High-adaptability polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the field of concrete admixtures, in particular to a high-adaptability polycarboxylate superplasticizer and a preparation method thereof. According to the high-adaptability polycarboxylate superplasticizer and the preparation method thereof provided by the invention, the functional monomer and the cross-linking agent are added into the raw material formula, and the functional monomer with a rigid benzene ring and an intramolecular hydrogen bond is introduced into the molecular structure of the polycarboxylate superplasticizer, so that the molecular rigidity of the polycarboxylate superplasticizer is synergistically improved; the polycarboxylate superplasticizer has a cross-linked molecular structure under the action of the cross-linking agent, the molecular rigidity of the polycarboxylate superplasticizer is enhanced by integrating an intramolecular structure and an intermolecular structure, the polycarboxylate superplasticizer is applied to a concrete mixture, the adaptability to cement is remarkably improved, and the polycarboxylate superplasticizer has the effects of low mixing amount, high water-reducing rate, small slump loss, good sulfate tolerance and the like.

Description

Technical Field

[0001] The invention relates to the field of concrete admixtures, and in particular to a highly adaptable polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] Polycarboxylate water-reducing agent has excellent water-reducing and dispersing properties. It can keep the fresh concrete with low water-binder ratio fluid at a low dosage. It is an important component of high-strength and high-fluidity concrete admixtures. However, both theoretical research and engineering applications have shown that polycarboxylate water-reducing agent is incompatible with concrete components. In some cases, polycarboxylate water-reducing agent will have poor dispersion effect and rapid concrete slump loss. This is mainly because polycarboxylate water-reducing agent cannot avoid the effect of sulfate when used in concrete engineering: on the one hand, cement and admixtures in concrete contain sulfate; on the other hand, other concrete admixtures such as expansion agents and early strength agents often contain sulfate. Ordinary polycarboxylate water-reducing agent molecules tend to shrink and form a curled conformation in the presence of sulfate, making it difficult to adsorb on cement particles, thereby affecting the dispersion and slump retention performance of polycarboxylate water-reducing agent.

[0003] Based on the problem of the incompatibility of the above-mentioned polycarboxylate water-reducing agent with sulfate, those skilled in the art have explored. Chinese patent CN104311761A disclosed a comb-shaped polyether block polyacrylic acid copolymer and its preparation method on January 28, 2015, and prepared a comb-shaped polyether block polyacrylic acid copolymer dispersant by reversible addition-fragmentation chain transfer polymerization and applied to the dispersion of cement system, but the copolymer dispersant has a simple composition, a single structure, and fewer adjustable factors of solution conformation, so the dispersant has poor adaptability to cement, and especially has extremely poor resistance to sulfate. Chinese patent CN105713150A disclosed a preparation method and application of a sulfate-resistant polycarboxylate water-reducing agent on June 29, 2016, and introduced a strong adsorption group-phosphate group on the block polycarboxylic acid main chain structure with clear sequence structure distribution through reversible addition-fragmentation chain transfer polymerization, so that the adsorption capacity of the block polycarboxylic acid is stronger, thereby improving its resistance to sulfate, but the synthesis method is complex and difficult to control, and industrial production cannot be achieved. It can be seen that how to prepare a polycarboxylate water reducer that is resistant to sulfate and has good adaptability is still a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0004] In order to solve the technical problem of how to prepare a polycarboxylate water-reducing agent that is resistant to sulfate and has good adaptability, the present invention provides a method for preparing a polycarboxylate water-reducing agent with high adaptability, comprising the following steps: S100, adding vinyl polyether macromonomer, functional monomer, crosslinking agent, oxidant, alcohol solvent and water into a reaction kettle by weight, and stirring for reaction; S101, adding a reducing agent aqueous solution, an unsaturated carboxylic acid aqueous solution and a chain transfer agent aqueous solution into a reactor simultaneously for reaction; S102, heat preservation, to obtain a copolymer product; S103, adjusting the pH to 6-7 to obtain a highly adaptable polycarboxylate water-reducing agent; The weight ratio of the vinyl polyether macromonomer to the functional monomer is 1-4:6-10; The functional monomer structural formula is as follows:

[0005] Wherein, R1 is -OCH3 or -OCH2CH=CH2, R2 is -H or -CH2CH=CH2, R3 is -H or -CH2CH=CH2 or -CH=CH-CH3; Preferably, the vinyl polyether macromonomer may be ethylene glycol monovinyl polyethylene glycol ether or 4-hydroxybutyl vinyl polyethylene glycol ether.

