Air-entraining type polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the field of concrete admixtures, and particularly discloses an air-entraining type polycarboxylic acid water reducer and a preparation method thereof. The air-entraining type polycarboxylate superplasticizer is prepared from the following raw materials in parts by weight: 320 to 380 parts of unsaturated polyether macromonomer, 10 to 30 parts of air-entraining type functional monomer, 26 to 50 parts of unsaturated carboxylic acid or unsaturated carboxylic acid derivative, 1 to 4 parts of oxidizing agent, 0.5 to 2 parts of reducing agent, 0.6 to 2.8 parts of chain transfer agent, 18 to 30 parts of neutralizing agent and 500 to 600 parts of water, the preparation method of the air-entraining type functional monomer comprises the following steps: crushing maleated rosin, mixing the crushed maleated rosin with 48% liquid caustic soda, heating to 100-125 DEG C, carrying out heat preservation reaction for 1-2 hours, and adding water for dilution after the reaction is finished. According to the polycarboxylate superplasticizer, the air-entraining type functional monomer is added, so that the dispersity of the superplasticizer is not influenced, the polycarboxylate superplasticizer has relatively low air-entraining property, and the polycarboxylate superplasticizer has the advantages of improving the workability of concrete and increasing the freezing resistance and durability of the concrete at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of concrete admixtures, and more specifically, to an air-entraining polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] Concrete admixtures refer to substances added to concrete before or during mixing to improve the performance of concrete. Since admixtures can effectively improve the performance of concrete and have good economic benefits, they are widely used in many countries and are increasingly valued in engineering applications, becoming an indispensable material in concrete. Among them, water reducer is the most important admixture in concrete. It can reduce the amount of mixing water and improve the strength of concrete under the condition that the workability of concrete and the amount of cement remain unchanged; or save the amount of cement under the condition that the workability and strength remain unchanged.

[0003] For fresh concrete, uniform small bubbles and appropriate air content are favorable factors for maintaining the fluidity of concrete, because the "ball rolling" and "floating" effects of bubbles can effectively improve the workability of concrete. For hardened concrete, appropriate air content and uniform pores can improve the pore structure of hardened concrete and improve crack resistance and frost resistance. When polycarboxylic acid-based high-performance water reducer is used as a concrete admixture, the bubbles generated by the inclusion of air during the mixing process of concrete are usually uneven in size, that is, the quality of the introduced foam is poor, the foam stabilization performance is also poor, and the air content is far higher than the allowable value. The larger bubbles in the concrete will burst quickly, and the smaller bubbles cannot exist stably, which will reduce the strength of the concrete and deteriorate the antifreeze performance.

[0004] Therefore, admixtures such as defoamers and foam stabilizers are currently used to improve the problem of uneven bubble size or excessive air content during concrete mixing. However, defoamers are mostly lipophilic substances with low HLB values, and have poor compatibility with water-soluble polycarboxylate superplasticizer mother liquor. The polycarboxylate superplasticizer mother liquor mixed with the defoamer is unstable and easily produces the "floating oil" phenomenon, that is, the defoamer is suspended in the upper layer of the polycarboxylate superplasticizer mother liquor, and cannot play the role of defoaming and foam control, and cannot improve the compressive strength and antifreeze and anti-cracking properties of concrete.

[0005] In view of the above-mentioned related technologies, the inventors found that it is urgent to develop a water reducing agent that introduces uniform bubbles and stable foam, so as to improve the bubble content and uniformity of concrete, and enhance the compressive strength, frost resistance and crack resistance of concrete. Summary of the invention

[0006] In order to make the bubbles introduced into the water reducer uniform and fine, and to improve the foam stability, thereby improving the workability of concrete, the present application provides an air-entraining polycarboxylic acid water reducer and a preparation method thereof.

[0007] In the first aspect, the present application provides an air-entraining polycarboxylate water-reducing agent, which adopts the following technical solution: An air-entraining polycarboxylate water-reducing agent comprises the following raw materials in parts by weight: 320-380 parts of an unsaturated polyether macromonomer, 10-30 parts of an air-entraining functional monomer, 26-50 parts of an unsaturated carboxylic acid or an unsaturated carboxylic acid derivative, 1-4 parts of an oxidant, 0.5-2 parts of a reducing agent, 0.6-2.8 parts of a chain transfer agent, 18-30 parts of a neutralizer, and 500-600 parts of water; The preparation method of the air-entraining functional monomer is as follows: crushing maleic rosin, mixing with 48% liquid caustic soda, heating to 100-125° C., keeping the temperature for reaction for 1-2 hours, adding water after the reaction is finished, and diluting to a solid content of 23-25%.

[0008] By adopting the above technical scheme, the polyether macromonomer contains multiple ether bonds and reactive active hydrogen atoms, and the unsaturated carboxylic acid or unsaturated carboxylic acid derivative contains unsaturated double bonds. Under the action of the oxidant, the system generates free radicals, which attack the double bonds of the unsaturated carboxylic acid, triggering a chain polymerization reaction. Subsequently, the active hydrogen atoms on the polyether macromonomer may also be attacked by the free radicals, thereby connecting to the polymer chain to form a polycarboxylic acid water reducer with specific structure and properties.

