A low acid-ether ratio water reducing agent and its preparation method and application in concrete

Abstract

The present invention belongs to the technical field of additives for building concrete, and specifically relates to a catalyst, a low acid-ether ratio water reducer, a preparation method thereof, and an application thereof in concrete. The water reducer of the present invention has a compound shown in the following formula (I): The water reducer prepared by the present invention has a high conversion rate and has good performance in cement dispersion and concrete application, providing an effective means for solving the application of water reducers in concrete. Concrete mixed with ordinary water reducers will have water exudation, high concrete viscosity, and bottom scraping, while the concrete mixed with the water reducer prepared by the present invention is relatively soft, has improved wrapping, and improves the pumpability and comprehensive performance of the concrete, achieving significant advantages in industrial applications.

Description

Technical Field

[0001] The invention belongs to the technical field of additives for building concrete, and particularly relates to a low acid-to-ether ratio water reducer, a preparation method thereof and application in concrete. Background Art

[0002] The raw materials for preparing polycarboxylic acid water reducers are mainly divided into two categories: 1) polyether monomers (HPEG, TPEG); 2) reactive small monomers (acrylic acid, acrylate, etc.). Due to the differences in polymerization activity and reactivity ratio of these two types of monomers, it is difficult to prepare water reducer products with high conversion rate and excellent performance in a relatively low "reactive small monomer / polyether monomer (molar ratio, hereinafter referred to as acid-ether ratio)" polymerization system.

[0003] The main function of water reducer is to disperse cement particles. Its dispersion state (such as workability, encapsulation, etc.) is closely related to the acid-ether ratio selected when preparing the water reducer. High acid-ether ratio water reducer is easier to prepare, and the raw material conversion rate of the prepared product is high, showing a higher water reduction rate, but the concrete mixed with it has poor workability and encapsulation, and the slump retention ability is also poor.

[0004] The acid-ether ratio water-reducing agent commonly used in China now has poor adaptability to ground materials. The domestic high-quality ground materials have been almost exhausted by the vigorous development of construction over the years, and inferior ground materials have become the norm in industry applications, making the problems of conventional acid-ether ratio water-reducing agents in application more prominent.

[0005] The preparation of low acid-ether ratio water reducer is very difficult because the copolymerization activity of polyether monomer is poor and it is difficult to obtain a high raw material conversion rate at a low acid-ether ratio. Under the condition of low raw material conversion rate, the effective ingredients of the water reducer are insufficient and the concrete mixed with the water reducer is difficult to reach an ideal state.

[0006] The conventional polymerization method of water reducer is free radical polymerization. In order to reduce energy consumption, free radical-initiated polymerization is generally carried out at a relatively low temperature. The industry usually uses a redox system to initiate free radicals. This initiation system, under the premise of a low acid-ether ratio polymerization ratio, is difficult to obtain a high conversion rate while controlling the ideal molecular weight range. Summary of the invention

[0007] In order to improve the above technical problems, the present invention adopts a complex catalyst shown in the following formula (C):

[0008]

M x

[0009] Wherein, M is selected from metal ions, selected from Mg 2+ 、Al 3+ , Cu 2+ 、Ni2+ , Fe 3+ , Fe 2+ 、Ti 2+ One or more of;

[0010] L is a ligand containing a functional group, selected from one or more of a carbonyl compound, a phosphine-containing compound, and a nitrogen-containing compound; the carbonyl compound may be formic acid, acetic acid, oxalic acid, ammonium oxalate, etc.; the phosphine-containing compound may be a phosphonic acid compound or a salt thereof, such as hydroxyethylidene diphosphonic acid, pentasodium aminotrimethylene phosphonate, etc.; the nitrogen-containing compound may be sodium ethylenediaminetetraacetate, an ammonium salt, etc.; the coordination number x:y of the complex catalyst is 1:3 to 1:5.

[0011] The present invention also provides a method for preparing the catalyst, comprising reacting a salt containing the metal ions mentioned above with a chemical substance containing a functionalized group to prepare the catalyst.

[0012] According to an embodiment of the present invention, the reaction may be carried out in a solvent of water.

