An ether-based polycarboxylic acid slump-retaining agent, its preparation method and application

Abstract

The present invention relates to the technical field of concrete admixtures, and particularly relates to an ether-type polycarboxylic acid slump-retaining agent, a preparation method thereof, and an application thereof. The preparation method of the ether-type polycarboxylic acid slump-retaining agent includes subjecting vinyl phthalic acid and polyethylene glycol to an esterification reaction, and then subjecting the obtained esterification functional monomer to a radical polymerization reaction with an unsaturated polyether monomer, an unsaturated carboxylic acid monomer, and a carboxylic acid hydroxy ester monomer. The key of the present invention lies in carrying out radical copolymerization of an esterification functional monomer and a carboxylic acid hydroxy ester monomer having a specific structure with an unsaturated polyether monomer and an unsaturated carboxylic acid monomer. The polycarboxylic acid slump-retaining agent obtained thereby can reduce the sensitivity of concrete, improve the workability of concrete, improve the anti-sludge performance, reduce the slump loss, reduce the sensitivity to changes in raw materials, facilitate the pumping of manufactured sand concrete, pumped concrete, etc., and effectively improve the construction efficiency of concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to an ether polycarboxylic acid slump retaining agent, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the construction industry, the market demand for ready-mixed concrete is in short supply, and the development of concrete admixtures has entered a new era. The consumption of concrete and cement is increasing continuously. As one of the important admixtures for concrete, the polycarboxylic acid slump retaining agent is also a hot spot in the research and development of concrete.

[0003] The polycarboxylic acid slump retaining agent is a commonly used functional admixture in the production of concrete. Although the excellent slump retaining performance of the polycarboxylic acid slump retaining agent has been widely recognized in the industry at present, due to reasons such as the deteriorating quality of sand and stone materials (high mud content and stone powder content), the polycarboxylic acid slump retaining agent also has problems such as high sensitivity to raw material changes, too fast slump loss, and poor workability in actual applications. In addition, after decades of rapid urban construction development, the natural resources of concrete raw materials have been consumed greatly, and high-quality sand and stone resources are almost exhausted. It has become an inevitable trend to apply low-quality aggregates such as construction waste, machine-made sand, and natural sand and stone with high mud content to concrete. In the use process, the high sensitivity of the polycarboxylic acid slump retaining agent often leads to problems such as fast concrete loss and pipe blockage, seriously affecting the pumping construction performance of concrete, and further affecting the mechanical properties and durability in the later stage. Therefore, how to reduce the sensitivity of the polycarboxylic acid slump retaining agent to raw material changes while improving the slump retaining performance and workability has become an urgent technical problem to be solved. Summary of the Invention

[0004] One object of the present invention is to provide a preparation method of an ether polycarboxylic acid slump retaining agent with low sensitivity to raw materials and good slump retaining performance and workability.

[0005] Another object of the present invention is to provide an ether polycarboxylic acid slump retaining agent prepared by the above method.

[0006] A third object of the present invention is to provide an application of the above ether polycarboxylic acid slump retaining agent in the construction field.

[0007] The preparation method of the ether polycarboxylic acid slump retaining agent provided by the present invention includes the following steps:

[0008] S1. Perform an esterification reaction on vinyl phthalic acid and polyethylene glycol. The vinyl phthalic acid has the structure shown in formula (1) to obtain an esterification functional monomer;

[0009] S2. Carry out a radical polymerization reaction on an esterification functional monomer, an unsaturated polyether monomer, an unsaturated carboxylic acid monomer, and a carboxylic acid hydroxy ester monomer. The carboxylic acid hydroxy ester monomer contains compound A shown in formula (2-1) and compound B shown in formula (2-2). The resulting polymerization reaction product is an ether-type polycarboxylic acid slump-retaining agent.

[0010]

[0011] In formula (2-1), R 21 is H or an alkyl group with 1 to 5 carbon atoms, R 22 is an alkylene group with 0 to 4 carbon atoms, and R 23 is an alkylene group with 1 to 5 carbon atoms;

[0012] In formula (2-2), R 21 is H or an alkyl group with 1 to 5 carbon atoms, and R 23 is an alkylene group with 1 to 5 carbon atoms;

[0013] In formula (3), R 31 is an alkylene group with 1 - 5 carbon atoms, R 32 , R 33 and R 34 are each independently H, an alkyl group with 1 - 5 carbon atoms, or -OH, and n is an integer from 1 to 100.

[0014] The present invention also provides an ether-type polycarboxylic acid slump-retaining agent prepared by the above method.

[0015] The present invention also provides the application of the ether-type polycarboxylic acid slump-retaining agent in the construction field.

