Viscosity reduction type water reducing agent as well as preparation method and application thereof

Abstract

The invention belongs to the field of concrete admixtures, and particularly relates to a viscosity reduction type water reducer as well as a preparation method and application thereof. The viscosity reduction type water reducer contains a monomer A structural unit, a monomer B structural unit, an ether macromonomer structural unit and an unsaturated acid structural unit. The viscosity reduction type water reducing agent provided by the invention has the advantages of good viscosity reduction effect and good wrapping property and softness on concrete slurry under the condition of low cement consumption, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of concrete admixtures, and particularly relates to a viscosity-reducing water reducer, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing global emphasis on environmental protection, carbon emission reduction and carbon neutrality have become important goals for all industries. As one of the main sources of carbon emissions, the construction industry's efforts in carbon emission reduction are crucial for the sustainable development of the entire industry. Reducing the cement dosage, as an effective means to achieve carbon emission reduction, has been widely recognized and applied. Cement is the main raw material of concrete, but a large amount of carbon dioxide is generated during its production. By reducing the cement dosage, the construction industry can reduce its dependence on cement, thereby reducing carbon emissions. However, in order to achieve the same design strength, reducing the cement dosage may increase the use of other materials, such as fly ash, slag powder, stone powder, or other cementitious materials, and at the same time, the water consumption needs to be reduced. The use of these alternative materials and the reduction of water consumption may greatly affect the workability of concrete, such as dispersibility and viscosity.

[0003] To solve this problem, it is particularly important to develop a viscosity-reducing water reducer that can reduce the viscosity and improve the workability of concrete under low cement dosage or low water consumption conditions, making it easier to mix and construct. This will help improve the production efficiency of the construction industry and also contribute to carbon emission reduction and carbon neutrality.

[0004] CN112608423A discloses a viscosity-reducing and mud-resistant polycarboxylate water reducer, which first esterifies and grafts a strongly hydrophobic rigid structure end-functional monomer, and then copolymerizes with 3-hydroxypropyl vinyl polyoxyethylene ether, unsaturated acid, and other small monomers. The resulting polycarboxylate water reducer can obtain excellent viscosity-reducing effects, excellent mud-resistant properties, and low sensitivity to the dosage under the synergistic action of various groups, but the wrapping and softness of the concrete paste still cannot be satisfied.

[0005] CN116554413A discloses a polycarboxylate-based water reducer with special functional structural units obtained by controlling the molecular weight of the macromonomer. By controlling the side chain length and the ester group of the functional structural unit, the adsorption capacity and surface tension can be regulated, and a significant viscosity-reducing effect can be achieved while maintaining the fluidity of the cement paste and the workability of the concrete, realizing a high water reduction rate, but the wrapping and softness of the concrete paste are poor. Summary of the Invention

[0006] The first object of the present invention is to provide a new viscosity-reducing water reducer, which has the advantages of good viscosity-reducing effect and good wrapping and softness of the concrete paste under low cement dosage.

[0007] The second object of the present invention is to provide a preparation method of a viscosity-reducing water reducing agent.

[0008] The third object of the present invention is to provide a viscosity-reducing water reducing agent prepared by the above method.

[0009] The fourth object of the present invention is to provide the application of the above viscosity-reducing water reducing agent in the construction field.

[0010] Specifically, the viscosity-reducing water reducing agent provided by the present invention contains a monomer A structural unit, a monomer B structural unit, an ether macromonomer structural unit and an unsaturated acid structural unit. The monomer A structural unit has the structure shown in formula (1), and the monomer B structural unit has the structure shown in formula (2);

[0011]

[0012] In formula (1), R1 is -(CH2) n -, n is an integer from 1 to 4; R2 is -(CH2) n` -, n` is an integer from 5 to 15; R3, R3` and R3`` are each independently H or an alkyl group having 1 to 5 carbon atoms; n1 is an integer from 10 to 30;

[0013] In formula (2), R4 is H or an alkyl group having 1 to 5 carbon atoms; R5 is -(CH2)a-, a is an integer from 1 to 3; R6 is -(CH2) b - or -(CH2) b NH-, b is an integer from 0 to 3; R7 is H or an alkyl group having 1 to 5 carbon atoms.

