A super-retarded setting ester-based polycarboxylate superplasticizer and its preparation method

Abstract

This application relates to the field of concrete admixtures, and particularly to a super-retarded-setting ester-based polycarboxylate superplasticizer and its preparation method. This super-retarded-setting ester-based polycarboxylate superplasticizer is polymerized from comonomers under the action of an initiator, chain transfer agent, and emulsifier; the comonomers include ester macromonomers, polyoxyalkyl ethers containing ester groups and rigid benzene ring structures, ester micromonomers, and unsaturated acids. This super-retarded-setting ester-based polycarboxylate superplasticizer effectively improves the initial dispersion and slump retention properties of concrete, increases concrete strength, reduces concrete sensitivity, and has a good long-term slump retention effect. Furthermore, this super-retarded-setting ester-based polycarboxylate superplasticizer can be prepared at room temperature, with mild reaction conditions, effectively saving energy.

Description

Technical Field

[0001] This application relates to the field of concrete admixtures, and in particular to an ultra-retarded setting ester polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] With the increasing demand for high-performance concrete in the construction industry, traditional water-reducing agents can no longer meet the requirements of modern engineering. Polycarboxylate superplasticizers have become the preferred high-performance concrete admixtures in the construction industry today due to their high water-reduction and high slump retention properties. However, some existing water-reducing agents, while providing good water-reduction effects, fail to maintain good slump retention. Therefore, developing a long-slump-retention polycarboxylate superplasticizer that can slowly release carboxyl groups and maintain good concrete workability is particularly important.

[0003] In the synthesis of polycarboxylate superplasticizers, the reactivity of the polyether macromonomers determines the reaction temperature. 4-carbon and 5-carbon superplasticizers (synthesized using 4-carbon or 5-carbon terminal olefin initiators) are currently the mainstream polycarboxylate superplasticizers, accounting for a large proportion, but their reaction temperature is as high as 60℃, requiring heating equipment. 2+2 and 2+4 superplasticizers, due to their shorter reaction time and superior water reduction and slump retention properties, are also currently accepted in the market, but their macromonomers have higher reactivity, requiring low-temperature equipment. Both types have high production costs, which does not meet the requirements of energy conservation and environmental protection. Therefore, developing a polycarboxylate superplasticizer that can be synthesized under room temperature conditions is of great significance.

[0004] For example, Chinese invention patent application CN 118580021 A discloses a method for synthesizing isopentenyl alcohol polyoxyethylene ether water-reducing agent, which requires high-temperature preparation and consumes a large amount of energy. Chinese invention patent application CN118620143A discloses a long-lasting slump-retaining polycarboxylate high-performance water-reducing agent and its preparation method, which introduces a comb-like structure but does not exhibit step-hydrolyzed ester groups, resulting in poor stability of its slump-retaining properties. Summary of the Invention

[0005] To address the shortcomings of existing polycarboxylate superplasticizers mentioned in the background section, this application provides a super-retarded setting ester-based polycarboxylate superplasticizer, the technical solution of which is as follows:

[0006] The super-retarded setting type ester polycarboxylate superplasticizer provided in this application is polymerized by comonomers under the action of an initiator, a chain transfer agent, and an emulsifier; the comonomers include ester macromonomers, polyoxyalkyl ethers containing ester groups and rigid benzene ring structures, ester small monomers, and unsaturated acids; wherein, the structural formula of the polyoxyalkyl ethers containing ester groups and rigid benzene ring structures is as follows:

[0007] ,

[0008] Wherein, R1 is an alkylene group having 1 or 2 carbon atoms; N1 is an epoxy alkyl group containing an ester group and a rigid benzene ring structure;

[0009] The structural formula of the ester monomer is as follows:

[0010] In this case, R2 is an alkylene group having 1 to 5 carbon atoms.

[0011] In some embodiments, the structure of N1 is as follows:

[0012] ,or ;

[0013] Where n is 4 to 18.