[0016] The key of the present invention lies in carrying out a radical copolymerization on an esterification functional monomer and a carboxylic acid hydroxy ester monomer with specific structures, an unsaturated polyether monomer, and an unsaturated carboxylic acid monomer. The resulting polycarboxylic acid slump-retaining agent can reduce the sensitivity of concrete, improve the workability of concrete, improve the anti-clay performance, reduce the slump loss, reduce the sensitivity to raw material changes, facilitate the pumping of manufactured sand concrete, pumped concrete, etc., and effectively improve the concrete construction efficiency. It is speculated that the reason may be as follows: The copolymerization of the above several monomers can not only make the side chains of the polycarboxylic acid slump-retaining agent molecule more extended, the steric hindrance effect more obvious, effectively reduce the viscosity of concrete, make it not easy to form intercalation adsorption with clay, improve the anti-clay performance, enhance the workability, reduce the sensitivity to raw material changes, but also can effectively compensate for the slump loss in the early stage, improve the slump-retaining performance of concrete, and extend the slump loss time of concrete. Specific Embodiments

[0017] The preparation method of the ether-type polycarboxylic acid slump-retaining agent provided by the present invention includes the following steps:

[0018] S1. Esterify vinyl phthalic acid with polyethylene glycol to obtain an esterified functional monomer;

[0019] S2. Carry out a radical polymerization reaction on the esterified functional monomer, an unsaturated polyether monomer, an unsaturated carboxylic acid monomer, and a carboxylic acid hydroxy ester monomer. The resulting polymerization reaction product is an ether-type polycarboxylic acid slump retaining agent.

[0020] In the present invention, the mass ratio of the unsaturated polyether monomer, the unsaturated carboxylic acid monomer, the esterified functional monomer, and the carboxylic acid hydroxy ester monomer is preferably 200:(5 - 10):(5 - 20):(10 - 30). Based on the amount of the unsaturated polyether monomer being 200 parts by weight, the amount of the unsaturated carboxylic acid monomer is preferably 5 - 10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value between them; the content of the esterified functional monomer is preferably 5 - 20 parts by weight, such as 5, 8, 10, 12, 15, 18, 20 parts by weight or any value between them; the content of the carboxylic acid hydroxy ester structural unit is preferably 10 - 30 parts by weight, such as 10, 12, 15, 18, 20, 22, 25, 28, 30 parts by weight or any value between them.

[0021] In the preparation process of the above esterified functional monomer, the molar ratio of vinyl phthalic acid to polyethylene glycol is preferably (2 - 4):1, such as 2:1, 2.5:1, 3:1, 3.5:1, 5:1 or any value between them.

[0022] In the preparation process of the above esterified functional monomer, vinyl phthalic acid has the structure shown in formula (1), and its specific examples include but are not limited to: 4-vinyl-1,2-benzenedicarboxylic acid.

[0023]

[0024] In the preparation process of the above esterified functional monomer, the specific examples of polyethylene glycol include but are not limited to at least one of PEG-200, PEG-400, PEG-600, PEG-800, and PEG-1000.

[0025] In the preparation process of the above esterified functional monomer, the conditions of the esterification reaction preferably include a temperature of 80°C - 100°C, such as 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C, 100°C or any value between them; and a time of 1 - 5 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value between them.

[0026] In the preparation process of the above esterification functional monomer, the esterification reaction is preferably carried out in the presence of a catalyst and an inhibitor. Among them, the catalyst can be various existing substances capable of catalyzing the esterification reaction, and specific examples thereof include but are not limited to at least one of concentrated sulfuric acid, p-toluenesulfonic acid, stannous oxide, and dibutyltin oxide. The dosage of the catalyst preferably accounts for 1% - 3% of the total mass of vinyl benzenedicarboxylic acid and polyethylene glycol, such as 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3% or any value between them. Specific examples of the inhibitor include but are not limited to at least one of p-methoxyphenol, hydroquinone, and phenothiazine. The dosage of the inhibitor preferably accounts for 0.1% - 2% of the total mass of vinyl benzenedicarboxylic acid and polyethylene glycol, such as 1%, 1.2%, 1.5%, 1.8%, 2% or any value between them.

[0027] In the present invention, the carboxylic acid hydroxy ester monomer contains compound A represented by formula (2-1) and compound B represented by formula (2-2). Among them, the mass ratio of compound A to compound B in the carboxylic acid hydroxy ester monomer is preferably 1:(2 - 4), such as 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8, 1:4 or any value between them. Using compound A and compound B in combination according to this preferred ratio has the advantage of strong slump retention ability for a long time.

[0028]

[0029] In formula (2-1), R 21 is H or an alkyl group with 1 - 5 carbon atoms, R 22 is an alkylene group with 0 - 4 carbon atoms, R 23 is an alkylene group with 1 - 5 carbon atoms. In formula (2-2), R 21 is H or an alkyl group with 1 - 5 carbon atoms, R 23 is an alkylene group with 1 - 5 carbon atoms. Among them, specific examples of the alkyl group with 1 - 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. Specific examples of the alkylene group with 0 - 4 carbon atoms include but are not limited to: absent, methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene or tert-butylene. Specific examples of the alkylene group with 1 - 5 carbon atoms include but are not limited to: methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. In the present invention, the unsaturated polyether monomer preferably has the structure shown in formula (3):

[0030]

[0031] In formula (3), R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34 are each independently H, an alkyl group having 1 to 5 carbon atoms or -OH, and n is an integer from 1 to 100. Among them, specific examples of the alkylene group having 1 to 5 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene, isopropylidene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. Specific examples of the alkyl group having 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 be 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or any value between them. In a preferred embodiment, R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34 are all H, and n is an integer from 20 to 60. The unsaturated polyether macromonomer can be at least one of vinyl polyoxyethylene ether, methyl vinyl polypropylene glycol ether, ethylene glycol mono vinyl polyethylene glycol ether (EPEG) and 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG). In addition, the number average molecular weight of the unsaturated polyether macromonomer is preferably 1200 to 6000, such as 1200, 1400, 1600 or any value between them.

