A composite polycarboxylate water reducer and its preparation method

Abstract

This application relates to the field of water reducers, and specifically discloses a composite polycarboxylate water reducer and a preparation method thereof. The composite polycarboxylate water reducer comprises at least polycarboxylate water reducer and a promoter with a mass ratio of 10-15:1-3. The promoter is prepared by polycondensation of polyether diol and bifunctional phenylsilane coupling agent with a molar ratio of 2:1 under vacuum and catalyzed by dodecylbenzenesulfonic acid. The composite polycarboxylate water reducer of this application has good adaptability to concrete systems with a relatively high carbon content, can effectively ensure the dispersion performance of the water reducer, and improve the strength performance of concrete.

Description

Technical Field

[0001] This application relates to the field of water reducers, and particularly to a composite polycarboxylate water reducer and its preparation method. Background Art

[0002] Polycarboxylate water reducers have the advantages of low dosage, high water reduction rate, good slump retention, high compatibility, and environmental friendliness, so they have gradually replaced other water reducers and are widely used, especially in the fields of high-strength and high-performance concrete, where they have an irreplaceable position.

[0003] In practical applications, problems such as poor water reduction effect and decreased dispersion ability of polycarboxylate water reducers have also emerged, resulting in a decrease in concrete strength. Especially in concrete with a high carbon content in cement, due to the porous structure of the carbon particles in the fly ash used in the cement raw materials, the adsorption amount of polycarboxylate water reducers by them is relatively high, affecting the exertion of the water reduction effect of polycarboxylate water reducers, and then making it difficult for cement particles to disperse and hydrate, reducing the concrete strength. Summary of the Invention

[0004] This application provides a composite polycarboxylate water reducer and its preparation method, which can effectively overcome the problem of the performance decline of polycarboxylate water reducers caused by high carbon content in cement, and further lead to the decline of concrete strength.

[0005] In the first aspect, this application provides a composite polycarboxylate water reducer, which at least includes a polycarboxylate water reducer and a promoter with a mass ratio of 10 - 15:1 - 3. The promoter is prepared by polycondensation of polyether diol and bifunctional phenyl silane coupling agent with a molar ratio of 2:1 under vacuum and catalyzed by dodecylbenzenesulfonic acid.

[0006] The carbon particles in concrete come from the fly ash incorporated in the cement. The carbon particles formed by carbonization during the high-temperature calcination of fly ash have a porous structure and extremely high surface energy, and have a strong adsorption effect on polycarboxylate water reducers, affecting the water reduction and dispersion effect. The above-mentioned promoter used in this application is a dehydration polycondensation product of polyether diol and bifunctional phenyl silane coupling agent, which has high activity and can quickly adsorb on the surface of carbon particles, form a water film and generate steric hindrance through the polyether long chain, and effectively prevent the polycarboxylate water reducer from being adsorbed by carbon particles through the compensatory effect, fully ensuring its water reduction and dispersion effect, promoting the hydration process of cement particles, and realizing the improvement of concrete strength.

[0007] The bifunctional silane coupling agent described in this application refers to a silane coupling agent containing two alkoxy groups. After hydrolysis, the two silanol groups formed respectively undergo polycondensation reactions with a polyether diol molecule, thereby forming a polyether silane long chain containing two terminal hydroxyl groups and phenyl and methyl side chains, playing a good role in steric hindrance and dispersion.

[0008] Preferably, the degree of vacuum for evacuation is -0.09 MPa to -0.1 MPa.

[0009] Preferably, the time for the polycondensation reaction is 3 to 5 h.

[0010] Preferably, the dosage of dodecylbenzenesulfonic acid is 2% to 5% of the mass of the polyether diol.

[0011] Preferably, the molecular weight of the polyether diol is 1000 to 3000.

[0012] The particle sizes of the carbon particles and soil particles contained in the concrete are much smaller than those of the cement particles. Under the action of high surface energy, the flocs formed by their agglomeration will wrap a large amount of water, affecting the water-reducing effect, and then hindering the cement hydration process and resulting in a decrease in concrete strength. At the same time, the structure of this flocculent soil is compact, and it is difficult for the polycarboxylate water reducer to penetrate between the particles to play a dispersing role, and it is difficult to destroy the flocs. Therefore, a polyether diol with a relatively small molecular weight is selected as the raw material for the accelerator, which can reduce the chain length of the accelerator, significantly improve the permeability of the accelerator, play a role in destroying the flocs, releasing water, promoting hydration, and enhancing the concrete strength.