[0009] The added functional air-entraining monomer is made of maleic rosin and liquid caustic soda. Maleic rosin is a compound containing conjugated double bonds. The double bonds in its structure can react with unsaturated carboxylic acids to introduce more functional groups and branches, increase the complexity and performance of the polymer, and have a good air-entraining effect during the concrete mixing process. It can adsorb air to form tiny bubbles, improve the amount of bubbles formed by air entrainment, the persistence of bubbles, and the fineness and uniformity of bubbles, thereby improving the freeze-thaw resistance and durability of concrete and reducing the formation of harmful bubbles with larger diameters. Therefore, there is no need to add defoamers, foam stabilizers and other additives to obtain a good air-entraining effect, thereby reducing the impact of excessive admixtures on the working performance of concrete.

[0010] Optionally, the mass ratio of the maleic rosin to 48% liquid caustic soda is 1-1.5:0.36-0.45.

[0011] By adopting the above technical scheme, marathon rosin is a product of rosin modified by maleic anhydride, which contains functional groups such as carboxyl. Caustic soda, as a strong base, can react with carboxyl to produce corresponding carboxylates and water. When the above amount of maleic rosin and liquid caustic soda are mixed, the carboxyl in the maleic rosin will combine with the hydroxide ions in the caustic soda to form a salt compound of sodium maleic rosinate, which can form stable tiny bubbles in concrete, increase the air entraining capacity of the polycarboxylate water reducer, thereby enhancing the air entraining effect of the polycarboxylate water reducer, reducing the generation of harmful bubbles, and maintaining the content and stability of beneficial bubbles.

[0012] Optionally, the unsaturated polyether macromonomer is selected from at least one of methyl allyl alcohol polyoxyethylene ether, isopentanol polyoxyethylene ether and diethylene glycol polyoxyethylene ether.

[0013] By adopting the above technical scheme, the molecular structure of methyl allyl alcohol polyoxyethylene ether contains a large number of ether bonds and a small amount of unsaturated double bonds, which make it have good water solubility and certain reactivity. When copolymerizing with unsaturated carboxylic acid or its derivatives, it can be used as a component of the main chain or side chain to form a polycarboxylic acid water reducer with specific structure and performance; isopentenol polyoxyethylene ether is prepared by polymerization of isopentenol and ethylene oxide, and similar to methyl allyl alcohol polyoxyethylene ether, it has good water solubility and certain reactivity, and can be copolymerized with other monomers to give the polycarboxylic acid water reducer better dispersibility and stability; diethylene glycol polyoxyethylene ether not only has excellent wettability and permeability, but also has good compatibility and stability. In the synthesis of polycarboxylic acid water reducer, it can improve the dispersion effect and fluidity of the water reducer, and help to form a more uniform and stable polycarboxylic acid molecular structure.

[0014] Optionally, the unsaturated carboxylic acid is acrylic acid or methacrylic acid, and the unsaturated carboxylic acid derivative is at least one of maleic anhydride, methyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate and hydroxypropyl acrylate.

[0015] By adopting the above technical scheme, small molecular monomers such as acrylic acid and methacrylic acid are used as raw materials. These small molecular monomers have strong polarity and reactivity, and can better carry out monomer reaction and polymerization reaction, thereby obtaining a higher degree of polymerization and a better polymerization effect. The formed high molecular polymer has good stability and durability, and the storage stability and service life are improved. Moreover, monomers such as acrylic acid can react with components such as calcium ions in cement to form stable compounds, thereby improving the adaptability of polycarboxylate water reducer in different cements, so that the polycarboxylate water reducer has excellent water reducing properties, slump retention and strengthening properties.

[0016] Optionally, the reducing agent is selected from at least one of L-ascorbic acid, sodium formaldehyde sulfoxylate and ferrous sulfate.

[0017] By adopting the above technical scheme, L-ascorbic acid can participate in the redox reaction by providing electrons or hydrogen atoms, thereby affecting the polymerization rate of the monomer and the molecular structure of the product, effectively promoting the generation of free radicals and chain growth reactions, and accelerating the progress of the polymerization reaction. Ferrous sulfate has a certain reducing property and can also participate in the redox reaction, affecting the polymerization reaction rate and the molecular structure of the product. Moreover, it can also work together with the oxidant to form a system with stronger redox properties, thereby simply affecting the polymerization reaction. Ferrous sulfate can also act as a catalyst to accelerate the progress of the polymerization reaction.

[0018] Optionally, the chain transfer agent is selected from at least one of sodium hypophosphite, thioglycolic acid, mercaptopropionic acid and mercaptoethanol.

