Low-sensitivity polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of building admixtures, and discloses a low-sensitivity polycarboxylate superplasticizer as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a polyether macromonomer, a crosslinking monomer and a first solvent to obtain a first solution; mixing a reducing agent, a chain transfer agent and a second solvent to obtain a solution A; mixing an unsaturated carboxylic acid monomer, an esterification monomer and a third solvent to obtain a solution B; mixing an oxidizing agent and a fourth solvent to obtain a solution C; the esterified monomer is obtained by carrying out esterification reaction on polyethylene glycol, p-toluenesulfonic acid and 3, 7-dimethyl-6-octenoic acid; and mixing the solution A, the solution B, the solution C and the first solution for reaction, and adjusting the pH value of the obtained reaction solution to 5-7 to obtain the low-sensitivity polycarboxylic acid water reducer. The low-sensitivity polycarboxylic acid water reducing agent can solve the problems that an additive is more sensitive due to performance difference of machine-made sand, large stone powder content and relatively high MB value, so that concrete is too large in gradual loss, bleeding and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of building admixtures, and particularly relates to a low-sensitivity polycarboxylate water-reducing agent and a preparation method and application thereof. Background Art

[0002] In recent years, commercial concrete mixing stations have generally reported that admixtures are sensitive, and concrete often suffers large losses. Increasing the proportion of slump-preventing agents leads to more serious concrete bleeding and worse workability. Therefore, how to solve problems such as admixture sensitivity, excessive concrete slump loss, excessive bleeding, and poor workability has become one of the issues that urgently need to be solved.

[0003] CN113060968A discloses a high water-reducing and low-sensitivity polycarboxylate water-reducing agent and a preparation method thereof. The preparation method comprises the following steps: S1: raw material preparation: weighing the following raw materials in parts by weight: 7-11 parts of sodium lignin sulfonate, 21-25 parts of calcium chloride, 18-22 parts of perlite, 9-13 parts of defoamer, 19-23 parts of isopentanol polyoxyethylene ether, 4-8 parts of phenol, 17-21 parts of formaldehyde, 14-18 parts of citric acid, 22-26 parts of volcanic ash and 13-17 parts of water; S2: preparing a first mixed solution: adding the sodium lignin sulfonate and calcium chloride described in S1 into a reactor for stirring and heating to obtain a first mixed solution; S3: calcining and soaking: calcining the perlite described in S1, and after the calcination is completed, acid-soaking and alkali-soaking the perlite in turn to obtain a high water-reducing and low-sensitivity polycarboxylate water-reducing agent. This method effectively improves the compressive strength of concrete and improves the durability of concrete, but the research direction is mainly in the strength aspect, and the process is relatively complicated, the manufacturing cost is high, the manufacturing time is long, and the energy consumption is too high.

[0004] CN106046269A discloses a cross-linked low-sensitivity ester-ether copolymerized polycarboxylic acid water-reducing agent and a preparation method thereof, wherein the polycarboxylic acid water-reducing agent is copolymerized by 4-hydroxybutyl vinyl polyoxyethylene ether, unsaturated acid, unsaturated phosphoric acid monoester and unsaturated phosphoric acid diester, and has high water reduction rate, high slump retention, high workability, mud resistance and low dosage sensitivity under the synergistic effect of various groups. However, the method does not study the sensitivity of materials, such as different types of machine-made sand.

[0005] At present, it has become a trend in the concrete industry to replace natural sand with artificial sand. Compared with natural sand, artificial sand has many problems such as poor particle grading, unstable performance of different batches of artificial sand, high stone powder content, and high MB value, which makes admixtures more sensitive, and often causes problems such as excessive concrete loss over time and water seepage. Summary of the invention

[0006] The purpose of the present invention is to solve the problems that the admixture is more sensitive due to many problems such as poor particle grading of machine-made sand, unstable performance of machine-made sand of different batches, large stone powder content, high MB value, etc., resulting in excessive loss of concrete over time and water seepage.

