A fast-dispersible polycarboxylate water reducer and its preparation method

Abstract

The present invention relates to the technical field of concrete admixtures, and particularly relates to a rapid-dispersing polycarboxylate water reducer and a preparation method thereof. The water reducer is copolymerized from an acetyl-capped polyether macromonomer, acrylic acid, an ester macromonomer and functional monomer C through a copolymerization reaction. The rapid-dispersing polycarboxylate water reducer prepared by using a specific acetyl-capped polyether macromonomer in the present invention has a significantly improved adsorption rate and early adsorption amount on the surface of cement particles, and the later adsorption amount of the water reducer can be maintained at a relatively high level. The net paste dispersion time of the cement using this water reducer is short, and less of this water reducer is required to meet the same initial net paste fluidity requirement. This water reducer has a fast dispersion speed, good dispersion performance and good slump retention performance at low temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a fast-dispersing polycarboxylate water reducer and a preparation method thereof. Background Art

[0002] As the latest generation of concrete admixtures, polycarboxylate water reducers have high water reduction rate, strong slump retention ability, and are green and pollution-free in the production process. Due to the strong adjustable molecular structure of polycarboxylate water reducers, different monomer compositions and polymerization processes can prepare products with different properties, and they have great potential for high performance. They have become the most effective, economical, and simple technical approach to achieve high durability and performance improvement of concrete.

[0003] The molecular chain of polycarboxylate water reducer is relatively long and curls in the cement solution, and the adsorption groups are partially coated and cannot quickly exert the adsorption ability, resulting in a slow dispersion speed of polycarboxylate water reducer in low-temperature environments, causing low production efficiency of concrete and the phenomenon of reverse growth of fluidity in the later stage, which affects the quality of concrete projects. Moreover, polycarboxylate water reducers are adsorbed more by cement particles in the early stage, which easily causes insufficient water reducer to be adsorbed in the later stage, resulting in poor slump retention performance. Therefore, through molecular structure design, it is of great significance to develop a water reducer that can quickly adsorb cement particles, improve the dispersion performance of cement particles, and has good slump retention performance under low-temperature conditions.

[0004] The Chinese patent application with the publication number CN 115215972A discloses a preparation method of a fast-dispersing polycarboxylate water reducer. After the epoxy group of glycidyl ether is ring-opening polymerized by the hydroxyl group at the end of the polyether macromonomer, the in-situ generated terminal hyperbranched polyethylene glycol macromolecule is obtained. After the terminal reactive hydroxyl group of the terminal hyperbranched polyether is converted into a carboxyl adsorption group, it is copolymerized with a carboxylic acid small monomer to obtain the fast-dispersing polycarboxylate water reducer. Organic solvents are used in the preparation process of the polyether macromonomer, which not only has high cost but also pollutes the environment, and the prepared water reducer only has good dispersion performance at room temperature.

[0005] The Chinese invention patent with the patent publication number CN 113736036B discloses a multi-arm polycarboxylate water reducer and a preparation method thereof, which halogenates the end of the unsaturated polyether macromonomer, but the steps for preparing the polyether macromonomer are relatively complex, and the polycarboxylate water reducer prepared by using this kind of polyether macromonomer mainly has an improvement in shrinkage reduction performance.

[0006] The Chinese invention patent with the patent announcement number CN104371081 B discloses a preparation method of a fast-dispersing and viscosity-reducing polycarboxylate cement dispersant. It uses a self-made unsaturated macromonomer containing a tertiary amino group as a reducing agent that can participate in polymerization. The weight-average molecular weight of the dispersant is controlled within 20,000 - 100,000. However, the self-made tertiary amino unsaturated monomer is prepared through transesterification, using toluene as a solvent, which has the characteristic of being environmentally unfriendly.

[0007] The Chinese invention patent with the patent announcement number CN112707674 B discloses a high-adsorption and dispersing polycarboxylate water reducer and its preparation method. It uses a modified polyether macromonomer, an esterifying monomer, an alkoxysilane monomer, an unsaturated acid, graphene oxide, an initiator, a chain transfer agent, and a neutralizing agent. The high-adsorption and dispersing polycarboxylate water reducer provided by the present invention has good adsorption and dispersing properties, can promote the formation of a stable adsorption layer on the surface of cement particles in the cement paste, and can continuously release carboxyl groups and silanol groups during the cement hydration process, with the strongest effect on the adsorption ability of cement particles. However, there is no relevant research on the adsorption speed at low temperatures.

