Viscosity-reducing polycarboxylate water reducer and preparation method thereof

Abstract

The application discloses a viscosity-reducing polycarboxylic water reducing agent and a preparation method thereof. The viscosity-reducing polycarboxylic water reducing agent is prepared from an intermediate C obtained by an amide / imide reaction of a compound A and a compound B, and copolymerization of the intermediate C with monomer D, monomer E and monomer F; the compound A is an amino polyether, and the compound B is a carboxylic acid containing a mercapto group; the monomer D is an unsaturated carboxylic acid, the monomer E is a polymerizable sulfonic acid monomer, and the monomer F is a polymerizable phosphonic acid monomer. The prepared viscosity-reducing polycarboxylic water reducing agent has the advantages of low dosage, high water reducing rate, small slump loss, and significant reduction of paste viscosity, especially at a low water-binder ratio. The method has the advantages of simple synthesis method, high yield, low process requirement, low production cost and small environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures in building materials, specifically to a viscosity-reducing polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] High-strength, high-pumpability, and high-durability concrete has become an inevitable trend in the development of modern concrete technology. To improve concrete strength, high-strength cement, increased cementitious material content, and reduced water-cement ratio are commonly used. These measures lead to increased concrete viscosity, slower flow rate, increased construction difficulty, and lower construction efficiency, which greatly limits the promotion and application of high-strength concrete.

[0003] Currently, common methods for reducing the viscosity of high-strength concrete include increasing the dosage of water-reducing agents, adding air-entraining agents, optimizing the particle size distribution of binders, and adding viscosity-reducing agents. However, increasing the dosage of water-reducing agents can easily lead to new problems in fresh concrete, such as bleeding and excessive retardation; it also increases costs, resulting in a low cost-effectiveness ratio. Adding air-entraining agents reduces concrete viscosity by introducing air bubbles to reduce friction between aggregate particles, but this can negatively impact the strength of high-strength concrete. Optimizing the particle size distribution of binders, such as adding admixtures like fly ash, can reduce concrete viscosity, but its viscosity-reducing effect on ultra-high-performance concrete is limited and does not fundamentally solve the problem. In recent years, newly emerging organic viscosity-reducing agents have shown significant viscosity-reducing effects, but due to their small molecular weight and low water-reduction rate, they are unable to meet the dual requirements of water reduction and viscosity reduction in high-strength concrete.

[0004] Patent US20050228142A1 reports a block polycarboxylic acid, prepared by atom transfer radical polymerization of a polyether macromonomer and an unsaturated acid. Patent CN104371071A reports a hyperbranched polycarboxylic acid concrete high-efficiency water-reducing agent prepared by self-condensation vinyl polymerization of a polymerizable monomer possessing both haloacylhalide groups and unsaturated carboxylic acid groups and a polyether macromonomer. The above methods belong to controlled radical polymerization, which requires harsh reaction conditions and suffers from drawbacks such as the difficulty and high cost of initiator preparation.

[0005] Patent CN102532558A reports a synthetic method employing a pre-polymerization followed by functionalization approach. First, a carboxyl-containing polymer backbone is formed. Then, branches are introduced by grafting with terminal amino polyethers and polyethylene glycol monoalkyl ethers at a specific temperature through amidation and esterification reactions. This yields a polycarboxylic acid-based water-reducing agent whose backbone is linked by both amide / imide bonds and ester bonds. However, the esterification reaction is reversible and has a slow reaction rate.

[0006] Patent CN102993430B describes the reaction of alkenyl glycidyl ether and alkyl-terminated amino polyether to obtain an intermediate for a high-strength water-reducing agent. The intermediate is then reacted with unsaturated carboxylic acids and / or unsaturated carboxylates to obtain the high-strength water-reducing agent. Patent CN107652405A describes the synthesis of a polycarboxylic acid water-reducing agent by amide / imide-forming an amino-terminated polyether amine, followed by copolymerization with an active monomer. The water-reducing agent obtained by this preparation method has a traditional comb-like structure, thus its performance improvement has reached a bottleneck. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to overcome the problems of insufficient initial dispersion performance and high early viscosity of concrete caused by traditional polycarboxylate superplasticizers at low water-cement ratios, and provides a viscosity-reducing polycarboxylate superplasticizer and its preparation method that has readily available raw materials, low production costs, and simple production processes.