[0014] In some embodiments, the polyoxyalkyl ether containing ester groups and a rigid benzene ring structure is prepared by ring-opening polymerization of an unsaturated alcohol and an epoxy ester compound under the action of a catalyst; wherein the unsaturated alcohol is diethylene glycol monoallyl ether or diethylene glycol monovinyl ether; the epoxy ester compound is 2,3-epoxypropylbenzoate or methyl 3,3-diphenyl-2,3-epoxypropionate; the molar ratio of the unsaturated alcohol to the epoxy ester compound is 1:(6-18); the ring-opening polymerization reaction temperature is 100℃-180℃, the reaction time is 4-6h, and the reaction pressure is 0.3MPa-0.5MPa.

[0015] The structural formula of 2,3-epoxypropylbenzoate is:

[0016]

[0017] The structure of methyl 3,3-diphenyl-2,3-epoxypropionate is as follows:

[0018] .

[0019] In some embodiments, the catalyst is one or more combinations of potassium hydroxide, sodium ethoxide, sodium hydride, potassium hydride, and potassium hydroxide.

[0020] In some embodiments, the mass ratio of the ester monomer, the ester macromonomer, the polyoxyalkylene ether containing the ester group and the rigid benzene ring structure, and the unsaturated acid is (1.8-6):100:(10-16):(4-13); the polymerization reaction temperature is 25℃-35℃, and the reaction time is 0.5h-1.5h.

[0021] In some embodiments, the ester macromonomer is one or more combinations of polyethylene glycol dimethacrylate with a molecular weight of 1500-5000, polyethylene glycol monomethyl ether acrylate with a molecular weight of 1500-5000, polyethylene glycol acrylate with a molecular weight of 1500-5000, polyethylene glycol monomethoxy ether monoacrylate with a molecular weight of 1500-5000, and polyethylene glycol monomethoxy ether monomethacrylate with a molecular weight of 1500-5000.

[0022] In some embodiments, the unsaturated acid is one or more combinations of acrylic acid, methacrylic acid, and maleic acid.

[0023] In some embodiments, the initiator comprises an oxidant and a reducing agent; the oxidant is one or more combinations of potassium persulfate, hydrogen peroxide, and 2,5-dimethyl-2,5-bis(hydrogen peroxide)hexane; the reducing agent is one or more combinations of sodium hypophosphite, sodium sulfite, ferrous sulfate, and potassium thiosulfate; the chain transfer agent is one or more combinations of mercaptoacetic acid, 2-hydroxypropanethiol, 2-mercaptosuccinic acid, and sodium hypophosphite; and the emulsifier is one or more combinations of sorbitol polyoxyethylene ether tetraoleate and stearic acid polyoxyethylene ester.

[0024] In some embodiments, the amount of oxidant is 1% to 2.5% of the total mass of the ester macromonomers, the amount of reducing agent is 0.8% to 2.8% of the total mass of the ester macromonomers, the amount of chain transfer agent is 0.5% to 2% of the total mass of the ester macromonomers, and the amount of emulsifier is 1% to 4% of the total mass of the ester macromonomers.

[0025] This application also provides a method for preparing the super-retarded setting type ester polycarboxylate superplasticizer as described above, which includes the following preparation steps: mixing the ester monomer, the ester macromonomer and the polyoxyalkyl ether containing ester groups and rigid benzene ring structures, adding an initiator solution, a chain transfer agent solution, an emulsifier solution and an unsaturated acid at 25℃~35℃ to carry out a polymerization reaction, the addition time being 0.5h~1.5h; then keeping at the temperature for a certain period of time, adjusting the pH, and obtaining the super-retarded setting type ester polycarboxylate superplasticizer.

[0026] Compared with the prior art, this application has the following advantages:

[0027] This application provides a super-retarded-setting ester-based polycarboxylate superplasticizer. Due to the introduction of slow-release groups on its side chains, it provides a more steric adsorption effect. The ester side chains slowly release the adsorbed groups, providing long-lasting slump retention and improving the later-stage strength of concrete. This super-retarded-setting ester-based polycarboxylate superplasticizer effectively improves the initial dispersion and slump retention properties of concrete, increases concrete strength, and reduces concrete sensitivity, exhibiting excellent long-lasting slump retention. Furthermore, this super-retarded-setting ester-based polycarboxylate superplasticizer can be prepared at room temperature, with mild reaction conditions, effectively saving energy. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] This application also provides the following embodiments and comparative examples:

