An acetyl-terminated polyether macromonomer, a preparation method thereof, a concrete water reducer and a preparation method thereof

Abstract

The present invention relates to the technical field of concrete admixtures, and particularly relates to an acetyl-terminated polyether macromonomer and a preparation method thereof, a concrete water reducer and a preparation method thereof. The water reducer is copolymerized from an acetyl-terminated polyether macromonomer, acrylic acid and a functional monomer C through a copolymerization reaction. The concrete 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 water reducer adsorption amount in the later stage 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 and good dispersion performance at low temperatures, and good slump retention performance.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to an acetyl-terminated polyether macromonomer, a preparation method thereof, a concrete water reducer, and a preparation method thereof. Background Art

[0002] As the latest generation of concrete admixtures, polycarboxylate water reducers have a high water reduction rate, strong slump retention ability, and a green and pollution-free production process. Due to the strong tunability of their molecular structure, 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 reducers is relatively long, and it curls in the cement solution, with the adsorption groups being partially coated and unable to quickly exert their adsorption ability, resulting in a slow dispersion rate of polycarboxylate water reducers 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 leads to insufficient water reducers being 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 ring-opening polymerization of glycidyl ether is initiated 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 carboxylic acid small monomers to obtain the fast-dispersing polycarboxylate water reducer. In the preparation process of this polyether macromonomer, organic solvents are used, which not only have high costs but also pollute 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 using this polyether macromonomer mainly has an improvement in shrinkage reduction performance.

[0006] The Chinese invention patent with the patent publication 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 between 20,000 and 100,000. However, the self-made tertiary amino unsaturated monomer is carried out through transesterification, using toluene as a solvent, which has the characteristic of being not environmentally friendly.

[0007] The Chinese invention patent with the patent publication number CN112707674 B discloses a high-adsorption and dispersing polycarboxylate water reducer and its preparation method, which 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, having 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. Using monomethyl allyl ethylene glycol ether or propylene glycol monoallyl ether as the starting material, 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, without bleeding and late re-growth phenomena during the process, has the function of water retention and slurry raising, and good workability. However, it does not mention the 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 dispersion speed is relatively slow in low-temperature environments, resulting in low concrete production efficiency and the phenomenon of reverse growth of fluidity in the later stage, affecting the quality of concrete projects. Moreover, the existing polycarboxylate water reducers are adsorbed more by cement particles in the early stage, easily causing insufficient water reducers to be adsorbed in the later stage, resulting in poor slump retention performance. The present invention provides an acetyl-capped polyether macromonomer and a concrete water reducer copolymerized using this acetyl-capped polyether macromonomer. The technical solution is as follows:

[0010] The present invention provides an acetyl-capped polyether macromonomer, and its structural formula is as follows:

[0011]

[0012] Among them, 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;

[0013] The structural formula of the acetyl-capped monomer is:

[0014]

[0015] R1 and R2 are H or CH3.

[0016] 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 (A) X wherein A is a repeating unit of polyoxyethylene and X is an integer from 1 to 100.

[0017] In one embodiment, the weight-average molecular weight of the acetyl-capped polyether macromonomer is 600 - 6000.

[0018] The present invention also provides a method for preparing the acetyl-capped polyether macromonomer as described above, which includes the following steps: 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;

[0019] Among them, 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 more than one 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 more than one of sodium hydroxide, potassium hydroxide, lithium aluminum hydride, and sodium metal.

[0024] The present invention also provides a concrete water reducer, which is copolymerized from an acetyl-terminated polyether macromonomer, acrylic acid and functional monomer C through a copolymerization reaction;

[0025] Among them, the structural formula of the functional monomer C is as follows:

[0026]

[0027] Among them, R3, R4, and R5 are CH3, and 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;

[0028] The acetyl-terminated polyether macromonomer adopts the acetyl-terminated polyether macromonomer described in any one of the above, or is prepared by the preparation method of the acetyl-terminated polyether macromonomer described above.

[0029] In one embodiment, the functional monomer C is one or a combination of more than one of 3,3-dimethylacryloxytrimethylsilane, methacryloxytrimethylsilane, tributylsilyl 2-methyl-2-propenoate, (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}-2-propenoic acid trimethylsilyl ester, and (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}-2-propenoic acid trimethylsilyl ester.