[0008] This invention provides a viscosity-reducing polycarboxylate superplasticizer, which is obtained by an intermediate C obtained through an amide / imide reaction between compound A and compound B, and then by copolymerizing intermediate C with monomers D, E, and F.

[0009] The molar ratio of compound A to compound B is 1:1.05 to 1:2;

[0010] The molar ratio of intermediate C to monomers D, E, and F satisfies: C / (D+E+F)=1 / 1~1 / 7, and monomers D, E, and F are mixed in any proportion.

[0011] Compound A is an amino polyether, represented by general formula (Ⅰ):

[0012]

[0013] In formula (Ⅰ), R1 is H, CH3 or CH2CH3, and x, y and z are the average number of moles of polyoxypropylene (PO) added, each of which is independently chosen as an integer from 1 to 30;

[0014] The compound B is a thiol-containing carboxylic acid, specifically selected from one or more of mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and L-2-amino-3-mercaptopropionic acid in any proportion, but not limited thereto;

[0015] The monomer D is an unsaturated carboxylic acid, represented by the general formula (II):

[0016]

[0017] In formula (II), R2 is H or CH3; R3 is H or m is an integer satisfying 0 ≤ m ≤ 3, when When present, it can form an anhydride with COOM1 in general formula (II); M1 is H, alkali metal ions, 1 / 2 alkaline earth metal ions, ammonium ions or organic amine groups;

[0018] The monomer E is a polymerizable sulfonic acid monomer, represented by general formula (Ⅲ):

[0019]

[0020] In formula (Ⅲ), R4 is H or CH3, and R5 is CH2, C=ONHC(CH3)2CH2 or M2 is H or an alkali metal ion; the monomer E is specifically selected from sodium methyl propylene sulfonate, sodium propylene sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, and sodium p-styrene sulfonate, mixed in any proportion.

[0021] The monomer F is a polymerizable phosphonic acid monomer, represented by general formula (Ⅳ):

[0022]

[0023] In formula (Ⅳ), R6 is H or CH3; n is the number of carbon atoms, which is an integer from 2 to 4; M3 is H, alkali metal ion, 1 / 2 alkaline earth metal ion, ammonium ion or organic amine group.

[0024] The monomer F can be synthesized in a variety of ways according to existing technologies: (1) Phosphoric acid reacts with alcohol at high temperature and water is removed by a dehydrating agent to improve the reaction yield (US20080108732). (2) Phosphorylation of alcohol (CN1158132A, US20090258969).

[0025] The preparation method of monomer F of the present invention is as follows: unsaturated carboxylic acid ester and phosphorylation reagent are reacted at a temperature of 50-120°C, preferably 50-90°C;

[0026] The phosphorylating agent is selected from any one of phosphorus pentoxide, phosphoric acid, polyphosphoric acid, and pyrophosphoric acid.

[0027] The phosphorylation reaction time is 1 to 6 hours, preferably 2 to 4 hours;

[0028] The structure of the unsaturated carboxylic acid ester conforms to general formula (V):

[0029]

[0030] The unsaturated carboxylic acid ester is selected from any one of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0031] The monomer F is selected from any one or more of hydroxyethyl methacrylate phosphate, hydroxyethyl acrylate phosphate, hydroxypropyl acrylate phosphate, and hydroxypropyl methacrylate phosphate, mixed in any proportion.

[0032] This invention also provides a method for preparing the aforementioned viscosity-reducing polycarboxylate superplasticizer, the specific preparation steps of which are as follows:

[0033] (1) Amide / imide reaction: Compound A and compound B were heated to 60°C under nitrogen protection, and after adding a catalyst, the temperature was slowly increased to 80-130°C and held at the temperature for 2-6 hours. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0034] The catalyst is selected from any one or two of 4-dimethylaminopyridine, concentrated sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, and ethylsulfonic acid in any proportion, and its amount is 0.05% to 10% of the mass of compound A.

