Heat-resistant moisture-proof slow-release ester powder water reducing agent and preparation method thereof

Abstract

The application discloses a heat-resistant moisture-proof slow-release ester powder water reducing agent and a preparation method thereof. The main body of the ester water reducing agent is composed of methacrylic acid and polyethylene glycol monomethyl ether methacrylate polymerization, a temperature-sensitive monomer and a small amount of unsaturated hydrophobic ester monomer are added into the main body, and finally the liquid water reducing agent obtained through polymerization is further subjected to dehydration esterification crosslinking reaction with a crosslinking agent. After the reaction is completed and cooled, the final powder water reducing agent is obtained through slicing and powdering. Compared with the existing ester solid water reducing agent technology, the heat-resistant moisture-proof, hydrolysis-resistant and long-time storage ester powder water reducing agent has a slow-release effect in concrete and has a good market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of water reducing agents, and in particular to a heat-resistant, moisture-proof, slow-release ester powder water reducing agent and a preparation method thereof. Background Art

[0002] In recent years, the number of powder water reducers has increased due to the control of transportation costs and the need to use powder water reducers in special applications such as dry mortar and grouting materials. At present, the preparation methods of powder water reducers mainly include the following methods: (1) Spray drying method. As the mainstream preparation method of powder water reducers used by major manufacturers at home and abroad, it has the advantages of uniform product particles and stable performance, but its disadvantages such as high equipment investment, high energy consumption, and potential safety hazards are also criticized by the industry. (2) Bulk polymerization method. This method is an important method for synthesizing polycarboxylic acid water reducers, but it has the disadvantages of high material viscosity, difficulty in stirring, difficult to control reaction heat, and easy polymerization in industrial production. (3) Esterification method. As a relatively traditional preparation method of powder water reducers, the ester water reducer prepared by the esterification method has the advantages of good workability and strong adaptability, but the problem of easy hydrolysis of ester water reducers makes it difficult to be better popularized. On the one hand, in a high temperature and humidity environment, it is easy to absorb moisture, melt and agglomerate, which reduces its storage stability. On the other hand, under the alkaline conditions of concrete, it hydrolyzes quickly and has poor retention, making it difficult to meet the requirements for concrete transportation and use.

[0003] In summary, spray drying does not meet the current trend of green and environmentally friendly production, and bulk polymerization does not meet the requirements of large-scale industrial production. If the problems of rapid loss during use and storage instability in high-temperature and humid environments of ester powder water reducers can be solved, they will surely have a broader prospect in the powder polycarboxylate water reducer market. Summary of the Invention

[0004] 1. Technical problems to be solved:

[0005] In response to the above technical problems, the present invention provides a heat-resistant, moisture-proof, sustained-release ester powder water reducer and a preparation method thereof. The main body of the ester water reducer is formed by polymerizing methacrylic acid and polyethylene glycol monomethyl ether methacrylate, to which a temperature-sensitive monomer and a small amount of unsaturated hydrophobic ester monomer are added. Finally, the liquid water reducer obtained by the polymerization is further subjected to a dehydration esterification and cross-linking reaction with a cross-linking agent to obtain the final powder water reducer.

[0006] 2. Technical solution:

[0007] A heat-resistant and moisture-proof slow-release ester powder water reducer, characterized in that the structure of the water reducer is as follows:

[0008]

[0009] wherein a is an integer of 51 to 78; b is an integer of 17 to 26; c is an integer of 2 to 4; d is an integer of 3 to 8; n is 20; A is one of glycerol and trimethylolpropane; and B is one of methyl methacrylate, ethyl methacrylate, and butyl methacrylate.

[0010] A method for preparing a heat-resistant and moisture-proof slow-release ester powder water reducer comprises the following steps:

[0011] Step 1: Add polyethylene glycol monomethyl ether methacrylate and an oxidant to a three-necked flask with a stirrer and mix them evenly. Then, dropwise add a reducing agent and a solution of methacrylic acid, a temperature-sensitive monomer, a hydrophobic unsaturated ester small monomer, and a chain transfer agent to the three-necked flask to carry out a free radical polymerization reaction. After the reaction is completed, a liquid ester polycarboxylate water reducer is obtained.

[0012] Step 2: Add the liquid ester polycarboxylic acid water reducer, crosslinking agent and catalyst into a single-necked flask for dehydration esterification reaction. After the reaction is complete, cool it, slice it and grind it into powder to obtain the final ester powder water reducer.

[0013] Furthermore, in step 1, the molar ratio of polyethylene glycol monomethyl ether methacrylate, oxidant, reducing agent, methacrylic acid, temperature-sensitive monomer, hydrophobic unsaturated ester monomer, and chain transfer agent is: 1: (0.03-0.2): (0.03-0.1): 3: (0.1-0.2): (0.05-0.1): (0.01-0.05).

