A hydroxyl-terminated polyether macromonomer, a preparation method thereof, a low-temperature and rapid-dispersing ether-type polycarboxylate water reducer, and a preparation method thereof

Abstract

The present invention relates to the technical field of concrete admixtures, and particularly relates to a hydroxyl-terminated polyether macromonomer and a preparation method thereof, and a low-temperature rapid-dispersing ether-type polycarboxylate water reducer and a preparation method thereof. The ether-type polycarboxylate water reducer is copolymerized from a hydroxyl-terminated polyether macromonomer, acrylic acid and a functional monomer C through a copolymerization reaction. The ether-type polycarboxylate water reducer prepared by the present invention using a specific hydroxyl-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 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 also has good slump retention performance.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a hydroxyl-terminated polyether macromonomer and a preparation method thereof, a low-temperature rapid-dispersing ether-type 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 rates, strong slump retention capabilities, and a green and pollution-free production process. Due to the strong tunability of their molecular structures, polycarboxylate water reducers can produce products with different properties with different monomer compositions and polymerization processes, and 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 curls in the cement solution, and the adsorption groups are partially coated and cannot 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 at low temperatures.

[0004] The Chinese patent application with the publication number CN 115215972A discloses a preparation method of a rapid-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 polyoxyethylene ether 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 rapid-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 an unsaturated polyether macromonomer, but the steps for preparing the polyether macromonomer are relatively complex, and the polycarboxylate water reducer prepared with 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, and 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 by transesterification, using toluene as a solvent, which has the characteristic of being environmentally unfriendly.

[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. It uses monomethyl allyl ethylene glycol ether or propylene glycol monoallyl ether as the starting material, and under the action of a catalyst I, ethylene oxide and / or propylene oxide are introduced under anaerobic conditions and heated for a polymerization reaction. After the reaction is completed, propylene glycol is further introduced for a polymerization reaction to block the end. 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 the phenomenon of late return to large slump 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 a low-temperature environment, 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, which easily causes insufficient water reducers to be adsorbed in the later stage, leading to poor slump retention performance. The present invention provides a hydroxyl-terminated polyether macromonomer and an ether-type polycarboxylate water reducer copolymerized using this hydroxyl-terminated polyether macromonomer. The technical solution is as follows:

[0010] The present invention provides a hydroxyl-terminated polyether macromonomer, and its structural formula is as follows:

[0011]

[0012] Among them, R 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 a hydroxyl-terminated monomer.

[0013] The structural formula of the hydroxyl-terminated monomer is:

[0014]

[0015] R1, R2, and R3 are H or CH3; a and c are integers from 0 to 2, and b is an integer from 1 to 2.

[0016] In one embodiment, the hydroxyl-terminated monomer is one of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol, (3,3-dimethyloxiranyl)methanol, glycidol, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyloxirane methanol; Y represents a polyether chain with the structure (A) X where 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 hydroxyl-terminated polyether macromonomer is 600 - 4000.

[0018] The present invention also provides a method for preparing the above-mentioned hydroxyl-terminated polyether macromonomer, which includes the following steps:

[0019] 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 hydroxyl-terminated monomer to obtain the hydroxyl-terminated polyether macromonomer.

[0020] Among them, the unsaturated alcohol is ethylene glycol mono vinyl ether; the structural formula of the polyether intermediate is:

[0021] H2C=CH-O-R-O-Y-H;

[0022] The hydroxyl-terminated monomer is one or a combination of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol, (3,3-dimethyloxiranyl)methanol, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyloxirane methanol.

[0023] In one embodiment, the molar ratio of the polyether intermediate to the hydroxyl-terminated monomer is (1 to 1.3):1; the reaction temperature of the ring-opening polymerization reaction is 100 to 130 °C, the reaction pressure is 0.2 - 0.6 MPa, and the reaction end point is when 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 1.0 MPa, and the reaction time is (1 to 3) h.

[0024] In one embodiment, the catalyst is one or a combination of sodium hydroxide, potassium hydroxide, lithium aluminum hydride, and sodium metal.

