Early-strength quick-setting polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention relates to an early-strength quick-setting polycarboxylic acid water reducer and a preparation method and application thereof, and the early-strength quick-setting polycarboxylic acid water reducer is prepared from the following raw materials in parts by weight: 20-35 parts of unsaturated polyether monomer; 8 to 10 parts of acrylic acid-2-hydroxy-3-phenoxy propyl ester; 5 to 12 parts of N-hydroxyethylpiperazine-3-hydroxypropionate, and 5 to 12 parts of N-hydroxyethylpiperazine-3- 0.8 to 2.5 parts of an initiator; 0.3-1.2 parts of a chain transfer agent and water. Aiming at the problems of insufficient early-strength and quick-setting performance of a polycarboxylate superplasticizer, side effects of a compound early-strength agent, limited molecular structure adjustment effect, poor environmental protection property and the like in the prior art, the invention provides the early-strength and quick-setting polycarboxylate superplasticizer and the preparation method thereof. The initial setting time of the concrete is remarkably shortened, the early strength is greatly improved, meanwhile, it is guaranteed that the later strength of the concrete is not reduced, the working performance (slump loss rate) is good, the preparation process is environmentally friendly, and the cost is controllable.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, specifically to an early-strength, fast-setting polycarboxylate superplasticizer, its preparation method, and its application. Background Technology

[0002] Traditional polycarboxylate superplasticizers often incorporate early-strength agents such as chlorides, sulfates, and alkanolamines. For example, Chinese patent CN108586178A discloses a polycarboxylate superplasticizer compounded with calcium nitrate and triethanolamine. While this can shorten the initial setting time to 6-8 hours and increase the 1-day strength by 30%-40%, chlorides can cause steel corrosion (the risk of corrosion increases significantly when the Cl- content exceeds 0.1%), and sulfates can easily trigger sulfate erosion inside the concrete. Furthermore, the compounding amount is relatively large (usually 10%-20% of the superplasticizer's mass), which not only increases production costs but may also lead to accelerated slump loss in concrete (slump loss rate exceeds 30% within 60 minutes).

[0003] The early strength effect can be improved by changing the molecular backbone and side chain structure of polycarboxylate superplasticizers or by introducing early strength functional groups. For example, Chinese patent CN110255043A discloses a polycarboxylate superplasticizer with aminosulfonic acid groups introduced. However, its preparation process requires the use of highly toxic aminosulfonic acid ester raw materials, and the early strength effect is limited (the strength improvement in 1 day is only 40%-50%). At the same time, the slump retention performance is greatly reduced after the molecular structure is adjusted (the slump loss rate in 60 minutes is more than 40%).

[0004] Furthermore, in existing technologies, the preparation of polycarboxylate superplasticizers mostly adopts a free radical polymerization process at a single temperature. During the reaction, local overheating is prone to occur, leading to molecular chain aggregation and affecting the stability of product performance. Moreover, the raw materials used are mostly conventional unsaturated polyethers (such as isopentenyl alcohol polyoxyethylene ether and methyl allyl alcohol polyoxyethylene ether) and common carboxylic acids (such as acrylic acid and maleic anhydride), which have limited functions and are difficult to achieve the synergistic effect of early strength, rapid setting and slump retention at the same time.

[0005] Therefore, developing a high-strength, fast-setting polycarboxylate superplasticizer with special raw materials, advanced technology, and excellent performance has become the key to solving the current technical bottleneck. Summary of the Invention

[0006] Therefore, it is necessary to provide an early-strength, fast-setting polycarboxylate superplasticizer, its preparation method, and its application, in order to solve the technical problems existing in the prior art.

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

[0008] An early-strength, fast-setting polycarboxylate superplasticizer, wherein the raw materials for its preparation include, by weight parts:

[0009]

[0010] water.

[0011] Preferably, the unsaturated polyether monomer is isopentenyl alcohol polyoxyethylene ether with oxazolidinone end groups.

[0012] Preferably, the number average molecular weight of the isopentenyl alcohol polyoxyethylene ether with oxazolidinone end groups is 2000-3500, and the grafting rate of the oxazolidinone end groups in the isopentenyl alcohol polyoxyethylene ether is ≥85%.

