A hydrophobic chain transfer agent, a preparation method thereof and application thereof in air entraining and viscosity reducing polycarboxylic acid water reducer

Abstract

The application provides a hydrophobic chain transfer agent, a preparation method thereof and application of the hydrophobic chain transfer agent in air entraining and viscosity reducing polycarboxylic acid water reducing agent, the hydrophobic chain transfer agent is prepared by esterification reaction of acid with sulfydryl and aliphatic alcohol; the air entraining and viscosity reducing polycarboxylic acid water reducing agent is prepared by using the prepared hydrophobic chain transfer agent, the main chain is capped, so that the HLB value of the main chain is reduced, the hydrophobic performance of the hydrophobic chain transfer agent is adjusted, the HLB value of the main chain can be controlled and adjusted, and the air entraining and viscosity reducing polycarboxylic acid water reducing agent with excellent air entraining performance and without affecting the strength of concrete is prepared. Moreover, the conversion rate of the polycarboxylic acid water reducing agent is more than 90%, the polydispersity coefficient is less than or equal to 1,75, the polydispersity coefficient is relatively small, and the molecular weight distribution is relatively narrow.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete admixtures, and particularly relates to a hydrophobic chain transfer agent, a preparation method thereof and application of the hydrophobic chain transfer agent in air-entraining and viscosity-reducing polycarboxylate superplasticizer. BACKGROUND

[0002] With the rapid development of concrete technology, concrete is more and more widely used in roads, bridges, dams and civil buildings, and the demand for concrete is increasing year by year in both national projects and civil projects. At the same time, the requirements for the performance of concrete in construction projects are gradually increasing, especially for special concrete such as ultra-high performance concrete and self-compacting concrete. The concrete not only requires good flowability, but also has low viscosity and high strength. However, in high-grade concrete, most of the sand and gravel materials are machine-made mountain sand, which results in higher viscosity of the concrete, leading to difficulties in mixing, pumping and construction of the concrete. This problem has become a difficult problem in the field of ready-mixed concrete.

[0003] Currently, a proper amount of air bubbles is introduced into concrete by adding air-entraining agents to improve the workability of fresh concrete and reduce the viscosity of the concrete. However, excessive use of air-entraining agents will introduce a large amount of large air bubbles, which will break and form pores after the concrete hardens, resulting in stress failure points and reducing the strength of the concrete. On the other hand, air-entraining agents have weak air-entraining performance in high-grade or high-powder-content concrete, and it is difficult to achieve the purpose of reducing the viscosity of the concrete. Therefore, it is difficult to solve the problem of high viscosity of concrete by simply using air-entraining agents, and industry personnel try to synthesize and prepare polycarboxylate superplasticizers with air-entraining function to solve this problem.

[0004] A viscosity-reducing superplasticizer and a preparation method thereof are disclosed in patent CN 114213602 A published on March 22, 2022. An unsaturated hydroxyalkyl ester and a fatty acid monomethyl ester are subjected to esterification to obtain an unsaturated hydrophobic functional monomer, and then the prepared hydrophobic functional monomer is copolymerized with a polyether macromonomer, an unsaturated acid, an unsaturated ester and the like in an aqueous solution to obtain a viscosity-reducing polycarboxylate superplasticizer. The patent mainly introduces a hydrophobic monomer into the main chain of the polycarboxylate superplasticizer to adjust the hydrophilic-lipophilic balance (HLB value) of the main chain, so that the polycarboxylate superplasticizer has certain air-entraining ability. However, the degree of participation of the hydrophobic monomer in the reaction in the aqueous solution is uncontrollable. SUMMARY

[0005] The purpose of the present application is to provide a hydrophobic chain transfer agent and a preparation method thereof, which is prepared by esterification of an acid with a mercapto group and an aliphatic alcohol.

