A low-temperature rapid-dispersing ester-based polycarboxylate water reducer and its preparation method

Abstract

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

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a low-temperature rapid-dispersing ester polycarboxylate 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 adjustable nature of their molecular structure, where different monomer compositions and polymerization processes can produce products with different properties, polycarboxylate water reducers have great potential for high performance and 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, with the adsorption groups 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 rapid-dispersing polycarboxylate water reducer. After the hydroxyl group at the end of the polyether macromonomer initiates the ring-opening polymerization of glycidyl ether, the in-situ generated terminal hyperbranched polyethylene oxide 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 carboxylic acid small monomers to obtain the rapid-dispersing polycarboxylate water reducer. Organic solvents are used in the preparation process of this polyether macromonomer, which not only has a high cost but also pollutes the environment, and the prepared water reducer only has good dispersion performance at room temperature.

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

[0006] The Chinese invention patent with the patent publication number CN104371081B discloses a preparation method of a fast-dispersing and viscosity-reducing polycarboxylate cement dispersant. It uses a self-made unsaturated macromonomer containing a tertiary amino group as a reducing agent that can participate in polymerization. The weight-average molecular weight of the dispersant is controlled within 20,000 - 100,000. However, the self-made tertiary amino unsaturated monomer is prepared through transesterification, using toluene as a solvent, which has the characteristic of being environmentally unfriendly.

[0007] The Chinese invention patent with the patent publication number CN112707674B 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 CN116376004A 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 ends, 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 return to large phenomena during the process, has the function of water retention and slurry raising, and good workability. However, there is no mention of its fast-dispersing performance at low temperatures. Summary of the Invention

[0009] To solve the problems of the existing polycarboxylate water reducers mentioned in the above background technology: their dispersion speed is relatively slow in low-temperature environments, resulting in low concrete production efficiency and the phenomenon of increased 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 low-temperature fast-dispersing ester-type polycarboxylate water reducer, and its technical solution is as follows:

[0010] This low-temperature fast-dispersing ester-type polycarboxylate water reducer is copolymerized from a hydroxyl-terminated polyether macromonomer, acrylic acid, an ester macromonomer, and functional monomer C through a copolymerization reaction;

[0011] The structural formula of the hydroxyl-terminated polyether macromonomer is as follows:

[0012] ,

[0013] Wherein, 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 of the carbon-oxygen bond of the epoxy group of a hydroxyl-terminated monomer to open the ring;

[0014] The structural formula of the hydroxyl-terminated monomer is:

[0015] ,

[0016] 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.

[0017] In one embodiment, the hydroxyl-terminated monomer is one of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol, (3,3-dimethyloxiranyl)methanol, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyloxirane methanol;

[0018] 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.

[0019] In one embodiment, the weight-average molecular weight of the hydroxyl-terminated polyether macromonomer is 600 to 4000.

[0020] In one embodiment, the preparation process of the hydroxyl-terminated polyether macromonomer:

[0021] 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; wherein, the structural formula of the polyether intermediate is:

[0022] ;

[0023] 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, (3,3-dimethyloxiranyl)methanol, methyloxirane methanol, (2S,3S)-(-)-3-propyloxirane methanol; the unsaturated alcohol is ethylene glycol mono vinyl ether.

[0024] In one embodiment, the mass ratio of the hydroxyl-terminated 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 0.2 - 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 to 120 °C, the reaction pressure is 0.2 to 1.0 MPa, and the reaction time is (1 to 3) h.

[0025] In one embodiment, the catalyst is one or a combination of more of sodium hydroxide, potassium hydroxide, lithium aluminum hydride, and sodium metal.

[0026] In one embodiment, the structural formula of the functional monomer C is as follows:

[0027] ,

[0028] Wherein, R4, R5, and R6 are CH3, R7 and R8 are H or CH3, m, n, and p are integers from 0 to 3, and d and e are integers from 0 to 2;

[0029] The ester macromonomer is one or a combination of more of polyethylene glycol monomethacrylate methoxy ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate methoxy ether, and polyethylene glycol monomethacrylate.