[0014] The preparation method of the viscosity-reducing water reducing agent provided by the present invention includes carrying out a polymerization reaction on monomer A, monomer B, an ether macromonomer and an unsaturated acid in the presence of a radical initiator and a chain transfer agent, and then the viscosity-reducing water reducing agent is obtained; the monomer A has the structure shown in formula (3), and the monomer B has the structure shown in formula (4);

[0015]

[0016] In formula (3), R1 is -(CH2) n -, n is an integer from 1 to 4; R2 is -(CH2) n` -, n` is an integer from 5 to 15; R3, R3` and R3`` are each independently H or an alkyl group having 1 to 5 carbon atoms; n1 is an integer from 10 to 30;

[0017] In formula (4), R4 is H or an alkyl group having 1 to 5 carbon atoms; R5 is -(CH2)a-, a is an integer from 1 to 3; R6 is -(CH2) b - or -(CH2) bNH-, where b is an integer from 0 to 3; R7 is H or an alkyl group with 1 to 5 carbon atoms.

[0018] The key of the present invention lies in simultaneously introducing a low-molecular-weight vinyl polyoxyethylene ether modified by a long-chain alkyl hydrophobic group (structural unit of monomer A), an asymmetric bisamide structure (structural unit of monomer B), a polyether macromonomer structural unit, and an unsaturated acid structural unit into the polycarboxylate water reducer. The viscosity-reducing water reducer obtained thereby has good viscosity-reducing effects at low cement dosages and has the advantages of good wrapping and softness for concrete paste. Presumably, the reasons may be as follows: On the one hand, the introduction of the low-molecular-weight vinyl polyoxyethylene ether modified by a long-chain alkyl hydrophobic group can adjust the molecular conformation of the polycarboxylate water reducer, effectively reduce the surface tension of the paste, improve the particle lubrication effect, thereby effectively reducing the plastic viscosity of the concrete. At the same time, the esterified end group of the long-chain alkyl will gradually hydrolyze during use to release hydroxyalkanoic acid. Hydroxyalkanoic acid has hydrophilic and hydrophobic groups and has the effect of stabilizing bubbles in the paste, which can further reduce the viscosity of the paste to achieve a continuous viscosity-reducing effect, and hydroxyalkanoic acid also has an antibacterial effect, which can effectively extend the storage time of the viscosity-reducing water reducer. On the other hand, the simultaneous introduction of the asymmetric bisamide structure can effectively lock in moisture, enable the water reducer to adsorb on the particle surface to form a more solid water film layer, endow the water reducer with better viscosity-reducing effects, and during use, the ester group hydrolyzes and gradually releases amido acid compounds and polyethylene glycol. Polyethylene glycol and amido acid compounds can lock in the free water in the paste to make the paste more plump, thereby improving the wrapping and softness of the concrete; the viscosity-reducing water reducer prepared by copolymerizing the low-molecular-weight vinyl polyoxyethylene ether modified by a long-chain alkyl hydrophobic group (monomer A), the asymmetric bisamide structure (monomer B), the polyether macromonomer, and the unsaturated acid has short side chains and contains rich hydrophobic groups and water-retaining groups, which can adjust the hydrophilic-lipophilic balance value of the molecule, effectively reduce the viscosity of the concrete and improve the workability of the concrete. In summary, the viscosity-reducing water reducer provided by the present invention can effectively reduce the viscosity of high-strength concrete, improve the wrapping and softness of the concrete, enhance the workability effect, and the product can be produced at room temperature, is green, low-carbon, and environmentally friendly, and has broad application prospects. Detailed implementation manners

[0019] The viscosity-reducing water reducer provided by the present invention contains a monomer A structural unit, a monomer B structural unit, an ether macromonomer structural unit, and an unsaturated acid structural unit. Preferably, the above structural units are obtained by random copolymerization to obtain the viscosity-reducing water reducer. Among them, the mass ratio of the monomer A structural unit, the monomer B structural unit, the ether macromonomer structural unit, and the unsaturated acid structural unit is preferably (50-100):(2-10):(50-150):(20-35). Specifically, the content of the monomer A structural unit is preferably 50-100 parts by weight, such as 50, 60, 70, 80, 90, 100 parts by weight or any value therebetween; the content of the monomer B structural unit is preferably 2-10 parts by weight, such as 2, 4, 6, 8, 10 parts by weight or any value therebetween; the content of the ether macromonomer structural unit is preferably 50-150 parts by weight, such as 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 parts by weight or any value therebetween; the content of the unsaturated acid structural unit is preferably 20-35 parts by weight, such as 20, 28, 30, 32, 35 parts by weight or any value therebetween.

