Oleic acid modified polycarboxylate superplasticizer, its preparation method and application

Abstract

The present invention relates to the technical field of polycarboxylate superplasticizers and their preparation methods and applications, and is an oleic acid-modified polycarboxylate superplasticizer and its preparation method and application. The raw materials of the oleic acid-modified polycarboxylate superplasticizer include polyether monomers, acrylic acid, oleic acid, emulsifiers, oxidants, etc. The present invention selects oleic acid, which is cheaper and more environmentally friendly than acrylic acid, as the third monomer to synthesize a new terpolymer (oleic acid-modified polycarboxylate superplasticizer), which can improve the water retention and bonding properties of the slurry at the same time; the oleic acid-modified polycarboxylate superplasticizer synthesized by the present invention is more significant in adsorbing and dispersing cement particles than the unmodified polycarboxylate superplasticizer, showing a good effect of promoting cement hydration and improving the mechanical properties of concrete, and has application prospects in engineering fields with high requirements for the early strength of concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of polycarboxylate superplasticizers and their preparation methods and applications, and is an oleic acid-modified polycarboxylate superplasticizer and its preparation method and application. Background Art

[0002] Polycarboxylate superplasticizers are one of the most widely used concrete admixtures in the field of construction engineering. Their development process can be roughly divided into three stages: The first-generation lignosulfonate-based superplasticizers adhere to the principle of secondary utilization of waste resources, mostly using pulp waste liquid as raw materials and going through multiple processes to obtain. However, they have a low water reduction rate (5% to 10%), a large air-entraining property, and seriously reduce the mechanical properties of concrete when over-dosed; The second-generation superplasticizers represented by naphthalene-based superplasticizers have a higher water reduction rate than the previous generation (10% to 20%), a small air-entraining volume, and good compatibility with materials. However, due to the use of formaldehyde in the raw materials, they do not conform to the basic strategy of the development of green chemistry, which has promoted the emergence of the third-generation polycarboxylate superplasticizers; The third-generation polycarboxylate superplasticizers are widely used because their effective molecular structure can be flexibly designed according to the mechanism of action of dispersing cement, and they have the advantages of a high water reduction rate (about 30%) at low dosages, good slump retention, a low concrete shrinkage rate, great performance potential, and environmental friendliness. However, there is a problem of large differences in compatibility with different sand and gravel aggregates.

[0003] Based on the mechanism of action of polycarboxylate superplasticizers, their preparation process is realized by free radical polymerization. Through literature review (such as CN111154046A, CN106946494A, CN109942757A, CN111004358A, CN114524908A), it is found that the commonly used methods for preparing polycarboxylate superplasticizers at present are mainly aqueous solution free radical polymerization and bulk polymerization. However, compared with emulsion polymerization, the products synthesized by aqueous solution free radical polymerization have a smaller molecular weight, which will affect the product performance, and have the disadvantages of being difficult to transport and store over long distances; Bulk polymerization will have problems such as difficult reaction control, difficult heat dissipation, unstable dispersion system, difficult product pumping, and high equipment costs; Living / controlled free radical polymerization has deficiencies such as a complex operation process, high production costs, and difficulty in industrial production. Therefore, different from the above patents, the present invention uses emulsion polymerization to synthesize an oleic acid-modified polycarboxylate superplasticizer with excellent performance.

[0004] In addition, in order to achieve the application performance of polycarboxylate superplasticizers in specific fields, many researchers have, in recent years, rationally designed the molecular structure of polycarboxylate superplasticizers to meet the requirements of concrete for subway segment linings in terms of early strength. For example, the patent document with the publication number CN111763290A (Chen Jie. A kind of early-strength polycarboxylate superplasticizer [P]) discloses a preparation method of a polycarboxylate superplasticizer capable of improving the early strength of concrete. The raw materials are in a mass ratio of: 240 - 300 parts of polyether monomer, 19 - 22.5 parts of unsaturated acid, 1 - 1.2 parts of hydrogen peroxide, 0.3 - 0.5 parts of reducing agent, 1 - 1.3 parts of molecular weight regulator, 18 - 23.5 parts of functional monomer, and 400 - 500 parts of water, among which 8 - 10 parts of self-made early-strength functional monomer, 5 - 7 parts of acrylamide, 1 - 1.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, and 4 - 6 parts of methacryloyloxyethyltrimethylammonium chloride are used. An early-strength polycarboxylate superplasticizer is prepared by aqueous solution free radical polymerization. Although the early strength of concrete is improved to a certain extent, the numerous raw materials used undoubtedly increase the production cost, and the compressive strength of the concrete in the group with the best effect in the examples only increases by 5.1 MPa after 18 h compared with the ordinary polycarboxylate superplasticizer in the comparative examples. Wang Yongding (Wang Yongding. Synthesis and performance study of high thixotropic early-strength polycarboxylate superplasticizer [J]. New Building Materials, 2020, 47(09): 72 - 75.) synthesized a high thixotropic early-strength polycarboxylate superplasticizer from isobutenol polyoxyethylene ether, unsaturated fatty acid glyceride, unsaturated quaternary ammonium salt, and acrylic acid at room temperature. The test results show that compared with the traditional polycarboxylate superplasticizer, the compressive strength of concrete at each age increases, but the increase amplitude is small. However, under the premise of controlling the raw material cost and simplifying the process flow, the present invention synthesizes an oleic acid-modified polycarboxylate superplasticizer, and the improvement effect of its 4-h concrete compressive strength compared with the comparative examples is relatively significant. Summary of the Invention