[0030] In one embodiment, the functional monomer C is one or a combination of more of trimethylsilyl 3,3-dimethylacrylate, trimethylsilyl methacrylate, tributylsilyl 2-methyl-2-propenoate, (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}-2-propenoic acid trimethylsilyl ester, (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}-2-propenoic acid trimethylsilyl ester; the molecular weight of the ester macromonomer is 600 to 3000.

[0031] In one embodiment, the mass ratio of the hydroxyl-terminated polyether macromonomer, the ester macromonomer, acrylic acid, and the functional monomer C is 70:30:(6 to 13):(0.5 to 2); the copolymerization reaction is carried out at room temperature, and the reaction time is 150 to 180 min.

[0032] The present invention also provides a preparation method of the low-temperature and rapid-dispersing ester polycarboxylate water reducer as described above, which includes the following steps:

[0033] Add the hydroxyl-terminated polyether macromonomer, ester macromonomer and solvent into a reaction vessel for mixing, then add an oxidant solution, a reductant solution, a chain transfer agent solution, acrylic acid, and a functional monomer C solution respectively, and carry out a copolymerization reaction at room temperature for 150 - 180 min; after the reaction is completed, keep warm at room temperature for a period of time, and add liquid alkali to adjust the pH to 6 - 7 to obtain a low-temperature and fast-dispersing ester polycarboxylate water reducer.

[0034] In one embodiment, the dosage of the oxidant is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer and the ester macromonomer; the dosage of the reductant is 0.8% - 2.5% of the total mass of the hydroxyl-terminated polyether macromonomer and the ester macromonomer; the dosage of the chain transfer agent is 0.5% - 2.0% of the total mass of the hydroxyl-terminated polyether macromonomer and the ester macromonomer.

[0035] In one embodiment, the oxidant is one or a combination of more of cumene hydroperoxide, hydrogen peroxide, and tert-butyl hydroperoxide; the reductant is one or a combination of more of sodium hypophosphite, ascorbic acid, and disodium 2-hydroxy-2-sulfonatoacetate; the chain transfer agent is one or a combination of more of n-butyl mercaptan, mercaptoethanol, mercaptopropionic acid, and trisodium phosphate.

[0036] Based on the above, compared with the prior art, the low-temperature and fast-dispersing ester polycarboxylate water reducer provided by the present invention has the following beneficial effects:

[0037] The low-temperature and fast-dispersing ester polycarboxylate water reducer provided by the present invention has a significantly improved adsorption rate and early adsorption amount on the surface of cement particles, and the later adsorption amount of the water reducer can be maintained at a relatively high level. The net paste dispersion time of the cement using this water reducer is short, and under the requirement of the same initial net paste fluidity, less of this water reducer is needed. This water reducer has a fast dispersion speed and good dispersion performance at low temperature, and good slump retention performance.

[0038] Other features and beneficial effects of the present invention will be described in the subsequent specification, and part of them 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

[0039] 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0040] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains, and should not be construed as limiting 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.

[0041] The present invention also provides the following examples and comparative examples:

[0042] Example 1

[0043] (1) Preparation of hydroxyl-terminated polyether macromonomer:

[0044] By weight, 73.4 parts of ethylene glycol mono vinyl ether and 1 part of metallic sodium were added to the first reaction vessel, stirred evenly, the reaction kettle was evacuated to -0.1 MPa, replaced with N2 three times, the reaction kettle was heated to 80 °C, and 926.6 parts of ethylene oxide were continuously added to the reaction kettle. The reaction temperature was controlled at 110 °C, and the reaction pressure was 0.2 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 1200 was obtained.