[0014] Furthermore, the temperature-sensitive monomer is N-isopropylacrylamide.

[0015] Furthermore, the hydrophobic unsaturated ester small monomer is one of methyl methacrylate, ethyl methacrylate, and butyl methacrylate; the oxidant is one of ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one of sodium bisulfite, sodium sulfite, bleaching agent, ascorbic acid, sodium ascorbate, isoascorbic acid, and sodium hypophosphite; and the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecyl mercaptan, and sodium hypophosphite.

[0016] Furthermore, the temperature of the free radical polymerization reaction in step 1 is carried out at 10-35° C., and the reaction time is 3 hours.

[0017] Furthermore, in step 2, the cross-linking agent is one of glycerol and trimethylolpropane; the catalyst is one of concentrated sulfuric acid, phosphoric acid, and p-toluenesulfonic acid; and the molar ratio of the water reducer, the cross-linking agent, and the catalyst is 150:50:1.

[0018] Furthermore, the dehydration esterification reaction in step 2 is carried out at 125° C. to 155° C., and after the dehydration is complete, the reaction is continued at a vacuum degree of -0.1 MPa for 3 to 5 hours.

[0019] Furthermore, the molecular weight of the final ester powder water reducer in step 2 is 66,000 to 102,000 g / mol.

[0020] 3.Beneficial effects:

[0021] (1) The powder water reducer prepared by the present invention is composed of a main body of an ester water reducer formed by polymerization of methacrylic acid and polyethylene glycol monomethyl ether methacrylate, to which a temperature-sensitive monomer and a small amount of unsaturated hydrophobic ester monomer are added, and finally the liquid water reducer obtained by polymerization is further subjected to a dehydration esterification cross-linking reaction with a cross-linking agent to obtain the final powder water reducer. The incorporation of the temperature-sensitive monomer allows the polymer as a whole to remain hydrophilic below the lower critical solution temperature (LCST) of 32°C, while it becomes hydrophobic above 32°C. The incorporation of a small amount of hydrophobic ester monomer can, on the one hand, make the LCST of the polymer as a whole clearer, and on the other hand, it can also make it slightly hydrophobic below the LCST, so that the polymer obtained has a better moisture-proof effect during storage. In addition, in concrete, the hydrophobic monomer hinders water molecules from invading the ester bond connecting the main chain and the side chain to a certain extent, thereby protecting the side chain and reducing the hydrolysis rate. The macromolecular water reducer obtained after the cross-linking reaction not only greatly increases the glass transition temperature and improves its heat resistance during storage, but also can achieve a sustained release effect brought about by the slow hydrolysis of the cross-linked structure to the hydrophobic ester monomer layer by layer in the alkaline environment of concrete.

[0022] (2) The heat-resistant and moisture-proof slow-release ester powder water reducer prepared by the present invention is different from ordinary ester water reducers that are prone to agglomeration and hydrolysis during storage. It can also be stored for a long time in a high-temperature and humid environment and its performance remains stable.

[0023] (3) The heat-resistant and moisture-proof slow-release ester powder water reducer prepared by the present invention not only has a high water reduction rate in concrete, but also, thanks to its special structure, it slowly hydrolyzes layer by layer in alkaline conditions, thereby achieving a slow-release and continuous dispersion effect, solving the problem of rapid loss caused by rapid hydrolysis of ordinary ester water reducers in alkaline environments. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, but not all embodiments.

[0025] Unless otherwise specified, the experimental materials and reagents used in the following examples can be obtained from commercial sources.

[0026] Example 1

[0027] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate having a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.03 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.2 mol of N-isopropylacrylamide, 0.1 mol of butyl methacrylate, and 0.01 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to conduct a free radical polymerization reaction. After completion of the reaction, a liquid ester polycarboxylic acid water reducer was obtained.

[0028] Step S02: 3 mol of liquid ester polycarboxylate water-reducing agent and 1 mol of trimethylolpropane were added to a single-necked flask. After the temperature reached 155°C, the flask was vacuumed to -0.1 MPa for dehydration. After dehydration, 0.02 mol of concentrated sulfuric acid was added and the reaction continued for 5 hours. Finally, the flask was cooled, sliced, and ground to obtain the final ester powder water-reducing agent with a molecular weight of 102,000 g / mol.

[0029] The structural formula is shown below.