[0006] In one embodiment, the distribution ratio of each group is as follows according to weight parts: Vinyl polyether macromonomer 60~100 parts Functional monomer 10~40 parts Cross-linking agent 5~10 parts 1~2 parts of oxidant Alcohol solvent 10~30 parts 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.

[0007] In one embodiment, the reaction temperature and the insulation temperature are both 20-30° C., and the insulation 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 reactor in a uniform dropwise manner for 3-4 h.

[0008] In one embodiment, the molecular weight of the vinyl polyether macromonomer is 5000-6000.

[0009] In one embodiment, the cross-linking agent is any one or any combination of diallyldimethylsilane, 1,4-pentadien-3-ol and trimethylolpropane diallyl ether.

[0010] In one embodiment, the reducing agent aqueous solution is prepared by dissolving 0.4-0.9 parts by weight of the reducing agent in 30 parts of water; the unsaturated carboxylic acid aqueous solution is prepared by dissolving 10-20 parts by weight of the unsaturated carboxylic acid in 30 parts of water; and the chain transfer agent aqueous solution is prepared by dissolving 0.3-1.0 parts by weight of the chain transfer agent in 30 parts of water.

[0011] Furthermore, the reducing agent is any one or any combination of bisulfite, sulfite, sodium formaldehyde sulfoxylate and vitamin C.

[0012] Furthermore, the unsaturated carboxylic acid is any one or any combination of acrylic acid, methacrylic acid and itaconic acid.

[0013] Furthermore, the chain transfer agent is any one or any combination of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, n-dodecyl mercaptan and tert-dodecyl mercaptan.

[0014] The present invention also provides a highly adaptable polycarboxylate water-reducing agent, which is prepared by the above-mentioned preparation method of the highly adaptable polycarboxylate water-reducing agent.

[0015] Compared with the prior art, the highly adaptable polycarboxylate water-reducing agent and its preparation method provided by the present invention are added with functional monomers and cross-linking agents in the raw material formula, wherein the functional monomers have rigid benzene rings and intramolecular hydrogen bonds, and are introduced into the molecular structure of the polycarboxylate water-reducing agent to increase the molecular rigidity. Further, the introduction of the cross-linking agent enables the polycarboxylate water-reducing agent to have a cross-linked molecular structure, three-way synergy, and the molecular rigidity of the polycarboxylate water-reducing agent is strengthened in both the intramolecular structure and the intermolecular structure, so that the molecular configuration of the polycarboxylate water-reducing agent is not easy to shrink and difficult to form a curled conformation in the concrete system where sulfate exists, and thus the sulfate does not affect the adsorption of the polycarboxylate water-reducing agent on cement particles. Therefore, the prepared highly adaptable polycarboxylate water-reducing agent is applied to concrete mixtures, and the adaptability to cement is significantly improved, and the dosage is low, the water reduction rate is high, the slump loss is small, and the sulfate resistance is good. In addition, the process of the method is simple, and it has the process characteristics and advantages of industrial production, and solves the technical problem of how to prepare a polycarboxylate water-reducing agent that is resistant to sulfate and has good adaptability. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides the following embodiments 1 to 3 for preparing a highly adaptable polycarboxylate water-reducing agent: Example 1 85 g of ethylene glycol monovinyl polyglycol ether, 30 g of 2-methoxy-4-vinylphenol, 5 g of diallyldimethylsilane, 2 g of hydrogen peroxide, 15 g of ethanol and 50 g of water were added into a reaction kettle and stirred for reaction at a temperature of 20°C. 30.6 g of vitamin C aqueous solution, 43 g of acrylic acid aqueous solution and 30.4 g of thioglycolic acid aqueous solution were added dropwise to the reactor at a uniform speed for 3 h. After the addition was completed, the temperature was kept at 20°C for 1 h to obtain a copolymer product; After the insulation is completed, the pH is adjusted to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate water-reducing agent.

