Sequence segmentation type long-chain and short-chain block polycarboxylic acid water reducer and preparation method thereof
By designing a sequence-segmented long-short chain block polycarboxylate superplasticizer, the short-chain polyether side chains distributed in segments on the main chain work synergistically with the anti-intercalation cap structure, solving the problem of unstable performance of polycarboxylate superplasticizer in mud-containing systems and achieving efficient and stable water reduction and slump retention effects.
Patent Information
- Application Number
- CN202512045692.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-06
AI Technical Summary
Existing polycarboxylate superplasticizers are difficult to achieve simultaneously high water reduction rate, excellent slump retention and dosage stability in mud-containing systems. Traditional modification methods have failed to effectively inhibit the intercalation adsorption of polyether side chains by clay minerals, resulting in unstable performance.
A sequence segmented long and short chain block polycarboxylate superplasticizer is designed, with the main chain containing anti-mud functional segment A and stabilizing and slump-preserving segment B. Anti-mud functional segment A is enriched with short chain polyether side chains and connected to anti-intercalation cap structure and weak charge end groups at the end, achieving synergistic effect through segmented or gradient distribution.
Under complex muddy conditions, it achieves high utilization rate, low admixture sensitivity and stable construction performance, effectively inhibits the adsorption of side chains by clay minerals, and maintains good fluidity and slump retention performance.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete admixture technology, specifically to a sequence segmented long and short chain block polycarboxylate superplasticizer and its preparation method. Background Technology
[0002] Polycarboxylate superplasticizers, as third-generation high-performance concrete admixtures, typically consist of a polymer backbone containing carboxyl groups (-COO-) and grafted polyether (such as polyethylene oxide, PEO) side chains. Their mechanism of action relies primarily on the electrostatic adsorption of the carboxyl groups on the backbone onto the surface of cement particles, while the hydrophilic polyether side chains extend in solution, generating a strong steric hindrance effect. This effectively disperses cement particles, significantly improving the flowability and workability of the concrete mixture. Compared to first-generation lignin-based and second-generation naphthalene-based superplasticizers, polycarboxylate superplasticizers offer significant advantages such as high water reduction rate, low dosage, highly designable molecular structure, and good environmental performance, making them an indispensable core material in modern commercial concrete, high-performance concrete, and precast components.
[0003] To address the challenges posed by diverse cement types, complex mineral admixtures, varying environmental temperature and humidity, and diverse construction process requirements in engineering practice, existing technologies have optimized the molecular structure of polycarboxylate superplasticizers in various ways. Common modification strategies include: adjusting the length of polyether side chains to balance initial dispersibility and slump retention; altering the density of carboxyl groups on the main chain to regulate adsorption strength and charge density; and using polyether macromonomers of different lengths for physical compounding or preparing random copolymers through copolymerization to achieve wider application adaptability. Furthermore, some studies have explored the introduction of special functional groups such as phosphate groups, sulfonic acid groups, and amide groups, or attempted to construct branched or comb-like topologies, aiming to improve the compatibility and adaptability of superplasticizers to complex cementitious material systems.
[0004] However, in actual construction, especially when using aggregates with high mud content or mixing water rich in clay minerals (such as montmorillonite and kaolin), the performance of traditional polycarboxylate superplasticizers often fluctuates significantly or even fails severely. Studies have shown that layered silicate clay minerals such as montmorillonite, due to their large specific surface area and strong cation exchange capacity, have an extremely strong adsorption affinity for polycarboxylate superplasticizer molecules, particularly their polyoxyethylene side chains. The side chains of the superplasticizer molecules readily insert into the interlayer structure of the clay or undergo strong adsorption on its surface, resulting in a large amount of effective components being "ineffectively consumed" by the clay particles rather than acting on the target cement particles. The macroscopic manifestations are: a significant decrease in the initial water reduction rate of concrete, accelerated loss of fluidity of the mixture over time, and a sharp increase in the sensitivity of the admixture dosage required to maintain workability. This problem is particularly prominent in superplasticizers using long-chain polyether side chains (providing stronger steric hindrance), as long chains are more prone to intercalation adsorption.