[0008] The Chinese invention patent application with the publication number CN116376004 A discloses a polyether compound, its preparation method, and its application in a slump-retaining agent. It uses monomethyl allyl ethylene glycol ether or propylene glycol monoallyl ether as the starting material, and under the action of catalyst I, ethylene oxide and / or propylene oxide are introduced under anaerobic conditions and heated for polymerization reaction. After the reaction is completed, propylene glycol is further introduced for polymerization reaction for capping. And a water-retaining and slurry-raising type concrete slump-retaining agent is designed and synthesized using this polyether compound. This slump-retaining agent can achieve long-term slump retention without loss for 4 hours, and there is no bleeding and late return to large phenomenon during the process, with the functions of water retention and slurry raising, and good workability. However, there is no mention of its fast-dispersing performance at low temperatures. Summary of the Invention

[0009] To solve the problems of the existing polycarboxylate water reducers mentioned in the above background technology: their dispersing speed is relatively slow in low-temperature environments, resulting in low concrete production efficiency and the phenomenon of reverse growth of later fluidity, affecting the quality of concrete projects. Moreover, the existing polycarboxylate water reducers are adsorbed more by cement particles in the early stage, which easily causes insufficient water reducers to be adsorbed later, leading to poor slump retention performance. The present invention provides a fast-dispersing polycarboxylate water reducer, and its technical solution is as follows:

[0010] The present invention provides a fast-dispersing polycarboxylate water reducer, which is copolymerized from an acetyl-capped polyether macromonomer, acrylic acid, an ester macromonomer, and functional monomer C through a copolymerization reaction;

[0011] The acetyl-capped polyether macromonomer is characterized in that its structural formula is as follows:

[0012]

[0013] Wherein, R is an alkylene group with 4 carbon atoms, M is an alkylene group with 2 carbon atoms; Y is a polyether chain prepared by polymerizing ethylene oxide; the B group is a group formed by the cleavage and ring-opening of the carbon-oxygen bond of the epoxy group of the acetyl-capped monomer;

[0014] The structural formula of the acetyl-capped monomer is:

[0015]

[0016] R1 and R2 are H or CH3.

[0017] In one embodiment, the acetyl-capped monomer is one of 2-acetyl ethylene oxide and 2-acetyl-2-methyl ethylene oxide; Y represents a polyether chain with the structure of (A) X wherein A is a repeating unit of polyoxyethylene and X is an integer from 1 to 100.

[0018] In one embodiment, the weight-average molecular weight of the acetyl-capped polyether macromonomer is 600 - 6000.

[0019] In one embodiment, the preparation process of the acetyl-capped polyether macromonomer is as follows: under the action of a catalyst, the initiator unsaturated alcohol and ethylene oxide undergo a ring-opening polymerization reaction to generate a polyether intermediate; the polyether intermediate undergoes a ring-opening reaction with the acetyl-capped monomer to obtain the acetyl-capped polyether macromonomer; wherein, the unsaturated alcohol is 2-(4-vinyloxybutoxy)ethanol; the structural formula of the polyether intermediate is as follows:

[0020] H2C=CH-O-R-O-M-O-Y-H;

[0021] The acetyl-capped monomer is one or a combination of 2-acetyl ethylene oxide and 2-acetyl-2-methyl ethylene oxide.

[0022] In one embodiment, the molar ratio of the acetyl-capped monomer to the polyether intermediate is (1 - 1.3):1; the reaction temperature of the ring-opening polymerization reaction is 100 - 120 °C, the reaction pressure is 0.3 - 0.6 MPa, and the reaction end point is that the pressure of the reaction system no longer decreases; the reaction temperature of the ring-opening reaction is 100 - 120 °C, the reaction pressure is 0.2 - 1.2 MPa, and the reaction time is (1 - 3) h.

[0023] In one embodiment, the catalyst is one or a combination of sodium hydroxide, potassium hydroxide, lithium aluminum hydride, and sodium metal.

[0024] In one embodiment, the structural formula of the functional monomer C is as follows:

[0025]

[0026] Wherein, R3, R4, and R5 are CH3, R6 and R7 are H or CH3, m, n, and p are integers from 0 to 3; a and b are integers from 0 to 2;

[0027] The ester macromonomer is one of polyethylene glycol methoxy ether monomethacrylate, polyethylene glycol monoacrylate, polyethylene glycol methoxy ether monoacrylate, and polyethylene glycol monomethacrylate.

