A preparation method of sulfamic acid water reducer

Abstract

The present invention belongs to the technical field of cement admixtures, and specifically relates to a method for preparing an aminosulfonic acid-based water reducer. The present invention introduces amide-modified sodium ligninsulfonate and nano-silica into the water reducer. The resulting aminosulfonic acid-based water reducer has a hydrophobic backbone containing groups such as phenyl, and is connected to multiple hydrophilic groups such as -SO3Na, -OH, -NH2, and -CONH. The synergistic effect of these groups gives the water reducer excellent water retention, effectively reducing bleeding in concrete and improving concrete durability.

Description

Technical Field

[0001] The invention belongs to the technical field of cement admixtures, and particularly relates to a preparation method of a sulfamic acid-based water reducer. Background Art

[0002] A water reducer is a concrete admixture that reduces mixing water consumption while maintaining the concrete's slump. Water reducers, typically surfactants, primarily work by reducing the attraction between cement particles through polar adsorption and polar repulsion, thereby dispersing the cement molecules. When added to concrete, water reducers improve its frost resistance, corrosion resistance, water seepage, impermeability, and mechanical strength.

[0003] Water reducers primarily include naphthalene-based, melamine-based, aminosulfonic acid-based, and polycarboxylic acid-based water reducers. While naphthalene-based and melamine-based water reducers are mature technologies, they exhibit numerous limitations in the formulation of high-performance concrete due to their low water reduction rates and poor compatibility with cement. Polycarboxylic acid-based water reducers are also incompatible with many admixture components, significantly limiting their application. However, aminosulfonic acid-based water reducers, with their high water reduction rates and low dosage, have become a research hotspot in recent years.

[0004] A Chinese patent application, publication number CN107777906A, discloses a method for preparing a sulfamic acid-based water reducer. This method utilizes industrial phenol-containing wastewater to prepare a sulfamic acid-based water reducer using crude phenol prepared from the wastewater, sodium hydroxide, caustic soda flakes, and a FePO4 solid acid catalyst. This method shortens reaction time and improves raw material conversion. However, the hydrophobic groups in sulfamic acid-based water reducers are short and highly polar. While they effectively disperse cement particles, they struggle to form a dense, stable, and thick adsorption layer to prevent water migration, resulting in relatively poor water retention when applied to concrete. Consequently, sulfamic acid-based high-efficiency water reducers are sensitive to dosage in actual use. High dosages can lead to severe water exudation and segregation, impacting construction quality. Summary of the Invention

[0005] Existing aminosulfonic acid-based water reducers have the problem of water exudation and segregation. In order to solve this problem, the present invention provides a method for preparing an aminosulfonic acid-based water reducer.

[0006] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a sulfamic acid-based water reducer, comprising the following steps:

[0008] S1: 4-(methylsulfonyl)phenol, phenol, sodium p-aminobenzenesulfonate and water are mixed evenly, the pH is adjusted to 9-11, the temperature is raised once, an aldehyde aqueous solution is added dropwise, the temperature is raised a second time for reaction, and the mixture is dried to obtain the first substance;

[0009] S2: uniformly mixing the amide-modified sodium lignin sulfonate, the first substance, and water, adjusting the pH to 9-11, reacting, and drying to obtain the second substance;

[0010] S3: Evenly mix the second substance and water, and dropwise add the nano-silica suspension to react to obtain an aminosulfonic acid-based water reducer.

[0011] By adopting the above technical solution, the present invention introduces amide-modified sodium lignin sulfonate and nano-silica into the water reducer, and the prepared aminosulfonic acid-based water reducer has a hydrophobic main chain containing groups such as phenyl, and is connected with multiple hydrophilic groups such as -SO3Na, -OH, -NH2 and -CONH, so that the aminosulfonic acid-based water reducer has good water retention and water reduction rate.

[0012] Preferably, in step S1, the molar ratio of 4-(methylsulfonyl)phenol, phenol and sodium p-aminobenzenesulfonate is (1-1.2):(0.8-1):1.