[0005] The present invention provides an oleic acid-modified polycarboxylate superplasticizer, its preparation method and application. Compared with traditional polycarboxylate superplasticizers, the oleic acid-modified polycarboxylate superplasticizer of the present invention not only has a certain novelty in the preparation method, that is, it is different from the common aqueous solution free radical polymerization method, but also has a more significant application effect in promoting cement hydration and improving the early strength of concrete.

[0006] One of the technical solutions of the present invention is achieved by the following measures: An oleic acid-modified polycarboxylate superplasticizer, the structural general formula of which is:

[0007]

[0008] In the structural general formula, R1 is -H or -CH3, and R2 is -CH2 or -CH2CH2.

[0009] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0010] The oleic acid-modified polycarboxylic acid water-reducing agent is prepared from raw materials including polyether monomer, acrylic acid, oleic acid, emulsifier, oxidant, reducing agent and thioglycolic acid. The raw materials are calculated by weight as follows: 20 to 50 parts of polyether monomer, 3.0 to 6.0 parts of acrylic acid, 0.1 to 0.6 parts of oxidant, 0.03 to 0.3 parts of reducing agent, 0.1 to 1.0 parts of thioglycolic acid, 3% to 20% of the weight of acrylic acid, 1% to 9% of the weight of emulsifier, and one or more of allyl polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether and 3-methylbut-3-enyl polyoxyethylene ether.

[0011] The oleic acid-modified polycarboxylate water reducer is prepared according to the following method: first, pre-preparing liquid A and liquid B, wherein liquid A is composed of a required amount of a reducing agent, thioglycolic acid, and distilled water, and liquid B is composed of a required amount of acrylic acid and distilled water; second, adding a required amount of a polyether monomer into distilled water and stirring until completely dissolved; third, adding a required amount of an emulsifier and oleic acid to the solution obtained in the second step, stirring, adding a required amount of an oxidant to the system, and continuing to fully stir at a certain temperature and stirring speed; fourth, slowly adding liquid A and liquid B dropwise, respectively, wherein the dropwise addition time of liquid A is 1 to 3 hours, and the dropwise addition time of liquid B is 0.5 to 2.5 hours; and fifth, after the dropwise addition is completed, heat-insulating and reacting for 1 to 3 hours to obtain a slightly milky white oleic acid-modified polycarboxylate water reducer.

[0012] In the third step, the required amount of emulsifier and oleic acid is added to the solution obtained in the second step, and after stirring for 15 to 20 minutes, the required amount of oxidant is added to the system, and the stirring is continued for 15 to 20 minutes at a certain temperature and stirring speed.

[0013] In the third step, the reaction temperature is 15° C. to 45° C.; or / and, in the third step, the stirring speed is 100 rpm to 300 rpm.

[0014] The emulsifier is one or more of Tween 20, Tween 60, polyvinyl alcohol (1788), and Tween 80.

[0015] The oxidant is one or more of benzoyl peroxide, ammonium persulfate, and sodium perborate.

[0016] The reducing agent is one or more of sodium sulfite, N,N-dimethylaniline, trimethylamine and triethanolamine.

[0017] The second technical solution of the present invention is achieved by the following measures: A preparation method of the oleic acid-modified polycarboxylate water reducer described in one of the technical solutions, the preparation raw materials include polyether monomer, acrylic acid, oleic acid, emulsifier, oxidant, reductant, and mercaptoacetic acid. By weight, the polyether monomer is 20 parts to 50 parts, acrylic acid is 3.0 parts to 6.0 parts, oxidant is 0.1 part to 0.6 part, reductant is 0.03 part to 0.3 part, mercaptoacetic acid is 0.1 part to 1.0 part. The dosage of oleic acid accounts for 3% to 20% of the mass of acrylic acid, and the dosage of emulsifier accounts for 1% to 9% of the mass of oleic acid. The polyether monomer is one or more of allyl polyoxyethylene ether, methallyl alcohol polyoxyethylene ether, 3-methylbut-3-enyl polyoxyethylene ether;

[0018] Its preparation method is carried out as follows: First step, prepare A liquid and B liquid in advance. Among them, A liquid is composed of the required amount of reductant, mercaptoacetic acid, and distilled water, and B liquid is composed of the required amount of acrylic acid and distilled water; Second step, add the required amount of polyether monomer to distilled water and stir until completely dissolved; Third step, add the required amount of emulsifier and oleic acid to the solution obtained in the second step, stir, and then add the required amount of oxidant to the system, and continue to stir fully at a certain temperature and stirring speed; Fourth step, slowly dropwise add A liquid and B liquid respectively. The dropping time of A liquid is 1 hour to 3 hours, and the dropping time of B liquid is 0.5 hour to 2.5 hours; Fifth step, after the dropping is completed, keep the temperature for reaction for 1 hour to 3 hours to obtain an oleic acid-modified polycarboxylate water reducer showing a slightly milky white color.