[0007] In a first aspect, the present invention provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, the preparation method comprising:

[0008] Step (1): mixing a polyether macromonomer, a cross-linking monomer and a first solvent to obtain a first solution;

[0009] Step (2): mixing a reducing agent, a chain transfer agent and a second solvent to obtain a liquid A; mixing an unsaturated carboxylic acid monomer, an esterification monomer and a third solvent, wherein the esterification monomer is obtained by esterification reaction of polyethylene glycol, p-toluenesulfonic acid and 3,7-dimethyl-6-octenoic acid to obtain a liquid B; mixing an oxidant and a fourth solvent to obtain a liquid C;

[0010] Step (3): mixing the liquid A, liquid B, and liquid C with the first solution for reaction, and then adjusting the pH value of the resulting reaction solution to 5 to 7 to obtain a low-sensitivity polycarboxylate water-reducing agent.

[0011] In a second aspect, the present invention provides a low-sensitivity polycarboxylate water-reducing agent prepared by the above preparation method.

[0012] In a third aspect, the present invention provides the use of the low-sensitivity polycarboxylate water-reducing agent in concrete.

[0013] Compared with the prior art, the present invention can at least achieve the following beneficial effects:

[0014] The low-sensitivity polycarboxylate water-reducing agent prepared by the preparation method of the present invention can effectively bond cement paste and aggregate during cement hydration, thereby ensuring the stability of different materials. The carboxylate structure contained in the agent will undergo a hydrolysis reaction under alkaline conditions in concrete, gradually generating new groups with a water-reducing effect, so that the fluidity of the concrete is maintained, thereby solving the problems of excessive concrete loss over time and water bleeding caused by the sensitivity of the admixtures caused by many problems in the current application of machine-made sand, such as poor particle grading, unstable performance of machine-made sand in different batches, high stone powder content, and high MB value. In addition, the low-sensitivity polycarboxylate water-reducing agent of the present invention has a high water reduction rate, can improve production capacity, and save energy consumption.

[0015] Other features and advantages of the present invention will be described in the following description, and some advantages may become apparent from the description, or may be understood by practicing the present invention. The purpose and other advantages of the present invention may be realized and obtained through the contents particularly pointed out in the description. DETAILED DESCRIPTION

[0016] The preparation method of the low-sensitivity polycarboxylate water-reducing agent provided by the present invention comprises:

[0017] Step (1): mixing a polyether macromonomer, a cross-linking monomer and a first solvent to obtain a first solution;

[0018] Step (2): mixing a reducing agent, a chain transfer agent and a second solvent to obtain a liquid A; mixing an unsaturated carboxylic acid monomer, an esterification monomer and a third solvent, wherein the esterification monomer is obtained by esterification reaction of polyethylene glycol, p-toluenesulfonic acid and 3,7-dimethyl-6-octenoic acid to obtain a liquid B; mixing an oxidant and a fourth solvent to obtain a liquid C;

[0019] Step (3): mixing the liquid A, liquid B, and liquid C with the first solution for reaction, and then adjusting the pH value of the resulting reaction solution to 5 to 7 to obtain a low-sensitivity polycarboxylate water-reducing agent.

[0020] In a preferred embodiment, the esterification reaction is carried out in the presence of a polymerization inhibitor and under the protection of an inert gas.

[0021] In the present invention, the function of the polymerization inhibitor is to prevent the single raw material from undergoing polymerization reaction. The present invention has no particular limitation on the selection of the polymerization inhibitor, as long as it can prevent the single raw material from undergoing polymerization reaction. The polymerization inhibitor is preferably a mixture of hydroquinone and phenothiazine.

[0022] In the present invention, preferably, the temperature of the esterification reaction is 100-130°C, such as 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C or any value therebetween. Preferably, the time of the esterification reaction is 4-7h, such as 7h, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C or any value therebetween.

[0023] In the present invention, preferably, in parts by weight, the amount of the polyethylene glycol is 250-270 parts by weight, for example, 250 parts by weight, 255 parts by weight, 260 parts by weight, 265 parts by weight, 270 parts by weight or any value therebetween; the amount of the p-toluenesulfonic acid is 8-15 parts by weight, for example, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight or any value therebetween; the amount of the 3,7-dimethyl-6-octenoic acid is 40-60 parts by weight, for example, 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 54 parts by weight, 56 parts by weight, 58 parts by weight, 60 parts by weight or any value therebetween; the amount of the hydroquinone is 0.3-0.6 parts by weight, for example, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight or any value therebetween; the amount of the phenothiazine is 0.04-0.07 parts by weight, for example, 0.04 parts by weight, 0.05 parts by weight, 0.06 parts by weight, 0.07 parts by weight or any value therebetween.