[0013] By adopting the above technical solution, the sulfamic acid-based water-reducing agent prepared by using 4-(methylsulfonyl)phenol and phenol within the dosage range has moderate dispersibility in cement; when the dosage of phenolic substances is small, the number of groups such as benzene rings in the generated sulfamic acid-based water-reducing agent molecules is reduced, the steric hindrance between molecules is reduced, and the dispersibility of cement is weakened; when the dosage of phenolic substances is large, excessive polymerization is easily generated, which increases the molecular weight of the sulfamic acid-based water-reducing agent and also affects the dispersibility of cement.

[0014] Preferably, in step S1, the aldehyde aqueous solution is prepared by mixing formaldehyde, 1,8-diadehydanthracene and water in a ratio of 1 mol: (0.8-1) mol: (400-500) mL; the molar ratio of formaldehyde to sodium p-aminobenzenesulfonate is (0.6-0.7):1.

[0015] By adopting the above technical solution, 1,8-dialdehyde anthracene is used to replace part of the formaldehyde, and the hydrophobic conjugated large π bond in the 1,8-dialdehyde anthracene is introduced into the water reducer; within this range, the ratio of hydrophobic groups to hydrophilic groups is moderate, so that the aminosulfonic acid-based water reducer can form a stable adsorption layer on the surface of cement particles, thereby improving water retention.

[0016] Preferably, in step S1, the temperature of the first heating is 65-75° C., and the time of the dropwise addition is 1-3 h; the temperature of the second heating reaction is 85-95° C., and the time of the second heating reaction is 4-6 h.

[0017] By adopting the above technical solution, within the reaction temperature and time, while ensuring the reaction efficiency, a sulfamic acid-based water reducer with good performance can be obtained.

[0018] Preferably, in step S2, the amount of amide-modified sodium lignin sulfonate used is 10%-15% of the mass of the first substance; the reaction temperature is 90-95° C., and the reaction time is 1-3 hours.

[0019] By adopting the above technical solution, the amount of amide-modified sodium lignin sulfonate is within this range, which can better balance the various properties of the aminosulfonic acid-based water reducer on cement particles, such as dispersibility and water retention. If the amount of amide-modified sodium lignin sulfonate is too small, it is easy to cause the dispersibility of cement particles to decrease; if the amount is too large, it is easy to cause the molecular structure of the aminosulfonic acid-based water reducer to be too complex, the interaction between molecules is enhanced, and the dispersibility of the water reducer on cement particles is deteriorated.

[0020] Preferably, in step S2, the preparation method of amide-modified sodium lignin sulfonate comprises the following steps:

[0021] (1) Mix sodium lignin sulfonate, hydrogen peroxide and water evenly, adjust the pH to 3-4, heat the reaction, centrifuge, immerse, precipitate, wash and dry to obtain oxidized sodium lignin sulfonate;

[0022] (2) Under a nitrogen atmosphere, oxidized sodium lignin sulfonate, sodium persulfate and water are mixed evenly, heated once, and an aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid is added dropwise, heated twice for reaction, impregnated, precipitated, washed and dried to obtain amide-modified sodium lignin sulfonate.

[0023] By adopting the above technical solution, the reactive sites of the oxidized sodium lignin sulfonate are increased, and a better polymerization reaction can be carried out with 2-acrylamido-2-methylpropane sulfonic acid, thereby improving the performance of the water reducer.

[0024] Preferably, in step (1), the mass ratio of sodium lignin sulfonate to hydrogen peroxide is 1:(0.1-0.15); the temperature of the temperature-raising reaction is 65-75° C., and the time of the temperature-raising reaction is 4-5 hours.

[0025] By adopting the above technical solution, the sodium lignin sulfonate can be moderately oxidized under the ratio and reaction conditions without excessively destroying the structure of the sodium lignin sulfonate.