[0035] (2) Copolymerization reaction: The amino polyether intermediate C with thiol end obtained in step (1) is subjected to free radical copolymerization reaction with monomers D, E and F in an aqueous medium under the action of an initiator to obtain the viscosity-reducing polycarboxylic acid water-reducing agent.

[0036] The initiator is a conventional free radical water-soluble initiator, selected from any one or more of water-soluble azo initiators, ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount used is 0.5% to 5.0% of the total weight of intermediate C, monomer D, monomer E, and monomer F.

[0037] When implementing step (2) of the present invention, intermediate C, due to its relatively low copolymerization activity, is added to the reaction vessel before the reaction begins in order to improve its conversion rate; the aqueous solutions of monomers D, E, and F, as well as the aqueous solution of the initiator, are added to the reaction vessel dropwise after the reaction begins (in step 2, the aqueous solutions of monomers D, E, F, and the initiator are prepared first, and the concentration varies slightly depending on the polymerization concentration of the total monomers, as long as the total monomer concentration of the reaction is 20-60 wt%), and the dropwise addition time is controlled at 2-6 h, the polymerization reaction time is controlled at 4-8 h; the polymerization concentration of the total monomers in the reaction is controlled at 20-60 wt%, and the polymerization temperature is controlled at 40-80 °C.

[0038] The viscosity-reducing water-reducing agent of the present invention has a weight-average molecular weight of 5000-50000 Da; if the weight-average molecular weight of the viscosity-reducing water-reducing agent is too small or too large, the water-reducing and slump-retaining properties will deteriorate.

[0039] The application method of the viscosity-reducing water-reducing agent of this invention is as follows: its dosage is 0.05% to 0.5% of the total weight of cementitious materials. As an improvement, the dosage of the viscosity-reducing water-reducing agent of this invention is 0.08% to 0.3 wt%. If the dosage is too low, the dispersion effect on cement will not be satisfactory; if the dosage is too high, it will result in economic waste, and the dispersion effect will not be further improved.

[0040] The application method of the viscosity-reducing cement dispersant described in this invention is the same as that of existing water-reducing agents, except for a slight difference in dosage. Those skilled in the art are generally aware that the specific dosage is related to the type of water-reducing agent used.

[0041] The viscosity-reducing water-reducing agent described in this invention can also be used in combination with at least one type of water-reducing agent selected from known aminosulfonic acid-based water-reducing agents, lignin-based common water-reducing agents, and existing polycarboxylate water-reducing agents. In addition to the known concrete water-reducing agents mentioned above, air-entraining agents, expanding agents, retarders, early-strength agents, viscosity-increasing agents, shrinkage-reducing agents, and defoamers can also be added.

[0042] The viscosity-reducing polycarboxylate superplasticizer product prepared by this invention has advantages such as low dosage, high water reduction rate, small slump loss, and significant reduction in slurry viscosity, especially at low water-cement ratios. The method of this invention has the advantages of simple synthesis, high yield, low process requirements, low production cost, and minimal environmental pollution.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The method of the present invention has the advantages of readily available raw materials, low production cost, simple production process and low environmental pollution;

[0045] (2) The viscosity-reducing water-reducing agent prepared by the method of the present invention has the advantages of low dosage, high water reduction rate, small slump loss and good cement adaptability. In particular, it performs well in overcoming the problems of insufficient initial dispersion performance and large early viscosity of concrete when the traditional polycarboxylate water-reducing agent has a low water-cement ratio. Attached Figure Description

[0046] Figure 1 The rheological properties of mortar obtained by the viscosity-reducing water-reducing agent obtained in Examples 1, 2 and 3 of this invention and the traditional comb-shaped water-reducing agent obtained in the comparative example are shown. Detailed Implementation

[0047] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0048] To better understand the present invention, the following description, in conjunction with specific embodiments, further illustrates the invention.

