Hydroxyl-terminated polyether macromonomer and preparation method therefor, and low-temperature rapid-dispersion-type ether polycarboxylic acid superplasticizer and preparation method therefor

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 therefor, and a low-temperature rapid-dispersion-type ether polycarboxylic acid superplasticizer and a preparation method therefor. The ether polycarboxylic acid superplasticizer is formed by copolymerizing the hydroxyl-terminated polyether macromonomer, acrylic acid and a functional monomer C by means of a copolymerization reaction. The ether polycarboxylic acid superplasticizer, which is prepared by using the specific hydroxyl-terminated polyether macromonomer in the present invention, has a significantly improved adsorption rate and early-stage adsorption capacity on the surfaces of cement particles; in addition, the adsorption capacity of the superplasticizer in the later stage can be kept at a relatively high level, the cement paste dispersion time of cement using the superplasticizer is short, and the requirements of the superplasticizer are less while satisfying the same initial cement paste fluidity requirement; and the superplasticizer has a high dispersion speed, good dispersion performance, and good slump-retaining performance at low temperatures.

Description

A hydroxyl-terminated polyether macromonomer and its preparation method, a low-temperature fast-dispersing ether polycarboxylate water reducer and its preparation method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 2023116082693, filed with the Patent Office of China on November 29, 2023, entitled "A hydroxyl-terminated polyether macromonomer and its preparation method, low-temperature fast-dispersing ether polycarboxylic acid water reducer and its preparation method", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of concrete admixtures, and in particular to a hydroxyl-terminated polyether macromonomer and a preparation method thereof, a low-temperature fast-dispersing ether polycarboxylate water reducer and a preparation method thereof. Background Art

[0004] As the latest generation of concrete admixtures, polycarboxylate superplasticizers offer high water-reducing rates, strong slump-reducing properties, and a green, pollution-free production process. Due to their highly tunable molecular structure, polycarboxylate superplasticizers can be formulated to produce products with varying performance, depending on monomer composition and polymerization process. They offer significant potential for high-performance development, making them the most effective, economical, and simplest technological approach to achieving enhanced concrete durability and performance.

[0005] Polycarboxylate superplasticizers have long molecular chains, which curl in cement solutions. This partially encapsulates the adsorption groups, preventing them from rapidly exerting their adsorption capacity. This results in slow dispersion at low temperatures, low concrete production efficiency, and a subsequent increase in fluidity, impacting the quality of concrete projects. Furthermore, polycarboxylate superplasticizers are heavily adsorbed by cement particles in the early stages, which can lead to insufficient adsorption later and poor slump retention. Therefore, developing a superplasticizer that can rapidly adsorb cement particles at low temperatures, improve their dispersion, and provide excellent slump retention in the later stages through molecular structure design is of great significance.

[0006] Chinese invention patent application CN 115215972A discloses a method for preparing a rapidly dispersible polycarboxylate water-reducing agent. The method involves in-situ generation of terminally hyperbranched polyoxyethylene ether macromolecules by initiating ring-opening polymerization of glycidyl ether via the terminal hydroxyl groups of a polyether macromonomer. The terminal reactive hydroxyl groups of the terminally hyperbranched polyether are then converted into carboxyl adsorption groups, which are then copolymerized with a carboxylate micromonomer to produce the rapidly dispersible polycarboxylate water-reducing agent. The use of organic solvents in the preparation of this polyether macromonomer is not only costly but also environmentally polluting. Furthermore, the resulting water-reducing agent exhibits good dispersibility only at room temperature.

[0007] A Chinese invention patent with the patent publication number CN 113736036B discloses a multi-arm polycarboxylate water-reducing agent and a preparation method thereof. The method involves terminal halogenation of an unsaturated polyether macromonomer. However, the steps involved in preparing the polyether macromonomer are relatively complex. The polycarboxylate water-reducing agent prepared using this polyether macromonomer primarily exhibits improved shrinkage reduction performance.

[0008] The Chinese invention patent with patent publication number CN104371081B discloses a method for preparing a fast-dispersing and viscosity-reducing polycarboxylic acid cement dispersant. The method 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 prepared through ester exchange and toluene is used as a solvent, which is not environmentally friendly.