[0024] In a preferred embodiment, the preparation method of the esterification monomer comprises: adding 250-270 parts by weight of polyethylene glycol, 8-15 parts by weight of p-toluenesulfonic acid, 40-60 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.3-0.6 parts by weight of hydroquinone, and 0.04-0.07 parts by weight of phenothiazine into a reactor and mixing them; under nitrogen protection, adjusting the temperature to 100-130° C., and keeping the temperature for 4-7 hours to obtain the esterification monomer.

[0025] In the present invention, preferably, the cross-linking monomer is N-hydroxymethyl acrylamide, the polymer of which can produce a chemical reaction with cement hydration products to form an interpenetrating network structure, thereby improving the bonding between cement paste and aggregate.

[0026] In a preferred embodiment, the number average molecular weight of polyethylene glycol is 1100-1300.

[0027] The present invention has no particular limitation on the polyether macromonomer in step (1), which can be selected conventionally in the art. In order to further reduce the sensitivity of the polycarboxylate water-reducing agent to different machine-made sands, preferably, the polyether macromonomer is methyl allyl polyoxyethylene ether macromonomer.

[0028] In the present invention, preferably, in step (1), the weight ratio of the polyether macromonomer, the crosslinking monomer and the first solvent is 44-46: 0.2-0.7: 35-37. For example, in parts by weight, the amount of the polyether macromonomer can be 44-46 parts by weight, specifically 44 parts by weight, 45 parts by weight, 46 parts by weight or any value therebetween; the amount of the crosslinking monomer can be 0.2-0.7 parts by weight, specifically 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight or any value therebetween; the amount of the first solvent can be 35-37 parts by weight, specifically 35 parts by weight, 36 parts by weight, 37 parts by weight or any value therebetween.

[0029] The present invention has no particular limitation on the reducing agent in step (2), and it can be a conventional choice in the art. In order to further reduce the sensitivity of the polycarboxylate water-reducing agent to different machine-made sands, preferably, the reducing agent is a mixture of sodium bisulfite formaldehyde and sodium carbonate.

[0030] The present invention has no particular limitation on the chain transfer agent in step (2), and it can be a conventional choice in the art. In order to further reduce the sensitivity of the polycarboxylate water reducer to different machine-made sands, preferably, the chain transfer agent is at least one of mercaptopropionic acid, thioglycolic acid and mercaptoethanol.

[0031] In the present invention, preferably, in step (2), the weight ratio of the reducing agent, the chain transfer agent, and the second solvent is 0.04-0.08: 0.15-0.25: 4-5. For example, in parts by weight, the amount of the reducing agent is 0.04-0.08, specifically 0.04 parts by weight, 0.05 parts by weight, 0.06 parts by weight, 0.07 parts by weight, 0.08 parts by weight, or any value therebetween; the amount of the chain transfer agent is 0.15-0.25 parts by weight, specifically 0.15 parts by weight, 0.17 parts by weight, 0.20 parts by weight, 0.22 parts by weight, 0.25 parts by weight, or any value therebetween; the amount of the second solvent is 4-5 parts by weight, specifically 4 parts by weight, 4.2 parts by weight, 4.5 parts by weight, 4.7 parts by weight, 5 parts by weight, or any value therebetween.

[0032] The present invention has no particular limitation on the unsaturated carboxylic acid monomer in step (2), and it can be a conventional choice in the art. In order to further reduce the sensitivity of the polycarboxylic acid water-reducing agent to different machine-made sands, preferably, the unsaturated carboxylic acid monomer is acrylic acid.