[0026] Preferably, in step (2), the mass ratio of sodium oxidized lignin sulfonate, sodium persulfate and 2-acrylamido-2-methylpropanesulfonic acid is 1:(0.02-0.05):(0.3-0.7); the mass fraction of the 2-acrylamido-2-methylpropanesulfonic acid aqueous solution is 20%-25%; the temperature of the first heating is 60-65°C; the time of the dropwise addition is 2-2.5 hours; the temperature of the second heating reaction is 70-80°C, and the time of the second heating reaction is 3-4 hours.

[0027] By adopting the above technical solution, after sodium lignin sulfonate is modified by 2-acrylamido-2-methylpropane sulfonic acid, the molecular structure of sodium lignin sulfonate is optimized, the binding ability of sodium lignin sulfonate with water molecules is increased, the free movement of water is reduced, and the water retention of concrete is improved; the introduction of sulfonic acid groups and amide groups can improve the adsorption effect of the water reducer on the surface of cement particles, making the adsorption of sodium lignin sulfonate on the surface of cement particles more uniform and stable, effectively preventing the agglomeration of cement particles, improving the fluidity of concrete, and reducing the slump loss of concrete.

[0028] Preferably, in step S3, the mass ratio of nano-silicon dioxide to the second substance is (0.05-0.1):1; and the mass fraction of the nano-silicon dioxide suspension is 15%-20%.

[0029] By adopting the above technical solution, the presence of nano-silica can optimize the steric hindrance effect of aminosulfonic acid-based water-reducing agent molecules, adjust the adsorption state of aminosulfonic acid-based water-reducing agent on the surface of cement particles, and optimize the dispersion effect.

[0030] Preferably, in step S3, the reaction temperature is 60-65° C., and the reaction time is 3-4 h.

[0031] In summary, the beneficial effects of the present invention are:

[0032] (1) The present invention introduces amide-modified sodium lignin sulfonate and nano-silica into the water reducer. The hydrophobic main chain of the prepared aminosulfonic acid-based water reducer contains groups such as phenyl, and is connected with multiple hydrophilic groups such as -SO3Na, -OH, -NH2 and -CONH. The synergistic effect of multiple groups makes the water reducer have good water retention performance, which can effectively reduce the bleeding phenomenon in concrete and improve the durability of concrete.

[0033] (2) The present invention utilizes 4-(methylsulfonyl)phenol to replace part of phenol and 1,8-dialdehyde anthracene to replace part of formaldehyde, and introduces appropriate hydrophobic groups and hydrophilic groups into the water reducer molecular chain, so that the water reducer can form a stable adsorption layer on the surface of cement particles, thereby improving water retention;

[0034] (3) The present invention utilizes 2-acrylamido-2-methylpropanesulfonic acid to modify sodium lignin sulfonate. The introduction of sulfonic acid groups in the 2-acrylamido-2-methylpropanesulfonic acid molecules increases the binding ability of sodium lignin sulfonate with water molecules, enabling it to adsorb more water molecules and reduce the free movement of water, thereby improving the water retention of concrete and avoiding the occurrence of water bleeding and segregation in concrete.

[0035] (4) The present invention introduces nano-silica into the water reducer to increase the electrostatic repulsion and steric hindrance effect between cement particles, thereby improving the water reduction rate; the silanol groups on its surface can react with calcium ions and the like in the cement particles, making the cement particles more evenly dispersed in the slurry, effectively preventing the agglomeration of cement particles and improving fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the infrared spectrum of the aminosulfonic acid-based water reducer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is explained in detail below with reference to several representative embodiments of the present invention.

[0038] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are all conventional methods. Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples are all commercially available.

[0039] Example 1

[0040] The preparation method of a sulfamic acid-based water reducer of this embodiment comprises the following specific steps:

[0041] S1: 17.22 g of 4-(methylsulfonyl)phenol, 8.47 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 11, the temperature was raised to 70°C once, and an aldehyde aqueous solution was added dropwise for 3 h. The temperature was raised to 95°C for a second time to react for 5 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 1.8 g of formaldehyde, 12.65 g of 1,8-dialdehyde anthracene and 28.8 mL of water for 15 min.