[0030] Example 1

[0031] (1) Preparation of polyoxyalkyl ethers containing ester groups and rigid benzene ring structures: 29.2 parts by weight of diethylene glycol monoallyl ether and 1.7 parts by weight of sodium ethoxide were added to a 3L stainless steel high-pressure reactor and stirred until homogeneous. The reactor was evacuated and replaced with N2 four times. The reactor was heated to 90℃, and 213.8 parts by weight of 2,3-epoxypropylbenzoate were continuously added to the reactor. The reaction temperature was controlled at 110℃ and the reaction pressure at 0.5 MPa. The reaction time was 5.5 h. After the product cooled, a neutralizing agent was added, and the product was collected.

[0032] (2) Copolymerization reaction: By weight, first add 4 parts of 2-(4-pentene)malonide diethyl ester, 12 parts of polyoxyalkylene polyether containing ester group and rigid benzene ring structure, 100 parts of polyethylene glycol acrylate, 2.8 parts of sodium hypophosphite solution, 1 part of sorbitol polyoxyethylene ether tetraoleate and 68.2 parts of water to the first reaction vessel and stir evenly;

[0033] One part hydrogen peroxide and 20 parts water are mixed evenly in the first adding device; two parts mercaptoacetic acid and 20 parts water are mixed evenly in the second adding device; eight parts acrylic acid and 20 parts water are mixed evenly in the third adding device.

[0034] At room temperature of 25℃~35℃, the materials from the first dropping device, the second dropping device, and the third dropping device are added dropwise to the first reaction vessel in sequence. The materials from the third dropping device, the second dropping device, and the first dropping device are added dropwise in 60 minutes, and the reaction is carried out at a constant temperature for 1 hour.

[0035] The polyethylene glycol acrylate (with 56 repeating segments) has a molecular weight of 2536 and its structural formula is: H2C=CHCO(OCH2CH2). 56 OH.

[0036] (3) Add 10 parts by weight of sodium hydroxide with a mass concentration of 32% to obtain a 50% concentration of super-retarded setting type ester polycarboxylate superplasticizer.

[0037] Example 2

[0038] (1) Preparation of polyoxyalkyl ethers containing ester groups and rigid benzene ring structures: 100.2 parts by weight of diethylene glycol monovinyl ether and 1.4 parts by weight of sodium hydride were added to a 3L stainless steel high-pressure reactor and stirred until homogeneous. The reactor was evacuated and replaced with N2 four times. The reactor was heated to 140℃, and 1748.6 parts by weight of methyl 3,3-diphenyl-2,3-epoxypropionate were continuously added to the reactor. The reaction temperature was controlled at 160℃ and the reaction pressure at 0.3 MPa. The reaction time was 4 hours. After the product cooled, a neutralizing agent was added, and the product was collected.

[0039] (2) Copolymerization reaction: By weight, 6 parts of diethyl 2-(4-propylene)malonate, 14 parts of polyoxyalkylene polyether containing ester group and rigid benzene ring structure, 100 parts of polyethylene glycol monomethoxy ether monoacrylate, 1.5 parts of sodium sulfite, 4 parts of polyoxyethylene stearate and 68.8 parts of water are added to the first reaction vessel and stirred evenly.

[0040] 2.4 parts potassium persulfate and 20 parts water are mixed evenly in the first adding device; 0.5 parts 2-hydroxypropanethiol and 20 parts water are mixed evenly in the second adding device; 4 parts methacrylic acid and 20 parts water are mixed evenly in the third adding device.

[0041] At room temperature of 25℃~35℃, the materials from the first dropping device, the second dropping device, and the third dropping device are added dropwise to the first reaction vessel in sequence. The materials from the third dropping device, the second dropping device, and the first dropping device are added dropwise in 75 minutes, and the reaction is carried out at a constant temperature for 1 hour.

[0042] The molecular weight of polyethylene glycol monomethoxy ether monoacrylate is 3000.

[0043] (3) Add 10 parts by weight of sodium hydroxide with a mass concentration of 32% to obtain the super-retarded setting type ester polycarboxylate superplasticizer with a concentration of 40%.