[0013] According to an embodiment of the present invention, the reaction may be carried out under heating conditions, for example, the reaction temperature may be 30 to 80°C, such as 40 to 60°C.

[0014] According to an embodiment of the present invention, the reaction time may be 0.5 to 10 hours, such as 2 to 4 hours.

[0015] According to an embodiment of the present invention, the mass ratio of the metal ion to the compound containing the functional group may be 1:1 to 10, preferably 1:1 to 6, and more preferably 1:2.

[0016] According to an embodiment of the present invention, the pH value of the reaction system may be 2 to 6. Optionally, the reaction may be carried out in the presence of a pH adjuster to allow the reaction to proceed at a desired pH value.

[0017] According to an embodiment of the present invention, the salt containing the above-mentioned metal ions is selected from at least one of titanium sulfate, ferrous sulfate, ferric sulfate, nickel sulfate, aluminum sulfate, copper sulfate and magnesium sulfate.

[0018] According to an embodiment of the present invention, the chemical substance containing a functional group is the above-mentioned ligand containing a functional group.

[0019] The present invention provides a polycarboxylate water reducer, the structure of which is a compound shown in the following formula (I):

[0020]

[0021] Wherein, R1, R2, and R3 are the same or different and are independently selected from H, C 1-4 Alkyl, -(CH2) m COOH, -(CH2) p OH, for example, selected from H, C 1-3 Alkyl, such as selected from H, methyl, ethyl;

[0022] m is an integer selected from 0 to 3, such as 0, 1, 2 or 3;

[0023] p is an integer selected from 1 to 4, such as 1, 2, 3 or 4;

[0024] R4, R5, R6 are the same or different and are independently selected from H, C 1-3 Alkyl; for example, selected from H, methyl;

[0025] Y is -O- or absent;

[0026] The ratio of a / b is selected from a number between 1.5 and 3.5;

[0027] n is a number from 22 to 130;

[0028] Wherein, the compound represented by formula (I) is prepared using the above catalyst.

[0029] According to an embodiment of the present invention, a / b may be an integer or a decimal, for example, it is selected from 1.5, 1.85, 2, 2.2, 2.5, 2.6, 3, 3.2, 3.5, preferably an integer or a decimal selected from 1.7 to 3.2.

[0030] According to an embodiment of the present invention, n may be an integer or a decimal, for example, selected from 22, 30, 40, 50, 55.5, 60, 70, 80, 90, 100, 110, 120, 130, preferably a number selected from 40-70.

[0031] According to an embodiment of the present invention, the compound represented by formula (I) is a polycarboxylate water-reducing agent.

[0032] According to an embodiment of the present invention, the weight average molecular weight of the compound represented by formula (I) is 8000-50000, for example, 20000-50000, such as 8000, 10000, 12000, 15000, 20000, 21000, 24000, 28500, 38000, 48000 or 50000.

[0033] According to an embodiment of the present invention, the number average molecular weight of the compound represented by formula (I) is 6000-30000, for example, 9000-30000, such as 6000, 6500, 9800, 11000, 13800, 15000, 24000, 27000, 30000.

[0034] According to an embodiment of the present invention, the peak molecular weight of the compound represented by formula (I) is 7000-50000, for example, 16000-46000, such as 7000, 7300, 9800, 11500, 13800, 16000, 17000, 21000, 25000, 37000, 38000, 45000.

[0035] According to an embodiment of the present invention, the raw materials for preparing the compound represented by formula (I) may include acrylic monomers and polyether monomers.

[0036] According to an embodiment of the present invention, the acrylic monomer can be selected from at least one of acrylic acid, maleic anhydride, itaconic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate; preferably acrylic acid.

[0037] According to an embodiment of the present invention, the polyether monomer may be selected from at least one of methyl allyl alcohol polyoxyethylene ether, isopentanol polyoxyethylene ether, allyl polyoxyethylene ether, and vinyl polyoxyethylene ether.

[0038] According to an embodiment of the present invention, the molar ratio of acrylic monomer to polyether monomer is (1.5-3.5):1, for example, 1.5:1, 1.8:1, 2:1, 2:2, 2.3:1, 2.5:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.5:1 or any value between any two ranges.