[0033] In the present invention, preferably, in step (2), the weight ratio of the unsaturated carboxylic acid monomer, the esterification monomer and the third solvent is 5.5-6.5:0.5-1:1.5-2. For example, in parts by weight, the amount of the unsaturated carboxylic acid monomer is 5.5-6.5, specifically 5.5 parts by weight, 5.7 parts by weight, 6.0 parts by weight, 6.2 parts by weight, 6.5 parts by weight or any value therebetween; the amount of the esterification monomer is 0.5-1 parts by weight, specifically 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight or any value therebetween; the amount of the third solvent is 1.5-2 parts by weight, specifically 1.5 parts by weight, 1.7 parts by weight, 2 parts by weight or any value therebetween.

[0034] The present invention has no particular limitation on the oxidant in step (2), and it can be a conventional choice in the art. In order to further reduce the sensitivity of the polycarboxylate water-reducing agent to different machine-made sands, preferably, the oxidant is hydrogen peroxide.

[0035] In the present invention, preferably, the mass ratio of the oxidant to the fourth solvent is 0.30-0.40:2-3. For example, in parts by weight, the amount of the oxidant is 0.30-0.40, specifically 0.30 parts by weight, 0.31 parts by weight, 0.32 parts by weight, 0.33 parts by weight, 0.34 parts by weight, 0.35 parts by weight or any value therebetween; the amount of the fourth solvent is 2-3 parts by weight, specifically 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight, 3 parts by weight or any value therebetween.

[0036] In a preferred embodiment, in step (3), the liquid A, liquid B, liquid C and the first solution are mixed by simultaneously dropping the liquid A, liquid B and liquid C into the first solution.

[0037] In the present invention, preferably, the dropping time is 100-120 min, such as 100 min, 105 min, 110 min, 115 min, 120 min or any value therebetween.

[0038] In the present invention, preferably, the weight ratio of the liquid A, liquid B, liquid C and the first solution is 4.19-5.33: 7.50-9.50: 2.30-3.40: 79.2-83.7. For example, in parts by weight, the amount of liquid A is 4.19-5.33 parts by weight, specifically 4.19 parts by weight, 4.3 parts by weight, 4.5 parts by weight, 4.7 parts by weight, 5.0 parts by weight, 5.2 parts by weight, 5.33 parts by weight or any value therebetween; the amount of liquid B is 7.50-9.50 parts by weight, specifically 7.5 parts by weight, 7.7 parts by weight, 8.0 parts by weight, 8.2 parts by weight, 8.5 parts by weight, 8.7 parts by weight, 9.0 parts by weight, 9.3 parts by weight, 9.5 parts by weight or any value therebetween. any value; the amount of liquid C is 2.30-3.40 parts by weight, specifically 2.3 parts by weight, 2.5 parts by weight, 2.7 parts by weight, 3.0 parts by weight, 3.2 parts by weight, 3.4 parts by weight or any value therebetween; the amount of the first solution is 79.2-83.7 parts by weight, specifically 79.2 parts by weight, 79.6 parts by weight, 80 parts by weight, 80.5 parts by weight, 81 parts by weight, 81.5 parts by weight, 82 parts by weight, 82.5 parts by weight, 83 parts by weight, 83.7 parts by weight or any value therebetween.

[0039] In the present invention, preferably, in step (3), the pH value of the reaction solution is adjusted to 6.0.

[0040] In the present invention, preferably, the first solvent, the second solvent, the third solvent and the fourth solvent are all water.

[0041] In a preferred embodiment, in step (3), liquid A, liquid B and liquid C are simultaneously added dropwise into the first solution for 100-120 minutes, stirred for reaction, and after the reaction is completed, the pH value is adjusted to 6.0 to obtain a low-sensitivity polycarboxylate water-reducing agent.

[0042] In the second aspect, the present invention provides a low-sensitivity polycarboxylate water-reducing agent prepared by the above-mentioned preparation method. The low-sensitivity polycarboxylate water-reducing agent can solve the problems of excessive concrete loss over time and water seepage caused by the sensitivity of admixtures caused by many problems in the current application of machine-made sand, such as poor particle grading, unstable performance of machine-made sand in different batches, large stone powder content, and high MB value; and the low-sensitivity polycarboxylate water-reducing agent of the present invention has a high water reduction rate, can improve production capacity, and save energy consumption.