[0020] In the present invention, the structure of the monomer A structural unit is shown in formula (1):

[0021]

[0022] In formula (1), R1 is -(CH2) n -, n is an integer from 1 to 4; R2 is -(CH2) n` -, n` is an integer from 5 to 15; R3, R3` and R3`` are each independently H or an alkyl group of C1-C5; n1 is an integer from 10 to 30. Among them, specific examples of the alkyl group of C1-C5 include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. n can specifically be 1, 2, 3 or 4. n` can specifically be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15. n1 can specifically be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 or 30.

[0023] In the present invention, the structure of the monomer B structural unit is shown in formula (2):

[0024]

[0025] In formula (2), R4 is H or an alkyl group of C1-C5; R5 is -(CH2)a-, a is an integer from 1 to 3; R6 is -(CH2) b - or -(CH2) bNH-, where b is an integer from 0 to 3; R7 is H or an alkyl group with 1 to 5 carbon atoms. Specific examples of the alkyl group with 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. a can be 1, 2 or 3. b is 0, 1, 2 or 3.

[0026] In the present invention, the structural unit of the ether macromonomer is derived from an ether macromonomer, that is, a structural unit obtained by polymerizing a polyether macromonomer. The ether macromonomer is preferably methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether. In addition, the number average molecular weight of the ether macromonomer is preferably 1000 to 1500, such as 1000, 1100, 1200, 1300, 1400, 1500 or any value between them.

[0027] In the present invention, the structural unit of the unsaturated acid is derived from an unsaturated acid monomer, that is, a structural unit obtained by polymerizing an unsaturated acid monomer. The unsaturated carboxylic acid is preferably at least one selected from acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

[0028] In the present invention, the viscosity-reducing water reducer is preferably a random copolymer.

[0029] In the present invention, in the above formulas, "*" represents the bonding end.

[0030] The preparation method of the viscosity-reducing water reducer provided by the present invention includes polymerizing monomer A, monomer B, an ether macromonomer and an unsaturated acid in the presence of a radical initiator and a chain transfer agent to obtain the viscosity-reducing water reducer.

[0031] In the preparation process of the viscosity-reducing water reducer provided by the present invention, monomer A has the structure shown in formula (3):

[0032]

[0033] In formula (3), R1 is -(CH2) n -, n is an integer from 1 to 4; R2 is -(CH2) n` -, n` is an integer from 5 to 15; R3, R3` and R3`` are each independently H or an alkyl group with 1 to 5 carbon atoms; n1 is an integer from 10 to 30. Specific examples of the alkyl group with 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. n can specifically be 1, 2, 3 or 4. n` can specifically be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15. n1 can specifically be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 or 30.

[0034] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the source of monomer A is not particularly limited. It can be obtained through commercial purchase or prepared by various existing methods. In a preferred embodiment, monomer A is prepared by the first esterification reaction of unsaturated polyoxyethylene ether and hydroxyalkanoic acid. Among them, the molar ratio of the unsaturated polyoxyethylene ether to the hydroxyalkanoic acid is preferably (1.05 - 1.1):1, such as 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.1:1 or any value between them. The unsaturated polyoxyethylene ether is preferably methylallyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether. The unsaturated polyoxyethylene ether can be prepared by methods well-known in the art or obtained through commercial purchase. For example, it can be purchased from unsaturated polyoxyethylene ethers of Ouke Chemical Co., Ltd. and Fujian Zhongshan Chemical Co., Ltd. Specific examples of the hydroxyalkanoic acid include, but are not limited to, at least one of hydroxy nonanoic acid, hydroxy decanoic acid, hydroxy undecanoic acid, and hydroxy dodecanoic acid. The first esterification reaction is generally carried out in the presence of catalyst I and inhibitor I. Among them, the conditions of the first esterification reaction preferably include a temperature of 100 - 120 °C, such as 100 °C, 102 °C, 104 °C, 106 °C, 108 °C, 110 °C, 112 °C, 114 °C, 116 °C, 118 °C, 120 °C or any value between them; the time is 4 - 12 h, such as 4 h, 6 h, 8 h, 10 h, 12 h or any value between them. Catalyst I can be various existing compounds that can increase the reaction rate, such as at least one of concentrated sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, strongly acidic cation exchange resin, Lewis acid, etc. The dosage of catalyst I is preferably 0.2 - 5% of the mass of the unsaturated polyoxyethylene ether, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value between them. Inhibitor I can be various existing compounds that can inhibit the polymerization reaction, including but not limited to at least one of phenolic inhibitors, ether inhibitors, quinone inhibitors, aromatic amine inhibitors, etc. Examples of the phenolic inhibitor include at least one of hydroquinone, p-tert-butylcatechol, pyrogallol, 2,6-di-tert-butyl-p-cresol, 4,4'-dihydroxybiphenyl, bisphenol A, etc. Examples of the ether inhibitor include p-methoxyphenol. Examples of the quinone inhibitor include at least one of p-benzoquinone, tetrachlorobenzoquinone, naphthoquinone, anthraquinone, etc. Examples of the aromatic amine inhibitor include at least one of phenothiazine, p-phenylenediamine, p-toluidine, diphenylamine, methylaniline, benzidine, β-naphthylamine, N-nitrosodiphenylamine, etc. The dosage of inhibitor I is preferably 0.01 - 1% of the mass of the unsaturated polyoxyethylene ether, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1% or any value between them.