[0019] The third technical solution of the present invention is achieved by the following measures: Application of the oleic acid-modified polycarboxylate water reducer described in one of the technical solutions in improving the performance of concrete.

[0020] The oleic acid-modified polycarboxylate water reducer prepared by the emulsion polymerization method of the present invention promotes the hydration of cement more significantly and has the effect of improving the mechanical properties of concrete. It has certain reference significance when applied to engineering fields with high requirements for the early strength of concrete. Description of the Drawings

[0021] Attached Figure 1 is the polymerization process of the present invention.

[0022] Attached Figure 2 is the infrared spectrum diagram of the oleic acid-modified polycarboxylate water reducer prepared in Example 3 of the present invention.

[0023] Attached Figure 3 is the nuclear magnetic resonance hydrogen spectrum diagram of the oleic acid-modified polycarboxylate water reducer prepared in Example 3 of the present invention.

[0024] Attached Figure 2 In it, SPEG refers to methallyl alcohol polyoxyethylene ether. Detailed Embodiments

[0025] The present invention is not limited by the following embodiments, and the specific implementation manners can be determined according to the technical solutions of the present invention and the actual situation. Various chemical reagents and chemical supplies mentioned in the present invention are publicly known and commonly used chemical reagents and chemical supplies in the prior art unless otherwise specified; the percentages in the present invention are mass percentages unless otherwise specified.

[0026] In the following embodiments, the polyvinyl alcohol used is polyvinyl alcohol (1788).

[0027] The present invention will be further described below in conjunction with embodiments:

[0028] Embodiment 1: The raw materials for preparing the oleic acid-modified polycarboxylate water reducer include polyether monomers, acrylic acid, oleic acid, emulsifier, oxidant, reductant, and mercaptoacetic acid. By weight, the raw materials are 20 g to 50 g of polyether monomers, 3.0 g to 6.0 g of acrylic acid, 0.1 g to 0.6 g of oxidant, 0.03 g to 0.3 g of reductant, 0.1 g to 1.0 g of mercaptoacetic acid. The amount of oleic acid used accounts for 3% to 20% of the mass of acrylic acid, and the amount of emulsifier used accounts for 1% to 9% of the mass of oleic acid. The polyether monomers are one or more of allyl polyoxyethylene ether, methallyl alcohol polyoxyethylene ether, and 3-methylbut-3-enyl polyoxyethylene ether;

[0029] The oleic acid-modified polycarboxylate water reducer is prepared by the following preparation method: First step, prepare A liquid and B liquid in advance. A liquid is composed of the required amount of reductant, mercaptoacetic acid, and distilled water, and B liquid is composed of the required amount of acrylic acid and distilled water; Second step, add the required amount of polyether monomers to distilled water and stir until completely dissolved; Third step, add the required amount of emulsifier and oleic acid to the solution obtained in the second step, stir for about 15 minutes to 20 minutes, and then add the required amount of oxidant to the system. Continue to stir thoroughly for 15 minutes to 20 minutes under the conditions of a temperature of 15°C to 45°C and a stirring speed of 100 revolutions per minute to 300 revolutions per minute; Fourth step, slowly drip A liquid and B liquid respectively with a peristaltic pump. The dropping time of A liquid is 1 hour to 3 hours, and the dropping time of B liquid is 0.5 hour to 2.5 hours; Fifth step, after the dropping is completed, keep the temperature for reaction for 1 hour to 3 hours to obtain an oleic acid-modified polycarboxylate water reducer in a slightly milky white color.

[0030] Example 2: The raw materials for preparing the oleic acid-modified polycarboxylate water reducer include polyether monomers, acrylic acid, oleic acid, emulsifiers, oxidants, reductants, and mercaptoacetic acid. By weight, the raw materials are as follows: 20 g or 50 g of polyether monomer, 3.0 g or 6.0 g of acrylic acid, 0.1 g or 0.6 g of oxidant, 0.03 g or 0.3 g of reductant, 0.1 g or 1.0 g of mercaptoacetic acid. The amount of oleic acid used accounts for 3% or 20% of the mass of acrylic acid, and the amount of emulsifier used accounts for 1% or 9% of the mass of oleic acid. The polyether monomer is one or more of allyl polyoxyethylene ether, methallyl alcohol polyoxyethylene ether, and 3-methylbut-3-enyl polyoxyethylene ether;

[0031] The oleic acid-modified polycarboxylate water reducer is prepared by the following method: First step, prepare solution A and solution B in advance. Solution A consists of the required amount of reductant, mercaptoacetic acid, and distilled water, and solution B consists of the required amount of acrylic acid and distilled water; Second step, add the required amount of polyether monomer to distilled water and stir until completely dissolved; Third step, add the required amount of emulsifier and oleic acid to the solution obtained in the second step, stir for about 15 minutes or 20 minutes, and then add the required amount of oxidant to the system. Continue to stir thoroughly for 15 minutes or 20 minutes under the conditions of a temperature of 15°C or 45°C and a stirring speed of 100 revolutions per minute or 300 revolutions per minute; Fourth step, slowly drip solution A and solution B respectively with a peristaltic pump. The dripping time of solution A is 1 hour or 3 hours, and the dripping time of solution B is 0.5 hour or 2.5 hours; Fifth step, after the dripping is completed, keep the temperature for reaction for 1 hour or 3 hours to obtain an oleic acid-modified polycarboxylate water reducer in a slightly milky white color.