[0019] By adopting the above technical scheme, the chain transfer agent can participate in the polymerization reaction, control the progress of the polymerization reaction by transferring free radicals, thereby adjusting the chain length of the polymer, making the molecular weight distribution of the polymer more uniform, and improving the dispersion performance, fluidization effect and compatibility of the polycarboxylate water-reducing agent with cement particles, enhancing its dispersion and thickening effects, while reducing the water bleeding of the concrete and increasing the strength and durability of the concrete.

[0020] Optionally, the oxidant is a 27.5% hydrogen peroxide solution or a 27.5% ammonium persulfate solution.

[0021] By adopting the above technical scheme, hydrogen peroxide and ammonium persulfate can provide the necessary oxidizing capacity for the polymerization reaction, thereby initiating the polymerization reaction between monomer molecules and improving the reaction rate and effect. At the same time, they also participate in the construction process of the molecular structure, which can optimize the molecular structure of the polycarboxylic acid water reducer and make it have better water reducing performance, dispersibility and stability.

[0022] Optionally, the neutralizing agent is a sodium hydroxide solution with a concentration of 32%.

[0023] By adopting the above technical scheme, sodium hydroxide solution is used to adjust the pH of the polycarboxylate water-reducing agent, thereby ensuring the stability of the product and avoiding failure during storage. Moreover, the appropriate pH value can make the polycarboxylate water-reducing agent disperse better in the concrete, improve the fluidity and working performance of the concrete, and the functional groups such as carboxyl in the polycarboxylate water-reducing agent can better play a retarding effect under specific pH conditions, which helps to control the hydration process of the concrete and prevent premature coagulation. Under suitable pH conditions, the polycarboxylate water-reducing agent can be more effectively adsorbed on the surface of cement particles, promote the dispersion and hydration of cement particles, thereby improving the strength and durability of the concrete.

[0024] Optionally, 1-3 parts by weight of a nano auxiliary agent is further added to the air-entraining polycarboxylate water-reducing agent. The preparation method of the nano auxiliary agent is as follows: dispersing lignin nanoparticles in deionized water to form a suspension, adding cocoamidopropyl betaine, ultrasonically dispersing for 20-30 minutes, filtering, washing with anhydrous ethanol and then drying, and the mass ratio of lignin nanoparticles to cocoamidopropyl betaine is 1:0.2-0.3.

[0025] By adopting the above technical scheme, the addition of lignin nanoparticles enhances the liquid holding capacity of the foam liquid film, plays a role in supporting the liquid film, prevents the drainage process of the foam, slows down the drainage rate of the foam, and maintains the thickness of the foam film, which is not only beneficial to the enhancement of the foam properties, but also has a positive promoting effect on the stability of the foam under shear disturbance. The lignin nanoparticles and cocamidopropyl betaine have hydrogen bonding, which is beneficial to the formation and stability of the foam. It is not easy to break during stirring, and the foam size is uniform, so that the pore size of the concrete after molding is uniform. When subjected to external stress, it can better disperse the stress and improve the compressive strength.

[0026] In a second aspect, the present application provides a method for preparing an air-entraining polycarboxylate water-reducing agent, using the following technical solution: A method for preparing an air-entraining polycarboxylate water-reducing agent comprises the following steps: Mix the unsaturated polyether macromonomer and water, raise the temperature to 40-60°C, stir until completely dissolved, and prepare a primer solution for standby use. The amount of water used is 50-53wt% of the total amount of water; The unsaturated carboxylic acid or unsaturated carboxylic acid derivative, the air-entraining functional monomer and water are uniformly mixed to prepare liquid A, wherein the amount of water used is 8-12 wt % of the total amount of water used; The reducing agent, chain transfer agent and water are mixed and stirred evenly to prepare liquid B, wherein the amount of water used is 17-18wt% of the total amount of water used; the base material solution is heated to 35-40°C, an oxidant is added, and then liquid B is added dropwise, and liquid A is added dropwise after liquid B is added dropwise for 30s. After the addition is completed, the solution is kept warm for 60-120min, and then a neutralizing agent and water in an amount of 20-22wt% of the total amount of water are added, and the pH is adjusted to 5-7 to prepare an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%; or: Mix the unsaturated polyether macromonomer and water, raise the temperature to 40-60°C, stir until completely dissolved, and prepare a primer solution for standby use. The amount of water used is 50-53wt% of the total amount of water; The unsaturated carboxylic acid or unsaturated carboxylic acid derivative, the air-entraining functional monomer and water are uniformly mixed to prepare liquid A, wherein the amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative in liquid A is 90-100wt% of the total amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative, and the amount of water is 8-12wt% of the total amount of water; Mix the reducing agent, chain transfer agent and water, stir evenly to prepare liquid B, wherein the amount of reducing agent in liquid B is 28-30wt% of the total amount of reducing agent, and the amount of water is 17-18wt% of the total amount of water; An unsaturated carboxylic acid or an unsaturated carboxylic acid derivative, a reducing agent and an oxidizing agent are sequentially added to a base material solution at room temperature, and each addition is stirred for 3-5 minutes, and then B is added dropwise, and after 30 seconds of adding liquid B, liquid A is added dropwise. After the addition is completed, the solution is kept warm for 60-120 minutes, and then a neutralizing agent and water in an amount of 20-22wt% of the total amount of water are added, and the pH is adjusted to 5-7 to prepare an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%, wherein the amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative is 0-10wt% of the total amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative, the amount of the reducing agent is 70-72wt% of the total amount of the reducing agent, and the reducing agent concentration is 1%.

