Mechano-chemical green efficient controllable synthesis method of polycarboxylic acid high-performance water reducing agent

Abstract

The invention discloses a green, efficient and controllable synthesis method of a polycarboxylic acid high-performance water reducing agent, and belongs to the field of cement concrete admixtures. According to the invention, a macromonomer isopentenyl polyoxyethylene ether (TPEG), a micromonomer acrylic acid (AA), a chain transfer agent sodium methallyl sulfonate (MAS), an initiator ammonium persulfate (APS) and the like are subjected to mechanochemical free radical polymerization reaction through mechanical mixing to prepare the polycarboxylic acid high-performance water reducing agent. According to the method, efficient, green and controllable production of the polycarboxylic acid high-performance water reducing agent is achieved, no organic solvent is used in the production process, the process is simple, the time is short (less than or equal to 90 minutes), and the prepared polycarboxylic acid high-performance water reducing agent is excellent in dispersity and high in product concentration (gt; the method is convenient to transport and use, capable of greatly reducing energy consumption, low in cost and suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixtures and relates to a preparation method of a water reducer, in particular to a mechanochemical green, efficient and controllable synthesis method of a polycarboxylic acid high-performance water reducer. Background Art

[0002] Cement and concrete are the most abundant man-made materials in the world, with an annual output of billions of tons, but the carbon footprint of cement and concrete is very large, accounting for 7% of global carbon dioxide emissions. Polycarboxylate water reducers are the third generation of high-performance water reducers developed after the first generation of ordinary water reducers represented by lignin sulfonates and the second generation of high-efficiency water reducers represented by melamine and naphthalene series. Polycarboxylate water reducers have strong adaptability to concrete and can well improve the workability of concrete. At the same time, due to its unique comb-like structure, its molecular structure has good designability, and the synthesis process is environmentally friendly, which is the development direction and research hotspot of high-performance water reducers.

[0003] At present, polycarboxylate water reducers are mostly produced by aqueous solution polymerization. However, the reaction time exceeds 4 hours, the product concentration is low, only 10-40wt%, and the admixture manufacturer is generally far away from the construction site. Low solid content products will lead to high transportation costs and inconvenient product storage. Under high temperature conditions in summer, due to the addition of sugars as retarders, the microorganisms in the polycarboxylate water reducer multiply and metabolize in large quantities, resulting in the polycarboxylate water reducer becoming sour and smelly, the liquid turning black, and the liquid surface growing bacteria and other mildew phenomena, and the performance of the polycarboxylate water reducer is seriously reduced. In addition, the aqueous solution of polycarboxylate water reducer cannot be directly used in dry-mixed mortar, high-strength grouting, thermal insulation mortar, plastering mortar or ceramic bonding mortar and other application scenarios. At present, the main production method of high-concentration polycarboxylate water reducer is to use a high-temperature spray drying process to dry and dehydrate the product prepared by the aqueous solution polymerization method. The production process of this method is mature, but the high temperature of the drying process leads to a decrease in the performance of the water reducer, and the energy consumption cost is high. Therefore, it is a research and production trend to develop a synthetic method for directly obtaining high-concentration polycarboxylate water reducer. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a polycarboxylic acid water reducer. The present invention is to synthesize a polycarboxylic acid water reducer by mechanical mixing, which can shorten the synthesis reaction time to 90 minutes, has a simple process, consumes less time, does not add organic solvents, has low cost, has a high yield of the obtained polycarboxylic acid water reducer, and is easy to store and transport.

[0005] The present invention provides a method for preparing a polycarboxylic acid-based water reducer, and the specific steps are as follows:

[0006] After reaching the set reaction temperature and speed, the macromonomer isopentyl polyoxyethylene ether (TPEG) and the initiator ammonium persulfate (APS) are added to the mixing chamber according to the corresponding molar ratio, and after TPEG and APS are completely melted, the small monomer acrylic acid (AA), the chain transfer agent sodium methyl acrylate sulfonate (MAS) and half of the ultrapure water required for the reaction are added; at this time, the mechanochemical free radical polymerization reaction begins, and when half of the required reaction time is reached, the remaining AA, MAS and ultrapure water are added to continue the mechanochemical free radical polymerization reaction; after the above reaction is completed, an inhibitor is added, and the obtained product is removed to obtain a polycarboxylic acid high-performance water reducer.