[0009] A Chinese invention patent, patent publication number CN112707674B, discloses a highly adsorbable, dispersible polycarboxylate water-reducing agent and its preparation method. The agent utilizes a modified polyether macromonomer, an esterified monomer, an alkoxysilane monomer, an unsaturated acid, graphene oxide, an initiator, a chain transfer agent, and a neutralizer. The highly adsorbable, dispersible polycarboxylate water-reducing agent provided by the invention exhibits excellent adsorption and dispersion properties, enabling the polycarboxylate water-reducing agent to form a stable adsorption layer on the surface of cement particles in cement paste. Furthermore, the agent continuously releases carboxyl and silanol groups during cement hydration, resulting in the strongest adsorption effect on cement particles. However, no research has been conducted on the adsorption rate at low temperatures.

[0010] A Chinese invention patent application with publication number CN116376004A discloses a polyether compound, a preparation method thereof, and an application thereof in a slump retaining agent. The polyether compound uses monomethyl allyl glycol ether or propylene glycol monoallyl ether as a starting material. In the presence of a catalyst, ethylene oxide and / or propylene oxide are introduced under anaerobic conditions for heating to carry out a polymerization reaction. After the reaction is completed, propylene oxide is introduced for further polymerization termination. The polyether compound is used to design and synthesize a water-retaining and slurry-enhancing concrete slump retaining agent. The slump retaining agent can achieve long-term slump retention for 4 hours without loss of slump, without bleeding or delayed enlargement during the process, has a water-retaining and slurry-enhancing effect, and good workability. However, there is no mention of its rapid dispersion performance under low temperature conditions.

[0011] Summary of the Invention

[0012] To address the problems of existing polycarboxylate water-reducers mentioned in the background art above: their slow dispersion rate in low-temperature environments, resulting in low concrete production efficiency and a reverse increase in fluidity in the later stages, which affects the quality of concrete projects. Furthermore, existing polycarboxylate water-reducers are highly adsorbed by cement particles in the early stages, which can lead to insufficient adsorption of the water-reducer in the later stages, resulting in poor slump retention. The present invention provides a hydroxyl-terminated polyether macromonomer and an ether-based polycarboxylate water-reducer copolymerized with the hydroxyl-terminated polyether macromonomer. The technical solution is as follows:

[0013] The present invention provides a hydroxyl-terminated polyether macromonomer, the structural formula of which is as follows:

[0014] Wherein, R is an alkylene group having 2 carbon atoms; Y is a polyether chain obtained by polymerization of ethylene oxide; and the B group is a group formed by the ring-opening of the carbon-oxygen bond of the epoxy group of the hydroxyl-terminated monomer;

[0015] The structural formula of the hydroxyl terminated monomer is:

[0016] The R1, R2, and R3 are H or CH3; a and c are integers ranging from 0 to 2, and b is an integer ranging from 1 to 2.

[0017] In one embodiment, the hydroxyl-terminated monomer is one of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol, (3,3-dimethyloxirane)methanol, glycidol, (3,3-dimethyloxirane)methanol, methyl glycidol, and (2S,3S)-(-)-3-propyloxiranemethanol; the Y represents a structure of (A) X A polyether chain, wherein A is a repeating unit of polyoxyethylene and X is an integer of 1 to 100.

[0018] In one embodiment, the weight average molecular weight of the hydroxyl-terminated polyether macromonomer is 600-4000.

[0019] The present invention also provides a method for preparing the hydroxyl-terminated polyether macromonomer as described above, which comprises the following steps:

[0020] Under the action of a catalyst, an unsaturated alcohol as an initiator undergoes a ring-opening polymerization reaction with ethylene oxide to generate a polyether intermediate; the polyether intermediate undergoes a ring-opening reaction with a hydroxyl-terminated monomer to obtain a hydroxyl-terminated polyether macromonomer;

[0021] Wherein, the unsaturated alcohol is ethylene glycol monovinyl ether; the structural formula of the polyether intermediate is: H2C=CH-OROYH;

[0022] The hydroxyl-terminated monomer is one or more combinations of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol, (3,3-dimethyloxirane)methanol, (3,3-dimethyloxirane)methanol, methyl glycidol, and (2S,3S)-(-)-3-propyloxiranemethanol.

