Gemini imidazoline functional monomer, imidazoline type polycarboxylate water reducer and preparation method

Abstract

The invention discloses a gemini imidazoline functional monomer, an imidazoline type polycarboxylate water reducer and a preparation method. By preparing a symmetrical double-chain imidazoline functional monomer and grafting it on the side chain of the polycarboxylate water reducer molecule, the steric hindrance of the polycarboxylate water reducer is increased, the dispersibility of cement particles is improved, and the water reduction rate is increased. Due to the grafting of the gemini imidazoline functional group, it can preferentially adsorb montmorillonite in sand in concrete, avoid adsorption of the polycarboxylate polyether side chain, significantly improve the anti-mud and collapse protection effects of the polycarboxylate water reducer, and at the same time introduce a sulfonic acid group in the quaternary ammonium salt reaction to improve the adsorption performance of the polycarboxylate water reducer and increase the water reduction rate. Therefore, the invention solves the problems of poor workability, high dosage and large loss of conventional polycarboxylate water reducers when applied to artificial and inferior sand and stone materials with high mud content, has a strong anti-mud effect, and greatly reduces the dosage of the polycarboxylate water reducer, which plays a role in reducing costs, increasing efficiency, energy saving and environmental protection.

Description

Technical Field

[0001] The invention relates to the field of concrete admixtures, and in particular to an imidazoline type polycarboxylate water reducer. Background Art

[0002] Compared with traditional water reducers, polycarboxylate water reducers have the advantages of simple production process, high water reduction rate, low slump loss, small shrinkage rate, and green environmental protection. They are the most widely used admixtures in current concrete admixtures. However, with the continuous development of the current construction industry, the demand for sand and stone materials is increasing, and natural high-quality sand and stone are slowly being replaced by artificial and inferior sand and stone. The mud content in inferior sand and stone increases. The polycarboxylate water reducers currently used on the market are applied to sand and stone materials with high mud content, showing problems such as poor concrete workability, high dosage, and large losses. Therefore, how to improve the mud resistance of polycarboxylate water reducers is an urgent problem to be solved. Providing a mud-resistant polycarboxylate water reducer is of great significance to the development of concrete admixtures and the concrete industry.

[0003] Patent No. CN113788917A discloses an anti-mud functional monomer, an anti-mud type polycarboxylate water-reducing agent and a preparation method, which increases steric hindrance by introducing a coupling agent and an unsaturated aromatic group into the molecular chain of the polycarboxylate water-reducing agent. However, the coupling agent has a poor anti-mud effect, and increasing the steric hindrance only increases the water reduction rate in an apparent manner, and has no substantial effect on anti-mud.

[0004] Patent No. CN114380529A discloses an anti-mud polycarboxylate water-reducing agent and a preparation method thereof, which uses triethylene glycol to partially replace unsaturated polyether monomers grafted on the molecular chain of the polycarboxylate water-reducing agent, increases the polar end of the polycarboxylate water-reducing agent, and utilizes the polarity and small molecular characteristics of triethylene glycol in the polycarboxylate water-reducing agent to dissolve the mud and adsorb on the surface of the mud, thereby offsetting the adsorption of the mud on both ends of the polycarboxylate water-reducing agent, achieving the anti-mud effect. However, the essence of this method is to absorb mud by consuming triethylene glycol, and the anti-mud performance of the polycarboxylate water-reducing agent cannot achieve the expected effect. Summary of the invention

[0005] The invention provides a gemini imidazoline functional monomer, an imidazoline type polycarboxylate water reducer and a preparation method, thereby solving the technical problems in the background technology.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A gemini imidazoline functional monomer, the chemical structure of which is as follows:

[0008]

[0009] Wherein R1 is one of C17H33 and C15H29.

[0010] The present invention also provides a method for preparing the above-mentioned gemini imidazoline functional monomer, comprising the following steps:

[0011] (1) Amidation reaction: unsaturated fatty acid is placed in a 1000 mL three-necked flask, a magnetic bar is added, a water separator and a serpentine condenser are installed, toluene is added as a water-carrying agent, and α-Al2O3 is added as a catalyst. The temperature of the oil bath is heated to 140-150°C and stirred continuously. Triethylenetetramine is added to the flask at a uniform rate within 0.5 h using a dropper. After condensation and reflux reaction for 2 h, an amide intermediate is obtained.