[0018] In this embodiment, preferably, the molecular weight of the ethylene glycol monovinyl polyglycol ether is 5000.

[0019] In this embodiment, preferably, the vitamin C aqueous solution is prepared by dissolving 0.6 g of vitamin C in 30 parts of water.

[0020] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 13 g of acrylic acid in 30 parts of water.

[0021] In this embodiment, preferably, the thioglycolic acid aqueous solution is prepared by dissolving 0.4 g of thioglycolic acid in 30 parts of water.

[0022] Example 2 90 g of 4-hydroxybutyl vinyl 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 were added into a reaction kettle and stirred for reaction at a temperature of 25°C. 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 reactor at a uniform speed for 3 h. After the addition was completed, the temperature was kept at 25°C for 1 h to obtain a copolymer product; After the insulation is completed, the pH is adjusted to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate water-reducing agent.

[0023] In this embodiment, preferably, the molecular weight of the 4-hydroxybutyl vinyl polyethylene glycol ether is 6000.

[0024] 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.

[0025] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 17 g of acrylic acid in 30 parts of water.

[0026] In this embodiment, preferably, the mercaptopropionic acid aqueous solution is prepared by dissolving 0.6 g of mercaptopropionic acid in 30 parts of water.

[0027] Example 3 85 g of ethylene glycol monovinyl polyglycol 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 were added into a reaction kettle and stirred for reaction at a temperature of 30°C. 30.9 g of vitamin C aqueous solution, 48 g of acrylic acid aqueous solution and 30.5 g of thioglycolic acid aqueous solution were added to the reactor at a uniform speed for 3 h. After the addition was completed, the temperature was kept at 30°C for 1 h to obtain a copolymer product; After the insulation is completed, the pH is adjusted to 6-7 with sodium hydroxide aqueous solution to obtain a highly adaptable polycarboxylate water-reducing agent.

[0028] In this embodiment, preferably, the molecular weight of the ethylene glycol monovinyl polyglycol ether is 6000.

[0029] In this embodiment, preferably, the vitamin C aqueous solution is prepared by dissolving 0.9 g of vitamin C in 30 parts of water.

[0030] In this embodiment, preferably, the acrylic acid aqueous solution is prepared by dissolving 18 g of acrylic acid in 30 parts of water.

[0031] In this embodiment, preferably, the thioglycolic acid aqueous solution is prepared by dissolving 0.5 g of thioglycolic acid in 30 parts of water.

[0032] The present invention also provides the following comparative examples 1 to 4 for preparing a polycarboxylate water reducer: Comparative Example 1 The difference between this comparative example and Example 1 is that no crosslinking agent is added, that is, 5 g of diallyldimethylsilane described in Example 1 is not added; other components, proportions, operating steps and process parameters are consistent with Example 1 of the present invention.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that no functional monomer is added, that is, 30 g of 2-methoxy-4-vinylphenol described in Example 1 is not added; other components, proportions, operating steps and process parameters are consistent with Example 1 of the present invention.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that no functional monomer and cross-linking agent are added, that is, 30 g of 2-methoxy-4-vinylphenol and 5 g of diallyldimethylsilane described in Example 1 are not added; other components, proportions, operating steps and process parameters are consistent with Example 1 of the present invention.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is that the functional monomer is replaced by 2-allylphenol whose molecular structure does not contain intramolecular hydrogen bonds; other components, proportions, operating steps and process parameters are consistent with Example 1 of the present invention.

[0036] The highly adaptable polycarboxylate water-reducing agents prepared in Examples 1 to 3 and the polycarboxylate water-reducing agents prepared in Comparative Examples 1 to 4 were subjected to conformation determination and concrete mixture performance test.

[0037] Performance Test 1 Determination of the conformation of polycarboxylate water-reducing agent solution The polycarboxylate water-reducing agents prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to solution conformation determination using a Malvern Panalytical Viscotek 270 dynamic and static light scattering instrument; wherein Na2SO4 was used to adjust the SO4 2- concentration, the polymer concentration was 1 mg / mL, and the test angle was 90°; the solution conformation determination results are listed in Table 1.