[0032] In the present invention, the unsaturated carboxylic acid monomer preferably has the structure shown in formula (4):

[0033]

[0034] In formula (4), R 41 and R 42 are each independently H, an alkyl group having 1 to 5 carbon atoms or -R 43 -COOH and at least one of R 41 and R 42 is -R 43 -COOH, R 43 is an alkylene group having 0 to 5 carbon atoms; when R 41 and R 42 are both -R 43 -COOH, R 41 and R 42 can form a ring by bonding; R 41 `and R 42Each independently is H or an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group having 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. Specific examples of the alkylene group having 0 to 5 carbon atoms include, but are not limited to: absent, methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. Specific examples of the alkylene group having 1 to 5 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. When R 41 and R 42 are both -R 43 -COOH, R 41 and R 42 can form a ring by bonding, and an acid anhydride is formed at this time. Considering the availability of raw materials, the unsaturated carboxylic acid is particularly preferably at least one selected from acrylic acid, methacrylic acid, itaconic acid and maleic anhydride.

[0035] The present invention does not particularly limit the type of initiator used in the radical polymerization reaction, and it can be at least one selected from azo-type initiators, peroxide-type initiators and redox-type initiators. Among them, specific examples of the azo-type initiator include, but are not limited to: at least one of dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, azodicarbonamide, 2,2'-azobis(2-isopropylimidazoline) hydrochloride, 2-cyano-2-propylazoformamide, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(isopentanenitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile). Specific examples of the peroxide-type initiator include, but are not limited to: at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide and tert-butyl peroxybenzoate. The redox-type initiator includes an oxidizing agent and a reducing agent, and specific examples thereof include, but are not limited to: at least one of sulfate-sulfite, persulfate-thiourea, persulfate-organic salt and ammonium persulfate-fatty amine. Among them, the sulfate-sulfite can be at least one selected from sodium sulfate-sodium sulfite, potassium sulfate-potassium sulfite and ammonium sulfate-ammonium sulfite. The persulfate-thiourea can be at least one selected from sodium persulfate-thiourea, potassium persulfate-thiourea and ammonium persulfate-thiourea. The persulfate-organic salt can be at least one selected from sodium persulfate-potassium acetate, potassium persulfate-potassium acetate and ammonium persulfate-ammonium acetate. The ammonium persulfate-fatty amine can be ammonium persulfate-N,N-tetramethylethylenediamine and / or ammonium persulfate-diethylamine. The radical polymerization reaction preferably uses a redox-type initiator.

[0036] In a preferred embodiment, the manner of the radical polymerization reaction includes:

[0037] S1`: Dissolve the unsaturated polyether monomer and the oxidant in water to obtain a substrate;

[0038] S2`: Drop the A solution and the B solution into the substrate respectively for polymerization reaction. The A solution is a reducing agent solution, and the B solution is a mixed solution of an esterification functional monomer, an unsaturated carboxylic acid monomer, a carboxylic acid hydroxy ester monomer and a molecular weight regulator. The product obtained after the reaction is the ether-type polycarboxylic acid slump retaining agent.

[0039] In the preparation process of the above-mentioned ether-type polycarboxylic acid slump retaining agent, specific examples of the oxidant include but are not limited to at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, benzoyl peroxide and tert-butyl hydroperoxide, and preferably a mixture of two or more. Specific examples of the reducing agent include but are not limited to at least one of ascorbic acid, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 1,1'-azobis(cyclohexanecarbonitrile), sodium bisulfite, sodium sulfite, sodium metabisulfite, sodium formaldehyde sulfoxylate, ferrous sulfate heptahydrate, sodium hypophosphite, sodium phosphite and ammonium ferrous sulfate, and preferably a mixture of two or more. The dosage of the oxidant is preferably 1% - 5% of the total mass of the unsaturated polyether monomer, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value between them. The dosage of the reducing agent is preferably 0.1% - 2% of the total mass of the unsaturated polyether monomer, such as 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2% or any value between them.

[0040] In the preparation process of the above-mentioned ether-type polycarboxylic acid slump retaining agent, the molecular weight regulator is preferably a thiol compound, and more preferably selected from one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol and mercaptopropanol. In addition, the dosage of the molecular weight regulator is preferably 1% - 5% of the total mass of the unsaturated polyether monomer, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value between them.

[0041] In the preparation process of the above-mentioned ether-type polycarboxylic acid slump retaining agent, the A solution and the B solution are dropped into the substrate respectively for free radical polymerization reaction. Among them, the dropping time of the A solution is preferably 120 - 180 min, such as 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min or any value between them. The dropping time of the B solution is preferably 120 - 180 min, such as 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min or any value between them.

[0042] In the preparation process of the above-mentioned ether-type polycarboxylic acid slump-retaining agent, the conditions of the radical polymerization reaction preferably include a temperature of 15 to 40 °C, such as 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C or any value between them; the reaction time after the solution is added dropwise is 20 to 60 min, such as 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min or any value between them.

