High-adaptability polycarboxylic acid water reducing agent and preparation method thereof

Abstract

The present application relates to the field of concrete admixtures, in particular to a high-adaptability polycarboxylate superplasticizer and a preparation method thereof.The high-adaptability polycarboxylate superplasticizer and the preparation method thereof have the following advantages: by adding a functional monomer and a crosslinking agent in a raw material formula, the functional monomer with a rigid benzene ring and intramolecular hydrogen bonds is introduced into the molecular structure of the polycarboxylate superplasticizer, so that the molecular rigidity is improved; further, the polycarboxylate superplasticizer has a crosslinked molecular structure by the action of the crosslinking agent, so that the molecular rigidity of the polycarboxylate superplasticizer is simultaneously strengthened in the intramolecular structure and the intermolecular structure; when the polycarboxylate superplasticizer is applied to a concrete mixture, the adaptability to cement is significantly improved, and the polycarboxylate superplasticizer has the effects of low dosage, high water-reducing rate, small slump loss, good sulfate resistance and the like.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and particularly to a highly adaptable polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers possess excellent water-reducing and dispersing properties, enabling fresh concrete with low water-cement ratios to maintain fluidity even at low dosages. They are an important component of high-strength and high-flowability concrete admixtures. However, both theoretical research and engineering applications indicate incompatibility between polycarboxylate superplasticizers and concrete components. In some cases, polycarboxylate superplasticizers may exhibit poor dispersion and rapid slump loss in concrete. This is primarily due to the unavoidable interaction with sulfates when used in concrete engineering: firstly, cement and admixtures in concrete contain sulfates; secondly, other concrete admixtures such as expansion agents and accelerators often contain sulfates. Ordinary polycarboxylate superplasticizer molecules tend to shrink and form coiled conformations in the presence of sulfates, making adsorption on cement particles difficult and thus affecting the dispersion and slump retention properties of the polycarboxylate superplasticizer.

[0003] Based on the aforementioned problem of incompatibility between polycarboxylate superplasticizers and sulfates, those skilled in the art have explored various approaches. Chinese Patent CN104311761A, published on January 28, 2015, discloses a comb-shaped polyether block polyacrylic acid copolymer and its preparation method. A comb-shaped polyether block polyacrylic acid copolymer dispersant was prepared using a reversible addition-fragmentation chain transfer polymerization method and applied to the dispersion of cement systems. However, this copolymer dispersant has a simple composition, a single structure, and few adjustable factors in solution conformation. Therefore, this dispersant has poor adaptability to cement, especially its resistance to sulfates is extremely poor. Chinese Patent CN105713150A, published on June 29, 2016, discloses a method for preparing a sulfate-resistant polycarboxylate superplasticizer and its application. Through reversible addition-fragmentation chain transfer polymerization, a strong adsorption group—phosphate group—is introduced into the main chain structure of the block polycarboxylate with a well-defined sequence structure, making the adsorption capacity of the block polycarboxylate stronger and thus improving its resistance to sulfates. However, this synthesis method is complex and difficult to control, making industrial production impossible. It is evident that how to prepare a sulfate-resistant and adaptable polycarboxylate superplasticizer remains a technical challenge that urgently needs to be addressed by those skilled in the art. Summary of the Invention

[0004] To address the technical problem of how to prepare a sulfate-resistant and adaptable polycarboxylate superplasticizer, this invention provides a method for preparing a highly adaptable polycarboxylate superplasticizer, comprising the following steps:

[0005] S100. By weight, add the vinyl polyether macromonomer, functional monomer, crosslinking agent, oxidant, alcohol solvent and water into the reactor and stir to react.

[0006] S101. The reducing agent aqueous solution, the unsaturated carboxylic acid aqueous solution and the chain transfer agent aqueous solution are simultaneously added to the reaction vessel to carry out the reaction;

[0007] S102, heat preservation, to obtain copolymer product;

[0008] S103, adjust the pH to 6-7 to obtain the highly adaptable polycarboxylate superplasticizer;

[0009] The weight ratio of the vinyl polyether macromonomer to the functional monomer is 1~4:6~10;

[0010] The structural formula of the functional unit is as follows:

[0011]

[0012] Wherein, R1 is -OCH3 or -OCH2CH=CH2, R2 is -H or -CH2CH=CH2, and R3 is -H or -CH2CH=CH2 or -CH=CH-CH3;

[0013] Preferably, the vinyl polyether macromonomer can be ethylene glycol monovinyl polyethylene glycol ether or 4-hydroxybutyl vinyl polyethylene glycol ether.