[0044] Example 3

[0045] (1) Preparation of polyoxyalkyl ethers containing ester groups and rigid benzene ring structures: 50.6 parts by weight of diethylene glycol monovinyl ether and 0.9 parts by weight of potassium hydride were added to a 3L stainless steel high-pressure reactor and stirred until homogeneous. The reactor was evacuated and replaced with N2 four times. The reactor was heated to 110℃, and 1226.4 parts by weight of 2,3-epoxypropylbenzoate were continuously added to the reactor. The reaction temperature was controlled at 130℃ and the reaction pressure at 0.4 MPa. The reaction time was 4.5 h. After the product cooled, a neutralizing agent was added, and the product was collected.

[0046] (2) Copolymerization reaction: By weight, first add 2 parts of 2-(4-pentene)malonide diethyl ester, 10 parts of polyoxyalkylene polyether containing ester group and rigid benzene ring structure, 100 parts of polyethylene glycol monomethyl ether acrylate, 3 parts of sorbitol polyoxyethylene ether tetraoleate and 66.5 parts of water to the first reaction vessel and stir evenly.

[0047] 1.2 parts of 2,5-dimethyl-2,5-bis(hydrogen peroxide)hexane and 20 parts of water are mixed evenly in the first dropping device; 0.9 parts of potassium thiosulfate, 1 part of sodium hypophosphite and 20 parts of water are mixed evenly in the second dropping device; 12 parts of acrylic acid and 20 parts of water are mixed evenly in the third dropping device.

[0048] At room temperature of 25℃~35℃, the materials from the first dropping device, the second dropping device, and the third dropping device are added dropwise to the first reaction vessel in sequence. The materials from the third dropping device, the second dropping device, and the first dropping device are added dropwise in 90 minutes, and the reaction is carried out at a constant temperature for 1 hour.

[0049] The molecular weight of polyethylene glycol monomethyl ether acrylate is 4000.

[0050] (3) Add 10 parts by weight of sodium hydroxide with a mass concentration of 32% to obtain the super-retarded setting type ester polycarboxylate superplasticizer with a concentration of 40%.

[0051] Comparative Example 1 (4-hydroxybutyl vinyl ether substituted with diethylene glycol monoallyl ether)

[0052] The only difference from Example 1 is that in the preparation of polyoxyalkyl ether containing ester group and rigid benzene ring structure in step (1), 4-hydroxybutyl vinyl ether is used in equimolar amount to replace diethylene glycol monoallyl ether, and the other steps and conditions are the same as in Example 1.

[0053] Comparative Example 2 (using ethylene glycol monovinyl ether in equimolar substitution for diethylene glycol monoallyl ether)

[0054] The only difference from Example 1 is that in the preparation of polyoxyalkyl ethers containing ester groups and rigid benzene ring structures in step (1), ethylene glycol monovinyl ether is used in equimolar amounts to replace diethylene glycol monoallyl ether, while the other steps and conditions are the same as in Example 1.

[0055] Comparative Example 3 (Equal mass substitution of ester macromonomers for polyether macromonomers)

[0056] The only difference from Example 1 is that in the copolymerization reaction of step (2), polyether macromonomer TPEG polyether is used to replace polyethylene glycol acrylate by the same mass, while the other steps and conditions are the same as in Example 1.

[0057] The molecular weight of the polyether macromonomer TPEG polyether is 2507 (with 55 repeating fragments), and its structural formula is: CH2=CH(CH3)CH2CH2O(CH2CH2O). n H, where n=55.

[0058] Comparative Example 4 (Copolymerization reaction without ester groups or rigid benzene ring structures involving polyoxyalkyl ethers)

[0059] The only difference from Example 1 is that in the copolymerization reaction of step (2), no polyoxyalkylene ether containing ester group and rigid benzene ring structure was added to participate in the copolymerization reaction. The other steps and conditions are the same as in Example 1.

[0060] Comparative Example 5

[0061] Commercially available Point-S type polycarboxylate superplasticizer mother liquor and white sugar were mixed at 0.2% and 0.03% of the cementitious material, respectively, for concrete verification.

[0062] Comparative Example 6 (no ester monomers involved in the copolymerization reaction)

[0063] The only difference from Example 1 is that no ester monomers are added in the copolymerization reaction of step (2). The other steps and conditions are the same as in Example 1.