[0045] Continuously add 157.8 parts of 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to the reaction kettle, control the reaction temperature at 100 °C, the reaction pressure at 0.6 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;

[0046] (2) Preparation of low-temperature and fast-dispersing ester-type polycarboxylate water reducer:

[0047] By weight, first add 70 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1), 30 parts of polyethylene glycol monoacrylate with a molecular weight of 1200, and 105 parts of water into the second reaction vessel and stir evenly. Mix 1.5 parts of cumene hydroperoxide with 20 parts of water evenly in the first dropping device; mix 0.8 part of ascorbic acid, 2 parts of n-butyl mercaptan with 20 parts of water evenly in the second dropping device; mix 10 parts of acrylic acid, 2 parts of trimethylsilyl dimethacrylate with 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 within 170 min, and carry out a constant-temperature reaction for 30 min;

[0048] Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the low-temperature rapid-dispersing ester-type polycarboxylate water reducer with a concentration of 40% is obtained.

[0049] Example 2

[0050] (1) Preparation of hydroxyl-terminated polyether macromonomer:

[0051] By weight, add 22.0 parts of ethylene glycol mono vinyl ether and 2.5 parts of sodium hydroxide into the 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 977.9 parts of ethylene oxide into the reaction kettle, control the reaction temperature at 100 °C, and the reaction pressure at 0.4 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 4000 is prepared.

[0052] Continue to add 33.2 parts of (3,3-dimethyloxiranyl) methanol into the reaction kettle, control the reaction temperature at 110 °C, and the reaction pressure at 0.2 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;

[0053] (2) Preparation of low-temperature rapid-dispersing ester-type polycarboxylate water reducer:

[0054] By weight, first add 70 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1), 30 parts of polyethylene glycol monomethacrylate with a molecular weight of 600, and 110 parts of water into the second reaction vessel and stir evenly. Mix 2.5 parts of hydrogen peroxide with 20 parts of water evenly in the first dropping device; mix 1.6 parts of disodium 2-hydroxy-2-sulfinoacetate, 1.5 parts of mercaptopropionic acid with 20 parts of water evenly in the second dropping device; mix 13 parts of acrylic acid, 1.2 parts of trimethylsilyl dimethacrylate with 20 parts of water evenly in the third dropping device. At room temperature, start to drop the materials in the first dropping device, the second dropping device and the third dropping device into the second reaction vessel in sequence, and finish dropping the materials in the third dropping device, the second dropping device and the first dropping device respectively in 150 min, and keep the temperature constant for reaction for 30 min;

[0055] Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the low-temperature fast-dispersing ester polycarboxylate water reducer with a concentration of 40% is obtained.

[0056] Example 3

[0057] Preparation of hydroxyl-terminated polyether macromonomer:

[0058] By weight, add 146.8 parts of ethylene glycol mono vinyl ether and 1.5 parts of lithium aluminum tetrahydride into the 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 to continuously add 853.1 parts of ethylene oxide into the reaction kettle, control the reaction temperature at 120 °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 1000 parts of polyether intermediate with a molecular weight of 600 are prepared.

[0059] Continue to add 146.8 parts of methyl glycidol into the reaction kettle, control the reaction temperature at 120 °C and the reaction pressure at 1 MPa, stop the reaction after 1 h, add acetic acid to neutralize the reaction system until the mixture is neutral, cool to room temperature, and collect the product.

[0060] Preparation of low-temperature fast-dispersing ester polycarboxylate water reducer:

[0061] By weight, first add 70 parts of the hydroxyl-terminated polyether macromonomer prepared in step (1), 30 parts of methoxy ether polyethylene glycol monomethacrylate with a molecular weight of 3000, 2.5 parts of sodium hypophosphite, and 95 parts of water into the second reaction vessel and stir evenly. Mix 0.8 parts of tert-butyl hydroperoxide with 20 parts of water evenly in the first dropping device; mix 0.5 parts of mercaptoethanol with 20 parts of water evenly in the second dropping device; mix 6 parts of acrylic acid, 0.5 parts of trimethylsilyl 3,3-dimethylacrylate with 20 parts of water evenly in the third dropping device. At room temperature, start dropping the materials in the first dropping device, the second dropping device, and the third dropping device into the second reaction vessel in sequence, and finish dropping the materials in the third dropping device, the second dropping device, and the first dropping device respectively in 180 min, and keep the temperature constant for reaction for 30 min;

[0062] Add 10 parts of sodium hydroxide with a mass concentration of 32% by weight, and the low-temperature fast-dispersing ester polycarboxylate water reducer with a concentration of 40% is obtained.