[0032] The emulsifier described in the above example can be one or more of Tween 20, Tween 60, polyvinyl alcohol (1788), and Tween 80.

[0033] The oxidant described in the above example can be one or more of benzoyl peroxide, ammonium persulfate, and sodium perborate.

[0034] The reductant described in the above example can be one or more of sodium sulfite, N,N-dimethylaniline, trimethylamine, and triethanolamine.

[0035] The following is illustrated with specific preparation examples.

[0036] Example 3: For the oleic acid-modified polycarboxylate water reducer (OA-PCE), the raw materials include 36.5 g of methallyl alcohol polyoxyethylene ether, 4.36 g of acrylic acid, 5% of the mass of acrylic acid for the amount of oleic acid used, 5% of the mass of oleic acid for the amount of polyvinyl alcohol as the emulsifier used, 0.33 g of ammonium persulfate, 0.06 g of trimethylamine, and 0.293 g of mercaptoacetic acid.

[0037] The oleic acid modified polycarboxylate water reducer is prepared by the following method: In the first step, two solutions labeled A and B are prepared in advance for use. Solution A consists of the required amounts of trimethylamine, mercaptoacetic acid, and distilled water, and solution B consists of the required amounts of acrylic acid and distilled water. In the second step, the required amounts of allyl polyoxyethylene ether and distilled water are added into a four-necked flask equipped with a stirrer and a thermometer, and stirred until completely dissolved. In the third step, the required amounts of polyvinyl alcohol and oleic acid are added to the solution, and after stirring for about 15 to 20 minutes, the required amount of ammonium persulfate is added to the system. Under the conditions of a temperature of 25 °C and a stirring speed of 250 revolutions per minute, stirring is continued for 15 to 20 minutes. In the fourth step, solutions A and B are slowly added dropwise using a peristaltic pump. The dropping time of solution A is 3 hours, and the dropping time of solution B is 2.5 hours. In the fifth step, after the dropping is completed, the reaction is carried out under insulation for 1 hour to obtain an oleic acid modified polycarboxylate water reducer that is slightly milky white.

[0038] In the present invention, oleic acid, which is cheaper and more environmentally friendly than acrylic acid, is selected as the third monomer, and polyvinyl alcohol is used as an emulsifier to simultaneously improve the water retention and bonding properties of the slurry, and a new terpolymer is synthesized: oleic acid modified polycarboxylate water reducer. The polymerization process of Example 3 is as Figure 2 shown. Compared with traditional polycarboxylate water reducers, the oleic acid modified polycarboxylate water reducer has a more significant effect on improving the mechanical properties of concrete.

[0039] Example 4: The raw materials of the oleic acid modified polycarboxylate water reducer include 37 grams of allyl polyoxyethylene ether, 4.25 grams of acrylic acid, 15% of the mass of acrylic acid for the amount of oleic acid, 7% of the mass of oleic acid for the amount of emulsifier Tween 80, 0.33 grams of ammonium persulfate, 0.06 grams of trimethylamine, and 0.293 grams of mercaptoacetic acid.

[0040] The oleic acid modified polycarboxylate water reducer is prepared by the following method: In the first step, two solutions labeled A and B are prepared in advance for use. Solution A consists of the required amounts of trimethylamine, mercaptoacetic acid, and distilled water, and solution B consists of the required amounts of acrylic acid and distilled water. In the second step, the required amounts of allyl polyoxyethylene ether and distilled water are added into a four-necked flask equipped with a stirrer and a thermometer, and stirred until completely dissolved. In the third step, the required amounts of emulsifier Tween 80 and oleic acid are added to the solution, and after stirring for about 15 to 20 minutes, the required amount of ammonium persulfate is added to the system. Under the conditions of a temperature of 25 °C and a stirring speed of 100 revolutions per minute, stirring is continued for 15 to 20 minutes. In the fourth step, solutions A and B are slowly added dropwise using a peristaltic pump. The dropping time of solution A is 2.5 hours, and the dropping time of solution B is 2 hours. In the fifth step, after the dropping is completed, the reaction is carried out under insulation for 1 hour to obtain an oleic acid modified polycarboxylate water reducer that is slightly milky white.

