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

Abstract

The invention discloses a heat-resistant moisture-proof slow-release ester powder water reducer and a preparation method thereof, methacrylic acid and polyethylene glycol monomethyl ether methacrylate are polymerized to form a main body of the ester water reducer, and a temperature-sensitive monomer and a small amount of unsaturated hydrophobic ester monomer are added into the main body; finally, the liquid water reducer obtained through polymerization and a cross-linking agent are further subjected to a dehydration esterification cross-linking reaction, after the reaction is completed and cooling is conducted, slicing and grinding are conducted finally, and the final powder water reducer is obtained. Compared with the existing ester solid water reducing agent technology, the ester solid water reducing agent has the characteristics of heat resistance, moisture resistance, hydrolysis resistance and long-time storage, has a slow release effect in concrete, and has a good market prospect.

Description

Technical Field

[0001] The 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 fact that powder water reducers must be used 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. 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. This method is an important method for synthesizing polycarboxylic acid water reducers, but it has the disadvantages of high material viscosity, difficult stirring, difficult to control reaction heat, and easy polymerization in industrial production. (3) Esterification. As a more traditional preparation method of powder water reducers, the ester water reducers prepared by the esterification method have 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 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, the spray drying method does not meet the current trend of green and environmentally friendly production, and the bulk polymerization method does not meet the conditions for large-scale industrial production. If the problems of rapid loss of ester powder water reducers during use and unstable storage in high temperature and humidity environments can be solved, it will definitely have a broader prospect in powder polycarboxylic acid water reducers. Summary of the invention

[0004] 1. Technical problems to be solved:

[0005] In view of the above technical problems, the present invention provides a heat-resistant and 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, a temperature-sensitive monomer and a small amount of unsaturated hydrophobic ester monomer are added thereto, and finally the liquid water reducer obtained by the polymerization is further subjected to a dehydration esterification 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 sustained-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 propylene glycol 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-reducing agent comprises the following steps:

[0011] Step 1: Add polyethylene glycol monomethyl ether methacrylate and an oxidant into a three-necked flask with a stirrer and mix them evenly, then drop a reducing agent and a solution mixed with methacrylic acid, a temperature-sensitive monomer, a hydrophobic unsaturated ester small monomer and a chain transfer agent into the three-necked flask to carry out a free radical polymerization reaction, and after the reaction is completed, a liquid ester polycarboxylic acid water reducer is obtained;

[0012] 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.

[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; the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecanol, 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 66000-102000 g / mol.

[0020] 3. Beneficial effects:

[0021] (1) The powder water reducer prepared by the present invention is 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, and to become hydrophobic above 32°C. The incorporation of a small amount of hydrophobic ester monomers can, on the one hand, make the LCST of the polymer as a whole clearer, and on the other hand, 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-reducing agent 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 layer-by-layer hydrolysis from the cross-linked structure to the hydrophobic ester monomer in the alkaline environment of concrete.

[0022] (2) The heat-resistant and moisture-proof sustained-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 with stable performance.

[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, due 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 is described in detail below with reference to specific embodiments. The described embodiments are only partial 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 with a molecular weight of 1000 g / mol and an esterification rate of 93% and 0.03 mol of ammonium persulfate are added to a three-necked flask with a stirrer and mixed evenly, and then 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.2 mol of N-isopropylacrylamide, 0.1 mol of butyl methacrylate and 0.01 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and after the reaction is completed, a liquid ester polycarboxylic acid water reducer is obtained;