[0049] In this embodiment of the invention, the weight-average molecular weight Mw of the polymer was determined using a miniDAWNTristar aqueous gel permeation chromatography (GPC) instrument manufactured by Wyatt Technology Corporation. The experimental conditions were as follows: column: TSK-GELSW (TOSOH), eluent: 0.1M NaNO3, flow rate: 0.8ml / min, injection: 20μl 0.1% aqueous solution (differential refractive index detector).

[0050] Comparative Example

[0051] 30.0 g of water was added to a four-necked flask equipped with a stirrer, thermometer, and dropping device. The temperature was raised to 90°C. Simultaneously, 100.0 g of polyethylene glycol monomethyl ether methacrylate (Mn = 1000 g / mol), a mixed monomer solution of 18.0 g of acrylic acid and 44.0 g of water, a mixed solution of 1.8 g of ammonium persulfate and 50.0 g of water, and a mixed solution of 1.21 g of sodium bisulfite and 50.0 g of water were added dropwise to the reactor over a period of 3 hours. After the addition was completed, the mixture was kept at this temperature for 2 hours. Then, 14.3 g of 35% NaOH solution was added for neutralization, yielding a polycarboxylate superplasticizer mother liquor (Mw = 24.53 kDa). It is worth noting that this formulation is a laboratory formulation of a commercially available superplasticizer.

[0052] Example 1

[0053] (1) Amide / imide reaction: 88.0g of amino polyether (x+y+z=5~6, Mw=440) and 36.8g of mercaptoacetic acid were heated to 60℃ under nitrogen protection, 8.8g of ethyl sulfonic acid was added, and the temperature was slowly raised to 80℃ and held for 6h. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0054] (2) Copolymerization reaction: 129.0g of deionized water was added to 193.8g of the amino polyether intermediate C with thiol groups obtained in step (1). The reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 40℃ and stirred until homogeneous. Then 27.9g of sodium acrylate (in the general formula of monomer D, R1=H, R2=H) and 28.2g of sodium methacrylate (in the general formula of monomer E, R4=CH3) were added. 291.2g of hydroxyethyl acrylate phosphate, 27.1g of ammonium persulfate and 235.1g of water were mixed and stirred to prepare a uniform monomer aqueous solution. This solution was added dropwise to the reactor over a period of 6 hours. After the addition was complete, the reaction was kept at the temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer with a solid content of 59.8% (Mw = 0.85kDa).

[0055] Example 2

[0056] (1) Amide / imide reaction: 88.0g of amino polyether (x+y+z=5~6, Mw=440) and 19.3g of mercaptoacetic acid were heated to 60℃ under nitrogen protection, 4.4g of p-toluenesulfonic acid was added, and the temperature was slowly raised to 100℃ and held at a constant temperature for 4h. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0057] (2) Copolymerization reaction: 141.0g of deionized water was added to 211.8g of the amino polyether intermediate C with thiol groups obtained in step (1). The reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 60℃ and stirred until homogeneous. Then 25.8g of methacrylic acid (in the general formula of monomer D, R1=CH3, R2=H) and 71.1g of sodium methacrylate (in the general formula of monomer E, R4=CH3) were added. 117.7g of hydroxyethyl acrylate phosphate, 8.5g of azobisisobutyramidine hydrochloride and 285.2g of water were mixed and stirred to prepare a homogeneous monomer aqueous solution. The solution was added dropwise to the reactor over a period of 3 hours. After the addition was complete, the reaction was kept at the temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer with a solid content of 49.9% (Mw = 4.89kDa).

