Double-block polymeric monomer, preparation method thereof and polycarboxylic acid water reducing agent using double-block polymeric monomer and suitable for low-carbon cement

Abstract

The invention discloses a double-block polymeric monomer, a preparation method thereof and a polycarboxylic acid water reducing agent which uses the double-block polymeric monomer and is suitable for low-carbon cement. The polycarboxylate superplasticizer is formed by copolymerization of a double-block polymeric monomer A, an unsaturated carboxylic acid monomer B and a polymerizable phosphoric acid monomer C through free radicals, wherein the double-block polymeric monomer A is a polymeric monomer composed of an unsaturated multi-element heterocyclic chain segment near a double-bond end and a polyether polyol acrylate chain segment far away from the double-bond end. The polycarboxylic acid water reducing agent is suitable for low-carbon cement, solves the problems of weak dispersion and poor adaptability of the existing water reducing agent in the application process of the low-carbon cement, and is more suitable for low-carbon cement concrete containing various complex admixtures such as slag, clay and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of admixtures for cement concrete, and particularly relates to a polycarboxylate water reducer applicable to low-carbon cement, its preparation method and application. Background Art

[0002] With the development of modern society and the construction of urban infrastructure, the demand for cement continues to increase. The production of cement will inevitably cause a large amount of energy consumption and carbon dioxide emissions, posing a huge pressure on the resource environment. In order to reduce carbon emissions in the construction industry, a new type of low-carbon cement building material has emerged. Low-carbon cement mainly uses various supplementary cementitious materials (SCMs) such as fly ash, limestone, ground granulated blast furnace slag, metakaolin, biomass ash, steel slag, etc. to partially replace clinker to reduce the usage of Portland cement. Low-carbon cement has the advantages of wide sources, low carbon emissions, low energy consumption, etc. However, the hydration of cement incorporated with SCMs materials is different from that of ordinary Portland cement because the calcium content of these materials is usually low and the composition is relatively complex, which further affects the dispersing ability of water reducers in them, resulting in construction problems such as decreased fluidity of concrete, poor strength and durability. Therefore, it is of great significance to develop an admixture applicable to low-carbon cement materials.

[0003] As the third-generation concrete water reducer, polycarboxylate water reducer has the advantages of high dispersion, high slump retention, low dosage, etc., and is widely used in high-performance concrete. Due to the unique comb-shaped structure of polycarboxylate water reducer, it can be modified or redesigned by changing the composition of functional groups, the length of the backbone, the length or density of side chains to achieve good performance of cement-based materials. For example, polycarboxylate water reducer with a high content of carboxyl (-COO-) can quickly adsorb on the surface of cement particles, showing good initial dispersion, but poor slump retention; polycarboxylate water reducer with a high grafting density or long side chains is more conducive to the dispersion of cement particles; the retarding effect on cement hydration increases with the decrease of side chain length.

[0004] Patent CN107987231B discloses an anti-clay polycarboxylate water reducer and its preparation method, which is polymerized from unsaturated carboxylic acid monomers, N-vinylpyrrolidone (NVP), and unsaturated polyethers. The side chain structure changes from the traditional linear shape to a comb shape, and the introduction of NVP units increases the ductility of the side chains. The increase in the molecular size of the side chains makes it difficult to insert into the layered structure of clay, endowing the product with good anti-clay function.

[0005] Patent CN112111041B discloses a preparation method of an anti-sludge type early-strength polycarboxylate water reducer for high-mineral admixture concrete, which is obtained by a variable-speed dropping process from ethylene glycol mono-vinyl polyethylene glycol ether, acrylic acid, and amide-based active functional monomers, and has remarkable high early-strength and anti-sludge characteristics, meeting the requirements of the application of high-mineral admixture concrete.

[0006] Patent CN109705289B discloses a block imidazole type polycarboxylate water reducer and its preparation method. The block imidazole type polycarboxylate water reducer is obtained by the polymerization reaction of acrylic acid, vinyl imidazole, and polyoxyethylene ether through a RAFT reagent, which can effectively improve the workability of concrete, reduce the dosage of cement, and improve the dispersibility of cement. It can not only effectively resist sludge but also improve the later compressive strength of concrete.

[0007] The above technologies design the structure of polycarboxylate water reducers for high admixture and high clay environments, either modifying the adsorption groups from the main chain or transforming the topological structure from the side chain. The technical effects obtained are limited, and they still cannot effectively solve the dispersion requirements of current low-carbon cements. In particular, the application technologies mainly based on Limestone Calcined Clay Cement (LC3) are more lacking. There is an urgent need for a concrete water reducer that is widely applicable to low-carbon cement-based materials. Summary of the Invention

[0008] To solve the problems of weak dispersion and poor adaptability of existing water reducers in the application of low-carbon cements, the present invention provides a double-block polymerization monomer and a polycarboxylate water reducer suitable for low-carbon cements prepared based on it.

[0009] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0010] A double-block polymerization monomer, having a typical double-block structure, is a polymerization monomer composed of an unsaturated polyheterocyclic chain segment near the double bond end and a polyether polyol acrylate chain segment far from the double bond end;

[0011] The unsaturated polyheterocyclic chain segment is derived from an unsaturated polyhybrid monomer, and the unsaturated polyhybrid monomer is selected from any one or a mixture of one or more of morpholine-based, piperazine-based, and pyrrolidine-based unsaturated polyhybrid monomers;

[0012] The polyether polyol acrylate chain segment is derived from the monomer polyether polyol acrylate, and the end of the polyether polyol acrylate is capped with methoxy.

[0013] Further, the structure of the morpholine-based unsaturated polyhybrid monomer in the present invention is shown in general formula (Ⅰ), the structure of the piperazine-based unsaturated polyhybrid monomer is shown in general formula (Ⅱ), and the structure of the pyrrolidine-based unsaturated polyhybrid monomer is shown in general formula (Ⅲ).

