Polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of building materials, and particularly discloses a polycarboxylate superplasticizer as well as a preparation method and application thereof. The polycarboxylate superplasticizer comprises a polymer main chain and a plurality of polyether side chains, firstly alkynyl and azido are respectively modified on a polyether macromonomer and hydroxyethyl acrylate, then the polyether macromonomer and hydroxyethyl acrylate are connected through a triazole ring by utilizing a CuAAC reaction to assemble polyether side chains, and finally through a free radical copolymerization reaction, the polycarboxylate superplasticizer is obtained. A side chain is accurately connected to a main chain formed by copolymerization of an unsaturated carboxylic acid monomer and an unsaturated sulfonic acid monomer. According to the invention, ordered distribution of a plurality of functional groups on a polymer molecular chain is realized, a synergistic effect is exerted, good balance of a plurality of properties of the polycarboxylate superplasticizer is ensured, the water reducing property and segregation resistance of the polycarboxylate superplasticizer are effectively improved, and the comprehensive properties are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a polycarboxylate superplasticizer, its preparation method, and its application. Background Technology

[0002] The traditional synthesis technology of polycarboxylate superplasticizers is based on random copolymerization with free radical aqueous solution, which has led to three major technical branches: monomer modification, composite doping, and process optimization. These technologies are widely used in concrete engineering. Traditional processes for preparing polycarboxylate superplasticizers involve graft copolymerization of polyether macromonomers with maleic anhydride and acrylate monomers. This introduces retarding (hydroxyl) and anti-segregation (sulfonic acid) groups, resulting in representative products such as slump-resistant and mud-resistant polycarboxylate superplasticizers.

[0003] In traditional preparation processes, functional groups (carboxyl, hydroxyl, and sulfonic acid groups) are randomly distributed in the main chain / side chain, resulting in poor synergy of the water-reducing agent's "adsorption-dispersion-slump retention" function. Furthermore, low molecular weight components are easily adsorbed by clay (reducing water reduction rate), while high molecular weight components easily increase concrete viscosity (affecting fluidity), leading to large fluctuations in the water-reducing agent's performance and insufficient quality stability. This is mainly because traditional preparation processes often employ free radical copolymerization, where the monomer addition sequence and chain termination mode (bimolecular termination / chain transfer) cannot be precisely controlled, resulting in disordered functional group distribution and a wide molecular weight distribution (PDI>1.8). For example, when acrylic acid (AA) is randomly copolymerized with 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sulfonic acid groups may concentrate at the ends or middle of the molecular chain, failing to form uniform adsorption sites. The hydroxyl groups of the polyether macromonomer easily undergo esterification side reactions with the carboxylic acid monomer (conversion rate 5%~10%), leading to side chain breakage and reducing steric hindrance effect; moisture in the reaction system easily triggers free radical hydrolysis, further exacerbating structural heterogeneity.

[0004] Controlled polymerization technology can improve the above problems, but the current method still has shortcomings. Introducing functional groups through conventional grafting reactions results in low grafting rates (60%~70%) and numerous byproducts, creating a bottleneck for large-scale production. Furthermore, this method currently faces the challenge of synergistic effects between high water reduction and anti-segregation, mainly manifested in the following ways: increasing carboxyl group density to improve water reduction leads to decreased concrete cohesiveness (increased risk of segregation); enhancing cohesiveness through crosslinking monomers (MBA) easily leads to excessive crosslinking of molecular chains (gelation rate >5%), resulting in loss of fluidity. Therefore, existing polycarboxylate superplasticizer synthesis technologies suffer from core defects such as poor controllability of molecular structure, prominent performance synergy contradictions, weak adaptability to harsh environments, and insufficient environmental and industrial compatibility. Consequently, the resulting polycarboxylate superplasticizers typically exhibit poor water reduction and anti-segregation effects, making them unsuitable for the stringent comprehensive performance requirements of high-end engineering projects. Summary of the Invention

[0005] The present invention aims to provide a polycarboxylate superplasticizer, its preparation method and application, in order to solve the problems of poor water reduction performance and poor anti-segregation effect of existing polycarboxylate superplasticizers.

[0006] The water-reducing agent provided by this invention comprises a polymer backbone and several polyether side chains; the polymer backbone is formed by at least an unsaturated carboxylic acid monomer and an unsaturated sulfonic acid monomer through a free radical copolymerization reaction, and the polyether side chains are formed by click-modified polyether macromonomers connected to the polymer backbone through the free radical copolymerization reaction; the click-modified polyether macromonomer is generated by an alkynylated polyether macromonomer and an azido-hydroxyethyl acrylate through an azido-alkynyl cycloaddition reaction, and contains a triazole ring structure, and the click-modified polyether macromonomer is connected to the polymer backbone using structural units from the azido-hydroxyethyl acrylate and / or structural units from the alkynylated polyether macromonomer.