[0038] Table 1 Conformation determination results of polycarboxylate water-reducing agent solutions obtained in Examples 1 to 3 and Comparative Examples 1 to 4

[0039] According to the data in Table 1, after adding the sulfate solution, the hydrodynamic radius of the polycarboxylate water-reducer solution is reduced. The hydrodynamic radius of the polycarboxylate water-reducer solution prepared in Comparative Example 3 is significantly reduced. The reduction level of the hydrodynamic radius when the sulfate concentration is 20 mmol / L and 80 mmol / L is about 1 nm and 2 nm, respectively. Its molecular structure is curled and the conformation is significantly shrunk. The reduction degree of the hydrodynamic radius of the polycarboxylate water-reducer solutions prepared in Comparative Examples 1, 2 and 4 is less than that in Comparative Example 3. The reduction level of the hydrodynamic radius under the second level of sulfate concentration is about 0.4 nm and 0.8 nm, respectively. It can be seen that simply introducing a functional monomer or a cross-linking agent having a benzene ring and an intramolecular hydrogen bond into the polycarboxylate water-reducer can enhance the molecular rigidity to a certain extent and inhibit the conformational curling phenomenon under the action of sulfate.

[0040] The degree of reduction in the hydrodynamic radius of the highly adaptable polycarboxylate water-reducing agent solutions prepared in Examples 1 to 3 is significantly less than that of Comparative Examples 1 to 4, and the level of reduction in the hydrodynamic radius under the second-level sulfate concentration is only between 0.15 nm and 0.35 nm. It can be seen that the present invention simultaneously introduces benzene rings, intramolecular hydrogen bonds and cross-linking agents into the polycarboxylate water-reducing agent, and the ring structure closed by the benzene ring limits the flexibility of the polycarboxylate water-reducing agent molecules, thereby improving the molecular rigidity. The special intramolecular hydrogen bonds further improve the molecular rigidity of the polycarboxylate water-reducing agent, and the introduction of the cross-linking agent enables the polycarboxylate water-reducing agent to have a cross-linked molecular structure. The three-way synergy and the superposition of benefits make the molecular configuration of the highly adaptable polycarboxylate water-reducing agent provided by the present invention difficult to shrink and difficult to form a curled conformation in the presence of sulfate.

[0041] Performance test 2 Concrete mixture performance test The highly adaptable polycarboxylate water-reducing agents prepared in Examples 1 to 3 of the present invention and the polycarboxylate water-reducing agents prepared in Comparative Examples 1 to 4 were added with an appropriate amount of water to adjust the concentration to 50%, and the concrete mixture performance test was performed in accordance with GB / T 50080-2016 Ordinary Concrete Mixture Performance Test Method Standard; wherein the concrete mix ratio is: cement 360 kg / m 3 、Mechanical sand 790kg / m 3 、Stone 1060 kg / m 3 , water 162 kg / m 3 , and add Na2SO4 to the water to adjust the SO4 in the concrete 2- Concentration; the test results are listed in Table 2.

[0042] Table 2 Test results of the effects of polycarboxylate water-reducing agents prepared in Examples 1 to 3 and Comparative Examples 1 to 4 on concrete properties