[0028] In one embodiment, the functional monomer C is one or a combination of more than one of trimethylsilyl dimethacrylate, trimethylsilyl methacrylate, tributylsilyl 2-methyl-2-acrylate, (2E)-3-{4-[(trimethylsilyl)oxy]phenyl} acrylate trimethylsilyl ester, and (2E)-3-{3-[(trimethylsilyl)oxy]phenyl} acrylate trimethylsilyl ester; the molecular weight of the ester macromonomer is 600 - 3000.

[0029] In one embodiment, the mass ratio of the acetyl - terminated polyether macromonomer, the ester macromonomer, acrylic acid, and the functional monomer C is 70:30:(6 - 13):(0.5 - 2); the copolymerization reaction is carried out at room temperature, and the reaction time is 50 - 70 min.

[0030] The present invention also provides a preparation method of the rapid - dispersing polycarboxylate water - reducing agent as described above, which includes the following steps: adding the acetyl - terminated polyether macromonomer, the ester macromonomer, and a solvent into a reaction vessel for mixing, then respectively adding an oxidant solution, a reducing agent solution, a chain transfer agent solution, acrylic acid, and a functional monomer C solution, and carrying out a copolymerization reaction at room temperature for 50 - 70 min; after the reaction is completed, keeping warm for a period of time, and adding liquid alkali to adjust the pH to 6 - 7, thus obtaining the rapid - dispersing polycarboxylate water - reducing agent.

[0031] In one embodiment, the dosage of the oxidant is 0.5% - 3% of the total mass of the acetyl - terminated polyether macromonomer and the ester macromonomer; the dosage of the reducing agent is 0.5% - 3% of the total mass of the acetyl - terminated polyether macromonomer and the ester macromonomer; the dosage of the chain transfer agent is 0.5% - 1.5% of the total mass of the acetyl - terminated polyether macromonomer and the ester macromonomer.

[0032] In one embodiment, the oxidant is one or a combination of cumene hydroperoxide, hydrogen peroxide, and tert-butyl hydroperoxide; the reducing agent is one or a combination of sodium hypophosphite, ascorbic acid, disodium 2-hydroxy-2-sulfonatoacetate, and disodium 2-hydroxy-2-sulfinatoacetate; the chain transfer agent is one or a combination of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, and sodium dimethyldithiocarbamate.

[0033] Based on the above, compared with the prior art, the rapid-dispersing polycarboxylate water reducer provided by the present invention has the following beneficial effects:

[0034] The rapid-dispersing polycarboxylate water reducer prepared by the present invention has a significantly improved adsorption rate and early adsorption amount on the surface of cement particles, and the adsorption amount of the water reducer can be maintained at a high level in the later stage. The net paste dispersion time of the cement using this water reducer is short, and less of this water reducer is required to meet the same initial net paste fluidity requirement. This water reducer has a fast dispersion speed and good dispersion performance at low temperatures, and also has good slump retention performance.

[0035] Other features and beneficial effects of the present invention will be described in the subsequent specification, and part of them will be obvious from the specification or understood by implementing the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained through the structures specifically pointed out in the specification and claims. Detailed Embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them; the technical features designed in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs, and should not be construed as a limitation of the present invention; it should be further understood that the terms used in the present invention should be understood as having a meaning consistent with their meaning in the context of this specification and the relevant art, and should not be understood in an idealized or overly formal sense, unless clearly defined as such in the present invention.

[0038] The present invention also provides the following examples and comparative examples:

[0039] Example 1

[0040] (1) Preparation of acetyl-terminated polyether macromonomer:

[0041] By weight, add 66.6 parts of 2-(4-vinyloxybutoxy)ethanol and 1.8 parts of sodium hydroxide to the first reaction vessel, stir evenly, evacuate the reaction kettle to -0.1 MPa, displace with N2 three times, heat the reaction kettle to 80 °C, and start continuously adding 933.3 parts of ethylene oxide to the reaction kettle. Control the reaction temperature at 100 °C and the reaction pressure at 0.3 MPa. After the ethylene oxide is completely added, stop the reaction when the pressure in the reaction kettle no longer drops, and obtain 1000 parts of a polyether intermediate with a molecular weight of 2400;

[0042] Continue to add 46.6 parts of 2-acetyl ethylene oxide to the reaction kettle, control the reaction temperature at 110 °C and the reaction pressure at 1.2 MPa, stop the reaction after 3 h, add acetic acid to the reaction system to neutralize until the mixture is neutral, cool to room temperature, and collect the product;

