083] Setting time test: According to GB / T50080-2016 standard, the mixed concrete was sieved, and the mortar portion was taken for penetration resistance test to determine the initial setting time (penetration resistance reaches 3.5MPa) and final setting time (penetration resistance reaches 28MPa).

[0084] Compressive strength test: The mixed concrete was poured into standard cubic molds and vibrated to form the required shape. After curing in a standard curing room (temperature 20±2℃, relative humidity ≥95%) for 24 hours, the molds were removed, and curing continued under standard conditions until the specified age. The compressive strength of the test blocks was tested at 3 days, 7 days, and 28 days, according to GB / T50081-2019 standard.

[0085] Experimental data:

[0086] Table 2: Test Results of Concrete Performance for Each Sample

[0087]

[0088] Summary: The data in Table 2 show that the concrete specimens prepared using the method of this invention (Examples 1-3) exhibited normal setting times and fully developed compressive strength at each age. This indicates that the polymer products successfully prepared by this method possess anchoring functional groups that effectively act on the surface of cement particles, while the dispersed long side chains provide excellent dispersibility through steric hindrance. Together, these factors contribute to the formation of a dense microstructure in the hardened cement paste, thereby endowing the concrete components with high mechanical strength.

[0089] Comparing the results of Example 2 with those of Comparative Example 1, under the condition of completely identical raw materials, the concrete strength of the product prepared by the one-pot method in Comparative Example 1 was significantly lower than that in Example 2, and the setting time was prolonged. This indicates that the sequential polymerization process used in this invention is necessary for constructing polymer structures with clearly defined functional zones. The ordered structure obtained by this process can achieve efficient synergy among various functional groups, while the random copolymer structure of Comparative Example 1 is disordered and cannot function effectively, thus leading to a decline in the overall performance of the concrete.

[0090] Comparing the results of Example 2 with those of Comparative Example 2, the latter, lacking a crucial monomer pretreatment step, resulted in a significant decrease in concrete strength and a severely prolonged setting time. This phenomenon confirms that pretreatment of anchoring functional group monomers is a prerequisite for the formation of the target polymer. Without this step, unstable reactive monomers undergo side reactions during polymerization, leading to serious defects in the molecular structure of the final polymer. Furthermore, the byproducts negatively impact the cement hydration process, ultimately resulting in severe deterioration of the concrete's mechanical properties.

[0091] Test Example 3: Concrete Water Reduction Rate Test

[0092] This test case aims to evaluate the efficiency of antisegregation agents prepared by different methods as water-reducing agents, that is, their ability to reduce mixing water while achieving the same concrete workability.

[0093] Experimental materials and equipment:

[0094] Cement: P.O42.5 ordinary Portland cement.

[0095] Fine aggregate: medium sand.

[0096] Coarse aggregate: 5-20mm continuously graded crushed stone.

[0097] Equipment: Horizontal shaft concrete mixer, slump cone, measuring scale.

[0098] Sample preparation:

[0099] The liquid products obtained in Example 2, Comparative Example 1, and Comparative Example 2 were all precisely diluted with deionized water to a solid content of 20.0% and used as test samples for later use.

[0100] Experimental steps:

[0101] Reference concrete preparation: The same concrete mix proportion as in Test Example 2 was used (cement 450, sand 650, aggregate 1100, unit kg / m³). 3 Adjust the mixing water volume until the slump is measured to be 180±10mm. Record the unit water consumption at this point as the baseline water consumption (W0).

[0102] Test concrete preparation: Keeping the cement, sand and aggregate content of the reference concrete unchanged, the test samples were added at a rate of 0.8%, 1.0% and 1.2% (solid content) of cement mass, respectively.

[0103] Water reduction rate determination: For each admixture of the test sample, the mixing water volume was adjusted through repeated experiments until the slump of the concrete group reached 180±10mm. The unit water consumption (W1) at this time was recorded.

[0104] Water reduction rate calculation: The water reduction rate of each sample is calculated according to the following formula: Water reduction rate (%) = (W0 - W1) / W0

[0105] ×100%

[0106] Experimental data:

[0107] Table 3: Water Reduction Rate Test Results of Each Sample at Different Additive Doses

[0108]

[0109]

[0110] Summary: The data in Table 3 objectively reflect the water-reducing performance of the product prepared by the method of this invention. The product of Example 2 showed high water reduction rates at different dosages, proving that the polymer prepared by the method of this invention has rigid dispersed long side chains in its molecular structure that can effectively adsorb onto the surface of cement particles and generate a steric hindrance effect, thereby destroying the flocculation structure of cement particles, releasing encapsulated water, and achieving a significant water-reducing effect.

[0111] Comparing the test data of Example 2 and Comparative Example 1, the water reduction rate of the product in Example 2 was significantly higher than that in Comparative Example 1 at all dosage levels. This result indicates that the sequential dropwise polymerization process used in this invention is a necessary technical means to obtain high-performance products. By controlling the polymerization process, this process facilitates the formation of an ordered molecular structure with anchoring groups near the main chain and dispersed groups far from the main chain, maximizing the functionality of the dispersed groups. In contrast, the one-pot random copolymerization used in Comparative Example 1 resulted in a disordered product structure, with some functional groups being embedded or interfering with each other, failing to efficiently exert their dispersing effect, thus leading to lower water reduction efficiency.

[0112] Comparing the test data of Example 2 and Comparative Example 2, the water reduction rate of the product of Comparative Example 2 is extremely low, almost devoid of application value as a water-reducing agent. This decisively proves the indispensability of the monomer pretreatment step. Without this step, unstable anchored functional group monomers undergo side reactions such as hydrolysis during polymerization, resulting in the failure to form the target molecular structure. The final product molecular chain has structural defects and cannot be effectively anchored to the surface of cement particles, naturally failing to achieve the technical objectives of dispersing particles and reducing water consumption. This, in turn, confirms the scientific nature and completeness of the method design of this invention.