[0007] The method for preparing the water-reducing agent provided by this invention includes the following steps: S1, the polyether macromonomer was modified by alkynylation using an alkynylating agent to obtain an alkynylated polyether macromonomer; S2, hydroxyethyl acrylate is modified by azidation with an azide reagent to obtain azidated hydroxyethyl acrylate; S3, in the presence of a copper catalyst, the alkynylated polyether macromonomer obtained in step S1 and the azido-alkynylated hydroxyethyl acrylate obtained in step S2 undergo an azido-alkynyl cycloaddition reaction to obtain the click-modified polyether macromonomer. S4. The click-modified polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated sulfonic acid monomer obtained in step S3 are subjected to free radical copolymerization to obtain a polycarboxylic acid water-reducing agent composed of a polymer backbone and several polyether side chains.

[0008] This invention abandons the traditional random grafting mode of free radical copolymerization and pioneers a modular stepwise synthesis process of "alkynylation-azidation-click grafting-copolymerization," achieving precise design of the molecular structure and performance breakthrough of polycarboxylate superplasticizers. The process first precisely modifies the ends of the polyether macromonomer and the hydroxyethyl acrylate (HEA) end, respectively. Then, using a highly selective azid-alkynyl cycloaddition reaction (CuAAC reaction), the two are linked through a highly polar and stable triazole ring to assemble a functional side chain. Finally, in the copolymerization reaction, the assembled side chain is precisely attached to the main chain. The click-modified polyether macromonomer obtained from the azide-acetylene cycloaddition reaction provides significant steric hindrance, thereby improving adhesion, better retaining moisture in concrete, and reducing bleeding. Furthermore, the click-modified polyether macromonomer contains triazole rings and diunsaturated double bonds. The strong polarity of the triazole rings and the crosslinking effect of the diunsaturated double bonds significantly improve the anti-segregation performance of the water-reducing agent. The carboxyl groups introduced into the unsaturated carboxylic acid monomer provide slow-release and hydration-regulating effects, while the sulfonic acid groups introduced into the unsaturated sulfonic acid monomer... It provides strong electrostatic repulsion. Therefore, after free radical copolymerization of click-modified polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated sulfonic acid monomer, a synergistic mechanism of "steric hindrance (click-modified polyether macromonomer side chain) - strong polarity (triazole ring) - crosslinking (click-modified polyether macromonomer) - hydration regulation (carboxyl group) - electrostatic repulsion (sulfonic acid group)" can be constructed as a whole. This breaks the bottleneck of mutual restriction between the properties of traditional water-reducing agents, thereby effectively improving the water-reducing performance and anti-segregation performance of polycarboxylic acid water-reducing agents.

[0009] When the water-reducing agent of this invention is used in the field of construction engineering, it can achieve a good balance between high water reduction (water reduction rate ≥38%), high slump retention (2h slump loss ≤10%), high segregation resistance (bleeding rate ≤1.0%) and high strength (7d compressive strength increase ≥15%) in concrete. It meets the stringent requirements of modern high-end engineering for concrete workability, durability and mechanical properties, and the comprehensive performance is significantly improved, which has good industrialization prospects. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in specific embodiments of this invention will be described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0011] The polycarboxylate superplasticizer provided by the present invention comprises a polymer backbone and several polyether side chains; the polymer backbone is formed by copolymerization of at least unsaturated carboxylic acid monomers and unsaturated sulfonic acid monomers, and the polyether side chains are formed by linking click-modified polyether macromonomers to the polymer backbone through the copolymerization reaction.

[0012] In this invention, the type of unsaturated carboxylic acid monomer is not particularly limited, but may include at least one of acrylic acid, methacrylic acid, and maleic anhydride.

[0013] In this invention, the type of unsaturated sulfonic acid monomer is not particularly limited, but may include at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium methylallyl sulfonate, styrene sulfonic acid, and vinyl sulfonic acid.

[0014] In this invention, the click-modified polyether macromonomer is generated from an alkynylated polyether macromonomer and an azido-hydroxyethyl acrylate via an azido-alkynyl cycloaddition reaction (click reaction). Specifically, the alkynylated polyether macromonomer is obtained by alkynylation modification of a polyether macromonomer, and the azido-hydroxyethyl acrylate is obtained by azido modification of hydroxyethyl acrylate. In the presence of a copper catalyst, the two react via a click reaction to generate a triazole ring structure, which links the two together into a single unit, i.e., the click-modified polyether macromonomer. The click-modified polyether macromonomer utilizes structural units derived from the azido-hydroxyethyl acrylate and / or structural units derived from the alkynylated polyether macromonomer to connect to the polymer backbone. These structural units can be the double bonds inherent in the azido-hydroxyethyl acrylate.