[0064] Comparative Example 7 (hydroxyethyl acrylate replacing the ester monomer 2-(4-pentene)malonate)

[0065] The only difference from Example 1 is that in the copolymerization reaction of step (2), hydroxyethyl acrylate is used in place of diethyl 2-(4-pentene)malonate by mass. The other steps and conditions are the same as in Example 1.

[0066] Comparative Example 8 (Methyl 2,3-epoxypropionate substituted with 2,3-epoxypropylbenzoate)

[0067] The only difference from Example 1 is that in step (1), methyl 2,3-epoxypropionate is used in place of 2,3-epoxypropylbenzoate in equal molar amounts. The other steps and conditions are the same as in Example 1.

[0068] Comparative Example 9 (Equimolarly substituted 2-(4-pentene)malonic acid diethyl ester of methyl 6-heptenoate)

[0069] The only difference from Example 1 is that in the copolymerization reaction of step (2), methyl 6-heptenoate is used to replace diethyl 2-(4-pentene)malonate by mass. The other steps and conditions are the same as in Example 1.

[0070] Performance testing of the products in the examples and comparative examples:

[0071] The polycarboxylate superplasticizers synthesized in the examples and comparative examples were compared with those synthesized in manufactured sand concrete: Conch PO42.5R cement was used. The superplasticizer dosage in Examples 1-3 was 0.2% (converted to solids) of cementitious materials. The superplasticizer dosage in Comparative Examples 1-4 and Comparative Example 6 was 0.2% (converted to solids) of cementitious materials. The admixture dosage in Comparative Example 5 was based on the specific compound formulation.

[0072] According to GB 8076-2008 "Concrete Admixtures", its slump, spread, etc., are measured. The standard concrete mix proportion is: cement 285 kg / m³. 3 63 kg / m³ of fly ash 3 Mineral powder 60kg / m 3 825 kg / m³ of manufactured sand 3 1013 kg / m³ of gravel 3 The baseline sample did not contain any admixtures. Examples 1-3 and Comparative Examples 1-9 were tested using the baseline mix proportions. The concrete test results are shown in Table 1.

[0073] Table 1

[0074]

[0075] The results in Table 1 show that:

[0076] Based on the experimental results, it can be found that the product of this application performs well in improving the initial dispersion and slump retention of concrete, while also enhancing the strength of concrete and reducing its sensitivity. In particular, the effects of Examples 1 to 3 are particularly significant in reducing the loss of concrete slump and spread after 4 hours, showing that the product of this application has a significant and long-lasting slump retention effect.

[0077] As can be seen from Example 1 and Comparative Examples 1-2, compared with the comparative examples that used 4-hydroxybutyl vinyl ether and ethylene glycol monovinyl ether as initiators to prepare polyether macromonomers, this application uses a specific structured unsaturated alcohol, which has a significant improvement in the initial water-reducing performance of concrete.

[0078] Comparing Example 1 with Comparative Examples 1-2, it can be found that compared with the use of 4-hydroxybutyl vinyl ether and ethylene glycol monovinyl ether, the specific unsaturated alcohol with a specific structure used in this application as an initiator can significantly improve the initial water-reducing performance of concrete when preparing polyether macromonomers.

[0079] Compared with Comparative Example 1 and Comparative Example 3, and compared with the polycarboxylate superplasticizer prepared by copolymerization using 5-carbon polyether, the superplasticizer prepared by copolymerization using specific ester macromonomers in this application has a significant improvement in slump retention performance after 4 hours.

[0080] By comparing Example 1 with Comparative Example 4, it can be found that if polyoxyalkylene ethers containing ester groups and rigid benzene ring structures are not used for polymerization, the slump retention of concrete will decrease, and the strength of concrete will also decrease slightly.

[0081] As can be seen from Example 1 and Comparative Example 5, compared with the existing method of using water-reducing agents combined with retarders, the concrete water-reducing agent prepared by the present application, which consists of ester macromonomers, polyoxyalkyl ethers containing ester groups and rigid benzene ring structures, and ester monomers, not only has better water-reducing performance but also significantly improved slump retention performance and can enhance the early strength of concrete.