[0025] The present invention also provides a low-temperature and rapid-dispersing ether-type polycarboxylate water reducer, which is copolymerized from a hydroxyl-terminated polyether macromonomer, acrylic acid, and functional monomer C through a copolymerization reaction;

[0026] Among them, the structural formula of the functional monomer C is as follows:

[0027]

[0028] Among them, R4, R5, and R6 are CH3, R7 and R8 are H or CH3, m, n, and p are integers from 0 to 3, d and e are integers from 0 to 2; the hydroxyl-terminated polyether macromonomer adopts the hydroxyl-terminated polyether macromonomer described in any one of claims 1 - 3, or is prepared by the preparation method of the hydroxyl-terminated polyether macromonomer described in any one of claims 4 - 5.

[0029] In one embodiment, 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.

[0030] In one embodiment, the mass ratio of the hydroxyl-terminated 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 150 to 180 min.

[0031] The present invention also provides a preparation method of the low-temperature and rapid-dispersing ether-type polycarboxylate water reducer as described above, which includes the following steps:

[0032] Add the hydroxyl-terminated polyether macromonomer and the solvent into a reaction vessel and mix them. Then, add the oxidant solution, the reductant solution, the chain transfer agent solution, acrylic acid, and the functional monomer C solution respectively, and carry out a copolymerization reaction at room temperature for 150 - 180 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 low-temperature and fast-dispersing ether-type polycarboxylate water reducer.

[0033] In one embodiment, the dosage of the oxidant is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the dosage of the reductant is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the dosage of the chain transfer agent is 0.5% - 2.0% of the total mass of the hydroxyl-terminated polyether macromonomer.

[0034] In one embodiment, the oxidant is one or a combination of cumene hydroperoxide, hydrogen peroxide, tert-butyl hydroperoxide, etc.; the reductant is one or a combination of sodium hypophosphite, ascorbic acid, disodium 2-hydroxy-2-sulfonatoacetate, etc.; the chain transfer agent is one or a combination of n-butyl mercaptan, mercaptoethanol, mercaptopropionic acid, trisodium phosphate, etc.

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

[0036] The ether-type polycarboxylate water reducer prepared by the present invention using a specific hydroxyl-terminated polyether macromonomer has a significantly increased 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 and good dispersion performance at low temperatures, and good slump retention performance.

[0037] Other features and beneficial effects of the present invention will be described in the subsequent specification, and some will become obvious from the specification or 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 drawings. 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 accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them; as long as the technical features designed in different embodiments of the present invention described below do not conflict with each other, they can be combined 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 fall within the scope of protection of the present invention.

[0039] 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 technical field 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 otherwise clearly defined in the present invention.

[0040] The present invention also provides the following embodiments and comparative examples:

[0041] Example 1

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

[0043] By weight, add 73.4 parts of ethylene glycol mono vinyl ether and 1.5 parts of potassium hydroxide to the first reaction vessel, stir evenly, evacuate the reaction kettle to -0.1 MPa, replace it with N2 three times, heat the reaction kettle to 80 °C, and start continuously adding 926.6 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 1200;

[0044] Continue to add 172.26 parts of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to the reaction kettle, control the reaction temperature at 100 °C and the reaction pressure at 1 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;

[0045] (2) Preparation of low-temperature and rapid-dispersing ether-type polycarboxylate water reducer:

[0046] By weight, first add 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1) and 105 parts of water into a second reaction vessel and stir evenly. Mix 1.5 parts of hydrogen peroxide with 20 parts of water evenly in a first dropping device; mix 1.5 parts of ascorbic acid, 0.5 part of mercaptopropionic acid with 20 parts of water evenly in a second dropping device; mix 12 parts of acrylic acid, 1 part of trimethylsilyl dimethacrylate with 20 parts of water evenly in a third dropping device. At room temperature, start to dropwise add 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 150 min, and carry out a constant-temperature reaction for 30 min;

[0047] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the low-temperature rapid-dispersing ether-type polycarboxylate water-reducing agent with a concentration of 40% is obtained.