[0041] Example 5: The oleic acid-modified polycarboxylate water reducer has raw materials including 38 g of methallyl alcohol polyoxyethylene ether, 4.5 g of acrylic acid, the amount of oleic acid accounting for 5% of the mass of acrylic acid, 3% of the mass of oleic acid of the emulsifier polyvinyl alcohol, 0.33 g of ammonium persulfate, 0.06 g of trimethylamine, and 0.293 g of mercaptoacetic acid.

[0042] The oleic acid-modified polycarboxylate water reducer is prepared by the following method: First step, prepare two solutions labeled A and B in advance for later use. Solution A consists of the required amounts of trimethylamine, mercaptoacetic acid, and distilled water, and solution B consists of the required amounts of acrylic acid and distilled water. Second step, add the required amounts of methallyl alcohol polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stir until completely dissolved. Third step, add the required amounts of the emulsifier polyvinyl alcohol and oleic acid into the solution, stir for about 15 to 20 minutes, then add the required amount of ammonium persulfate into the system, and continue to stir thoroughly for 15 to 20 minutes under the conditions of a temperature of 40 °C and a stirring speed of 200 revolutions per minute. Fourth step, slowly dropwise add solutions A and B respectively with a peristaltic pump, where the dropping time of solution A is 3 hours and the dropping time of solution B is 2.5 hours. Fifth step, after the dropping is completed, keep the temperature for reaction for 1.5 hours to obtain a slightly milky white oleic acid-modified polycarboxylate water reducer.

[0043] Example 6: The oleic acid-modified polycarboxylate water reducer has raw materials including 36.5 g of methallyl alcohol polyoxyethylene ether, 4.1 g of acrylic acid, the amount of oleic acid accounting for 10% of the mass of acrylic acid, 5% of the mass of oleic acid of the emulsifier Tween 20, 0.33 g of benzoyl peroxide, 0.06 g of N,N-dimethylaniline, and 0.293 g of mercaptoacetic acid.

[0044] The oleic acid-modified polycarboxylate water reducer is prepared by the following method: First step, prepare two solutions labeled A and B in advance for later use. Solution A consists of the required amounts of N,N-dimethylaniline, mercaptoacetic acid, and distilled water, and solution B consists of the required amounts of acrylic acid and distilled water. Second step, add the required amounts of methallyl alcohol polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stir until completely dissolved. Third step, add the required amounts of the emulsifier Tween 20 and oleic acid into the solution, stir for about 15 to 20 minutes, then add the required amount of benzoyl peroxide into the system, and continue to stir thoroughly for 15 to 20 minutes under the conditions of a temperature of 20 °C and a stirring speed of 150 revolutions per minute. Fourth step, slowly dropwise add solutions A and B respectively with a peristaltic pump, where the dropping time of solution A is 2 hours and the dropping time of solution B is 1.5 hours. Fifth step, after the dropping is completed, keep the temperature for reaction for 1.5 hours to obtain a slightly milky white oleic acid-modified polycarboxylate water reducer.

[0045] Example 7: The oleic acid-modified polycarboxylate water reducer, whose raw materials include 35.5 g of 3-methylbut-3-enyl polyoxyethylene ether, 3.9 g of acrylic acid, the amount of oleic acid accounting for 15% of the mass of acrylic acid, 9% of the mass of oleic acid as the amount of emulsifier Tween 60, 0.33 g of ammonium persulfate, 0.06 g of trimethylamine, and 0.293 g of mercaptoacetic acid.

[0046] The oleic acid-modified polycarboxylate water reducer is prepared by the following method: First step, prepare two solutions labeled A and B in advance for later use. Among them, solution A is composed of the required amount of trimethylamine, mercaptoacetic acid, and distilled water, and solution B is composed of the required amount of acrylic acid and distilled water; Second step, add the required amount of 3-methylbut-3-enyl polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stir until completely dissolved; Third step, add the required amount of emulsifier Tween 60 and oleic acid to the solution, stir for about 15 to 20 minutes, then add the required amount of ammonium persulfate to the system, and continue to stir thoroughly for 15 to 20 minutes under the conditions of a temperature of 30 °C and a stirring speed of 200 revolutions per minute; Fourth step, slowly drip solutions A and B respectively with a peristaltic pump, where the dripping time of solution A is 1.5 hours and the dripping time of solution B is 1.0 hour; Fifth step, after the dripping is completed, keep the temperature for reaction for 1 hour to obtain an oleic acid-modified polycarboxylate water reducer showing a slightly milky white color.

[0047] Example 8: The oleic acid-modified polycarboxylate water reducer, whose raw materials include 36 g of 3-methylbut-3-enyl polyoxyethylene ether, 4.08 g of acrylic acid, the amount of oleic acid accounting for 10% of the mass of acrylic acid, 5% of the mass of oleic acid as the amount of emulsifier polyvinyl alcohol, 0.33 g of benzoyl peroxide, 0.06 g of N,N-dimethylaniline, and 0.293 g of mercaptoacetic acid.