[0015] In this invention, the type of polyether macromonomer used in the alkynylated polyether macromonomer is not particularly limited, and examples include at least one selected from methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, and ethylene glycol monovinyl polyethylene glycol ether. The molar ratio of the alkynylated polyether macromonomer to the hydroxyethyl azidoacrylate is preferably 1:(0.9~1.3). Specifically, based on 1 mol of alkynylated polyether macromonomer, the amount of hydroxyethyl azidoacrylate is preferably 0.9~1.3 mol, such as 0.9 mol, 1.0 mol, 1.1 mol, 1.2 mol, 1.3 mol, etc.

[0016] In this invention, the preferred molar ratio of the click-modified polyether macromonomer, the unsaturated carboxylic acid monomer, and the unsaturated sulfonic acid monomer is 1:(2.5~6):(0.2~0.8). Specifically, based on 1 mol of click-modified polyether macromonomer, the preferred amount of the unsaturated carboxylic acid monomer is 2.5~6 mol, such as 2.5 mol, 3 mol, 3.5 mol, 4 mol, 4.5 mol, 5 mol, 5.5 mol, 6 mol, etc., and the preferred amount of the unsaturated sulfonic acid monomer is 0.2~0.8 mol, such as 0.2 mol, 0.4 mol, 0.6 mol, 0.8 mol, etc.

[0017] In this invention, the preparation process of the above-mentioned water-reducing agent adopts a modular stepwise synthesis process of "alkynylation-azidation-click grafting-copolymerization", and the specific process and principle are as follows: Step S1: The polyether macromonomer is modified by alkynylation using an alkynylating agent to obtain alkynylated polyether macromonomer.

[0018] The purpose of this step is to precisely modify the polyether macromonomer with an alkynyl group at its end through alkynylation modification. Therefore, the core of selecting the alkynylating agent used for alkynylation modification is to introduce an alkynyl group onto the terminal hydroxyl group of the polyether macromonomer, preferably at least one of propargyl isocyanate (PI) and propargyl bromide. Alkynylation modification is usually carried out in the presence of a catalyst, preferably at least one of dibutyltin dilaurate (DBTDL), bismuth neodecanoate (BiND), and tetrabutyl titanate (TBT). In this step, the molar ratio of the polyether macromonomer, catalyst, and alkynylating agent is preferably 1:(1.0~1.3):(0.001~0.005). Specifically, based on 1 mol of polyether macromonomer, the amount of catalyst is preferably 1.0~1.3 mol, such as 1.0 mol, 1.1 mol, 1.2 mol, 1.3 mol, etc., and the amount of alkynylating agent is preferably 0.001~0.005 mol, such as 0.001 mol, 0.002 mol, 0.003 mol, 0.004 mol, 0.005 mol, etc.

[0019] The reaction equations for modifying polyether macromonomers (R-OH) with two alkynylating agents are given below for further detailed explanation: (1) The alkynylating agent is propargyl isocyanate (PI, HC≡C-CH2-NCO) R-OH + HC≡C-CH2-NCO — (DBTDL, 60℃, 2-5h) → RO-CO-NH-CH2-C≡CH + H2O (trace amount); (2) The alkynylating agent is propargyl bromide (HC≡C-CH2-Br). R-OH + HC≡C-CH2-Br —(TBT, 60℃, 2-5h)→ RO-CH2-C≡CH + HBr(The reaction system is neutralized by a trace amount of base) In this invention, the conditions for alkynylation modification are not particularly limited, but preferably include a temperature of 50°C to 70°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, etc.; and a time of 2h to 5h, such as 2h, 3h, 4h, 5h, etc. Furthermore, the method of alkynylation modification is not particularly limited, and may include uniformly mixing the polyether macromonomer, catalyst, and alkynylating agent, then placing the resulting mixture under alkynylation modification conditions, and cooling after the reaction is complete to obtain the alkynylated polyether macromonomer.

[0020] Step S2: Hydroxyethyl acrylate is modified by azidation with an azide reagent to obtain azidated hydroxyethyl acrylate.