[0013] Preferably, the initiator is a compound system of ammonium persulfate and azobisisobutyramidine hydrochloride, with a mass ratio of 1:(0.3-0.8). Specifically, the compound system of ammonium persulfate (water-soluble, highly reactive at high temperatures) and azobisisobutyramidine hydrochloride (water-soluble, stable initiation at medium and low temperatures) can maintain stable initiation throughout the 50-75℃ range, avoiding the problem of "slow initiation at low temperatures and easy rapid polymerization at high temperatures" associated with single initiators, and ensuring a uniform molecular weight distribution of the polymer (PDI = 1.2-1.5). In addition, the compound system will not undergo side reactions with oxazolidinone rings or heterocyclic alcoholamine esters.

[0014] Preferably, the chain transfer agent is mercaptoacetic acid-ethylene glycol monomethyl ether ester.

[0015] More specifically, the advantages of this patented chain transfer agent (thioglycolic acid-ethylene glycol monomethyl ether ester):

[0016] 1. Precise molecular weight adjustment, balancing polymerization activity: The chain transfer constant of its thiol (-SH) group matches the polymerization rate of this patent (modified polyether, carboxylic acid derivative), which can precisely control the weight-average molecular weight of the polymer between 15,000 and 30,000, ensuring water reduction rate while avoiding excessively large molecular weight that would affect the rapid setting effect; while the chain transfer constant of mercaptoethanol is too high, which easily leads to a smaller molecular weight (<10,000), resulting in a 10%-15% decrease in water reduction rate.

[0017] 2. Improve the slump retention performance of the product: The ethylene glycol monomethyl ether ester group (-OCH2CH2OCH3) in the molecular structure can form weak hydrogen bonds with cement hydration products, which helps to delay slump loss and make the slump loss rate ≤12% at 60 min, while when mercaptopropionic acid is used as a chain transfer agent, the loss rate is usually ≥18%.

[0018] 3. Odorless and environmentally friendly: Compared with the pungent odor of mercaptoethanol and dodecyl mercaptoethanol, this chain transfer agent leaves no residual odor after reaction and has better biodegradability, meeting the standards for green building materials.

[0019] Preferably, the raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer further include 1-3 parts by weight of pH adjuster.

[0020] Preferably, the pH adjuster is a compound system of triethanolamine and sodium bicarbonate, and the mass ratio of triethanolamine to sodium bicarbonate is 1:0.5-1.2.

[0021] A second aspect of this invention provides a method for preparing an early-strength, fast-setting polycarboxylate superplasticizer, comprising the steps of:

[0022] Unsaturated polyether monomers, a portion of the total initiator, and water are mixed to obtain a prepolymer solution;

[0023] Raise the temperature of the prepolymer solution to 65-70℃, and simultaneously add mixture A and mixture B dropwise. After the addition is complete, keep the mixture at 70℃-75℃ for 2-2.5 hours. Once the reaction is complete, the mixture is obtained.

[0024] Add N-hydroxyethylpiperazine-3-hydroxypropionate to the mixture, heat to 80℃-85℃, increase the stirring speed to 500-600r / min, and keep the reaction at this temperature for 1.5-2h to obtain the early-strength, fast-setting polycarboxylate superplasticizer.

[0025] Preferably, the dropping rate of mixture A is 0.8 mL / min-1.2 mL / min, and the dropping rate of mixture B is 0.5 mL / min-0.8 mL / min.

[0026] More specifically, the specific steps for preparing the early-strength, fast-setting polycarboxylate superplasticizer are as follows:

[0027] (1) Raw material pretreatment:

[0028] The unsaturated polyether monomer was placed in a vacuum drying oven and dried at 80-90℃ and a vacuum of -0.08 to -0.09 MPa for 4-6 hours to remove moisture, ensuring that the moisture content was ≤0.1%, thus obtaining the pretreated unsaturated polyether monomer.

[0029] 2-hydroxy-3-phenoxypropyl acrylate was purified by silica gel column chromatography with a mixture of ethyl acetate and petroleum ether as eluent (volume ratio 1:3-5). The fraction with a purity ≥98% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0030] (2) Prepolymerization reaction:

[0031] Add deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel, and nitrogen protection device, heat to 50-55℃, and purge with nitrogen for 30-45 minutes to remove air; then add the pretreated unsaturated polyether monomer, stir until completely dissolved, and control the stirring speed at 300-400 r / min; next, add 40%-50% of the total initiator dropwise over 30-45 minutes, and keep the reaction at the temperature for 1-1.5 hours to obtain the prepolymer solution.