[0014] In one embodiment, the allocation ratio of each group is as follows, based on weight parts:

[0015] 60-100 parts of vinyl polyether macromonomer

[0016] 10-40 parts of functional monomer

[0017] 5-10 parts of crosslinking agent

[0018] 1-2 parts of oxidant

[0019] 10-30 parts of alcohol solvent

[0020] 50-100 parts water

[0021] 30.4~30.9 parts of reducing agent aqueous solution

[0022] 40-50 parts of unsaturated carboxylic acid aqueous solution

[0023] 30.3-34 parts of chain transfer agent aqueous solution.

[0024] In one embodiment, the reaction temperature and the holding temperature are both 20~30℃, and the holding time is 1~3 h; the reducing agent aqueous solution, the unsaturated carboxylic acid aqueous solution and the chain transfer agent aqueous solution are added to the reaction vessel at a uniform rate, and the adding time is 3~4 h.

[0025] In one embodiment, the vinyl polyether macromonomer has a molecular weight of 5000-6000.

[0026] In one embodiment, the crosslinking agent is any one or more of diallyl dimethylsilane, 1,4-pentadien-3-ol, and trimethylolpropane diallyl ether.

[0027] In one embodiment, the reducing agent aqueous solution is prepared by dissolving 0.4 to 0.9 parts by weight of reducing agent in 30 parts by weight of water; the unsaturated carboxylic acid aqueous solution is prepared by dissolving 10 to 20 parts by weight of unsaturated carboxylic acid in 30 parts by weight of water; and the chain transfer agent aqueous solution is prepared by dissolving 0.3 to 1.0 parts by weight of chain transfer agent in 30 parts by weight of water.

[0028] Furthermore, the reducing agent is any one or more of bisulfite, sulfite, sodium formaldehyde sulfoxylate, and vitamin C.

[0029] Furthermore, the unsaturated carboxylic acid is any one or more of acrylic acid, methacrylic acid, and itaconic acid.

[0030] Furthermore, the chain transfer agent is any one or more of mercaptoethanol, mercaptoacetic acid, mercaptopropionic acid, n-dodecyl mercaptoethanol, and tert-dodecyl mercaptoethanol.

[0031] The present invention also provides a highly adaptable polycarboxylate superplasticizer, which is prepared by the method described above for preparing a highly adaptable polycarboxylate superplasticizer.

[0032] Compared with existing technologies, the highly adaptable polycarboxylate superplasticizer and its preparation method provided by this invention, through the addition of functional monomers and crosslinking agents to the raw material formulation, wherein the functional monomers have rigid benzene rings and intramolecular hydrogen bonds, which, when introduced into the molecular structure of the polycarboxylate superplasticizer, can increase molecular rigidity. Furthermore, the introduction of the crosslinking agent gives the polycarboxylate superplasticizer a crosslinked molecular structure. This three-way synergy strengthens the molecular rigidity of the polycarboxylate superplasticizer in both intramolecular and intermolecular structures, making the polycarboxylate superplasticizer molecular configuration less prone to shrinkage and less likely to form a coiled conformation in the presence of sulfate in concrete systems. Consequently, sulfate does not affect the adsorption of polycarboxylate superplasticizer on cement particles. Therefore, the prepared highly adaptable polycarboxylate superplasticizer, when applied to concrete mixtures, significantly improves cement adaptability, and exhibits low dosage, high water reduction rate, small slump loss, and good sulfate resistance. In addition, the process is simple and possesses the characteristics and advantages of industrial production, solving the technical problem of how to prepare a sulfate-resistant and highly adaptable polycarboxylate superplasticizer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention provides the following Examples 1-3 for the preparation of a highly adaptable polycarboxylate superplasticizer:

[0035] Example 1

[0036] 85 g of ethylene glycol monovinyl polyethylene glycol ether, 30 g of 2-methoxy-4-vinylphenol, 5 g of diallyl dimethylsilane, 2 g of hydrogen peroxide, 15 g of ethanol and 50 g of water were added to a reaction vessel and stirred to react at a temperature of 20°C.

[0037] 30.6 g of vitamin C aqueous solution, 43 g of acrylic acid aqueous solution and 30.4 g of mercaptoacetic acid aqueous solution were added dropwise to the reaction vessel at a constant rate and the reaction was carried out over a period of 3 h.

[0038] After the addition was completed, the temperature was kept at 20℃ for 1 hour to obtain the copolymer.