[0021] The purpose of this step is to precisely modify hydroxyethyl acrylate (HEA) with azidation. Therefore, the key to selecting the azidation reagent is to introduce azid groups onto the hydroxyl groups of the HEA while ensuring that the carbon-carbon double bonds at the ends, which are used for polymerization with the main chain, are not affected. The azidation reagent is preferably selected from azidocarboxylic acid esters, azidoyl halides, and azidosulfonyl halides. In this step, the molar ratio of hydroxyethyl acrylate, the azidation reagent, and the polyether macromonomer described in step S1 is preferably (0.8~1.5):(0.9~1.4):1. Specifically, taking the molar amount of the polyether macromonomer in step S1 as 1 part, the amount of hydroxyethyl acrylate is preferably 0.8~1.5 mol, such as 0.8 mol, 0.9 mol, 1.0 mol, 1.1 mol, 1.2 mol, 1.3 mol, 1.4 mol, 1.5 mol, etc., and the amount of azide reagent is preferably 0.9~1.4 mol, such as 0.9 mol, 1.0 mol, 1.1 mol, 1.2 mol, 1.3 mol, 1.4 mol, etc.

[0022] The following is a detailed explanation of the reaction equation for ethyl azide (EAz, N3-CH2-COO-C2H5) modified hydroxyethyl acrylate (HEA, CH2=CH-COO-CH2CH2-OH): CH2=CH-COO-CH2CH2-OH + N3-CH2-COO-C2H5—(60-80℃, 3-5h)→CH2=CH-COO-CH2CH2-O-CO-CH2-N3+C2H5OH In this invention, the conditions for the azidation modification are not particularly limited, but preferably include a temperature of 60℃~80℃, such as 60℃, 65℃, 70℃, 75℃, 80℃, etc.; and a time of 3h~5h, such as 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0023] Step S3: In the presence of a copper catalyst, the alkynylated polyether macromonomer obtained in step S1 and the azido-hydroxyethyl acrylate obtained in step S2 are subjected to a copper-catalyzed azido-alkynyl cycloaddition reaction to obtain a click-modified polyether macromonomer with a triazole ring structure.

[0024] The purpose of this step is to link the functional monomers formed in the first two steps using a highly selective copper-catalyzed azido-acetylene cycloaddition reaction (CuAAC click reaction). The acetylated polyether macromonomer obtained in step S1 has an acetyl group, and the azidolated hydroxyethyl acrylate obtained in step S2 has an azido group. The two monomers can form a triazole ring structure through the CuAAC click reaction, and then link together to form a polyether side chain. This reaction has high selectivity, few byproducts, and facilitates the formation of structurally well-defined side chains, avoiding the uncertainty of traditional side chain structures.

[0025] The copper catalyst used in the CuAAC click reaction is preferably a mixture of cuprous ions and ligands. Combining cuprous ions with ligands can improve stability and catalytic efficiency. In some specific embodiments of the present invention, the copper catalyst is preferably a complex of cuprous chloride and 2,2'-bipyridine (CuCl / Bpy complex). In this step, the molar ratio of alkynylated polyether macromonomer, azidolated hydroxyethyl acrylate, cuprous ions, and ligands is 1:(0.9~1.3):(0.05~0.12):(0.1~0.24). Specifically, based on 1 part of the alkynylated polyether macromonomer, the preferred amount of azidolated hydroxyethyl acrylate is 0.9~1.3 mol, such as 0.9 mol, 1.0 mol, 1.1 mol, 1.2 mol, 1.3 mol, etc.; the preferred amount of cuprous ions is 0.05~0.12 mol, such as 0.05 mol, 0.06 mol, 0.07 mol, 0.08 mol, 0.09 mol, 0.11 mol, 0.12 mol, etc.; and the preferred amount of ligands is 0.1~0.24 mol, such as 0.1 mol, 0.12 mol, 0.14 mol, 0.16 mol, 0.18 mol, 0.2 mol, 0.22 mol, 0.24 mol, etc.

[0026] The following example illustrates the CuAAC click reaction equation: Step 1 forms an alkynylated polyether macromonomer (R'-C≡CH, where R' represents the polyether chain of the product from Step 1), Step 2 forms an azide-modified hydroxyethyl acrylate (N3-CH2-COO-CH2CH2-O-CO-CH=CH2), and the catalyst is a CuCl / Bpy complex. R'-C≡CH + N3-CH2-COO-CH2CH2-O-CO-CH=CH2—(CuCl / Bpy, 25℃, 1h)→ R'-[1,2,3-triazole ring]-CH2-COO-CH2CH2-O-CO-CH=CH2 In this invention, the preferred conditions for the azide-alkyne cycloaddition reaction include a temperature of 20°C to 40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, etc.; and a time of 0.5h to 5h, such as 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0027] Step S4: The click-modified polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated sulfonic acid monomer obtained in step S3 are subjected to free radical copolymerization to obtain a polycarboxylic acid water-reducing agent composed of a polymer backbone and several polyether side chains.