[0032] (3) Copolymerization:

[0033] Raise the temperature of the prepolymer solution to 65-70℃, and simultaneously add two mixtures: Mixture A is a mixture of 2-hydroxy-3-phenoxypropyl acrylate and chain transfer agent, with a dropping time of 60-90 min; Mixture B is a mixture of the remaining initiator and deionized water (mass ratio 1:5-8), with a dropping time of 70-100 min; the starting time of adding mixture B is delayed by 10-15 min compared to mixture A to ensure that the dropping processes of the two liquids overlap; after the dropping is completed, maintain the reaction at 70-75℃ for 2-2.5 h.

[0034] (4) Functional group grafting:

[0035] Add N-hydroxyethylpiperazine-3-hydroxypropionate to the reaction vessel, heat to 80-85℃, increase the stirring speed to 500-600 r / min, and keep the reaction at this temperature for 1.5-2 h to allow the active groups in the heterocyclic alcoholamine ester to undergo a grafting reaction with the polymer backbone.

[0036] (5) Post-processing:

[0037] Cool to 40-45℃, add pH adjuster to adjust the pH value of the system to 6.5-7.5, stir for 30-40 minutes; then filter with a 0.22μm microporous membrane to remove unreacted impurities, and obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 30%-40%.

[0038] Preferably, the nitrogen gas introduction rate in step (2) is 0.5-1 L / min.

[0039] Preferably, in step (5), the filtration is performed by pressure filtration with a filtration pressure of 0.3-0.5 MPa to ensure filtration efficiency and filtrate purity.

[0040] Preferably, the water-reducing agent is added to the concrete at a dosage of 1.0%-1.5% of the total mass of the cementitious materials.

[0041] The third aspect of the present invention provides an application of an early-strength, fast-setting polycarboxylate superplasticizer in concrete, wherein the dosage of the early-strength, fast-setting polycarboxylate superplasticizer in concrete is 1.0%-1.5% of the total mass of cementitious materials.

[0042] The beneficial effects of this invention are:

[0043] (1) This invention achieves a slump loss rate of concrete of ≤10% in 60 min through the synergistic effect of “phenoxy steric hindrance + oxazolidinone cyclic polar adsorption”.

[0044] The phenoxy group in 2-hydroxy-3-phenoxypropyl acrylate can form a steric barrier, delaying the flocculation of cement particles;

[0045] Simultaneously, the oxazolidinone ring interacts with the Ca on the surface of cement particles. 2+ Its strong adsorption effect prevents water-reducing agent molecules from desorbing prematurely, ensuring that concrete maintains good fluidity throughout transportation and pouring, eliminating the need for additional slump retainers and reducing compounding costs.

[0046] (2) The hydroxyl group (-OH) in 2-hydroxy-3-phenoxypropyl acrylate can form hydrogen bonds with the Si-OH group in hydrated calcium silicate gel, which accelerates the cross-linking and curing of the gel network and shortens the strength development cycle.

[0047] The steric hindrance effect of phenoxy (-C6H5O-) in 2-hydroxy-3-phenoxypropyl acrylate can regulate the flocculation rate of cement particles and avoid the increase in internal porosity caused by excessively rapid hydration.

[0048] Meanwhile, grafting with the heterocyclic alcoholamine ester N-hydroxyethylpiperazine-3-hydroxypropionate further optimizes the early strength performance—piperazine heterocycles can chelate Fe in cement. 3+ (Fe3+) and (aluminum3+) promote the formation of early strength minerals such as calcium aluminate hydrate, while hydroxyethyl (-CH2CH2OH) and hydroxypropionate groups (-OCH2CH(OH)COOH) can delay the excessive growth of Ca(OH)2 (calcium hydroxide) crystals and reduce defects in the interface transition zone.

[0049] This "multi-group synergistic grafting" molecular design enables concrete to maintain efficient early strength even in low-temperature (-5℃) environments, with a 1-day compressive strength of 18-22MPa and an initial setting time controlled at 6-7.5h. It solves the technical pain point of "early strength failure" of traditional polyether water-reducing agents at low temperatures and is suitable for extreme scenarios such as winter construction in northern regions. Detailed Implementation

[0050] 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.