[0043] The present invention also provides an ether-type polycarboxylic acid slump-retaining agent prepared by the above method.

[0044] The ether-type polycarboxylic acid slump-retaining agent provided by the present invention includes a polyether structural unit, a carboxylic acid structural unit, an esterification functional structural unit, and a carboxylic acid hydroxy ester structural unit. Among them, the mass ratio of the polyether structural unit, the carboxylic acid structural unit, the esterification functional structural unit, and the carboxylic acid hydroxy ester structural unit is 200:(5 - 10):(5 - 20):(10 - 30). Based on the content of the polyether structural unit being 200 parts by weight, the content of the carboxylic acid structural unit is 5 to 10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value between them; the content of the esterification functional structural unit is 5 to 20 parts by weight, such as 5, 8, 10, 12, 15, 18, 20 parts by weight or any value between them; the content of the carboxylic acid hydroxy ester structural unit is 10 to 30 parts by weight, such as 10, 12, 15, 18, 20, 22, 25, 28, 30 parts by weight or any value between them.

[0045] In the present invention, the esterification functional structural unit has at least one of the structures shown in Formula (5-1), Formula (5-2), and Formula (5-3):

[0046]

[0047]

[0048]

[0049] In Formula (5-1) to Formula (5-3), n is an integer from 1 to 100, such as 1, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or any value between them.

[0050] In the present invention, the carboxylic acid hydroxy ester structural unit has the structures shown in Formula (6-1) and Formula (6-2).

[0051]

[0052]

[0053] In formula (6-1), R 21 is H or an alkyl group having 1 to 5 carbon atoms, R 22 is an alkylene group having 0 to 4 carbon atoms, R 23 is an alkylene group having 1 to 5 carbon atoms. In formula (6-2), R 21 is H or an alkyl group having 1 to 5 carbon atoms, R 23 is an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkyl group having 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. Specific examples of the alkylene group having 0 to 5 carbon atoms include, but are not limited to: absent, methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. Specific examples of the alkylene group having 0 to 4 carbon atoms include, but are not limited to: absent, methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene or tert-butylene.

[0054] In the present invention, the polyether structural unit preferably has the structure shown in formula (7):

[0055]

[0056] In formula (7), R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34 are each independently H, an alkyl group having 1 to 5 carbon atoms or -OH, and n is an integer from 1 to 100. Among them, specific examples of the alkylene group having 1 to 5 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene or neopentylene. Specific examples of the alkyl group having 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 be 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or any value between them. In a preferred embodiment, R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34All are H, and n is an integer from 20 to 60. The polyether structural unit is formed by polymerizing unsaturated polyether monomers. The unsaturated polyether macromonomer can be at least one of vinyl polyoxyethylene ether, methyl vinyl polypropylene glycol ether, ethylene glycol mono vinyl polyethylene glycol ether (EPEG), and 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG). In addition, the number average molecular weight of the unsaturated polyether macromonomer is preferably 1200 to 6000, such as 1200, 1400, 1600, or any value between them.

[0057] In the present invention, the carboxylic acid structural unit has the structure shown in formula (8):

[0058]

[0059] In formula (8), R 41 and R 42 are each independently H, an alkyl group having 1 to 5 carbon atoms, or -R 43 -COOH, and at least one of R 41 and R 42 is -R 43 -COOH, R 43 does not exist or is an alkylene group having 1 to 5 carbon atoms; when R 41 and R 42 are both -R 43 -COOH, R 41 and R 42 can form a ring by bonding; R 41 ` and R 42 ` are each independently H or an alkyl group having 1 to 5 carbon atoms. Among them, specific examples of the alkyl group having 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. Specific examples of the alkylene group having 1 to 5 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, or neopentylene. When R 41 and R 42 are both -R 43 -COOH, R 41 and R 42 can form a ring by bonding, and an acid anhydride is formed at this time. The carboxylic acid structural unit is formed by polymerizing unsaturated carboxylic acids. Among them, specific examples of the unsaturated carboxylic acid include, but are not limited to: at least one of acrylic acid, methacrylic acid, itaconic acid, and maleic anhydride.

[0060] In the present invention, the ether-type polycarboxylate slump retaining agent is preferably a random copolymer.

[0061] In the present invention, the number-average molecular weight of the ether-type polycarboxylic acid slump-retaining agent is preferably 5,000 to 80,000, such as 5,000, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000 or any value therebetween.

[0062] The present invention also provides an application of the above ether-type polycarboxylic acid slump-retaining agent in the construction field.

[0063] The present invention will be described in detail below through examples.

[0064] In the following examples and comparative examples, the parts of raw materials are all by weight.