[0005] To address the negative impacts of clay minerals, existing technologies typically employ the following measures: first, universally shortening the side chain length of polyethers to reduce the probability of interaction between them and the clay layer; second, simply increasing the dosage of water-reducing agents to compensate for losses due to clay adsorption; and third, physically compounding polycarboxylate water-reducing agent products with different side chain lengths, or synthesizing random copolymers of long and short chains. However, these methods all have significant drawbacks: excessively shortening the side chains weakens the steric hindrance effect, potentially leading to re-flocculation of the concrete paste in the later stages of mixing, resulting in insufficient slump retention; simply increasing the dosage not only increases costs but may also introduce new problems such as excessive retardation and bleeding; while simple compounding or random copolymerization, due to the lack of careful sequence design and functional partitioning in the molecular structure, results in chaotic competitive adsorption behavior of different chain segments on the clay and cement surfaces, failing to fundamentally inhibit the non-selective, high-loss adsorption of polyether side chains on the clay surface, leading to limited and unstable anti-mud effects.
[0006] In summary, existing technologies for the anti-mud modification of polycarboxylate superplasticizers mainly focus on macroscopic adjustment of overall molecular parameters (such as average side chain length and total carboxyl group density) or rely on empirical compounding schemes. These methods fail to address the root cause of molecular structure design and construct novel molecular architectures with clear functional partitions and synergistic mechanisms targeting the intercalation and adsorption mechanisms of clay minerals.
[0007] Therefore, existing polycarboxylate superplasticizers cannot simultaneously achieve a balance of high water reduction rate, excellent slump retention, and dosage stability in mud-containing systems. Developing a novel polycarboxylate superplasticizer that can be precisely designed at the molecular sequence level, effectively resist clay adsorption, ensure that the active ingredients act efficiently on cement particles, and thus maintain stable performance under complex mud-containing conditions has become a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0008] Therefore, it is necessary to provide a sequence-segmented long and short chain block polycarboxylate superplasticizer and its preparation method, in order to solve the problems existing in the prior art.
[0009] To achieve the above objectives, the present invention provides a technical solution:
[0010] A sequence-segmented long-short chain block polycarboxylate superplasticizer, characterized in that the superplasticizer is a comb-shaped copolymer, wherein the main chain of the comb-shaped copolymer is a carboxyl-containing vinyl polymer backbone, the side chains of the comb-shaped copolymer include polyether side chains, and the molecular structure of the comb-shaped copolymer contains at least two segments with different structures and functions along the main chain direction:
[0011] Anti-mud functional segment A, wherein anti-mud functional segment A is enriched with short-chain polyether side chains, the number of polyoxyethylene repeating units in the short-chain polyether side chains is 3-20, and the ends of the short-chain polyether side chains are connected to anti-intercalation end cap structures; and
[0012] Stabilizing and slump-preserving segment B, wherein the stabilizing and slump-preserving segment B is enriched with long-chain polyether side chains, and the number of polyoxyethylene repeating units of the long-chain polyether side chains is 30-120;
[0013] The anti-mud functional segment A and the stabilizing and collapsible segment B are distributed in a segmented or gradient manner on the main chain, and the anti-intercalation end cap structure mainly or only exists at the end of the short-chain polyether side chain of the anti-mud functional segment A.
[0014] Preferably, the anti-intercalation layer end cap structure is an organic group with steric hindrance effect, which is selected from at least one of alicyclic structures containing bridge rings or polycyclic rigid skeletons, and aliphatic structures with three-dimensional configuration and high branching degree.
[0015] Preferably, the short-chain polyether side chain of the anti-mud functional segment A is further connected to a weakly charged end group, which is an amphoteric group.
[0016] Preferably, the short-chain polyether side chain is derived from isopentenyl polyoxyethylene ether. The number of repeating polyoxyethylene units is preferably 8-15.
[0017] Preferably, the number of polyoxyethylene repeating units in the long-chain polyether side chain is 45-90.
[0018] Preferably, based on the total number of molar segments of the comb copolymer, the molar percentage of the anti-mud functional segment A is 10%-60%, more preferably 20%-45%.