[0082] When comparing Example 1 with Comparative Examples 6 and 7, it is evident that the specific ester monomers selected in this application exhibit superior slump retention and concrete strength enhancement capabilities, even without the addition of ester monomers or when using other types of ester monomers. Specifically, after 2 hours, the ester monomers of this application still maintain good workability, while the other two monomers exhibit poor workability.

[0083] By comparing Example 1 with Comparative Example 8, we found that after hydrolysis, the adsorption groups of the water-reducing agent in Comparative Example 8 are easily blocked by the surrounding long side chain groups, which leads to a reduction in its adsorption capacity. In the slump test at 2 hours and 4 hours, the results of Comparative Example 8 were lower than those of Example 1.

[0084] By comparing Example 1 and Comparative Example 9, we observed that the slump retention performance of the water-reducing agent in Comparative Example 9 decreased after 2 hours and 4 hours. This may be because the number of adsorption groups formed after hydrolysis is smaller, and its slump retention effect is not obvious compared to Example 1.

[0085] The super-retarded setting type ester polycarboxylate superplasticizer and its preparation method provided in this application include at least the following design concept, mechanism of action, and beneficial effects:

[0086] 1. This application utilizes unsaturated diethylene glycol monovinyl ether (carbon structure 2+2+2) and diethylene glycol monoallyl ether (carbon structure 3+2+2) to polymerize with 2,3-epoxypropylbenzoate and methyl 3,3-diphenyl-2,3-epoxypropionate to prepare polyether products. The structures of the epoxy alkyl polyether products containing ester groups and rigid benzene ring structures are as follows:

[0087] ,

[0088] Wherein, R1 is an alkylene group having 1 or 2 carbon atoms; the structure of N1 is...

[0089] . ,or Where n is 4 to 18.

[0090] As can be seen from the above structure, this polyether product introduces multiple ester groups, thereby introducing multiple ester groups into the water-reducing agent. Therefore, after hydrolysis, a large number of carboxyl groups can be introduced and adsorbed on the surface of cement particles, delaying the dissolution of cement particles. Moreover, the chain segments and free calcium ions in the pore solution form complex compounds, delaying the formation of supersaturated solutions in the solution. At the same time, the introduction of ester groups with different hydrolysis rates can also adsorb calcium hydroxide precipitate and ettringite precipitate in the pore solution.

[0091] Meanwhile, the benzene ring on the ester group (in the N1 group) increases the rigidity of the chain segment, and after the ester group hydrolyzes, the benzene ring or dibenzene ring remains on the side chain structure, increasing the steric hindrance effect of the chain segment, making the hydration products less prone to aggregation, further prolonging the hydration time and improving the retarding effect. It also reduces the hydrolysis rate of the ester group, which is beneficial for establishing different hydrolysis rates of the ester group in the overall polycarboxylate superplasticizer. However, if the structure of the polyether monomer (especially at the ester group) does not have a corresponding benzene ring designed, for example, the N1 structure adopts the structure without a benzene ring as shown below:

[0092]

[0093] This results in the adsorption group carboxyl group after hydrolysis not having the support of rigid chain segments. It will be "buried" in other side chains and shielded by other long flexible side chains, and its adsorption capacity will further decrease.

[0094] 2. The structure of polyoxyalkyl ethers containing ester groups and rigid benzene rings shows that, in the polyoxyalkyl ethers containing ester groups and rigid benzene rings participating in the polymerization of water-reducing agents, the unsaturated alcohol preferably uses a terminal olefin initiator with a 2+2+2 or 3+2+2 carbon structure (diethylene glycol monoallyl ether or diethylene glycol monovinyl ether). Compared to the less reactive initiators used in the synthesis of 2+2 or 2+4 type water-reducing agents, this application does not require low-temperature reaction and can react at room temperature, achieving energy saving and environmental protection, and meeting the requirements of carbon emission reduction. Compared to 4-carbon and 5-carbon polycarboxylate water-reducing agents, this application does not require heating for the reaction, thus also saving energy.

[0095] Although 1-allyloxyprop-1-ol (carbon structure 3+3) or 4-(allyloxy)-1-butanol (carbon structure 3+4) can be used as unsaturated alcohols, that is, terminal alkene initiators with 3+3 carbon structure and 3+4 carbon structure can also be polymerized at room temperature to obtain polyoxyalkyl ethers containing ester groups and rigid benzene ring structures.