[0013] Preferably, the difunctional phenylsilane coupling agent is at least one of methylphenyl dimethoxysilane and methylphenyl diethoxysilane.

[0014] Preferably, the preparation method of the accelerator is as follows: Dissolve the polyether diol in ethylene glycol, add the difunctional phenylsilane coupling agent and dodecylbenzenesulfonic acid, mix evenly, and react under the conditions of 60 to 100 °C and evacuation. After the reaction is completed, ethylene glycol is recovered by vacuum distillation to obtain the accelerator.

[0015] Under vacuum and reduced pressure, the silanol groups generated by the hydrolysis of the difunctional phenylsilane coupling agent are catalyzed by an acid catalyst to undergo a polycondensation reaction with the polyether diol to obtain the accelerator.

[0016] Preferably, the accelerator is a modified accelerator, and the modified accelerator is prepared according to the following method:

[0017] Heat the accelerator to 60 to 90 °C, add aminosulfonic acid and urea, stir and mix after dropping, then raise the temperature to 110 to 140 °C, and keep warm for the sulfonation reaction; after the heat preservation is completed, cool down to 80 to 90 °C, dropwise add an alkali solution for neutralization, evacuate to remove ammonia gas, and dilute with water to obtain the modified accelerator.

[0018] Under the catalysis of urea, sulfonation reaction occurs between sulfamic acid and one of the terminal hydroxyl groups of the promoter, introducing -SO3Na into the molecular chain of the promoter. As a result, the promoter can play a more prominent dispersing role through electrostatic interaction, effectively improving the water-reducing effect on carbon particles, soil particles or their flocs, and being beneficial to enhancing the curing strength of concrete. In addition, after grafting and modifying with sulfonic acid groups, the compatibility with polycarboxylate water-reducing agents can be improved, reducing the bleeding phenomenon.

[0019] Preferably, the molar ratio of the polyether diol to sulfamic acid is 2:1 to 1.3.

[0020] Under normal circumstances, 2 mol of polyether diol reacts with a bifunctional phenylsilane coupling agent to obtain a promoter with two terminal hydroxyl groups. After the promoter reacts with 1 mol of sulfamic acid, one -SO3Na is introduced, enabling the remaining terminal hydroxyl group to form a hydrogen bond adsorption with carbon particles or soil particles, thereby generating a steric hindrance effect and an electrostatic adsorption effect. Appropriately increasing the dosage of sulfamic acid in this application is beneficial to the full reaction of the promoter.

[0021] Preferably, the molar ratio of the polyether diol to urea is 2:0.5 to 1.

[0022] Preferably, the heat preservation time is 3 to 6 h.

[0023] In a second aspect, this application provides a preparation method of a composite polycarboxylate water-reducing agent, which is obtained by uniformly mixing the polycarboxylate water-reducing agent and the promoter according to the ratio.

[0024] This composite polycarboxylate water-reducing agent can effectively overcome the problem of the decline in the water-reducing and dispersing effect of polycarboxylate water-reducing agents caused by high carbon content and high mud content in concrete, ensuring the strength performance of concrete.

[0025] It should be noted that air-entraining agents, foam stabilizers, water retention agents, thickeners and other concrete additives can be added to the composite carboxylic acid water-reducing agent of this application as needed. The dosage of this composite water reducer in concrete is 0.5 to 2 wt%.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. By using a promoter prepared by reacting polyether diol with a bifunctional phenylsilane coupling agent and compounding it with a polycarboxylate water-reducing agent, the strength performance of high-carbon-content concrete is significantly improved.

[0028] 2. By using polyether diol with a molecular weight of 1000 to 3000, the obtained promoter has excellent penetration and dispersion effects on the flocs formed by carbon particles and soil particles, thereby effectively releasing the water wrapped in the flocs, playing a good water-reducing role, and improving the workability and strength performance of concrete.