[0065] Example 1

[0066] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid and PEG-200 at a molar ratio of 2:1, add 3% p-toluenesulfonic acid and 2% p-methoxyphenol, and carry out an esterification reaction at 90 °C for 3 h under nitrogen protection to obtain an esterification functional monomer D1;

[0067] S2. Polymerization reaction: By mass, add 200 parts of vinyl polyethylene glycol ether (having the structure shown in formula (3), wherein R 31 is an ethylene group, R 32 is H, R 33 is H, R 34 is H, and the number-average molecular weight is 2,400) and 100 parts of water into a reaction kettle. After stirring and dispersing evenly, add 1 part of hydrogen peroxide at one time and react at 25 °C for 10 min, and then dropwise add solution A and solution B. Among them, solution A is 10 parts of a 10% sodium hypophosphite solution by mass concentration. Solution B is a mixed solution composed of 20 parts of esterification functional monomer D1, 6 parts of acrylic acid, 6 parts of 2-hydroxyethyl 4-vinylbenzoate (compound A), 12 parts of 2-hydroxybutyl methacrylate (compound B) and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and after the dropping is completed, continue to react for 30 min to obtain the ether-type polycarboxylic acid slump-retaining agent BT-1.

[0068] Example 2

[0069] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid and PEG-400 at a molar ratio of 3:1, add 2% stannous oxide and 2% hydroquinone, and carry out an esterification reaction at 80 °C for 4 h under nitrogen protection to obtain an esterification functional monomer D2;

[0070] S2. Polymerization reaction: By mass, add 200 parts of methyl vinyl polypropylene glycol ether (having the structure shown in formula (3), wherein R 31is propylene, R 32 is H, R 33 is H, R 34 is methyl, the number average molecular weight is 3000), and 100 parts of water were added to the reaction kettle. After being stirred and dispersed evenly, 2 parts of ammonium persulfate were added at one time. After reacting at 30 °C for 10 min, solution A and solution B were added dropwise. Among them, solution A is 10 parts of an L-ascorbic acid solution with a mass concentration of 5%. Solution B is a mixed solution composed of 20 parts of esterification functional monomer D2, 5 parts of itaconic acid, 3 parts of hydroxypropyl 4-propenylbenzoate (compound A), 7 parts of hydroxypropyl methacrylate (compound B), and 4 parts of mercaptoethanol. The dropping time of solution A is 180 min, the dropping time of solution B is 180 min, and after the dropping is completed, the reaction continues for 30 min to obtain the ether-type polycarboxylic acid slump retaining agent BT-2.

[0071] Example 3

[0072] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid with PEG-600 at a molar ratio of 4:1, add 2% of dibutyltin oxide and 0.2% of phenothiazine, and carry out the esterification reaction at 100 °C for 2 h under nitrogen protection to obtain the esterification functional monomer D3;

[0073] S2. Polymerization reaction: By mass, add 200 parts of ethylene glycol mono vinyl polyethylene glycol ether (number average molecular weight is 4000) and 100 parts of water to the reaction kettle. After being stirred and dispersed evenly, add 3 parts of hydrogen peroxide at one time, react at 20 °C for 10 min, and then add solution A and solution B dropwise. Among them, solution A is 20 parts of a sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 5 parts of esterification functional monomer D3, 8 parts of methacrylic acid, 6 parts of hydroxyethyl 4-methylpropenylbenzoate (compound A), 20 parts of hydroxypropyl acrylate (compound B), and 5 parts of sulfonated mercaptopropionic acid. The dropping time of solution A is 160 min, the dropping time of solution B is 160 min, and after the dropping is completed, the reaction continues for 30 min to obtain the ether-type polycarboxylic acid slump retaining agent BT-3.

[0074] Example 4

[0075] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid with PEG-400 at a molar ratio of 3:1, add 1% of concentrated sulfuric acid and 0.8% of phenothiazine, and carry out the esterification reaction at 90 °C for 3 h under nitrogen protection to obtain the esterification functional monomer D4;

[0076] S2. Polymerization reaction: 200 parts of 4-hydroxybutyl vinyl polyethylene glycol ether (number average molecular weight is 6000) and 100 parts of water are added to a reaction kettle by mass. After being stirred and dispersed evenly, 5 parts of ammonium persulfate are added at one time, and the reaction is carried out at 15 °C for 10 min, and then solution A and solution B are added dropwise. Among them, solution A is 10 parts of L-ascorbic acid solution with a mass concentration of 1%. Solution B is a mixed solution composed of 5 parts of esterification functional monomer D4, 10 parts of maleic acid, 7 parts of 4-butenyl-hydroxybutyl benzoate (compound A), 15 parts of hydroxyethyl acrylate (compound B) and 1 part of mercaptopropionic acid. The dropping time of solution A is 120 min, the dropping time of solution B is 120 min, and after the dropping is completed, the reaction continues for 30 min to obtain the ether-type polycarboxylate slump retaining agent BT-4.

[0077] Comparative Example 1

[0078] The ether-type polycarboxylate slump retaining agent is prepared according to the method of Example 1, except that the esterification functional monomer is not prepared and not added, and the other conditions are the same as those in Example 1. The specific steps are as follows:

[0079] 200 parts of vinyl polyethylene glycol ether and 100 parts of water are added to a reaction kettle by mass. After being stirred and dispersed evenly, 1 part of hydrogen peroxide is added at one time, and the reaction is carried out at 25 °C for 10 min, and then solution A and solution B are added dropwise. Among them, solution A is 10 parts of sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 6 parts of acrylic acid, 6 parts of 4-vinyl-hydroxyethyl benzoate (compound A), 12 parts of hydroxybutyl methacrylate (compound B) and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and after the dropping is completed, the reaction continues for 30 min to obtain the ether-type polycarboxylate slump retaining agent DBT-1.