[0039] After the insulation is completed, adjust the pH to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate superplasticizer.

[0040] In this embodiment, preferably, the molecular weight of the ethylene glycol monovinyl polyethylene glycol ether is 5000.

[0041] In this embodiment, preferably, the vitamin C aqueous solution is prepared by dissolving 0.6 g of vitamin C in 30 parts of water.

[0042] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 13 g of acrylic acid in 30 parts of water.

[0043] In this embodiment, preferably, the aqueous solution of mercaptoacetic acid is prepared by dissolving 0.4 g of mercaptoacetic acid in 30 parts of water.

[0044] Example 2

[0045] Add 90 g of 4-hydroxybutylvinyl polyethylene glycol ether, 20 g of eugenol, 7 g of 1,4-pentadien-3-ol, 1.2 g of hydrogen peroxide, 25 g of ethanol and 60 g of water to a reaction vessel, stir and react at a reaction temperature of 25°C.

[0046] 30.7 g of sodium formaldehyde sulfoxylate aqueous solution, 47 g of acrylic acid aqueous solution and 30.6 g of mercaptopropionic acid aqueous solution were added dropwise to the reaction vessel at a constant rate and the reaction was carried out over a period of 3 h.

[0047] After the addition was completed, the temperature was kept at 25℃ for 1 hour to obtain the copolymer product.

[0048] After the insulation is completed, adjust the pH to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate superplasticizer.

[0049] In this embodiment, preferably, the 4-hydroxybutylvinyl polyethylene glycol ether has a molecular weight of 6000.

[0050] In this embodiment, preferably, the sodium formaldehyde sulfoxylate aqueous solution is prepared by dissolving 0.7 g of sodium formaldehyde sulfoxylate in 30 parts of water.

[0051] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 17 g of acrylic acid in 30 parts of water.

[0052] In this embodiment, preferably, the mercaptopropionic acid aqueous solution is prepared by dissolving 0.6 g of mercaptopropionic acid in 30 parts of water.

[0053] Example 3

[0054] Add 85 g of ethylene glycol monovinyl polyethylene glycol ether, 15 g of 2-(allyloxy)phenol, 8 g of trimethylolpropane diallyl ether, 1.4 g of hydrogen peroxide, 20 g of ethanol and 70 g of water to a reaction vessel, stir and react at a reaction temperature of 30°C.

[0055] 30.9 g of vitamin C aqueous solution, 48 g of acrylic acid aqueous solution and 30.5 g of mercaptoacetic acid aqueous solution were added dropwise to the reaction vessel at a constant rate and the reaction was carried out over a period of 3 hours.

[0056] After the addition was completed, the temperature was kept at 30℃ for 1 hour to obtain the copolymer.

[0057] After the insulation is completed, adjust the pH to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate superplasticizer.

[0058] In this embodiment, preferably, the molecular weight of the ethylene glycol monovinyl polyethylene glycol ether is 6000.

[0059] In this embodiment, preferably, the vitamin C aqueous solution is prepared by dissolving 0.9 g of vitamin C in 30 parts of water.

[0060] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 18 g of acrylic acid in 30 parts of water.

[0061] In this embodiment, preferably, the aqueous solution of mercaptoacetic acid is prepared by dissolving 0.5 g of mercaptoacetic acid in 30 parts of water.

[0062] This invention also provides the following comparative examples 1-4 for preparing a polycarboxylate superplasticizer:

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that no crosslinking agent is added, that is, no 5 g of diallyl dimethylsilane as described in Example 1 is added; other components, ratios, operating steps and process parameters are consistent with those of Example 1 of the present invention.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that no functional monomer is added, that is, no 30 g of 2-methoxy-4-vinylphenol as described in Example 1 is added; other components, proportions, operating steps and process parameters are consistent with those of Example 1 of this invention.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 is that no functional monomers and crosslinking agents are added, that is, no 30 g of 2-methoxy-4-vinylphenol and 5 g of diallyl dimethylsilane are added as described in Example 1; other components, ratios, operating steps and process parameters are consistent with those of Example 1 of this invention.

[0069] Comparative Example 4

[0070] The difference between this comparative example and Example 1 is that the functional monomer is replaced with 2-allylphenol, which does not contain intramolecular hydrogen bonds in its molecular structure; the other components, ratios, operating steps and process parameters are consistent with those of Example 1 of this invention.