[0096] However, different terminal olefin initiator structures affect the final polyoxyalkyl ether structure. As can be seen from the structures of the polyoxyalkyl ethers containing ester groups and rigid benzene rings mentioned above: compared with using 1-allyloxyprop-1-ol (carbon structure 3+3) or 4-(allyloxy)-1-butanol (carbon structure 3+4) as terminal olefin initiators, this application uses diethylene glycol monoallyl ether or diethylene glycol monovinyl ether, i.e., unsaturated alcohols with 3+2+2 or 2+2+2 structures as terminal olefin initiators. This gives the side chain structure of the polycarboxylate superplasticizer more folding angles in the porous solution, improves the chain segment flexibility of the polycarboxylate superplasticizer, and makes it easier to adsorb the active sites of cement particles and hydration products, thus further improving the subsequent slump retention performance. Meanwhile, the high activity of diethylene glycol monoallyl ether or diethylene glycol monovinyl ether shortens the reaction time of the copolymerization reaction and increases the solid content of the final polycarboxylate superplasticizer product, thereby improving production efficiency and saving energy in industrial production, and saving energy and improving synthesis efficiency for subsequent industrial applications.

[0097] 3. This application introduces diester-based ester monomers (the specific ester monomers involved in polymerization are olefin-coated diester structures) into the main chain of the polycarboxylate superplasticizer. Upon hydration to an alkaline environment, these diester groups release more carboxyl groups, which is beneficial for the adsorption of polycarboxylate segments, improving slump retention and setting retarding effects. Simultaneously, under alkaline cement conditions, effective adsorption prevents excessive consumption of free water in the polycarboxylate superplasticizer pore solution, further enhancing the steric hindrance effect of the polyether fragments and rigid benzene ring structure, thus maintaining slump. During ester hydrolysis, carboxylate ions are released, adsorbing calcium ions and cement particles or the surface of hydration products, further reducing the calcium ion concentration in the solution, covering the nucleation sites of hydration products, prolonging the nucleation time of hydration products, inhibiting the growth of Ca(OH)₂ and AFt crystal nuclei, slowing down the hydration rate, and extending the cement hydration induction period, thereby improving dispersion retention and exhibiting excellent slump retention. Meanwhile, the products released after hydrolysis still contain a large number of carboxylate ions, which can freely disperse into the negatively charged regions of cement particles or complex calcium ions, further filling the nucleation sites of hydration products and further hindering the formation of hydration products.

[0098] Furthermore, the structure of ester monomers affects the molecular structure of water-reducing agents. Different ratios of olefins and ester groups in the ester monomers will result in different structures in the polycarboxylate water-reducing agents, thus affecting their performance. Although some existing ester monomers involved in polymerization also possess ester groups, and even diester groups, their structures consist of an olefin and an ester group, or a diene and a diester group. For example, the structures of some ester monomers are as follows:

[0099] ;

[0100] Compared to existing ester monomers with a 1:1 ratio of olefin to ester group (either a monoolefin with a monoester group or a diene with a diene), this application uses a specific ester monomer (a monoolefin with a diene, structure shown below). The monoolefin with the diene does not cause cross-linking in the polycarboxylate superplasticizer. Its two ester groups generate more carboxyl groups upon hydrolysis, making them more easily adsorbed onto the surface of cement particles and hydration products, thus improving slump retention.

[0101] .

[0102] 4. This application effectively improves the long-term slump retention of polycarboxylate superplasticizers by introducing ester macromonomers. The effect is not as good if existing polyether macromonomers, such as TPEG polyether, are used instead.

[0103] 5. The process described in this application is simple to operate, the reaction conditions are mild, it is easy to scale up production, the production process is safe and pollution-free, and it is an environmentally friendly product.

[0104] Finally, it should be noted that:

[0105] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the concept of this application, and are not intended to limit them; those skilled in the art can make adaptive adjustments within the concept and protection scope of this application.