[0019] This invention also provides a method for preparing a sequence-segmented long- and short-chain block polycarboxylate superplasticizer, comprising the following steps:
[0020] S100. Preparation of intermediate A:
[0021] An esterification reaction is carried out between a short-chain polyether macromonomer with unsaturated bonds and an acylation reagent containing an anti-intercalation end-cap structure under alkaline conditions to obtain intermediate A.
[0022] S200. Preparation of intermediate B:
[0023] Short-chain polyether macromonomers with unsaturated bonds are reacted with haloacyl halides, then reacted with secondary amines to introduce tertiary amine groups, and then reacted with sulcinolone or halocarboxylate to generate intermediate B.
[0024] S300. Sequence segmented copolymerization:
[0025] In the presence of an initiator, a mixture containing an unsaturated carboxylic acid monomer, intermediate A and / or intermediate B is subjected to a first-stage polymerization to form the anti-sludge functional segment A; more specifically, the initiator is ammonium persulfate.
[0026] In the presence of the first-stage polymerization product, a mixture containing unsaturated carboxylic acid monomers and long-chain polyether macromonomers is added dropwise to carry out a second-stage polymerization, grafting to form the stable slump-holding segment B, thereby obtaining the sequence segmented long and short chain block polycarboxylic acid water-reducing agent.
[0027] Preferably, in step S100, the acylation agent includes at least one of adamantane-1-formyl chloride, norborneneformyl chloride, and tert-butylacetyl chloride.
[0028] Preferably, in step S200, the haloacyl halide includes chloroacetyl chloride or bromoacetyl bromide;
[0029] The secondary amine includes dimethylamine.
[0030] Preferably, in step S200, the sulfonyl lactone includes 1,3-propanesulfonyl lactone or 1,4-butanesulfonyl lactone.
[0031] The beneficial effects of this invention are:
[0032] (1) For the first time, a sequence segmented structure with anti-mud effect was introduced into the molecular design of polycarboxylate superplasticizer, so as to achieve the synergistic effect of anti-mud and anti-slump functions in the same molecule, rather than random copolymerization or simple compounding.
[0033] (2) By using the anti-intercalation cap structure at the end of the short-chain side chain, the clay intercalation adsorption is inhibited at the molecular geometry level, breaking through the traditional approach of relying solely on "shortening the side chain" to improve the anti-mud performance.
[0034] (3) The switchable weak charge / zwitterionic end group is precisely positioned at the end of the short chain anti-mud segment side chain, which reduces the risk of failure of water-reducing agent in complex mineral system while ensuring rapid adsorption.
[0035] (4) Compared with conventional long and short chain random mixed polycarboxylate superplasticizers, the present invention exhibits higher effective utilization rate, lower dosage sensitivity and more stable construction performance in mud-containing aggregate systems. Detailed Implementation
[0036] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.
[0037] In the embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.
[0038] Example 1
[0039] Preparation of segmented short-chain functional enriched anti-mud polycarboxylate superplasticizer, the superplasticizer molecule containing terminal caps and zwitterions:
[0040] Short-chain polymerizable double bonds, namely EPEG-OH, with EO≈10, were selected as raw materials to prepare two types of short-chain macromonomers, denoted as intermediate A and intermediate B, respectively.
[0041] S100. Preparation of intermediate A:
[0042] Add 20.0 g (0.040 mol) of short-chain EPEG-OH with unsaturated bonds (EO≈10, calculated as Mn≈500) and 80 mL of anhydrous DCM to a 250 mL three-necked flask, incubate on ice at 0-5 °C, and then add 8.1 g (0.080 mol) of triethylamine.
[0043] Dissolve 8.3 g (0.044 mol) of adamantane-1-formyl chloride in 20 mL of DCM and add it dropwise to the three-necked flask over 30 min. After the addition is complete, stir at room temperature for 4 h. Filter to remove salt, evaporate the filtrate by rotary evaporation, and remove small molecules by precipitation / reprecipitation with a small amount of diethyl ether to obtain a short-chain functional macromonomer with a terminal cap, i.e., intermediate A.