[0014]

[0015] Among them, in each of the above general formulas, R1 is independently selected as an alkyl group having 1 to 4 carbon atoms or -CO-, -COOCH2CH2-, -CONHCH2CH2-, -COOCH2-, -CONHCH2- or does not exist.

[0016] Furthermore, the polyether polyol acrylate structure of the present invention is shown by the general formula (IV):

[0017]

[0018] Among them, in the general formula (IV), n is an integer from 2 to 10, and R2-R4 are each independently an alkyl group having 1 to 4 carbon atoms or -H. Furthermore, the polyether polyol acrylate is preferably methoxypolyethylene glycol acrylate or methoxypolyethylene glycol methacrylate.

[0019] Furthermore, the preparation method of the diblock polymerization monomer of the present invention includes the following steps:

[0020] (1) After freeze-thaw cycling at least three times in an anhydrous solvent with an unsaturated polyheterocyclic monomer, a RAFT reagent, and a first batch of initiator I, a polymerization reaction is carried out in a nitrogen atmosphere oil bath to obtain an intermediate, and the reaction is terminated after rapidly quenching free radicals in an ice-water bath; then, a polyether polyol acrylate and a second batch of initiator I are added, and after freeze-thaw cycling at least three times, an oil bath reaction and purification are carried out in a nitrogen atmosphere to obtain a block intermediate;

[0021] (2) The block intermediate obtained in step (1), an unsaturated alcohol, an inhibitor, and a catalyst are subjected to an esterification reaction under a water-carrying agent, and after the reaction is completed, the diblock polymerization monomer is prepared through purification;

[0022] The molar ratio of the unsaturated polycyclic monomer, polyether polyol acrylate to the RAFT reagent in step (1) is 5-10:5-10:1;

[0023] The molar amount ratio of the unsaturated alcohol to the block intermediate in step (2) is 1-1.1;

[0024] The RAFT reagent in step (1) is a dithioester or trithioester with a carboxyl group at one end, and is further preferably any one of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid CDPA, 2-(dodecyltrithiocarbonato)-2-methylpropanoic acid dithioester or trithioester compound, 4-cyano-4-(phenylthiocarbamoylthio)pentanoic acid (CPADB), 2-(ethyltrithiocarbonato)-2-methylpropanoic acid (EMP), and (4-cyano-4-[(ethylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (CETPA).

[0025] Furthermore, in step (1) of the present invention, the dosage of the first batch of initiator I is 0.1% - 2% of the mass of the unsaturated polyheterocyclic monomer, and the dosage of the second batch of initiator I is 0.1% - 2% of the mass of the polyether polyol acrylate; the initiator I is a peroxide initiator or an azo initiator, and the general structural formula of the peroxide initiator is R-O-O-H or R-O-O-R, where R is an alkyl group, an acyl group, or a carbonate group, and is further preferably any one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide; the azo initiator is preferably any one of azobisisobutyronitrile (AIBN), azobisisopentanenitrile (AMBN), azobisisoheptanenitrile (ABVN), dimethyl 2,2'-azobis(2-methylpropionate) (AIBME), 2,2'-azobis(2,4,4-trimethylpentane), and 2-phenylazo-2,4-dimethyl-4-methoxypentanenitrile.

[0026] Furthermore, in step (1) of the present invention, the amount of the anhydrous solvent is controlled such that the total mass concentration of the reactants is 30 - 80%, and it is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and N-methylpyrrolidone.

[0027] Furthermore, in step (1) of the present invention, the polymerization reaction temperature is 50 - 90 °C, the polymerization reaction time is 1 - 12 h, the oil bath reaction time is 1 - 12 h, the oil bath reaction temperature is the same as the polymerization reaction temperature, and the mass concentration of the polymerization reactants is 30 - 80%. The polymerization reactants include an unsaturated polycyclic monomer, a polyether polyol acrylate, and a RAFT reagent.

[0028] Furthermore, the purification method in step (1) of the present invention is to distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in a precipitant, and dry for 1 - 24 h after centrifugation. The precipitant is selected from any one of diethyl ether, n-hexane, and petroleum ether, and the dosage is 2 - 3 times the total mass of the remaining substances after reduced pressure distillation.

[0029] The feeding order of the unsaturated polyheterocyclic monomer and polyether polyol acrylate in step (1) of the present invention cannot be changed. Otherwise, the structure of the macromonomer with a polyheterocyclic chain segment at the near double bond end cannot be obtained, and the ductility of the polyether polyol acrylate chain segment is also limited, affecting the use effect of the polycarboxylate water reducer applicable to low-carbon cement described in the present invention.

[0030] Furthermore, the unsaturated alcohol in step (2) of the present invention has the following general structural formula (Ⅴ):

[0031]

[0032] Wherein R5, R6, and R7 are -CH3 or -H, and R8 is an alkyl group of C1-C4, -OCH2CH2-, -OCH2CH2OCH2CH2-, -OCH2CH2CH2CH2-. Further, it can be preferably any one of allyl alcohol, 2-butenol, 2-allyl alcohol, 2-methylallyl alcohol, 3-methyl-3-buten-1-ol, 4-penten-1-ol, ethylene glycol mono vinyl ether, and diethylene glycol mono vinyl ether.

[0033] Furthermore, the water-carrying agent in step (2) of the present invention is selected from any one of benzene, xylene, toluene, and chloroform, and the dosage is 1 to 3 times the total mass of the reactants in step (2).

[0034] Furthermore, the catalyst in step (2) of the present invention is any one or a mixture of more than one of sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, dimethylsulfonic acid, sodium bisulfate monohydrate, solid superacid, and polyphosphoric acid. The dosage is 1-10 wt% of the total mass of the reactants in step (2). Too much easily leads to an increase in side reactions, and too little results in low catalytic efficiency and is not conducive to the reaction.