[0023] In one embodiment, the molar ratio of the polyether intermediate to the hydroxyl-terminated monomer 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 endpoint is when 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.

[0024] In one embodiment, the catalyst is one or more of sodium hydroxide, potassium hydroxide, lithium aluminum tetrahydride, and metallic sodium.

[0025] The present invention also provides a low-temperature, fast-dispersing ether polycarboxylate water-reducing agent, which is prepared by copolymerization of a hydroxyl-terminated polyether macromonomer, acrylic acid, and a functional monomer C;

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

[0027] Wherein, R4, R5, and R6 are CH3, R7 and R8 are H or CH3, m, n, and p are integers of 0 to 3, and d and e are integers of 0 to 2; the hydroxyl-terminated polyether macromonomer is prepared by the hydroxyl-terminated polyether macromonomer described in any one of claims 1 to 3, or by the preparation method of the hydroxyl-terminated polyether macromonomer described in any one of claims 4 to 5.

[0028] In one embodiment, the functional monomer C is one or more combinations of 3,3-trimethylsilyl dimethacrylate, trimethylsilyl methacrylate, 2-methyl-2-acrylate tributylsilyl ester, trimethylsilyl (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}acrylate, and trimethylsilyl (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}acrylate.

[0029] In one embodiment, 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 for 150-180 min.

[0030] The present invention also provides a method for preparing the low-temperature, fast-dispersing ether-based polycarboxylate water-reducing agent as described above, comprising the following steps:

[0031] The hydroxyl-terminated polyether macromonomer and the solvent are added to a reaction vessel and mixed, and then an oxidant solution, a reducing agent solution, a chain transfer agent solution, acrylic acid, and a functional monomer C solution are added respectively, and a copolymerization reaction is carried out at room temperature for 150 to 180 minutes. After the reaction is completed, the temperature is kept for a period of time, and liquid caustic soda is added to adjust the pH to 6 to 7, thereby obtaining a low-temperature fast-dispersing ether polycarboxylate water-reducing agent.

[0032] In one embodiment, the amount of the oxidizing agent is 0.8% to 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the amount of the reducing agent is 0.8% to 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; and the amount of the chain transfer agent is 0.5% to 2.0% of the total mass of the hydroxyl-terminated polyether macromonomer.

[0033] In one embodiment, the oxidizing agent is one or more combinations of cumene hydroperoxide, hydrogen peroxide, and tert-butyl hydroperoxide; the reducing agent is one or more combinations of sodium hypophosphite, ascorbic acid, and disodium 2-hydroxy-2-sulfonic acid acetate; and the chain transfer agent is one or more combinations of n-butyl mercaptan, mercaptoethanol, mercaptopropionic acid, and trisodium phosphate.

[0034] Based on the above, compared with the prior art, the hydroxyl-terminated polyether macromonomer provided by the present invention and the ether polycarboxylate water-reducing agent synthesized using the hydroxyl-terminated polyether macromonomer have the following beneficial effects:

[0035] The present invention adopts an ether polycarboxylate water reducer prepared from a specific hydroxyl-terminated polyether macromonomer. The adsorption rate and early adsorption amount of the water reducer on the surface of cement particles are significantly improved, and the adsorption amount of the water reducer in the later stage can be maintained at a high level. The cement paste dispersion time using the water reducer is short, and less water reducer is required to achieve the same initial paste fluidity requirements. The water reducer has a fast dispersion speed at low temperatures, good dispersibility, and good slump retention performance.

[0036] Other features and beneficial effects of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood through practice of the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained through the structures particularly pointed out in the description and claims. DETAILED DESCRIPTION

[0037] In order to make the purpose, 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, not all of the embodiments; the technical features designed in the different implementation modes 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 ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] 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 meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in the present invention.

[0039] The present invention also provides the following embodiments and comparative examples:

[0040] Example 1

[0041] (1) Preparation of hydroxyl-terminated polyether macromonomer:

[0042] 73.4 parts of ethylene glycol monovinyl ether and 1.5 parts of potassium hydroxide were added to the first reaction vessel by weight, and the mixture was stirred evenly. The reactor was evacuated to -0.1 MPa and replaced with N2 three times. The reactor was heated to 80°C and 926.6 parts of ethylene oxide were continuously added to the reactor. The reaction temperature was controlled to 120°C and the reaction pressure was 0.5 MPa. After the ethylene oxide was completely added, the reaction was stopped until the reactor pressure no longer decreased to obtain 1000 parts of a polyether intermediate with a molecular weight of 1200.

