Anti-mud polycarboxylic acid high-performance water reducing agent and preparation method thereof

Abstract

The application belongs to the technical field of polymer polymer water reducing agent, and particularly relates to a kind of anti-mud polycarboxylic acid high-performance water reducing agent and its preparation method.The preparation method steps are as follows: D4H and polyether macromonomer are added to organic solvent according to the molar ratio of 1-1.5:1 to be mixed and dissolved, then organic tin catalyst is added to heat and stir to react, after the reaction is completed, the organic solvent and unreacted raw materials are removed by vacuum evaporation, to obtain anti-mud functional monomer;((Methyl) acrylate hydroxyalkyl ester monomer, anti-mud functional monomer and chain transfer agent are added to deionized water to be mixed and dissolved, then heated to 40-60 DEG C, drop the oxidation-reduction initiator and (methyl) acrylate monomer to initiate copolymerization reaction, after the reaction is completed, add alkali to neutralize, to obtain anti-mud polycarboxylic acid high-performance water reducing agent.The water reducing agent obtained by the application has significantly improved water reducing performance and anti-mud performance.

Description

Technical Field

[0001] This invention belongs to the field of polymer water-reducing agent technology, specifically relating to an anti-mud type polycarboxylate high-performance water-reducing agent and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizer is an environmentally friendly concrete admixture with a comb-like structure, prepared by copolymerizing acrylic monomers and polyether macromonomers. Its structural characteristics allow it to firmly adsorb onto the surface of cement particles, while its side chains extend into the water to form a spatial barrier. Its main mechanisms of action include: 1. Electrostatic repulsion: Anionic groups adsorb onto the positively charged surface of cement particles, forming an electric double layer. This causes the particles to carry the same charge, repelling each other, disrupting the flocculation structure, and releasing trapped water. 2. Steric hindrance: After adsorption, long side chains extend around the particles. When particles approach each other, the overlapping side chains generate repulsive forces, preventing aggregation. 3. Lubrication: The strongly polar hydrophilic groups in the superplasticizer allow the superplasticized adsorption film on the surface of cement particles to form a stable solvated water film with water molecules. This water film has excellent lubrication properties, effectively reducing the sliding resistance between cement particles. However, due to the introduction of highly hydrophilic polyether long side chains, the anti-mud properties of polycarboxylate superplasticizer are insufficient. The main reason is that the clay components in concrete strongly intercalate and adsorb onto the long side chains of highly flexible and free-form polyethers. This results in the water-reducing agent adsorbing more clay than cement particles, thus reducing its water-reducing performance. Generally, the longer the molecular chain of the polyether, the greater its steric hindrance effect. However, this also leads to higher flexibility and freedom, resulting in a greater intercalation and adsorption effect and poorer anti-mud properties. With the deterioration of aggregate resources in concrete raw materials and their higher clay content, the demand for anti-mud performance of polycarboxylate high-performance water-reducing agents is becoming increasingly urgent.

[0003] Patent document CN 115197413 A discloses an anti-mud functional monomer for polycarboxylate superplasticizers, which can be prepared by reacting polyethylene glycol, diol, catalyst, polymerization inhibitor, and unsaturated carboxylic acid under certain process conditions. Adding this monomer during the synthesis of the polycarboxylate superplasticizer mother liquor can effectively improve the anti-mud performance of the superplasticizer. The anti-mud principle lies in the fact that this anti-mud functional monomer contains a large number of ether bonds, which can preferentially adsorb into the clay interlayer, causing other superplasticizer molecules to adsorb onto the surface of cement particles, thus acting as a sacrificial agent. However, the amount of anti-mud sacrificial agent added needs to be precisely calculated and adjusted according to the clay content in the concrete to ensure the performance of the superplasticizer. This method fails to improve the anti-mud performance of the high-performance polycarboxylate superplasticizer from its structural aspects.