[0044] S200. Preparation of intermediate B:
[0045] In a 250 mL three-necked flask, 20.0 g (0.040 mol) of short-chain EPEG-OH (EO≈10) with unsaturated bonds was dissolved in 80 mL of anhydrous DCM. At 0–5 °C, 8.1 g (0.080 mol) of triethylamine was added, followed by dropwise addition of 3.6 g (0.032 mol) of chloroacetyl chloride (dissolved in 20 mL of DCM, added over 30 min). After reacting at room temperature for 2 h, the intermediate EPEG-OCO-CH2Cl was obtained. After filtration to remove salt and rotary evaporation, the intermediate EPEG-OCO-CH2Cl was dissolved in 60 mL of anhydrous acetonitrile, and 0.06 mol of dimethylamine was added. The reaction was carried out at 60 °C for 6 h, causing the –CH2Cl group to undergo SN2 substitution to generate EPEG-OCO-CH2-N(CH3)2, denoted as Ms-N. After the reaction, the solvent was removed, and small molecules were removed by reprecipitation / ultrafiltration.
[0046] The Ms-N obtained in the previous step was dissolved in 60 mL of anhydrous acetonitrile, and 5.5 g (0.040 mol) of potassium carbonate and 4.9 g (0.040 mol) of 1,3-propanesulfonyl lactone were added. The mixture was stirred at 60 °C for 6 h. After cooling and filtration to remove salt, the acetonitrile was rotary evaporated, and the small molecules were removed by ethanol / ether reprecipitation or ultrafiltration to obtain a short-chain macromonomer with terminal sulfobetaine, namely intermediate B.
[0047] Synthesis of S300 polycarboxylate superplasticizer:
[0048] Add 250g of deionized water to a 1L three-necked flask, stir mechanically, purge with nitrogen for 30min, and heat to 70℃. Add 30.0g (0.416mol) of acrylic acid AA and neutralize to pH 5.5-6.5 (approximately 60mol%) to prepare an unsaturated acid solution. After preparation, divide the unsaturated acid solution into two equal portions.
[0049] Mix 6.0g of intermediate A and 6.0g of intermediate B to prepare a short-chain functional monomer mixture. Add 1 part of the above-mentioned unsaturated acid solution to the short-chain functional monomer mixture to form a short-chain functional segment feeding solution, denoted as short-chain solution.
[0050] Weigh 45.0g of long-chain EPEG macromonomer (EO≈45~60, Mn≈2400) and add it to another part of unsaturated acid solution to form a long-chain stable segment feeding solution, which is denoted as long-chain solution.
[0051] In the initial stage of free radical polymerization: add the short-chain liquid all at once, keep it at 70℃ for 30 min, and then add 0.60 g of APS (ammonium persulfate) (dissolved in 10 g of water) dropwise as an initiator;
[0052] Mid-stage of free radical polymerization: After 60 min of short-chain liquid polymerization, long-chain liquid is added dropwise (completed in 60-90 min), and 0.20 g of APS is added at the beginning and mid-stage of long-chain liquid polymerization.
[0053] Late stage of free radical polymerization: After the addition is completed, react at 70℃ for 60 min, cool down to 40℃, adjust the pH to 6.5-7.5 and add water to about 500 mL to obtain the mother liquor of the sequence segmented anti-mud polycarboxylate superplasticizer.
[0054] Example 2
[0055] Preparation of gradient-distributed short-chain functional enriched anti-mud polycarboxylate superplasticizer:
[0056] The preparation methods for intermediates A and B are the same as in Example 1, except that:
[0057] In step S300, the short-chain functional macromonomer and the long-chain EPEG monomer are fed in a gradient manner.
[0058] The specific tiered feeding method is as follows:
[0059] Only short-chain liquids are added in the initial stage of free radical polymerization;
[0060] During the intermediate stage of free radical polymerization, short-chain and long-chain liquids are added in a mixed manner.
[0061] Only long-chain liquids are added in the later stages of free radical polymerization;
[0062] A mud-resistant polycarboxylate superplasticizer with short-chain functional monomers distributed in a gradient along the main chain was obtained.