[0058] Example 3

[0059] (1) Amide / imide reaction: 450.0g of amino polyether (x+y+z=50, Mw=3000) and 25.4g of 2-mercaptopropionic acid were heated to 60℃ under nitrogen protection, 13.5g of benzenesulfonic acid was added, and the temperature was slowly raised to 110℃ and held at a constant temperature for 3h. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0060] (2) Copolymerization reaction: 148.0g of deionized water was added to 221.3g of the terminal thiol-containing amino polyether intermediate C obtained in step (1). The reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 60℃ and stirred until homogeneous. Then, 22.3g of maleic acid (in the general formula of monomer D, R1 = H, ), 55.4g sodium propylene sulfonate (monomer E, in the general formula R4=H, 40.4g of hydroxyethyl methacrylate phosphate, 10.2g of sodium persulfate and 361.8g of water were mixed and stirred to prepare a uniform monomer aqueous solution. This solution was added dropwise to the reactor over a period of 4 hours. After the addition was complete, the reaction was kept at the temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer (Mw = 3.22kDa) with a solid content of 39.7%.

[0061] Example 4

[0062] (1) Amide / imide reaction: 450.0g of amino polyether (x+y+z=50, Mw=3000) and 21.8g of L-2-amino-3-mercaptopropionic acid were heated to 60℃ under nitrogen protection, 4.5g of concentrated sulfuric acid was added, and the temperature was slowly raised to 100℃ and kept at a constant temperature for 4h. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0063] (2) Copolymerization reaction: 102.0g of deionized water was added to 153.2g of the amino polyether intermediate C with thiol groups obtained in step (1), the reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 80℃ and stirred until homogeneous; then 18.7g of itaconic anhydride (in the general formula of monomer D, R1=H, And forms an anhydride with COOM1), 103.5g 2-acrylamide-2-methylpropanesulfonic acid (in the general formula of monomer E, R4=H, 17.5g of hydroxypropyl acrylate phosphate, 2.9g of azobisisobutyramidine hydrochloride and 581.2g of water were mixed and stirred to prepare a uniform monomer aqueous solution. The solution was added dropwise to the reactor over a period of 2 hours. After the addition was complete, the reaction was kept at the same temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer with a solid content of 30.2% (Mw = 1.69kDa).

[0064] Example 5

[0065] (1) Amide / imide reaction: 500.0g of amino polyether (x+y+z=85, Mw=5000) and 14.8g of 3-mercaptopropionic acid were heated to 60℃ under nitrogen protection, and 10.0g of 4-dimethylaminopyridine was added. The temperature was then slowly raised to 120℃ and held for 3h. The mixture was then cooled to obtain amino polyether intermediate C with thiol groups at the end.

[0066] (2) Copolymerization reaction: 168.0 g of deionized water was added to 252.7 g of the amino polyether intermediate C with thiol groups at the end obtained in step (1). The reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 70 °C and stirred until homogeneous. Then 15.1 g of 2-methylmaleic anhydride (in the general formula of monomer D, R1 = CH3, And forms an anhydride with COOM1), 111.2g of sodium p-styrenesulfonate (in the general formula of monomer E, R4 = H, 10.1g of hydroxypropyl methacrylate phosphate, 15.6g of potassium persulfate and 415.3g of water were mixed and stirred to prepare a uniform monomer aqueous solution. This solution was added dropwise to the reactor over a period of 3 hours. After the addition was complete, the reaction was kept at the same temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer (Mw = 2.25kDa) with a solid content of 39.9%.

[0067] Example 6

[0068] (1) Amide / imide reaction: 500.0g of amino polyether (x+y+z=85, Mw=5000) and 19.1g of 3-mercaptopropionic acid were heated to 60℃ under nitrogen protection, 0.3g of concentrated sulfuric acid was added, and the temperature was slowly raised to 130℃ and held for 2h. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end.

[0069] (2) Copolymerization reaction: 112.0g of deionized water was added to 168.5g of the amino polyether intermediate C with thiol groups obtained in step (1). The reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 50℃ and stirred until homogeneous. Then, 1.0g of methacrylic acid (in the general formula of monomer D, R1 = CH3, R2 = H) and 13.7g of sodium p-styrene sulfonate (in the general formula of monomer E, R4 = H) were added. 0.5g of hydroxypropyl methacrylate phosphate, 0.9g of ammonium persulfate and 622.3g of water were mixed and stirred to prepare a uniform monomer aqueous solution. This solution was added dropwise to the reactor over a period of 5 hours. After the addition was complete, the reaction was kept at the same temperature for 2 hours and then cooled to room temperature to obtain a viscosity-reducing polycarboxylate superplasticizer with a solid content of 20.1% (Mw = 3.85kDa).