[0004] In the patent document CN 116333228 A, we proposed using a combination of unsaturated polyoxyethylene ether-grafted cyclosiloxane crosslinking agent and vinyl silane coupling agent comonomer to simultaneously improve the low-temperature crosslinking activity and dispersion and slump retention effect of polycarboxylate superplasticizer. However, no corresponding research was conducted on its anti-mud properties. The results showed that when using only unsaturated polyoxyethylene ether-grafted cyclosiloxane crosslinking agent, the water reduction rate and fluidity were reduced to a certain extent. This indicates that the introduction of a simple high-steric-hindrance crosslinking monomer reduced the anchoring effect of the superplasticizer molecules on cement particles and reduced the dispersion ability. Studies have shown that polycarboxylate superplasticizer containing siloxane (silane coupling agent) has a greater adsorption amount on cement than ordinary polycarboxylate superplasticizer. Siloxane weakens the adsorption of polycarboxylate superplasticizer on montmorillonite (Zhang Guanghua et al. Influence of siloxane functional monomers on the anti-mud properties of polycarboxylate superplasticizer [J]. Journal of Shaanxi University of Science and Technology, 2017, 35(6): 77-87), thus having a certain improvement effect on anti-mud properties. However, due to the strong intercalation adsorption of montmorillonite by the long side chains of hydrophilic polyether, the adsorption differences of silane coupling agent comonomers on cement and montmorillonite are relatively weak, and the resulting water-reducing agent has a limited effect on improving the mud resistance. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for preparing a mud-resistant polycarboxylate high-performance water-reducing agent.

[0006] Another objective of this invention is to provide a mud-resistant polycarboxylate high-performance water-reducing agent prepared by the above method.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a mud-resistant polycarboxylate superplasticizer includes the following steps:

[0009] (1) Tetramethylcyclotetrasiloxane (D4H) and polyether macromonomer were added to an organic solvent at a molar ratio of 1~1.5:1 and mixed and dissolved. Then an organotin catalyst was added and heated and stirred to react. After the reaction was completed, the organic solvent and unreacted raw materials were removed by vacuum evaporation to obtain the anti-mud functional monomer.

[0010] (2) Add (meth)acrylate hydroxyalkyl ester monomer, anti-mud functional monomer and chain transfer agent to deionized water to mix and dissolve, then heat to 40~60℃, add redox initiator and (meth)acrylate monomer dropwise to initiate copolymerization reaction, add alkali to neutralize after the reaction is completed to obtain anti-mud polycarboxylate high performance water-reducing agent.

[0011] In step (1) above, the molar ratio of D4H to polyether macromonomer needs to be controlled at 1~1.5:1 to ensure that D4H is in excess, prevent the formation of multifunctional crosslinking monomers, avoid the encapsulation of anion adsorption groups leading to a reduction in the anchoring ability of cement particles, and thus ensure the dispersion ability of cement particles. Excess D4H can be recovered by vacuum evaporation.

[0012] Further, the polyether macromonomers mentioned in steps (1) and (2) are one or more of allyl polyoxyethylene ether (APEG), methyl allyl polyoxyethylene ether (HPEG), isobutylene polyoxyethylene ether (SPEG), and isopentenyl polyoxyethylene ether (TPEG); the number average molecular weight of the polyether macromonomers is 1000~5000.

[0013] Further, the organic solvent mentioned in step (1) is any one or a mixture of several of acetone, butanone, N,N-dimethylformamide, and tetrahydrofuran.

[0014] Further, the organotin catalyst mentioned in step (1) is stannous isooctanoate, and the concentration of the organotin catalyst in the reaction system is 0.1%~1%; the temperature of the heating and stirring reaction is 50~80℃, and the reaction time is 2~6h. The reaction endpoint can be determined by measuring the amount of hydrogen released.

[0015] Further, the hydroxyalkyl methacrylate monomer mentioned in step (2) is one or more of hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), and hydroxybutyl acrylate (4-HBA). The hydroxyalkyl methacrylate monomer used in this invention contains polar hydroxyl groups that participate in solvation and has a certain steric hindrance effect, which can improve dispersion performance. Compared with conventional polyether macromonomers, it has a shorter chain length, lower flexibility and degree of freedom, and weaker intercalation adsorption effect, which can improve anti-mud properties.