[0039] The present invention also provides a method for preparing the compound represented by formula (I), comprising: reacting a polyether monomer, an acrylic monomer, an initiator and a reducing agent to prepare the compound represented by formula (I).

[0040] According to an embodiment of the present invention, the preparation method is carried out in the presence of a chain transfer agent.

[0041] Preferably, the preparation method is carried out in the presence of the above catalyst.

[0042] Preferably, the preparation method is carried out in the presence of water.

[0043] According to an embodiment of the present invention, the initiator is selected from at least one of water-soluble free radical initiators such as hydrogen peroxide, persulfate or azobisisobutylamidine; the amount of the initiator can be 0.7-1.8% of the mass of the polyether monomer.

[0044] According to an embodiment of the present invention, the reducing agent is selected from at least one of L-ascorbic acid, Rongalite, sodium hypophosphite, sodium disulfite, ammonium ferrous sulfate, etc.;

[0045] The concentration of the reducing agent is 1-2 wt %; the amount of the reducing agent can be 0.1-0.4% of the mass of the polyether monomer, preferably 0.2-0.3%.

[0046] According to an embodiment of the present invention, the chain transfer agent is selected from at least one of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, sodium bisulfite, sodium hypophosphite, isopropanol, sodium methacrylic acid, sodium allyl sulfonate, etc. The amount of the chain transfer agent can be 0.1-2% of the mass of the polyether monomer.

[0047] According to an exemplary embodiment of the present invention, the preparation method may include the following steps:

[0048] S1. adding a polyether monomer, water and the above catalyst to a reactor;

[0049] S2. The acrylic acid ester monomer and water are mixed to prepare a dropwise solution A;

[0050] S3. The reducing agent and water are mixed evenly to prepare a dropwise addition solution B;

[0051] S4. The chain transfer agent and water are mixed evenly to prepare a dropwise addition liquid C;

[0052] S5. adding a portion of the acrylic monomer, a portion of the reducing agent, and / or a portion of the chain transfer agent to the reactor of step (1);

[0053] The droplet B in step S4 and the droplet C in step S5 can be separately used as droplets, or prepared together as one droplet;

[0054] S6. adding the initiator to the reactor in step S2;

[0055] S7. Control the droplet speed so that the droplet A, the droplet B, and the droplet C are synchronously added to the reactor in step S6. After the droplet addition is completed, the mixture is kept warm and matured; and then an alkaline compound is added to adjust the pH to obtain the water reducing agent.

[0056] According to an embodiment of the present invention, in step S1, the mass ratio of the polyether monomer to water is (1-1.5):1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1.

[0057] According to an embodiment of the present invention, in step S1, the polyether monomer is firstly mixed with water and then the catalyst is added and mixed evenly.

[0058] According to an embodiment of the present invention, in step S2, the mass concentration of the acrylic monomer is 30-60 wt%, for example, 30 wt%, 40 wt%, 50 wt% or 60 wt%.

[0059] According to an embodiment of the present invention, the molar ratio of acrylic monomer to polyether monomer is (1.5-3.5):1, for example, 1.5:1, 1.8:1, 2:1, 2.3:1, 2.5:1, 2.8:1, 3:1, 3.5:1 or any value between any two ranges.

[0060] According to an embodiment of the present invention, in step S5, the acrylic monomer may be an aqueous solution of the acrylic monomer; the reducing agent may be an aqueous solution of the reducing agent; and the chain transfer agent may be an aqueous solution of the chain transfer agent.

[0061] According to an embodiment of the present invention, in step S5, the portion of acrylic monomers is 0-50wt% of the total acrylic monomers, such as 0, 5wt%, 10wt%, 20wt%, 30wt%, 33wt%, 35wt%, 40wt%, 45wt%, 50wt% or any value in between any two ranges.

[0062] According to an embodiment of the present invention, in step S5, the portion of the reducing agent is 0-50wt% of the total reducing agent mass, such as 0, 5wt%, 10wt%, 20wt%, 30wt%, 33wt%, 35wt%, 40wt%, 45wt%, 50wt% or any value between any two ranges.