[0035] Furthermore, the polymerization inhibitor in step (2) of the present invention is selected from any one of phenothiazine, p-benzoquinone, and p-tert-butylcatechol, aiming to avoid the double bond being damaged during the high-temperature esterification process. The dosage is 1 to 0.1% of the total mass of the reactants in step (2).

[0036] Furthermore, the esterification reaction temperature in step (2) of the present invention is 70-170 °C. The specific reaction temperature can be preferably selected according to the boiling point of different water-carrying agents; the esterification reaction time is 1-24 h, and the specific end point of the reaction is when no more water is separated from the water-carrying agent; the purification method in step (2) is the same as the purification method in step (1).

[0037] Furthermore, the present invention also provides a polycarboxylate water reducer applicable to low-carbon cement using the above-mentioned diblock polymerization monomer, which is formed by free radical copolymerization of monomer A, monomer B and monomer C. Its main chain adopts a multi-functional adsorption group of phosphate or phosphate ester and acrylic acid, and a branched side chain with a block structure composed of polyether polyol acrylate and multi-functional heterocyclic monomers, and a cyclic structure is introduced near the main chain end;

[0038] The monomer A is the diblock polymerization monomer;

[0039] The monomer B is an unsaturated carboxylic acid monomer, and its dosage is 3 to 6 times the molar amount of monomer A;

[0040] The monomer C is a polymerizable phosphoric acid monomer, and its dosage is 0.5 to 2 times the molar amount of monomer A.

[0041] Furthermore, the monomer B of the present invention is selected from any one or a mixture of more than one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid or maleic anhydride.

[0042] Furthermore, the monomer C of the present invention has the following general structural formula (Ⅵ):

[0043]

[0044] Wherein R9, R 11 is selected from C1-C4 alkyl or -H, R 10 is selected from C1-C4 alkyl or -COOCH2-, -COOCH2CH2-, -COOCH2CH2CH2-, -CONHCH2-, -CONHCH2CH2-, -CONHCH2CH2CH2- or does not exist; more preferably selected from vinyl phosphoric acid, acryloyloxyethyl phosphate, acryloyloxypropyl phosphate, 2-methacryloyloxyethyl phosphate, 2-methacryloyloxypropyl phosphate, acrylamide ethyl phosphate, acrylamide-propyl phosphate, dimethyl vinyl phosphate, diethyl vinyl phosphate any one of them.

[0045] Furthermore, the weight average molecular weight (M w ) of the polycarboxylate water reducer of the present invention is controlled at 10,000 to 40,000 Da. Too low or too high is not conducive to the dispersion effect.

[0046] Furthermore, the preparation method of the polycarboxylate water reducer of the present invention is: placing monomer A, initiator II, and chain transfer agent in the presence of deionized water at a temperature of 25 to 80 °C, dropping a mixed solution of monomer B, monomer C and deionized water, with a dropping reaction time of 1 to 8 h, and maintaining the temperature for curing for 1 to 8 h, and adding liquid alkali to adjust the pH to 6 to 7;

[0047] Further, the initiator II in the present invention is persulfate, water-soluble azo initiator or redox initiator; among them, the persulfate is preferably ammonium persulfate, potassium persulfate or sodium persulfate, and its dosage is 0.1%-5% of the total mass of the polymerization monomers; the water-soluble azo initiator is preferably azodiisobutylamidine hydrochloride, azodiisobutimidazoline hydrochloride, azodicyanovaleric acid or azodiisopropylimidazoline, and its dosage is 0.1%-3% of the total mass of the polymerization monomers; for the redox initiator, preferably the oxidant is hydrogen peroxide or persulfate, and the reductant is ferrous salt, cuprous salt, sodium bisulfite, sodium thiosulfate, ascorbic acid or sodium formaldehyde sulfoxylate and other sulfates of sulfur below hexavalent, and its dosage is 0.5%-3% of the total mass of the polymerization monomers, where the molar ratio of the oxidant to the reductant is 2-6:1.

[0048] Further, the chain transfer agent in the present invention is any one of mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptobutanol, and its dosage is 0.5-5% of the total molar amount of the polymerization monomers.

[0049] The reaction temperature is controlled at 25-80°C, and the polymerization mass concentration is controlled at 20-60%. If the reaction concentration is too low, the reaction is slow, and if it is too high, it is not conducive to the control of the reaction.

[0050] The polycarboxylate water reducer applicable to low-carbon cement in the present invention can be compounded with retarders, early strength agents, air-entraining agents, thickeners, defoamers, etc. The dosage for single use is 0.5‰-2‰ of the mass of the cementitious material;

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The polyether polyol acrylate and the water-soluble polyheterocyclic monomer form a branched side chain of a block. Introducing a cyclic structure near the main chain end can avoid the curling and winding of the polyether polyol side chain and improve the ductility of the side chain. The comb-shaped branched side chain can provide stronger dispersion performance;

[0053] (2) The combination of the cyclic monomer and the branched structure can reduce the intercalation effect of the sludge powder on the side chain and improve the anti-sludge ability of the water reducer;

[0054] (3) The main chain adopts a multi-adsorption group of phosphoric acid group or phosphate ester and acrylic acid, which is more suitable for low-carbon cement concrete containing various complex admixtures such as slag and clay. Specific embodiments

[0055] The technical solution of the present invention will be further described in detail below through examples

[0056] The dosages in each example and comparative example are in parts by mass;

[0057] Synthesis Example 1

[0058] A preparation method of a polycarboxylate water reducer applicable to low-carbon cement includes:

[0059] (1) Dissolve 6.5 parts of vinylpyrrolidone, 5 parts of CDPA, and 0.13 part of benzoyl peroxide in 25 parts of N,N-dimethylformamide. Perform at least three freeze-thaw cycles in a nitrogen atmosphere, react at 75 °C in an oil bath for 8 h, quench free radicals in an ice-water bath and then terminate the reaction to obtain an intermediate; continue to add 32 parts of methoxypolyethylene glycol acrylate (M w = 500), 0.6 part of benzoyl peroxide, perform at least three freeze-thaw cycles, react at 75 °C in an oil bath for 8 h in a nitrogen atmosphere, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 90 parts of ether, and dry for 1 h after centrifugation to obtain a block intermediate;