[0016] Further, the molar ratio of the (meth)acrylate hydroxyalkyl ester monomer, the anti-mud functional monomer and the (meth)acrylate monomer in step (2) is 1~2:0.2~1:3~7.

[0017] Further, the chain transfer agent mentioned in step (2) is one of mercaptoacetic acid or mercaptopropionic acid.

[0018] Further, the redox initiator mentioned in step (2) is a combination of at least one oxidant selected from hydrogen peroxide, sodium peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate, and at least one reducing agent selected from ascorbic acid, sodium sulfite, and sodium bisulfite.

[0019] A mud-resistant polycarboxylate high-performance water-reducing agent is prepared by the above method.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The present invention uses rigid, high steric hindrance and high hydrophobicity cyclosiloxane to end-cap the free ends of polyether macromonomers, which can significantly reduce the intercalation adsorption of water-reducing agent molecules on clay particles, while not affecting the adsorption of water-reducing agent molecules on cement particles, thereby significantly improving the anti-mud performance.

[0022] (2) The hydrophilic polyether long chain contained in the anti-mud functional monomer used in this invention still maintains good solvation effect, and its steric hindrance effect is stronger after being treated with high steric hindrance cyclosiloxane end capping, thereby significantly improving water reduction performance. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0024] Example 1

[0025] A method for preparing a mud-resistant polycarboxylate superplasticizer includes the following steps:

[0026] (1) D4H and TPEG-2400 were added to methyl ethyl ketone solvent at a molar ratio of 1.2:1 and mixed and dissolved. Then, 0.5% stannous isooctanoate catalyst was added, and the mixture was heated to 60°C and stirred. The amount of hydrogen released during the reaction was monitored. After 4 hours of reaction, almost no hydrogen was produced, and the reaction was completed. Then, the methyl ethyl ketone solvent and unreacted D4H were removed by heating and vacuum distillation to obtain the anti-mud functional monomer.

[0027] (2) HEMA monomer, anti-mud functional monomer, and chain transfer agent mercaptoacetic acid were added to deionized water and mixed to dissolve. The mixture was then heated to 50°C, and hydrogen peroxide solution and ascorbic acid solution were added dropwise as initiators for 30 min. Then, methacrylic acid monomer was added dropwise and the reaction was continued at the specified temperature. The molar ratio of HEMA monomer, anti-mud functional monomer, and methacrylic acid monomer was 1.5:0.5:5. The dropwise addition time of the initiator and methacrylic acid monomer was controlled at 3 h. After the initiator and methacrylic acid monomer were added, the reaction was continued at the specified temperature for 2 h. After cooling to room temperature, sodium hydroxide solution was added to neutralize the mixture, thus obtaining an anti-mud polycarboxylate high-performance water-reducing agent.

[0028] Example 2

[0029] A method for preparing a mud-resistant polycarboxylate superplasticizer includes the following steps:

[0030] (1) D4H and HPEG-2400 were added to methyl ethyl ketone solvent at a molar ratio of 1.3:1 and mixed and dissolved. Then, 0.5% stannous isooctanoate catalyst was added, and the mixture was heated to 70°C and stirred. The amount of hydrogen released during the reaction was monitored. After 4 hours of reaction, almost no hydrogen was produced, and the reaction was completed. Then, the methyl ethyl ketone solvent and unreacted D4H were removed by heating and vacuum distillation to obtain the anti-mud functional monomer.

[0031] (2) HPMA monomer, anti-mud functional monomer, and chain transfer agent mercaptoacetic acid were added to deionized water and mixed to dissolve. The mixture was then heated to 60°C, and ammonium persulfate solution and sodium bisulfite solution were added dropwise as initiators for 30 min. Then, acrylic monomer was added dropwise and the reaction was continued at the specified temperature. The molar ratio of HPMA monomer, anti-mud functional monomer, and acrylic monomer was 2:0.2:6. The dropwise addition time of the initiator and acrylic monomer was controlled at 3 h. After the initiator and acrylic monomer were added, the reaction was continued at the specified temperature for 2 h. After cooling to room temperature, sodium hydroxide solution was added to neutralize the mixture, thus obtaining an anti-mud polycarboxylate high-performance water-reducing agent.