[0035] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the monomer B has the structure shown in formula (4):

[0036]

[0037] In formula (4), R4 is H or an alkyl group with 1 to 5 carbon atoms; R5 is -(CH2)a-, where a is an integer from 1 to 3; R6 is -(CH2) b - or -(CH2) b NH-, where b is an integer from 0 to 3; R7 is H or an alkyl group with 1 to 5 carbon atoms. Among them, specific examples of the alkyl group with 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or neopentyl. a can be 1, 2 or 3. b is 0, 1, 2 or 3.

[0038] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the source of the monomer B is not particularly limited, and it can be obtained through commercial purchase or prepared by various existing methods. In a preferred embodiment, the monomer B is prepared by a second esterification reaction of an unsaturated hydroxyamide and an amic acid compound. Among them, the molar ratio of the unsaturated hydroxyamide to the amic acid compound is preferably (1.05 - 1.1):1, such as 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.1:1 or any value therebetween. Specific examples of the unsaturated hydroxyamide include, but are not limited to, at least one of N-hydroxymethylacrylamide, N-(hydroxymethyl)methacrylamide, N-hydroxyethylacrylamide, N-(hydroxyethyl)methacrylamide, N-hydroxypropylacrylamide, and N-(hydroxypropyl)methacrylamide. Specific examples of the amic acid compound include, but are not limited to, at least one of oxamic acid, butyramic acid, and N-methylsuccinamic acid. The second esterification reaction is generally carried out in the presence of a catalyst II and an inhibitor II. Among them, the conditions of the second esterification reaction preferably include a temperature of 100 - 120°C, such as 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C, 120°C or any value therebetween; and a time of 4 - 12 h, such as 4 h, 6 h, 8 h, 10 h, 12 h or any value therebetween. The catalyst II can be various existing compounds that can increase the reaction rate, and examples include at least one of concentrated sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, strongly acidic cation exchange resin, Lewis acid, etc. The dosage of the catalyst II is preferably 0.2 - 5% of the mass of the unsaturated polyoxyethylene ether, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value therebetween. The inhibitor II can be various existing compounds that can inhibit the polymerization reaction, including but not limited to at least one of phenolic inhibitors, ether inhibitors, quinone inhibitors, aromatic amine inhibitors, etc. Examples of the phenolic inhibitor include at least one of hydroquinone, p-tert-butylcatechol, pyrogallol, 2,6-di-tert-butyl-p-cresol, 4,4'-dihydroxybiphenyl, bisphenol A, etc. Examples of the ether inhibitor include p-methoxyphenol. Examples of the quinone inhibitor include at least one of p-benzoquinone, tetrachlorobenzoquinone, naphthoquinone, anthraquinone, etc. Examples of the aromatic amine inhibitor include at least one of phenothiazine, p-phenylenediamine, p-toluidine, diphenylamine, methylaniline, benzidine, β-naphthylamine, N-nitrosodiphenylamine, etc. The dosage of the inhibitor II is preferably 0.01 - 1% of the mass of the unsaturated polyoxyethylene ether, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1% or any value therebetween.