[0042] S2: 2.6 g of amide-modified sodium lignin sulfonate, 20 g of the first substance, and 80 mL of water were added to a three-necked flask and stirred for 30 min. The pH was adjusted to 10, the temperature was raised to 92°C, and the reaction was carried out for 2 h. The second substance was obtained by spray drying.

[0043] S3: 30g of the second substance and 75mL of water were added to a three-necked flask and stirred for 30min. 20g of a 15% nano-silica suspension was added dropwise. The temperature was raised to 60℃ and the reaction was carried out for 3h to obtain an aminosulfonic acid water reducer. The infrared spectrum of the aminosulfonic acid water reducer is shown in FIG. Figure 1 .

[0044] In the infrared spectrum of aminosulfonic acid water reducer, 3435cm -1 The peaks at 2926cm are the superposition of stretching vibration peaks of amino, amide and hydroxyl groups; -1 The C—H stretching vibration absorption peak is at 1676 cm -1 The stretching vibration absorption peak of C=O is at 1600cm -1 、1516cm -1 and 1465cm -1 The peaks near it are the stretching vibration absorption peaks of the carbon-carbon double bond of the benzene ring conjugated system; 1448 cm -1 The absorption peak of NH is at 1338 cm -1 and 1120cm -1 is the stretching vibration absorption peak of sulfonic acid group, 1042cm -1 The stretching vibration absorption peak of COC is at 806 cm -1 is the Si-O-Si stretching vibration absorption peak; in summary, the above infrared spectrum contains absorption peaks of groups such as benzene ring, amino group, hydroxyl group, amide group, sulfonic acid group, ether bond and silicon-oxygen bond, which proves that the aminosulfonic acid water reducer is successfully synthesized.

[0045] The preparation method of the amide-modified sodium lignin sulfonate of this embodiment comprises the following specific steps:

[0046] (1) Add 53.45 g of sodium lignin sulfonate, 8 g of hydrogen peroxide and 100 mL of water into a three-necked flask and stir for 20 min. Adjust the pH to 3, heat to 65 °C and react for 4 h. Centrifuge, soak in anhydrous ethanol, precipitate, wash with water, and dry in a vacuum drying oven at 50 °C for 8 h to obtain oxidized sodium lignin sulfonate.

[0047] (2) Under nitrogen atmosphere, 50 g of oxidized sodium lignin sulfonate, 1 g of sodium persulfate and 100 mL of water were added to a three-necked flask and stirred for 20 min. The temperature was raised to 65 °C once, and 140 g of a 25% mass fraction 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was added dropwise for 2.5 h. The temperature was raised to 70 °C for the second time and reacted for 4 h. The mixture was immersed in anhydrous ethanol, precipitated, washed with water, and dried in a vacuum drying oven at 50 °C for 12 h to obtain amide-modified sodium lignin sulfonate.

[0048] Example 2

[0049] The preparation method of a sulfamic acid-based water reducer of this embodiment comprises the following specific steps:

[0050] S1: 18.94 g of 4-(methylsulfonyl)phenol, 9.4 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 9, the temperature was raised to 65°C once, and an aldehyde aqueous solution was added dropwise for 1 h. The temperature was raised to 85°C for a second time to react for 5 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 2.1 g of formaldehyde, 13.12 g of 1,8-dialdehyde anthracene and 28 mL of water for 15 min.

[0051] S2: 3 g of amide-modified sodium lignin sulfonate, 20 g of the first substance, and 80 mL of water were added to a three-necked flask and stirred for 30 min. The pH was adjusted to 11, the temperature was raised to 90°C, the reaction was carried out for 2 h, and the second substance was obtained by spray drying.