[0048] The oleic acid-modified polycarboxylate water reducer is prepared by the following method: First step, prepare two solutions labeled A and B in advance for later use. Among them, solution A is composed of the required amount of N,N-dimethylaniline, mercaptoacetic acid, and distilled water, and solution B is composed of the required amount of acrylic acid and distilled water; Second step, add the required amount of 3-methylbut-3-enyl polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stir until completely dissolved; Third step, add the required amount of emulsifier polyvinyl alcohol and oleic acid to the solution, stir for about 15 to 20 minutes, then add the required amount of benzoyl peroxide to the system, and continue to stir thoroughly for 15 to 20 minutes under the conditions of a temperature of 35 °C and a stirring speed of 300 revolutions per minute; Fourth step, slowly drip solutions A and B respectively with a peristaltic pump, where the dripping time of solution A is 2 hours and the dripping time of solution B is 1.5 hours; Fifth step, after the dripping is completed, keep the temperature for reaction for 1 hour to obtain an oleic acid-modified polycarboxylate water reducer showing a slightly milky white color.

[0049] Comparative Example 1:

[0050] 35.5 grams of allyl polyoxyethylene ether, 4.50 grams of acrylic acid, 0.33 grams of hydrogen peroxide, 0.06 grams of ascorbic acid, and 0.293 grams of thioglycolic acid are used.

[0051] The unmodified polycarboxylate water-reducing agent is prepared according to the following preparation method: first, preparing two solutions labeled A and B in advance, wherein solution A comprises a required amount of ascorbic acid, thioglycolic acid, and distilled water, and solution B comprises a required amount of acrylic acid and distilled water; second, adding a required amount of allyl polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stirring until completely dissolved; third, adding a required amount of hydrogen peroxide to the solution, and continuing to stir thoroughly for 15 to 20 minutes at a temperature of 25° C. and a stirring speed of 200 rpm; fourth, slowly adding solutions A and B dropwise using a peristaltic pump, wherein solution A is added dropwise for 3 hours and solution B is added dropwise for 2.5 hours; and fifth, after the dropwise addition is completed, the solution is kept warm for reaction for 1.0 hour to obtain a clear and transparent unmodified polycarboxylate water-reducing agent mother solution.

[0052] Comparative Example 2:

[0053] 35.5 grams of methyl allyl alcohol polyoxyethylene ether, 4.50 grams of acrylic acid, 0.33 grams of hydrogen peroxide, 0.06 grams of ascorbic acid and 0.293 grams of thioglycolic acid are used.

[0054] The unmodified polycarboxylate water-reducing agent is prepared according to the following preparation method: first, preparing two solutions labeled A and B in advance, wherein solution A comprises a required amount of ascorbic acid, thioglycolic acid, and distilled water, and solution B comprises a required amount of acrylic acid and distilled water; second, adding a required amount of methyl allyl alcohol polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stirring until completely dissolved; third, adding a required amount of hydrogen peroxide to the solution, and continuing to stir thoroughly for 15 to 20 minutes at a temperature of 25° C. and a stirring speed of 200 rpm; fourth, slowly adding solutions A and B dropwise using a peristaltic pump, wherein solution A is added dropwise for 3 hours and solution B is added dropwise for 2.5 hours; and fifth, after the dropwise addition is completed, the solution is kept warm for reaction for 1.0 hour to obtain a clear and transparent unmodified polycarboxylate water-reducing agent mother solution.

[0055] Comparative Example 3:

[0056] 35.5 g of 3-methylbut-3-enyl polyoxyethylene ether, 4.50 g of acrylic acid, 0.33 g of hydrogen peroxide, 0.06 g of ascorbic acid and 0.293 g of thioglycolic acid were used.

[0057] The unmodified polycarboxylate water reducer is prepared by the following method: First step, prepare two solutions labeled A and B in advance for use. Solution A consists of the required amount of ascorbic acid, mercaptoacetic acid, and distilled water, and solution B consists of the required amount of acrylic acid and distilled water. Second step, add the required amount of 3-methylbut-3-enyl polyoxyethylene ether and distilled water into a four-necked flask equipped with a stirrer and a thermometer, and stir until completely dissolved. Third step, add the required amount of hydrogen peroxide to the solution, and continue to stir thoroughly for 15 to 20 minutes under the conditions of a temperature of 25 °C and a stirring speed of 200 revolutions per minute. Fourth step, slowly drip solutions A and B respectively with a peristaltic pump. The dropping time of solution A is 3 hours, and the dropping time of solution B is 2.5 hours. Fifth step, after the dropping is completed, keep the reaction at a constant temperature for 1.0 hour to obtain a clear and transparent mother liquor of the unmodified polycarboxylate water reducer.

[0058] Comparative Example 4: JS-PCE prepared in Section 1.3.1 (Synthesis of JS-PCE) of the prior art (Zhang Xiaoyu et al. Synthesis, Characterization and Microscopic Mechanism of Cement of Polyether-Type Polycarboxylate Water Reducer [J], Bulletin of the Chinese Ceramic Society, 2021, 40(10): 3366-3375.).