[0028] Step S02: Add 3 mol of liquid ester polycarboxylic acid water reducer and 1 mol of trimethylolpropane into a single-necked flask, and after the temperature rises to 155°C, evacuate to -0.1 MPa for dehydration, add 0.02 mol of concentrated sulfuric acid after dehydration, and continue to react for 5 hours. Finally, cool, slice, and grind to obtain the final ester powder water reducer with a molecular weight of 102000 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 are added to a three-necked flask with a stirrer and mixed evenly, and then 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.15 mol of N-isopropylacrylamide, 0.08 mol of butyl methacrylate and 0.03 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and a liquid ester polycarboxylic acid water-reducing agent is obtained after the reaction is completed; Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane are added to a single-necked flask, and after the temperature rises to 155° C., the flask is evacuated to -0.1 MPa for dehydration, and after the dehydration is completed, 0.02 mol of concentrated sulfuric acid is added, and the reaction is continued for 4 hours. Finally, the mixture is cooled, sliced ​​and ground to obtain the final ester powder water reducer with a molecular weight of 84000 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 are added to a three-necked flask with a stirrer and mixed evenly, and then 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of butyl methacrylate and 0.05 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and a liquid ester polycarboxylic acid water-reducing agent is obtained after the reaction is completed; Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane are added to a single-necked flask, and after the temperature rises to 155° C., the flask is evacuated to -0.1 MPa for dehydration, and after the dehydration is completed, 0.02 mol of concentrated sulfuric acid is added, and the reaction is continued for 3 hours. Finally, the mixture is cooled, sliced ​​and ground to obtain the final ester powder water reducer with a molecular weight of 66000 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 are added to a three-necked flask with a stirrer and mixed evenly, and then 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of ethyl methacrylate and 0.05 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and a liquid ester polycarboxylic acid water-reducing agent is obtained after the reaction is completed; Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane are added to a single-necked flask, and after the temperature rises to 155° C., the flask is evacuated to -0.1 MPa for dehydration, and after the dehydration is completed, 0.02 mol of phosphoric acid is added, and the reaction is continued for 3 hours. Finally, cooling, slicing and grinding are performed to obtain the final ester powder water reducer with a molecular weight of 66000 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 are added to a three-necked flask with a stirrer and mixed evenly, and then 0.03 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.2 mol of N-isopropylacrylamide, 0.1 mol of methyl methacrylate and 0.01 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and a liquid ester polycarboxylic acid water-reducing agent is obtained after the reaction is completed; Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of trimethylolpropane are added to a single-necked flask, and after the temperature rises to 155° C., the flask is evacuated to -0.1 MPa for dehydration, and after the dehydration is completed, 0.02 mol of phosphoric acid is added, and the reaction is continued for 5 hours. Finally, the mixture is cooled, sliced ​​and ground to obtain the final ester powder water reducer with a molecular weight of 102000 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 are added to a three-necked flask with a stirrer and mixed evenly, and then 0.1 mol of a 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid, 0.1 mol of N-isopropylacrylamide, 0.05 mol of butyl methacrylate and 0.05 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask at 25° C. within 3 hours to carry out a free radical polymerization reaction, and a liquid ester polycarboxylic acid water-reducing agent is obtained after the reaction is completed; Step S02: 3 mol of the liquid ester polycarboxylic acid water-reducing agent and 1 mol of glycerol are added to a single-necked flask, and after the temperature rises to 155° C., the flask is evacuated to -0.1 MPa for dehydration, and after the dehydration is completed, 0.02 mol of p-toluenesulfonic acid is added, and the reaction is continued for 3 hours. Finally, the mixture is cooled, sliced ​​and ground to obtain the final ester powder water reducer with a molecular weight of 66000 g / mol. The structural formula is shown below.

[0045]

[0046] Comparative Example 1

[0047] Step S01: Add 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 to a three-necked flask with a stirrer and mix them evenly. Then, at 25°C, 0.03 mol of 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid and 0.01 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask within 3 hours to carry out free radical polymerization reaction. After the reaction is completed, a liquid ester polycarboxylic acid water reducer is obtained with a molecular weight of 33000 g / mol. Finally, the temperature is raised to 155°C for dehydration, cooling, slicing, and grinding to obtain the final powder water reducer. The structural formula is shown below.

[0048]

[0049] Comparative Example 2

[0050] Step S01: Add 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 to a three-necked flask with a stirrer and mix them evenly. Then, at 25°C, 0.1 mol of 0.6 wt.% aqueous solution of ascorbic acid and a solution mixed with 3 mol of methacrylic acid and 0.05 mol of thioglycolic acid are simultaneously added dropwise to the three-necked flask within 3 hours to carry out free radical polymerization reaction. After the reaction is completed, a liquid ester polycarboxylic acid water reducer is obtained with a molecular weight of 21000 g / mol. Finally, the temperature is raised to 125°C for dehydration, cooling, slicing, and grinding to obtain the final powder water reducer. The structural formula is shown below.