[0027] By adopting the above technical scheme, at room temperature, the temperature of the reaction base material is adjusted by partially using unsaturated carboxylic acids or unsaturated carboxylic acid derivatives and / or reducing agents, and each time a raw material is added, stirring is performed for three to five minutes to obtain a more uniform reaction solution. At a specific temperature, only the oxidant is first added to the base material solution. In addition, in both preparation methods, the dripping time of liquid B is controlled to be 30 seconds earlier than that of liquid A, which can accelerate the reaction and obtain higher production efficiency.

[0028] In summary, this application has the following beneficial effects: 1. Since the present application adopts an air-entraining functional monomer made by mixing maleic rosin and liquid alkali, and prepares a polycarboxylic acid water-reducing agent with an air-entraining effect with components such as a polyether macromonomer, an unsaturated carboxylic acid or its derivatives, the amount of bubbles introduced into the concrete is increased, and the bubbles are uniform, dense, and have good bubble persistence, reducing the generation of larger bubbles, thereby avoiding the addition of a defoaming agent, reducing the use of unnecessary admixtures, and can better improve the workability of concrete. In addition, there is no need to add an air-entraining agent separately to the concrete, avoiding the cumbersome operation caused by physically compounding an air-entraining agent and a water-reducing agent. DETAILED DESCRIPTION

[0029] The following examples further illustrate the present application in detail.

[0030] Preparation Example 1-4 of Functional Air Entraining Monomer Preparation Example 1: 100 g of maleic rosin was crushed, mixed with 36 g of liquid caustic soda with a concentration of 48%, put into a reactor, heated to 100° C., reacted for 2 hours, and after the reaction was completed, water was added to dilute to a solid content of 25%.

[0031] Preparation Example 2: 150 g of maleic rosin was crushed, mixed with 45 g of liquid caustic soda with a concentration of 48%, put into a reactor, heated to 125° C., reacted for 1 hour, and water was added to dilute to a solid content of 25%.

[0032] Preparation Example 3: 200 g of maleic rosin was crushed, mixed with 36 g of liquid caustic soda with a concentration of 48%, put into a reactor, heated to 100° C., reacted for 2 hours, and after the reaction was completed, water was added to dilute to a solid content of 25%.

[0033] Preparation Example 4: 50 g of maleic rosin was crushed, mixed with 36 g of liquid caustic soda with a concentration of 48%, put into a reactor, heated to 100° C., reacted for 2 hours, and after the reaction was completed, water was added to dilute to a solid content of 25%. Example

[0034] Embodiment 1: An air-entraining polycarboxylate water-reducing agent, the preparation method comprising the following steps: S1, add 340g of unsaturated polyether macromonomer and 300g of water into a four-necked flask, heat to 40°C, and stir until all dissolved to prepare a base material solution, wherein the unsaturated polyether macromonomer is methyl allyl polyoxyethylene ether; S2, 40g of unsaturated carboxylic acid, 15g of air-entraining type functional monomer and 50g of water were mixed and stirred to obtain liquid A, wherein the unsaturated carboxylic acid was acrylic acid, and the air-entraining type functional monomer was prepared by Preparation Example 1; 0.7g of reducing agent, 1.8g of chain transfer agent and 100g of water were mixed to obtain liquid B, wherein the reducing agent was L-ascorbic acid, and the chain transfer agent was mercaptopropionic acid; S3, the base material solution was heated to 40 ° C, 3.5 g of 27.5% hydrogen peroxide was added to the base material solution, stirred for 5 minutes, and then liquid B was added dropwise. After 30 seconds of liquid B, liquid A was added dropwise. The addition time of liquid A was controlled to be 150 minutes, and the addition time of liquid B was controlled to be 180 minutes. After the addition was completed, the temperature was kept for 120 minutes; S4. Add 25 g of a neutralizing agent and 120 g of water to the liquid obtained in S3, and adjust the pH to 7 to obtain an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%. The neutralizing agent is a 32% sodium hydroxide aqueous solution.