[0051] 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.

[0052] Example 1:

[0053] (1) Raw material pretreatment:

[0054] The unsaturated polyether monomer was dried at 85°C and a vacuum of -0.085 MPa for 5 hours to ensure that the moisture content was ≤0.1%, thus obtaining the pretreated unsaturated polyether monomer.

[0055] 2-Hydroxy-3-phenoxypropyl acrylate was purified with an eluent, and the fraction with a purity of 98.5% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0056] (2) Prepolymerization reaction:

[0057] Add 80 parts by weight of deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel and nitrogen protection device, heat to 52°C and purge with nitrogen for 40 min; add pretreated unsaturated polyether monomer, stir at 350 r / min until dissolved; add 50% of initiator mixture dropwise, after 40 min of dropwise addition, keep at 52°C for 1.2 h to obtain prepolymer solution;

[0058] (3) Copolymerization:

[0059] The prepolymer solution was heated to 68°C, and mixture A was added dropwise over 75 min. Mixture B was added dropwise with a delay of 12 min over 85 min. The mixture was then kept at 72°C for 2.2 h.

[0060] (4) Functional grafting:

[0061] N-hydroxyethylpiperazine-3-hydroxypropionate was added to the reactor, the temperature was raised to 82°C, the stirring speed was increased to 550 r / min, and the reaction was maintained at this temperature for 1.8 h to allow the active groups in the heterocyclic alcoholamine ester to undergo a grafting reaction with the polymer backbone.

[0062] (5) Post-processing:

[0063] The solution was cooled to 42°C, and the pH was adjusted to 7.0 using a pH adjuster. The solution was stirred for 35 minutes. Subsequently, it was filtered through a 0.22 μm filter membrane to obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 39.56%.

[0064] The unsaturated polyether monomer is an oxazolidinone with a number average molecular weight of 2500 and a grafting rate of 88%; the eluent is a mixture of ethyl acetate and petroleum ether in a mass ratio of 1:4.

[0065] The initiator is a mixture of ammonium persulfate and azobisisobutyramidine hydrochloride in a mass ratio of 1:0.5.

[0066] Mixture A is a mixed solution of 2-hydroxy-3-phenoxypropyl acrylate and mercaptoacetic acid-ethylene glycol monomethyl ether ester;

[0067] Mixture B is a mixture of the remaining 50% initiator and water, with an initiator to water ratio of 1:6.

[0068] The pH adjuster is a mixture of triethanolamine and sodium bicarbonate in a mass ratio of 1:0.8.

[0069] The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

[0070]

[0071] Example 2:

[0072] (1) Raw material pretreatment:

[0073] The unsaturated polyether monomer was dried at 80°C and a vacuum of -0.08 MPa for 4 hours to ensure that the moisture content was ≤0.1%, thus obtaining the pretreated unsaturated polyether monomer.

[0074] 2-Hydroxy-3-phenoxypropyl acrylate was purified with an eluent, and the fraction with a purity of 98.5% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0075] (2) Prepolymerization reaction:

[0076] Add 100 parts by weight of deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel and nitrogen protection device, heat to 50°C and purge with nitrogen for 30 min; add pretreated unsaturated polyether monomer and stir at 300 r / min until dissolved; add 50% of the initiator mixture dropwise for 30 min, and then keep at 52°C for 1 h to obtain the prepolymer solution.

[0077] (3) Copolymerization:

[0078] The prepolymer solution was heated to 65°C, and mixture A was added dropwise over 60 min. Mixture B was added dropwise with a delay of 12 min over 70 min. The mixture was then kept at 72°C for 2 h.

[0079] (4) Functional grafting:

[0080] N-hydroxyethylpiperazine-3-hydroxypropionate was added to the reactor, the temperature was raised to 80°C, the stirring speed was increased to 500 r / min, and the reaction was maintained at this temperature for 1.5 h to allow the active groups in the heterocyclic alcoholamine ester to undergo a grafting reaction with the polymer backbone.

[0081] (5) Post-processing:

[0082] The solution was cooled to 40°C, and the pH was adjusted to 7.0 using a pH adjuster. The solution was stirred for 30 minutes. Then, it was filtered through a 0.22μm filter membrane to obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 40.05%.