[0006] Another objective of this invention is to provide an application of a hydrophobic chain transfer agent in air-entraining and viscosity-reducing polycarboxylate superplasticizers. This hydrophobic chain transfer agent, acting as a chain transfer agent, is used to prepare air-entraining and viscosity-reducing polycarboxylate superplasticizers. By end-capping the main chain, the HLB value of the main chain is reduced. By adjusting the strength of the hydrophobic properties of this hydrophobic chain transfer agent, the HLB value of the main chain can be controllably adjusted, thereby preparing an air-entraining and viscosity-reducing polycarboxylate superplasticizer with excellent air-entraining properties without affecting the strength of concrete. The reaction degree is successfully increased through various methods, including directly adding the hydrophobic chain transfer agent to the substrate for reaction, adjusting its dosage to several times or more than that of conventional hydrophilic chain transfer agents, and adding an emulsifier to further form "water-in-oil" micro-droplets of the hydrophobic chain transfer agent in the substrate to increase the reaction area. Furthermore, the synthesized polycarboxylate superplasticizer has a conversion rate of over 90%, a relatively small polydispersity index ≤1.75, and a narrow molecular weight distribution, reducing synthesis and production costs, increasing the stability of the synthesized product, and possessing good market application value.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for preparing a hydrophobic chain transfer agent includes the following steps:

[0009] Aliphatic alcohols, thiol-containing acids, and catalysts are mixed in a solvent and heated under reflux. After the reaction is complete, the reaction system is cooled to room temperature, the pH is adjusted to weakly acidic, and after stirring, the lower liquid is separated. The hydrophobic chain transfer agent is obtained by vacuum distillation.

[0010] The molar ratio of the aliphatic alcohol to the thiol-containing acid is 1:1 to 1:1.2;

[0011] The amount of catalyst used is 1% to 3% of the total molar amount of aliphatic alcohols and thiol-containing acids;

[0012] The mass ratio of the total mass of the aliphatic alcohol and the thiol-containing acid to the mass of the solvent is 0.5 to 1.5:1;

[0013] The aliphatic alcohol is one of the following: n-butanol, isobutanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, dodecanol, tetradecanol, hexadecylol, and octadecylol.

[0014] The thiol-containing acid is one of the following: thioglycolic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, 3-mercaptoisobutyric acid, 6-mercaptohexanoic acid, 8-mercaptooctanoic acid, 14-mercaptotetradecanoic acid, 16-mercaptohexadecanoic acid, 4-mercaptophenylacetic acid, and 4-mercaptobenzoic acid.

[0015] The catalyst is one or more of methanesulfonic acid, p-toluenesulfonic acid, hydrogen chloride, aluminum trichloride, and ferric chloride.

[0016] The solvent is one of toluene, cyclohexane, and N,N-dimethylformamide.

[0017] The heating and reflux reaction: the constant temperature of the reaction is 105℃~120℃, and the reaction time is 6h~8h.

[0018] The heating and reflux reaction involves starting the stirring and cooling circulating water, using an oil bath to heat to a constant temperature reflux state, and separating the water produced by the reaction from the reaction system through a water separator.

[0019] The adjustment of pH to weakly acidic means adjusting it to pH=5 using an aqueous sodium hydroxide solution;

[0020] After adjusting the pH, the mixture was stirred for 0.5 hours and the lower liquid was separated. The hydrophobic chain transfer agent was obtained by vacuum distillation.

[0021] This invention provides a hydrophobic chain transfer agent, prepared using the above method; the structural formula of the hydrophobic chain transfer agent is:

[0022] R1 is a secondary carbon, a tertiary carbon, or a benzene ring; R2 is a secondary carbon or a tertiary carbon; R3 is a primary carbon or a hydroxyl group; a is 1-15; b is 2-16.

[0023] This invention provides an application of a hydrophobic chain transfer agent in air-entrained, viscosity-reducing polycarboxylate superplasticizers. The hydrophobic chain transfer agent is used as a chain transfer agent in the preparation of air-entrained, viscosity-reducing polycarboxylate superplasticizers to end-cap the main chain.

[0024] The preparation method of the air-entraining viscosity-reducing polycarboxylate superplasticizer is as follows:

[0025] 1) Mix the unsaturated polyether monomer, hydrophobic chain transfer agent, oxidant, emulsifier and deionized water evenly to prepare the base solution; mix the unsaturated acid and deionized water evenly to prepare solution A; mix the reducing agent and deionized water evenly to prepare solution B.

[0026] 2) Simultaneously and uniformly add liquid A and liquid B to the base liquid. After the addition is complete, keep the mixture warm to react and obtain the gas-entraining and viscosity-reducing polycarboxylate superplasticizer.

[0027] The amount of deionized water in the base solution is 0.5-1.5 times the mass of the unsaturated polyether monomer;

[0028] The amount of deionized water used in solutions A and B should be controlled according to standard procedures, ensuring that the mass fraction of solid content in the product is between 0.4% and 0.6%.