[0063] Comparative Example 1 (without adding 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0064] The steps for preparing the water reducer 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.

[0065] Comparative Example 2 (propylene oxide replaces 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0066] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, and the only difference is 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 3 (propylene glycol replaces 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol)

[0068] The steps and conditions for preparing the water reducer in this comparative example are the same as those in Example 1, and the only difference is that when preparing the hydroxyl-terminated polyether macromonomer, 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol is replaced with propylene oxide in equal mass.

[0069] Comparative Example 4 (4-hydroxybutyl vinyl ether replaces ethylene glycol mono vinyl ether)

[0070] 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, ethylene glycol mono vinyl ether is replaced with 4-hydroxybutyl vinyl ether in equal mass.

[0071] Comparative Example 5 (without 3,3-trimethylsilyl dimethacrylate)

[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 ester-type polycarboxylate water reducer, 3,3-trimethylsilyl dimethacrylate is not added.

[0073] Ester-type polycarboxylate water reducer

[0074] Comparative Example 6 (3-(trimethoxysilyl)propyl acrylate replaces 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, except that: when preparing the ester-type polycarboxylate water reducer, 3-(trimethoxysilyl)propyl acrylate is used to replace 3,3-trimethylsilyl dimethacrylate in equal mass.

[0076] Comparative Example 7 (methacryloyloxymethyltriethoxysilane replaces 3,3-trimethylsilyl dimethacrylate)

[0077] The steps for preparing the hydroxyl-terminated polyether macromonomer are the same as those in Example 1. When preparing the low-temperature and rapid-dispersion type ester-type polycarboxylate water reducer, methacryloyloxymethyltriethoxysilane is used to replace 3,3-trimethylsilyl dimethacrylate, and the other steps for preparing the water reducer are the same as those in Example 1.

[0078] Comparative Example 8 (vinylmethyldimethoxysilane replaces 3,3-trimethylsilyl dimethacrylate)

[0079] 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 ester-type polycarboxylate water reducer, vinylmethyldimethoxysilane is used to replace 3,3-trimethylsilyl dimethacrylate in equal mass.

[0080] Comparative Example 9

[0081] Commercially available Point-TS5 type polycarboxylate water reducer.

[0082] Performance tests on the products of the examples and comparative examples:

[0083] (1) Adsorption amount of the water reducer product in cement paste

[0084] The low-temperature rapid-dispersing ester-based polycarboxylate water reducer synthesized in Examples 1-3 and the water reducers prepared in Comparative Examples 1-9 were used to test the adsorption amount of the above water reducer products in cement paste with Huailuo PO52.5R cement. The test method is as follows:

[0085] 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 admixture is 4 mg∙L -1 ), stir evenly, take out 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 cement particles. The adsorption amount results at 4 min and 60 min are shown in Table 1.

[0086] Using the above adsorption amount test method, 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 was stirred evenly were tested respectively. And the pseudo-first-order kinetic model was used to fit the experimental results, and the adsorption rate was calculated according to the fitting results. Among them, the adsorption rate results are shown in Table 1:

[0087] Table 1 Adsorption amount and adsorption rate of samples

[0088]

[0089] (2) Fluidity of cement paste and dispersion time of cement paste

[0090] Using Huailuo 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 reached 220±10 mm. The dosages of the water reducers 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, and the fluidity of the cement paste at different stirring times is monitored. 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.