[0043] Continue to add 172.26 parts of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol to the reactor, control the reaction temperature to 100°C, the reaction pressure to 1 MPa, stop the reaction after 2 hours, add acetic acid to the reaction system to neutralize the mixture until it is neutral, cool to room temperature, and collect the product;

[0044] (2) Preparation of low-temperature fast-dispersing ether polycarboxylate water reducer:

[0045] In parts by weight, 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1) and 105 parts of water were first added to a second reaction vessel and stirred evenly, 1.5 parts of hydrogen peroxide and 20 parts of water were evenly mixed in a first dropping device; 1.5 parts of ascorbic acid, 0.5 parts of mercaptopropionic acid and 20 parts of water were evenly mixed in a second dropping device; 12 parts of acrylic acid, 1 part of 3,3-trimethylsilyl dimethacrylate and 20 parts of water were evenly mixed in a third dropping device; at room temperature, the materials in the first dropping device, the second dropping device and the third dropping device were sequentially 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 150 minutes, and the reaction was carried out at a constant temperature for 30 minutes;

[0046] (3) adding 10 parts by weight of 32% sodium hydroxide to obtain the low-temperature fast-dispersing ether-based polycarboxylate water-reducing agent with a concentration of 40%.

[0047] Example 2

[0048] (1) Preparation of hydroxyl-terminated polyether macromonomer:

[0049] 22.0 parts of ethylene glycol monovinyl ether and 0.8 parts of sodium metal were added to the first reaction vessel by weight, and the mixture was stirred evenly. The reactor was evacuated to -0.1 MPa and replaced with N2 three times. The reactor was heated to 130°C and 977.9 parts of ethylene oxide was continuously added to the reactor. The reaction temperature was controlled to 130°C and the reaction pressure was 0.2 MPa. After the ethylene oxide was completely added, the reaction was stopped until the pressure in the reactor no longer decreased, thereby obtaining 1000 parts of a polyether intermediate with a molecular weight of 4000.

[0050] Continue to add 25.6 parts of (3,3-dimethyloxirane)methanol to the reactor, control the reaction temperature to 110°C, the reaction pressure to 0.6 MPa, stop the reaction after 1 hour, add acetic acid to the reaction system to neutralize the mixture until it becomes neutral, cool to room temperature, and collect the product;

[0051] (2) Preparation of low-temperature fast-dispersing ether polycarboxylate water reducer:

[0052] In parts by weight, 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1) and 100 parts of water are first added to a second reaction vessel and stirred evenly, 2.5 parts of isopropylbenzene hydroperoxide and 20 parts of water are mixed evenly in a first dropping device; 0.8 parts of 2-hydroxy-2-sulfonic acid disodium salt, 2.0 parts of trisodium phosphate and 20 parts of water are mixed evenly in a second dropping device; 8 parts of acrylic acid, 0.5 parts of 3,3-dimethylsilyl trimethylsilyl ester and 20 parts of water are mixed evenly in a third dropping device; at room temperature, the materials in the first dropping device, the second dropping device and the third dropping device are sequentially added dropwise to the second reaction vessel, and the materials in the third dropping device, the second dropping device and the first dropping device are added dropwise over 180 minutes, and the reaction is continued at a constant temperature for 30 minutes;

[0053] (3) adding 10 parts by weight of 32% sodium hydroxide to obtain the low-temperature fast-dispersing ether-based polycarboxylate water-reducing agent with a concentration of 40%.

[0054] Example 3

[0055] (1) Preparation of hydroxyl-terminated polyether macromonomer: 146.8 parts of ethylene glycol monovinyl ether and 2 parts of sodium hydroxide were added to a first reaction vessel by weight, and the mixture was stirred evenly. The reactor was evacuated to -0.1 MPa, and the pressure was replaced with N2 three times. The reactor was heated to 80°C, and 853.1 parts of ethylene oxide was continuously added to the reactor. The reaction temperature was controlled to be 100°C and the reaction pressure was controlled to be 0.6 MPa. After the ethylene oxide was completely added, the reaction was stopped until the pressure in the reactor no longer decreased, and 1000 parts of a polyether intermediate with a molecular weight of 600 were obtained.