[0029] In step 1), the mass ratio of the unsaturated polyether monomer, hydrophobic chain transfer agent, oxidant, emulsifier, unsaturated acid, and reducing agent is: 100-300: 2-30: 1-4: 0.1-2.0: 5-25: 0.2-1.5;

[0030] The unsaturated polyether monomer is one or a combination of several of the following: methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, 4-hydroxybutyl vinyl polyoxyethylene ether, and ethylene glycol monovinyl polyethylene glycol ether.

[0031] Preferably, the molecular weight of ethylene glycol monovinyl polyethylene glycol ether is 800-4000;

[0032] The hydrophobic chain transfer agent is one of the products with different molecular structures synthesized in this invention; its molar amount is 5-60% of the total molar amount of unsaturated polyether monomer and unsaturated acid.

[0033] The oxidant is one of ammonium persulfate, hydrogen peroxide, and tert-butanol peroxide.

[0034] The emulsifier is one or a combination of several of polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, sodium dodecyl sulfate, etc., and its amount is 1 to 8% of the mass of the hydrophobic chain transfer agent.

[0035] Preferably, the molecular weight of the polyoxyethylene dodecyl ether is 362-1198;

[0036] The unsaturated acid is one of acrylic acid, methacrylic acid, fumaric acid, and sodium allyl sulfonate.

[0037] The reducing agent is one or a combination of several of sodium formaldehyde sulfoxylate, ascorbic acid, and sodium bisulfite.

[0038] In steps 1) and 2), the temperature is controlled between 5 and 40°C.

[0039] In step 2), the dripping time of solution A and solution B is 0.5 to 2 hours; the dripping time of solution B is 10 to 20 minutes longer than that of solution A.

[0040] In step 2), the heat preservation reaction time is 0.5 to 1 hour.

[0041] This invention provides a novel method to reduce the HLB value of polycarboxylate superplasticizers, thereby enabling them to possess a certain air-entraining function and achieving the goal of reducing concrete viscosity without sacrificing concrete strength. This method synthesizes hydrophobic chain transfer agents with different HLB values. These chain transfer agents, during the synthesis of polycarboxylate superplasticizers, end-cap one end of the superplasticizer backbone, thus introducing a hydrophobic segment into the polycarboxylate superplasticizer backbone and reducing its HLB value. This invention can control the HLB value of polycarboxylate superplasticizers by synthesizing chain transfer agents with different carbon chain lengths and varying degrees of hydrophobicity. Figure 1 As shown, the polycarboxylate superplasticizer synthesized in this invention comprises a hydrophilic portion and a hydrophobic portion provided by a hydrophobic chain transfer agent. When dissolved in water, it can reduce the surface tension of the water and generate microbubbles. These microbubbles can reduce the shear stress generated inside the concrete during flow, resulting in a lubricating effect of "ball bearing effect," thereby reducing the viscosity of the concrete. Furthermore, when the generated bubbles are small, they do not leave obvious stress concentration points inside the hardened concrete, thus not affecting the later-stage strength of the concrete.

[0042] In the synthesis of polycarboxylate superplasticizer, a hydrophobic chain transfer agent was added to the substrate instead of component A or component B. Simultaneously, an emulsifier was added to form oil-in-water (O / W) micro-droplets in the substrate, increasing its surface area in contact with the aqueous solution. Furthermore, the amount of this emulsifier was increased several times the conventional amount, successfully solving the reactivity problem in the aqueous solution system. Experimental results show that the synthesized final product has excellent air-entraining properties, effectively addressing the high viscosity of concrete without reducing its hardened strength. Attached Figure Description

[0043] Figure 1 The structure of the polycarboxylate superplasticizer prepared by this invention when the unsaturated acid is acrylic acid is as follows: R1 is a secondary carbon, tertiary carbon, or benzene ring; R2 is a secondary carbon or tertiary carbon; R3 is a primary carbon or hydroxyl group; R4 is CH3- or H-; R5 is -CH2-, -CH2CH2-, -OCH2CH2-, or -OCH2CH2OCH2CH2-; a is 1-15; b is 2-16; d:c = 0.5-8:1; and e is 15-90. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below through embodiments.

[0045] The preparation method of the hydrophobic chain transfer agent provided by the present invention is as follows:

[0046] 1) Add the aliphatic alcohol, the thiol-containing acid, the catalyst, and the solvent to a three-necked flask equipped with a condenser, a water separator, and a stirrer. Place the flask in an oil bath.