[0029] 3. By sulfonating and modifying the accelerator, the water-reducing dispersion performance of the accelerator can be further adjusted, thereby improving the strength of the concrete. Detailed implementation manners

[0030] Preparation examples of the accelerator

[0031] Preparation Example 1. A modified accelerator is prepared by the following method:

[0032] Step 1: Dissolve 2 mol of polyether diol (molecular weight 2000) in 5 L of ethylene glycol, add 1 mol of methylphenyl dimethoxysilane and 0.12 kg of dodecylbenzenesulfonic acid, and stir evenly; heat up to 85 °C, evacuate to -0.09 MPa, and carry out polycondensation reaction for 5 h. Recover ethylene glycol by vacuum distillation to obtain the accelerator.

[0033] Step 2: Heat the accelerator obtained above to 70 °C, add 1.2 mol of sulfamic acid and 0.8 mol of urea, stir and mix after dropping, then heat up to 130 °C and keep warm for 5 h for sulfonation reaction; after the heat preservation ends, cool down to 90 °C, dropwise add 10 wt% sodium hydroxide aqueous solution for neutralization, evacuate to -0.09 MPa to remove ammonia gas, and the degassing time is 2 h. After degassing, add 30 mol of water for dilution to obtain the modified accelerator.

[0034] Preparation Example 2. A modified accelerator is prepared by the following method:

[0035] Step 1: Dissolve 2 mol of polyether diol (molecular weight 1000) in 3 L of ethylene glycol, add 1 mol of methylphenyl diethoxysilane and 0.2 kg of dodecylbenzenesulfonic acid, and stir evenly; heat up to 60 °C, evacuate to -0.1 MPa, and carry out polycondensation reaction for 4 h. Recover ethylene glycol by vacuum distillation to obtain the accelerator.

[0036] Step 2: Heat the accelerator obtained above to 90 °C, add 1 mol of sulfamic acid and 0.5 mol of urea, stir and mix after dropping, then heat up to 140 °C and keep warm for 3 h for sulfonation reaction; after the heat preservation ends, cool down to 80 °C, dropwise add 20 wt% sodium hydroxide aqueous solution for neutralization, evacuate to -0.09 MPa to remove ammonia gas, and the degassing time is 1.5 h. After degassing, add 12 mol of water for dilution to obtain the modified accelerator.

[0037] Preparation Example 3. A modified accelerator is prepared by the following method:

[0038] Step 1: Dissolve 2 mol of polyether diol (molecular weight 3000) in 5 L of ethylene glycol, add 1 mol of methylphenyl dimethoxysilane and 0.15 kg of dodecylbenzenesulfonic acid, and stir evenly; heat up to 100 °C, evacuate to -0.09 MPa, carry out polycondensation reaction for 3 h, and recover ethylene glycol by vacuum distillation to obtain the accelerator.

[0039] Step 2: Heat the accelerator obtained above to 60 °C, add 1.3 mol of sulfamic acid and 1 mol of urea, stir and mix after dropping, then heat up to 130 °C, keep warm for 6 h for sulfonation reaction; after the heat preservation is over, cool down to 90 °C, dropwise add 10 wt% potassium hydroxide aqueous solution for neutralization, evacuate to -0.09 MPa to remove ammonia gas, and the degassing time is 2 h. After degassing, add 35 mol of water for dilution to obtain the modified accelerator.

[0040] Preparation Example 4, an accelerator, different from Preparation Example 1 in that the accelerator is not modified with sulfamic acid, that is, the operation of Step 2 is not carried out.

[0041] Preparation Example 5, an accelerator, different from Preparation Example 4 in that polyether diol with a molecular weight of 4000 is used in Step 1. The specific preparation method is as follows:

[0042] Step 1: Dissolve 2 mol of polyether diol (molecular weight 4000) in 10 L of ethylene glycol, add 1 mol of methylphenyl dimethoxysilane and 0.3 kg of dodecylbenzenesulfonic acid, and stir evenly; heat up to 95 °C, evacuate to -0.09 MPa, carry out polycondensation reaction for 5 h, and recover ethylene glycol by vacuum distillation to obtain the accelerator.