[0035] Embodiment 2: An air-entraining polycarboxylate water-reducing agent, the preparation method comprising the following steps: S1, add 340g of unsaturated polyether macromonomer and 300g of water into a four-necked flask, heat to 40°C, and stir until all dissolved to prepare a base material solution, wherein the unsaturated polyether macromonomer is methyl allyl polyoxyethylene ether; S2, 40g of unsaturated carboxylic acid, 15g of air-entraining type functional monomer and 50g of water were mixed and stirred to obtain liquid A, the unsaturated carboxylic acid was acrylic acid, the air-entraining type functional monomer was prepared by Preparation Example 2, 0.7g of reducing agent, 1.8g of chain transfer agent and 100g of water were mixed to obtain liquid B, the reducing agent was L-ascorbic acid, and the chain transfer agent was mercaptopropionic acid; S3, add 1.8g reducing agent and 3.5g 27.5% hydrogen peroxide to the bottom material solution at room temperature, stir for 5min each time adding one substance, start to add liquid B, add liquid A after 30s of adding liquid B, control the adding time of liquid A to be 120min, the adding time of liquid B to be 150min, after the addition is completed, keep warm for 120min, the reducing agent is 1% ferrous sulfate solution; S4. Add 25 g of a neutralizing agent and 120 g of water to the liquid obtained in step S3, and adjust the pH to 7 to obtain an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%. The neutralizing agent is a 32% sodium hydroxide aqueous solution.

[0036] Embodiment 3: An air-entraining polycarboxylate water-reducing agent, the preparation method comprising the following steps: S1, add 340g of unsaturated polyether macromonomer and 300g of water into a four-necked flask, heat to 40°C, and stir until all dissolved to prepare a base material solution, wherein the unsaturated polyether macromonomer is methyl allyl polyoxyethylene ether; S2, 36g of unsaturated carboxylic acid, 15g of air-entraining type functional monomer and 50g of water were mixed and stirred to obtain liquid A, the unsaturated carboxylic acid was acrylic acid, the air-entraining type functional monomer was prepared by Preparation Example 2, 0.7g of reducing agent, 1.8g of chain transfer agent and 100g of water were mixed to obtain liquid B, the reducing agent was L-ascorbic acid, and the chain transfer agent was mercaptopropionic acid; S3, to the room temperature base material solution, 4g unsaturated carboxylic acid, 1.8g reducing agent and 3.5g 27.5% hydrogen peroxide were added in sequence, each one was stirred for 5min, and liquid B was added dropwise, and liquid A was added dropwise after 30s of liquid B, and the addition time of liquid A was controlled to be 150min, and the addition time of liquid B was controlled to be 180min. After the addition was completed, the temperature was kept for 120min. The unsaturated carboxylic acid was acrylic acid, and the reducing agent was a 1% ferrous sulfate solution; S4. Add 25 g of a neutralizing agent and 120 g of water to the liquid obtained in step S3, and adjust the pH to 7 to obtain an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%. The neutralizing agent is a 32% sodium hydroxide aqueous solution.

[0037] Embodiment 4: An air-entraining polycarboxylate water-reducing agent, the preparation method comprising the following steps: S1, add 340g of unsaturated polyether macromonomer and 300g of water into a four-necked flask, heat to 40°C, and stir until all dissolved to prepare a base material solution, wherein the unsaturated polyether macromonomer is methyl allyl polyoxyethylene ether; S2, 35g of unsaturated carboxylic acid, 20g of air-entraining type functional monomer and 50g of water were mixed and stirred to obtain liquid A, the unsaturated carboxylic acid was acrylic acid, the air-entraining type functional monomer was prepared by Preparation Example 2, 0.7g of reducing agent, 1.8g of chain transfer agent and 100g of water were mixed to obtain liquid B, the reducing agent was L-ascorbic acid, and the chain transfer agent was mercaptopropionic acid; S3, add 1.8g reducing agent and 3.5g 27.5% hydrogen peroxide to the bottom material solution at room temperature, stir for 5min each time, start to add liquid B, add liquid A after 30s, control the addition time of liquid A to be 120min, and the addition time of liquid B to be 150min. After the addition is completed, keep warm for 120min. The reducing agent is 1% ferrous sulfate solution; S4. Add 25 g of a neutralizing agent and 120 g of water to the liquid obtained in step S3, and adjust the pH to 7 to obtain an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%. The neutralizing agent is a 32% sodium hydroxide aqueous solution.

[0038] Embodiment 5: An air-entraining polycarboxylate water-reducing agent, the preparation method comprising the following steps: S1, add 340g of unsaturated polyether macromonomer and 300g of water into a four-necked flask, heat to 40°C, and stir until all dissolved to prepare a base material solution, wherein the unsaturated polyether macromonomer is methyl allyl polyoxyethylene ether; S2, 30g of unsaturated carboxylic acid, 30g of air-entraining type functional monomer and 50g of water were mixed and stirred to obtain liquid A, the unsaturated carboxylic acid was acrylic acid, the air-entraining type functional monomer was prepared by Preparation Example 2, 0.7g of reducing agent, 1.8g of chain transfer agent and 100g of water were mixed to obtain liquid B, the reducing agent was L-ascorbic acid, and the chain transfer agent was mercaptopropionic acid; S3, add 1.8g reducing agent and 3.5g hydrogen peroxide with a concentration of 27.5% to the base material solution at room temperature in sequence, stir for 5min each time adding one, start to drop liquid B, add liquid A after 30s of dropwise addition of liquid B, control the dropwise addition time of liquid A to be 150min, and the dropwise addition time of liquid B to be 180min. After the dropwise addition is completed, keep warm for 120min. The reducing agent is a ferrous sulfate solution with a concentration of 1%; S4, add 25g neutralizing agent and 120g water to the liquid obtained in step S3, adjust the pH to 7, and obtain an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%. The neutralizing agent is a sodium hydroxide aqueous solution with a concentration of 32%.