[0047] 2) Turn on the stirring and cooling circulating water, turn on the oil bath to heat to a constant temperature reflux state, and separate the water produced by the reaction from the reaction system through the water separator. After the reaction has been carried out for a period of time, stop the heating reaction.

[0048] 3) After the reaction product is cooled to room temperature, a certain amount of sodium hydroxide aqueous solution is added to adjust the pH to 5. After stirring for 0.5 h, the lower liquid is separated and the hydrophobic chain transfer agent is obtained by vacuum distillation.

[0049] In the preparation method of hydrophobic chain transfer agents:

[0050] The molar ratio of the aliphatic alcohol to the thiol-containing acid is 1:1 to 1:1.2;

[0051] The amount of catalyst used is 1% to 3% of the total molar amount of aliphatic alcohols and thiol-containing acids;

[0052] The mass ratio of the total mass of the aliphatic alcohol and the thiol-containing acid to the mass of the solvent is 0.5 to 1.5:1;

[0053] The aliphatic alcohol is one of the following: n-butanol, isobutanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, dodecanol, tetradecanol, hexadecylol, and octadecylol.

[0054] The thiol-containing acid is one of the following: thioglycolic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, 3-mercaptoisobutyric acid, 6-mercaptohexanoic acid, 8-mercaptooctanoic acid, 14-mercaptotetradecanoic acid, 16-mercaptohexadecanoic acid, 4-mercaptophenylacetic acid, and 4-mercaptobenzoic acid.

[0055] The catalyst is one or more of methanesulfonic acid, p-toluenesulfonic acid, hydrogen chloride, aluminum trichloride, and ferric chloride.

[0056] The solvent is one of toluene, cyclohexane, and N,N-dimethylformamide.

[0057] The oil bath is heated to a constant temperature reflux state, with a constant temperature of 105℃~120℃ and a reaction time of 6h~8h.

[0058] The structural formula of the hydrophobic chain transfer agent is:

[0059] R1 is a secondary carbon, a tertiary carbon, or a benzene ring; R2 is a secondary carbon or a tertiary carbon; R3 is a primary carbon or a hydroxyl group; a is 1-15; b is 2-16.

[0060] The hydrophobic chain transfer agent prepared according to this invention is used to prepare an air-entraining, viscosity-reducing polycarboxylate superplasticizer. The specific preparation process is as follows:

[0061] S1. Weigh a certain amount of unsaturated polyether monomer, hydrophobic chain transfer agent, oxidant, emulsifier and deionized water and mix them evenly to make a base solution. Pour the mixture into a three-necked flask, fix the three-necked flask on an iron stand, connect a cantilever stirrer to the top and place it in a constant temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh a certain amount of unsaturated acid and deionized water and mix them evenly to make solution A. Weigh a certain amount of reducing agent and deionized water and mix them evenly to make solution B.

[0062] S2. Start the stirrer and constant temperature water bath to maintain a constant temperature. Add solutions A and B dropwise at a uniform rate to the three-necked flask containing the base solution within a certain time period to start the aqueous solution free radical polymerization reaction. The time of this process is controlled by instruments such as an automatic dropper or a peristaltic pump.

[0063] S3. After liquids A and B have been added, continue to keep warm and stir for a certain period of time, then stop stirring and cool the synthesized product to room temperature to obtain the target product of this invention.

[0064] The unsaturated polyether monomers, hydrophobic chain transfer agents, oxidizing agents, emulsifiers, unsaturated acids, and reducing agents are prepared according to the following parts by weight:

[0065] Unsaturated polyether monomer: 100-300 parts;

[0066] Hydrophobic chain transfer agent: 2-30 parts;

[0067] Oxidizing agent: 1-4 parts;

[0068] Emulsifier: 0.1–2.0 parts;

[0069] Unsaturated acids: 5-25 parts;

[0070] Reducing agent: 0.2–1.5 parts;

[0071] The unsaturated polyether monomer is one or a combination of several of the following: methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, 4-hydroxybutyl vinyl polyoxyethylene ether, and ethylene glycol monovinyl polyethylene glycol ether.

[0072] The hydrophobic chain transfer agent is one of the products with different molecular structures synthesized in this invention. Its molar amount is 5-60% of the total molar amount of the unsaturated polyether monomer and the unsaturated acid.