[0043] (2) Preparation of fast-dispersing polycarboxylate water reducer:

[0044] By weight, first add 70 parts of the acetyl-terminated polyether macromonomer prepared in step (1), 30 parts of methoxy ether polyethylene glycol monomethacrylate with a molecular weight of 1200, and 110 parts of water to the second reaction vessel and stir evenly. Mix 3 parts of hydrogen peroxide with 20 parts of water evenly in the first dropping device; mix 1.5 parts of disodium 2-hydroxy-2-sulfinoacetate, 0.5 part of mercaptopropionic acid with 20 parts of water evenly in the second dropping device; mix 13 parts of acrylic acid, 1.3 parts of trimethylsilyl dimethacrylate with 20 parts of water evenly in the third dropping device; at room temperature, start dropping the materials in the first dropping device, the second dropping device, and the third dropping device into the second reaction vessel in sequence, and finish dropping the materials in the third dropping device, the second dropping device, and the first dropping device respectively in 50 min, and carry out a constant-temperature reaction for 30 min;

[0045] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32%, and the fast-dispersing polycarboxylate water reducer with a concentration of 40% is obtained.

[0046] Example 2

[0047] (1) Preparation of acetyl-terminated polyether macromonomer:

[0048] By weight, 26.6 parts of 2-(4-vinyloxybutoxy)ethanol and 0.8 part of sodium metal were added to the first reaction vessel, stirred evenly, the reaction kettle was evacuated to -0.1 MPa, replaced with N2 three times, the reaction kettle was heated to 80 °C, and 973.3 parts of ethylene oxide were continuously added to the reaction kettle, controlling the reaction temperature at 120 °C and the reaction pressure at 0.5 MPa. After the ethylene oxide was completely added, the reaction was stopped when the pressure in the reaction kettle no longer decreased, obtaining 1000 parts of a polyether intermediate with a molecular weight of 6000;

[0049] Continuously add 17.2 parts of 2-acetyl ethylene oxide to the reaction kettle, control the reaction temperature at 100 °C and the reaction pressure at 0.2 MPa, stop the reaction after 2 h, add acetic acid to the reaction system to neutralize until the mixture is neutral, cool to room temperature, and collect the product;

[0050] (2) Preparation of fast-dispersing polycarboxylate water reducer:

[0051] By weight, first add 70 parts of the acetyl-terminated polyether macromonomer prepared in step (1), 30 parts of polyethylene glycol monoacrylate with a molecular weight of 600, and 95 parts of water to the second reaction vessel and stir evenly. 0.5 part of tert-butyl hydroperoxide was mixed evenly with 20 parts of water in the first dropping device; 0.5 part of ascorbic acid, 1 part of mercaptoethanol were mixed evenly with 20 parts of water in the second dropping device; 9 parts of acrylic acid, 0.5 part of trimethylsilyl dimethacrylate were mixed evenly with 20 parts of water in the third dropping device; at room temperature, the materials in the first dropping device, the second dropping device and the third dropping device were successively added dropwise to the second reaction vessel, and the materials in the third dropping device, the second dropping device and the first dropping device were added dropwise within 60 min respectively, and the reaction was carried out at a constant temperature for 30 min;

[0052] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the fast-dispersing polycarboxylate water reducer with a concentration of 40% is obtained.

[0053] Example 3

[0054] (1) Preparation of acetyl-terminated polyether macromonomer:

[0055] By weight, 266.6 parts of 2-(4-vinyloxybutoxy)ethanol and 2 parts of lithium aluminum tetrahydride were added to the first reaction vessel, stirred evenly, the reaction kettle was evacuated to -0.1 MPa, replaced with N2 three times, the reaction kettle was heated to 80 °C, and 733.3 parts of ethylene oxide were continuously added to the reaction kettle, controlling the reaction temperature at 110 °C and the reaction pressure at 0.6 MPa. After the ethylene oxide was completely added, the reaction was stopped when the pressure in the reaction kettle no longer decreased, obtaining 1000 parts of a polyether intermediate with a molecular weight of 600;

[0056] Continue to add 166.8 parts of 2-acetyl-2-methyloxirane into the reaction kettle, control the reaction temperature at 120 °C and the reaction pressure at 0.7 MPa. Stop the reaction after 1 h, add acetic acid to the reaction system to neutralize until the mixture is neutral, cool to room temperature, and collect the product.