[0032] Example 3

[0033] A method for preparing a mud-resistant polycarboxylate superplasticizer includes the following steps:

[0034] (1) D4H and SPEG-2400 were added to methyl ethyl ketone solvent at a molar ratio of 1.4:1 and mixed and dissolved. Then, 0.8% stannous isooctanoate catalyst was added, and the mixture was heated to 50°C and stirred. The amount of hydrogen released during the reaction was monitored. After 5 hours of reaction, almost no hydrogen was produced, and the reaction was completed. Then, the methyl ethyl ketone solvent and unreacted D4H were removed by heating and vacuum distillation to obtain the anti-mud functional monomer.

[0035] (2) 4-HBA monomer, anti-mud functional monomer, and chain transfer agent mercaptoacetic acid were added to deionized water and mixed to dissolve. The mixture was then heated to 55°C, and potassium persulfate solution and sodium sulfite solution were added dropwise as initiators for 30 min. Then, methacrylic acid monomer was added dropwise and the reaction was continued at the specified temperature. The molar ratio of 4-HBA monomer, anti-mud functional monomer, and methacrylic acid monomer was 1:1:7. The dropwise addition time of the initiator and methacrylic acid monomer was controlled at 3 h. After the initiator and methacrylic acid monomer were added, the reaction was continued at the specified temperature for 2 h. After cooling to room temperature, sodium hydroxide solution was added for neutralization to obtain anti-mud polycarboxylate high-performance water-reducing agent.

[0036] Example 4

[0037] A method for preparing a mud-resistant polycarboxylate superplasticizer includes the following steps:

[0038] (1) D4H and APEG-1200 were added to methyl ethyl ketone solvent at a molar ratio of 1.5:1 and mixed and dissolved. Then, 0.5% stannous isooctanoate catalyst was added, and the mixture was heated to 70°C and stirred. The amount of hydrogen released during the reaction was monitored. After 4 hours of reaction, almost no hydrogen was produced, and the reaction was completed. Then, the methyl ethyl ketone solvent and unreacted D4H were removed by heating and vacuum distillation to obtain the anti-mud functional monomer.

[0039] (2) HEMA monomer, anti-mud functional monomer, and chain transfer agent mercaptoacetic acid were added to deionized water and mixed to dissolve. The mixture was then heated to 50°C, and hydrogen peroxide solution and ascorbic acid solution were added dropwise as initiators for 30 min. Then, methacrylic acid monomer was added dropwise and the reaction was continued at the specified temperature. The molar ratio of HEMA monomer, anti-mud functional monomer, and methacrylic acid monomer was 1.6:0.4:4. The dropwise addition time of the initiator and methacrylic acid monomer was controlled at 3 h. After the initiator and methacrylic acid monomer were added, the reaction was continued at the specified temperature for 2 h. After cooling to room temperature, sodium hydroxide solution was added to neutralize the mixture, thus obtaining an anti-mud polycarboxylate high-performance water-reducing agent.

[0040] Comparative Example 1

[0041] A method for preparing a polycarboxylate high-performance water-reducing agent includes the following steps:

[0042] HEMA monomer, TPEG-2400, and chain transfer agent mercaptoacetic acid were dissolved in deionized water. The mixture was then heated to 50°C, and hydrogen peroxide solution and ascorbic acid solution were added dropwise as initiators for 30 minutes. Methacrylate monomer was then added dropwise, and the reaction was continued at this temperature. The molar ratio of HEMA monomer, TPEG-2400, and methacrylate monomer was 1.5:0.5:5. The dropwise addition time of both the initiator and methacrylate monomer was controlled at 3 hours. After the addition of the initiator and methacrylate monomer was completed, the reaction was continued at this temperature for 2 hours. After cooling to room temperature, sodium hydroxide solution was added for neutralization, yielding a high-performance polycarboxylate superplasticizer.