[0052] S3: Add 30 g of the second substance and 75 mL of water into a three-necked flask and stir for 30 min. Add 7.5 g of a 20% nano-silica suspension dropwise, heat to 65 °C and react for 4 h to obtain an aminosulfonic acid-based water reducer.

[0053] The preparation method of the amide-modified sodium lignin sulfonate of this embodiment comprises the following specific steps:

[0054] (1) Add 53.45 g of sodium lignin sulfonate, 5.35 g of hydrogen peroxide and 100 mL of water into a three-necked flask and stir for 20 min. Adjust the pH to 3, heat to 75 °C and react for 5 h. Centrifuge, soak in anhydrous ethanol, precipitate, wash with water, and dry in a vacuum drying oven at 50 °C for 8 h to obtain oxidized sodium lignin sulfonate.

[0055] (2) Under nitrogen atmosphere, 50 g of oxidized sodium lignin sulfonate, 2.5 g of sodium persulfate and 100 mL of water were added to a three-necked flask and stirred for 20 min. The temperature was raised to 60 °C once, and 125 g of a 20% 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was added dropwise for 2 h. The temperature was raised to 75 °C for the second time and reacted for 3 h. The mixture was immersed in anhydrous ethanol, precipitated, washed with water, and dried in a vacuum drying oven at 50 °C for 12 h to obtain amide-modified sodium lignin sulfonate.

[0056] Example 3

[0057] The preparation method of a sulfamic acid-based water reducer of this embodiment comprises the following specific steps:

[0058] S1: 20.65 g of 4-(methylsulfonyl)phenol, 7.53 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 10, the temperature was raised to 75°C once, and an aldehyde aqueous solution was added dropwise for 3 h. The temperature was raised to 90°C for a second time to react for 4 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 1.95 g of formaldehyde, 15.23 g of 1,8-dialdehyde anthracene and 32.5 mL of water for 15 min;

[0059] S2: 2.4 g of amide-modified sodium lignin sulfonate, 20 g of the first substance, and 80 mL of water were added to a three-necked flask and stirred for 30 min. The pH was adjusted to 9, the temperature was raised to 95°C, the reaction was carried out for 1 h, and the second substance was obtained by spray drying.

[0060] S3: Add 30 g of the second substance and 75 mL of water into a three-necked flask and stir for 30 min. Add 10.5 g of a 17% nano-silica suspension dropwise, heat to 60 °C and react for 4 h to obtain an aminosulfonic acid-based water reducer.

[0061] The preparation method of the amide-modified sodium lignin sulfonate of this embodiment comprises the following specific steps:

[0062] (1) Add 53.45 g of sodium lignin sulfonate, 6.4 g of hydrogen peroxide and 100 mL of water into a three-necked flask and stir for 20 min. Adjust the pH to 4, heat to 70 °C and react for 4 h. Centrifuge, soak in anhydrous ethanol, precipitate, wash with water, and dry in a vacuum drying oven at 50 °C for 8 h to obtain oxidized sodium lignin sulfonate.

[0063] (2) Under nitrogen atmosphere, 50 g of oxidized sodium lignin sulfonate, 1.5 g of sodium persulfate and 100 mL of water were added to a three-necked flask and stirred for 20 min. The temperature was raised to 60 °C once, and 68 g of 22% 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was added dropwise for 2.5 h. The temperature was raised to 80 °C for the second time and reacted for 4 h. The mixture was immersed in anhydrous ethanol, precipitated, washed with water, and dried in a vacuum drying oven at 50 °C for 12 h to obtain amide-modified sodium lignin sulfonate.

[0064] Example 4

[0065] The preparation method of a sulfamic acid-based water reducer of this embodiment comprises the following specific steps:

[0066] S1: 17.22 g of 4-(methylsulfonyl)phenol, 9.4 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 11, the temperature was raised to 70°C once, and an aldehyde aqueous solution was added dropwise for 2 h. The temperature was raised to 90°C for a second time to react for 6 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 2.1 g of formaldehyde, 14.76 g of 1,8-dialdehyde anthracene and 31.5 mL of water for 15 min.