[0043] In a third aspect, the present invention provides the use of the low-sensitivity polycarboxylate water-reducing agent in concrete.

[0044] The present invention will be described in detail below through examples.

[0045] Example 1

[0046] This embodiment provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, comprising:

[0047] Step (1): 44 parts by weight of methyl allyl polyoxyethylene ether (purchased from Fujian Zhongshan Chemical Co., Ltd., brand HPEG2400), 0.2 parts by weight of N-hydroxymethyl acrylamide and 35 parts by weight of water are mixed and stirred to obtain a first solution.

[0048] Step (2): 0.04 parts by weight of a reducing agent (a mixture of sodium bisulfite formaldehyde and sodium carbonate in a mass ratio of 9:1), 0.15 parts by weight of mercaptopropionic acid and 4 parts by weight of water are mixed evenly to obtain liquid A. 5.5 parts by weight of acrylic acid, 1 part by weight of an esterification monomer and 1.5 parts by weight of water are mixed evenly to obtain liquid B. The preparation method of the esterification monomer is as follows: by weight, 260 parts by weight of polyethylene glycol (number average molecular weight of 1200), 10 parts by weight of p-toluenesulfonic acid, 50 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.4 parts by weight of hydroquinone and 0.05 parts by weight of phenothiazine are added to a reactor and mixed, and under nitrogen protection, the temperature is adjusted to 118° C. and kept warm for 5 hours to obtain an esterification monomer. 0.30 parts by weight of hydrogen peroxide and 2 parts by weight of water are mixed evenly to obtain liquid C.

[0049] Step (3): Add liquid A, liquid B and liquid C into the first solution simultaneously, the adding time is 110 minutes, and stir to react. After the reaction is completed, adjust the pH value and the amount of water to make the pH value 6.0, so as to obtain a low-sensitivity polycarboxylate water reducer LZ-KZJFJ1 with a mass concentration of 50%.

[0050] Example 2

[0051] This embodiment provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, comprising:

[0052] Step (1): 45 parts by weight of methyl allyl polyoxyethylene ether (purchased from Fujian Zhongshan Chemical Co., Ltd., brand HPEG2400), 0.5 parts by weight of N-hydroxymethyl acrylamide and 36 parts by weight of water are mixed and stirred to obtain a first solution.

[0053] Step (2): 0.06 parts by weight of a reducing agent (a mixture of sodium bisulfite formaldehyde and sodium carbonate in a mass ratio of 9:1), 0.20 parts by weight of thioglycolic acid, and 4.5 parts by weight of water are mixed evenly to obtain liquid A. 6.0 parts by weight of acrylic acid, 1 part by weight of an esterification monomer, and 2 parts by weight of water are mixed evenly to obtain liquid B. The preparation method of the esterification monomer is as follows: by weight, 250 parts by weight of polyethylene glycol (number average molecular weight of 1200), 8 parts by weight of p-toluenesulfonic acid, 60 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.3 parts by weight of hydroquinone, and 0.07 parts by weight of phenothiazine are added to a reactor and mixed, and the temperature is adjusted to 100° C. under nitrogen protection, and the temperature is kept for 7 hours to obtain an esterification monomer. 0.35 parts by weight of hydrogen peroxide and 2.5 parts by weight of water are mixed evenly to obtain liquid C.

[0054] Step (3): liquid A, liquid B and liquid C are simultaneously added dropwise into the first solution for 100 minutes, and the mixture is stirred for reaction. After the reaction is completed, the pH value and the amount of water are adjusted to a pH value of 6.0, thereby obtaining a low-sensitivity polycarboxylate water-reducing agent LZ-KZJFJ2 with a mass concentration of 50%.

[0055] Example 3

[0056] This embodiment provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, comprising:

[0057] Step (1): 46 parts by weight of methyl allyl polyoxyethylene ether (purchased from Fujian Zhongshan Chemical Co., Ltd., brand HPEG2400), 0.7 parts by weight of N-hydroxymethyl acrylamide and 37 parts by weight of water are mixed and stirred to obtain a first solution.