[0057] (2) Preparation of fast-dispersing polycarboxylate superplasticizer:

[0058] By weight, first add 70 parts of the acetyl-terminated polyether macromonomer prepared in step (1), 30 parts of polyethylene glycol monomethacrylate with a molecular weight of 3000, 3 parts of sodium hypophosphite, and 102 parts of water into the second reaction vessel and stir evenly. Mix 1.5 parts of cumene hydroperoxide with 20 parts of water evenly in the first dropping device; mix 1.5 parts of sodium dimethyldithiocarbamate with 20 parts of water evenly in the second dropping device; mix 6 parts of acrylic acid, 2 parts of trimethylsilyl 3,3-dimethylacrylate with 20 parts of water evenly in the third dropping device. At room temperature, start to drop the materials in the first dropping device, the second dropping device, and the third dropping device into the second reaction vessel in sequence, and finish dropping the materials in the third dropping device, the second dropping device, and the first dropping device respectively in 70 min, and carry out a constant-temperature reaction for 30 min.

[0059] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the fast-dispersing polycarboxylate superplasticizer with a concentration of 40% is obtained.

[0060] Comparative Example 1 (without adding 2-acetyl oxirane)

[0061] The steps for preparing the fast-dispersing polycarboxylate superplasticizer are the same as those in Example 1. When preparing the acetyl-terminated polyether macromonomer, 2-acetyl oxirane is not added for end-capping modification, and the other steps for preparing the polyether macromonomer are the same as those in Example 1.

[0062] Comparative Example 2 (propylene oxide replaces 2-acetyl oxirane)

[0063] The steps and conditions for preparing the superplasticizer in this comparative example are the same as those in Example 1, with the only difference being that when preparing the acetyl-terminated polyether macromonomer, 2-acetyl oxirane is replaced with propylene oxide in equal mass.

[0064] Comparative Example 3 (4-hydroxybutyl vinyl ether replaces 2-(4-vinyloxybutoxy)ethanol)

[0065] The steps and conditions for preparing the superplasticizer in this comparative example are the same as those in Example 1, with the only difference being that when preparing the acetyl-terminated polyether macromonomer, 2-(4-vinyloxybutoxy)ethanol is replaced with 4-hydroxybutyl vinyl ether in equal mass.

[0066] Comparative Example 4 (without 3,3-dimethyltrimethoxysilane acrylate)

[0067] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, except that: when preparing the rapid-dispersing polycarboxylate water reducer, 3,3-dimethyltrimethoxysilane acrylate is not added.

[0068] Comparative Example 5 (3-(trimethoxysilyl)propyl acrylate replaces 3,3-dimethyltrimethoxysilane acrylate)

[0069] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, except that: when preparing the rapid-dispersing polycarboxylate water reducer, 3-(trimethoxysilyl)propyl acrylate is used to replace 3,3-dimethyltrimethoxysilane acrylate in equal mass.

[0070] Comparative Example 6 (methacryloyloxymethyltriethoxysilane replaces 3,3-dimethyltrimethoxysilane acrylate)

[0071] The steps for preparing the acetyl-terminated polyether macromonomer are the same as those in Example 1. When preparing the rapid-dispersing polycarboxylate water reducer, methacryloyloxymethyltriethoxysilane is used to replace 3,3-dimethyltrimethoxysilane acrylate, and the other steps for preparing the water reducer are the same as those in Example 1.

[0072] Comparative Example 7 (vinylmethyldimethoxysilane replaces 3,3-dimethyltrimethoxysilane acrylate)

[0073] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, except that: when preparing the rapid-dispersing polycarboxylate water reducer, vinylmethyldimethoxysilane is used to replace 3,3-dimethyltrimethoxysilane acrylate in equal mass.

[0074] Comparative Example 8

[0075] Commercially available Point-TS5 type polycarboxylate water reducer.

[0076] Performance test of the products in the examples and comparative examples:

[0077] (1) Adsorption amount of the water reducer product in cement paste

[0078] The rapid-dispersing polycarboxylate water reducers synthesized in Examples 1-3 and the water reducers prepared in Comparative Examples 1-8 were used to test the adsorption amount of the above water reducer products in cement paste with Conch PO52.5R cement, and the test method is as follows:

[0079] Take 20 g of cement and add it to 40 mL of the water reducer solution (the solvent of the solution is water, the cement and water are stored at 5 °C, and the concentration of the water reducer additive is 4 mg· L-1) Stir evenly, take an appropriate amount of the liquid and pour it into a centrifuge tube. Centrifuge the filtrate using a centrifuge (rotation speed: 10,000 r / min, centrifugation time: 2 min), collect the supernatant for TOC testing, and calculate the adsorption amount on the surface of cement particles. The adsorption amount results at 4 min and 60 min are shown in Table 1.