[0060] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 1.2 parts of ethylene glycol mono vinyl ether, 0.16 part of phenothiazine, and 0.35 part of p-toluenesulfonic acid in 50 parts of toluene, perform an esterification reaction at 125 °C for 9 h. After the reaction is completed, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 70 parts of ether, and dry for 1 h after centrifugation to prepare a double-block polymerization monomer A;

[0061] (3) Dissolve 1.0 part of ammonium persulfate, 0.2 part of mercaptoethanol, and 20 parts of double-block polymerization monomer A in 50 parts of deionized water and mix evenly. Use 2.4 parts of acrylic acid and 1.2 parts of vinyl phosphonic acid dissolved in 40 parts of deionized water as the dropping solution, heat to 70 °C and drop for 2 h, keep the temperature for reaction for 2 h, add liquid alkali to adjust the pH to 6 - 7 to obtain the polycarboxylate water reducer CPCE-1 applicable to low-carbon cement of the present invention.

[0062] Synthesis Example 2

[0063] A preparation method of a polycarboxylate water reducer applicable to low-carbon cement includes:

[0064] (1) Dissolve 23 parts of morpholine ethyl acrylate, 5 parts of CPADB, and 0.34 part of tert-butyl benzoyl peroxide in 20 parts of N,N-dimethylformamide. Perform at least three freeze-thaw cycles in a nitrogen atmosphere, react at 90 °C in an oil bath for 12 h, quench free radicals in an ice-water bath and then terminate the reaction to obtain an intermediate; continue to add 50 parts of methoxypolyethylene glycol methacrylate (M w = 300), 0.75 part of tert-butyl benzoyl peroxide, perform at least three freeze-thaw cycles, react at 90 °C in an oil bath for 10 h in a nitrogen atmosphere, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 160 parts of n-hexane, and dry for 2 h after centrifugation to obtain a block intermediate;

[0065] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 0.5 part of 2 - allyl alcohol, 0.04 part of p - benzoquinone, and 0.6 part of methanesulfonic acid in 60 parts of toluene, and carry out an esterification reaction at 140 °C for 10 h. After the reaction is completed, most of the solvent is removed by distillation or vacuum distillation, and the product is precipitated 2 - 3 times in 70 parts of n - hexane. After centrifugation, it is dried for 6 h to prepare the diblock polymerization monomer A;

[0066] (3) Dissolve 0.8 part of potassium persulfate, 0.14 part of mercaptoethanol, and 20 parts of the diblock polymerization monomer A in 20 parts of deionized water and mix evenly. Dissolve 2.4 parts of methacrylic acid and 2.0 parts of acryloyloxyethyl phosphate in 20 parts of deionized water as the dropping solution. Heat up to 80 °C and drop it for 1 h, keep the temperature for reaction for 2 h, and add liquid alkali to adjust the pH to 6 - 7 to obtain the polycarboxylate water - reducing agent CPCE - 2 for low - carbon cement described in the invention.

[0067] Synthesis Example 3

[0068] A preparation method of a polycarboxylate water - reducing agent for low - carbon cement includes:

[0069] (1) Dissolve 23 parts of allyl piperazine, 5 parts of CETPA, and 0.23 part of methyl ethyl ketone peroxide in 28 parts of toluene, carry out at least three freeze - thaw cycles in a nitrogen atmosphere, react at 85 °C in an oil bath for 6 h, and terminate the reaction by quenching free radicals in an ice - water bath to obtain an intermediate; then continue to add 30 parts of methoxypolyethylene glycol acrylate (M w = 300), 0.3 part of methyl ethyl ketone peroxide, carry out at least three freeze - thaw cycles, react at 85 °C in a nitrogen atmosphere in an oil bath for 12 h, remove most of the solvent by distillation or vacuum distillation, precipitate 2 - 3 times in 150 parts of petroleum ether, and dry for 24 h after centrifugation to obtain a block intermediate;

[0070] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 0.75 part of 2 - methylallyl alcohol, 0.25 part of phenothiazine, and 0.6 part of polyphosphoric acid in 90 parts of xylene, carry out an esterification reaction at 150 °C for 16 h. After the reaction is completed, most of the solvent is removed by distillation or vacuum distillation, precipitate 2 - 3 times in 70 parts of petroleum ether, and dry for 24 h after centrifugation to prepare the diblock polymerization monomer A;

[0071] (3) Dissolve 0.5 part of azodiisobutyramidine hydrochloride, 0.15 part of mercaptopropionic acid, and 20 parts of the diblock polymerization monomer A in 10 parts of deionized water and mix evenly. Dissolve 2.8 parts of acrylic acid and 0.8 part of acrylamidopropyl phosphate in 10 parts of deionized water as the dropping solution. Heat up to 65 °C and drop it for 3 h, keep the temperature for reaction for 3 h, and add liquid alkali to adjust the pH to 6 - 7 to obtain the polycarboxylate water - reducing agent CPCE - 3 for low - carbon cement described in the invention.