[0067] S2: 2 g of amide-modified sodium lignin sulfonate, 20 g of the first substance, and 80 mL of water were added to a three-necked flask and stirred for 30 min. The pH was adjusted to 9, the temperature was raised to 95°C, and the reaction was carried out for 3 h. The second substance was obtained by spray drying.

[0068] S3: Add 30 g of the second substance and 75 mL of water into a three-necked flask and stir for 30 min. Add 16 g of a 15% nano-silica suspension dropwise, heat to 63 °C and react for 3 h to obtain an aminosulfonic acid-based water reducer.

[0069] The preparation method of the amide-modified sodium lignin sulfonate of this embodiment comprises the following specific steps:

[0070] (1) Add 53.45 g of sodium lignin sulfonate, 6.95 g of hydrogen peroxide and 100 mL of water into a three-necked flask and stir for 20 min. Adjust the pH to 4, heat to 68 °C and react for 5 h. Centrifuge, soak in anhydrous ethanol, precipitate, wash with water, and dry in a vacuum drying oven at 50 °C for 8 h to obtain oxidized sodium lignin sulfonate.

[0071] (2) Under nitrogen atmosphere, 50 g of oxidized sodium lignin sulfonate, 1 g of sodium persulfate and 100 mL of water were added to a three-necked flask and stirred for 20 min. The temperature was raised to 65 °C once, and 113 g of 22% 2-acrylamido-2-methylpropanesulfonic acid aqueous solution was added dropwise for 2 h. The temperature was raised to 75 °C for the second time and reacted for 3 h. The mixture was immersed in anhydrous ethanol, precipitated, washed with water, and dried in a vacuum drying oven at 50 °C for 12 h to obtain amide-modified sodium lignin sulfonate.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that in step S1 of this comparative example, 4-(methylsulfonyl)phenol is replaced by phenol in an equal molar amount, and the rest are the same as in Example 1.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that in step S1 of this comparative example, an equimolar amount of formaldehyde is used instead of 1,8-dialdehyde anthracene, and the rest is the same as in Example 1.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that in step S2 of this comparative example, the amount of amide-modified sodium lignin sulfonate used accounts for 55% of the mass of the first substance, and the rest is the same as Example 1.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that in the preparation method of amide-modified sodium lignin sulfonate in this comparative example, the mass ratio of oxidized sodium lignin sulfonate to 2-acrylamido-2-methylpropanesulfonic acid is 1:2, and the rest is the same as Example 1.

[0080] Comparative Example 5

[0081] The difference from Example 1 is that the preparation of step S2 in Example 1 is not performed in this comparative example, and the rest is the same as in Example 1; the preparation method of the aminosulfonic acid-based water reducer in this comparative example has the following specific steps:

[0082] S1: 17.22 g of 4-(methylsulfonyl)phenol, 8.47 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 11, the temperature was raised to 70°C once, and an aldehyde aqueous solution was added dropwise for 3 h. The temperature was raised to 95°C for a second time to react for 5 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 1.8 g of formaldehyde, 12.65 g of 1,8-dialdehyde anthracene and 28.8 mL of water for 15 min.

[0083] S2: Add 30 g of the first substance and 75 mL of water into a three-necked flask and stir for 30 min. Add 20 g of a 15% nano-silica suspension dropwise, heat to 60°C and react for 3 h to obtain an aminosulfonic acid-based water reducer.

[0084] Comparative Example 6

[0085] The difference from Example 1 is that in step S3 of this comparative example, the mass ratio of nano-silicon dioxide to the second substance is 0.5:1, and the rest is the same as Example 1.