[0080] Using the above adsorption amount testing method, test the adsorption amounts at 0 min, 2 min, 4 min, 8 min, 12 min, 20 min, 40 min, and 60 min after the cement paste is stirred evenly and left standing. Fit the experimental results with the pseudo-first-order kinetic model, and calculate the adsorption rate according to the fitting results. The adsorption rate results are shown in Table 1:

[0081] Table 1 Adsorption amount and adsorption rate of samples

[0082]

[0083] (2) Fluidity of cement paste and dispersion time of cement paste

[0084] Use Conch PO52.5R cement and water stored at 5°C. According to the standard method in GB / T 8077-2012 "Test Methods for Homogeneity of Concrete Admixtures", by adjusting the dosage of the water reducer, the initial fluidity of the cement paste reaches 220 ± 10 mm. The dosages of the water reducer used are shown in Table 3, and the fluidity of the cement paste at 60 min is shown in Table 2. At this dosage, the cement paste mixer adopts a continuous fast-stirring mode, monitor the fluidity of the cement paste at different stirring times, and the minimum stirring time when the fluidity of the cement paste no longer increases is the dispersion time of the cement paste. The results are shown in Table 3.

[0085] Table 2 Fluidity of cement paste of samples

[0086]

[0087] Table 3 Dispersion time of cement paste at 5°C of samples

[0088]

[0089]

[0090] Analysis of performance test results of products in examples and comparative examples

[0091] (1) It can be seen from the test results in Tables 1-3 that:

[0092] After adding the water reducer product prepared by the present invention, not only can the adsorption rate of the water reducer on the surface of cement particles and the adsorption amount of the water reducer on the surface of cement particles in the early stage be significantly improved, and the net paste dispersion time can be shortened, but also in the later stage, the adsorption amount of the water reducer on the surface of cement particles can be maintained at a relatively high level. It can be seen that the water reducer provided by the present invention has excellent dispersion speed at low temperature; and under the requirement of the same initial net paste fluidity, less dosage of the water reducer is required, indicating that the product of the present invention has excellent dispersion performance and good slump retention performance.

[0093] (2) It can be seen from the test results of Example 1 and Comparative Examples 1-2 that:

[0094] The difference between Comparative Example 1 and Example 1 is that 2-acetyl ethylene oxide is not added; the difference between Comparative Example 2 and Example 1 is that propylene oxide is used to replace 2-acetyl ethylene oxide;

[0095] The present invention uses 2-acetyl ethylene oxide to carry out ring-opening polymerization to cap the polyether macromonomer for the preparation of the water reducer; compared with the schemes of Comparative Examples 1-2, the water reducer prepared in the example has higher adsorption amount and adsorption rate on the cement surface, and at a lower dosage, the dispersion speed at low temperature is better.

[0096] (3) It can be seen from the test results of Example 1 and Comparative Example 3 that:

[0097] The difference between Comparative Example 3 and Example 1 is that 4-hydroxybutyl vinyl ether is used to replace 2-(4-vinyloxybutoxy) ethanol;

[0098] The present invention uses 2-acetyl ethylene oxide to carry out ring-opening polymerization to cap the polyether macromonomer for the preparation of the water reducer. Compared with the scheme of Comparative Example 3, the water reducer prepared in the example has higher adsorption amount and adsorption rate on the cement surface, at a lower dosage, the dispersion speed at low temperature is better, and the slump retention performance is better.

[0099] (4) It can be seen from the test results of Example 1 and Comparative Examples 4-7 that:

[0100] The difference between Comparative Example 4 and Example 1 is that 3,3-dimethyl acrylic acid trimethylsilicone ester is not added; the difference between Comparative Example 5 and Example 1 is that 3-(trimethoxysilyl) propyl acrylate is used to replace 3,3-dimethyl acrylic acid trimethylsilicone ester; the difference between Comparative Example 6 and Example 1 is that methacryloyloxy methyl triethoxysilane is used to replace 3,3-dimethyl acrylic acid trimethylsilicone ester; the difference between Comparative Example 7 and Example 1 is that vinyl methyl dimethoxy silane is used to replace 3,3-dimethyl acrylic acid trimethylsilicone ester.