[0059] Comparative Example 5: BT-PCE prepared in Section 1.3.2 (Synthesis of BT-PCE) of the prior art (Zhang Xiaoyu et al. Synthesis, Characterization and Microscopic Mechanism of Cement of Polyether-Type Polycarboxylate Water Reducer [J], Bulletin of the Chinese Ceramic Society, 2021, 40(10): 3366-3375.).

[0060] It can be seen from Figure 2 that in the infrared spectrum of the oleic acid-modified polycarboxylate water reducer (OA-PCE) molecules prepared in Example 3, the broad peak near 3468 cm -1 is the stretching vibration peak of the intramolecular associated hydroxyl group; the stretching vibration peak of methyl and methylene groups is at 2878 cm -1 , and the bending vibration peak of methylene group appears at 1462 cm -1 corresponding to it; the bending vibration peak of methyl group is at 1343 cm -1 ; the antisymmetric stretching vibration peaks of ether bond (-O-) or ester bond (-COO) are at 1281 cm -1 and 1236 cm -1 , corresponding to the symmetric stretching vibration peak of ether bond (-O-) or ester bond (-COO) at 1092 cm -1 ; the stretching vibration peaks of C-O and C-C on the carbon chain are at 949 cm -1 and 838 cm -1 respectively. The basic skeleton of the polymer contains functional groups such as -OH, -COOH, -CH3, -CH2, -O-, -COO, etc.; at 1730 cm -1A distinct stretching vibration peak of C=O in carboxylic acid newly emerged nearby. Comparing with the infrared spectrum of the main reactant monomer SPEG, there is no characteristic peak at 1730 cm -1 , and the double bond stretching vibration peak at 1647 cm -1 disappeared in the infrared spectrum of the synthesized product (OA-PCE), indicating the successful progress of the emulsion polymerization reaction. Further, the structure of the newly synthesized ternary copolymer after oleic acid modification (i.e., oleic acid modified polycarboxylate superplasticizer) was characterized by nuclear magnetic resonance hydrogen spectrum, and the results are as Figure 3 shown. As Figure 3 can be seen, the peak at 1.24 ppm belongs to the hydrogen atom on -CH in the main chain of the superplasticizer molecule. The stronger peak near 1.66 ppm is contributed by the hydrogen atom on -CH2 in the main chain and -CH2 on the long alkyl chain of the oleic acid molecule. The strong peak in the chemical shift range of 3.3 - 3.83 ppm belongs to the hydrogen atom on the polyoxyethylene ether side chain. The peak within 4.83 ppm - 4.92 ppm can be attributed to the chemical shift of α-H in the oleic acid molecule. Combining with the infrared spectrum, it is obtained that the oleic acid molecule was successfully introduced into the structure of the polycarboxylate superplasticizer, and a new oleic acid modified ternary copolymer (i.e., oleic acid modified polycarboxylate superplasticizer) was synthesized.

[0061] The unmodified polycarboxylate superplasticizers of Comparative Examples 1 to 5 and the oleic acid modified polycarboxylate superplasticizers (oleic acid modified polycarboxylate superplasticizers prepared in Examples 3 to 8) were mixed according to the following concrete formula: cement content 360 kg / cm 3 , fly ash content 65 kg / cm 3 , sand content 820 kg / cm 3 , coarse aggregate content 760 kg / cm 3 , fine aggregate content 245 kg / cm 3 , mineral powder content 45 kg / cm 3 , water content 150 kg / cm 3 , admixture content 4.8 kg / cm 3 (the addition amount of oleic acid modified polycarboxylate superplasticizer accounts for 6 parts, the addition amount of sodium thiosulfate accounts for 3 parts, and the addition amount of triethanolamine accounts for 1 part), and the compressive strength values were tested after 4h steam curing and 28d standard curing with reference to the "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T 50081 - 2002. The test results are shown in Table 1. From the performance test results in Table 1, it can be seen that the 4h and 28d compressive strengths of the concrete blocks mixed with the oleic acid modified polycarboxylate superplasticizers of Examples 3 to 8 are greater than those of Comparative Examples 1 to 5. Among them, Example 3 with excellent performance has a 57.6% and 11.8% increase in compressive strength compared with Comparative Example 2 after 4h steam curing and 28d standard curing respectively, and the improvement effect of early strength is significant.

[0062] In summary, the oleic acid-modified polycarboxylate water reducer synthesized by the present invention exhibits good promotion of cement hydration and improvement of the mechanical properties of concrete, and has potential application prospects in engineering fields with high requirements for the early strength of concrete.

[0063] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effects. Non-essential technical features can be added or subtracted according to actual needs to meet the requirements of different situations.