[0007] Furthermore, the weight average molecular weight of the TPEG is 2400.

[0008] Furthermore, the molar ratio of the TPEG macromonomer, AA micromonomer and MAS is 1.0:2.5-3.0:0.08-0.16.

[0009] Furthermore, the amount of ultrapure water is 0.7 wt % of the mass of TPEG.

[0010] Furthermore, the amount of the APS is 0.8-1.2 wt % of the mass of TPEG.

[0011] Furthermore, the reaction temperature is 60-70°C.

[0012] Furthermore, the above rotation speed is 65-75R / min.

[0013] Furthermore, the above reaction time is 60 to 90 minutes.

[0014] Furthermore, the amount of the polymerization inhibitor is 0.03wt% of the mass of TPEG. The polymerization inhibitor is selected from hydroquinone (HQ).

[0015] The invention realizes efficient, green and controllable production of polycarboxylic acid high-performance water-reducing agent, does not use organic solvents in the production process, has a simple process, and a short time (≤90 minutes), and the obtained polycarboxylic acid high-performance water-reducing agent has excellent dispersibility and high product concentration (>99wt%), is convenient for transportation and use, can greatly reduce energy consumption, has low cost, and is suitable for industrial large-scale production. Compared with the existing preparation method, it has significant characteristics and substantial progress. DETAILED DESCRIPTION

[0016] The present invention is further illustrated and described below in conjunction with specific implementation modes, but the present invention is not limited in any way.

[0017] The method for preparing a polycarboxylic acid high performance water reducing agent of the present invention comprises the following steps:

[0018] After reaching the set reaction temperature and speed, the macromonomer TPEG and the initiator APS are added to the mixing chamber in the corresponding molar ratio. After TPEG and APS are completely melted, half of the amount of AA, MAS and ultrapure water required for the reaction is added. At this time, the mechanochemical free radical polymerization reaction begins. When half of the required reaction time is reached, the remaining AA, MAS and ultrapure water are added to continue the mechanochemical free radical polymerization reaction. After the above reaction is completed, an inhibitor is added, and the obtained product is removed to obtain a polycarboxylic acid high-performance water reducer.

[0019] The steps in the preparation method of the water reducing agent are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0020] Example 1

[0021] Weigh the isopentenyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS) in a molar ratio of 1.0:2.5:0.08, weigh ammonium persulfate (APS) in an amount of 1.0wt% of the mass of TPEG and place it in beaker A containing TPEG, measure ultrapure water in an amount of 0.7wt% of the mass of TPEG and place it in beaker B containing AA and MAS and stir to completely dissolve MAS. Set the reaction temperature of the mixing chamber to 65°C and the speed to 65R / min, add TPEG and APS to the mixing chamber until they are completely melted. Then add half of AA, MAS and ultrapure water, and when the reaction time is more than half, add the remaining AA, MAS and ultrapure water, and react in the torque rheometer for 90 minutes. After the reaction was completed, a polymerization inhibitor, hydroquinone (HQ), was added in an amount of 0.03 wt % of the mass of TPEG. The reaction product was taken out, and finally a polycarboxylic acid-based high-performance water reducer was obtained, which was recorded as INPCE-1.

[0022] Example 2

[0023] Weigh the isopentenyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS) in a molar ratio of 1.0:2.5:0.08, weigh ammonium persulfate (APS) in an amount of 1.0wt% of the mass of TPEG and place it in beaker A containing TPEG, measure ultrapure water in an amount of 0.7wt% of the mass of TPEG and place it in beaker B containing AA and MAS and stir to completely dissolve MAS. Set the reaction temperature of the mixing chamber to 70°C and the speed to 70R / min, add TPEG and APS to the mixing chamber until they are completely melted. Then add half of AA, MAS and ultrapure water, and when the reaction time is more than half, add the remaining AA, MAS and ultrapure water, and react in the torque rheometer for 60 minutes. After the reaction, a polymerization inhibitor, hydroquinone (HQ), was added in an amount of 0.03 wt % of the mass of TPEG. The reaction product was taken out, and finally a polycarboxylic acid-based high-performance water reducer was obtained, which was recorded as INPCE-2.