[0073] Preferably, the molecular weight of ethylene glycol monovinyl polyethylene glycol ether is 800-4000;

[0074] The oxidant is one of ammonium persulfate, hydrogen peroxide, and tert-butanol peroxide.

[0075] The emulsifier is one or a combination of several of polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, sodium dodecyl sulfate, etc. Its dosage is 1-8% of the mass of the hydrophobic chain transfer agent;

[0076] The molecular weight of the polyoxyethylene dodecyl ether is 362-1198;

[0077] The unsaturated acid is one of acrylic acid, methacrylic acid, fumaric acid, allyl sulfonic acid, etc.

[0078] The reducing agent is one or a combination of several of sodium formaldehyde sulfoxylate, ascorbic acid, sodium bisulfite, etc.

[0079] In the air-entrained viscosity-reducing polycarboxylate superplasticizer, the constant temperature of the constant temperature water bath is 5-40℃.

[0080] The dripping time for solutions A and B is 0.5–2 hours; the dripping time for solution B is 10–20 minutes longer than that for solution A.

[0081] After adding solutions A and B, the incubation time is 0.5 to 1 hour.

[0082] The following are several specific embodiments of the present invention:

[0083] Preparation of hydrophobic chain transfer agent CTA1:

[0084] According to the following mass ratios: 74 parts n-butanol, 120 parts 3-mercaptopropionic acid, 4 parts p-toluenesulfonic acid, and 300 parts toluene were added to a three-necked flask equipped with a condenser, a water separator, and a stirrer. The flask was placed in an oil bath. Stirring and cooling water circulation were started, and the oil bath was heated to 105°C to initiate the reaction. The water produced during the reaction was separated from the reaction system using the water separator. After 8 hours of reaction, heating was stopped. After the reaction product cooled to room temperature, a certain amount of 30% sodium hydroxide aqueous solution was added to adjust the pH to 5. After stirring for 0.5 hours, the lower layer liquid was separated, and the hydrophobic chain transfer agent CTA1 was obtained by vacuum distillation. Its molecular weight was 162 g / mol, and its structural formula was: a = 1, b = 2, R1 is -CH2-, R2 is -CH2-, and R3 is -CH3;

[0085] Preparation of hydrophobic chain transfer agent CTA2:

[0086] According to the following mass proportions: 186 parts dodecanol, 120 parts 3-mercaptopropionic acid, 4 parts p-toluenesulfonic acid, and 300 parts toluene were added to a three-necked flask equipped with a condenser, a water separator, and a stirrer. The flask was placed in an oil bath. Stirring and cooling water circulation were started, and the oil bath was heated to 105°C to initiate the reaction. The water produced during the reaction was separated from the reaction system using the water separator. After 8 hours of reaction, heating was stopped. After the reaction product cooled to room temperature, a certain amount of 30% sodium hydroxide aqueous solution was added to adjust the pH to 5. After stirring for 0.5 hours, the lower layer liquid was separated, and the hydrophobic chain transfer agent CTA2 was obtained by vacuum distillation. Its molecular weight was 274 g / mol, and its structural formula was: a = 1, b = 10, R1 is -CH2-, R2 is -CH2-, and R3 is -CH3;

[0087] Preparation of hydrophobic chain transfer agent CTA3:

[0088] According to the following mass proportions: 270 parts octadecyl alcohol, 120 parts 3-mercaptopropionic acid, 4 parts p-toluenesulfonic acid, and 300 parts toluene were added to a three-necked flask equipped with a condenser, a water separator, and a stirrer. The flask was placed in an oil bath. Stirring and cooling water circulation were started, and the oil bath was heated to 105°C to initiate the reaction. The water produced during the reaction was separated from the reaction system using the water separator. After 8 hours of reaction, heating was stopped. After the reaction product cooled to room temperature, a certain amount of 30% sodium hydroxide aqueous solution was added to adjust the pH to 5. After stirring for 0.5 hours, the lower layer liquid was separated, and the hydrophobic chain transfer agent CTA3 was obtained by vacuum distillation. Its molecular weight was 358 g / mol, and its structural formula was: a = 1, b = 16, R1 is -CH2-, R2 is -CH2-, and R3 is -CH3;

[0089] Example 1

[0090] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0091] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 4.6 parts of CTA1, 2 parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. Fix the three-necked flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix thoroughly, and prepare solution B. Start the stirrer and the constant temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to begin the aqueous solution free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0092] Example 2