[0039] In the present invention, the terms "first esterification reaction" and "second esterification reaction" are merely used to distinguish the esterification reactions occurring at different positions for the convenience of description and have no other special meanings. The terms "catalyst I" and "catalyst II" are merely used to distinguish the catalysts used at different positions for the convenience of description and have no other special meanings. The terms "polymerization inhibitor I" and "polymerization inhibitor II" are merely used to distinguish the polymerization inhibitors used at different positions for the convenience of description and have no other special meanings.

[0040] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the ether macromonomer is preferably methallyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether. In addition, the number-average molecular weight of the ether macromonomer is preferably 1000 to 1500, such as 1000, 1100, 1200, 1300, 1400, 1500 or any value therebetween. The ether macromonomer can be prepared by methods well known in the art or obtained by commercial purchase. For example, the ether macromonomer can be purchased from Ouke Chemical Co., Ltd. and Fujian Zhongshan Chemical Co., Ltd.

[0041] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the unsaturated acid is preferably at least one selected from acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

[0042] In the preparation process of the viscosity-reducing water reducer provided by the present invention, the mass ratio of monomer A, monomer B, the ether macromonomer and the unsaturated acid is preferably (50 to 100):(2 to 10):(50 to 150):(20 to 35). Specifically, the dosage of monomer A is preferably 50 to 100 parts by weight, such as 50, 60, 70, 80, 90, 100 parts by weight or any value therebetween; the dosage of monomer B is preferably 2 to 10 parts by weight, such as 2, 4, 6, 8, 10 parts by weight or any value therebetween; the dosage of the ether macromonomer is preferably 50 to 150 parts by weight, such as 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 parts by weight or any value therebetween; the dosage of the unsaturated acid is preferably 20 to 35 parts by weight, such as 20, 28, 30, 32, 35 parts by weight or any value therebetween.

[0043] The present invention has no particular limitation on the type of free radical initiator, which can be selected from at least one of azo initiators, peroxide initiators, and redox initiators, preferably redox initiators. Among them, specific examples of the oxidant in the redox initiator include, but are not limited to, at least one of hydrogen peroxide, sodium persulfate, and ammonium persulfate. Specific examples of the reductant in the redox initiator include, but are not limited to, at least one of ascorbic acid, sodium formaldehyde sulfoxylate, and sodium bisulfite. The dosage of the free radical initiator is preferably 0.1-2.0% of the total mass of monomer A, monomer B, ether macromonomer, and unsaturated acid, such as 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt% or any value between them.

[0044] In the preparation process of the viscosity-reducing water reducer provided by the present invention, specific examples of the chain transfer agent include, but are not limited to, at least one of mercaptoethanol, mercaptopropionic acid, and mercaptoacetic acid. In addition, the dosage of the chain transfer agent is preferably 0.1-2.0% of the total mass of monomer A, monomer B, ether macromonomer, and unsaturated acid, such as 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2% or any value between them.

[0045] In a specific embodiment, the preparation process of the viscosity-reducing water reducer includes mixing monomer A, polyether macromonomer, and water evenly, controlling the temperature of the resulting mixture at 25°C to 35°C, and then dropping a mixed solution of monomer B and unsaturated acid, a mixed solution of chain transfer agent and reductant, and an oxidant solution into the reaction system within 1-2.5 h. After the dropping is completed, continue the heat preservation reaction for 0.5-5 h. After the reaction is completed, adjust the pH value to 6-8 to obtain the viscosity-reducing water reducer.

[0046] The present invention also provides a viscosity-reducing water reducer prepared by the above method.

[0047] In addition, the present invention also provides the application of the above viscosity-reducing water reducer in the construction field.

[0048] The present invention will be described in detail below through examples.

[0049] Preparation Example 1-1

[0050] Mix isopentenyl polyethylene glycol ether (TPEG-2400, (CH3)2C=CHCH2(OCH2CH2) nOH), hydroxy nonanoic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) were added to a reactor equipped with a condensation device. The molar ratio of TPEG-2400 to hydroxy nonanoic acid was 1.05:1. The amount of the catalyst was 1.5% of the mass of TPEG-2400, and the amount of the inhibitor was 0.5% of the mass of TPEG-2400. The reaction was carried out at a constant temperature of 100 °C for 12 h under nitrogen protection. After the reaction, the temperature was lowered to 40 °C to obtain monomer A1.