[0012] (2) Cyclization reaction: slowly heat the amide intermediate in step (1) to 180-210°C, install a water separator, and maintain the temperature for 6 hours until no more water is generated in the water separator. Use a vacuum distillation device instead, and use an oil bath to maintain the reaction temperature at 140-150°C for 2 hours to separate toluene, and finally obtain an imidazoline intermediate;

[0013] (3) Quaternization reaction: The imidazoline intermediate in step (2) is cooled to 80-90° C., a quaternizing agent is added to the imidazoline intermediate to carry out a quaternization reaction, the stirring speed is increased, the reaction is stirred continuously for 4-5 hours, and then recrystallized with acetone for multiple times to finally obtain a gemini imidazoline functional monomer.

[0014] Furthermore, the unsaturated fatty acid in step (1) is one of 9-hexadecenoic acid and 9-octadecenoic acid, the molar ratio of the unsaturated fatty acid to triethylenetetramine is 2:1-1.5, the amount of water-carrying agent toluene is 25wt.% of the total reaction amount, and the amount of catalyst α-Al2O3 is 1.5wt.% of the total reaction amount.

[0015] Furthermore, the quaternizing agent in step (3) is sodium 3-chloro-2-hydroxypropanesulfonate, and the molar ratio of triethylenetetramine to sodium 3-chloro-2-hydroxypropanesulfonate is 1:1-1.2.

[0016] The present invention also provides an imidazoline type polycarboxylate water reducer prepared by using the above-mentioned gemini imidazoline functional monomer, and the chemical structural formula is as follows:

[0017]

[0018] Wherein, X, Y, and Z are the number of chain segments of the copolymer repeating unit; M is a hydrogen atom or an alkali metal atom; n is the degree of polymerization of ethylene oxide, n=55 to 70; and a is C5H10 or C7H14.

[0019] The present invention also provides a formula for preparing the above-mentioned imidazoline type polycarboxylic acid water-reducing agent, comprising the following components by weight: 300-450 parts of unsaturated polyether monomer, 28-35 parts of unsaturated acid, 10-25 parts of imidazoline functional monomer, 1.5-5.0 parts of initiator, 0.3-2.5 parts of reducing agent, 1.2-5.5 parts of chain transfer agent, and 340-510 parts of water.

[0020] Furthermore, the unsaturated polyether monomer is one or two of methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, and ethylene glycol monovinyl polyoxyethylene ether; the unsaturated acid is one or two of acrylic acid, methacrylic acid, and maleic anhydride; the oxidant is any one of hydrogen peroxide, ammonium persulfate, and potassium persulfate, or a mixture of several of them; the reducing agent is one or two of L-ascorbic acid, bleaching agent, and E51; the chain transfer agent is one or two of thioglycolic acid, 3-mercaptopropionic acid, mercaptoethanol, and sodium hypophosphite.

[0021] The present invention also provides a method for preparing an imidazoline type polycarboxylate water-reducing agent using the formula of the above-mentioned imidazoline type polycarboxylate water-reducing agent, comprising the following steps: dissolving an unsaturated polyether monomer and a chain transfer agent in water, adding an initiator at 20±2° C., stirring evenly, dripping an aqueous solution of an unsaturated acid and an imidazoline functional monomer at a uniform speed within 50 minutes, and dripping an aqueous solution of a reducing agent at a uniform speed within 60 minutes, and maintaining the temperature for 60 minutes after the dripping is completed, thereby obtaining the imidazoline type polycarboxylate water-reducing agent.

[0022] The present invention is beneficial in that:

[0023] 1. The present invention prepares a symmetrical double-chain imidazoline functional monomer and grafts it onto the side chain of the polycarboxylate water-reducing agent molecule, thereby increasing the steric hindrance of the polycarboxylate water-reducing agent, improving the dispersibility of cement particles, and increasing the water reduction rate.