[0058] Step (2): 0.08 parts by weight of a reducing agent (a mixture of sodium bisulfite formaldehyde and sodium carbonate in a mass ratio of 9:1), 0.25 parts by weight of mercaptoethanol and 5 parts by weight of water are mixed evenly to obtain liquid A. 6.0 parts by weight of acrylic acid, 0.5 parts by weight of an esterification monomer and 2 parts by weight of water are mixed evenly to obtain liquid B. The preparation method of the esterification monomer is as follows: by weight, 270 parts by weight of polyethylene glycol (number average molecular weight of 1200), 15 parts by weight of p-toluenesulfonic acid, 40 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.6 parts by weight of hydroquinone and 0.04 parts by weight of phenothiazine are added to a reactor and mixed, and the temperature is adjusted to 130° C. under nitrogen protection, and the temperature is kept for 4 hours to obtain an esterification monomer. 0.35 parts by weight of hydrogen peroxide and 3 parts by weight of water are mixed evenly to obtain liquid C.

[0059] Step (3): Add liquid A, liquid B and liquid C into the first solution simultaneously, the dropping time is 120 minutes, and the reaction is stirred. After the reaction is completed, the pH value and the amount of water are adjusted to make the pH value 6.0, thereby obtaining a low-sensitivity polycarboxylate water reducer LZ-KZJFJ3 with a mass concentration of 50%.

[0060] Example 4

[0061] This embodiment provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, comprising:

[0062] Step (1): 45 parts by weight of methyl allyl polyoxyethylene ether (purchased from Fujian Zhongshan Chemical Co., Ltd., brand HPEG2400), 0.6 parts by weight of N-hydroxymethyl acrylamide, and 37 parts by weight of water are mixed and stirred to obtain a first solution.

[0063] Step (2): 0.06 parts by weight of a reducing agent (a mixture of sodium bisulfite formaldehyde and sodium carbonate in a mass ratio of 9:1), 0.25 parts by weight of thioglycolic acid and 5 parts by weight of water are mixed evenly to obtain liquid A. 6.5 parts by weight of acrylic acid, 0.5 parts by weight of an esterification monomer and 2 parts by weight of water are mixed evenly to obtain liquid B. The preparation method of the esterification monomer is as follows: by weight, 265 parts by weight of polyethylene glycol (number average molecular weight of 1200), 12 parts by weight of p-toluenesulfonic acid, 55 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.5 parts by weight of hydroquinone and 0.06 parts by weight of phenothiazine are added to a reactor and mixed, and the temperature is adjusted to 120° C. under nitrogen protection, and the temperature is kept for 5 hours to obtain an esterification monomer. 0.40 parts by weight of hydrogen peroxide and 3 parts by weight of water are mixed evenly to obtain liquid C.

[0064] Step (3): Add liquid A, liquid B, and liquid C into the first solution at the same time, the dropping time is 115 minutes, and the reaction is stirred. After the reaction is completed, the pH value and the amount of water are adjusted to make the pH value 6.0, and a low-sensitivity polycarboxylic acid water reducer LZ-KZJFJ4 with a mass concentration of 50% is obtained.

[0065] Example 5

[0066] This embodiment provides a method for preparing a low-sensitivity polycarboxylate water-reducing agent, comprising:

[0067] Step (1): 44 parts by weight of methyl allyl polyoxyethylene ether (purchased from Fujian Zhongshan Chemical Co., Ltd., brand HPEG2400), 0.7 parts by weight of N-hydroxymethyl acrylamide, and 37 parts by weight of water are mixed and stirred to obtain a first solution.

[0068] Step (2): 0.08 parts by weight of a reducing agent (a mixture of sodium bisulfite formaldehyde and sodium carbonate in a mass ratio of 9:1), 0.25 parts by weight of mercaptopropionic acid, and 5 parts by weight of water are mixed evenly to obtain liquid A. 6.5 parts by weight of acrylic acid, 1 part by weight of an esterification monomer, and 2 parts by weight of water are mixed evenly to obtain liquid B. The preparation method of the esterification monomer is as follows: by weight, 255 parts by weight of polyethylene glycol (number average molecular weight of 1200), 9 parts by weight of p-toluenesulfonic acid, 45 parts by weight of 3,7-dimethyl-6-octenoic acid, 0.5 parts by weight of hydroquinone, and 0.05 parts by weight of phenothiazine are added to a reactor and mixed, and the temperature is adjusted to 120° C. under nitrogen protection, and the temperature is kept for 5 hours to obtain an esterification monomer. 0.40 parts by weight of hydrogen peroxide and 3 parts by weight of water are mixed evenly to obtain liquid C.