[0048] Example 2

[0049] (1) Preparation of hydroxyl-terminated polyether macromonomer:

[0050] By weight, add 22.0 parts of ethylene glycol mono vinyl ether and 0.8 part of metallic sodium into a first reaction vessel and stir evenly. Vacuum the reaction kettle to -0.1 MPa, displace with N2 for 3 times, heat the reaction kettle to 130 °C, and start to continuously add 977.9 parts of ethylene oxide into the reaction kettle, control the reaction temperature at 130 °C and the reaction pressure at 0.2 MPa. After the ethylene oxide is completely added, stop the reaction when the pressure in the reaction kettle no longer drops, and 1000 parts of polyether intermediate with a molecular weight of 4000 is obtained;

[0051] Continue to add 25.6 parts of (3,3-dimethyloxiranyl) methanol into the reaction kettle, control the reaction temperature at 110 °C and the reaction pressure at 0.6 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;

[0052] (2) Preparation of low-temperature rapid-dispersing ether-type polycarboxylate water-reducing agent:

[0053] By weight, first add 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1) and 100 parts of water into a second reaction vessel and stir evenly. Mix 2.5 parts of cumene hydroperoxide with 20 parts of water evenly in a first dropping device; mix 0.8 part of disodium 2-hydroxy-2-sulfoacetate, 2.0 parts of trisodium phosphate with 20 parts of water evenly in a second dropping device; mix 8 parts of acrylic acid, 0.5 part of trimethylsilyl dimethacrylate with 20 parts of water evenly in a 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 within 180 min, and then carry out a constant-temperature reaction for 30 min;

[0054] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the low-temperature fast-dispersing ether-type polycarboxylate water reducer with a concentration of 40% is obtained.

[0055] Example 3

[0056] (1) Preparation of hydroxyl-terminated polyether macromonomer: By weight, add 146.8 parts of ethylene glycol mono vinyl ether and 2 parts of sodium hydroxide into a first reaction vessel and stir evenly. Vacuum the reaction kettle to -0.1 MPa, displace with N2 for 3 times, heat the reaction kettle to 80 °C, and start continuously adding 853.1 parts of ethylene oxide into the reaction kettle, control the reaction temperature at 100 °C, 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 1000 parts of a polyether intermediate with a molecular weight of 600 is obtained;

[0057] Continue to add 190.9 parts of methyl glycidol into the reaction kettle, control the reaction temperature at 120 °C, the reaction pressure at 0.2 MPa, stop the reaction after 3 h, add acetic acid to neutralize the reaction system until the mixture is neutral, cool to room temperature, and collect the product;

[0058] (2) Preparation of low-temperature fast-dispersing ether-type polycarboxylate water reducer:

[0059] By weight, first add 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1), 2.5 parts of sodium hypophosphite, and 113 parts of water into a second reaction vessel and stir evenly. Mix 0.8 part of tert-butyl hydroperoxide with 20 parts of water evenly in a first dropping device; mix 1.3 parts of mercaptoethanol with 20 parts of water evenly in a second dropping device; mix 15 parts of acrylic acid, 2 parts of trimethylsilyl 3,3-dimethylacrylate, and 20 parts of water evenly in a 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 165 min, and carry out a constant-temperature reaction for 30 min;

[0060] (3) Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and then the low-temperature fast-dispersing ether-type polycarboxylate water-reducing agent with a concentration of 40% is obtained.

[0061] Comparative Example 1 (without adding 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0062] The steps for preparing the low-temperature fast-dispersing ether-type polycarboxylate water-reducing agent are the same as those in Example 1. When preparing the hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol is not added for end-capping modification, and the other steps for preparing the polyether macromonomer are the same as those in Example 1.

[0063] Comparative Example 2 (propylene oxide replaces 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0064] The steps and conditions for preparing the water-reducing agent in this comparative example are the same as those in Example 1, except that when preparing the hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol is replaced with propylene oxide in equal mass.

[0065] Comparative Example 3 (propylene glycol replaces 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0066] The steps and conditions for preparing the water-reducing agent in this comparative example are the same as those in Example 1, except that when preparing the hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol is replaced with propylene oxide in equal mass.

[0067] Comparative Example 4 (4-hydroxybutyl vinyl ether replaces ethylene glycol mono vinyl ether)

[0068] The steps and conditions for preparing the water-reducing agent in this comparative example are the same as those in Example 1, except that when preparing the hydroxyl-terminated polyether macromonomer, ethylene glycol mono vinyl ether is replaced with 4-hydroxybutyl vinyl ether in equal mass.