[0024] 2. The polycarboxylate water-reducing agent prepared by the present invention can preferentially adsorb montmorillonite in sand in concrete due to the grafting of gemini imidazoline functional groups, avoiding the adsorption of polycarboxylate polyether side chains, significantly improving the anti-mud and collapse-preserving effects of the polycarboxylate water-reducing agent, and at the same time, introducing sulfonic acid groups in the quaternary ammonium salt reaction to improve the adsorption performance of the polycarboxylate water-reducing agent and increase the water reduction rate. Therefore, the present invention solves the problems of poor workability, high dosage and large loss of conventional polycarboxylate water-reducing agents when applied to artificial and inferior sand and stone materials with high mud content.

[0025] 3. The imidazoline polycarboxylate water-reducing agent prepared by the present invention has a strong anti-mud effect, which greatly reduces the dosage of the polycarboxylate water-reducing agent, plays a role in reducing costs, increasing efficiency, saving energy and protecting the environment. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] The gemini imidazoline functional monomer in the present invention has the following chemical structural formula:

[0028]

[0029] Wherein R1 is one of C17H33 and C15H29.

[0030] The preparation method of the gemini imidazoline functional monomer comprises the following steps:

[0031] (1) Amidation reaction: unsaturated fatty acid is placed in a 1000 mL three-necked flask, a magnetic bar is added, a water separator and a serpentine condenser are installed, toluene is added as a water-carrying agent, and α-Al2O3 is added as a catalyst. The temperature of the oil bath is heated to 140-150°C and stirred continuously. Triethylenetetramine is added to the flask at a uniform rate within 0.5 h using a dropper. After condensation and reflux reaction for 2 h, an amide intermediate is obtained.

[0032] (2) Cyclization reaction: slowly heat the amide intermediate in step (1) to 180-210°C, install a water separator, and maintain the temperature for 6 hours until no more water is generated in the water separator. Use a vacuum distillation device instead, and use an oil bath to maintain the reaction temperature at 140-150°C for 2 hours to separate toluene, and finally obtain an imidazoline intermediate;

[0033] (3) Quaternization reaction: The imidazoline intermediate in step (2) is cooled to 80-90° C., a quaternizing agent is added to the imidazoline intermediate to carry out a quaternization reaction, the stirring speed is increased, the reaction is stirred continuously for 4-5 hours, and then recrystallized with acetone for multiple times to finally obtain a gemini imidazoline functional monomer.

[0034] The unsaturated fatty acid in step (1) is one of 9-hexadecenoic acid and 9-octadecenoic acid, the molar ratio of the unsaturated fatty acid to triethylenetetramine is 2:1-1.5, the amount of water-carrying agent toluene is 25wt.% of the total amount of the reaction, and the amount of catalyst α-Al2O3 is 1.5wt.% of the total amount of the reaction.

[0035] The quaternizing agent in step (3) is sodium 3-chloro-2-hydroxypropanesulfonate, and the molar ratio of triethylenetetramine to sodium 3-chloro-2-hydroxypropanesulfonate is 1:1-1.2.

[0036] The relevant reaction equation is as follows:

[0037]

[0038] Where R1 is C 17 H 33 , C 15 H 29 One of them.

[0039] The formula for preparing imidazoline polycarboxylate water reducer is as follows:

[0040] The invention comprises the following components by weight: 300-450 parts of unsaturated polyether monomer, 28-35 parts of unsaturated acid, 10-25 parts of imidazoline functional monomer, 1.5-5.0 parts of initiator, 0.3-2.5 parts of reducing agent, 1.2-5.5 parts of chain transfer agent, and 340-510 parts of water. The unsaturated polyether monomer is one or two of methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, and ethylene glycol monovinyl polyoxyethylene ether; the unsaturated acid is one or two of acrylic acid, methacrylic acid, and maleic anhydride; the oxidant is any one of hydrogen peroxide, ammonium persulfate, and potassium persulfate, or a mixture thereof; the reducing agent is one or two of L-ascorbic acid, bleaching agent, and E51; the chain transfer agent is one or two of thioglycolic acid, 3-mercaptopropionic acid, mercaptoethanol, and sodium hypophosphite.