[0083] Among them, the unsaturated polyether monomer is an oxazolidinone with a number average molecular weight of 2500 and a grafting rate of 88%.

[0084] The eluent is a mixture of ethyl acetate and petroleum ether in a mass ratio of 1:5;

[0085] The initiator is a mixture of ammonium persulfate and azobisisobutyramidine hydrochloride in a mass ratio of 1:0.5.

[0086] Mixture A is a mixed solution of 2-hydroxy-3-phenoxypropyl acrylate and mercaptoacetic acid-ethylene glycol monomethyl ether ester;

[0087] Mixture B is a mixture of the remaining 50% initiator and water, with an initiator to water ratio of 1:6.

[0088] The pH adjuster is a mixture of triethanolamine and sodium bicarbonate in a mass ratio of 1:0.8.

[0089] The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

[0090]

[0091]

[0092] Example 3:

[0093] (1) Raw material pretreatment:

[0094] The unsaturated polyether monomer was dried at 90°C and a vacuum of -0.09 MPa for 6 hours to ensure that the moisture content was ≤0.1%, thus obtaining the pretreated unsaturated polyether monomer.

[0095] 2-Hydroxy-3-phenoxypropyl acrylate was purified with an eluent, and the fraction with a purity of 99% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0096] (2) Prepolymerization reaction:

[0097] Add 80 parts by weight of deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel and nitrogen protection device, heat to 55°C and purge with nitrogen for 45 min; add pretreated unsaturated polyether monomer, stir at 400 r / min until dissolved; add 50% of initiator mixture dropwise, after 45 min of dropwise addition, keep at 52°C for 1.5 h to obtain prepolymer solution;

[0098] (3) Copolymerization:

[0099] The prepolymer solution was heated to 70°C, and mixture A was added dropwise over 90 min. Mixture B was added dropwise with a delay of 12 min over 100 min. The mixture was then kept at 75°C for 2.5 h.

[0100] (4) Functional grafting:

[0101] N-hydroxyethylpiperazine-3-hydroxypropionate was added to the reactor, the temperature was raised to 85°C, the stirring speed was increased to 600 r / min, and the reaction was maintained at this temperature for 2 h to allow the active groups in the heterocyclic alcoholamine ester to undergo a grafting reaction with the polymer backbone.

[0102] (5) Post-processing:

[0103] The temperature was lowered to 40℃, the pH was adjusted to 6.8 with a pH adjuster, and the mixture was stirred for 40 minutes. Then, it was filtered through a 0.22μm filter membrane to obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 40.34%.

[0104] Among them, the unsaturated polyether monomer is an oxazolidinone with a number average molecular weight of 2500 and a grafting rate of 88%.

[0105] The eluent is a mixture of ethyl acetate and petroleum ether in a mass ratio of 1:5;

[0106] The initiator is a mixture of ammonium persulfate and azobisisobutyramidine hydrochloride in a mass ratio of 1:0.5.

[0107] Mixture A is a mixed solution of 2-hydroxy-3-phenoxypropyl acrylate and mercaptoacetic acid-ethylene glycol monomethyl ether ester;

[0108] Mixture B is a mixture of the remaining 50% initiator and water, with an initiator to water ratio of 1:6.

[0109] The pH adjuster is a mixture of triethanolamine and sodium bicarbonate in a mass ratio of 1:0.8.

[0110] The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

[0111]

[0112] Example 4:

[0113] (1) Raw material pretreatment:

[0114] The unsaturated polyether monomer was dried at 85°C and under a vacuum of -0.08 MPa for 5 hours to ensure that the moisture content was ≤0.1%, thus obtaining the pretreated unsaturated polyether monomer.

[0115] 2-Hydroxy-3-phenoxypropyl acrylate was purified with an eluent, and the fraction with a purity of 98.5% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0116] (2) Prepolymerization reaction:

[0117] Add 85 parts by weight of deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel and nitrogen protection device, heat to 53°C and purge with nitrogen for 40 min; add pretreated unsaturated polyether monomer and stir at 350 r / min until dissolved; add 50% of the initiator mixture dropwise for 40 min, and then keep at 52°C for 1.3 h to obtain the prepolymer solution.