[0086] Comparative Example 7

[0087] The difference from Example 1 is that the preparation of step S3 in Example 1 is not performed in this comparative example, and the rest is the same as in Example 1; the preparation method of the aminosulfonic acid-based water reducer in this comparative example has the following specific steps:

[0088] S1: 17.22 g of 4-(methylsulfonyl)phenol, 8.47 g of phenol, 19.52 g of sodium p-aminobenzenesulfonate and 300 mL of water were added to a three-necked flask and stirred for 20 min. The pH was adjusted to 11, the temperature was raised to 70°C once, and an aldehyde aqueous solution was added dropwise for 3 h. The temperature was raised to 95°C for a second time to react for 5 h, and spray-dried to obtain the first substance; the aldehyde aqueous solution was prepared by stirring 1.8 g of formaldehyde, 12.65 g of 1,8-dialdehyde anthracene and 28.8 mL of water for 15 min.

[0089] S2: 2.6 g of amide-modified sodium lignin sulfonate, 20 g of the first substance, and 80 mL of water were added to a three-necked flask and stirred for 30 min. The pH was adjusted to 10, and the temperature was raised to 92° C. and reacted for 2 h to obtain an aminosulfonic acid-based water reducer.

[0090] Comparative Example 8

[0091] The preparation method of the aminosulfonic acid water-reducing agent of this comparative example comprises the following specific steps:

[0092] Add 17.88g of phenol, 19.52g of sodium p-aminobenzenesulfonate and 300mL of water to a three-necked flask and stir for 20min. Adjust the pH to 11, heat it to 70℃ once, add aldehyde aqueous solution dropwise for 3h, heat it to 95℃ for the second time and react for 5h to obtain aminosulfonic acid-based water reducer; the aldehyde aqueous solution is prepared by stirring 3.42g of formaldehyde with 28.8mL of water for 15min.

[0093] Related performance tests

[0094] The aminosulfonic acid-based water reducers prepared in Examples 1 to 4 and Comparative Examples 1 to 8 were subjected to relevant performance tests. The test results are shown in Tables 1 and 2.

[0095] Cement paste fluidity: Tested in accordance with GB / T 8077-2000 "Test method for homogeneity of concrete admixtures".

[0096] Concrete application performance test: Cement: P.O42.5 cement is used; Sand: medium sand with a fineness modulus of 2.6; Stone: crushed stone particle size 5-40mm (secondary mixing, 5-20mm small stones account for 40%, 21-40mm large stones account for 60%); Concrete mix ratio: 3.3kg cement, 7.1kg sand, 7.05kg large stone, 4.6kg small stone, adjust the amount of water reducer to maintain the slump of concrete at 7-9cm; test in accordance with GB / T8076-2008 "Concrete Admixtures".

[0097] Table 1 Cement paste fluidity

[0098]

[0099] Table 2 Concrete properties

[0100]

[0101] From the comparison of Comparative Example 1 and Comparative Example 2 with Example 1, it can be seen that the introduction of 4-(methylsulfonyl)phenol and 1,8-dialdehyde anthracene can balance the hydrophilic and hydrophobic groups in the aminosulfonic acid-based water reducer molecules and improve the water retention of the aminosulfonic acid-based water reducer.

[0102] By comparing Comparative Examples 3 and 5 with Example 1, it can be seen that the introduction of amide-modified sodium lignin sulfonate can improve the water retention and other properties of concrete, but excessive use can easily make the molecular structure of the aminosulfonic acid water reducer disordered, destroy the molecular structure, and lead to a decrease in the performance of the aminosulfonic acid water reducer.

[0103] Comparison of Comparative Example 4 with Example 1 shows that an excessive amount of 2-acrylamido-2-methylpropanesulfonic acid may lead to excessive branching or cross-linking of the molecular chain, making the adsorption morphology of the water-reducing agent molecules on the surface of cement particles complex and unstable, and failing to form a tightly ordered adsorption layer, thereby reducing the water reduction rate and overall water retention of the concrete.