[0056] Continue to add 190.9 parts of methyl glycidol to the reactor, control the reaction temperature to 120°C, the reaction pressure to 0.2 MPa, stop the reaction after 3 hours, add acetic acid to the reaction system to neutralize the mixture until it becomes neutral, cool to room temperature, and collect the product;

[0057] (2) Preparation of low-temperature fast-dispersing ether polycarboxylate water reducer:

[0058] In parts by weight, 100 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1), 2.5 parts of sodium hypophosphite and 113 parts of water were first added to a second reaction vessel and stirred evenly. 0.8 parts of tert-butyl hydroperoxide and 20 parts of water were evenly mixed in a first dropping device; 1.3 parts of mercaptoethanol and 20 parts of water were evenly mixed in a second dropping device; 15 parts of acrylic acid, 2 parts of 3,3-trimethylsilyl dimethacrylate and 20 parts of water were evenly mixed in a third dropping device; at room temperature, the materials in the first dropping device, the second dropping device and the third dropping device were sequentially 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 165 minutes, and the reaction was carried out at a constant temperature for 30 minutes;

[0059] (3) adding 10 parts by weight of 32% sodium hydroxide to obtain the low-temperature fast-dispersing ether-based polycarboxylate water-reducing agent with a concentration of 40%.

[0060] Comparative Example 1 (without addition of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol)

[0061] The steps for preparing the low-temperature, fast-dispersing ether-based polycarboxylate water-reducing agent were the same as those in Example 1. When preparing the hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol was not added for end-capping modification. The other steps for preparing the polyether macromonomer were the same as those in Example 1.

[0062] Comparative Example 2 (propylene oxide replaces 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol)

[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 hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol is replaced by propylene oxide.

[0064] Comparative Example 3 (Epoxypropanol instead of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol)

[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 hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol is replaced by propylene oxide.

[0066] Comparative Example 4 (4-hydroxybutyl vinyl ether replaces ethylene glycol monovinyl ether)

[0067] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, with the only difference being that when preparing the hydroxyl-terminated polyether macromonomer, ethylene glycol monovinyl ether is replaced by 4-hydroxybutyl vinyl ether.

[0068] Comparative Example 5 (without adding 3,3-trimethylsilyl dimethacrylate)

[0069] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, except that 3,3-trimethylsilyl dimethacrylate is not added when preparing the ether polycarboxylic acid water reducer.

[0070] Comparative Example 6 (3-(Trimethoxysilyl)propyl acrylate instead of 3,3-trimethylsilyl dimethacrylate)

[0071] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, with the only difference being that when preparing the ether polycarboxylic acid water reducer, 3-(trimethoxysilyl)propyl acrylate of equal mass is used instead of 3,3-trimethylsilyl dimethacrylate.

[0072] Comparative Example 7 (Methacryloxymethyltriethoxysilane instead of 3,3-trimethylsilyl dimethacrylate)

[0073] The steps for preparing the hydroxyl-terminated polyether macromonomer are the same as those in Example 1. When preparing the low-temperature, fast-dispersing ether polycarboxylate water reducer, methacryloxymethyltriethoxysilane is used instead of 3,3-trimethylsilyl dimethacrylate. The other steps for preparing the water reducer are the same as those in Example 1.

[0074] Comparative Example 8 (vinylmethyldimethyloxysilane instead of 3,3-trimethylsilyl dimethacrylate)

[0075] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, with the only difference being that when preparing the ether polycarboxylate water reducer, vinylmethyldimethyloxysilane of equal mass is used instead of 3,3-trimethylsilyl dimethacrylate.

[0076] Comparative Example 9

[0077] Point-TS5 polycarboxylate water reducer is currently available on the market.