[0118] (3) Copolymerization:

[0119] The prepolymer solution was heated to 67°C, and mixture A was added dropwise over 80 min. Mixture B was added dropwise with a delay of 12 min over 90 min. The mixture was then kept at 73°C for 2.3 h.

[0120] (4) Functional grafting:

[0121] N-hydroxyethylpiperazine-3-hydroxypropionate was added to the reactor, the temperature was raised to 83°C, the stirring speed was increased to 550 r / min, and the reaction was maintained at this temperature for 1.7 h. At the same time, 0.5% of low temperature stabilizer (ethylene glycol monomethyl ether) was added to improve the low temperature fluidity, so that the active groups in the heterocyclic alcoholamine ester could undergo a grafting reaction with the polymer backbone.

[0122] (5) Post-processing:

[0123] The solution was cooled to 40°C, and the pH was adjusted to 7.2 with a pH adjuster. The solution was stirred for 30 minutes. Then, it was filtered through a 0.22μm filter membrane to obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 39.77%.

[0124] Among them, the unsaturated polyether monomer is an oxazolidinone with a number average molecular weight of 3000 and a grafting rate of 88%.

[0125] The eluent is a mixture of ethyl acetate and petroleum ether in a mass ratio of 1:3;

[0126] The initiator is a mixture of ammonium persulfate and azobisisobutyramidine hydrochloride in a mass ratio of 1:0.5.

[0127] Mixture A is a mixed solution of 2-hydroxy-3-phenoxypropyl acrylate and mercaptoacetic acid-ethylene glycol monomethyl ether ester;

[0128] Mixture B is a mixture of the remaining 50% initiator and water, with an initiator to water ratio of 1:6.

[0129] The pH adjuster is a mixture of triethanolamine and sodium bicarbonate in a mass ratio of 1:0.8.

[0130] The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

[0131]

[0132] Example 5:

[0133] (1) Raw material pretreatment:

[0134] The unsaturated polyether monomer was dried at 85°C and a vacuum of -0.08 MPa for 5 hours to obtain the pretreated unsaturated polyether monomer.

[0135] 2-Hydroxy-3-phenoxypropyl acrylate was purified with an eluent, and the fraction with a purity of 98.5% was collected to obtain pretreated 2-hydroxy-3-phenoxypropyl acrylate.

[0136] (2) Prepolymerization reaction:

[0137] Add 95 parts by weight of deionized water to a reactor equipped with a high-efficiency stirrer, thermometer, dropping funnel and nitrogen protection device, heat to 54°C and purge with nitrogen for 40 min; add pretreated unsaturated polyether monomer, stir at 350 r / min until dissolved; add 50% of the initiator mixture dropwise, and after 40 min of dropwise addition, keep at 52°C for 1.4 h to obtain the prepolymer solution;

[0138] (3) Copolymerization:

[0139] The prepolymer solution was heated to 69°C, and mixture A was added dropwise over 85 min. Mixture B was added dropwise with a delay of 12 min over 95 min. The mixture was then kept at 74°C for 2.4 h.

[0140] (4) Functional grafting:

[0141] N-hydroxyethylpiperazine-3-hydroxypropionate was added to the reactor, the temperature was raised to 82°C, the stirring speed was increased to 550 r / min, and the reaction was maintained at this temperature for 1.8 h to allow the active groups in the heterocyclic alcoholamine ester to undergo a grafting reaction with the polymer backbone.

[0142] (5) Post-processing:

[0143] The solution was cooled to 40°C, and the pH was adjusted to 7.0 using a pH adjuster. The solution was stirred for 30 minutes. Then, it was filtered through a 0.22μm filter membrane to obtain an early-strength, fast-setting polycarboxylate superplasticizer with a solid content of 40.05%.

[0144] Among them, the unsaturated polyether monomer is an oxazolidinone with a number average molecular weight of 2800 and a grafting rate of 88%.

[0145] The eluent is a mixture of ethyl acetate and petroleum ether in a mass ratio of 1:5;

[0146] The initiator is a mixture of ammonium persulfate and azobisisobutyramidine hydrochloride in a mass ratio of 1:0.5.

[0147] Mixture A is a mixed solution of 2-hydroxy-3-phenoxypropyl acrylate and mercaptoacetic acid-ethylene glycol monomethyl ether ester;

[0148] Mixture B is a mixture of the remaining 50% initiator and water, with an initiator to water ratio of 1:6.