[0030] In one embodiment, the mass ratio of the acetyl-terminated polyether macromonomer, acrylic acid, and functional monomer C is 100:(8 - 15):(0.5 - 2); the copolymerization reaction is carried out at room temperature, and the reaction time is 50 - 70 min.

[0031] The present invention also provides a preparation method of the concrete water reducer described above, which is characterized by including the following steps:

[0032] Add the acetyl-terminated polyether macromonomer and a solvent into a reaction vessel for mixing, and then respectively add an oxidant solution, a reductant solution, a chain transfer agent solution, acrylic acid, and a functional monomer C solution, and carry out a copolymerization reaction at room temperature for 50 - 70 min; after the reaction ends, keep warm for a period of time, and add liquid caustic soda to adjust the pH to 6 - 7 to obtain the concrete water reducer.

[0033] In one embodiment, the dosage of the oxidant is 0.5% - 3% of the total mass of the acetyl-terminated polyether macromonomer; the dosage of the reductant is 0.5% - 3% of the total mass of the acetyl-terminated polyether macromonomer; the dosage of the chain transfer agent is 0.5% - 1.5% of the total mass of the acetyl-terminated polyether macromonomer.

[0034] In one embodiment, the oxidizing agent 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.

[0035] Based on the above, compared with the prior art, the acetyl-terminated polyether macromonomer provided by the present invention and the concrete water reducer synthesized using the acetyl-terminated polyether macromonomer have the following beneficial effects:

[0036] The concrete 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 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.

[0037] Other features and beneficial effects of the present invention will be described in the subsequent specification, and, in part, will be apparent from the specification or will be 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, claims, and solutions. Detailed Embodiments

[0038] 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 in conjunction with the solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments; 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.

[0039] In the description of the present invention, it should be noted that all terms (including technical terms and scientific terms) used in the present invention 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.

[0040] The present invention also provides the following examples and comparative examples as shown below:

[0041] Example 1

[0042] (1) Preparation of acetyl-terminated polyether macromonomer:

[0043] By weight, 66.6 parts of 2-(4-vinyloxybutoxy)ethanol and 1 part of sodium metal were added to the first reaction vessel and stirred evenly. The reaction kettle was evacuated to -0.1 MPa, replaced with N2 three times, the temperature of the reaction kettle was raised to 80 °C, and 933.3 parts of ethylene oxide were continuously added to the reaction kettle. The reaction temperature was controlled at 110 °C and the reaction pressure was 0.3 MPa. After the ethylene oxide was completely added, the reaction was stopped when the pressure in the reaction kettle no longer decreased, and 1000 parts of a polyether intermediate with a molecular weight of 2400 were obtained.

[0044] Then, 39.4 parts of 2-acetyl ethylene oxide were added to the reaction kettle. The reaction temperature was controlled at 110 °C and the reaction pressure was 0.6 MPa. After 2 h, the reaction was stopped. Acetic acid was added to the reaction system to neutralize the mixture until it was neutral, and then cooled to room temperature, and the product was collected;

[0045] (2) Preparation of concrete water reducer:

[0046] By weight, first, 100 parts of the acetyl-terminated polyether macromonomer prepared in step (1) and 107 parts of water were added to the second reaction vessel and stirred evenly. 2 parts of cumene hydroperoxide were mixed evenly with 20 parts of water in the first dropping device; 1.5 parts of ascorbic acid and 1 part of mercaptoacetic acid were mixed evenly with 20 parts of water in the second dropping device; 12 parts of acrylic acid and 2 parts of trimethylsilyl 3,3-dimethylacrylate 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;

[0047] (3) 10 parts of sodium hydroxide with a mass concentration of 32% by weight was added to obtain the concrete water reducer with a concentration of 40%.