[0072] Synthesis Example 4

[0073] A preparation method of a polycarboxylate water reducer applicable to low-carbon cement includes:

[0074] (1) Dissolve 22 parts of 4-acryloylmorpholine, 5 parts of EMP, and 0.03 part of azobisisobutyronitrile (AIBN) in 27 parts of N,N-dimethylacetamide. Perform freeze-thaw cycles at least three times under a nitrogen atmosphere, react at 55 °C in an oil bath for 1 h, and quench free radicals in an ice-water bath to terminate the reaction to obtain an intermediate; then continue to add 55 parts of methoxypolyethylene glycol methacrylate (M w = 400), 0.06 part of azobisisobutyronitrile (AIBN), perform freeze-thaw cycles at least three times, react at 55 °C in an oil bath for 1 h under a nitrogen atmosphere, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 200 parts of ether, and dry for 24 h after centrifugation to obtain a block intermediate;

[0075] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 0.75 part of 3-methyl-3-buten-1-ol, 0.2 part of p-benzoquinone, and 0.9 part of p-toluenesulfonic acid in 50 parts of chloroform, and perform an esterification reaction at 80 °C for 20 h. After the reaction is completed, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 70 parts of ether, and dry for 5 h after centrifugation to prepare a double-block polymer monomer A;

[0076] (3) Mix 0.2 part of hydrogen peroxide, 0.15 part of mercaptopropionic acid, and 20 parts of double-block polymer monomer A evenly in 10 parts of deionized water. Dissolve 1.9 parts of methacrylic acid, 1.2 parts of 2-methacryloyloxyethyl phosphate, and 0.25 part of ascorbic acid in 15 parts of deionized water as a dropping solution. Heat to 45 °C and dropwise add for 4 h, hold the reaction for 3 h, and add liquid alkali to adjust the pH to 6 - 7 to obtain the polycarboxylate water reducer CPCE-4 applicable to low-carbon cement described in the invention.

[0077] Synthesis Example 5

[0078] A preparation method of a polycarboxylate water reducer applicable to low-carbon cement includes:

[0079] (1) Dissolve 12 parts of allylmorpholine, 5 parts of CPADB, and 0.06 part of azobisisopentanenitrile (AMBN) in 25 parts of toluene. Perform freeze-thaw cycles at least three times under a nitrogen atmosphere, react at 70 °C in an oil bath for 5 h, and quench free radicals in an ice-water bath to terminate the reaction to obtain an intermediate; then continue to add 45 parts of methoxypolyethylene glycol acrylate (M w = 500), 0.2 part of azobisisopentanenitrile (AMBN), perform freeze-thaw cycles at least three times, react at 70 °C in an oil bath for 5 h under a nitrogen atmosphere, distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in 180 parts of n-hexane, and dry for 12 h after centrifugation to obtain a block intermediate;

[0080] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 0.65 part of 2-butenol, 0.15 part of p-tert-butylcatechol, and 1.5 parts of polyphosphoric acid in 90 parts of chloroform, and carry out an esterification reaction at 90 °C for 24 h. After the reaction is completed, most of the solvent is removed by distillation or vacuum distillation, and the product is precipitated 2-3 times in 70 parts of ether, centrifuged, and dried for 8 h to prepare the diblock polymerization monomer A;

[0081] (3) Dissolve 0.2 part of hydrogen peroxide, 0.12 part of 2-mercaptobutanol, and 20 parts of the diblock polymerization monomer A in 10 parts of deionized water and mix evenly. Dissolve 1.8 parts of maleic anhydride, 1.3 parts of diethyl vinylphosphonate, and 0.34 part of ascorbic acid in 15 parts of deionized water as the dropping solution. Heat up to 45 °C and dropwise add for 2 h, keep the temperature for reaction for 8 h, add liquid alkali to adjust the pH to 6-7 to obtain the polycarboxylate water reducer CPCE-5 for low-carbon cement described in the invention.

[0082] Synthesis Example 6

[0083] A preparation method of a polycarboxylate water reducer for low-carbon cement includes:

[0084] (1) Dissolve 26 parts of 4-acryloylpiperazine, 5 parts of CETPA, and 0.06 part of azodiisooctanenitrile (ABVN) in 50 parts of N-methylpyrrolidone, carry out freeze-thaw cycles in a nitrogen atmosphere for at least three times, react at 60 °C in an oil bath for 9 h, quench free radicals in an ice-water bath to terminate the reaction to obtain an intermediate; continue to add 35 parts of methoxypolyethylene glycol methacrylate (M w =300), 0.07 part of azodiisooctanenitrile (ABVN), carry out freeze-thaw cycles for at least three times, react at 60 °C in a nitrogen atmosphere in an oil bath for 9 h, remove most of the solvent by distillation or vacuum distillation, precipitate 2-3 times in 190 parts of petroleum ether, centrifuge, and dry for 16 h to obtain the block intermediate;

[0085] (2) Dissolve 30 parts of the block intermediate obtained in step (1), 0.55 part of 2-allyl alcohol, 0.3 part of phenothiazine, and 3 parts of sulfuric acid in 90 parts of xylene, carry out an esterification reaction at 170 °C for 5 h. After the reaction is completed, most of the solvent is removed by distillation or vacuum distillation, precipitate 2-3 times in 70 parts of n-hexane, centrifuge, and dry for 12 h to prepare the diblock polymerization monomer A;

[0086] (3) Dissolve 0.2 part of hydrogen peroxide, 0.21 part of 2-mercaptobutanol, and 20 parts of the diblock polymerization monomer A in 15 parts of deionized water and mix evenly. Dissolve 2.5 parts of acrylic acid, 2.0 parts of acryloyloxypropyl phosphate, and 0.15 part of sodium formaldehyde bisulfite in 20 parts of deionized water as the dropping solution. Heat up to 25 °C and dropwise add for 8 h, keep the temperature for reaction for 4 h, add liquid alkali to adjust the pH to 6-7 to obtain the polycarboxylate water reducer CPCE-6 for low-carbon cement described in the invention.