[0093] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0094] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 7.8 parts of CTA2 (equimolar amount of CTA1 in Example 1), 2 parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix them thoroughly, and pour them into a three-necked flask. The three-necked flask is fixed to an iron stand, with a cantilever stirrer connected to the top and a constant temperature water bath placed below. A temperature sensor is inserted into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix them thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix them thoroughly, and prepare solution B. Start the stirrer and the constant temperature water bath, and maintain the temperature at a constant 25°C. Liquids A and B were added dropwise into a three-necked flask at a uniform rate over 80 min and 90 min, respectively, to initiate the aqueous free radical polymerization reaction. After the addition of liquids A and B was completed, the mixture was kept warm and stirred for another 40 min. Then, stirring was stopped and the synthesized product was cooled to room temperature.

[0095] Example 3

[0096] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0097] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 10 parts of CTA3 (equimolar amount of CTA1 in Example 1), 2 parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix them thoroughly, and pour them into a three-necked flask. The three-necked flask is fixed to an iron stand, with a cantilever stirrer connected to the top and a constant temperature water bath placed below. A temperature sensor is inserted into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix them thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix them thoroughly, and prepare solution B. Start the stirrer and the constant temperature water bath, and maintain the temperature at a constant 25°C. Liquids A and B were added dropwise into a three-necked flask at a uniform rate over 80 min and 90 min, respectively, to initiate the aqueous free radical polymerization reaction. After the addition of liquids A and B was completed, the mixture was kept warm and stirred for another 40 min. Then, stirring was stopped and the synthesized product was cooled to room temperature.

[0098] Example 4

[0099] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0100] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 12 parts of CTA3, 2 parts of 30% hydrogen peroxide solution, 0.36 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. Fix the three-necked flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant-temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix thoroughly, and prepare solution B. Start the stirrer and the constant-temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to begin the aqueous free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0101] Example 5

[0102] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0103] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 14 parts of CTA3, 2 parts of 30% hydrogen peroxide solution, 0.42 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. Fix the three-necked flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix thoroughly, and prepare solution B. Start the stirrer and the constant temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to begin the aqueous solution free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0104] Example 6

[0105] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0106] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 14 parts of CTA3, 2 parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. Fix the three-necked flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant-temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix thoroughly, and prepare solution B. Start the stirrer and the constant-temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to begin the aqueous free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0107] Example 7

[0108] A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, specifically comprising:

[0109] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 14 parts of CTA3, 2 parts of 30% hydrogen peroxide solution, 0.18 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. Fix the three-necked flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant-temperature water bath below. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water, mix thoroughly, and prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water, mix thoroughly, and prepare solution B. Start the stirrer and the constant-temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to begin the aqueous free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0110] Comparative Example 1

[0111] A method for preparing a polycarboxylate superplasticizer, specifically comprising:

[0112] Weigh 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 2 parts of 30% hydrogen peroxide solution, and 200 parts of deionized water, mix thoroughly, and pour into a three-necked flask. The three-necked flask is fixed to an iron stand, with a cantilevered stirrer connected to the top and the bottom placed in a constant temperature water bath. A temperature sensor is inserted into one neck to record the synthesis temperature. Weigh 15 parts of acrylic acid... 0.8 parts of mercaptopropionic acid Mix 0.5 parts of sodium formaldehyde sulfoxylate with 20 parts of deionized water to prepare solution A; weigh out 0.5 parts of sodium formaldehyde sulfoxylate and mix with 20 parts of deionized water to prepare solution B; start the stirrer and the constant temperature water bath, and maintain the temperature at a constant 25℃. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min respectively to start the aqueous solution free radical polymerization reaction; after the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0113] Comparative Example 2

[0114] A method for preparing a polycarboxylate superplasticizer, specifically comprising:

[0115] Weigh out 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400. 3 parts of mercaptopropionic acidMix 2 parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water in an equimolar amount of CTA1 (as in Example 1), pour the mixture into a three-necked flask, fix the flask to an iron stand, connect a cantilever stirrer to the top, and place it in a constant temperature water bath. Insert a temperature sensor into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water and mix them evenly to prepare solution A. Weigh 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water and mix them evenly to prepare solution B. Start the stirrer and the constant temperature water bath, and maintain the temperature at a constant 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 min and 90 min, respectively, to begin the aqueous solution free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring at the constant temperature for 40 min, then stop stirring and cool the synthesized product to room temperature.