[0051] Preparation Example 1-2

[0052] Isopentenyl polyoxyethylene ether (TPEG-2400, (CH3)2C=CHCH2(OCH2CH2) n OH), hydroxy decanoic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) were added to a reactor equipped with a condensation device. The molar ratio of TPEG-2400 to hydroxy decanoic acid was 1.1:1. The amount of the catalyst was 1.5% of the mass of TPEG-2400, and the amount of the inhibitor was 0.5% of the mass of TPEG-2400. The reaction was carried out at a constant temperature of 120 °C for 4 h under nitrogen protection. After the reaction, the temperature was lowered to 40 °C to obtain monomer A2.

[0053] Preparation Example 1-3

[0054] Isopentenyl polyoxyethylene ether (TPEG-2400, (CH3)2C=CHCH2(OCH2CH2) n OH), hydroxy undecanoic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) were added to a reactor equipped with a condensation device. The molar ratio of TPEG-2400 to hydroxy undecanoic acid was 1.05:1. The amount of the catalyst was 1.5% of the mass of TPEG-2400, and the amount of the inhibitor was 0.5% of the mass of TPEG-2400. The reaction was carried out at a constant temperature of 110 °C for 8 h under nitrogen protection. After the reaction, the temperature was lowered to 40 °C to obtain monomer A3.

[0055] Preparation Example 1-4

[0056] Isopentenyl polyoxyethylene ether (TPEG-2400, (CH3)2C=CHCH2(OCH2CH2) n OH), hydroxy dodecanoic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) were added to a reactor equipped with a condensation device. The molar ratio of TPEG-2400 to hydroxy dodecanoic acid was 1.05:1. The amount of the catalyst was 1.5% of the mass of TPEG-2400, and the amount of the inhibitor was 0.5% of the mass of TPEG-2400. The reaction was carried out at a constant temperature of 100 °C for 5 h under nitrogen protection. After the reaction, the temperature was lowered to 40 °C to obtain monomer A4.

[0057] Preparation Example 2-1

[0058] Add N - hydroxymethylacrylamide, oxamic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) into a reactor equipped with a condensation device. The molar ratio of N - hydroxymethylacrylamide to oxamic acid is 1.05:1. The dosage of the catalyst is 1.5% of the mass of N - hydroxymethylacrylamide, and the dosage of the inhibitor is 0.5% of the mass of N - hydroxymethylacrylamide. React at a constant temperature of 100 °C for 12 h under nitrogen protection. After the reaction, cool down to 40 °C to obtain monomer B1.

[0059] Preparation Example 2 - 2

[0060] Add N - hydroxymethylacrylamide, butyramic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) into a reactor equipped with a condensation device. The molar ratio of N - hydroxymethylacrylamide to butyramic acid is 1.08:1. The dosage of the catalyst is 1.5% of the mass of N - hydroxymethylacrylamide, and the dosage of the inhibitor is 0.5% of the mass of N - hydroxymethylacrylamide. React at a constant temperature of 120 °C for 4 h under nitrogen protection. After the reaction, cool down to 40 °C to obtain monomer B2.

[0061] Preparation Example 2 - 3

[0062] Add N - hydroxymethylacrylamide, N - methylsuccinic acid, a catalyst (concentrated sulfuric acid), and an inhibitor (hydroquinone) into a reactor equipped with a condensation device. The molar ratio of N - hydroxymethylacrylamide to N - methylsuccinic acid is 1.1:1. The dosage of the catalyst is 1.5% of the mass of N - hydroxymethylacrylamide, and the dosage of the inhibitor is 0.5% of the mass of N - hydroxymethylacrylamide. React at a constant temperature of 110 °C for 6 h under nitrogen protection. After the reaction, cool down to 40 °C to obtain monomer B3.

[0063] Examples 1 - 4

[0064] Place monomer A, polyether macromonomer, and water in a reactor. Control the temperature of the solution in the reactor at 30 °C. Then, dropwise add a mixed solution of monomer B and unsaturated acid, a mixed solution of chain transfer agent and reducing agent, and an oxidant solution into the reactor within 2 h. After the dropping is completed, continue the heat - preservation reaction for 2 h. After the reaction, adjust the pH value to 7 to obtain a viscosity - reducing water - reducing agent. Among them, the dosages of each raw material are shown in Table 1.