[0024] Example 3

[0025] According to the molar ratio of 1.0:3.0:0.08 of isopentyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS), ammonium persulfate (APS) was weighed in an amount of 1.2wt% of the mass of TPEG and placed in beaker A containing TPEG, and ultrapure water was measured in an amount of 0.7wt% of the mass of TPEG and placed in beaker B containing AA and MAS and stirred to completely dissolve MAS. The reaction temperature of the mixing chamber was set to 60°C and the speed was 70R / min, and TPEG and APS were added to the mixing chamber until they were completely melted. Then half of AA, MAS and ultrapure water were added, and when the reaction time was more than half, the remaining AA, MAS and ultrapure water were added, and the reaction was carried out in the torque rheometer for 60min. After the reaction, hydroquinone (HQ) was added, and the reaction product was taken out, and finally the polycarboxylic acid high-performance water reducer was obtained and recorded as INPCE-3.

[0026] Example 4

[0027] Weigh the isopentenyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS) in a molar ratio of 1.0:3.0:0.12, weigh ammonium persulfate (APS) in an amount of 1.0wt% of the mass of TPEG and place it in beaker A containing TPEG, measure ultrapure water in an amount of 0.7wt% of the mass of TPEG and place it in beaker B containing AA and MAS and stir to completely dissolve MAS. Set the reaction temperature of the mixing chamber to 60°C and the speed to 70R / min, add TPEG and APS to the mixing chamber until they are completely melted. Then add half of AA, MAS and ultrapure water, and when the reaction time is more than half, add the remaining AA, MAS and ultrapure water, and react in the torque rheometer for 60 minutes. After the reaction was completed, a polymerization inhibitor, hydroquinone (HQ), was added in an amount of 0.03 wt % of the mass of TPEG. The reaction product was taken out, and finally a polycarboxylic acid-based high-performance water reducer was obtained, which was recorded as INPCE-4.

[0028] Example 5

[0029] Weigh the isopentenyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS) in a molar ratio of 1.0:3.0:0.16, weigh ammonium persulfate (APS) in an amount of 1.0wt% of the mass of TPEG and place it in beaker A containing TPEG, measure ultrapure water in an amount of 0.7wt% of the mass of TPEG and place it in beaker B containing AA and MAS and stir to completely dissolve MAS. Set the reaction temperature of the mixing chamber to 60°C and the speed to 70R / min, add TPEG and APS to the mixing chamber until they are completely melted. Then add half of AA, MAS and ultrapure water, and when the reaction time is more than half, add the remaining AA, MAS and ultrapure water, and react in the torque rheometer for 60 minutes. After the reaction was completed, a polymerization inhibitor, hydroquinone (HQ), was added in an amount of 0.03 wt % of the mass of TPEG. The reaction product was taken out, and finally a polycarboxylic acid-based high-performance water reducer was obtained, which was recorded as INPCE-5.

[0030] Comparative Example

[0031] Weigh the isopentenyl polyoxyethylene ether (TPEG) with a weight average molecular weight of 2400: acrylic acid (AA): sodium methyl propylene sulfonate (MAS) in a molar ratio of 1.0:3.0:0.12, and weigh ammonium persulfate (APS) in an amount of 1.0wt% of the mass of TPEG and place it in a beaker. Mix and dissolve in a three-necked flask equipped with a condenser according to the mass ratio of isopentenyl polyoxyethylene ether (TPEG): ultrapure water at a mass ratio of 1:2.38. At the same time, ultrapure water is measured at a mass ratio of TPEG:H2O of 1:1.07 and 1:2.62 to prepare initiator solution A (ammonium persulfate + water) and monomer mixed solution B (acrylic acid + sodium methyl propylene sulfonate + water). Heat the macromonomer to 60°C, add monomers A and B, and drip them in about 75 minutes. Heat to 75°C and keep warm for 3 hours. After the reaction was completed, a polymerization inhibitor, hydroquinone (HQ), was added in an amount of 0.03 wt % of the mass of TPEG, and the temperature was cooled to room temperature to finally obtain a polycarboxylic acid-based high-performance water reducer recorded as TPCE.