[0043] According to the data in Table 2, the polycarboxylate water-reducing agent prepared in Comparative Example 3 is applied to concrete. After adding sulfate to the concrete water, the initial dispersion performance and slump-retaining performance of the concrete are significantly reduced when the sulfate content is high, which clearly shows that it is not adaptable to sulfate; the polycarboxylate water-reducing agents prepared in Comparative Examples 1, 2 and 4 are applied to concrete. After adding sulfate to the concrete water, the initial dispersion performance and slump-retaining performance of the concrete are reduced when the sulfate content is high, but the degree of reduction is less than that of Comparative Example 3; and the highly adaptable polycarboxylate water-reducing agent prepared in Examples 1 to 3 is used for concrete. After adding sulfate to the concrete water, it has good initial dispersion and slump-retaining performance in concrete with different sulfate contents, and has good adaptability to sulfate. This is mainly because the polycarboxylate water-reducing agent prepared in Comparative Examples 1 to 4 has a significantly reduced hydrodynamic radius in the concrete system where sulfate exists, the molecular structure is in a curled state, and the conformation shrinks, making it difficult to adsorb on cement particles, affecting the dispersion and slump-retaining performance of concrete. The present invention directly connects the rigid benzene ring and the intramolecular hydrogen bond in the functional monomer into the molecular structure of the polycarboxylate water-reducing agent by adding a functional monomer and a cross-linking agent, and synergistically improves the molecular rigidity of the polycarboxylate water-reducing agent. Furthermore, the cross-linking agent is used to make the polycarboxylate water-reducing agent have a cross-linked molecular structure, and the molecular rigidity of the polycarboxylate water-reducing agent is strengthened from the intramolecular structure and the intermolecular structure at the same time, and the conformational curling phenomenon under the action of sulfate is slowed down at the molecular conformation level. When applied to concrete mixtures, the adaptability to cement is improved, the incompatibility is reduced, the adsorption on cement particles is good, and the polycarboxylate water-reducing agent has better water-reducing and dispersing performance and slump-retaining performance.

[0044] In summary, the highly adaptable polycarboxylate water-reducing agent prepared by the present invention has the advantages of good cement adaptability, good slump retention performance, low dosage, high water reduction rate, good sulfate resistance, etc.

[0045] Although the terms such as cement adaptability, sulfate resistance, conformational curling, molecular rigidity, etc. are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 water-reducing agent, characterized in that: The following steps are involved: S100, adding vinyl polyether macromonomer, functional monomer, crosslinking agent, oxidant, alcohol solvent and water into a reaction kettle by weight, and stirring for reaction; S101, adding a reducing agent aqueous solution, an unsaturated carboxylic acid aqueous solution and a chain transfer agent aqueous solution into a reactor respectively and simultaneously for reaction; S102, heat preservation, to obtain a copolymer product; S103, adjusting the pH to 6-7 to obtain a highly adaptable polycarboxylate water-reducing agent; The weight ratio of the vinyl polyether macromonomer to the functional monomer is 1-4:6-10; The functional monomer structural formula is as follows: Wherein, R1 is -OCH3 or -OCH2CH=CH2, R2 is -H or -CH2CH=CH2, and R3 is -H or -CH2CH=CH2 or -CH=CH-CH3.

2. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 1, characterized in that: The distribution ratio of each group is as follows: Vinyl polyether macromonomer 60~100 parts Functional monomer 10~40 parts Crosslinking agent 5~10 parts 1~2 parts of oxidant Alcohol solvent 10~30 parts 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 method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 1, characterized in that: The reaction temperature and the insulation temperature are both 20-30°C, and the insulation time is 1-3 h; The reducing agent aqueous solution, unsaturated carboxylic acid aqueous solution and chain transfer agent aqueous solution are added to the reactor in a uniform dropwise manner for 3 to 4 hours.

4. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 1, characterized in that: The molecular weight of the vinyl polyether macromonomer is 5000-6000.

5. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 1, characterized in that: The cross-linking agent is any one or any combination of diallyldimethylsilane, 1,4-pentadien-3-ol and trimethylolpropane diallyl ether.

6. The method for preparing a highly adaptable polycarboxylate water-reducing agent 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 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 of water; The chain transfer agent aqueous solution is prepared by dissolving 0.3 to 1.0 parts by weight of the chain transfer agent in 30 parts of water.

7. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 6, characterized in that: The reducing agent is any one or any combination of bisulfite, sulfite, sodium formaldehyde sulfoxylate and vitamin C.

8. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 6, characterized in that: The unsaturated carboxylic acid is any one or any combination of acrylic acid, methacrylic acid and itaconic acid.

9. The method for preparing a highly adaptable polycarboxylate water-reducing agent according to claim 6, characterized in that: The chain transfer agent is any one or any combination of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, n-dodecyl mercaptan and tert-dodecyl mercaptan.

10. A highly adaptable polycarboxylate water reducer, characterized in that: The polycarboxylate water-reducing agent is prepared by the preparation method of the highly adaptable polycarboxylate water-reducing agent according to any one of claims 1 to 9.

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