[0043] Preparation Example 6, an accelerator, different from Preparation Example 4 in that polyether diol with a molecular weight of 600 is used in Step 1. The specific preparation method is as follows:

[0044] Step 1: Dissolve 2 mol of polyether diol (molecular weight 600) in 10 L of ethylene glycol, add 1 mol of methylphenyl dimethoxysilane and 0.05 kg of dodecylbenzenesulfonic acid, and stir evenly; heat up to 80 °C, evacuate to -0.09 MPa, carry out polycondensation reaction for 3 h, and recover ethylene glycol by vacuum distillation to obtain the accelerator.

[0045] Preparation Example of Polycarboxylate Superplasticizer

[0046] A polycarboxylate superplasticizer is prepared according to the following steps:

[0047] Step 1: Add 36 kg of ethylene glycol mono vinyl polyethylene glycol ether, 0.5 kg of sodium persulfate, 0.4 kg of sodium hypophosphite and 42 kg of water into the reaction kettle;

[0048] Step 2: Then, 3.3 kg of acrylic acid and 15.8 kg of water are configured into A dropping liquid;

[0049] Step 3: Then, 0.2 kg of vitamin C and 1.8 kg of water are configured into B dropping liquid;

[0050] Step 4: Under the condition of 10 °C, A dropping liquid and B dropping liquid are added dropwise to the reaction kettle, added dropwise at a uniform speed for 1 hour, and then kept warm for half an hour to obtain vinyl ethylene glycol ether polycarboxylate water reducer. Example

[0051] In the following examples or comparative examples, the polycarboxylate water reducer used is the vinyl ethylene glycol ether polycarboxylate water reducer obtained in the above preparation example.

[0052] Example 1, a composite polycarboxylate water reducer, is obtained by mixing 12.5 kg of polycarboxylate water reducer with 2.5 kg of the modified promoter obtained in Preparation Example 1.

[0053] Example 2, a composite polycarboxylate water reducer, is obtained by mixing 10 kg of polycarboxylate water reducer with 1 kg of the modified promoter obtained in Preparation Example 2.

[0054] Example 3, a composite polycarboxylate water reducer, is obtained by mixing 15 kg of polycarboxylate water reducer with 3 kg of the modified promoter obtained in Preparation Example 3.

[0055] Example 4, a composite polycarboxylate water reducer, is different from Example 1 in that the promoter obtained in Preparation Example 4 in an equal amount is used to replace the modified promoter obtained in Preparation Example 1.

[0056] Example 5, a composite polycarboxylate water reducer, is different from Example 1 in that the promoter obtained in Preparation Example 5 in an equal amount is used to replace the modified promoter obtained in Preparation Example 1.

[0057] Example 6, a composite polycarboxylate water reducer, is different from Example 1 in that the promoter obtained in Preparation Example 6 in an equal amount is used to replace the modified promoter obtained in Preparation Example 1.

[0058] Comparative Example

[0059] Comparative Example 1, a composite polycarboxylate water reducer, is different from Example 4 in that it is obtained by mixing 11 kg of polycarboxylate water reducer with 4 kg of the modified promoter obtained in Preparation Example 1.

[0060] Comparative Example 2, a composite polycarboxylate water reducer, is different from Example 4 in that it is obtained by mixing 14.5 kg of polycarboxylate water reducer with 0.5 kg of the modified promoter obtained in Preparation Example 1.

[0061] Comparative Example 3, a composite polycarboxylate water reducer, is different from Example 4 in that an equal amount of polycarboxylate water reducer is used to replace the accelerator, that is, it only contains 15 kg of polycarboxylate water reducer.

[0062] Performance detection test

[0063] Specimen preparation: Mix 10 kg of cement (P.O 32.5), 5.5 kg of Class II fly ash (loss on ignition is 5%), 3.8 kg of water, 11.1 kg of sand, 27.2 kg of crushed stone (continuous grading of 16 - 31.5 mm, mud content 2%), and 0.55 kg of composite water reducer (1 wt%) evenly to make standard concrete test blocks. After curing for 28 days, measure their compressive strength. The test method is carried out in accordance with the provisions of GB / T 17671-1999 Test method for strength of cement mortar (ISO method). The higher the compressive strength, the better the adaptability of the composite water reducer to concrete and the better the water-reducing and dispersing performance. The test results are shown in Table 1.