[0041] The method for preparing imidazoline type polycarboxylate water reducer is as follows:

[0042] The unsaturated polyether monomer and the chain transfer agent are mixed and dissolved in water, and the initiator is added at 20±2°C. After stirring evenly, the aqueous solution of the unsaturated acid and the imidazoline functional monomer is uniformly added dropwise within 50 minutes, and the aqueous solution of the reducing agent is uniformly added dropwise within 60 minutes. After the addition is completed, the mixture is kept warm for 60 minutes to obtain the imidazoline type polycarboxylic acid water reducer.

[0043] The chemical structural formula of the imidazoline polycarboxylate water reducer obtained by the reaction is as follows:

[0044]

[0045] Wherein, X, Y, and Z are the number of chain segments of the copolymer repeating unit; M is a hydrogen atom or an alkali metal atom; n is the degree of polymerization of ethylene oxide, n=55 to 70; and a is C5H10 or C7H14.

[0046] Example 1

[0047] Preparation of Gemini imidazoline functional monomer: 255g 9-hexadecenoic acid was placed in a 1000mL three-necked flask, a magnetic particle was added, a water separator and a serpentine condenser were installed, 65g toluene and 3.8g α-Al2O3 were added, the temperature of the oil bath was heated to 145°C and stirred continuously, 73g triethylenetetramine was added to the flask at a uniform rate within 0.5h using a dropper, condensed and refluxed for 2h, the temperature was slowly raised to 190°C, a water separator was installed, and the temperature was maintained for 6h until no more water was generated in the water separator. A vacuum distillation device was used instead, and the reaction temperature was maintained at 145°C with an oil bath for 2h, toluene was separated, and 98.5g 3-chloro-2-hydroxypropanesulfonic acid sodium was added after cooling to 85°C for quaternization reaction, the stirring speed was accelerated, and the reaction was stirred continuously for 4h, and then recrystallized several times with acetone, and finally the Gemini imidazoline functional monomer A was obtained.

[0048] Preparation of oxazoline type polycarboxylate water reducer: 300g methyl allyl polyoxyethylene ether and 4.5g sodium hypophosphite are mixed and dissolved in 290g water, 1.5g hydrogen peroxide is added at 20±2°C, and after stirring evenly, a solution prepared by 29g acrylic acid, 15g imidazoline functional monomer A and 15g tap water is uniformly added dropwise within 50min; a solution prepared by 0.4g L-ascorbic acid and 45g tap water is uniformly added dropwise within 60min, and after the addition is completed, the solution is kept warm for 60min to obtain the imidazoline type polycarboxylate water reducer.

[0049] Example 2

[0050] Preparation of Gemini imidazoline functional monomer: 282.5g 9-octadecenoic acid was placed in a 1000mL three-necked flask, a magnetic particle was added, a water separator and a serpentine condenser were installed, 65g toluene and 3.8g α-Al2O3 were added, the temperature of the oil bath was heated to 145°C and stirred continuously, 73g triethylenetetramine was added to the flask at a uniform rate within 0.5h using a dropper, condensed and refluxed for 2h, the temperature was slowly raised to 190°C, a water separator was installed, and the temperature was maintained for 6h until no more water was generated in the water separator. A vacuum distillation device was used instead, and the reaction temperature was maintained at 145°C with an oil bath for 2h, toluene was separated, and 98.5g 3-chloro-2-hydroxypropanesulfonic acid sodium was added after cooling to 85°C for quaternization reaction, the stirring speed was accelerated, and the reaction was stirred continuously for 4h, and then recrystallized several times with acetone, and finally the Gemini imidazoline functional monomer B was obtained.