[0063] Example 3
[0064] Preparation of segmented anti-intercalation volume cap polycarboxylate superplasticizer, wherein the superplasticizer molecule does not contain short-chain macromonomers with terminal sulfobetaine:
[0065] The other steps are the same as in Example 1, except that:
[0066] Only intermediate A is added to the short-chain liquid, and an equal amount of long-chain EPEG monomer as intermediate b is added in the later stage of free radical polymerization.
[0067] A segmented polycarboxylate superplasticizer with short-chain anti-intercalation layer volume cap enrichment but without zwitterionic end groups was obtained.
[0068] Comparative Example 1
[0069] Preparation of random copolymerized long and short chain polycarboxylate superplasticizers:
[0070] The other steps are the same as in Example 1, except that:
[0071] Replace the EPEG-OH in Example 1 with an equal amount of conventional short-chain EPEG (EO≈10);
[0072] In step S300, when the polymerization reaction begins, short-chain liquid and long-chain liquid are added dropwise simultaneously, and aqueous free radical polymerization is carried out without controlling the order of addition.
[0073] Because no segmented or gradient feeding was performed, and the short-chain monomers did not contain anti-intercalation volume caps or zwitterionic end groups, a random copolymer polycarboxylate superplasticizer was obtained.
[0074] Comparative Example 2
[0075] Polycarboxylate superplasticizers containing only long-chain EPEG:
[0076] The other steps are the same as in Example 1, except that:
[0077] Without steps S100 and S200, intermediate A and intermediate are replaced with equal amounts of long-chain EPEG (EO≈45–60), and only long-chain EPEG (EO≈45–60) is used to carry out aqueous free radical polymerization with acrylic acid to obtain a conventional long-chain polycarboxylate superplasticizer.
[0078] Comparative Example 3
[0079] Polycarboxylate superplasticizer containing only short-chain EPEG
[0080] The other steps are the same as in Example 1, except that:
[0081] Without steps S100 and S200, intermediate A and intermediate are replaced with equal amounts of short-chain EPEG (EO≈10), and only short-chain EPEG (EO≈10) is used to perform free radical polymerization with acrylic acid in aqueous solution to obtain a conventional short-chain polycarboxylate superplasticizer.
[0082] Mortar testing and verification
[0083] Mortar tests were performed on the samples obtained from the examples and comparative examples.
[0084] The mortar mix ratio is cement:sand:water = 450:1350:225 (w / c = 0.50).
[0085] The general method for introducing mud content is the artificial clay method: add sodium montmorillonite (Na-MMT) to standard sand at a rate of 0%, 1.0%, or 2.0% of the sand mass, dry mix for 2 minutes, and then mix into mortar.
[0086] Specific test content: With a fixed sample dosage of 0.12% (solid content), the initial fluidity D0 and one-hour fluidity D60 of the mortar were measured under different mud contents.
[0087] The test results are shown in Tables 1 and 2.
[0088] Table 1. Mortar spread (mm) at different mud contents with a fixed admixture content of 0.12% (solid content).
[0089]
[0090] Table 2 Mud Retention Rate (R0, R) 60 Calculation results (dosage 0.12%)
[0091] sample <![CDATA[1% mud R0]]> <![CDATA[1% mud R 60 > <![CDATA[2% mud R0]]> <![CDATA[2% mud R 60 > Example 1 0.91 0.86 0.82 0.73 Example 2 0.91 0.85 0.8 0.7 Example 3 0.85 0.75 0.69 0.48 Comparative Example 1 0.76 0.57 0.56 0.34 Comparative Example 2 0.7 0.44 0.48 0.24 Comparative Example 3 0.83 0.67 0.62 0.42
[0092] As shown in Table 1, under the condition of fixed admixture, the mortar fluidity of the samples of Example 1 (segmentation + volume cap + zwitterion) and Example 2 (gradient + volume cap + zwitterion) is least affected by the increase of mud content, with Example 1 showing particularly good performance.
[0093] Meanwhile, comparing the mortar spread over one hour, it can be seen that Examples 1 and 2 can still maintain relatively good fluidity even with an increase in mud content, demonstrating the good slump retention performance of the two samples.
[0094] As shown in Table 2, the mud retention rate calculated from Table 1 more clearly reflects the above trend.