[0069] Step (3): liquid A, liquid B and liquid C are simultaneously added dropwise into the first solution for 105 min, and stirred for reaction. After the reaction is completed, the pH value and the amount of water are adjusted to make the pH value 6.0, thereby obtaining a low-sensitivity polycarboxylate water reducer LZ-KZJFJ5 with a mass concentration of 50%.

[0070] Comparative Example 1

[0071] This embodiment provides a preparation method of a polycarboxylate water reducer similar to that of embodiment 4, except that no esterification monomer is added in step (3), and the remaining conditions are the same as those of embodiment 4, to obtain a low-sensitivity polycarboxylate water reducer LZ-DKZJFJ1.

[0072] Comparative Example 2

[0073] This embodiment provides a preparation method of a polycarboxylate water reducer similar to that of embodiment 3, except that N-hydroxymethyl acrylamide is not added in step (1), and the remaining conditions are the same as those of embodiment 3, to obtain a low-sensitivity polycarboxylate water reducer LZ-DKZJFJ2.

[0074] Comparative Example 3

[0075] This embodiment provides a preparation method of a polycarboxylate water reducer similar to that of Embodiment 1, except that, when preparing the esterification monomer, p-toluenesulfonic acid of the same mass is used instead of 3,7-dimethyl-6-octenoic acid, that is, 3,7-dimethyl-6-octenoic acid is not added, and the remaining conditions are the same as those of Embodiment 1, to obtain a low-sensitivity polycarboxylate water reducer LZ-DKZJFJ3.

[0076] Comparative Example 4

[0077] This embodiment provides a preparation method of a polycarboxylate water reducer similar to that of Embodiment 1, except that, when preparing the esterification monomer, 3,7-dimethyl-6-octenoic acid of the same mass is used instead of p-toluenesulfonic acid, that is, p-toluenesulfonic acid is not added, and the remaining conditions are the same as those of Embodiment 1, to obtain a low-sensitivity polycarboxylate water reducer LZ-DKZJFJ4.

[0078] Comparative Example 5

[0079] This embodiment provides a preparation method of a polycarboxylate water reducer similar to that of Embodiment 1, except that the same mass of polypropylene glycol (number average molecular weight of 1200) is used instead of polyethylene glycol, and the other conditions are the same as those of Embodiment 1 to obtain a low-sensitivity polycarboxylate water reducer LZ-DKZJFJ5.

[0080] Comparative Example 6

[0081] A commercially available low-sensitivity polycarboxylate water-reducing agent mother liquor was used, with a mass concentration of 50%, purchased from Jiangsu Subote New Materials Co., Ltd., with a brand name of PCA-9.

[0082] Test Case

[0083] Test standard: Concrete performance test: According to GB8076-2008 standard, the water reducers of Examples 1-5 and Comparative Examples 1-6 and Point-T of Kezhijie are compounded into 10% samples according to the solid content of 5:5; Chunchi P.O42.5 ordinary Portland cement is used, and the dosage of polycarboxylate water reducer is 1.5% (relative to the amount of cementitious material); the concrete mix ratio is: cement 360kg / m 3 、Machinery sand 725kg / m 3 、Small stones 650kg / m 3 , large stones 425kg / m 3 , water 170kg / m 3 According to the above admixture formula, the performance tests of the water reducers of Examples 1-5 and Comparative Examples 1-6 were carried out respectively, and the initial, 1h and 2h concrete slump and expansion were tested respectively. The machine-made sand was collected from concrete companies in different regions of Fujian, as shown in Table 1 for details, and the concrete test results are shown in Tables 2-4 for details.