[0149] The pH adjuster is a mixture of triethanolamine and sodium bicarbonate in a mass ratio of 1:0.8.

[0150] The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

[0151]

[0152] Comparative Example 1: Traditional ordinary polyether water-reducing agent (without oxazolidinone modification)

[0153] This comparative example is a control group for traditional technology. The core difference is the absence of oxazolidinone modification. The raw material amounts correspond to those in Example 1: 28 parts of ordinary isopentenyl polyoxyethylene ether (number average molecular weight 2500, no oxazolidinone groups), 12 parts of ordinary acrylic acid (no hydroxyl and phenoxy groups), 8 parts of ordinary triethanolamine (no heterocyclic and propionate groups), only 1.5 parts of ammonium persulfate (no azo components) as the initiator, mixture A consists of 2-hydroxy-3-phenoxypropyl acrylate and only 0.7 parts of mercaptoacetic acid, 50 parts of deionized water, and only 2 parts of triethanolamine as the pH adjuster.

[0154] The process involves no segmented temperature control; polymerization occurs only at a single temperature of 65°C, with the mixed solution added dropwise simultaneously (without delay).

[0155] Comparative Example 2: 2-Hydroxy-3-phenoxypropyl acrylate missing (replaced with regular acrylic acid)

[0156] This comparative example verifies the necessity of the special 2-hydroxy-3-phenoxypropyl acrylate. Except for replacing "2-hydroxy-3-phenoxypropyl acrylate" with an equal amount of ordinary acrylic acid (without hydroxyl and phenoxy groups), the amounts and process parameters of the other raw materials (modified polyether, heterocyclic alcoholamine esters, etc.) are completely consistent with those in Example 1.

[0157] Comparative Example 3: N-hydroxyethylpiperazine-3-hydroxypropionate missing (replaced with common triethanolamine)

[0158] This comparative example verifies the role of heterocyclic alcoholamine esters. The raw material "N-hydroxyethylpiperazine-3-hydroxypropionate" was replaced with an equal amount of ordinary triethanolamine, and the remaining raw materials and process parameters were the same as in Example 1.

[0159] Comparative Example 4: Comparison with patented technology (CN202411969864.4, ester-type early strength water-reducing agent)

[0160] This comparative example uses the disclosed scheme of the patent (Tongji University ester-type early strength water-reducing agent). The raw materials are: 25 parts of low molecular weight polycarboxylic acid (acrylic acid, molecular weight 3000), 15 parts of polyether-based glycidyl ether, 2.0 parts of initiator potassium persulfate, 55 parts of deionized water, 3 parts of pH adjuster sodium hydroxide, and oxazolidinone-free modified polyether and special carboxylic acid derivatives.

[0161] The process is a patented two-step method: polymerization at 60℃ followed by esterification at 80℃, without segmented temperature control or delayed drop addition.

[0162] Comparative Example 5: Comparison with patented technology (CN119191744B, nano-composite water-reducing agent)

[0163] This comparative example uses the patented (Huzhou Green New Materials Nanocomposite Water Reducing Agent) scheme. The raw materials are: 28 parts of ordinary polyether macromonomer (molecular weight 2500, without oxazolidinone modification), 12 parts of acrylic acid, 5 parts of calcium nitrate (nano precursor), 3 parts of sodium silicate (nano precursor), 1.2 parts of initiator (composite of vitamin C and sodium persulfate), 50 parts of deionized water, and 2 parts of pH adjuster (ammonia water).

[0164] The process is the low-temperature method of this invention: polymerization at 25℃ followed by nanocomposite processing at 0-10℃.

[0165] The early-strength, fast-setting polycarboxylate superplasticizers provided in Examples 1-5 of this invention and the polycarboxylate superplasticizers provided in Comparative Examples 1-5, after being folded to the same solid content, were mixed into concrete, and their performance was compared by testing at the same dosage in different temperature environments.

[0166] The concrete mix proportions are shown in Table 1.

[0167] Table 1 Concrete Mix Proportion Table (kg / m³) 3 )

[0168]

[0169] Performance tests were conducted under the same conditions on concrete mixtures containing the water-reducing agents described in Examples 1-5 and Comparative Examples 1-5 of this invention, respectively, in accordance with GB / T8076-2008 Concrete Admixtures.