[0070] Application Examples

[0071] In the application examples, the cement used was Onoda PII 52.5, Conch P·O 42.5 produced by Anhui Conch Cement Co., Ltd., and Helin P·O 42.5 produced by Jiangsu Helin Cement Co., Ltd. The sand was medium sand with a fineness modulus M = 2.6, and the gravel was continuously graded crushed stone with a particle size of 5-20mm.

[0072] In application examples, the test methods for water reduction rate, bleeding rate, air content, and setting time shall be carried out in accordance with the relevant provisions of GB8077-2012 "Test Method for Homogeneity of Concrete Admixtures".

[0073] Application Example 1

[0074] The effects of the viscosity-reducing water-reducing agent synthesized in the evaluation examples and the traditional comb-shaped water-reducing agent synthesized in the comparative examples on the fluidity of fresh cement paste and its loss over time were investigated. The water-cement ratio was fixed at 0.29, and Onoda PII52.5 was used. The experimental results are shown in Table 1.

[0075] Table 1. Effects of different water-reducing agents on the fluidity and time-dependent loss of freshly mixed cement paste.

[0076]

[0077] The traditional comb-shaped water-reducing agent synthesized in the comparative example, at a water-cement ratio of 0.29 and a dosage of 0.12%, had an initial paste flowability of 227 mm and a paste flowability of 177 mm after 30 minutes; at a dosage of 0.14%, the initial paste flowability was 244 mm and the paste flowability after 30 minutes was 203 mm. The viscosity-reducing water-reducing agent synthesized in the examples, at a dosage of 0.12% of the cement weight, generally exhibited better initial paste flowability and paste flowability after 30 minutes than the comparative example. For example, in Example 3, the initial paste flowability was 277 mm and the paste flowability after 30 minutes was 263 mm. Therefore, compared to traditional comb-shaped cement dispersants, the viscosity-reducing water-reducing agent has the characteristics of low dosage, high water reduction rate, and excellent slump retention.

[0078] Application Example 2

[0079] The effects of the conventional comb-shaped water-reducing agent synthesized in the comparative example and the viscosity-reducing water-reducing agent synthesized in Examples 2, 3 and 5 on fresh concrete were evaluated. The water-cement ratio was fixed at 0.41, and the amount of polycarboxylate solids was adjusted to make the initial slump of the fresh concrete 23cm±2cm. The experimental results are shown in Table 2.

[0080] Table 2 shows the effects of the conventional comb-shaped water-reducing agent synthesized in the comparative examples and the viscosity-reducing water-reducing agent synthesized in the examples on the properties of fresh concrete.

[0081]

[0082] The conventional comb-shaped water-reducing agent synthesized in the comparative example had an initial slump of 20.0 cm, a 30-minute time loss of 16.5 cm, an initial spread of 48.0 cm, and a 30-minute time loss of 38.0 cm when the dosage was 0.14%; and an initial slump of 24.0 cm, a 30-minute time loss of 20.0 cm, an initial spread of 60.0 cm, and a 30-minute time loss of 48.0 cm when the dosage was 0.18%. In the examples, the viscosity-reducing water-reducing agent synthesized at a dosage of 0.14% of the cement weight showed better initial slump and spread of the freshly mixed mortar, as well as better slump and spread after 30 minutes, compared to the comparative example. For instance, the viscosity-reducing water-reducing agent synthesized in Example 3, at a dosage of 0.14% of the cement weight, showed virtually no change in the air content of the concrete, and its slump and spread were better than the comparative example. Specifically, the initial slump was 24.5 cm, the 30-minute time loss was 21.0 cm, the initial spread was 62.0 cm, and the 30-minute time loss was 56.0 cm. Therefore, compared to the traditional comb-shaped water-reducing agent synthesized in the comparative example, the viscosity-reducing water-reducing agent exhibits superior dispersion performance, higher water reduction rate, lower dosage, and smaller slump loss.