[0069] Comparative Example 5 (without 3,3 - trimethylsilyl dimethacrylate)

[0070] The steps and conditions for preparing the water - reducing agent in this comparative example are the same as those in Example 1, except that: when preparing the ether - type polycarboxylate water - reducing agent, 3,3 - trimethylsilyl dimethacrylate is not added.

[0071] Comparative Example 6 (3 - (trimethoxysilyl)propyl acrylate replaces 3,3 - trimethylsilyl dimethacrylate)

[0072] The steps and conditions for preparing the water - reducing agent in this comparative example are the same as those in Example 1, except that: when preparing the ether - type polycarboxylate water - reducing agent, 3 - (trimethoxysilyl)propyl acrylate is used to replace 3,3 - trimethylsilyl dimethacrylate in equal mass.

[0073] Comparative Example 7 (methacryloyloxymethyltriethoxysilane replaces 3,3 - trimethylsilyl dimethacrylate)

[0074] The steps for preparing the hydroxyl - terminated polyether macromonomer are the same as those in Example 1. When preparing the low - temperature and fast - dispersing type ether - type polycarboxylate water - reducing agent, methacryloyloxymethyltriethoxysilane is used to replace 3,3 - trimethylsilyl dimethacrylate, and the other steps for preparing the water - reducing agent are the same as those in Example 1.

[0075] Comparative Example 8 (vinylmethyldimethoxysilane replaces 3,3 - trimethylsilyl dimethacrylate)

[0076] The steps and conditions for preparing the water - reducing agent in this comparative example are the same as those in Example 1, except that: when preparing the ether - type polycarboxylate water - reducing agent, vinylmethyldimethoxysilane is used to replace 3,3 - trimethylsilyl dimethacrylate in equal mass.

[0077] Comparative Example 9

[0078] Commercially available Point - TS5 type polycarboxylate water - reducing agent.

[0079] Performance testing of the products of the examples and comparative examples:

[0080] (1) Adsorption amount of the water - reducing agent product in cement paste

[0081] The low - temperature and fast - dispersing type ether - type polycarboxylate water - reducing agents synthesized in Examples 1 - 3 and the water - reducing agents prepared in Comparative Examples 1 - 9 were used to test the adsorption amount of the above - mentioned water - reducing agent products in cement paste with Conch PO52.5R cement. The test method is as follows:

[0082] Take 20 g of cement and add it to 40 mL of 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 is 4 mg·L-1). Stir evenly, take an appropriate amount of the liquid and pour it into a centrifuge tube, and use a centrifuge to centrifuge and separate the filtrate (the rotation speed is 10,000 r / min, and the centrifugation time is 2 min). Collect the supernatant for TOC testing, and calculate the adsorption amount on the surface of the cement particles. The adsorption amount results at 4 min and 60 min are shown in Table 1.

[0083] 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. And use the pseudo-first-order kinetic model to fit the experimental results, and calculate the adsorption rate according to the fitting results. Among them, the adsorption rate results are shown in Table 1:

[0084] Table 1 Adsorption amount and adsorption rate of samples

[0085]

[0086]

[0087] (2) Fluidity of cement paste and dispersion time of cement paste

[0088] Use Conch PO52.5R cement and water stored at 5 °C, and 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 dosage of the water reducer used is shown in Table 3, and the fluidity of the cement paste at 60 min is tested as shown in Table 2. At this dosage, the cement paste mixer adopts a continuous fast-stirring mode, and monitors the fluidity of the cement paste at different stirring times. The minimum stirring time when the fluidity of the cement paste no longer increases is the dispersion time of the cement paste, and the results are shown in Table 3.