[0039] Example 6: An air-entraining polycarboxylic acid water-reducing agent, which is different from Example 5 in that the air-entraining functional monomer is prepared from Preparation Example 3.

[0040] Example 7: An air-entraining polycarboxylic acid water-reducing agent, which is different from Example 5 in that the air-entraining functional monomer is prepared from Preparation Example 4.

[0041] Embodiment 8: An air-entraining polycarboxylic acid water-reducing agent, which differs from Embodiment 5 in that, in step S4, 3 g of nano-adjuvant is further added to the liquid obtained in step S3, and the preparation method of the nano-adjuvant is as follows: lignin nanoparticles are dispersed in deionized water, stirred at room temperature for 12 hours to form a uniformly dispersed mixed solution, treated at 300°C and 13MPa for 24 hours, filtered, and dried at 80°C. The lignin nanoparticles are selected from Jinan Shengquan Group Co., Ltd., and the model is SQOA-1; the heat-treated lignin nanoparticles are dispersed in deionized water to form a suspension with a concentration of 1 wt%, cocamidopropyl betaine is added, ultrasonically dispersed for 30 minutes, filtered, repeatedly washed with anhydrous ethanol for 4 times, and dried at a constant temperature of 60°C for 12 hours. The mass ratio of lignin nanoparticles to cocamidopropyl betaine is 1:0.3.

[0042] Embodiment 9: An air-entraining polycarboxylate water-reducing agent, which differs from Embodiment 5 in that, in step S4, 3 g of nano-adjuvant is further added to the liquid obtained in step S3. The preparation method of the nano-adjuvant is as follows: lignin nanoparticles are dispersed in deionized water, stirred at room temperature for 12 hours to form a uniformly dispersed mixed solution, treated at 300°C and 13 MPa for 24 hours, filtered, and dried at 80°C. The lignin nanoparticles are selected from Jinan Shengquan Group Co., Ltd., and the model is SQOA-1; the heat-treated lignin nanoparticles are dispersed in deionized water to form a suspension with a concentration of 1 wt%, cocamidopropyl betaine is added, ultrasonically dispersed for 30 minutes, filtered, repeatedly washed with anhydrous ethanol for 4 times, and dried at a constant temperature of 60°C for 12 hours. The mass ratio of lignin nanoparticles to cocamidopropyl betaine is 1:0.2.

[0043] Example 10: An air-entraining polycarboxylate water-reducing agent, which differs from Example 5 in that 3 g of nano-adjuvant is further added to the liquid obtained in step S3 in step S4. The preparation method of the nano-adjuvant is as follows: lignin nanoparticles are dispersed in deionized water, stirred at room temperature for 12 hours to form a uniformly dispersed mixed liquid, treated at 300°C and 13MPa for 24 hours, filtered, and dried at 80°C. The lignin nanoparticles are selected from Jinan Shengquan Group Co., Ltd., model SQOA-1.

[0044] Example 11: An air-entraining polycarboxylate water-reducing agent, which differs from Example 5 in that 3 g of nano-adjuvant is further added to the liquid obtained in step S3 in step S4. The preparation method of the nano-adjuvant is as follows: lignin nanoparticles are dispersed in deionized water to form a suspension with a concentration of 1 wt%, cocamidopropyl betaine is added, ultrasonic dispersion is performed for 30 min, suction filtration is performed, and the mixture is repeatedly washed with anhydrous ethanol for 4 times, and dried at a constant temperature of 60°C for 12 h. The mass ratio of lignin nanoparticles to cocamidopropyl betaine is 1:0.2.

[0045] Comparative Example Comparative Example 1: A water-reducing PCE polycarboxylate water-reducing agent, the preparation method is as follows: 340g of methyl allyl polyoxyethylene ether and 250g of water were added to a four-necked flask, heated to 40°C, stirred and dissolved completely, then 3.5g of 27.5% hydrogen peroxide was added, stirred for 5min, and then liquid B (a mixture of 0.7g L-ascorbic acid, 1.8g chain transfer agent mercaptopropionic acid and 100g water) was added dropwise. After 30s, liquid A (a mixture of 40g acrylic acid and 60g water) was added dropwise. The addition time of liquid A was 120min, and the addition time of liquid B was 150min. After the addition was completed, the mixture was kept warm for 120min. After the reaction was complete, 20g of 32% sodium hydroxide aqueous solution and 150g water were added to obtain a water-reducing PCE polycarboxylic acid water reducer.

[0046] Comparative Example 2: A polycarboxylic acid water reducer, which differs from Example 2 in that no air-entraining functional monomer is added, and the remaining proportions and preparation method are the same as those of Example 2.