[0091] Table 2 Fluidity of cement paste of samples

[0092]

[0093] Table 3 Dispersion time of cement paste at 5°C of samples

[0094]

[0095] Analysis of the performance test results of the products in the examples and comparative examples

[0096] (1)It can be seen from the test results in Table 1-3 that:

[0097] After adding the water reducer product prepared by 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 required, indicating that the product of the present invention has excellent dispersion performance and good slump retention performance.

[0098] (2)It can be seen from the test results of Example 1 and Comparative Examples 1-3 that:

[0099] The difference between Comparative Example 1 and Example 1 is that it does not add 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol; the difference between Comparative Example 2 and Example 1 is that it uses propylene oxide to replace 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol; the difference between Comparative Example 3 and Example 1 is that it uses propylene glycol to replace 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol;

[0100] The present invention's example uses 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to open-loop polymerize and cap the polyether monomer for the preparation of the water reducer; compared with the schemes of Comparative Examples 1-3, 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.

[0101] (3)It can be seen from the test results of Example 1 and Comparative Example 4 that:

[0102] The difference between Comparative Example 4 and Example 1 is that it uses 4-hydroxybutyl vinyl ether to replace ethylene glycol mono vinyl ether;

[0103] The present invention's example uses 5-(3,3-dimethyloxiranyl)-3-methyl-1-pentanol to open-loop polymerize and cap the polyether monomer for the preparation of the water reducer. Compared with the scheme of Comparative Example 4, the water reducer prepared in the example has higher adsorption amount and adsorption rate on the cement surface, at a lower dosage, it has better dispersion speed at low temperature and better slump retention performance.

[0104] (4)It can be seen from the test results of Example 1 and Comparative Examples 5-8 that:

[0105] 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.

[0106] In the examples of the present invention, a specific functional monomer C is used for the preparation of water reducing agents. Compared with the schemes of Comparative Examples 5-8 (without adding functional monomer C, or using other existing silane monomers containing ester groups and silane monomers without ester groups), the water reducing agents prepared in the examples have higher adsorption amounts and adsorption rates on the cement surface. At a lower dosage, their dispersion speed is better at low temperatures. Compared with not adding functional monomer C and silane monomers without ester groups, the products of the examples have better slump retention performance.

[0107] Moreover, compared with the commercially available Point-TS5 polycarboxylate water reducing agent in Comparative Example 9, the water reducing agent provided in the examples of the present invention has significantly increased 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, and the net paste dispersion time is shortened; compared with the commercially available polycarboxylate water reducing agent in Comparative Example 9, the water reducing agent provided in the present invention has better dispersion speed at low temperatures, and requires less dosage of the water reducing agent to meet the same initial net paste fluidity requirement. The product of the present invention has better dispersion performance and better slump retention performance.

[0108] In summary, the low-temperature rapid-dispersing ester polycarboxylate water reducing agent and its preparation method provided by the present invention at least include the following design concepts, action mechanisms and beneficial effects:

[0109] 1. The present invention uses ethylene glycol mono vinyl ether (unsaturated alcohol) initiator and specific hydroxyl-terminated monomers to prepare hydroxyl-terminated polyether macromonomers, and uses the hydroxyl-terminated polyether macromonomers to participate in copolymerization reactions, so that the molecular structure of the prepared water reducing agent contains methyl and hydroxyl 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, thereby achieving rapid dispersion; while the hydroxyl group reacts chemically with the surface of cement particles to form hydrogen bonds, which can increase the adsorption between the water reducing agent and cement particles, thereby reducing the coagulation between cement particles and improving the dispersion performance of cement particles;

[0110] 2. The present invention introduces a specific functional monomer C into a copolymerization reaction with a hydroxyl-terminated polyether macromonomer and acrylic acid, introducing silicone grease into the superplasticizer structure. The molecule has multiple methyl groups, silicon-oxygen bonds, and ester groups. The introduction of multiple methyl groups into the main chain of the superplasticizer greatly improves the flexibility of the superplasticizer, enabling the superplasticizer 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 carboxyl groups as adsorption groups in the later stage, and the slump retention performance of the slurry is good.