[0048] Example 2

[0049] (1) Preparation of acetyl-terminated polyether macromonomer: By weight, add 26.6 parts of 2-(4-vinyloxybutoxy)ethanol and 2 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 973.3 parts of ethylene oxide to the reaction kettle. Control the reaction temperature at 120 °C and the reaction pressure at 0.5 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 6000;

[0050] Continue to add 14.35 parts of 2-acetyl ethylene oxide to the reaction kettle, control the reaction temperature at 100 °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;

[0051] (2) Preparation of concrete water reducer: By weight, first add 100 parts of the acetyl-terminated polyether macromonomer prepared in step (1) and 100 parts of water to the second reaction vessel and stir evenly. Mix 3 parts of hydrogen peroxide and 20 parts of water evenly in the first dropping device; Mix 0.5 part of disodium 2-hydroxy-2-sulfinoacetate, 1.5 parts of sodium dimethyldithiocarbamate and 20 parts of water evenly in the second dropping device; Mix 8 parts of acrylic acid, 1 part of trimethylsilyl 3,3-dimethylacrylate and 20 parts of water evenly in the third dropping device; At room temperature, sequentially start dropping the materials in the first dropping device, the second dropping device and the third dropping device into the second reaction vessel, 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;

[0052] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight to obtain the concrete water reducer with a concentration of 40%.

[0053] Example 3

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

[0055] By weight, add 266.6 parts of 2-(4-vinyloxybutoxy)ethanol and 1.8 parts of lithium aluminum tetrahydride 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 733.3 parts of ethylene oxide to the reaction kettle. Control the reaction temperature at 100 °C and the reaction pressure at 0.6 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 600.

[0056] Continue to add 216.9 parts of 2-acetyl-2-methyloxirane into the reaction kettle, control the reaction temperature at 120 °C, the reaction pressure at 0.2 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 concrete water reducer:

[0058] By weight, first add 100 parts of the acetyl-terminated polyether macromonomer prepared in step (1), 3 parts of sodium hypophosphite and 110 parts of water into the second reaction vessel and stir evenly. 0.5 part of tert-butyl hydroperoxide is mixed evenly with 20 parts of water in the first dropping device; 0.5 part of mercaptoethanol is mixed evenly with 20 parts of water in the second dropping device; 15 parts of acrylic acid, 0.5 part of trimethylsilyl 3,3-dimethylacrylate are 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 are successively added dropwise into the second reaction vessel, and the materials in the third dropping device, the second dropping device and the first dropping device are added dropwise respectively within 50 min, and the reaction is carried out at a constant temperature for 30 min;

[0059] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the concrete water reducer with a concentration of 40% is obtained.

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

[0061] The steps for preparing the concrete water reducer 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 water reducer in this comparative example are the same as those in Example 1, except 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 water reducer in this comparative example are the same as those in Example 1, except 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 adding trimethylsilyl 3,3-dimethylacrylate)

[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 concrete 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 concrete water reducer, 3-(trimethoxysilyl)propyl acrylate is used to replace 3,3-dimethyltrimethoxysilane acrylate in equal mass. Comparative Example 6 (methacryloxymethyltriethoxysilane replaces 3,3-dimethyltrimethoxysilane acrylate)

[0070] The steps for preparing the acetyl-terminated polyether macromonomer are the same as those in Example 1. When preparing the concrete water reducer, methacryloxymethyltriethoxysilane 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.

[0071] Comparative Example 7 (vinylmethyldimethoxysilane replaces 3,3-dimethyltrimethoxysilane acrylate)

[0072] 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 concrete water reducer, vinylmethyldimethoxysilane is used to replace 3,3-dimethyltrimethoxysilane acrylate in equal mass.

[0073] Comparative Example 8

[0074] The commercially available Point-TS5 type polycarboxylate water reducer.

[0075] Performance test of the products in the examples and comparative examples:

[0076] (1) Adsorption amount of the water reducer product in cement paste

[0077] The concrete 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. The test method is as follows:

[0078] 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.

[0079] 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 using the pseudo-first-order kinetic model, and calculate the adsorption rate based on the fitting results. The adsorption rate results are shown in Table 1:

[0080] Table 1 Adsorption amount and adsorption rate of samples

[0081]

[0082] (2) Fluidity of cement paste and dispersion time of cement paste

[0083] 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.