[0047] Performance testing The water reducer was prepared according to the method in the above embodiment and comparative example, and the water reducer was subjected to the following performance tests: 1. Fluidity of pure paste: Mix cement, water reducing agent and water in proportion to form pure cement paste, and test it according to the relevant standards of GB / T8077-2012 "Test method for homogeneity of concrete admixtures", and record the test results in Table 3.

[0048] 2. Air content: The water reducer prepared in the embodiment and the comparative example was added to the concrete according to the amount in Table 1, and the commercially available defoamer (BZB-0023) and the commercially available polycarboxylate water reducer (model HPC-S-1) were used to prepare concrete according to the raw materials in Table 2. The air content of the concrete was detected according to the method in GB / T50080-2016 "Test method for performance of ordinary concrete mixtures", and the test results were recorded in Table 3.

[0049] 3. Compressive strength: Add the water reducer into the concrete according to the amount in Table 1, and test the compressive strength according to the method in GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete". The size of the compressive strength specimen is 100mm×100mm×100mm. The test results are recorded in Table 3.

[0050] 4. Foaming test: Weigh the calculated amount of the water reducer prepared in the embodiment or comparative example, place it in a 1000mL beaker, add water, and gently stir with a glass rod until the water reducer is evenly dispersed to prepare 300g of a water reducer solution with a solid content of 0.5%. Place the stirring rod of the electric stirrer in the middle of the beaker, adjust the tetrafluoroethylene stirring paddle blade so that the stirring blade is located in the lower part of the water reducer solution, turn on the electric stirrer, the stirrer speed is 1000r / min, stir for (60±1)s and immediately turn off the stirring. Observe and record the initial foam height in the beaker within 30s of stopping stirring, accurate to 1mm; let it stand for 30min after starting the timing from the end of stirring, and record the foam height again, accurate to 1mm. The test results are shown in Table 3.

[0051] Table 1 The proportion of concrete used in the test Table 2 Raw material ratio of concrete in control group 1 and control group 2 Table 3 Performance test results of concrete It can be seen from the data in Table 3 that the polycarboxylate water-reducing agent to which the air-entraining functional monomer is added in Examples 1-5 reduces the air content of the concrete without affecting the dispersibility, and effectively increases the compressive strength of the concrete. With the increase of the air-entraining functional monomer, the performance gradually becomes excellent. When the air-entraining functional monomer reaches a certain level, the performance tends to be stable.

[0052] Compared with Example 5, Examples 6-7 respectively use the air-entraining functional monomers prepared in Preparation Example 3 and Preparation Example 4, and it can be seen that the air-entraining effect and foam durability are reduced.

[0053] Compared with Example 5, Examples 8-9 further added lignin nanoparticles modified with a zwitterionic surfactant, and it can be seen that the foam stability is increased, the content of stable, uniform, and tiny bubbles in the concrete is improved, the fluidity of the cement paste is increased, and the workability is improved; in Examples 10 and 11, the lignin nanoparticles are respectively treated with heat and a zwitterionic surfactant, and it can be seen that the persistence of the bubbles is reduced.

[0054] The water reducing agent prepared with the raw materials in Comparative Example 1 was added to the cement paste. Compared with Example 1, the fluidity of the cement paste slowed down, the air content increased, and the foam disappeared quickly, which easily generated large bubbles with large volume and easy to break, affecting the strength of the concrete.

[0055] Compared with Example 2, in Comparative Example 2, no air-entraining functional monomer is added, and the prepared water reducer has a decreased effect of improving the fluidity of cement paste when used, and the bubble content is increased, and the bubble stability is poor.

[0056] Commercially available defoamers and commercially available water reducers are used to replace the air-entraining water reducer of the present application. It can be seen from the data in Table 3 that the use of defoamers reduces the air content in the concrete, the improvement of the fluidity of the concrete is insufficient, and the stability of the bubbles is poor. The use of polycarboxylate water reducers can improve the fluidity and flowability of cement paste, and various properties are similar to those in Example 1, indicating that the air-entraining polycarboxylate water reducer prepared in the present application can achieve the effects of air entrainment, water reduction, and enhancement, and no additional additives such as air entraining agents are required.

[0057] The polycarboxylate water-reducing agent can generate a large amount of foam after rapid stirring, indicating that the synthesized polycarboxylate water-reducing agent has a certain surface activity, and the initial foam height of Examples 1-5 is smaller than that of Comparative Examples 1-2. Because the upper layer of the foam is relatively unstable, the large foam disappears quickly within 30 seconds. The polycarboxylate water-reducing agent with air-entraining functional monomer can effectively inhibit the generation of large foam and quickly dissipate it, reducing the amount of harmful foam. The foam height after 30 minutes is relatively large, and the small foam in the lower layer can remain stable and is not easy to deform and rupture, which increases the stability of the beneficial bubbles. It can effectively improve the fluidity of the concrete slurry during mixing and improve the workability. The uniform and tiny bubbles in the concrete can improve the durability of the concrete.