[0095] In summary, the samples synthesized according to Examples 1 and 2 have good anti-mud and anti-collapse properties, with Example 1 being the best.
[0096] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.
Claims
1. A sequence-segmented long-short-chain block polycarboxylic water reducer, characterized by, The water-reducing agent comb-shaped copolymer, a main chain of the comb-shaped copolymer is a carboxyl-containing vinyl polymer skeleton, side chains of the comb-shaped copolymer include polyether side chains, and a molecular structure of the comb-shaped copolymer at least includes two segments different in structure and function along the main chain direction: An anti-mud function segment A, the anti-mud function segment A is rich in short-chain polyether side chains, the number of polyoxyethylene repeating units of the short-chain polyether side chains is 3-20, and a terminal of the short-chain polyether side chains is connected with an anti-intercalation terminal cap structure; And A stable slump retaining segment B, the stable slump retaining segment B is rich in long-chain polyether side chains, the number of polyoxyethylene repeating units of the long-chain polyether side chains is 30-120; Wherein, the anti-mud function segment A and the stable slump retaining segment B are distributed in a segmented or gradient manner on the main chain, and the anti-intercalation terminal cap structure mainly or only exists at the terminal of the short-chain polyether side chains of the anti-mud function segment A.
2. The sequence segmented long-short-chain block polycarboxylic acid water reducer according to claim 1, characterized by, The anti-intercalation terminal cap structure is an organic group with a steric hindrance effect, which is selected from at least one of alicyclic structures containing a bridged ring or a polycyclic rigid skeleton, and aliphatic structures with a three-dimensional spatial configuration and high branching degree. 3.The sequence segmented long-short-chain block polycarboxylic acid water reducer according to claim 1, characterized in that, The terminal of the short-chain polyether side chains of the anti-mud function segment A is also connected with a weak charge end group, and the weak charge end group is a zwitterionic group. 4.The sequential segment type long-short-chain block polycarboxylic acid water reducer according to claim 1, characterized in that, The short-chain polyether side chains are derived from isopentenyl alcohol polyoxyethylene ether.
5. The sequence segmented long-short chain block polycarboxylic acid water reducer according to claim 1, characterized in that, The number of polyoxyethylene repeating units of the long-chain polyether side chains is 45-90. 6.The sequential segment type long-short-chain block polycarboxylic acid water reducer according to claim 1, characterized in that, The mole percentage of the anti-mud function segment A is 10%-60% based on the total segment mole number of the comb-shaped copolymer.
7. A method for producing the sequence segmented long-short chain block polycarboxylic acid water reducing agent according to any one of claims 1 to 6, characterized by, The method comprises the steps of: S100. Preparing intermediate A: esterification of a short-chain polyether macromonomer with an unsaturated bond and an acylating agent containing an anti-intercalation terminal cap structure under alkaline conditions to obtain intermediate A; S200. Preparing intermediate B: reacting a short-chain polyether macromonomer with an unsaturated bond with a halogenated acyl halide, then with a secondary amine to introduce a tertiary amine group, and then adding a sultone or halogenated carboxylic acid salt to generate intermediate B; S300. Sequential segmented copolymerization: mixing intermediate A and / or intermediate B containing unsaturated carboxylic acid monomers in the presence of an initiator to perform first-stage polymerization to form the anti-mud function segment A; dropping a mixture containing unsaturated carboxylic acid monomers and long-chain polyether macromonomers in the presence of the first-stage polymerization product to perform second-stage polymerization to graft to form the stable slump retaining segment B, thereby obtaining the sequential segmented long-short chain block polycarboxylic acid water-reducing agent.
8. The method of claim 7, wherein, In step S100, the acylating agent includes at least one of adamantane-1-formyl chloride, norbornane formyl chloride, and tert-butyl acetyl chloride.
9. The method of claim 7, wherein, In step S200, the halogenated acyl halide includes chloroacetyl chloride or bromoacetyl bromide; The secondary amine includes dimethylamine.
10. The method of claim 7, wherein, In step S200, the sultone includes 1,3-propane sultone or 1,4-butane sultone.