[0071] The conformational analysis and concrete mixture performance tests were conducted on the highly adaptable polycarboxylate superplasticizers prepared in Examples 1-3 and the polycarboxylate superplasticizers prepared in Comparative Examples 1-4.

[0072] Performance Test 1: Conformation Determination of Polycarboxylate Superplasticizer Solution

[0073] The solution conformation of the polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-4 was determined using a Malvern Panaco Viscotek 270 dynamic and static light scattering instrument; wherein, the SO4 content in the solution was adjusted with Na2SO4. 2- Concentration: polymer concentration was 1 mg / mL, test angle was 90°; solution conformation determination results are listed in Table 1.

[0074] Table 1. Conformation determination results of polycarboxylate superplasticizer solutions prepared in Examples 1-3 and Comparative Examples 1-4

[0075]

[0076] According to the data in Table 1, the hydrodynamic radius of the polycarboxylate superplasticizer solution decreased after the addition of sulfate solution. The hydrodynamic radius of the polycarboxylate superplasticizer solution prepared in Comparative Example 3 decreased significantly, with the reduction level at sulfate concentrations of 20 mmol / L and 80 mmol / L being around 1 nm and 2 nm, respectively. Its molecular structure was in a coiled state, and the conformation underwent obvious shrinkage. The reduction in the hydrodynamic radius of the polycarboxylate superplasticizer solutions prepared in Comparative Examples 1, 2, and 4 was less than that in Comparative Example 3. The reduction level at sulfate concentrations of 2 was around 0.4 nm and 0.8 nm, respectively. It can be seen that simply introducing functional monomers or crosslinking agents with benzene rings and intramolecular hydrogen bonds into polycarboxylate superplasticizer can enhance molecular rigidity to a certain extent and inhibit the conformational coiling phenomenon under the action of sulfate.

[0077] The reduction in hydrodynamic radius of the highly adaptable polycarboxylate superplasticizer solutions prepared in Examples 1-3 was significantly less than that in Comparative Examples 1-4. The reduction in hydrodynamic radius at the second-level sulfate concentration was only around 0.15 nm and 0.35 nm. It can be seen that the present invention simultaneously introduces benzene rings, intramolecular hydrogen bonds, and crosslinking agents into the polycarboxylate superplasticizer. The closed cyclic structure of the benzene ring restricts the flexibility of the polycarboxylate superplasticizer molecule and improves the molecular rigidity. The special intramolecular hydrogen bonds further improve the molecular rigidity of the polycarboxylate superplasticizer, while the introduction of the crosslinking agent gives the polycarboxylate superplasticizer a crosslinked molecular structure. The three-way synergy and superimposed benefits make the highly adaptable polycarboxylate superplasticizer molecular configuration provided by the present invention less prone to shrinkage and less likely to form a coiled conformation in the presence of sulfate.

[0078] Performance Test 2: Performance Test of Concrete Mixture

[0079] The highly adaptable polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-4 of this invention were adjusted to a concentration of 50% by adding appropriate amounts of water. The concrete mix performance was then tested according to GB / T 50080-2016, the standard for test methods of performance of ordinary concrete mixtures. The concrete mix proportion was: cement 360 kg / m³. 3 790kg / m³ of manufactured sand 3 1060 kg / m³ of gravel 3 162 kg / m³ of water 3 Na2SO4 was added to the water to adjust the SO4 content in the concrete. 2- Concentration; test results are listed in Table 2.

[0080] Table 2. Test results of the effects of polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-4 on concrete performance.

[0081]

[0082] According to the data in Table 2, when the polycarboxylate superplasticizer prepared in Comparative Example 3 was applied to concrete, the initial dispersion and slump retention properties of the concrete decreased significantly when sulfate was added to the concrete water, indicating a clear incompatibility with sulfate. When the polycarboxylate superplasticizers prepared in Comparative Examples 1, 2, and 4 were applied to concrete, the initial dispersion and slump retention properties of the concrete decreased when sulfate was added to the concrete water, but the degree of decrease was less than that in Comparative Example 3. In contrast, the highly adaptable polycarboxylate superplasticizers prepared in Examples 1-3, when applied to concrete, exhibited good initial dispersion and slump retention properties in concrete with different sulfate contents after the addition of sulfate to the concrete water, demonstrating good adaptability to sulfate. This is mainly because the hydrodynamic radius of the polycarboxylate superplasticizers prepared in Comparative Examples 1-4 significantly decreased in the presence of sulfate in the concrete system, and the molecular structure became coiled, resulting in conformational shrinkage. This made adsorption on cement particles difficult, affecting the dispersion and slump retention properties of the concrete. This invention, by adding functional monomers and crosslinking agents, directly integrates the rigid benzene rings and intramolecular hydrogen bonds in the functional monomers into the molecular structure of polycarboxylate superplasticizers, synergistically improving their molecular rigidity. Furthermore, the crosslinking agent enables the polycarboxylate superplasticizer to possess a crosslinked molecular structure, simultaneously strengthening the molecular rigidity of the polycarboxylate superplasticizer from both intramolecular and intermolecular structures. At the molecular conformation level, it mitigates the conformational curling phenomenon under the action of sulfate. When applied to concrete mixtures, it improves cement compatibility, reduces incompatibility, exhibits better adsorption on cement particles, and demonstrates superior water-reducing, dispersing, and slump-retaining properties.