[0051] Preparation of oxazoline type polycarboxylate water reducer: 300g methyl allyl polyoxyethylene ether and 4.5g sodium hypophosphite are mixed and dissolved in 290g water, 1.5g hydrogen peroxide is added at 20±2°C, and stirred evenly. A solution prepared by 29g acrylic acid, 20g imidazoline functional monomer B and 15g tap water is uniformly added dropwise within 50min; a solution prepared by 0.4g L-ascorbic acid and 45g tap water is uniformly added dropwise within 60min. After the addition is completed, the solution is kept warm for 60min to obtain the imidazoline type polycarboxylate water reducer.

[0052] Example 3

[0053] Preparation of Gemini imidazoline functional monomer: 282.5g 9-octadecenoic acid was placed in a 1000ml three-necked flask, a magnetic particle was added, a water separator and a serpentine condenser were installed, 65g toluene and 3.8g α-Al2O3 were added, the temperature of the oil bath was heated to 145°C and stirred continuously, 80g triethylenetetramine was added to the flask at a uniform rate within 0.5h using a dropper, condensed and refluxed for 2h, the temperature was slowly raised to 190°C, a water separator was installed, and the temperature was maintained for 6h until no more water was generated in the water separator. A vacuum distillation device was used instead, and the reaction temperature was maintained at 145°C with an oil bath for 2h, toluene was separated, and 125g sodium 3-chloro-2-hydroxypropanesulfonate was added after cooling to 85°C for quaternization reaction, the stirring speed was accelerated, and the reaction was stirred continuously for 4h, and then recrystallized several times with acetone, and finally the Gemini imidazoline functional monomer C was obtained.

[0054] Preparation of oxazoline type polycarboxylate water reducer: 300g of ethylene glycol monovinyl polyoxyethylene ether and 4.5g of sodium hypophosphite are mixed and dissolved in 290g of water, 1.5g of hydrogen peroxide is added at 20±2°C, and after stirring evenly, a solution prepared by 33g of acrylic acid, 20g of imidazoline functional monomer C and 15g of tap water is uniformly added dropwise within 50min; a solution prepared by 0.4g of L-ascorbic acid and 45g of tap water is uniformly added dropwise within 60min, and after the addition is completed, the solution is kept warm for 60min to obtain the imidazoline type polycarboxylate water reducer.

[0055] Example 4

[0056] Preparation of Gemini imidazoline functional monomer: 282.5g 9-octadecenoic acid was placed in a 1000ml three-necked flask, a magnetic particle was added, a water separator and a serpentine condenser were installed, 65g toluene and 3.8g α-Al2O3 were added, the temperature of the oil bath was heated to 145°C and stirred continuously, 85g triethylenetetramine was added to the flask at a uniform rate within 0.5h using a dropper, condensed and refluxed for 2h, the temperature was slowly raised to 190°C, a water separator was installed, and the temperature was maintained for 6h until no more water was generated in the water separator. A vacuum distillation device was used instead, and the reaction temperature was maintained at 145°C with an oil bath for 2h, toluene was separated, and 125g sodium 3-chloro-2-hydroxypropanesulfonate was added after cooling to 85°C for quaternization reaction, the stirring speed was accelerated, and the reaction was stirred continuously for 4h, and then recrystallized several times with acetone, and finally the Gemini imidazoline functional monomer D was obtained.

[0057] Preparation of oxazoline type polycarboxylate water reducer: 300g of ethylene glycol monovinyl polyoxyethylene ether and 4.5g of sodium hypophosphite are mixed and dissolved in 290g of water, 1.5g of hydrogen peroxide is added at 20±2°C, and after stirring evenly, a solution prepared by 33g of acrylic acid, 25g of imidazoline functional monomer D and 15g of tap water is uniformly added dropwise within 50min; a solution prepared by 0.4g of L-ascorbic acid and 45g of tap water is uniformly added dropwise within 60min, and after the addition is completed, the solution is kept warm for 60min to obtain the imidazoline type polycarboxylate water reducer.