[0101] In the embodiments of the present invention, a specific functional monomer C is used for the preparation of water reducers. Compared with the solutions of Comparative Examples 4-7 (without adding functional monomer C, or using other existing silane monomers containing ester groups and silane monomers without ester groups), the water reducers prepared in the embodiments have higher adsorption amounts and adsorption rates on the cement surface. At a lower dosage, their dispersion speed is better at low temperatures. Compared with not adding functional monomer C and silane monomers without ester groups, the products of the embodiments have better slump retention performance.

[0102] Moreover, compared with the commercially available Point-TS5 type polycarboxylate water reducer in Comparative Example 8, for the water reducer provided by the embodiments of the present invention, the adsorption rate of the water reducer on the surface of cement particles and the adsorption amount of the water reducer on the surface of cement particles in the early stage are significantly increased, and the dispersion time of the neat paste is shortened; compared with the commercially available polycarboxylate water reducer in Comparative Example 8, the water reducer provided by the present invention has a better dispersion speed at low temperatures, and requires less dosage of the water reducer to meet the same initial requirement of the neat paste fluidity. The product of the present invention has better dispersion performance and better slump retention performance.

[0103] In summary, the fast-dispersing type polycarboxylate water reducer and its preparation method provided by the present invention at least include the following design concepts, action mechanisms and beneficial effects:

[0104] 1. The present invention uses 2-(4-vinyloxybutoxy)ethanol initiator and acetyl-capped monomer to prepare acetyl-capped polyether macromonomer, and uses the acetyl-capped polyether macromonomer to participate in the copolymerization reaction, so that the molecular structure of the prepared water reducer contains methyl and acyl groups. The introduction of methyl into the side chain of the water reducer makes the water reducer have better flexibility and is more likely to adhere to the cement surface, increasing the early adsorption amount, thereby achieving rapid dispersion; while the acyl group can form hydrogen bonds, which can form a stable adsorption film on the surface of cement particles by polycarboxylate water reducer molecules, preventing the aggregation and condensation of water reducer molecules, thereby improving the slump retention performance of the water reducer;

[0105] 2. Using acetyl-capped polyether macromonomer as a polyether monomer to prepare water reducer, the acetyl-capped polyether macromonomer has high reaction activity and can shorten the reaction time.

[0106] 3. The present invention introduces a specific functional monomer C into the copolymerization reaction with acetyl-capped polyether macromonomer and acrylic acid, introducing a silicon ester into the water reducer structure. The molecule has multiple methyl groups, silicon-oxygen bonds and ester groups. The introduction of multiple methyl groups into the main chain of the water reducer greatly improves the flexibility of the water reducer, enabling the water reducer to be quickly adsorbed on the surface of cement particles, showing a high adsorption rate, so as to achieve rapid dispersion of cement particles under low temperature conditions; while the ester group is continuously hydrolyzed under the alkaline conditions of cement, supplementing sufficient adsorption groups of carboxyl groups in the later stage, and the slump retention performance of the paste is better.

[0107] 5. The present invention adopts the copolymerization method of ester-ether macromonomers. Compared with simply using ether macromonomers, the dispersion rate is faster and the slump retention performance is better under low-temperature conditions.

[0108] 4. The preparation method of the water reducer provided by the present invention has simple process operation, mild reaction conditions, is easy to scale up production, and the production process is safe and pollution-free, belonging to an environmental protection product.

[0109] In summary, the rapid-dispersing polycarboxylate water reducer prepared by the present invention using a specific acetyl-terminated polyether macromonomer has a significantly improved adsorption rate and early adsorption amount on the surface of cement particles, and the later adsorption amount of the water reducer can be maintained at a high level. The paste dispersion time of the cement using this water reducer is short, and less of this water reducer is required to meet the same initial paste fluidity requirement. This water reducer has a fast dispersion rate and good dispersion performance at low temperatures, and good slump retention performance. The solution of the present invention overcomes the problems of slow dispersion rate and lag amplification of existing water reducers under low-temperature conditions, as well as good early dispersion performance and poor later slump retention performance.