[0104] By comparing Comparative Examples 6 and 7 with Example 1, it can be seen that nano-silica has a high specific surface area and surface activity, can be adsorbed on the surface of cement particles, and enhance the dispersing effect of the water reducer on the cement particles; however, when the nano-silica content is too high, it is easy to form cross-linked polymers, which is not conducive to dispersion; the introduction of nano-silica can fill the pores and microcracks in the concrete, make the internal structure of the concrete more dense, reduce the porosity, reduce the water bleeding phenomenon of the concrete, and improve the compressive strength of the concrete.

[0105] From the comparison between Comparative Example 8 and Example 1, it can be seen that the concrete prepared with the aminosulfonic acid-based water-reducing agent prepared by the present invention has good water retention, water reduction rate and other properties.

[0106] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a sulfamic acid-based water reducer, characterized in that: The steps include: S1: 4-(methylsulfonyl)phenol, phenol, sodium p-aminobenzenesulfonate and water are mixed evenly, the pH is adjusted to 9-11, the temperature is raised once, an aldehyde aqueous solution is added dropwise, the temperature is raised a second time for reaction, and the mixture is dried to obtain the first substance; S2: uniformly mixing the amide-modified sodium lignin sulfonate, the first substance, and water, adjusting the pH to 9-11, reacting, and drying to obtain the second substance; S3: Evenly mix the second substance with water, and dropwise add the nano-silica suspension to react to obtain an aminosulfonic acid-based water reducer; In step S1, the molar ratio of 4-(methylsulfonyl)phenol, phenol, and sodium p-aminobenzenesulfonate is (1-1.2):(0.8-1):1; the aldehyde aqueous solution is prepared by mixing formaldehyde, 1,8-diadehydic anthracene, and water in a ratio of 1 mol:(0.8-1) mol:(400-500) mL; In step S2, the amount of amide-modified sodium lignin sulfonate is 10%-15% of the mass of the first substance; the preparation method of amide-modified sodium lignin sulfonate comprises the following steps: (1) Mix sodium lignin sulfonate, hydrogen peroxide and water evenly, adjust the pH to 3-4, heat the reaction, centrifuge, immerse, precipitate, wash and dry to obtain oxidized sodium lignin sulfonate; (2) Under a nitrogen atmosphere, oxidized sodium lignin sulfonate, sodium persulfate and water are uniformly mixed, heated once, and an aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid is added dropwise, heated twice for reaction, impregnated, precipitated, washed and dried to obtain the product; wherein the mass ratio of oxidized sodium lignin sulfonate, sodium persulfate and 2-acrylamido-2-methylpropanesulfonic acid is 1:(0.02-0.05):(0.3-0.7); In step S3, the mass ratio of nano-silicon dioxide to the second substance is (0.05-0.1):

1.

2. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In step S1, the molar ratio of formaldehyde to sodium p-aminobenzenesulfonate is (0.6-0.7):

1.

3. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In the step S1, the temperature of the first heating is 65-75° C., and the time of the dropwise addition is 1-3 hours; the temperature of the second heating reaction is 85-95° C., and the time of the second heating reaction is 4-6 hours.

4. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In step S2, the reaction temperature is 90-95° C., and the reaction time is 1-3 hours.

5. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In the step (1), the mass ratio of sodium lignin sulfonate to hydrogen peroxide is 1:(0.1-0.15); the temperature of the temperature-raising reaction is 65-75° C., and the temperature-raising reaction time is 4-5 hours.

6. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In the step (2), the mass fraction of the 2-acrylamido-2-methylpropanesulfonic acid aqueous solution is 20%-25%; the temperature of the first heating is 60-65°C; the time of the dropwise addition is 2-2.5 hours; the temperature of the second heating reaction is 70-80°C, and the time of the second heating reaction is 3-4 hours.

7. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In step S3, the mass fraction of the nano-silica suspension is 15%-20%.

8. The method for preparing a sulfamic acid-based water reducer according to claim 1, wherein: In step S3, the reaction temperature is 60-65° C., and the reaction time is 3-4 hours.

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