[0084] Table 2 Fluidity of cement paste of samples

[0085]

[0086] Table 3 Dispersion time of cement paste at 5°C of samples

[0087] Sample Name Dosage / % Net Paste Dispersion Time / s Example 1 0.10 38 Example 2 0.10 41 Example 3 0.10 43 Comparative Example 1 0.12 60 Comparative Example 2 0.12 57 Comparative Example 3 0.12 66 Comparative Example 4 0.16 70 Comparative Example 5 0.14 59 Comparative Example 6 0.12 52 Comparative Example 7 0.14 65 Comparative Example 8 0.15 79

[0088] Analysis of performance test results of products in examples and comparative examples

[0089] (1) It can be seen from the test results in Tables 1-3 that:

[0090] After adding the water reducer product prepared in the present invention, not only can it significantly improve 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, shorten the dispersion time of neat cement, 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. Thus, 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 fluidity of neat cement, less dosage of the water reducer is needed, indicating that the product of the present invention has excellent dispersion performance and good slump retention performance.

[0091] (2) It can be seen from the test results of Example 1 and Comparative Examples 1-2 that:

[0092] 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;

[0093] 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, it has better dispersion speed at low temperature.

[0094] (3) It can be seen from the test results of Example 1 and Comparative Example 3 that:

[0095] The difference between Comparative Example 3 and Example 1 is that 4-hydroxybutyl vinyl ether is used to replace 2-(4-vinyloxybutoxy) ethanol;

[0096] 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, and at a lower dosage, it has better dispersion speed at low temperature and better slump retention performance.

[0097] (4) It can be seen from the test results of Example 1 and Comparative Examples 4-7 that:

[0098] The difference between Comparative Example 4 and Example 1 is that 3,3-dimethyltrimetylsilyl acrylate is not added; the difference between Comparative Example 5 and Example 1 is that 3-(trimethoxysilyl)propyl acrylate is used to replace 3,3-dimethyltrimetylsilyl acrylate; the difference between Comparative Example 6 and Example 1 is that methacryloxymethyltriethoxysilane is used to replace 3,3-dimethyltrimetylsilyl acrylate; the difference between Comparative Example 7 and Example 1 is that vinylmethyldimethoxysilane is used to replace 3,3-dimethyltrimetylsilyl acrylate.

[0099] In the embodiments of the present invention, a specific functional monomer C is used for preparing a water reducing agent. 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 reducing agent prepared in the embodiments has higher adsorption amount and adsorption rate on the cement surface. At a lower dosage, its dispersion rate is better at low temperature. Compared with the case of not adding functional monomer C and silane monomers without ester groups, the product of the embodiments has better slump retention performance.

[0100] Moreover, compared with the commercially available Point-TS5 type polycarboxylate water reducing agent in Comparative Example 8, for the water reducing agent provided in the embodiments of the present invention, the adsorption rate of the water reducing agent on the surface of cement particles and the adsorption amount of the water reducing agent 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 reducing agent in Comparative Example 8, the water reducing agent provided by the present invention has excellent dispersion rate at low temperature, and requires less dosage of the water reducing agent to meet the same initial fluidity requirement of the neat paste. The product of the present invention has better dispersion performance and better slump retention performance.

[0101] In summary, the concrete water reducing agent and its preparation method provided by the present invention at least include the following design concepts, action mechanisms and beneficial effects:

[0102] 1. The present invention uses 2-(4-vinyloxybutoxy)ethanol initiator and acetyl-capped monomer to prepare an 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 reducing agent contains methyl and acyl groups. The introduction of methyl into the side chain of the water reducing agent makes the water reducing agent have better flexibility and is more likely to adhere to the cement surface, increasing the early adsorption amount, thus 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 reducing agent molecules, preventing the aggregation and coagulation of water reducing agent molecules, thereby improving the slump retention performance of the water reducing agent;

[0103] 2. Using the acetyl-capped polyether macromonomer as a polyether monomer to prepare a water reducing agent, the acetyl-capped polyether macromonomer has high reaction activity and can shorten the reaction time.

[0104] 3. The present invention introduces a specific functional monomer C into the copolymerization reaction with the acetyl-capped polyether macromonomer and acrylic acid, introducing a silicon ester into the structure of the water reducing agent. 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 reducing agent greatly improves the flexibility of the water reducing agent, enabling the water reducing agent 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 condition of cement, supplementing sufficient adsorption groups of carboxyl groups in the later stage, and the slump retention performance of the paste is better.

[0105] 4. The preparation method of the water reducing agent provided by the present invention has simple process operations, mild reaction conditions, is easy to scale up production, and is safe and pollution-free during the production process, belonging to an environmental protection product.