[0028] The purpose of this step is to assemble the click-modified polyether macromonomer, which is precisely synthesized in step S3, with unsaturated carboxylic acid monomers and unsaturated sulfonic acid monomers that provide adsorption groups through free radical copolymerization, thereby constructing a complete molecular chain.

[0029] In this invention, the free radical copolymerization reaction is not particularly limited in method, and materials can be added and reacted according to various existing conventional methods. In one specific embodiment, the free radical copolymerization reaction is carried out in the presence of an initiator and a chain transfer agent. The initiator can be selected from at least one of peroxide initiators, azo initiators, and redox initiators, preferably a redox initiator, such as ammonium persulfate. The chain transfer agent can be selected from thiols, preferably at least one of mercaptopropionic acid and mercaptoethanol. In this step, the molar ratio of the click-modified polyether macromonomer, unsaturated carboxylic acid monomer, unsaturated sulfonic acid monomer, initiator, and chain transfer agent is preferably 1:(2.5~6):(0.2~0.8):(0.02~0.05):(0.015~0.03). Specifically, taking 1 mol of click-modified polyether macromonomer as the basis, the preferred amount of unsaturated carboxylic acid monomer is 2.5~6.0 mol, such as 2.5 mol, 3.0 mol, 3.5 mol, 4.0 mol, 4.5 mol, 5.0 mol, 5.5 mol, 6.0 mol, etc.; the preferred amount of unsaturated sulfonic acid monomer is 0.2~0.8 mol, such as 0.2 mol, 0.3 mol, 0.4 mol, 0.5 mol, 0.6 mol, 0.7 mol, 0.8 mol, etc.; the preferred amount of initiator is 0.02~0.05 mol, such as 0.02 mol, 0.03 mol, 0.04 mol, 0.05 mol, etc.; and the preferred amount of chain transfer agent is 0.015~0.03 mol, such as 0.015 mol, 0.02 mol, 0.025 mol, 0.03 mol, etc.

[0030] The following example uses ammonium persulfate as the initiator and mercaptopropionic acid as the catalyst to provide a further detailed explanation of the free radical copolymerization reaction equation: n1M1+ n2CH2=CH-COOH + n3CH2=C(CH3)-CONH-CH2-C(CH3)2-SO3H → [-CH2-C(R1)-CH2-CH(COOH)-CH2-C(CH3)(CONH-CH2-C(CH3)2-SO3H)-] n Wherein, M1 represents the click-modified polyether macromonomer formed in step S3, and R1 represents the side chain formed on the main chain after free radical polymerization, that is, the remaining molecular chain after removing the double bonds of M1 used for copolymerization with the main chain.

[0031] In this invention, the conditions for the free radical polymerization reaction are not particularly limited, but preferably include a temperature of 60℃~80℃, such as 60℃, 65℃, 70℃, 75℃, 80℃, etc.; and a time of 1h~5h, such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0032] In this invention, the preparation method of the polycarboxylate superplasticizer generally includes adjusting the pH value of the resulting reaction product to 6.5-7.5 after the free radical copolymerization reaction is completed, thereby obtaining the polycarboxylate superplasticizer.

[0033] The polycarboxylate superplasticizer of this invention can be widely used in the construction field, specifically for preparing various concrete products, such as blocks, permeable bricks, manhole covers, and pipes. The recommended dosage of this polycarboxylate superplasticizer in concrete, based on the mass of its effective solids, is 0.1% to 0.5% of the total mass of the concrete cementitious materials. Specifically, the mass of the effective solids in the polycarboxylate superplasticizer can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., of the total mass of the concrete cementitious materials.

[0034] The technical solution of the present invention will be further described in detail and completely below with reference to the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0035] Example 1 S1, alkynylation modification 10 kg of methyl allyl polyoxyethylene ether (purchased from Guangdong Fangxin Biotechnology Co., Ltd., brand name CAS No. 27274-31-3, the same below) was added to the reaction vessel, the temperature was raised to 60℃, 0.02 kg of dibutyltin dilaurate (DBTDL) catalyst was added, the mixture was stirred continuously, and propargyl isocyanate (0.57 kg) was slowly added dropwise over a period of 30 min. After the addition was completed, the mixture was kept at 60℃ for 2 h. After the reaction was completed, the temperature was lowered to 40℃ to obtain the alkynylated polyether.

[0036] S2, azidation modification Add 0.6 kg of hydroxy acrylate (HEA) and 5 kg of anhydrous ethanol to a three-necked flask, stir to dissolve, add 0.65 kg of ethyl azide (EAz), heat to 70 °C, react for 3 h, after the reaction is complete, remove ethanol and unreacted EAz by vacuum distillation (vacuum degree -0.09 MPa, 60 °C) to obtain azidated HEA (HEA-N3).