[0087] Comparative Example 1

[0088] A preparation method of a polycarboxylate water reducer includes:

[0089] (1) Dissolve 32 parts of methoxypolyethylene glycol acrylate (M w = 500), 5 parts of CDPA, and 0.13 parts of benzoyl peroxide in 25 parts of N,N-dimethylformamide, perform freeze-thaw cycles at least three times in a nitrogen atmosphere, react at 75°C in an oil bath for 8 h, quench free radicals in an ice-water bath to terminate the reaction, remove most of the solvent by distillation or vacuum distillation, precipitate 2 - 3 times in 90 parts of ether, and dry for 1 h after centrifugation to obtain an intermediate;

[0090] (2) Dissolve 30 parts of the intermediate obtained in step (1), 1.2 parts of ethylene glycol mono vinyl ether, 0.16 parts of phenothiazine, and 0.35 parts of p-toluenesulfonic acid in 50 parts of toluene, perform an esterification reaction at 125°C for 9 h, remove most of the solvent by distillation or vacuum distillation after the reaction is completed, precipitate 2 - 3 times in 70 parts of ether, and dry for 1 h after centrifugation to prepare monomer A;

[0091] (3) Dissolve 1.0 part of ammonium persulfate, 0.2 part of mercaptoethanol, and 20 parts of monomer A in 50 parts of deionized water and mix evenly. Use 2.4 parts of acrylic acid and 1.2 parts of vinyl phosphonic acid dissolved in 40 parts of deionized water as a dropping solution, heat to 70°C and drop for 2 h, keep the temperature for reaction for 2 h, add liquid alkali to adjust the pH to 6 - 7 to obtain the polycarboxylate water reducer REF-1 suitable for low-carbon cement described in the invention.

[0092] Comparative Example 2

[0093] A preparation method of a polycarboxylate water reducer includes:

[0094] (1) Dissolve 6.5 parts of vinyl pyrrolidone, 32 parts of methoxypolyethylene glycol acrylate (M w = 500), 5 parts of CDPA, and 0.13 parts of benzoyl peroxide in 25 parts of N,N-dimethylformamide, perform freeze-thaw cycles at least three times in a nitrogen atmosphere, react at 75°C in an oil bath for 8 h, quench free radicals in an ice-water bath to terminate the reaction, remove most of the solvent by distillation or vacuum distillation, precipitate 2 - 3 times in 90 parts of ether, and dry for 1 h after centrifugation to obtain an intermediate;

[0095] (2) Dissolve 30 parts of the intermediate obtained in step (1), 1.2 parts of ethylene glycol mono vinyl ether, 0.16 parts of phenothiazine, and 0.35 parts of p-toluenesulfonic acid in 50 parts of toluene, perform an esterification reaction at 125°C for 9 h, remove most of the solvent by distillation or vacuum distillation after the reaction is completed, precipitate 2 - 3 times in 70 parts of ether, and dry for 1 h after centrifugation to prepare monomer A;

[0096] (3) 1.0 part of ammonium persulfate, 0.2 part of mercaptoethanol, and 20 parts of monomer A are dissolved in 50 parts of deionized water and mixed evenly. 2.4 parts of acrylic acid and 1.2 parts of vinyl phosphoric acid are dissolved in 40 parts of deionized water as the dropping solution. The temperature is raised to 70 °C and dropped for 2 hours, and then kept reacting for 2 hours. Liquid alkali is added to adjust the pH to 6 - 7 to obtain the polycarboxylate water reducer REF-2 for low-carbon cement described in the invention.

[0097] The following examples use self-made Limestone Calcined Clay Cement (LC3) for relevant tests. The specific preparation method refers to invention patents CN111875268B, CN115959870A, and CN116018328A. The proportion of LC3 cement is 50% P·I 42.5 Portland cement, 30% calcined clay, 15% limestone, and 5% gypsum.

[0098] Application Example 1

[0099] Referring to the "Test Method for the Homogeneity of Concrete Admixtures" GBT8077-2012, the fluidity of the neat cement paste is tested. The dosage of the admixture is 0.12% water reducer, and the water-cement ratio is 0.29. The dispersion performance of the examples and the comparative samples in Helin cement P·II 42.5, reference cement P·I 42.5, and LC3 cement is tested respectively; the synthesis method of the commercially available water reducer refers to Comparative Example 1 of patent CN113072667B.

[0100] Table 1 Test Results of Cement Paste Fluidity Unit: mm

[0101]

[0102] From the neat cement dispersion data of the above different types of cement in Table 1, it can be seen that the polycarboxylate water reducer for low-carbon cement described in the present invention shows good initial dispersion performance and fluidity retention performance in Helin cement, reference cement, and LC3 cement. Especially in low-carbon cement compared with commercially available cement, the dispersion performance is stable with small fluctuations, and it has good adaptability to cementitious materials, which benefits from its multiple adsorption groups. Compared with Comparative Example 1, without introducing the cyclic chain segment structure, although the dispersion performance of Comparative Example 1 is acceptable in conventional cement, its dispersion ability is poor in the special cementitious material LC3, indicating that the cyclic chain segment plays a crucial role in the dispersion of low-carbon LC3 cement; compared with Comparative Example 2, the difference lies in whether the polyethylene glycol acrylate chain segment and the cyclic chain segment are block structures. It can be significantly seen from the results that the block side chain structure can improve its dispersion performance in different cements, and its initial fluidity has increased.

[0103] Application Example 2

[0104] The fluidity of the mortar with superplasticizer was tested using the engineering mortar mix with high admixture content. The specific mix ratio was 220 g of LC3 cement, 120 g of fly ash, 112 g of ground granulated blast-furnace slag, 1050 g of river sand, water-binder ratio of 0.33, and the dosage of superplasticizer was 0.12 - 0.14%;

[0105] Table 2 Test Results of Engineering Mortar Unit: mm

[0106]

[0107]

[0108] The above data can once again show that the polycarboxylate superplasticizer for low-carbon cement described in the invention exhibits good dispersion performance and fluidity retention performance in low-carbon LC3 cement. After the dosage of the commercially available superplasticizer is increased from 0.12% to 0.14%, its initial mortar fluidity is still inferior to that of CPCE-1 - 6. Combining the data results of REF-1 and REF-2, the introduction of methoxyacrylate branched side chains and random polymerization methods alone both deteriorate the product performance, and the later fluidity loss rate also accelerates. In summary, it is proved that the polycarboxylate superplasticizer for low-carbon cement described in the invention has good application performance in the high-admixture system with LC3 cement mix ratio, and its unique block side chains, cyclic segments and terminal branched structures have good adsorption and dispersion ability in SCMs materials.