[0064] Note: Class II fly ash has a high loss on ignition and a high carbon content.

[0065] Table 1. Performance test results of composite water reducer

[0066]

[0067] Result analysis:

[0068] (1) Combining Examples 1 - 6 and Comparative Examples 1 - 3 and Table 1, it can be seen that in this application, by using polycarboxylate water reducer in combination with an accelerator, the water-reducing and dispersing effect on concrete with high carbon content and mud content is significantly improved, and the compressive strength after concrete curing is effectively increased. The reason for this phenomenon may be that the accelerator can be quickly and densely adsorbed on the surface of porous carbon particles, playing a steric hindrance role on the polycarboxylate water reducer, ensuring the water-reducing and dispersing effect of the polycarboxylate water reducer on cement particles, thereby promoting the hydration process and increasing the concrete strength.

[0069] (2) Combining Example 1 and Example 4 and Table 1, it can be seen that in this application, by modifying the accelerator with aminosulfonic acid and introducing sulfonic acid groups into the accelerator molecular chain, the dispersion effect of the accelerator can be further improved, effectively dispersing the flocs formed by carbon particles and soil particles, releasing the water wrapped by them, enhancing the water-reducing effect, and improving the curing strength of concrete. At the same time, it can reduce the bleeding phenomenon of concrete.

[0070] (3) By combining Example 4 with Examples 5-6 and referring to Table 1, it can be seen that by using polyether diol with a molecular weight of 1000-3000 as the raw material in this application, it is beneficial to improve its water-reducing and dispersing effect. If the molecular weight is too small or too large, it is easy to reduce the water-reducing effect. The reason may be that too small a molecular weight will lead to a decrease in the steric hindrance ability of its product, and too large a molecular weight will result in a decrease in permeability, especially the permeability to carbon particles and soil flocs, thereby leading to a decrease in the adsorption water-reducing and dispersing effect, which is not conducive to the improvement of concrete strength.

[0071] This specific embodiment is only an explanation of this application and does not limit this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A composite polycarboxylate water reducer, characterized in that, It contains at least a polycarboxylate water reducer and a promoter with a mass ratio of 10 - 15:1 - 3. The preparation method of the promoter is as follows: dissolve polyether diol in ethylene glycol, add a difunctional phenyl silane coupling agent and dodecylbenzenesulfonic acid, mix evenly, react under the conditions of 60 - 100 °C and vacuum, after the reaction is completed, recover ethylene glycol by vacuum distillation to obtain the promoter; the molar ratio of the polyether diol to the difunctional phenyl silane coupling agent is 2:1; the molecular weight of the polyether diol is 1000 - 3000; the difunctional phenyl silane coupling agent uses at least one of methylphenyl dimethoxysilane and methylphenyl diethoxysilane.

2. The composite polycarboxylate water reducer according to claim 1, wherein The promoter is a modified promoter, and the modified promoter is prepared according to the following method: Heat the promoter to 60 - 90 °C, add aminosulfonic acid and urea, after dropping, stir and mix, then raise the temperature to 110 - 140 °C, keep warm for sulfonation reaction; after the insulation is over, cool down to 80 - 90 °C, dropwise add an alkali solution for neutralization, vacuum to remove ammonia gas, add water for dilution to obtain the modified promoter.

3. The composite polycarboxylate water reducer according to claim 2, wherein The molar ratio of the polyether diol to the aminosulfonic acid is 2:1 - 1.

3.

4. A composite polycarboxylate water reducer according to claim 2, characterized in that, The molar ratio of the polyether diol to the urea is 2:0.5 - 1.

5. A composite polycarboxylate water reducer according to claim 2, characterized in that, The heat preservation time is 3 - 6 h.

6. The composite polycarboxylate water reducing agent according to claim 2, characterized in that, The alkali solution uses a 10 - 20 wt% sodium hydroxide or potassium hydroxide solution.

7. The preparation method of a composite polycarboxylate water reducer according to any one of claims 1 to 6, characterized in that, Mix the polycarboxylate water reducer and the promoter evenly according to the ratio to obtain.

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