[0116] Comparative Example 3

[0117] A method for preparing a polycarboxylate superplasticizer, specifically comprising:

[0118] Weigh out 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400. 2 parts of CTA3, Two parts of 30% hydrogen peroxide solution, 0.3 parts of polyoxyethylene dodecyl ether with an average molecular weight of 683, and 200 parts of deionized water were mixed thoroughly and poured into a three-necked flask. The three-necked flask was fixed to an iron stand, with a cantilever stirrer connected to the top and a constant temperature water bath placed below. A temperature sensor was inserted into one end to record the synthesis temperature. 15 parts of acrylic acid and 20 parts of deionized water were weighed and mixed thoroughly to prepare solution A. 0.5 parts of sodium formaldehyde bisulfite and 20 parts of deionized water were weighed and mixed thoroughly to prepare solution B. The stirrer and the constant temperature water bath were started and the temperature was kept constant at 25°C. Solutions A and B were added dropwise to the three-necked flask at a uniform rate over 80 min and 90 min, respectively, to begin the aqueous solution free radical polymerization reaction. After the addition of solutions A and B was completed, the mixture was stirred and kept at the same temperature for 40 min. Then, the stirring was stopped and the synthesized product was cooled to room temperature.

[0119] Comparative Example 4

[0120] A method for preparing a polycarboxylate superplasticizer, specifically comprising:

[0121] Weigh out 200 parts of ethylene glycol monovinyl polyethylene glycol ether with an average molecular weight of 2400, 14 parts of CTA3, and 2 parts of 30% hydrogen peroxide solution. 0 parts of polyoxyethylene dodecyl etherMix 200 parts of acrylic acid with 200 parts of deionized water until homogeneous, then pour the mixture into a three-necked flask. The three-necked flask is fixed to an iron stand, with a cantilevered stirrer connected to the top and the flask placed in a constant-temperature water bath below. A temperature sensor is inserted into one end to record the synthesis temperature. Weigh 15 parts of acrylic acid and 20 parts of deionized water and mix them until homogeneous to prepare solution A. Weigh 0.5 parts of sodium formaldehyde sulfoxylate and 20 parts of deionized water and mix them until homogeneous to prepare solution B. Start the stirrer and the constant-temperature water bath, maintaining a constant temperature of 25°C. Add solutions A and B dropwise to the three-necked flask at a uniform rate over 80 minutes and 90 minutes respectively, initiating the aqueous solution free radical polymerization reaction. After the addition of solutions A and B is complete, continue stirring and maintaining the temperature for 40 minutes. Stop stirring and cool the synthesized product to room temperature.

[0122] The molecular weight of the above 7 example samples and 4 comparative sample samples was tested, and the test results are shown in Table 1.

[0123] According to the national standard GB 8076-2008 "Concrete Admixtures", the performance of C60 concrete was tested on the above 7 example samples and 3 comparative sample samples. All groups of tests were conducted with the same refractory-to-solid admixture, which was 0.15% of the mass of concrete cementitious materials. The test results are shown in Table 2.

[0124] Table 1. Molecular weight test results

[0125]

[0126] Table 2. Test Results for Performance Evaluation of C60 Concrete

[0127]

[0128]

[0129] Comparative Examples 1-3 used equimolar amounts of CAT1, CAT2, and CAT3 as chain transfer agents, respectively. As the carbon chain length of the chain transfer agent increased, its hydrophobicity increased, resulting in a greater decrease in the HLB value of the synthesized polycarboxylate superplasticizer (the longer the polar chain segment, the lower the HLB value). Table 1 shows no significant change in molecular weight and molecular weight distribution. However, Table 2 shows that as the hydrophobicity of the chain transfer agent increased, the collapse time decreased, and the gas content increased. This indicates that the synthesized chain transfer agents with different hydrophobicities affected the performance of the polycarboxylate superplasticizer; the stronger the hydrophobicity, the better the gas-entraining performance of the polycarboxylate superplasticizer, and the better its viscosity-reducing effect.

[0130] Compared to Example 1 and Comparative Example 2, mercaptopropionic acid, unlike CAT1, does not contain hydrophobic groups, so it almost entirely participates in the synthesis reaction. Table 1 shows that its synthesized product has a low molecular weight and a wide molecular distribution. Table 2 shows that the product has a low water reduction rate and no gas-entraining properties. This demonstrates that introducing hydrophobic groups into the chain transfer agent according to the process conditions of this invention is essential, as it not only affects the chain transfer agent's ability to participate in the reaction but also influences the gas-entraining properties of the final product.