[0106] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A super-retarded setting type ester polycarboxylate superplasticizer, characterized in that: It is formed by polymerizing comonomers under the action of initiators, chain transfer agents and emulsifiers; the comonomers include ester macromonomers, polyoxyalkyl ethers containing ester groups and rigid benzene ring structures, ester small monomers and unsaturated acids; The structural formula of the polyoxyalkyl ether containing ester groups and a rigid benzene ring structure is as follows: ， Wherein, R1 is an alkylene group with 1 or 2 carbon atoms; N1 is an epoxy alkyl group containing an ester group and a rigid benzene ring structure, with the following structural formula: ； Wherein, n is 4 to 18; the ester monomer is diethyl 2-(4-pentene)malonate or diethyl 2-(4-propene)malonate.

2. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 1, characterized in that, The polyoxyalkyl ether containing ester groups and rigid benzene ring structures is prepared by ring-opening polymerization of unsaturated alcohols and epoxy ester compounds under the action of a catalyst. Wherein, the unsaturated alcohol is diethylene glycol monoallyl ether or diethylene glycol monovinyl ether; the epoxy ester compound is methyl 3,3-diphenyl-2,3-epoxypropionate; The molar ratio of the unsaturated alcohol to the epoxy ester compound is 1:(6-18); the ring-opening polymerization reaction temperature is 100℃-180℃, the reaction time is 4-6h, and the reaction pressure is 0.3Mpa-0.5Mpa.

3. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 2, characterized in that: The catalyst is one or more of potassium hydroxide, sodium ethoxide, sodium hydride, potassium hydride, and potassium hydroxide.

4. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 1, characterized in that: The mass ratio of the ester monomer, the ester macromonomer, the polyoxyalkylene ether containing the ester group and the rigid benzene ring structure, and the unsaturated acid is (1.8-6):100:(10-16):(4-13). The polymerization reaction temperature is 25℃~35℃, and the reaction time is 0.5h~1.5h.

5. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 1, characterized in that: The ester macromonomer is one or more of the following: polyethylene glycol dimethacrylate with a molecular weight of 1500-5000, polyethylene glycol monomethyl ether acrylate with a molecular weight of 1500-5000, polyethylene glycol acrylate with a molecular weight of 1500-5000, polyethylene glycol monomethoxy ether monoacrylate with a molecular weight of 1500-5000, and polyethylene glycol monomethoxy ether monomethacrylate with a molecular weight of 1500-5000.

6. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 1, characterized in that: The unsaturated acid is one or more combinations of acrylic acid, methacrylic acid, and maleic acid.

7. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 1, characterized in that: The initiator includes an oxidizing agent and a reducing agent; The oxidant is one or more of potassium persulfate, hydrogen peroxide, and 2,5-dimethyl-2,5-bis(hydrogen peroxide)hexane; the reducing agent is one or more of sodium hypophosphite, sodium sulfite, ferrous sulfate, and potassium thiosulfate; the chain transfer agent is one or more of mercaptoacetic acid, 2-hydroxypropanethiol, 2-mercaptosuccinic acid, and sodium hypophosphite; and the emulsifier is one or more of sorbitol polyoxyethylene ether tetraoleate and stearic acid polyoxyethylene ester.

8. The super-retarded setting type ester polycarboxylate superplasticizer according to claim 7, characterized in that: in, The amount of oxidant is 1% to 2.5% of the total mass of the ester macromonomers, the amount of reducing agent is 0.8% to 2.8% of the total mass of the ester macromonomers, the amount of chain transfer agent is 0.5% to 2% of the total mass of the ester macromonomers, and the amount of emulsifier is 1% to 4% of the total mass of the ester macromonomers.

9. A method for preparing a super-retarded setting ester polycarboxylate superplasticizer as described in any one of claims 1-8, characterized in that, The preparation steps include the following: The ester monomers, the ester macromonomers, and the polyoxyalkyl ethers containing ester groups and rigid benzene ring structures are mixed, and an initiator solution, a chain transfer agent solution, an emulsifier solution, and an unsaturated acid are added at 25°C to 35°C to carry out a polymerization reaction for 0.5 h to 1.5 h. Then, the mixture is kept at this temperature for a certain period of time, and the pH is adjusted to obtain the super-retarded setting type ester polycarboxylate superplasticizer.

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