[0089] Table 2 Fluidity of cement paste of samples

[0090]

[0091]

[0092] Table 3 Dispersion time of cement paste at 5 °C of samples

[0093] Sample Name Dosage / % Net Paste Dispersion Time / s Example 1 0.10 25 Example 2 0.10 29 Example 3 0.10 31 Comparative Example 1 0.12 55 Comparative Example 2 0.12 52 Comparative Example 3 0.12 53 Comparative Example 4 0.16 60 Comparative Example 5 0.14 68 Comparative Example 6 0.14 46 Comparative Example 7 0.12 39 Comparative Example 8 0.14 62 Comparative Example 9 0.15 78

[0094] Analysis of performance test results of products in examples and comparative examples

[0095] (1) It can be seen from the test results in Tables 1-3:

[0096] After adding the water reducing agent product prepared according to the present invention, not only can 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 be significantly improved, and the net paste dispersion time can be shortened. Thus, it can be seen that the water reducing agent 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 reducing agent is required, indicating that the product of the present invention has excellent dispersion performance and good slump retention performance.

[0097] (2) It can be seen from the test results of Example 1 and Comparative Examples 1-3 that:

[0098] The difference between Comparative Example 1 and Example 1 is that 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol is not added; the difference between Comparative Example 2 and Example 1 is that propylene oxide is used to replace 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol; the difference between Comparative Example 3 and Example 1 is that propylene glycol is used to replace 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol;

[0099] The present invention uses 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to open-loop polymerize and cap the polyether monomer for the preparation of the water reducing agent; compared with the schemes of Comparative Examples 1-3, the water reducing agent 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.

[0100] (3) It can be seen from the test results of Example 1 and Comparative Example 4 that:

[0101] The difference between Comparative Example 4 and Example 1 is that 4-hydroxybutyl vinyl ether is used to replace ethylene glycol mono vinyl ether;

[0102] The present invention uses 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to open-loop polymerize and cap the polyether monomer for the preparation of the water reducing agent. Compared with the scheme of Comparative Example 4, the water reducing agent 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 and the slump retention performance is better.

[0103] (4) It can be seen from the test results of Example 1 and Comparative Examples 5-8 that:

[0104] The differences between Comparative Example 5 and Example 1 are as follows: 3,3-trimethylsilyl dimethacrylate is not added; the differences between Comparative Example 6 and Example 1 are as follows: 3-(trimethoxysilyl)propyl acrylate is used to replace 3,3-trimethylsilyl dimethacrylate; the differences between Comparative Example 7 and Example 1 are as follows: methacryloxymethyltriethoxysilane is used to replace 3,3-trimethylsilyl dimethacrylate; the differences between Comparative Example 8 and Example 1 are as follows: vinylmethyldimethoxysilane is used to replace 3,3-trimethylsilyl dimethacrylate;

[0105] In the examples of the present invention, a specific functional monomer C is used for the preparation of the water reducer. Compared with the schemes of Comparative Examples 5-8 (without adding the functional monomer C, or using other existing silane monomers containing ester groups and silane monomers without ester groups), the water reducer prepared in the examples has higher adsorption amount and adsorption rate on the cement surface. At a lower dosage, its dispersion speed is better at low temperature. Compared with not adding the functional monomer C and silane monomers without ester groups, the product of the example has better slump retention performance.

[0106] Moreover, compared with the commercially available Point-TS5 polycarboxylate water reducer in Comparative Example 9, the water reducer provided in the examples of the present invention has significantly improved water reducer adsorption rate on the surface of cement particles and water reducer adsorption amount on the surface of cement particles in the early stage, and the net paste dispersion time is shortened; compared with the commercially available polycarboxylate water reducer in Comparative Example 9, the water reducer provided in the present invention has better dispersion speed at low temperature, and requires less dosage of the water reducer to meet the same initial net paste fluidity requirement. The product of the present invention has better dispersion performance and better slump retention performance.