[0131] Comparing Examples 3-5, the amount of CAT3 hydrophobic chain transfer agent used gradually increased. Table 1 shows that the molecular weight gradually decreased, proving that the hydrophobic chain transfer agent participated in the reaction and played a role in controlling the molecular weight. Table 2 shows a decrease in collapse time and an increase in gas content, demonstrating that with the increase in the amount of hydrophobic chain transfer agent, the gas-entraining performance and viscosity-reducing performance of the polycarboxylate superplasticizer improved.

[0132] Comparative Example 3 and Comparative Example 3, the amounts of CAT3 used were 10 parts by mass and 2 parts by mass, respectively, representing 9.58% and 1.9% of the total molar amounts of the unsaturated polyether monomer and the unsaturated acid. The sample synthesized in Comparative Example 3 had a very high molecular weight and, as shown in Table 2, had lost its water-reducing ability. This indicates that the amount of hydrophobic chain transfer agent used in the implementation of this invention must be within the range described in this invention.

[0133] Comparative Examples 5-7 show that the emulsifier dosage was reduced while keeping the CAT3 dosage constant. As the emulsifier dosage decreased, the molecular weight increased significantly. Simultaneously, the dispersion performance of the synthesized polycarboxylate superplasticizer decreased severely, the slump time increased, and the gas content decreased. This demonstrates that in the absence of an emulsifier, the amount of hydrophobic chain transfer agent participating in the reaction is reduced, thereby decreasing its impact on the HLB value of the polycarboxylate superplasticizer. Adding an appropriate amount of emulsifier is a necessary condition for the hydrophobic chain transfer agent to participate in the reaction.

[0134] Compared to Examples 5-7, Comparative Example 4, without the addition of emulsifier, produced a jelly-like gel product. This demonstrates that without the addition of emulsifier, the hydrophobic chain transfer agent is unlikely to participate in the chain transfer reaction and thus fails to regulate the molecular weight. Adding an appropriate amount of emulsifier according to this invention is a necessary condition for obtaining the target product.

[0135] Comparing Examples 1-7 with Comparative Example 1 (which uses a conventional method for synthesizing polycarboxylate superplasticizer), the data in Table 2 shows that all examples exhibit good water-reducing and dispersing properties, while also showing a decrease in slump time and an increase in air content. The 28-day compressive strength is essentially the same as that of the comparative example, proving that the air bubbles introduced in the examples do not affect the later-stage strength of the concrete, indicating that the bubble size is relatively small. Examples 1-7 all possess certain air-entraining properties, which can reduce concrete viscosity while ensuring that the concrete strength is not affected, thus achieving the objective of this invention.

[0136] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing an air-entraining, viscosity-reducing polycarboxylate superplasticizer, characterized in that, The preparation method is as follows: 1) Mix the unsaturated polyether monomer, hydrophobic chain transfer agent, oxidant, emulsifier and deionized water evenly to prepare the base solution; mix the unsaturated acid and deionized water evenly to prepare solution A; mix the reducing agent and deionized water evenly to prepare solution B. 2) Simultaneously and uniformly add liquid A and liquid B to the base liquid. After the addition is complete, keep the mixture warm for reaction to obtain an air-entraining and viscosity-reducing polycarboxylate superplasticizer. In step 1), the mass ratio of the unsaturated polyether monomer, hydrophobic chain transfer agent, oxidant, emulsifier, unsaturated acid, and reducing agent is: 100-300: 2-30: 1-4: 0.1-2.0: 5-25: 0.2-1.5; The hydrophobic chain transfer agent is selected from: , or ; The unsaturated polyether monomer is selected from one of methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, 4-hydroxybutyl vinyl polyoxyethylene ether or ethylene glycol monovinyl polyethylene glycol ether. The oxidant is selected from one of ammonium persulfate, hydrogen peroxide, or tert-butanol peroxide; The emulsifier is selected from polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, or sodium dodecyl sulfate; The unsaturated acid is selected from one of acrylic acid, methacrylic acid, fumaric acid, or sodium allyl sulfonate; The reducing agent is selected from sodium formaldehyde sulfoxylate, ascorbic acid, or sodium bisulfite.

2. The air-entraining, viscosity-reducing polycarboxylate superplasticizer prepared according to the preparation method described in claim 1.

Images