[0078] Performance tests of the products of Examples and Comparative Examples:

[0079] (1) Adsorption amount of water-reducing agent product in cement paste

[0080] The low-temperature, fast-dispersing ether polycarboxylate water-reducing agents synthesized in Examples 1 to 3 and the water-reducing agents prepared in Comparative Examples 1 to 9 were tested for adsorption in cement paste using Conch PO52.5R cement. The test method is as follows:

[0081] Take 20g of cement and add it to 40mL of water-reducing agent solution (the solvent of the solution is water, cement and water are stored at 5℃, and the concentration of the water-reducing agent admixture is 4mg·L-1), stir it evenly, take out an appropriate amount of liquid and pour it into a centrifuge tube, use a centrifuge to separate the filtrate (speed of 10000r / min, centrifugation for 2min), collect the supernatant for TOC test, and calculate the adsorption amount on the cement particle surface. The adsorption amount results of 4min and 60min are shown in Table 1.

[0082] The above adsorption test method was used to test the adsorption capacity of the cement paste after it was stirred evenly and left to stand for 0 minutes, 2 minutes, 4 minutes, 8 minutes, 12 minutes, 20 minutes, 40 minutes, and 60 minutes. The experimental results were fitted with a pseudo-first-order kinetic model, and the adsorption rate was calculated based on the fitting results. The adsorption rate results are shown in Table 1:

[0083] Table 1 Sample adsorption amount and adsorption rate

[0084] (2) Flow properties of pure pulp and dispersion time of pure pulp

[0085] Using Conch PO52.5R cement and water stored at 5°C, and following the standard method outlined in GB / T 8077-2012, "Test Method for Homogeneity of Concrete Admixtures," the water reducer dosage was adjusted to achieve an initial paste fluidity of 220±10mm. The water reducer dosage used is shown in Table 3, and the 60-minute paste fluidity is shown in Table 2. At this dosage, the paste mixer adopted a continuous rapid mixing mode, monitoring the paste fluidity at various mixing times. The minimum mixing time at which the cement paste fluidity no longer increased was defined as the paste dispersion time. The results are shown in Table 3.

[0086] Table 2 Flow properties of sample cement paste

[0087] Table 3 Dispersion time of cement paste at 5℃

[0088] Analysis of performance test results of the products of Examples and Comparative Examples

[0089] (1) From the test results in Table 1-3, we can see that:

[0090] After adding the water-reducing agent product prepared by the present invention, not only can the water-reducing agent adsorption rate on the surface of cement particles and the water-reducing agent adsorption amount on the surface of cement particles in the early stage be significantly improved, but also the slurry dispersion time is shortened. It can be seen that the water-reducing agent provided by the present invention has an excellent dispersion speed at low temperatures; and under the same initial slurry fluidity requirements, a smaller amount of water-reducing agent is required, indicating that the product of the present invention has excellent dispersibility and good slump retention performance.

[0091] (2) From the test results of Example 1 and Comparative Examples 1-3, it can be seen that:

[0092] The difference between Comparative Example 1 and Example 1 is that: 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol is not added; the difference between Comparative Example 2 and Example 1 is that propylene oxide is used instead of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol; the difference between Comparative Example 3 and Example 1 is that glycidol is used instead of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol;

[0093] In the embodiment of the present invention, 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol ring-opening polymerization end-capped polyether monomer is used to prepare a water reducer; compared with the solutions of Comparative Examples 1-3, the water reducer prepared in the embodiment has a higher adsorption amount and adsorption rate on the cement surface, and at a lower dosage, the dispersion speed is better at low temperature.

[0094] (3) From the test results of Example 1 and Comparative Example 4, it can be seen that:

[0095] The difference between Comparative Example 4 and Example 1 is that 4-hydroxybutyl vinyl ether is used instead of ethylene glycol monovinyl ether;

[0096] In the embodiment of the present invention, 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol ring-opening polymerization end-capped polyether monomer is used to prepare a water reducer. Compared with the solution of Comparative Example 4, the water reducer prepared in the embodiment has a 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.