[0080] Comparative Example 2

[0081] The ether-type polycarboxylate slump retaining agent is prepared according to the method of Example 1, except that 4-vinyl-hydroxyethyl benzoate (compound A) is replaced with the same weight part of hydroxybutyl methacrylate (compound B), and the other conditions are the same as those in Example 1. The specific steps are as follows:

[0082] S1. Esterification reaction: 4-vinyl-1,2-benzenedicarboxylic acid and PEG-200 are mixed at a molar ratio of 2:1, 3% of p-toluenesulfonic acid and 2% of p-hydroxyanisole are added, and under nitrogen protection, the esterification reaction is carried out at 90 °C for 3 h to obtain the esterification functional monomer D1;

[0083] S2. Polymerization reaction: Add 200 parts of vinyl polyethylene glycol ether and 100 parts of water by mass to a reaction kettle. After stirring and dispersing evenly, add 1 part of hydrogen peroxide at one time, react at 25 °C for 10 min, and then dropwise add solution A and solution B. Among them, solution A is 10 parts of a sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 20 parts of esterification functional monomer D1, 6 parts of acrylic acid, 18 parts of hydroxybutyl methacrylate (compound B), and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and continue to react for 30 min after dropping, then the ether-type polycarboxylate slump-retaining agent DBT-2 is obtained.

[0084] Comparative Example 3

[0085] Prepare the ether-type polycarboxylate slump-retaining agent according to the method of Example 1. The difference is that in the preparation process of the esterification functional monomer, 4-vinyl-1,2-benzenedicarboxylic acid is replaced with the same molar amount of methacrylic acid, and the other conditions are the same as those in Example 1. The specific steps are as follows:

[0086] S1. Esterification reaction: Mix methacrylic acid and PEG-200 in a molar ratio of 2:1, add 3% of p-toluenesulfonic acid and 2% of p-hydroxyanisole, and carry out an esterification reaction at 90 °C for 3 h under nitrogen protection to obtain the esterification functional monomer D5;

[0087] S2. Polymerization reaction: Add 200 parts of vinyl polyethylene glycol ether and 100 parts of water by mass to a reaction kettle. After stirring and dispersing evenly, add 1 part of hydrogen peroxide at one time, react at 25 °C for 10 min, and then dropwise add solution A and solution B. Among them, solution A is 10 parts of a sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 20 parts of esterification functional monomer D5, 6 parts of acrylic acid, 6 parts of 2-hydroxyethyl 4-vinylbenzoate (compound A), 12 parts of hydroxybutyl methacrylate (compound B), and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and continue to react for 30 min after dropping, then the ether-type polycarboxylate slump-retaining agent DBT-3 is obtained.

[0088] Comparative Example 4

[0089] Prepare the ether-type polycarboxylate slump-retaining agent according to the method of Example 1. The difference is that 2-hydroxyethyl 4-vinylbenzoate (compound A) is replaced with the same weight parts of polyethylene glycol dimethacrylate (number average molecular weight is 1332), and the other conditions are the same as those in Example 1. The specific steps are as follows:

[0090] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid with PEG-200 at a molar ratio of 2:1, add 3% p-toluenesulfonic acid and 2% p-hydroxyanisole, and carry out the esterification reaction at 90 °C for 3 h under nitrogen protection to obtain the esterification functional monomer D1;

[0091] S2. Polymerization reaction: Add 200 parts of vinyl polyethylene glycol ether and 100 parts of water to the reaction kettle by mass. After stirring and dispersing evenly, add 1 part of hydrogen peroxide at one time, react at 25 °C for 10 min, and then dropwise add solution A and solution B. Among them, solution A is 10 parts of a sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 20 parts of the esterification functional monomer D1, 6 parts of acrylic acid, 6 parts of polyethylene glycol dimethacrylate, 12 parts of hydroxybutyl methacrylate (compound B), and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and continue to react for 30 min after dropping to obtain the ether-type polycarboxylate slump retaining agent DBT-4.

[0092] Comparative Example 5

[0093] Prepare the ether-type polycarboxylate slump retaining agent according to the method of Example 1. The difference is that in the preparation process of the esterification functional monomer, PEG-200 is replaced with methoxypolyethylene glycol MPEG-200 with the same molar amount, and the other conditions are the same as those in Example 1. The specific steps are as follows:

[0094] S1. Esterification reaction: Mix 4-vinyl-1,2-benzenedicarboxylic acid with MPEG-200 at a molar ratio of 2:1, add 3% p-toluenesulfonic acid and 2% p-hydroxyanisole, and carry out the esterification reaction at 90 °C for 3 h under nitrogen protection to obtain the esterification functional monomer D6;

[0095] S2. Polymerization reaction: Add 200 parts of vinyl polyethylene glycol ether and 100 parts of water to the reaction kettle by mass. After stirring and dispersing evenly, add 1 part of hydrogen peroxide at one time, react at 25 °C for 10 min, and then dropwise add solution A and solution B. Among them, solution A is 10 parts of a sodium hypophosphite solution with a mass concentration of 10%. Solution B is a mixed solution composed of 20 parts of the esterification functional monomer D6, 6 parts of acrylic acid, 6 parts of hydroxyethyl 4-vinylbenzoate (compound A), 12 parts of hydroxybutyl methacrylate (compound B), and 2 parts of mercaptoacetic acid. The dropping time of solution A is 150 min, the dropping time of solution B is 150 min, and continue to react for 30 min after dropping to obtain the ether-type polycarboxylate slump retaining agent DBT-5.