[0051]

[0052] Test Case

[0053] 1. Heat and moisture resistance test

[0054] The present invention is different from the common ester powder water reducer, which will melt, absorb moisture, agglomerate and hydrolyze under long-term storage, especially in a high temperature and humidity environment (summer). The special structure improves the heat resistance and moisture resistance of the powder water reducer, thereby reducing the performance loss caused by agglomeration and hydrolysis. Table 1 shows whether the embodiments and comparative examples have melting and agglomeration at different temperatures. The comparative example basically starts to have a slight agglomeration phenomenon at 35°C, while the worst embodiment will only slightly agglomerate at 50°C, and as the molecular weight increases, the lower limit temperature of agglomeration gradually increases. It shows that its heat resistance is significantly improved. Table 2 shows the agglomeration phenomenon and conversion rate change trend of the water reducer at different storage times under the temperature and humidity conditions simulated in summer. It can be seen that the comparative example has a slight agglomeration phenomenon after 3 months of storage, and the conversion rate also shows a slightly decreasing trend, while only a few of the embodiments have a slight agglomeration phenomenon and a slightly decreasing trend in the conversion rate after 9 months of storage. It shows that the present invention improves the moisture resistance of the water reducer and ensures the stability of the performance of the water reducer during storage.

[0055] Table 1 Agglomeration and melting of water reducing agent at different temperatures

[0056]

[0057] Table 2 The agglomeration phenomenon and conversion rate change trend of water reducer at different storage times (simulated summer temperature and humidity: temperature 35℃; humidity 80%)

[0058]

[0059] 2. Cement paste test

[0060] With reference to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures", the embodiment and the comparative example were tested for the fluidity of the pure paste, and the results are shown in Table 3. Among them, the water-cement ratio was 0.29, the water-reducing agent dosage was 0.12% of the cement dosage, and the initial fluidity, 0.5h fluidity, 1h fluidity and 1.5h fluidity were tested respectively. The results show that the initial fluidity of the embodiment and the comparative example is not much different, while the 0.5h fluidity and 1h fluidity of the embodiment are significantly greater than those of the comparative example, and some embodiments can be maintained for 1.5h. It shows that the present invention significantly improves the retention performance of the ester water-reducing agent.

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

[0062]

[0063] Although the present invention has been disclosed as 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 heat-resistant and moisture-proof sustained-release ester powder water reducer, characterized in that: The structure of the water reducing agent is as follows: 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 propylene glycol and trimethylolpropane; and B is one of methyl methacrylate, ethyl methacrylate and butyl methacrylate.

2. A method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer, which is used to prepare the water reducer as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Add polyethylene glycol monomethyl ether methacrylate and an oxidant into a three-necked flask with a stirrer and mix them evenly, then drop a reducing agent and a solution mixed with methacrylic acid, a temperature-sensitive monomer, a hydrophobic unsaturated ester small monomer and a chain transfer agent into the three-necked flask to carry out a free radical polymerization reaction, and after the reaction is completed, a liquid ester polycarboxylic acid 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.

3. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water-reducing agent according to claim 2, characterized in that: 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).

4. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer according to claim 2, characterized in that: The temperature-sensitive monomer is N-isopropylacrylamide.

5. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water-reducing agent according to claim 2, characterized in that: 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; the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecanol, and sodium hypophosphite.

6. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water-reducing agent according to claim 2, 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.

7. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water reducer according to claim 2, characterized in that: 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.

8. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water-reducing agent according to claim 2, 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.

9. The method for preparing a heat-resistant and moisture-proof sustained-release ester powder water-reducing agent according to claim 2, characterized in that: The molecular weight of the final ester powder water reducer in step 2 is 66000-102000 g / mol.

Images