[0110] It should be noted that:

[0111] The specific parameters or some common reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, rather than limitations thereto; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limitations thereto; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fast-dispersible polycarboxylate water reducer, characterized in that: It is copolymerized from an acetyl - terminated polyether macromonomer, acrylic acid, an ester macromonomer and functional monomer C through a copolymerization reaction; The acetyl - terminated polyether macromonomer is characterized in that its structural formula is as follows: ， Wherein, R is an alkylene group with 4 carbon atoms, M is an alkylene group with 2 carbon atoms; Y is a polyether chain prepared by polymerizing ethylene oxide; the B group is a group formed by the ring - opening of the carbon - oxygen bond of the epoxy group of the acetyl - terminated monomer; The ester macromonomer is one of methoxy ether polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, methoxy ether polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate; The structural formula of the acetyl - terminated monomer is: ， R1 and R2 are H or CH3; The functional monomer C is one or a combination of trimethylsilyl 3,3 - dimethacrylate, trimethylsilyl methacrylate, tributylsilyl 2 - methyl - 2 - acrylate, (2E) - 3 - {4 - [(trimethylsilyl)oxy]phenyl} - 2 - methyl - 2 - acrylate trimethylsilyl ester, (2E) - 3 - {3 - [(trimethylsilyl)oxy]phenyl} - 2 - methyl - 2 - acrylate trimethylsilyl ester.

2. The rapid-dispersing polycarboxylate water reducer according to claim 1, wherein: The acetyl - terminated monomer is one of 2 - acetyl - epoxyethane and 2 - acetyl - 2 - methyl - epoxyethane; Said Y represents a structure of (A) X of a polyether chain, wherein A is a repeating unit of polyoxyethylene, X is an integer from 1 to 100, and X is not 1.

3. The rapid-dispersing polycarboxylate water reducer according to claim 1, wherein: The weight - average molecular weight of the acetyl - terminated polyether macromonomer is 600 - 6000.

4. The rapid-dispersing polycarboxylate water reducer according to claim 1, wherein: The preparation process of the acetyl - terminated polyether macromonomer is as follows: Under the action of a catalyst, the initiator unsaturated alcohol and ethylene oxide carry out a ring - opening polymerization reaction to generate a polyether intermediate; the polyether intermediate and the acetyl - terminated monomer carry out a ring - opening reaction to obtain the acetyl - terminated polyether macromonomer; Wherein, the unsaturated alcohol is 2-(4 - vinyloxybutoxy)ethanol; the structural formula of the polyether intermediate is as follows: ； The acetyl - terminated monomer is one or a combination of 2 - acetyl - epoxyethane and 2 - acetyl - 2 - methyl - epoxyethane.

5. The rapid-dispersing polycarboxylate water reducer according to claim 4, characterized in that: The molar ratio of the acetyl - terminated monomer to the polyether intermediate is (1 - 1.3):1; The reaction temperature of the ring - opening polymerization reaction is 100 - 120 °C, the reaction pressure is 0.3 - 0.6 MPa, and the reaction end point is that the pressure of the reaction system no longer decreases; The reaction temperature of the ring - opening reaction is 100 - 120 °C, the reaction pressure is 0.2 - 1.2 MPa, and the reaction time is (1 - 3) h.

6. The rapid - dispersing polycarboxylate water - reducing agent according to claim 1, characterized in that: The molecular weight of the ester macromonomer is 600 - 3000.

7. The rapid-dispersing polycarboxylate water reducer according to claim 1, wherein: The mass ratio of the acetyl - terminated polyether macromonomer, the ester macromonomer, acrylic acid, and functional monomer C is 70:30:(6 - 13):(0.5 - 2); The copolymerization reaction is carried out at room temperature, and the reaction time is 50 - 70 min.

8. A preparation method of a fast-dispersible polycarboxylate water reducer according to any one of claims 1-7, characterized in that, It includes the following steps: Add the acetyl-terminated polyether macromonomer, ester macromonomer and solvent into a reaction vessel for mixing, then add an oxidant solution, a reductant solution, a chain transfer agent solution, acrylic acid and a functional monomer C solution respectively, and carry out a copolymerization reaction at room temperature for 50 - 70 min; after the reaction is completed, keep warm for a period of time, and add liquid alkali to adjust the pH to 6 - 7 to obtain a fast-dispersing polycarboxylate water reducer.

9. The preparation method of the rapid-dispersing polycarboxylate water reducer according to claim 8, characterized in that: The dosage of the oxidant is 0.5% - 3% of the total mass of the acetyl-terminated polyether macromonomer and the ester macromonomer; the dosage of the reductant is 0.5% - 3% of the total mass of the acetyl-terminated polyether macromonomer and the ester macromonomer; the dosage of the chain transfer agent is 0.5% - 1.5% of the total mass of the acetyl-terminated polyether macromonomer and the ester macromonomer.

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