[0030]

[0031] Example 2

[0032] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.1 mol of sodium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.15 mol of N-isopropylacrylamide, 0.08 mol of butyl methacrylate, and 0.03 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to carry out a free radical polymerization reaction. After the reaction was completed, a liquid ester polycarboxylic acid water-reducing agent was obtained. Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane were added to a single-necked flask. After the temperature was raised to 155° C., the flask was evacuated to -0.1 MPa for dehydration. After the dehydration was completed, 0.02 mol of concentrated sulfuric acid was added, and the reaction was continued for 4 hours. Finally, the product is cooled, sliced, and ground to obtain the final ester powder water reducer with a molecular weight of 84,000 g / mol. The structural formula is shown below.

[0033]

[0034] Example 3

[0035] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.2 mol of potassium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of butyl methacrylate, and 0.05 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to carry out a free radical polymerization reaction. After the reaction was completed, a liquid ester polycarboxylic acid water-reducing agent was obtained. Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane were added to a single-necked flask. After the temperature was raised to 155° C., the flask was evacuated to -0.1 MPa for dehydration. After the dehydration was completed, 0.02 mol of concentrated sulfuric acid was added, and the reaction was continued for 3 hours. Finally, the product is cooled, sliced, and ground to obtain the final ester powder water reducer with a molecular weight of 66,000 g / mol. The structural formula is shown below.

[0036]

[0037] Example 4

[0038] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.2 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of ethyl methacrylate, and 0.05 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to carry out a free radical polymerization reaction. After the reaction was completed, a liquid ester polycarboxylic acid water-reducing agent was obtained. Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane were added to a single-necked flask. After the temperature was raised to 155° C., the flask was evacuated to -0.1 MPa for dehydration. After the dehydration was completed, 0.02 mol of phosphoric acid was added, and the reaction was continued for 3 hours. Finally, the product is cooled, sliced, and ground to obtain the final ester powder water reducer with a molecular weight of 66,000 g / mol. The structural formula is shown below.

[0039]

[0040] Example 5

[0041] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.03 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.2 mol of N-isopropylacrylamide, 0.1 mol of methyl methacrylate, and 0.01 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to carry out a free radical polymerization reaction. After the reaction was completed, a liquid ester polycarboxylic acid water-reducing agent was obtained. Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane were added to a single-necked flask. After the temperature was raised to 155° C., the flask was evacuated to -0.1 MPa for dehydration. After the dehydration was completed, 0.02 mol of phosphoric acid was added, and the reaction was continued for 5 hours. Finally, the product is cooled, sliced, and ground to obtain the final ester powder water reducer with a molecular weight of 102,000 g / mol. The structural formula is shown below.

[0042]

[0043] Example 6

[0044] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.2 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution prepared by mixing 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of butyl methacrylate, and 0.05 mol of thioglycolic acid were simultaneously added dropwise to the three-necked flask at 25° C. over a period of 3 hours to carry out a free radical polymerization reaction. After the reaction was completed, a liquid ester polycarboxylic acid water-reducing agent was obtained. Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of glycerol were added to a single-necked flask. After the temperature was raised to 155° C., the mixture was evacuated to -0.1 MPa for dehydration. After the dehydration was completed, 0.02 mol of p-toluenesulfonic acid was added, and the reaction was continued for 3 hours. Finally, the product is cooled, sliced, and ground to obtain the final ester powder water reducer with a molecular weight of 66,000 g / mol. The structural formula is shown below.

[0045]

[0046] Comparative Example 1

[0047] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate (MW 1000 g / mol, 93% esterification yield) and 0.03 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution of 3 mol of methacrylic acid and 0.01 mol of thioglycolic acid were simultaneously added dropwise to the flask at 25°C over a period of 3 hours for a free radical polymerization reaction. Upon completion, a liquid ester polycarboxylate water-reducing agent with a molecular weight of 33,000 g / mol was obtained. Finally, the mixture was heated to 155°C for dehydration, cooled, sliced, and ground to obtain the final powdered water-reducing agent. The structural formula is shown below.

[0048]

[0049] Comparative Example 2

[0050] Step S01: 1 mol of polyethylene glycol monomethyl ether methacrylate (MW 1000 g / mol, 93% esterification yield) and 0.2 mol of ammonium persulfate were added to a three-necked flask with a stirrer and mixed uniformly. Subsequently, 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution of 3 mol of methacrylic acid and 0.05 mol of thioglycolic acid were simultaneously added dropwise to the flask at 25°C over a period of 3 hours for a free radical polymerization reaction. Upon completion, a liquid ester polycarboxylate water-reducing agent with a molecular weight of 21,000 g / mol was obtained. Finally, the mixture was heated to 125°C for dehydration, cooled, sliced, and ground to obtain the final powdered water-reducing agent. The structural formula is shown below.