[0058] Example 5

[0059] Preparation of Gemini imidazoline functional monomer: 282.5g 9-octadecenoic acid was placed in a 1000ml three-necked flask, a magnetic particle was added, a water separator and a serpentine condenser were installed, 65g toluene and 3.8g α-Al2O3 were added, the temperature of the oil bath was heated to 145°C and stirred continuously, 85g triethylenetetramine was added to the flask at a uniform rate within 0.5h using a dropper, condensed and refluxed for 2h, the temperature was slowly raised to 190°C, a water separator was installed, and the temperature was maintained for 6h until no more water was generated in the water separator. A vacuum distillation device was used instead, and the reaction temperature was maintained at 145°C with an oil bath for 2h, toluene was separated, and 155g sodium 3-chloro-2-hydroxypropanesulfonate was added after cooling to 85°C for quaternization reaction, the stirring speed was accelerated, and the reaction was stirred continuously for 4h, and then recrystallized several times with acetone, and finally the Gemini imidazoline functional monomer E was obtained.

[0060] Preparation of oxazoline type polycarboxylate water reducer: 300g of ethylene glycol monovinyl polyoxyethylene ether and 4.5g of sodium hypophosphite are mixed and dissolved in 290g of water, 1.5g of hydrogen peroxide is added at 20±2°C, and after stirring evenly, a solution prepared by 33g of acrylic acid, 25g of imidazoline functional monomer E and 15g of tap water is uniformly added dropwise within 50min; a solution prepared by 0.4g of L-ascorbic acid and 45g of tap water is uniformly added dropwise within 60min, and after the addition is completed, the solution is kept warm for 60min to obtain the imidazoline type polycarboxylate water reducer.

[0061] Comparative Example 1

[0062] 300g of methyl allyl polyoxyethylene ether and 4.5g of sodium hypophosphite were mixed and dissolved in 290g of water, 1.5g of hydrogen peroxide was added at 20±2°C, and stirred evenly. A solution prepared by 29g of acrylic acid and 15g of tap water was uniformly added dropwise within 50min; a solution prepared by 0.4g of L-ascorbic acid and 45g of tap water was uniformly added dropwise within 60min. After the addition was completed, the mixture was kept warm for 60min to obtain a polycarboxylic acid water reducer.

[0063] Comparative Example 2

[0064] 300g of ethylene glycol monovinyl polyoxyethylene ether and 4.5g of sodium hypophosphite were mixed and dissolved in 290g of water, 1.5g of hydrogen peroxide was added at 20±2°C, and stirred evenly. A solution prepared by 33g of acrylic acid and 15g of tap water was uniformly added dropwise within 50min; a solution prepared by 0.4g of L-ascorbic acid and 45g of tap water was uniformly added dropwise within 60min. After the addition was completed, the mixture was kept warm for 60min to obtain a polycarboxylic acid water reducer.

[0065] In order to further illustrate the performance effect of an imidazoline polycarboxylate water-reducing agent provided by the present invention, according to the standard GB8076-2008 "Concrete Admixtures", the above embodiments and comparative examples were subjected to concrete working performance tests, wherein the water-binder ratio was 0.45; the machine-made sand used was the same batch number from the same sand field, the mud content was 12.5%, and the same compounding conditions were adopted. The concrete mix ratio was shown in Table 1, and the concrete performance test results were shown in Table 2:

[0066] Table 1 Concrete mix ratio (kg / m3)

[0067] cement Fly ash Machine-made sand Stone water 320 40 900 980 162

[0068] The experimental data obtained by the above test method are shown in Table 2:

[0069]

[0070] It can be seen from the data in the above table that compared with Comparative Example 1, Examples 1-2; and compared with Comparative Example 2, due to the introduction of the gemini imidazoline functional monomer on the side chain of the polycarboxylate water-reducing agent molecule, the steric hindrance of the polycarboxylate water-reducing agent is increased, the dispersion on the cement particles is improved, and the water reduction rate is increased; and when the dosage is lower than that of the comparative example, the water reduction and slump retention performances of the examples are better than those of the comparative example.