[0037] S3, CuAAC reaction Add approximately 10.5 kg of alkynylated polyether (TPEG-Alkyne, prepared by S1) and 10 kg of deionized water to the reactor, stir to dissolve, cool to 25 °C, and then add 0.03 kg of CuCl and 0.09 kg of 2,2'-bipyridine (Bpy). Stir for 10 min to form a complex catalyst, and slowly add HEA (HEA-N3) prepared by S2 dropwise over 10 min. React at room temperature (25 °C) for 1 h, add 0.5 kg of diatomaceous earth to the system to remove unreacted catalyst, stir for 30 min, filter to remove Cu(I) complex, and obtain click-modified polyether macromonomer (TPEG-Triazole-HEA).

[0038] S4, free radical copolymer Add the remaining deionized water (10 kg) to a reactor containing 10.5 kg of click-modified polyether macromonomer. Stir and heat to 70°C, holding for 10 min. Then, simultaneously add solutions A and B dropwise over 3 h. When solutions A and B have been added for 1 h, start adding solution C dropwise, maintaining the reaction temperature at 70°C. The dropwise addition time for solution C is controlled to 2 h. After the addition is complete, heat to 75°C and hold for 2 h. Then cool to below 40°C and slowly neutralize to pH 6.5 with 30% NaOH solution. Stir for 30 min, add 10 g of silicone defoamer, stir for 20 min, and filter through a 200-mesh filter cloth to obtain the finished polycarboxylate superplasticizer. Solution A is prepared by dissolving 2.4 kg of acrylic acid (AA), 0.8 kg of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 2 kg of deionized water. Solution B is prepared by dissolving 0.15 kg of ammonium persulfate (APS) and 1 kg of deionized water. Solution C was dissolved by stirring in 0.07 kg MPa and 0.5 kg deionized water.

[0039] Example 2 S1, alkynylation modification 10 kg of methyl allyl polyoxyethylene ether was added to the reactor, the temperature was raised to 60 °C, 0.02 kg of bismuth neodecanoate catalyst was added, and 0.65 kg of propargyl bromide alkynylating reagent was slowly added dropwise over a period of 50 min. After the addition was complete, the reaction was maintained at 60 °C for 4 h. After the reaction was completed, the temperature was lowered to 35 °C to obtain alkynylated polyether alkynylated HPEG (HPEG-Alkyne).

[0040] S2, azidation modification Add 0.6 kg of hydroxy acrylate (HEA) and 5 kg of anhydrous ethanol to a three-necked flask, stir to dissolve, add 0.65 kg of ethyl azide (EAz), heat to 65 °C, and react for 5 h. After the reaction is complete, remove ethanol and unreacted EAz by vacuum distillation (vacuum degree -0.09 MPa, 60 °C) to obtain azidated HEA (HEA-N3).

[0041] S3, CuAAC reaction HPEG-Alkyne (approximately 10.5 kg) and 10 kg of deionized water were added to the reactor and stirred to dissolve. After cooling to 30°C, 0.03 kg of CuCl and 0.09 kg of 2,2'-bipyridine (Bpy) were added and stirred for 25 min to form a complex catalyst. HEA azide (HEA-N3) was slowly added dropwise over a period of 20 min. The reaction was carried out at room temperature (25°C) for 1 h. Diatomaceous earth was added to the system and stirred for 45 min. The Cu(I) complex was removed by filtration to obtain the click-modified polyether macromonomer (HPEG-Triazole-HEA).

[0042] S4, free radical copolymer Add 5 kg of remaining deionized water to a reactor containing 10.5 kg of click-modified polyether macromonomer. Stir and heat to 75°C, holding for 10 min. Simultaneously add solutions A and B dropwise over 5 h. When solutions A and B have been added for 1 h, start adding solution C dropwise, maintaining the reaction temperature at 60°C. The dropwise addition time for solution C is controlled at 4 h. After the addition is complete, heat to 80°C and maintain for 1.55 h. Then cool to below 40°C and slowly neutralize to pH 7.5 with 30% NaOH solution. Stir for 30 min, add 5 g of silicone defoamer, stir for 20 min, and filter through a 200-mesh filter cloth to obtain the finished polycarboxylate superplasticizer. Solution A is prepared by dissolving 2.4 kg of acrylic acid (AA), 0.8 kg of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 2 kg of deionized water. Solution B is prepared by dissolving 0.15 kg of ammonium persulfate (APS) and 1 kg of deionized water. Solution C is prepared by stirring and dissolving 0.07 kg of mercaptopropionic acid (MPA) and 0.5 kg of deionized water.