[0065] Table 1

[0066]

[0067] In Table 1, the dosages of each raw material are in parts by weight.

[0068] Comparative Example 1

[0069] Commercially available standard - type high - performance water - reducing agent.

[0070] Comparative Example 2

[0071] The viscosity-reducing water reducer was prepared according to the method of Example 1, except that monomer A was replaced with polyether macromonomer (TPEG-1200) in the same weight portion, and monomer B was not added, and the other conditions were the same as those in Example 1, and a viscosity-reducing water reducer was obtained.

[0072] Comparative Example 3

[0073] The viscosity-reducing water reducer was prepared according to the method of Example 1, except that monomer A was replaced with polyether macromonomer (TPEG-1200) in the same weight portion, and the other conditions were the same as those in Example 1, and a viscosity-reducing water reducer was obtained.

[0074] Comparative Example 4

[0075] The viscosity-reducing water reducer was prepared according to the method of Example 1, except that monomer B was not added, and the other conditions were the same as those in Example 1, and a viscosity-reducing water reducer was obtained.

[0076] Test Example

[0077] Using Hongshi Cement, adjusting the dosage of the admixture to make the slump flow of the concrete be (570±20) mm, according to GB8076-2008 "Concrete Admixtures", the effects of the water reducer on the initial and 1h slump flow, 0h inverted slump cone emptying time and compressive strength at each age of the concrete were tested. The concrete mix ratio was: cement 170 kg / m 3 , fly ash 90 kg / m 3 , slag powder 60 kg / m 3 , sand 925 kg / m 3 , stone 950 kg / m 3 , water 155 kg / m 3 . The test results of the concrete are shown in Table 2.

[0078] Table 2

[0079]

[0080] It can be seen from the results in Table 1 that the viscosity-reducing water reducer obtained by polymerizing monomer A, monomer B, polyether macromonomer and unsaturated acid has a shorter emptying time and faster flow rate at low cement dosage, indicating good viscosity-reducing effect, and the softness and wrapping property of the paste are better, and there is no negative impact on the strength.

[0081] Comparative Example 1 was the concrete prepared with a conventional water reducer, which had a large material weight, high viscosity, and the static paste was prone to caking, and the workability was poor.

[0082] Comparative Example 2: Monomer A was replaced with the same weight portion of polyether macromonomer and monomer B was not added. The slump-reducing water reducer obtained had an extended evacuation time and a slower flow rate compared to Example 1, and the paste wrapping property was poor.

[0083] Comparative Example 3: Based on Comparative Example 2, monomer B was introduced, and the paste wrapping property was improved, and the paste became softer.

[0084] Comparative Example 4: Based on Comparative Example 2, monomer A was introduced, and the flow rate was improved.

[0085] From the above results, it can be seen that the introduction of monomer A and monomer B can more effectively improve the flow rate and paste state. The paste is soft and has a fast flow rate, but the loss of the mother liquor containing low molecular weight HPEG is large. In addition, the slump-reducing water reducer provided by the present invention for low water-binder ratio or low water consumption has obvious effects in improving the workability and flow rate of concrete, and has no negative impact on the strength.

[0086] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A viscosity reducing water reducing agent, characterized in that: The viscosity-reducing water-reducing agent contains a monomer A structural unit, a monomer B structural unit, an ether macromonomer structural unit and an unsaturated acid structural unit, wherein the monomer A structural unit has a structure shown in formula (1), and the monomer B structural unit has a structure shown in formula (2); In formula (1), R1 is -(CH2) n -, n is an integer of 1 to 4; R2 is -(CH2) n` -, n` is an integer from 5 to 15; R3, R3` and R3`` are each independently H or a C1 to C5 alkyl group; n1 is an integer from 10 to 30; In formula (2), R4 is H or a C1-C5 alkyl group; R5 is -(CH2)a-, where a is an integer from 1 to 3; R6 is -(CH2) b -or-(CH2) b NH-, b is an integer from 0 to 3; R7 is H or a C1 to C5 alkyl group.

2. The viscosity-reducing water-reducing agent according to claim 1, characterized in that: The mass ratio of the monomer A structural unit, the monomer B structural unit, the ether macromonomer structural unit and the unsaturated acid structural unit is (50-100):(2-10):(50-150):(20-35).