[0096] Test Example 1

[0097] (1) The net paste fluidity of the polycarboxylate slump-retaining agents obtained in the above examples and comparative examples was tested according to GB / T 8077-2012 "Test Methods for Homogeneity of Concrete Admixtures" under different dosages and water consumption. Among them, during the test of different dosages, the cement dosage was 300 g and the water dosage was 87 g, and the results are shown in Table 1. During the test of different water consumption, the cement dosage was 300 g and the slump-retaining agent dosage was 2.0%, and the results are shown in Table 2.

[0098] Table 1

[0099]

[0100]

[0101] Table 2

[0102]

[0103]

[0104] It can be seen from the test results in Table 1 and Table 2 that the polycarboxylate slump-retaining agent provided by the present invention is less sensitive in terms of dosage and water consumption.

[0105] Test Example 2

[0106] 60 g of the ether-type polycarboxylate slump-retaining agents obtained in the above examples and comparative examples were respectively mixed evenly with 140 g of water-reducing agent PCE (purchased from Kezhijie New Materials Group Co., Ltd., brand name Point-7408) and 800 g of water to obtain test samples. The test samples were made of Conch Cement, and according to GB 8076-2008 "Concrete Admixtures", the initial slump and spread of the concrete, as well as the slump and spread over time and the concrete state were measured. The concrete mix ratio was: cement 230 kg / m 3 , fly ash (Grade II) 90 kg / m 3 , manufactured sand 850 kg / m 3 (mud content is 8%), stone (5 - 31.5) mm) 1050 kg / m 3 , and the initial spread was controlled within 550 ± 10 mm, and the obtained results are shown in Table 3.

[0107] Table 3

[0108]

[0109] It can be seen from the test results in Table 3 that the dosage of the ether-based polycarboxylate slump-retaining agent provided by the present invention is low, and the slump loss over time is small. This polycarboxylate slump-retaining agent can improve the slump-retaining performance of concrete, reduce the slump loss during the pumping process, and has advantages such as good workability, good wrapping property, fast flow rate, and good anti-sludge effect. It can improve the pumping efficiency of concrete, improve the workability of concrete at the same time, and avoid problems such as pipe blockage caused by large late-stage loss of concrete.

[0110] 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 preparation method of an ether polycarboxylate slump retaining agent, characterized in that, The method includes: S1. Esterify vinyl phthalic acid with polyethylene glycol. The vinyl phthalic acid has the structure shown in formula (1) to obtain an esterified functional monomer; S2. Carry out a radical polymerization reaction on the esterified functional monomer, an unsaturated polyether monomer, an unsaturated carboxylic acid monomer, and a carboxylic acid hydroxy ester monomer. The carboxylic acid hydroxy ester monomer contains compound A shown in formula (2-1) and compound B shown in formula (2-2). The unsaturated polyether monomer has the structure shown in formula (3). The obtained polymerization reaction product is an ether-type polycarboxylate slump retaining agent; In formula (2-1), R 21 is H or an alkyl group having 1 to 5 carbon atoms, R 22 is an alkylene group having 0 to 4 carbon atoms, R 23 is an alkylene group having 1 to 5 carbon atoms; In formula (2-2), R 21 is H or an alkyl group having 1 to 5 carbon atoms, and R 23 is an alkylene group having 1 to 5 carbon atoms; In formula (3), R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34 are each independently H, an alkyl group having 1 to 5 carbon atoms or -OH, and n is an integer from 1 to 100.

2. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The mode of the radical polymerization reaction includes: S1`. Dissolve the unsaturated polyether monomer and an oxidant in water to obtain a substrate; S2`. Drop the A solution and the B solution into the substrate respectively for polymerization reaction. The A solution is a reducing agent solution, and the B solution is a mixed solution of an esterified functional monomer, an unsaturated carboxylic acid monomer, a carboxylic acid hydroxy ester monomer, and a molecular weight regulator. The product obtained after the reaction is an ether-type polycarboxylate slump retaining agent.

3. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The mass ratio of the unsaturated polyether monomer, the unsaturated carboxylic acid monomer, the esterified functional monomer, and the carboxylic acid hydroxy ester monomer is 200:(5-10):(5-20):(10-30).

4. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, In the preparation process of the esterified functional monomer, the molar ratio of vinyl phthalic acid to polyethylene glycol is (2-4):

1.

5. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The vinyl phthalic acid is 4-vinyl-1,2-benzenedicarboxylic acid.

6. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The polyethylene glycol is selected from at least one of PEG-200, PEG-400, PEG-600, PEG-800, and PEG-1000.

7. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The conditions of the esterification reaction include a temperature of 80°C to 100°C and a time of 1 to 5 h.

8. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The esterification reaction is carried out in the presence of a catalyst and an inhibitor.

9. The preparation method of the ether polycarboxylate slump retaining agent according to claim 8, characterized in that, The catalyst is selected from at least one of concentrated sulfuric acid, p-toluenesulfonic acid, stannous oxide, and dibutyltin oxide.

10. The preparation method of the ether polycarboxylate slump retaining agent according to claim 8, characterized in that, The dosage of the catalyst accounts for 1% to 3% of the total mass of vinyl phthalic acid and polyethylene glycol.

11. The preparation method of the ether polycarboxylate slump retaining agent according to claim 8, characterized in that, The inhibitor is selected from at least one of p-methoxyphenol, hydroquinone, and phenothiazine.

12. The preparation method of the ether polycarboxylate slump retaining agent according to claim 8, characterized in that, The dosage of the inhibitor accounts for 0.1% to 2% of the total mass of vinyl phthalic acid and polyethylene glycol.

13. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that, The unsaturated polyether monomer is selected from at least one of vinyl polyoxyethylene ether, methyl vinyl polypropylene glycol ether, ethylene glycol mono vinyl polyethylene glycol ether, and 4-hydroxybutyl vinyl polyethylene glycol ether.

14. The preparation method of the ether polycarboxylate slump retaining agent according to claim 1, characterized in that,The unsaturated carboxylic acid monomer has the structure shown in formula (4): In formula (4), R 41 and R 42 are each independently H, an alkyl group having 1 to 5 carbon atoms, or -R 43 -COOH, and at least one of R 41 and R 42 is -R 43 -COOH, R 43 is an alkylene group having 0 to 5 carbon atoms; when both R 41 and R 42 are -R 43 -COOH, R 41 and R 42 can form a ring by bonding; R 41 ` and R 42 ` are each independently H or an alkyl group having 1 to 5 carbon atoms.

15. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 14, characterized in that, The unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, and maleic acid.

16. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 1, characterized in that, The mass ratio of compound A to compound B in the carboxylic acid hydroxy ester monomer is 1:(2-4).

17. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, benzoyl peroxide, and tert-butyl hydroperoxide.

18. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The reducing agent is selected from at least one of ascorbic acid, sodium bisulfite, sodium sulfite, sodium metabisulfite, sodium formaldehyde sulfoxylate, ferrous sulfate heptahydrate, sodium hypophosphite, sodium phosphite, and ammonium ferrous sulfate.

19. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The molecular weight regulator is a thiol compound.

20. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The molecular weight regulator is selected from at least one of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol.

21. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The dosage of the oxidizing agent is 1% to 5% of the total mass of the unsaturated polyether monomer.

22. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The dosage of the reducing agent is 0.1% to 2% of the total mass of the unsaturated polyether monomer.

23. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The dosage of the molecular weight regulator is 1% to 5% of the total mass of the unsaturated polyether monomer.

24. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The dropping time of the solution A is 120 to 180 min.

25. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The dropping time of the solution B is 120 to 180 min.

26. The preparation method of the ether-based polycarboxylic acid slump retaining agent according to claim 2, characterized in that, The conditions of the polymerization reaction include an initial dropping temperature of 15 to 35 °C and a reaction time of 20 to 60 min after the solution is completely dropped.

27. The ether-based polycarboxylic acid slump retaining agent prepared by the method according to any one of claims 1 to 26.

28. The ether-based polycarboxylic acid slump retaining agent according to claim 27, characterized in that, The ether-type polycarboxylate slump retaining agent includes a polyether structural unit, a carboxylic acid structural unit, an esterification functional structural unit, and a carboxylic acid hydroxy ester structural unit; the esterification functional structural unit has a structure shown in at least one of formula (5-1), formula (5-2), and formula (5-3); the carboxylic acid hydroxy ester structural unit has a structure shown in formula (6-1) and formula (6-2); the polyether structural unit has a structure shown in formula (7); the carboxylic acid structural unit has a structure shown in formula (8); In formula (5-1) to formula (5-3), n is an integer from 1 to 100; In formula (6-1), R 21 is H or an alkyl group having 1 to 5 carbon atoms, R 22 is an alkylene group having 0 to 4 carbon atoms, R 23 is an alkylene group having 1 to 5 carbon atoms; In formula (6-2), R 21 is H or an alkyl group having 1 to 5 carbon atoms, and R 23 is an alkylene group having 1 to 5 carbon atoms; In formula (7), R 31 is an alkylene group having 1 to 5 carbon atoms, R 32 , R 33 and R 34 are each independently H, an alkyl group having 1 to 5 carbon atoms or -OH, and n is an integer from 1 to 100; In formula (8), R 41 and R 42 are each independently H, an alkyl group having 1 to 5 carbon atoms, or -R 43 -COOH, and at least one of R 41 and R 42 is -R 43 -COOH, R 43 is absent or is an alkylene group having 1 to 5 carbon atoms; when both R 41 and R 42 are -R 43 -COOH, R 41 and R 42 can be bonded to form a ring; R 41 ` and R 42 ` are each independently H or an alkyl group having 1 to 5 carbon atoms.

29. Use of the ether polycarboxylate slump retaining agent according to claim 27 or 28 in the construction field.

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