[0043] Example 3 S1, alkynylation modification 10.0 kg of ethylene glycol monovinyl polyethylene glycol ether (purchased from Guangzhou Huntsman Chemical Co., Ltd., brand name EPEG-2400) was added to the reactor, the temperature was raised to 60℃, 0.01 kg of TBT catalyst tetrabutyl titanate (TBT) and 0.05 kg of anhydrous ethanol were added, the mixture was stirred evenly, and 0.59 kg of PI was slowly added dropwise over a period of 45 min. After the addition was completed, the mixture was kept at 60℃ for 4 h. After the reaction was completed, the temperature was lowered to 35℃ to obtain alkynylated polyether.

[0044] S2, azidation modification Add (0.62 kg) hydroxy acrylate (HEA) and (5.0 kg) anhydrous ethanol to a three-necked flask, stir to dissolve, add (0.68 kg) ethyl azide (EAz), heat to 75 °C, react for 5 h, after the reaction is completed, remove ethanol and unreacted EAz by vacuum distillation (vacuum degree -0.09 MPa, 60 °C) to obtain azidated HEA (HEA-N3).

[0045] S3, CuAAC reaction Add alkynylated EPEG (approximately 10.5 kg) and deionized water (10.0 kg) to the reactor, stir to dissolve, cool to 20 °C, then add 0.03 kg CuCl and 0.09 kg 2,2'-bipyridine (Bpy), stir for 25 min to form a complex catalyst, slowly add azide-modified HEA (HEA-N3) dropwise over 20 min, react at room temperature (25 °C) for 1 h, add diatomaceous earth to the system, stir for 60 min, filter to remove Cu(I) complex, and obtain click-modified polyether macromonomer (EPEG-Triazole-HEA).

[0046] S4, free radical copolymer Add the remaining deionized water (10.0 kg) to a reactor containing 10.5 kg of click-modified polyether macromonomer. Stir and heat to 65°C, holding for 10 min. Then, simultaneously add solutions A and B dropwise over a period of 4 h. When solutions A and B have been added for 1 h, start adding solution C dropwise, maintaining the reaction temperature at 65°C. The dropwise addition time for solution C is controlled to 3 h. After the addition is complete, heat to 75°C and maintain for 4 h. Then, cool to below 40°C and slowly neutralize to pH 7 with 30% NaOH solution. Stir for 30 min, add 8 g of silicone defoamer, stir for 20 min, and filter through a 200-mesh filter cloth to obtain the finished polycarboxylate superplasticizer. Solution A is prepared by dissolving 2.5 kg of acrylic acid (AA), 0.85 kg of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 2.0 kg of deionized water. Solution B is prepared by dissolving 0.16 kg of ammonium persulfate (APS) and 1 kg of deionized water. Solution C is prepared by stirring and dissolving 0.07 kg of mercaptoethanol (ME) and 0.5 kg of deionized water.

[0047] Comparative Example 1 A polycarboxylate superplasticizer was prepared according to the method of Example 1, except that click-modified polyether macromonomers were not used. The remaining steps and conditions were the same as in Example 1, and a reference polycarboxylate superplasticizer was obtained.

[0048] Comparative Example 2 The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the click-modified polyether macromonomer was replaced with the same part by weight of methyl allyl polyoxyethylene ether, and the remaining steps and conditions were the same as in Example 1, to obtain the reference polycarboxylate superplasticizer.

[0049] Test case According to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures", the polycarboxylate superplasticizers prepared in the above examples and comparative examples were tested for mortar fluidity and compressive strength.

[0050] According to GB / T 50080 2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the polycarboxylate superplasticizer prepared in the above examples and comparative examples was added to the concrete, and the compressive strength of the concrete was determined. The water-cement ratio was fixed at 0.48. The concrete mix proportion was: 175 kg of water, 360 kg of cement (Chunchi cement P.052.5R), 790 kg of manufactured sand (containing 5% mud) and 1060 kg of stone.

[0051] Table 1. Concrete Experiment Results

[0052] The results show that, compared with the comparative examples, the polycarboxylate superplasticizers provided in Examples 1-3, when applied to concrete, not only improve the initial mortar fluidity of cement as well as the mortar fluidity at 1h and 2h, but also exhibit significant anti-segregation characteristics, achieving a synergistic improvement in water reduction and anti-segregation effects, and achieving a balance of high performance.

[0053] 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 polycarboxylate superplasticizer, characterized in that, The polycarboxylate superplasticizer comprises a polymer backbone and several polyether side chains; the polymer backbone is formed by at least unsaturated carboxylic acid monomers and unsaturated sulfonic acid monomers through a free radical copolymerization reaction, and the polyether side chains are formed by click-modified polyether macromonomers connected to the polymer backbone through the free radical copolymerization reaction; the click-modified polyether macromonomer is generated by an alkynylated polyether macromonomer and an azido-hydroxyethyl acrylate through an azido-alkynyl cycloaddition reaction, and contains a triazole ring structure, and the click-modified polyether macromonomer is connected to the polymer backbone using structural units from the azido-hydroxyethyl acrylate and / or structural units from the alkynylated polyether macromonomer.