[0106] In summary, the concrete water reducing agent prepared by the present invention using a specific acetyl-terminated polyether macromonomer has significantly improved adsorption rate and early adsorption amount on the surface of cement particles, and the later adsorption amount of the water reducing agent can be maintained at a relatively high level. The net paste dispersion time of the cement using this water reducing agent is short, and less of this water reducing agent is required to meet the same initial net paste fluidity requirement. This water reducing agent has a fast dispersion speed and good dispersion performance at low temperatures, and good slump retention performance. The solution of the present invention overcomes the problems of slow dispersion speed and lag amplification of existing water reducing agents under low temperature conditions, as well as good early dispersion performance and poor later slump retention performance.

[0107] It should be noted that:

[0108] 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.

[0109] 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 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. An acetyl-terminated polyether macromonomer, characterized in that, The 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 cleavage and ring-opening of the carbon-oxygen bond of the epoxy group of an acetyl-capped monomer; The structural formula of the acetyl-capped monomer is: ， R1 and R2 are H or CH3.

2. The acetyl-terminated polyether macromonomer according to claim 1, wherein: The acetyl-capped monomer is one of 2-acetyl ethylene oxide and 2-acetyl-2-methyl ethylene oxide; Said Y represents a polyether chain having the structure of (A) X , wherein A is a repeating unit of polyoxyethylene, X is an integer from 1 to 100, and X is not 1.

3. The acetyl-terminated polyether macromonomer according to claim 1, characterized in that: The weight-average molecular weight of the acetyl-capped polyether macromonomer is 600 to 6000.

4. A method for preparing an acetyl-terminated polyether macromonomer according to any one of claims 1-3, characterized in that, It includes the following steps: 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 an acetyl-capped polyether macromonomer; Wherein, the unsaturated alcohol is 2-(4-vinyloxybutoxy)ethanol; the structural formula of the polyether intermediate is as follows: ； The acetyl-capped monomer is one or a combination of 2-acetyl ethylene oxide and 2-acetyl-2-methyl ethylene oxide.

5. The preparation method of the acetyl-terminated polyether macromonomer according to claim 4, characterized in that: The molar ratio of the acetyl-capped monomer to the polyether intermediate is (1 to 1.3):1; The reaction temperature of the ring-opening polymerization reaction is 100 to 120 °C, the reaction pressure is 0.3 to 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 to 120 °C, the reaction pressure is 0.2 to 1.2 MPa, and the reaction time is (1 to 3) h.

6. A concrete water reducing agent, characterized in that: It is copolymerized from an acetyl-capped polyether macromonomer, acrylic acid and functional monomer C; The acetyl-capped polyether macromonomer is the acetyl-capped polyether macromonomer described in any one of claims 1-3, or is prepared by the preparation method of the acetyl-capped polyether macromonomer described in any one of claims 4-5; the functional monomer C is one or a combination of 3,3-dimethylacryloyloxytrimethylsilane, methacryloyloxytrimethylsilane, tributylsilyl 2-methyl-2-propenoate, trimethylsilyl (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}acrylate, and trimethylsilyl (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}acrylate.

7. The concrete water reducer according to claim 6, characterized in that: The mass ratio of the acetyl-capped polyether macromonomer, acrylic acid, and functional monomer C is 100:(8 to 15):(0.5 to 2); The copolymerization reaction is carried out at room temperature, and the reaction time is 50 to 70 min.

8. A preparation method of a concrete water reducing agent according to any one of claims 6-7, characterized in that, It includes the following steps: Add the acetyl-capped polyether macromonomer and a solvent into a reaction vessel and mix them, 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 to 70 min; after the reaction is completed, keep warm for a period of time, and add liquid alkali to adjust the pH to 6 to 7 to obtain a concrete water reducer.

9. The preparation method of the concrete water reducing agent according to claim 8, characterized in that: The dosage of the oxidant is 0.5% - 3% of the total mass of the acetyl-capped polyether macromonomer; the dosage of the reducing agent is 0.5% - 3% of the total mass of the acetyl-capped polyether macromonomer; the dosage of the chain transfer agent is 0.5% - 1.5% of the total mass of the acetyl-capped polyether macromonomer.

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