[0071] The main influence on polycarboxylate water reducer in machine-made sand is montmorillonite. Since the polyether side chain of polycarboxylate water reducer is directly adsorbed into the interlayer of montmorillonite and will not be adsorbed on the surface of cement particles, the dosage of polycarboxylate water reducer is high and the loss is large. The present invention grafts gemini imidazoline functional monomers on the molecular chain of polycarboxylate water reducer, and imidazoline preferentially adsorbs montmorillonite in machine-made sand, effectively avoiding the consumption of polyether side chains and achieving the anti-mud effect.

[0072] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A gemini imidazoline functional monomer, characterized in that: Its chemical structure is as follows: Wherein R1 is one of C17H33 and C15H29.

2. The method for preparing a gemini imidazoline functional monomer as claimed in claim 1, wherein: The following steps are involved: (1) Amidation reaction: unsaturated fatty acid is placed in a 1000 mL three-necked flask, a magnetic bar is added, a water separator and a serpentine condenser are installed, toluene is added as a water-carrying agent, and α-Al2O3 is added as a catalyst. The temperature of the oil bath is heated to 140-150°C and stirred continuously. Triethylenetetramine is added to the flask at a uniform rate within 0.5 h using a dropper. After condensation and reflux reaction for 2 h, an amide intermediate is obtained. (2) Cyclization reaction: slowly raise the temperature of the amide intermediate in step (1) to 180-210°C, install a water separator, maintain the temperature for 6 hours, until no more water is generated in the water separator, use a vacuum distillation device, and use an oil bath to maintain the reaction temperature at 140-150°C for 2 hours, separate toluene, and finally obtain an imidazoline intermediate; (3) Quaternization reaction: The imidazoline intermediate in step (2) is cooled to 80-90° C., a quaternizing agent is added to the imidazoline intermediate to carry out a quaternization reaction, the stirring speed is increased, the reaction is stirred continuously for 4-5 hours, and then recrystallized with acetone for multiple times to finally obtain a gemini imidazoline functional monomer.

3. The method for preparing the gemini imidazoline functional monomer according to claim 2, characterized in that: The unsaturated fatty acid in step (1) is one of 9-hexadecenoic acid and 9-octadecenoic acid, the molar ratio of the unsaturated fatty acid to triethylenetetramine is 2:1-1.5, the amount of water-carrying agent toluene is 25wt.% of the total reaction amount, and the amount of catalyst α-Al2O3 is 1.5wt.% of the total reaction amount.

4. The method for preparing the gemini imidazoline functional monomer according to claim 2, characterized in that: The quaternizing agent in step (3) is sodium 3-chloro-2-hydroxypropanesulfonate, and the molar ratio of triethylenetetramine to sodium 3-chloro-2-hydroxypropanesulfonate is 1:1-1.

2.

5. An imidazoline type polycarboxylate water reducer prepared by the gemini imidazoline functional monomer according to claim 1, characterized in that: The chemical structure is as follows: Wherein, X, Y, and Z are the number of chain segments of the copolymer repeating unit; M is a hydrogen atom or an alkali metal atom; n is the degree of polymerization of ethylene oxide, n=55 to 70; and a is 5 or 7.

6. A formula for preparing the imidazoline polycarboxylate water-reducing agent according to claim 5, characterized in that: The invention comprises the following components in weight: 300-450 parts of unsaturated polyether monomer, 28-35 parts of unsaturated acid, 10-25 parts of imidazoline functional monomer, 1.5-5.0 parts of initiator, 0.3-2.5 parts of reducing agent, 1.2-5.5 parts of chain transfer agent and 340-510 parts of water.

7. A method for preparing an imidazoline type polycarboxylate water reducer according to the formula of the imidazoline type polycarboxylate water reducer according to claim 6, characterized in that: The method comprises the following steps: dissolving an unsaturated polyether monomer and a chain transfer agent in water, adding an initiator at 20±2° C., stirring evenly, dripping an aqueous solution of an unsaturated acid and an imidazoline functional monomer at a uniform speed within 50 minutes, and dripping an aqueous solution of a reducing agent at a uniform speed within 60 minutes, and keeping the temperature for 60 minutes after the dripping is completed, so as to obtain the imidazoline type polycarboxylic acid water reducer.

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