[0083] Application Example 3

[0084] The adaptability of the viscosity-reducing water-reducing agents obtained in Examples 1, 3, and 5 and the traditional comb-shaped water-reducing agent obtained in the comparative example to different cements was evaluated. The water-cement ratio was fixed at 0.29, and the results of the paste fluidity are shown in Table 3.

[0085] Table 3. Compatibility of viscosity-reducing water-reducing agents with different types of cement.

[0086]

[0087] When the water-cement ratio is fixed at 0.29, the cement with the viscosity-reducing agent has good initial fluidity and good dispersion retention properties, regardless of the type of cement, indicating that the viscosity-reducing water-reducing agent has good adaptability in different types of cement.

[0088] Application Example 4

[0089] The rheological properties of mortar obtained from Examples 1, 2, and 3 (viscosity-reducing water-reducing agents) and the traditional comb-shaped water-reducing agent obtained from the comparative example were evaluated. The admixture dosage was adjusted to make the initial spread of fresh mortar 270mm ± 5mm. The experimental results are shown in [Figure 1]. Figure 1 And Table 2.

[0090] Table 4 shows the effect of the conventional comb-shaped water-reducing agent synthesized in the comparative examples and the viscosity-reducing water-reducing agents synthesized in Examples 1, 2, and 3 on the rheological properties of mortar.

[0091]

[0092] Under a fixed shear rate, the apparent viscosity of the slurry can be calculated by dividing the shear stress by the shear rate. In the rheological testing program, the rheometer automatically calculates the shear viscosity under each shear rate condition. Therefore, the apparent viscosity described in Table 4 is for a shear rate of 80 s⁻¹. -1 The shear viscosity at that time. From Figure 1 It can be seen that, regardless of the type of water-reducing agent added, the shear stress of the mortar increases with the increase of the shear rate. Under the same shear rate conditions, the shear stress of the mortar containing the comparative example is greater than that of the example.

[0093] In summary, under the same water-cement ratio, to achieve the same degree of spread, the dosage of viscosity-reducing polycarboxylate is reduced by 30% compared with traditional polycarboxylate, indicating that the water reduction of viscosity-reducing polycarboxylate is greater than that of traditional polycarboxylate, and the mortar has better workability. The V funnel time is shortened by 40% compared with the comparative example, and the apparent viscosity is reduced by 22% compared with the comparative example.

Claims

1. A viscosity-reducing polycarboxylate superplasticizer, characterized in that, The viscosity-reducing polycarboxylate superplasticizer is obtained by intermediate C, which is obtained by amide / imide reaction of compound A and compound B, and intermediate C is then copolymerized with monomers D, E and F. The molar ratio of compound A to compound B is 1:1.05 to 1:2; The molar ratio of intermediate C to monomers D, E, and F satisfies: C / (D+E+F) = 1 / 1 to 1 / 7, and monomers D, E, and F are mixed in any proportion. The compound A is an amino polyether, represented by the general formula (Ⅰ): （Ⅰ） In formula (Ⅰ), R1 is H, CH3 or CH2CH3, and x, y and z are the average number of moles of polyoxypropylene (PO) added, each of which is independently chosen as an integer from 1 to 30; Compound B is a carboxylic acid containing a thiol group; The monomer D is an unsaturated carboxylic acid, represented by the general formula (II): （Ⅱ） In formula (II), R2 is H or CH3; R3 is H or m is an integer satisfying 0 ≤ m ≤ 3, when When present, it can form an acid anhydride with COOM1 in general formula (II); M1 is H, alkali metal ion, 1 / 2 alkaline earth metal ion, ammonium ion or organic amine group; The monomer E is a polymerizable sulfonic acid monomer, represented by the general formula (Ⅲ): （Ⅲ） In formula (Ⅲ), R4 is H or CH3, and R5 is CH2, C=ONHC(CH3)2CH2 or M2 consists of H and alkali metal ions; The monomer F is a polymerizable phosphonic acid monomer, represented by the general formula (Ⅳ): （Ⅳ） In formula (Ⅳ), R6 is H or CH3; n is the number of carbon atoms, which is an integer from 2 to 4; M3 is H, alkali metal ion, 1 / 2 alkaline earth metal ion, ammonium ion or organic amine group.