[0097] (4) From the test results of Example 1 and Comparative Examples 5-8, it can be seen that:

[0098] The difference between Comparative Example 5 and Example 1 is that no trimethylsilyl 3,3-dimethacrylate is added; the difference between Comparative Example 6 and Example 1 is that 3-(trimethoxysilyl)propyl acrylate is used instead of trimethylsilyl 3,3-dimethacrylate; the difference between Comparative Example 7 and Example 1 is that methacryloxymethyltriethoxysilane is used instead of trimethylsilyl 3,3-dimethacrylate; the difference between Comparative Example 8 and Example 1 is that vinylmethyldimethyloxysilane is used instead of trimethylsilyl 3,3-dimethacrylate;

[0099] The embodiments of the present invention use a specific functional monomer C for the preparation of the water reducer. Compared with the solutions of Comparative Examples 5-8 (without the addition of functional monomer C, or using other existing ester-containing silane monomers and silane monomers without ester groups), the water reducer prepared in the embodiments has a higher adsorption amount and adsorption rate on the cement surface. At a lower dosage, its dispersion speed is better at low temperatures. Compared with the solution without the addition of functional monomer C and silane monomers without ester groups, the product of the embodiment has better slump retention performance.

[0100] Moreover, compared with the commercially available Point-TS5 polycarboxylate water reducer in Comparative Example 9, the water reducer provided in the embodiment of the present invention has a significantly improved water reducer adsorption rate on the cement particle surface and an early water reducer adsorption amount on the cement particle surface, and a shortened slurry dispersion time. Compared with the commercially available polycarboxylate water reducer in Comparative Example 9, the water reducer provided by the present invention has an excellent dispersion speed at low temperatures, and requires a smaller amount of water reducer to achieve the same initial slurry fluidity requirements. The product of the present invention has better dispersibility and better slump retention performance.

[0101] In summary, the low-temperature, fast-dispersing ether-based polycarboxylate water-reducing agent and its preparation method provided by the present invention include at least the following design concepts, action mechanisms, and beneficial effects:

[0102] 1. The present invention uses ethylene glycol monovinyl ether (unsaturated alcohol) as an initiator and a specific hydroxyl-terminated monomer to prepare a hydroxyl-terminated polyether macromonomer, and utilizes the hydroxyl-terminated polyether macromonomer to participate in a copolymerization reaction, so that the molecular structure of the prepared water reducer contains methyl and hydroxyl groups. The introduction of methyl groups into the side chains of the water reducer makes the water reducer more flexible, more easily adheres to the cement surface, and increases the early adsorption capacity, thereby achieving rapid dispersion. The hydroxyl groups chemically react with the surface of cement particles to form hydrogen bonds, which can increase the adsorption between the water reducer and the cement particles, thereby reducing the coagulation between the cement particles and improving the dispersibility of the cement particles.

[0103] 2. The present invention introduces a specific functional monomer C into the water-reducing agent structure for copolymerization with a hydroxyl-terminated polyether macromonomer and acrylic acid, and introduces silicone grease into the water-reducing agent structure. The molecule contains multiple methyl groups, silanol bonds and ester groups. The introduction of multiple methyl groups into the water-reducing agent main chain greatly improves the flexibility of the water-reducing agent, enables the water-reducing agent to be quickly adsorbed on the surface of cement particles, and exhibits a high adsorption rate, thereby achieving rapid dispersion of cement particles under low temperature conditions. The ester group is continuously hydrolyzed under alkaline conditions of cement, and sufficient adsorption group carboxyl groups are supplemented in the later stage, resulting in better slump retention performance of the slurry.

[0104] 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 the production process is safe and pollution-free, making it an environmentally friendly product.

[0105] In summary, the present invention uses an ether polycarboxylate water-reducing agent prepared from a specific hydroxyl-terminated polyether macromonomer, which significantly improves its adsorption rate and early adsorption amount on the surface of cement particles, and the later water-reducing agent adsorption amount can be maintained at a high level. The cement slurry dispersion time using this water-reducing agent is short, and less water-reducing agent is required to achieve the same initial slurry fluidity requirements. The water-reducing agent has a fast dispersion speed at low temperatures, good dispersibility, and good slump retention performance. The solution of the present invention overcomes the problems of existing water-reducing agents such as slow dispersion speed under low temperature conditions, hysteresis amplification problems, and good early dispersion performance but poor later slump retention performance.