[0043] Comparative Example 2

[0044] A method for preparing a mud-resistant polycarboxylate high-performance water-reducing agent, compared with Example 1, in step (1) the preparation of the mud-resistant functional monomer, the molar ratio of D4H to TPEG-2400 is adjusted to 1:2, and the rest are the same.

[0045] The water reduction rate, initial fluidity, fluidity over time, and slump loss over 1 hour of the water-reducing agents obtained in the above examples and comparative examples were tested:

[0046] The test method refers to GB / 8076-2008 standard. The cement used in the experiment is P.O42.5 standard cement and P.O42.5 standard cement with 2wt% montmorillonite (mud-containing cement). The water-reducing agent dosage is 0.25%.

[0047] The corresponding test results are shown in Table 1 below.

[0048] Table 1. Performance test results of water-reducing agents in Examples 1-4 and Comparative Examples 1-2

[0049]

[0050] The results of Examples 1-4 in Table 1 show that the water-reducing agent of the present invention exhibits good water-reducing performance and high anti-mud properties in both standard cement and mud-containing cement. A comparison between Comparative Example 1 and Example 1 shows that the end-capping treatment of the free ends of the polyether macromonomer using cyclosiloxane in the present invention significantly improves the anti-mud properties of the obtained water-reducing agent and also significantly enhances its water-reducing performance. A comparison between Comparative Example 2 and Example 1 shows that when the molar ratio of D4H to the polyether macromonomer is less than 1:1, the water-reducing performance of the obtained water-reducing agent is significantly reduced. This is because the reaction generates a polyene-structured crosslinking monomer. After copolymerization and crosslinking, the anchoring effect of the water-reducing agent on cement particles is reduced, and the solvation process of the polyether chain is severely restricted. The electrostatic repulsion and lubrication effects of the water-reducing agent cannot be effectively utilized, leading to a decrease in water-reducing performance.

[0051] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a mud-resistant polycarboxylate superplasticizer, characterized in that... Includes the following steps: (1) Tetramethylcyclotetrasiloxane and polyether macromonomer are added to an organic solvent at a molar ratio of 1~1.5:1 and mixed and dissolved. Then an organotin catalyst is added and heated and stirred to react. After the reaction is completed, the organic solvent and unreacted raw materials are removed by vacuum evaporation to obtain the anti-mud functional monomer. (2) Add (meth)acrylate hydroxyalkyl ester monomer, anti-mud functional monomer and chain transfer agent to deionized water to mix and dissolve, then heat to 40~60℃, add redox initiator and (meth)acrylate monomer dropwise to initiate copolymerization reaction, add alkali to neutralize after the reaction is completed to obtain anti-mud polycarboxylate high performance water-reducing agent.

2. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The polyether macromonomers mentioned in steps (1) and (2) are one or more of allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, isobutylene polyoxyethylene ether, and isopentenyl polyoxyethylene ether; the number average molecular weight of the polyether macromonomers is 1000~5000.

3. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The organic solvent mentioned in step (1) is any one or a mixture of several of the following: acetone, butanone, N,N-dimethylformamide, and tetrahydrofuran.

4. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The organotin catalyst mentioned in step (1) is stannous isooctanoate, and the concentration of the organotin catalyst in the reaction system is 0.1%~1%.

5. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 4, characterized in that: The heating and stirring reaction is carried out at a temperature of 50-80°C for 2-6 hours.

6. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The hydroxyalkyl methacrylate monomer mentioned in step (2) is one or more of hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

7. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The molar ratio of (meth)acrylate hydroxyalkyl ester monomer, anti-mud functional monomer and (meth)acrylate monomer in step (2) is 1~2:0.2~1:3~7.

8. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The chain transfer agent mentioned in step (2) is one of mercaptoacetic acid or mercaptopropionic acid.

9. The preparation method of the anti-mud type polycarboxylate high-performance water-reducing agent according to claim 1, characterized in that: The redox initiator mentioned in step (2) is a combination of at least one oxidant selected from hydrogen peroxide, sodium peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate, and at least one reducing agent selected from ascorbic acid, sodium sulfite, and sodium bisulfite.

10. A high-performance polycarboxylate superplasticizer with anti-mud properties, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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