[0170] The admixture dosage was 1.2%. The mechanical properties of the concrete mixtures with the water-reducing agents described in Examples 1 to 5 and Comparative Examples 1 to 5 of this invention were tested according to the GB / T50081-2002 standard for mechanical properties of ordinary concrete. The concrete test results are shown in Table 2.

[0171] Table 2 Concrete Test Results

[0172]

[0173] As shown in Table 2, the early-strength, fast-setting polycarboxylate superplasticizer prepared by this invention has the following specific properties:

[0174] 1. Early strength and rapid setting performance: The 1-day compressive strength (22-28MPa) of Examples 1-5 was significantly improved compared with Comparative Example 1 (12MPa), Comparative Example 4 (18MPa), and Comparative Example 5 (15MPa), and the initial setting time (3.5-7.0h) was significantly shortened compared with the comparative example group (4.1-13.2h), which reflects the synergistic effect of oxazolidinone group and special components;

[0175] 2. Slump retention balance performance: The slump loss rate (8%-12%) of the Example Group at 60 min was much lower than that of Comparative Example 2 (22%) and Comparative Example 4 (23%), which proves that the steric hindrance effect of phenoxy group of 2-hydroxy-3-phenoxypropyl acrylate can effectively balance early strength and slump retention.

[0176] 3. Environmental adaptability: At low temperature (-5℃), the initial setting time (7.0h) and 1d compressive strength (20MPa) of Example 4 are significantly better than those of Comparative Example 5 (9.5h, 15MPa), highlighting the low temperature adaptability of this patented technology; in high admixture scenarios, Example 5 still maintains excellent performance and is suitable for engineering cost optimization needs.

[0177] 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 rapid-setting, high-strength polycarboxylate superplasticizer, characterized in that, The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer, by weight, include:

2. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 1, characterized in that, The unsaturated polyether monomer is isopentenyl alcohol polyoxyethylene ether with oxazolidinone end groups.

3. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 2, characterized in that, The number average molecular weight of the isopentenyl alcohol polyoxyethylene ether with oxazolidinone terminal groups is 2000-3500, and the grafting rate of the oxazolidinone groups in the isopentenyl alcohol polyoxyethylene ether with oxazolidinone terminal groups is ≥85%.

4. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 1, characterized in that, The initiator is a compound system of ammonium persulfate and azobisisobutyramidine hydrochloride, with a mass ratio of 1:(0.3-0.8).

5. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 1, characterized in that, The chain transfer agent is mercaptoacetic acid-ethylene glycol monomethyl ether ester.

6. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 1, characterized in that, The raw materials for preparing the early-strength, fast-setting polycarboxylate superplasticizer also include 1-3 parts by weight of pH adjuster.

7. The early-strength, rapid-setting polycarboxylate superplasticizer according to claim 6, characterized in that, The pH adjuster is a compound system of triethanolamine and sodium bicarbonate, with a mass ratio of triethanolamine to sodium bicarbonate of 1:(0.5-1.2).

8. A method for preparing an early-strength, fast-setting polycarboxylate superplasticizer as described in any one of claims 1-7, characterized in that, Including the following steps: Unsaturated polyether monomers, a portion of the total initiator, and water are mixed to obtain a prepolymer solution; Raise the temperature of the prepolymer solution to 65-70℃, and simultaneously add mixture A and mixture B dropwise. After the addition is complete, keep the mixture at 70℃-75℃ for 2-2.5 hours. Once the reaction is complete, the mixture is obtained. Add N-hydroxyethylpiperazine-3-hydroxypropionate to the mixture, heat to 80℃-85℃, increase the stirring speed to 500-600r / min, and keep the reaction at this temperature for 1.5-2h to obtain the early-strength, fast-setting polycarboxylate superplasticizer.

9. The preparation method according to claim 8, characterized in that, The dropping rate of mixture A is 0.8 mL / min-1.2 mL / min, and the dropping rate of mixture B is 0.5 mL / min-0.8 mL / min.

10. An application of the early-strength, rapid-setting polycarboxylate superplasticizer as described in any one of claims 1-7 in concrete, characterized in that, The dosage of the early-strength, fast-setting polycarboxylate superplasticizer in concrete is 1.0%-1.5% of the total mass of cementitious materials.

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