[0058] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An air-entraining polycarboxylate water-reducing agent, characterized in that: The invention comprises the following raw materials in parts by weight: 320-380 parts of unsaturated polyether macromonomer, 10-30 parts of air-entraining functional monomer, 26-50 parts of unsaturated carboxylic acid or unsaturated carboxylic acid derivative, 1-4 parts of oxidant, 0.5-2 parts of reducing agent, 0.6-2.8 parts of chain transfer agent, 18-30 parts of neutralizer and 500-600 parts of water; The preparation method of the air-entraining functional monomer is as follows: crushing maleic rosin, mixing with 48% liquid caustic soda, heating to 100-125° C., keeping the temperature for reaction for 1-2 hours, and after the reaction is completed, adding water to dilute to a solid content of 23-25%.

2. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The mass ratio of the maleic rosin to 48% liquid caustic soda is 1-1.5:0.36-0.

45.

3. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The unsaturated polyether macromonomer is selected from at least one of methyl allyl alcohol polyoxyethylene ether, isopentanol polyoxyethylene ether and diethylene glycol polyoxyethylene ether.

4. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The unsaturated carboxylic acid is acrylic acid or methacrylic acid, and the unsaturated carboxylic acid derivative is at least one of maleic anhydride, methyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate and hydroxypropyl acrylate.

5. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The reducing agent is selected from at least one of L-ascorbic acid, sodium formaldehyde sulfoxylate and ferrous sulfate.

6. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The chain transfer agent is selected from at least one of sodium hypophosphite, thioglycolic acid, mercaptopropionic acid and mercaptoethanol.

7. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The oxidant is a 27.5% hydrogen peroxide solution or a 27.5% ammonium persulfate solution.

8. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The neutralizing agent is a sodium hydroxide solution with a concentration of 32%.

9. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The air-entraining polycarboxylate water-reducing agent is further added with 1-3 parts by weight of a nano auxiliary agent. The preparation method of the nano auxiliary agent is as follows: lignin nanoparticles are dispersed in deionized water to form a suspension, cocamidopropyl betaine is added, ultrasonic dispersion is performed for 20-30 minutes, suction filtration is performed, the suspension is washed with anhydrous ethanol and then dried, and the mass ratio of the lignin nanoparticles to the cocamidopropyl betaine is 1:0.2-0.

3.

10. The method for preparing the air-entraining polycarboxylate water-reducing agent according to any one of claims 1 to 9, characterized in that: The following steps are involved: Mix the unsaturated polyether macromonomer and water, raise the temperature to 40-60°C, stir until completely dissolved, and prepare a base material solution for standby use. The amount of water used is 50-53wt% of the total amount of water; The unsaturated carboxylic acid or unsaturated carboxylic acid derivative, the air-entraining functional monomer and water are uniformly mixed to prepare liquid A, wherein the amount of water used is 8-12wt% of the total amount of water used; Mix the reducing agent, chain transfer agent and water, stir evenly to prepare liquid B, the amount of water used is 17-18wt% of the total amount of water; The base material solution is heated to 35-40°C, an oxidant is added, and then B is added dropwise. After 30 seconds of adding B solution, A solution is added dropwise. After the addition is completed, the solution is kept warm for 60-120 minutes, and then a neutralizer and water in an amount of 20-22wt% of the total amount of water are added, and the pH is adjusted to 5-7 to obtain an air-entraining polycarboxylate water-reducing agent with a solid content of 40%; or: Mix the unsaturated polyether macromonomer and water, raise the temperature to 40-60°C, stir until completely dissolved, and prepare a base material solution for standby use. The amount of water used is 50-53wt% of the total amount of water; The unsaturated carboxylic acid or unsaturated carboxylic acid derivative, the air-entraining functional monomer and water are uniformly mixed to prepare liquid A, wherein the amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative in liquid A is 90-100wt% of the total amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative, and the amount of water is 8-12wt% of the total amount of water; Mix the reducing agent, chain transfer agent and water, stir evenly to prepare liquid B, wherein the amount of reducing agent in liquid B is 28-30wt% of the total amount of reducing agent, and the amount of water is 17-18wt% of the total amount of water; An unsaturated carboxylic acid or an unsaturated carboxylic acid derivative, a reducing agent and an oxidizing agent are sequentially added to a base material solution at room temperature, and each one is stirred for 3-5 minutes, and then liquid B is added dropwise, and liquid A is added dropwise after liquid B is added dropwise for 30 seconds. After the dropwise addition is completed, the solution is kept warm for 60-120 minutes, and then a neutralizing agent and water in an amount of 20-22wt% of the total amount of water are added, and the pH is adjusted to 5-7 to prepare an air-entraining polycarboxylic acid water-reducing agent with a solid content of 40%, the amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative is 0-10wt% of the total amount of the unsaturated carboxylic acid or the unsaturated carboxylic acid derivative, the amount of the reducing agent is 70-72wt% of the total amount of the reducing agent, and the reducing agent concentration is 1%.

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