[0106] It should be noted that:

[0107] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments of the present invention, but are not intended to limit the present invention. Those skilled in the art may make adaptive adjustments within the scope of the present invention.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, 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. A hydroxyl-terminated polyether macromonomer, characterized in that: The structural formula is as follows: Wherein, R is an alkylene group having 2 carbon atoms; Y is a polyether chain obtained by polymerization of ethylene oxide; and the B group is a group formed by breaking and ring-opening the carbon-oxygen bond of the epoxy group of the hydroxyl-terminated monomer; The structural formula of the hydroxyl-terminated monomer is: The R1, R2, and R3 are H or CH3; a and c are integers between 0 and 2, and b is an integer between 1 and 2.

2. The hydroxyl-terminated polyether macromonomer according to claim 1, characterized in that: The hydroxyl-terminated monomer is one of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol, (3,3-dimethyloxirane)methanol, (3,3-dimethyloxirane)methanol, methyl glycidol, and (2S,3S)-(-)-3-propyloxiranemethanol; The Y represents the structure (A) X A polyether chain, wherein A is a repeating unit of polyoxyethylene and X is an integer of 1 to 100.

3. The hydroxyl-terminated polyether macromonomer according to claim 1, characterized in that: The weight average molecular weight of the hydroxyl-terminated polyether macromonomer is 600-4000.

4. A method for preparing a hydroxyl-terminated polyether macromonomer as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: 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 a hydroxyl-terminated monomer to obtain a hydroxyl-terminated polyether monomer. body; Wherein, the unsaturated alcohol is ethylene glycol monovinyl ether; the structural formula of the polyether intermediate is: H2C=CH-OROYH; The hydroxyl-terminated monomer is one or more combinations of 5-(3,3-dimethyloxirane)-3-methyl-1-pentanol, (3,3-dimethyloxirane)methanol, glycidol, (3,3-dimethyloxirane)methanol, methyl glycidol, and (2S,3S)-(-)-3-propyloxiranemethanol.

5. The method for preparing a hydroxyl-terminated polyether macromonomer according to claim 4, 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 endpoint is when 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.

6. A low-temperature fast-dispersing ether polycarboxylate water-reducing agent, characterized in that: It is formed by copolymerization of hydroxyl-terminated polyether macromonomer, acrylic acid and functional monomer C; Wherein, the structural formula of the functional monomer C is as follows: Wherein, R4, R5, and R6 are CH3, R7 and R8 are H or CH3, m, n, and p are integers of 0 to 3, and d and e are integers of 0 to 2; The hydroxyl-terminated polyether macromonomer is the hydroxyl-terminated polyether macromonomer as described in any one of claims 1 to 3. The polyether macromonomer can be prepared by the method for preparing a hydroxyl-terminated polyether macromonomer as described in any one of claims 4 to 5.

7. The low-temperature fast-dispersing ether polycarboxylate water-reducing agent according to claim 6, characterized in that: The functional monomer C is one or more combinations of 3,3-trimethylsilyl dimethylacrylate, trimethylsilyl methacrylate, 2-methyl-2-acrylate tributylsilyl ester, trimethylsilyl (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}acrylate, and trimethylsilyl (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}acrylate.

8. The low-temperature fast-dispersing ether polycarboxylate water-reducing agent according to claim 6, 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 to 180 minutes.

9. A method for preparing the low-temperature fast-dispersing ether polycarboxylate water-reducing agent according to any one of claims 6 to 8, characterized in that: The following steps are involved: The hydroxyl-terminated polyether macromonomer and the solvent are added to a reaction container and mixed, and then an oxidant solution, a reducing agent solution, a chain transfer agent solution, acrylic acid, and a functional monomer C solution are added respectively, and copolymerization is carried out at room temperature for 150 to 180 minutes; after the reaction is completed, the temperature is kept for a period of time, and liquid alkali is added to adjust the pH to 6 to 7, so as to obtain a low-temperature fast-dispersing ether polycarboxylic acid water-reducing agent.

10. The method for preparing the low-temperature fast-dispersing ether polycarboxylate water-reducing agent according to claim 9, characterized in that: The amount of the oxidant is 0.8% to 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the amount of the reducing agent is 0.8% to 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer; the amount of the chain transfer agent is 0.5% to 2.0% of the total mass of the hydroxyl-terminated polyether macromonomer.

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