[0032] The water reducing agents obtained in the above examples and comparative examples were tested, and the results are shown in Table 1.

[0033] The solid content of the water reducing agent of each embodiment and comparative example was tested. The test used MB45 moisture meter (Ohaus, USA) to test the PCE solid content. The sample tray was placed in the moisture meter and the mass was reset to zero. The sample with a mass greater than 0.5g was placed in the sample tray and the test was started. After the sample reached a constant weight, the solid content of the sample was recorded.

[0034] The test measured the fluidity of the pure paste of the water reducing agent of each embodiment and the comparative example at the same dosage. The test was carried out in accordance with GB / T8077-2000 "Test method for homogeneity of concrete admixtures", the water reducing agent was adjusted to pH=6.90-7.10 with 30wt% sodium hydroxide solution, W / C=0.35, and the dosage was the solid dosage.

[0035] The test results are shown in Table 1:

[0036] Table 1: Results of the flow properties of the pure pulp

[0037]

[0038] The specific results in Table 1 above show that the solid content of the polycarboxylic acid water reducer (Examples 1 to 5) synthesized by the mechanochemical method of the present invention is >99wt%, which is significantly higher than the solid content of 39.73% of the polycarboxylic acid water reducer (Comparative Example) prepared by the aqueous solution polymerization method in the prior art. The reaction time of the polycarboxylic acid water reducer (Examples 1 to 5) synthesized by the mechanochemical method of the present invention is ≤90 minutes, which is significantly shorter than the reaction time of 255 minutes of the polycarboxylic acid water reducer (Comparative Example) prepared by the prior art, and the net slurry fluidity reaches the polycarboxylic acid water reducer prepared by the prior art, proving that the polycarboxylic acid water reducer of the present invention has very good practical value.

[0039] The preparation method of the polycarboxylic acid water reducer of the present invention has the advantages of simple process and reduced energy consumption, no organic solvent is added, low cost, high yield of the obtained polycarboxylic acid water reducer, and the product is easy to store and transport.

[0040] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be subject to the scope of protection of the claims.

Claims

1. A method for preparing a polycarboxylic acid water reducer, characterized in that: The following steps are involved: After reaching the set reaction temperature and rotation speed, the macromonomer isopentyl polyoxyethylene ether TPEG and the initiator ammonium persulfate APS are added into the mixing chamber according to the corresponding molar ratio, and after TPEG and APS are completely melted, half of the amount of acrylic acid AA, sodium methyl acrylate sulfonate MAS and ultrapure water required for the reaction are added; at this time, the mechanochemical free radical polymerization reaction begins, and when half of the required reaction time is reached, the remaining AA, MAS and ultrapure water are added to continue the mechanochemical free radical polymerization reaction; after the above reaction is completed, an inhibitor is added, and the obtained product is removed to obtain a polycarboxylic acid high-performance water reducer.

2. The preparation method according to claim 1, characterized in that The weight average molecular weight of the TPEG is 2400.

3. The preparation method according to claim 1, characterized in that The molar ratio of TPEG to AA to MAS is 1.0:2.5-3.0:0.08-0.

16.

4. The preparation method according to claim 1, characterized in that The amount of ultrapure water used is 0.7wt% of the mass of TPEG.

5. The preparation method according to claim 1, characterized in that The amount of APS used is 0.8-1.2wt% of the mass of TPEG.

6. The preparation method according to claim 1, characterized in that The reaction temperature is 60-70°C.

7. The preparation method according to claim 1, characterized in that The rotating speed is 65-75 R / min.

8. The preparation method according to claim 1, characterized in that The reaction time is 60 to 90 minutes.

9. The preparation method according to claim 1, characterized in that The dosage of the polymerization inhibitor is 0.03wt% of the mass of TPEG, and the polymerization inhibitor is selected from hydroquinone (HQ).

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