[0113] Test Example 4: Polymer Solution Stability Test

[0114] This test case aims to evaluate the stability of anti-segregation agent stock solutions prepared by different methods under storage conditions. This stability indirectly reflects the integrity of the polymer molecular structure and the reliability of the preparation method.

[0115] Experimental materials and equipment:

[0116] Samples to be tested: Undiluted polymer stock solutions prepared in Example 2, Comparative Example 1 and Comparative Example 2.

[0117] Equipment: sealed glass bottle, constant temperature chamber, rotational viscometer.

[0118] Experimental steps:

[0119] Samples of the newly prepared polymer stock solutions of Example 2, Comparative Example 1 and Comparative Example 2 were taken, their initial appearance was recorded, and their initial viscosity was tested using a rotational viscometer at 25°C.

[0120] The above samples were placed into sealed glass bottles and stored in a constant temperature chamber at 50°C for accelerated aging.

[0121] After 30 days of storage, remove the samples and allow them to return to room temperature. First, observe and record the appearance of each sample, checking for phenomena such as layering, precipitation, or gelation.

[0122] At 25°C, the final viscosity of each sample after storage was tested again using a rotational viscometer.

[0123] The viscosity change rate of each sample during storage was calculated using the following formula: Viscosity change rate (%) = |(Final viscosity - Initial viscosity) / Initial viscosity| × 100%

[0124] Experimental data:

[0125] Table 4: Results of polymer solution stability test

[0126]

[0127]

[0128] Summary: The test results in Table 4 show that the product of Example 2 prepared by the method of the present invention did not exhibit significant changes in its macroscopic state and viscosity after accelerated aging storage, demonstrating high storage stability. This indicates that the preparation method of the present invention, through the synergistic effect of each step, successfully synthesized a structurally complete and chemically stable polymer. The various functional groups on the molecular chain are connected by stable covalent bonds, enabling them to maintain their designed molecular conformation in a solution environment for a long time without dissociation or secondary reactions.

[0129] Comparing Example 2 with Comparative Example 1, the product of Comparative Example 1 exhibited turbidity, precipitation, and a significant increase in viscosity after storage, indicating poor stability. This is attributed to its one-pot random copolymerization process. This process cannot control the chain structure, and unreacted functional groups may exist between the random copolymer molecular chains. These functional groups will slowly undergo secondary reactions such as cross-linking during long-term storage, leading to increased system viscosity and ultimately the formation of insoluble substances. This comparative result highlights the necessity of the sequential dropwise polymerization process used in this invention for constructing stable molecular structures.

[0130] Comparing Example 2 with Comparative Example 2, the product of Comparative Example 2 exhibited extremely poor stability, being heterogeneous from the initial state and undergoing severe stratification and precipitation after storage, with drastic changes in viscosity. This phenomenon decisively demonstrates the crucial role of the pretreatment step for anchoring functional group monomers. Without this step, unstable active groups undergo side reactions such as hydrolysis and self-condensation during the polymerization stage, resulting in a final product that is a mixture of the target polymer and a large number of insoluble byproducts (such as siloxane oligomers). This mixture is extremely unstable and rapidly undergoes phase separation during storage, fundamentally confirming that monomer pretreatment is a prerequisite for obtaining stable and effective products.

[0131] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a concrete anti-segregation agent, characterized in that, Includes the following steps: S1. Pre-treat the anchoring functional group monomer and the pH-responsive shielding functional monomer in an aqueous medium to form a shielding assemblage. S2. Mix the shielding associative body with the first part of the flexible adhesive main chain monomer to form a dropwise solution I; S3. Mix the rigidly dispersed long-side-chain macromonomer with the second part of the flexible thickening main chain monomer to form dropwise solution II; S4. Under the action of the initiator, the dropwise solution I is first added dropwise to the reaction system to carry out the first stage of polymerization; S5. Subsequently, the solution II is added dropwise to the reaction system to carry out the second stage of polymerization, and the polymer product is obtained. S6. Add magnesium sulfate, an auxiliary component, to the polymer product to obtain the concrete anti-segregation agent.

2. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, The anchoring functional group monomer is vinyltrimethoxysilane or vinyltriethoxysilane, the flexible tackifying main chain monomer is acrylamide, the rigid dispersing long side chain macromonomer is isopentenyl polyoxyethylene ether, and the pH-responsive shielding functional monomer is N,N-dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid.

3. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, The raw materials used in the preparation method, by weight, are as follows: Vinyltrimethoxysilane or vinyltriethoxysilane: 1-5 parts; Acrylamide: 20-30 parts; Isoprene polyoxyethylene ether: 60-75 parts; N,N-Dimethylacrylamide-2-acrylamide-2-methylpropanesulfonic acid: 1-4 parts.

4. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, In step S1, the pretreatment involves mixing the anchoring functional group monomer and the pH-responsive shielding functional monomer at room temperature for 15-20 minutes.

5. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, In steps S4 and S5, the polymerization reaction is carried out in a redox initiator system.

6. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, In steps S4 and S5, the polymerization reaction is carried out under conditions of pH 5.0-6.

0.

7. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, In steps S4 and S5, the polymerization reaction temperature is maintained at 85-92°C.

8. The method for preparing a concrete anti-segregation agent according to claim 1, characterized in that, After step S5 and before step S6, the polymer product is subjected to a post-maturation reaction.

9. The method for preparing a concrete anti-segregation agent according to claim 8, characterized in that, The post-curing reaction is carried out at a temperature of 90-95℃ for 50-70 minutes.

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