[0109] Application Example 3

[0110] Refer to "Test Methods for Homogeneity of Concrete Admixtures" - GBT8077-2012 to test the slump and spread of concrete; "Standard Test Methods for Physical and Mechanical Properties of Concrete" (GB / T50081-2019) to test the 3d and 28d compressive strengths of concrete; the concrete mix ratio was 150 kg / m of LC3 cement 3 , 150 kg / m3 of fly ash, 80 kg / m of ground granulated blast-furnace slag 3 , 750 kg / m of river sand 3 , 1100 kg / m of crushed stone 3 , water-binder ratio of 0.4, and the dosage of the admixture was 0.13% - 0.15%;

[0111] Table 3 Concrete Results

[0112]

[0113] It can be seen from the concrete results that for the water-reducing agent examples CPCE-1 to 6, in the concrete system with mineral admixtures reaching about 60%, at a dosage of 0.13%, the slump flow is about 60 to 63 cm. While for the commercially available water-reducing agent and REF-1 of the same period, after increasing the dosage to 0.15%, the slump flow of their concrete is only 53 to 54 mm, and for REF-2, after increasing the dosage to 0.14%, the dispersion level barely approaches that of the examples CPCE-1 to 6. At the same time, regarding the compressive strength at 3d or 28d, due to better dispersion ability, small aggregate gaps, and high concrete density, the examples CPCE-1 to 6 exhibit higher compressive strength.

Claims

1. A diblock polymerization monomer, characterized in that, A polymerization monomer having a typical diblock structure, consisting of an unsaturated polyheterocyclic chain segment near the double bond end and a polyether polyol acrylate chain segment far from the double bond end; The unsaturated polyheterocyclic chain segment is derived from an unsaturated polyhybrid monomer, and the unsaturated polyhybrid monomer is selected from any one or a mixture of more than one of morpholine-based, piperazine-based, pyrrolidine-based unsaturated polyhybrid monomers; The polyether polyol acrylate chain segment is derived from the monomer polyether polyol acrylate, and the end of the polyether polyol acrylate is capped with methoxy.

2. The diblock polymerization monomer according to claim 1, characterized in that, The structure of the morpholine-based unsaturated polyhybrid monomer is shown in the general formula (Ⅰ), the structure of the piperazine-based unsaturated polyhybrid monomer is shown in the general formula (Ⅱ), and the structure of the pyrrolidine-based unsaturated polyhybrid monomer is shown in the general formula (Ⅲ). Among them, in each of the above general formulas, R1 is independently selected as an alkyl group of C1-C4 or -CO-, -COOCH2CH2-, -CONHCH2CH2-, -COOCH2-, -CONHCH2- or does not exist; The structure of the polyether polyol acrylate is shown in the general formula (Ⅳ): Among them, in the general formula (Ⅳ), n is an integer from 2 to 10, and R2-R4 are each independently an alkyl group of C1-C4 or -H.

3. A method for preparing the diblock polymerization monomer according to claim 1 or 2, characterized in that, It includes the following steps: (1) After at least three freeze-thaw cycles of an unsaturated polyheterocyclic monomer, a RAFT reagent, and a first batch of initiator Ⅰ in an anhydrous solvent, a polymerization reaction is carried out in a nitrogen atmosphere oil bath to obtain an intermediate, and the reaction is terminated after rapid quenching of free radicals in an ice-water bath; then, polyether polyol acrylate and a second batch of initiator Ⅰ are added, and after at least three freeze-thaw cycles, an oil bath reaction and purification are carried out in a nitrogen atmosphere to obtain a block intermediate; (2) Esterification reaction is carried out on the block intermediate, unsaturated alcohol, inhibitor, and catalyst obtained in step (1) under a water-carrying agent, and after the reaction is completed, the diblock polymerization monomer is prepared through purification; The molar ratio of the unsaturated polycyclic monomer, polyether polyol acrylate to the RAFT reagent in step (1) is 5-10:5-10:1; The molar amount ratio of the unsaturated alcohol to the block intermediate in step (2) is 1-1.1; The RAFT reagent in step (1) is a dithioester or trithioester containing a carboxyl group at one end; The unsaturated alcohol in step (2) has the following structural general formula (Ⅴ): Among them, R5, R6, and R7 are -CH3 or -H, and R8 is an alkyl group of C1-C4, -OCH2CH2-, -OCH2CH2OCH2CH2-, -OCH2CH2CH2CH2-.

4. The preparation method of the double-block polymerization monomer according to claim 3, wherein, The RAFT reagent in step (1) is selected from any one of 4-cyano-4-[(dodecylthio)thiocarbonylthio]pentanoic acid CDPA, 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid dithioester or trithioester, 4-cyano-4-(phenylthiocarbothioylthio)pentanoic acid (CPADB), 2-(ethyltrithiocarbonate)-2-methylpropanoic acid (EMP), (4-cyano-4-[(ethylthio)thiocarbonylthio]pentanoic acid (CETPA); The unsaturated alcohol described in step (2) is selected from any one of allyl alcohol, 2-butenol, 2-propenol, 2-methylallyl alcohol, 3-methyl-3-buten-1-ol, 4-penten-1-ol, ethylene glycol mono vinyl ether, and diethylene glycol mono vinyl ether.