3. The viscosity-reducing water-reducing agent according to claim 1, characterized in that: The ether macromonomer structural unit is derived from an ether macromonomer, and the ether macromonomer is methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether; the number average molecular weight of the ether macromonomer is 1000-1500.

4. The viscosity-reducing water-reducing agent according to claim 1, characterized in that: The unsaturated acid structural unit is derived from an unsaturated carboxylic acid, and the unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

5. A method for preparing a viscosity-reducing water-reducing agent, characterized in that: The method comprises subjecting monomer A, monomer B, ether macromonomer and unsaturated acid to polymerization reaction in the presence of a free radical initiator and a chain transfer agent to obtain the viscosity-reducing water-reducing agent; the monomer A has a structure shown in formula (3), and the monomer B has a structure shown in formula (4); In formula (3), R1 is -(CH2) n -, n is an integer of 1 to 4; R2 is -(CH2) nˋ -, nˋ is an integer from 5 to 15; R3, R3ˋ and R3ˋˋ are each independently H or a C1 to C5 alkyl group; n1 is an integer from 10 to 30; In formula (4), R4 is H or a C1-C5 alkyl group; R5 is -(CH2)a-, where a is an integer from 1 to 3; R6 is -(CH2) b -or-(CH2) b NH-, b is an integer from 0 to 3; R7 is H or a C1 to C5 alkyl group.

6. The method for preparing the viscosity-reducing water-reducing agent according to claim 5, characterized in that: The monomer A is prepared by a first esterification reaction of unsaturated polyoxyethylene ether and hydroxyalkanoic acid; Preferably, the molar ratio of the unsaturated polyoxyethylene ether to the hydroxyalkanoic acid is (1.05-1.1):1; Preferably, the unsaturated polyoxyethylene ether is methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether; Preferably, the hydroxyalkanoic acid is selected from at least one of hydroxynonacid, hydroxydecanoic acid, hydroxyundecanoic acid and hydroxydodecanoic acid; Preferably, the first esterification reaction is carried out in the presence of catalyst I and inhibitor I, and the conditions of the first esterification reaction include a temperature of 100 to 120° C. and a time of 4 to 12 hours; Preferably, the amount of the catalyst I is 0.2-5% of the mass of the unsaturated polyoxyethylene ether, and the amount of the inhibitor I is 0.01-1% of the mass of the unsaturated polyoxyethylene ether.

7. The method for preparing the viscosity-reducing water-reducing agent according to claim 5, characterized in that: The monomer B is prepared by a second esterification reaction of an unsaturated hydroxyamide and an amic acid compound; Preferably, the molar ratio of the unsaturated hydroxyamide and the amic acid compound is (1.05-1.1):1; Preferably, the unsaturated hydroxyamide is selected from at least one of N-hydroxymethyl acrylamide, N-(hydroxymethyl)methacrylamide, N-hydroxyethyl acrylamide, N-(hydroxyethyl)methacrylamide, N-hydroxypropyl acrylamide and N-(hydroxypropyl)methacrylamide; Preferably, the amic acid compound is selected from at least one of oxamic acid, butyramic acid and N-methylsuccinamic acid; Preferably, the second esterification reaction is carried out in the presence of catalyst II and inhibitor II, and the conditions of the second esterification reaction include 100-120° C. and a time of 4-12 h; Preferably, the amount of the catalyst II is 0.2-5% of the mass of the unsaturated hydroxyamide, and the amount of the inhibitor II is 0.01-1% of the mass of the unsaturated hydroxyamide.

8. The method for preparing the viscosity-reducing water-reducing agent according to claim 5, characterized in that: The ether macromonomer is methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether; Preferably, the unsaturated acid is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride and itaconic acid; Preferably, the free radical initiator is a redox initiator, the oxidant in the redox initiator is selected from at least one of hydrogen peroxide, sodium persulfate and ammonium persulfate, and the reducing agent in the redox initiator is selected from at least one of ascorbic acid, sodium formaldehyde sulfoxylate and sodium bisulfite; Preferably, the chain transfer agent is selected from at least one of mercaptoethanol, mercaptopropionic acid and thioglycolic acid.

9. A viscosity-reducing water-reducing agent prepared by the method according to any one of claims 5 to 8.

10. Use of the viscosity-reducing water-reducing agent according to any one of claims 1 to 4 and 9 in the field of construction.

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