[0111] 3. The preparation method of the superplasticizer provided by the present invention has simple process operation, mild reaction conditions, is easy to scale up production, and is safe and pollution-free in the production process, belonging to an environmental protection product.

[0112] 4. The present invention adopts the copolymerization method of ester-ether macromonomers (introducing polyether macromonomers and ester macromonomers). Compared with simply using ether macromonomers, the prepared superplasticizer product has a faster dispersion speed and better slump retention performance under low-temperature conditions.

[0113] In summary, for the ester-based polycarboxylate superplasticizer provided by the present invention, the adsorption rate and early adsorption amount on the surface of cement particles are significantly improved, and the later adsorption amount of the superplasticizer can be maintained at a high level. The net paste dispersion time of the cement using this superplasticizer is short, and when the same initial net paste fluidity requirement is met, less of this superplasticizer is needed. This superplasticizer 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 lagging amplification of existing superplasticizers under low-temperature conditions, as well as good early dispersion performance and poor later slump retention performance.

[0114] It should be noted that:

[0115] 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.

[0116] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limitations thereto; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-temperature and rapid-dispersing ester-type polycarboxylate water reducer, characterized in that: It is copolymerized from a hydroxyl-terminated polyether macromonomer, acrylic acid, an ester macromonomer, and a functional monomer C through a copolymerization reaction; The structural formula of the hydroxyl-terminated polyether macromonomer is as follows: ， Among them, R is an alkylene group with 2 carbon atoms; 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; The functional monomer C is one or a combination of more than one of 3,3-dimethylacryloyloxytrimethylsilane, trimethylacryloyloxytrimethylsilane, tributylsilyl 2-methyl-2-propenoate, (2E)-3-{4-[(trimethylsilyl)oxy]phenyl}acryloyloxytrimethylsilane, (2E)-3-{3-[(trimethylsilyl)oxy]phenyl}acryloyloxytrimethylsilane; 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 wherein A is a repeating unit of polyoxyethylene, X is an integer from 1 to 100, and X is not 1; The ester macromonomer is one or a combination of more than one of methoxypolyethylene glycol monoacrylate, polyethylene glycol monoacrylate, methoxypolyethylene glycol monoacrylate, polyethylene glycol monomethacrylate.

2. The low-temperature rapid-dispersing ester polycarboxylate water reducer according to claim 1, characterized in that: The weight-average molecular weight of the hydroxyl-terminated polyether macromonomer is 600 - 4000.

3. The low-temperature rapid-dispersing ester-type polycarboxylate water reducer according to claim 1, characterized in that: The preparation process of the hydroxyl-terminated polyether macromonomer: 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; Among them, 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; The unsaturated alcohol is ethylene glycol mono vinyl ether.

4. The low-temperature rapid-dispersing ester-based polycarboxylate water reducer 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 - 120 °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. The low-temperature rapid-dispersing ester-based polycarboxylate superplasticizer according to claim 1, wherein: The molecular weight of the ester macromonomer is 600 - 3000.

6. The low-temperature rapid-dispersing ester-based polycarboxylate water reducer according to claim 1, characterized in that: The mass ratio of the hydroxyl-terminated polyether macromonomer, ester macromonomer, acrylic acid, and functional monomer C is 70:30:(6 - 13):(0.5 - 2); The copolymerization reaction is carried out at room temperature, and the reaction time is 150 - 180 min.

7. A preparation method of the low-temperature and rapid-dispersing ester polycarboxylate water reducer according to any one of claims 1-6, characterized in that, It includes the following steps: Add the hydroxyl-terminated polyether macromonomer, ester macromonomer and solvent into a reaction vessel for mixing, and 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 at room temperature for a period of time, and add liquid alkali to adjust the pH to 6 - 7 to obtain a low-temperature and fast-dispersing ester-based polycarboxylate water reducer.

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

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