[0083] In summary, the highly adaptable polycarboxylate superplasticizer prepared by this invention has advantages such as good cement adaptability, good slump retention, low dosage, high water reduction rate, and good sulfate resistance.

[0084] Although this document uses terms such as cement adaptability, sulfate resistance, conformational coiling, and molecular rigidity extensively, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly adaptable polycarboxylate superplasticizer, characterized in that, Includes the following steps: S100. By weight, add the vinyl polyether macromonomer, functional monomer, crosslinking agent, oxidant, alcohol solvent and water into the reactor and stir to react. S101. The reducing agent aqueous solution, the unsaturated carboxylic acid aqueous solution, and the chain transfer agent aqueous solution are added to the reaction vessel separately and simultaneously to carry out the reaction. S102, heat preservation, to obtain copolymer product; S103, adjust the pH to 6-7 to obtain the highly adaptable polycarboxylate superplasticizer; The weight ratio of the vinyl polyether macromonomer to the functional monomer is 1~4:6~10; The structural formula of the functional unit is as follows: Wherein, R1 is -OCH3, R2 is -H, and R3 is -CH=CH2; Or R1 is -OCH3, R2 is -H, and R3 is -CH2CH=CH2; Or R1 is -OCH3CH=CH2, R2 is -H, and R3 is -H; The crosslinking agent is any one or any combination of diallyl dimethylsilane, 1,4-pentadien-3-ol, and trimethylolpropane diallyl ether.

2. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 1, characterized in that, The distribution ratios for each group, based on weight parts, are as follows: 60-100 parts of vinyl polyether macromonomer 10-40 parts of functional monomer 5-10 parts of crosslinking agent 1-2 parts of oxidant 10-30 parts of alcohol solvent 50-100 parts water 30.4~30.9 parts of reducing agent aqueous solution 40-50 parts of unsaturated carboxylic acid aqueous solution 30.3-34 parts of chain transfer agent aqueous solution.

3. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 1, characterized in that: The reaction temperature and the holding temperature are both 20~30℃, and the holding time is 1~3 h; The reducing agent aqueous solution, the unsaturated carboxylic acid aqueous solution, and the chain transfer agent aqueous solution are added to the reaction vessel at a uniform rate for 3-4 hours.

4. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 1, characterized in that: The vinyl polyether macromonomer has a molecular weight of 5000~6000.

5. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 1, characterized in that: The reducing agent aqueous solution is prepared by dissolving 0.4 to 0.9 parts by weight of the reducing agent in 30 parts by weight of water; The unsaturated carboxylic acid aqueous solution is prepared by dissolving 10-20 parts by weight of unsaturated carboxylic acid in 30 parts by weight of water; The chain transfer agent aqueous solution is prepared by dissolving 0.3 to 1.0 parts by weight of chain transfer agent in 30 parts by weight of water.

6. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 5, characterized in that: The reducing agent is any one or more of bisulfite, sulfite, sodium formaldehyde sulfoxylate, and vitamin C.

7. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 5, characterized in that: The unsaturated carboxylic acid is any one or more of acrylic acid, methacrylic acid, and itaconic acid.

8. The preparation method of the highly adaptable polycarboxylate superplasticizer according to claim 5, characterized in that: The chain transfer agent is any one or more of mercaptoethanol, mercaptoacetic acid, mercaptopropionic acid, n-dodecyl mercaptoethanol, and tert-dodecyl mercaptoethanol.

9. A highly adaptable polycarboxylate superplasticizer, characterized in that: It is prepared by the method of preparing the highly adaptable polycarboxylate superplasticizer according to any one of claims 1 to 8.

Images