[0107] In summary, the low-temperature rapid-dispersing ether-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:

[0108] 1. The present invention uses ethylene glycol mono vinyl ether (unsaturated alcohol) initiator and a specific hydroxyl-terminated monomer to prepare a hydroxyl-terminated polyether macromonomer, and uses this hydroxyl-terminated polyether macromonomer to participate in the copolymerization reaction, so that the molecular structure of the prepared water reducer contains methyl and hydroxyl 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, thus achieving rapid dispersion; while the hydroxyl group reacts chemically with the surface of the cement particles to form hydrogen bonds, which can increase the adsorption between the water reducer and the cement particles, thereby reducing the coagulation effect between the cement particles and improving the dispersion performance of the cement particles;

[0109] 2. The present invention introduces a specific functional monomer C into the copolymerization reaction with a hydroxyl-terminated polyether macromonomer and acrylic acid, introducing silicone grease into the structure of the water reducer. The molecule has multiple methyl groups, siloxane 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 quickly adsorb on the surface of cement particles, showing a high adsorption rate, so that the cement particles can be rapidly dispersed under low-temperature conditions; and the ester groups are 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 slurry is better.

[0110] 3. 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 is safe and pollution-free during the production process, belonging to an environmental protection product.

[0111] In summary, the ether-based polycarboxylate water reducer prepared by the present invention using a specific hydroxyl-terminated polyether macromonomer 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 temperature, and good slump retention performance. The solution of the present invention overcomes the problems of slow dispersion speed and lag amplification of existing water reducers under low-temperature conditions, as well as good dispersion performance in the early stage and poor slump retention performance in the later stage.

[0112] It should be noted that:

[0113] 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.

[0114] 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 on 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 hydroxyl-terminated polyether macromonomer, characterized in that, The structural formula is as follows: ， Wherein, R is an alkylene group with 2 carbon atoms; the B group is a group formed by the cleavage and ring-opening of the carbon-oxygen bond of the epoxy group of a hydroxyl-terminated monomer; The hydroxyl-terminated monomer is one of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyl oxirane methanol; Said Y represents a polyether chain having the structure of (A) X , where A is a repeating unit of polyethylene oxide, X is an integer from 1 to 100 and X is not 1.

2. The hydroxy-terminated polyether macromonomer according to claim 1, wherein: The weight-average molecular weight of the hydroxyl-terminated polyether macromonomer is 600-4000.

3. A method for preparing a hydroxyl-terminated polyether macromonomer according to any one of claims 1-2, 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 hydroxyl-terminated monomer to obtain a hydroxyl-terminated polyether macromonomer; Wherein, the unsaturated alcohol is ethylene glycol mono vinyl ether; the structural formula of the polyether intermediate is: ； The hydroxyl-terminated monomer is one or a combination of more than one of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyl oxirane methanol; 4. The preparation method of the hydroxyl-terminated polyether macromonomer according to claim 3, characterized in that: The molar ratio of the hydroxyl-terminated monomer to the polyether intermediate is (1-1.3):1; The reaction temperature of the ring-opening polymerization reaction is 100-130°C, the reaction pressure is 0.2-0.6 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 0.2-1.0 MPa, and the reaction time is (1-3) h.

5. A low-temperature and fast-dispersing ether-based polycarboxylate water reducer, characterized in that: It is copolymerized from a hydroxyl-terminated polyether macromonomer, acrylic acid and functional monomer C; The hydroxyl-terminated polyether macromonomer adopts the hydroxyl-terminated polyether macromonomer described in any one of claims 1-2, or is prepared by the preparation method of the hydroxyl-terminated polyether macromonomer described in any one of claims 3-4; the functional monomer C is one or a combination of more than one of trimethylsilyl 3,3-dimethylacrylate, trimethylsilyl methacrylate, tributylsilyl 2-methyl-2-acrylate, (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}trimethylsilyl acrylate, (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}trimethylsilyl acrylate; 6. The low-temperature rapid-dispersing ether-type polycarboxylate water reducer according to claim 5, characterized in that: The mass ratio of the hydroxyl-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 150-180 min.

7. A preparation method of a low-temperature rapid-dispersing ether-based polycarboxylate water-reducing agent according to any one of claims 5-6, characterized in that, It includes the following steps: Add the hydroxyl-terminated 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 150-180 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 low-temperature and fast-dispersing ether-type polycarboxylate water reducer.

8. The preparation method of the low-temperature and rapid-dispersing ether-type polycarboxylate water reducer according to claim 7, wherein: The dosage of the oxidant is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the dosage of the reducing agent is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the dosage of the chain transfer agent is 0.5% - 2.0% of the total mass of the hydroxyl-terminated polyether macromonomer.

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