[0064] Table 1 Performance test results

[0065] Sample number Compressive strength at 4 h (MPa) Compressive strength at 28 d (MPa) Comparative example 1 10.3 51.2 Comparative example 2 11.8 55.9 Comparative example 3 12.3 54.7 Comparative example 4 10.5 52.1 Comparative example 5 11.2 53.6 Example 3 18.6 62.5 Example 4 13.2 56.6 Example 5 17.8 61.3 Example 6 14.1 57.5 Example 7 14.7 58.2 Example 8 15.8 59.0

Claims

1. An oleic acid-modified polycarboxylate water reducer, characterized in that, The preparation raw materials include polyether monomer, acrylic acid, oleic acid, emulsifier, oxidant, reducing agent and thioglycolic acid. The raw materials are calculated by weight: 20 to 50 parts of polyether monomer, 3.0 to 6.0 parts of acrylic acid, 0.1 to 0.6 parts of oxidant, 0.03 to 0.3 parts of reducing agent, 0.1 to 1.0 parts of thioglycolic acid, the amount of oleic acid accounts for 3% to 20% of the mass of acrylic acid, the amount of emulsifier accounts for 1% to 9% of the mass of oleic acid, and the polyether monomer is one or more of allyl polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, and 3-methylbut-3-enyl polyoxyethylene ether. The oleic acid-modified polycarboxylate water-reducing agent is prepared according to the following method: first, pre-preparing liquid A and liquid B, wherein liquid A is composed of a required amount of a reducing agent, thioglycolic acid, and distilled water, and liquid B is composed of a required amount of acrylic acid and distilled water; second, adding a required amount of a polyether monomer into distilled water and stirring until completely dissolved; third, adding a required amount of an emulsifier and oleic acid to the solution obtained in the second step, stirring, adding a required amount of an oxidant to the system, and continuing to stir at a certain temperature and stirring speed; fourth, slowly adding liquid A and liquid B dropwise, wherein the dropwise addition time of liquid A is 1 to 3 hours, and the dropwise addition time of liquid B is 0.5 to 2.5 hours; fifth, after the dropwise addition is completed, heat-retaining and reacting for 1 to 3 hours to obtain a slightly milky white oleic acid-modified polycarboxylate water-reducing agent; In the third step, the reaction temperature is 15° C. to 45° C.; the emulsifier is one or more of Tween 20, Tween 60, polyvinyl alcohol 1788, and Tween 80.

2. The oleic acid-modified polycarboxylate water reducer according to claim 1, wherein In the third step, the required amount of emulsifier and oleic acid is added to the solution obtained in the second step, and after stirring for 15 to 20 minutes, the required amount of oxidant is added to the system, and the stirring is continued for 15 to 20 minutes at a certain temperature and stirring speed.

3. The oleic acid-modified polycarboxylate water reducer according to claim 1 or 2, characterized in that In the third step, the stirring speed is 100 rpm to 300 rpm.

4. The oleic acid-modified polycarboxylate water reducer according to claim 1 or 2, characterized in that The oxidizing agent is one or more of benzoyl peroxide, ammonium persulfate, and sodium perborate; or / and the reducing agent is one or more of sodium sulfite, N,N-dimethylaniline, trimethylamine, and triethanolamine.

5. The oleic acid-modified polycarboxylate water reducer according to claim 3, characterized in that The oxidizing agent is one or more of benzoyl peroxide, ammonium persulfate, and sodium perborate; or / and the reducing agent is one or more of sodium sulfite, N,N-dimethylaniline, trimethylamine, and triethanolamine.

6. A preparation method of the oleic acid-modified polycarboxylate water reducer according to any one of claims 2 to 5, characterized in that The preparation raw materials include polyether monomer, acrylic acid, oleic acid, emulsifier, oxidant, reducing agent and thioglycolic acid. The raw materials are calculated by weight: 20 to 50 parts of polyether monomer, 3.0 to 6.0 parts of acrylic acid, 0.1 to 0.6 parts of oxidant, 0.03 to 0.3 parts of reducing agent, 0.1 to 1.0 parts of thioglycolic acid, the amount of oleic acid accounts for 3% to 20% of the mass of acrylic acid, the amount of emulsifier accounts for 1% to 9% of the mass of oleic acid, and the polyether monomer is one or more of allyl polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, and 3-methylbut-3-enyl polyoxyethylene ether. The preparation method of the oleic acid modified polycarboxylate water reducer is carried out as follows: First step, prepare solution A and solution B in advance. Solution A consists of the required amount of reducing agent, thioglycolic acid, and distilled water, and solution B consists of the required amount of acrylic acid and distilled water; Second step, add the required amount of polyether monomer to distilled water and stir until completely dissolved; Third step, add the required amount of emulsifier and oleic acid to the solution obtained in the second step, stir, and then add the required amount of oxidizing agent to the system, and continue to stir thoroughly at a certain temperature and stirring speed; Fourth step, slowly dropwise add solution A and solution B respectively. The dropping time of solution A is 1 hour to 3 hours, and the dropping time of solution B is 0.5 hour to 2.5 hours; Fifth step, after the dropping is completed, keep the temperature for reaction for 1 hour to 3 hours to obtain an oleic acid modified polycarboxylate water reducer showing a slightly milky white color; In the third step, the reaction temperature is 15°C to 45°C; the emulsifier is one or more of Tween 20, Tween 60, polyvinyl alcohol 1788, and Tween 80.

7. Application of the oleic acid modified polycarboxylate water reducer according to any one of claims 1 to 5 in improving the performance of concrete.

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