2. The viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, Compound B is selected from any one or more of mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and L-2-amino-3-mercaptopropionic acid, mixed in any proportion.

3. The viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, The monomer E is selected from sodium methacrylate sulfonate, sodium acrylate sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, and sodium p-styrene sulfonate, and mixed in any proportion.

4. A viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, The monomer F is prepared by reacting an unsaturated carboxylic acid ester and a phosphorylation reagent at a temperature of 50-120℃; the phosphorylation reaction time is 1-6 h. The phosphorylation reagent is selected from any one of phosphorus pentoxide, phosphoric acid, and polyphosphoric acid. The structure of the unsaturated carboxylic acid ester conforms to general formula (V): （Ⅴ）。 5. A viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In the preparation method of monomer F, the reaction temperature is 50~90℃ and the phosphorylation reaction time is 2~4 h.

6. A viscosity-reducing polycarboxylate superplasticizer according to claim 4 or 5, characterized in that, The unsaturated carboxylic acid ester is selected from any one of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate; The monomer F is selected from any one or more of hydroxyethyl methacrylate phosphate, hydroxyethyl acrylate phosphate, hydroxypropyl acrylate phosphate, and hydroxypropyl methacrylate phosphate, mixed in any proportion.

7. A method for preparing a viscosity-reducing polycarboxylate superplasticizer according to any one of claims 1 to 6, characterized in that, The specific preparation steps are as follows: (1) Amide / imide reaction: Compound A and compound B were heated to 60°C under nitrogen protection, and after adding a catalyst, the temperature was slowly increased to 80-130°C and held at the temperature for 2-6 hours. The temperature was then lowered to obtain amino polyether intermediate C with thiol groups at the end. The catalyst is selected from any one or two of 4-dimethylaminopyridine, concentrated sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, and ethylsulfonic acid in any proportion, and its amount is 0.05% to 10% of the mass of compound A; (2) Copolymerization reaction: The amino polyether intermediate C with thiol groups at the end obtained in step (1) undergoes free radical copolymerization reaction with monomers D, E, and F in an aqueous medium under the action of an initiator to obtain the viscosity-reducing polycarboxylic acid water-reducing agent; The initiator is a conventional free radical water-soluble initiator, selected from any one or more of water-soluble azo initiators, ammonium persulfate, sodium persulfate, and potassium persulfate, and is used in an amount of 0.5% to 5.0% of the total weight of intermediate C, monomer D, monomer E, and monomer F. The viscosity-reducing water-reducing agent has a weight-average molecular weight of 5000~50000 Da.

8. The method for preparing a viscosity-reducing polycarboxylate superplasticizer according to claim 7, characterized in that, In step (2), intermediate C is added to the reaction vessel before the reaction begins. The aqueous solutions of monomers D, E, and F, as well as the aqueous solution of the initiator, are added to the reaction vessel dropwise after the reaction begins. The dropwise addition time is controlled at 2 to 6 hours, and the polymerization reaction time is controlled at 4 to 8 hours. In step (2), the total monomer concentration of the reaction is controlled at 20~60wt%, and the polymerization temperature is controlled at 40~80℃.

9. The method of applying a viscosity-reducing polycarboxylate superplasticizer according to any one of claims 1 to 6, characterized in that, The dosage of the viscosity-reducing water-reducing agent is 0.05% to 0.5% of the total weight of the cementitious materials.

10. The application method of the viscosity-reducing polycarboxylate superplasticizer according to claim 9, characterized in that, The dosage of the viscosity-reducing water-reducing agent is 0.08~0.3wt% of the total weight of the cementitious materials.

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