5. The preparation method of the double-block polymerization monomer according to claim 3, characterized in that In step (1), the dosage of the first batch of initiator I is 0.1% - 2% of the mass of the unsaturated polyheterocyclic monomer, and the dosage of the second batch of initiator I is 0.1% - 2% of the mass of the polyether polyol acrylate; the initiator I is a peroxide initiator or an azo initiator, and the general structural formula of the peroxide initiator is R - O - O - H or R - O - O - R, where R is an alkyl group, an acyl group, or a carbonate group; In step (1), the amount of the anhydrous solvent is controlled so that the total mass concentration of the reactants is 30 - 80%, and it is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide, toluene, and N-methylpyrrolidone; The water-carrying agent described in step (2) is selected from any one of benzene, xylene, toluene, and chloroform, and the dosage is 1 - 3 times the total mass of the reactants in step (2); The catalyst described in step (2) is any one or a mixture of more than one of sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, dimethylsulfonic acid, sodium bisulfate monohydrate, solid superacid, and polyphosphoric acid, and the dosage is 1 - 10 wt% of the total mass of the reactants in step (2); The inhibitor described in step (2) is selected from any one of phenothiazine, p-benzoquinone, and p-tert-butylcatechol, and the dosage is 1 - 0.1% of the total mass of the reactants in step (2).

6. The preparation method of the double-block polymerization monomer according to claim 5, wherein, The peroxide initiator in the initiator I is selected from any one of benzoyl peroxide, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide; The azo initiator is selected from any one of azobisisobutyronitrile (AIBN), azobisisovaleronitrile (AMBN), azobisisoheptonitrile (ABVN), dimethyl azobisisobutyrate (AIBME), 2,2'-azobis(2,4,4-trimethylpentane), and 2-phenylazo-2,4-dimethyl-4-methoxypentanenitrile.

7. The preparation method of the double-block polymerization monomer according to claim 3, characterized in that The polymerization reaction temperature in step (1) is 50 - 90 °C, the polymerization reaction time is 1 - 12 h, the oil bath reaction time is 1 - 12 h, the oil bath reaction temperature is the same as the polymerization reaction temperature, and the mass concentration of the polymerization reactants is 30 - 80%; The purification method in step (1) is to distill or distill under reduced pressure to remove most of the solvent, precipitate 2 - 3 times in a precipitant, and dry for 1 - 24 h after centrifugation. The precipitant is selected from any one of ether, n-hexane, and petroleum ether, and the dosage is 2 - 3 times the total mass of the remaining substances after reduced pressure distillation; The esterification reaction temperature in step (2) is 70 - 170 °C, the esterification reaction time is 1 - 24 h, and the purification method in step (2) is the same as the purification method in step (1).

8. A polycarboxylate water reducer applicable to low-carbon cement using the diblock polymerization monomer described in claim 1 or 2 above, characterized in that, It is formed by free radical copolymerization of monomer A, monomer B, and monomer C. Its main chain adopts a multi-adsorption group of phosphate or phosphate ester and acrylic acid. The polyether polyol acrylate and the polyheterocyclic monomer form a branched side chain of a block, and a cyclic structure is introduced near the main chain end; The monomer A is the double-block polymerization monomer; The monomer B is an unsaturated carboxylic acid monomer, and its dosage is 3 to 6 times the molar amount of monomer A; The monomer C is a polymerizable phosphoric acid monomer, and its dosage is 0.5 to 2 times the molar amount of monomer A; The monomer C has the following general structural formula (Ⅵ): wherein R9, R 11 is selected from C1-C4 alkyl or -H, R 10 is selected from C1-C4 alkyl or -COOCH2-, -COOCH2CH2-, -COOCH2CH2CH2-, -CONHCH2-, -CONHCH2CH2-, -CONHCH2CH2CH2- or is absent; The weight-average molecular weight of the polycarboxylate water reducer is controlled at 10,000 to 40,000 Da.

9. The polycarboxylate water reducer applicable to low-carbon cement according to claim 8, characterized in that, The monomer B is selected from any one or a mixture of more than one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid or maleic anhydride; The monomer C is selected from any one of vinyl phosphoric acid, acryloyloxyethyl phosphate, acryloyloxypropyl phosphate, 2-methacryloyloxyethyl phosphate, 2-methacryloyloxypropyl phosphate, acrylamidoethyl phosphate, acrylamido-propyl phosphate, dimethyl vinyl phosphate, diethyl vinyl phosphate.

10. A method for preparing a polycarboxylate water reducer applicable to low-carbon cement according to claim 8 or 9, characterized in that, It includes: Monomer A, initiator II, and chain transfer agent are placed at a temperature of 25 to 80 °C in the presence of deionized water, and a mixed solution of monomer B, monomer C, and deionized water is added dropwise. The dropping reaction time is 1 to 8 h, and it is kept warm and cured for 1 to 8 h, and liquid alkali is added to adjust the pH to 6 to 7; The initiator II is a persulfate, a water-soluble azo initiator or a redox initiator.

11. According to the preparation method described in claim 10, wherein In the initiator II, the persulfate is ammonium persulfate, potassium persulfate or sodium persulfate, and its dosage is 0.1% - 5% of the total mass of the polymerization monomers; the water-soluble azo initiator is azodiisobutylamidine hydrochloride, azodiisobutimidazoline hydrochloride, azodicyanovaleric acid or azodiisopropylimidazoline, and its dosage is 0.1% - 3% of the total mass of the polymerization monomers; for the redox initiator, the oxidant is hydrogen peroxide or persulfate, and the reductant is ferrous salt, cuprous salt, sodium bisulfite, sodium thiosulfate, ascorbic acid or sodium formaldehyde sulfoxylate and other sulfates of sulfur below hexavalent, and its dosage is 0.5% - 3% of the total mass of the polymerization monomers, where the molar ratio of the oxidant to the reductant is 2 to 6:1; The chain transfer agent is any one of mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptobutanol, and its dosage is 0.5% - 5% of the total molar amount of the polymerization monomers.

12. A method for applying a polycarboxylate water reducer according to claim 8 or 9, which is applicable to low-carbon cement, characterized in that, The dosage of the polycarboxylate water reducer applicable to low-carbon cement used alone is 0.5‰ - 2‰ of the mass of the cementitious material.

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