2. The polycarboxylate superplasticizer according to claim 1, characterized in that, The unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, methacrylic acid, and maleic anhydride; the unsaturated sulfonic acid monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium methylallyl sulfonate, styrene sulfonic acid, and vinyl sulfonic acid; the alkynylated polyether macromonomer is obtained by alkynylation modification of a polyether macromonomer selected from at least one of methylallyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, and ethylene glycol monovinyl polyethylene glycol ether; the azidolated hydroxyethyl acrylate is obtained by azido modification of hydroxyethyl acrylate.

3. The polycarboxylate superplasticizer according to claim 1, characterized in that, The molar ratio of the alkynylated polyether macromonomer to the azidolated hydroxyethyl acrylate is 1:(0.9~1.3); the molar ratio of the click-modified polyether macromonomer, the unsaturated carboxylic acid monomer, and the unsaturated sulfonic acid monomer is 1:(2.5~6):(0.2~0.8).

4. The method for preparing the polycarboxylate superplasticizer according to any one of claims 1 to 3, characterized in that, The method includes the following steps: S1, the polyether macromonomer was modified by alkynylation using an alkynylating agent to obtain an alkynylated polyether macromonomer; S2, hydroxyethyl acrylate is modified by azidation with an azide reagent to obtain azidated hydroxyethyl acrylate; S3, in the presence of a copper catalyst, the alkynylated polyether macromonomer obtained in step S1 and the azido-alkynylated hydroxyethyl acrylate obtained in step S2 undergo an azido-alkynyl cycloaddition reaction to obtain the click-modified polyether macromonomer. S4. The click-modified polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated sulfonic acid monomer obtained in step S3 are subjected to free radical copolymerization to obtain a polycarboxylic acid water-reducing agent composed of a polymer backbone and several polyether side chains.

5. The preparation method according to claim 4, characterized in that, The alkynylation modification in step S1 is carried out in the presence of a catalyst. The alkynylation reagent is selected from at least one of propargyl isocyanate and propargyl bromide. The catalyst is selected from at least one of dibutyltin dilaurate, bismuth neodecanoate, and tetrabutyl titanate. The molar ratio of the polyether macromonomer, catalyst, and alkynylation reagent is 1:(1.0~1.3):(0.001~0.005). Preferably, the conditions for the alkynylation modification include a temperature of 50°C to 70°C and a time of 2 to 5 hours.

6. The preparation method according to claim 4, characterized in that, The azide reagent in step S2 is selected from one of azide carboxylic acid ester, azide hydride, and azide sulfonyl hydride; the molar ratio of the hydroxyethyl acrylate, the azide reagent, and the polyether macromonomer in step S1 is (0.8~1.5):(0.9~1.4):1; Preferably, the conditions for the azidation modification include a temperature of 60℃~80℃ and a time of 3h~5h.

7. The preparation method according to claim 4, characterized in that, The copper catalyst in step S3 is a complex of cuprous ions and a ligand; preferably, the cuprous ion is cuprous chloride; preferably, the ligand is 2,2'-bipyridine; preferably, the molar ratio of the alkynylated polyether macromonomer, azidolated hydroxyethyl acrylate, cuprous ions, and ligand is 1:(0.9~1.3):(0.05~0.12):(0.1~0.24); Preferably, the conditions for the azide-alkyne cycloaddition reaction include a temperature of 20°C to 40°C and a time of 0.5 h to 5 h.

8. The water-reducing agent according to claim 4, characterized in that, The free radical copolymerization reaction described in step S4 is carried out in the presence of an initiator and a chain transfer agent. The initiator is a redox initiator, and the chain transfer agent is mercaptopropionic acid and / or mercaptoethanol. The molar ratio of the click-modified polyether macromonomer, unsaturated carboxylic acid monomer, unsaturated sulfonic acid monomer, initiator, and chain transfer agent is 1:(2.5~6):(0.2~0.8):(0.02~0.05):(0.015~0.03). Preferably, the conditions for the free radical polymerization reaction include a temperature of 60°C to 80°C and a time of 1 hour to 5 hours.

9. The application of the polycarboxylate superplasticizer according to any one of claims 1-3 in the construction field.

10. The application according to claim 9, characterized in that, The dosage of the polycarboxylate superplasticizer in concrete, based on the mass of its effective solid components, is 0.1% to 0.5% of the total mass of the concrete cementitious materials.

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