[0084] Table 1 Physical properties of machine-made sand from concrete companies in different regions of Fujian

[0085] Sample source area Fineness modulus Grading interval MB Value Stone powder content / % Crushing value / % Nan'an Shuitou Kanglong Concrete Co., Ltd. Quanzhou 3.1 Zone 2 0.5 4.6 29 Xiamen Jimei District Hongming Building Materials Co., Ltd. Xiamen 2.6 Zone 2 1.3 5.5 25 Zhangzhou Longcheng Concrete Co., Ltd. Zhangzhou 3.3 Zone 1 3.3 4.3 27

[0086] Table 2 Test results of Kanglong machine-made sand mixed concrete

[0087]

[0088] Table 3 Test results of Hongming machine-made sand concrete

[0089]

[0090] Table 4 Test results of Longcheng machine-made sand concrete

[0091]

[0092]

[0093] It can be seen from Tables 1-4 that, compared with Comparative Examples 2 and 6, Examples 1-5 have better workability under different machine-made sand performance conditions; compared with Comparative Examples 1-6, Examples 1-5 have better initial and 1h and 2h loss performance of concrete slump and expansion. Therefore, the low-sensitivity polycarboxylate water-reducing agent prepared by the present invention has better workability and higher water reduction rate.

[0094] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for preparing a low-sensitivity polycarboxylate water-reducing agent, characterized in that: The preparation method comprises: Step (1): mixing a polyether macromonomer, a cross-linking monomer and a first solvent to obtain a first solution; Step (2): mixing a reducing agent, a chain transfer agent and a second solvent to obtain a liquid A; mixing an unsaturated carboxylic acid monomer, an esterification monomer and a third solvent, wherein the esterification monomer is obtained by esterification reaction of polyethylene glycol, p-toluenesulfonic acid and 3,7-dimethyl-6-octenoic acid to obtain a liquid B; mixing an oxidant and a fourth solvent to obtain a liquid C; Step (3): mixing the liquid A, liquid B, and liquid C with the first solution for reaction, and then adjusting the pH value of the resulting reaction solution to 5 to 7 to obtain a low-sensitivity polycarboxylate water-reducing agent.

2. The preparation method according to claim 1, characterized in that: The esterification reaction is carried out in the presence of an inhibitor and under the protection of an inert gas; Preferably, the polymerization inhibitor is a mixture of hydroquinone and phenothiazine; Preferably, the esterification reaction temperature is 100-130° C. and the time is 4-7 hours.

3. The preparation method according to claim 2, characterized in that: In parts by weight, the amount of the polyethylene glycol is 250-270 parts by weight, the amount of the p-toluenesulfonic acid is 8-15 parts by weight, the amount of the 3,7-dimethyl-6-octenoic acid is 40-60 parts by weight, the amount of the hydroquinone is 0.3-0.6 parts by weight, and the amount of the phenothiazine is 0.04-0.07 parts by weight.

4. The preparation method according to claim 1, characterized in that: The cross-linking monomer is N-methylol acrylamide.

5. The preparation method according to claim 1, characterized in that: In step (1), the weight ratio of the polyether macromonomer, the cross-linking monomer and the first solvent is 44-46:0.2-0.7:35-37.

6. The preparation method according to claim 1, characterized in that: In step (2), the weight ratio of the reducing agent, the chain transfer agent, and the second solvent is 0.04-0.08:0.15-0.25:4-5; Preferably, the weight ratio of the unsaturated carboxylic acid monomer, the esterification monomer and the third solvent is 5.5-6.5:0.5-1:1.5-2; Preferably, the mass ratio of the oxidant to the fourth solvent is 0.30-0.40:2-3.

7. The preparation method according to claim 1, characterized in that: In step (3), the liquid A, liquid B, liquid C and the first solution are mixed by simultaneously dropping the liquid A, liquid B and liquid C into the first solution; Preferably, the dropping time is 100-120min; Preferably, the weight ratio of the A solution, the B solution, the C solution and the first solution is 4.19-5.33:7.50-9.50:2.30-3.40:79.2-83.

7.

8. The preparation method according to claim 1, characterized in that: In step (3), the pH value of the reaction solution is adjusted to 6.

0.

9. A low-sensitivity polycarboxylate water-reducing agent prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the low-sensitivity polycarboxylate water-reducing agent according to claim 9 in concrete.

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