[0051]

[0052] Test Case

[0053] 1. Heat and moisture resistance test

[0054] Unlike conventional ester-based powdered water reducers, which can experience melting, moisture absorption, agglomeration, and hydrolysis during long-term storage, especially in high-temperature and humid environments (summer), the present invention utilizes a unique structure to enhance the heat and moisture resistance of the powdered water reducer, thereby reducing performance losses caused by agglomeration and hydrolysis. Table 1 shows whether the Examples and Comparative Examples exhibited melting and agglomeration at different temperatures. The Comparative Examples exhibited slight agglomeration starting at 35°C, while the Examples did not exhibit slight agglomeration until at least 50°C. Furthermore, the lower agglomeration temperature gradually increased with increasing molecular weight, demonstrating significantly improved heat resistance. Table 2 shows the agglomeration and conversion rate trends of the water reducers at different storage times under simulated summer temperature and humidity conditions. The Comparative Examples exhibited slight agglomeration and a slightly decreasing conversion rate after three months of storage, while only a few of the Examples exhibited slight agglomeration and a slightly decreasing conversion rate after nine months of storage. This demonstrates that the present invention improves the moisture resistance of the water reducer, ensuring stable performance during storage.

[0055] Table 1 Agglomeration and melting phenomena of water reducer at different temperatures

[0056]

[0057] Table 2. Agglomeration and conversion rate trends of water reducers at different storage times (simulated summer temperature and humidity: temperature 35°C; humidity 80%)

[0058]

[0059] 2. Cement paste test

[0060] Referring to GB / T 8077-2012, "Test Method for Homogeneity of Concrete Admixtures," the examples and comparative examples were tested for paste fluidity. The results are shown in Table 3. The water-cement ratio was 0.29, and the water reducer dosage was 0.12% of the cement content. Initial fluidity, 0.5-hour fluidity, 1-hour fluidity, and 1.5-hour fluidity were tested. The results showed that while the initial fluidity of the examples and comparative examples was similar, the 0.5-hour and 1-hour fluidities of the examples were significantly greater than those of the comparative examples, and some examples could maintain fluidity for 1.5 hours. This demonstrates that the present invention significantly improves the retention performance of ester water reducers.

[0061] Table 3 Fluidity and time loss of pure pulp

[0062]

[0063] Although the present invention has been disclosed above in terms of preferred embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims of this application.

Claims

1. A method for preparing a heat-resistant and moisture-proof slow-release ester powder water reducer, characterized in that: The following steps are involved: Step 1: Add polyethylene glycol monomethyl ether methacrylate and an oxidant to a three-necked flask with a stirrer and mix them evenly. Then, add an aqueous solution of a reducing agent and a solution of methacrylic acid, a temperature-sensitive monomer, a hydrophobic unsaturated ester monomer, and a chain transfer agent dropwise to the three-necked flask to carry out a free radical polymerization reaction. After the reaction is completed, a liquid ester polycarboxylate water reducer is obtained. Step 2: Add the liquid ester polycarboxylic acid water reducer, the crosslinking agent and the catalyst into a single-necked flask for dehydration esterification reaction. After the reaction is complete, cool the mixture, slice it and grind it into powder to obtain the final ester powder water reducer. In step 1, the molar ratio of polyethylene glycol monomethyl ether methacrylate, oxidant, reducing agent, methacrylic acid, temperature-sensitive monomer, hydrophobic unsaturated ester monomer, and chain transfer agent is: 1: (0.03-0.2): (0.03-0.1): 3: (0.1-0.2): (0.05-0.1): (0.01-0.05); The temperature-sensitive monomer is N-isopropylacrylamide; The hydrophobic unsaturated ester monomer is one of methyl methacrylate, ethyl methacrylate, and butyl methacrylate; the oxidant is one of ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one of sodium bisulfite, sodium sulfite, bleaching agent, ascorbic acid, sodium ascorbate, isoascorbic acid, and sodium hypophosphite; the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecyl mercaptan, and sodium hypophosphite; In step 2, the crosslinking agent is one of glycerol and trimethylolpropane; the catalyst is one of concentrated sulfuric acid, phosphoric acid, and p-toluenesulfonic acid; and the molar ratio of the liquid ester polycarboxylic acid water reducer, the crosslinking agent, and the catalyst is 150:50:

1.

2. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer according to claim 1, characterized in that: The temperature of the free radical polymerization reaction in step 1 is carried out at 10-35° C., and the reaction time is 3 h.

3. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer according to claim 1, characterized in that: The dehydration esterification reaction in step 2 is carried out at 125° C. to 155° C., and after the dehydration is complete, the reaction is continued at a vacuum degree of -0.1 MPa for 3 to 5 hours.

4. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer according to claim 1, characterized in that: The molecular weight of the final ester powder water reducer in step 2 is 66,000~102,000 g / mol.

5. A heat-resistant and moisture-proof slow-release ester powder water reducer prepared by the preparation method according to any one of claims 1 to 4.

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