[0063] According to an embodiment of the present invention, in step S5, the portion of the chain transfer agent is 0-50wt% of the total chain transfer agent mass, such as 0, 5wt%, 10wt%, 20wt%, 30wt%, 33wt%, 35wt%, 40wt%, 45wt%, 50wt% or any value between any two ranges.

[0064] According to an embodiment of the present invention, in step S7, the insulation temperature is 15-34° C.; the aging time is 0 to 2 hours, preferably, the aging time is 1 hour.

[0065] According to an embodiment of the present invention, in step S7, the alkaline compound may be, for example, at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like.

[0066] According to an embodiment of the present invention, in step S7, the adjusted pH value is 2 to 6, preferably 5.

[0067] According to an embodiment of the present invention, in step S7, the starting temperature of the dropping is less than 25°C.

[0068] According to an embodiment of the present invention, in step S7, the heating rate during the dropwise addition is ≤1°C / 30min.

[0069] According to an embodiment of the present invention, the dripping liquids are controlled to be dripped simultaneously and the dripping is completed synchronously, and the dripping time is 1 to 7 hours.

[0070] The present invention also provides concrete, comprising the compound represented by formula (I).

[0071] The present invention also provides the use of the compound represented by formula (I) in concrete, preferably as a water reducing agent in concrete.

[0072] Beneficial Effects

[0073] (1) The present invention prepares an active catalyst, which can greatly improve the copolymerization activity of polyether monomers.

[0074] (2) When the catalyst of the present application is used to synthesize a water reducer, a product with high monomer conversion rate, controllable molecular weight and molecular weight distribution can be obtained.

[0075] (3) The water reducing agent prepared by the present invention has a high conversion rate and has good performance in cement dispersion and concrete application, which provides an effective means to solve the application of water reducing agent in concrete.

[0076] (4) The water reducer prepared by the present invention maintains a stable state in concrete applications, exhibits good initial water reduction and workability retention over time, and can effectively solve the problems of poor water reduction retention of ordinary water reducers and delayed water exudation of slow-release water reducers.

[0077] (5) Concrete mixed with ordinary water reducers will have water seepage, high concrete viscosity, and bottom scraping. However, concrete mixed with the water reducer prepared by the present invention shows smaller initial dispersion and lower viscosity. The amount of water reducer can be increased to use it as a viscosity-reducing water reducer for high-grade concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 This is the hydrogen NMR spectrum of the catalyst prepared in Example 1-2.

[0079] Figure 2 This is the gel chromatogram of the water reducing agent prepared in Example 2-1.

[0080] Figure 3 This is the H NMR spectrum of the water reducing agent prepared in Example 2-1.

[0081] Figure 4 This is the hydrogen NMR spectrum of the catalyst in Example 1-1.

[0082] Figure 5 It is the nuclear magnetic hydrogen spectrum of the catalyst in Example 1-3. DETAILED DESCRIPTION

[0083] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0084] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0085] Catalyst preparation

[0086] Example 1-1:

[0087] 1g titanium sulfate, 2g ferrous sulfate, 2g ethylenediaminetetraacetic acid disodium (EDTA-2Na), 4g hydroxyethylidene diphosphonic acid (HEDP) were dissolved in 90g water, the pH value of the reaction system was 2-6, and after reacting at 40°C for 2h, a stable complex aqueous solution was prepared, i.e., the catalyst shown in the following formula. The NMR hydrogen spectrum of the catalyst is as follows Figure 4 shown.

[0088]

[0089] Embodiment 1-2:

[0090] 1g of nickel sulfate, 2g of ferrous sulfate, 2g of ethylenediaminetetraacetic acid disodium (EDTA-2Na) and 4g of hydroxyethylidene diphosphonic acid (HEDP) were dissolved in 90g of water. The pH value of the reaction system was 2-6. After reacting at 40°C for 2h, a stable complex aqueous solution was prepared to obtain a catalyst with the following structure. The hydrogen nuclear magnetic spectrum of the catalyst is as follows: Figure 1 As shown:

[0091]

[0092] Embodiment 1-3:

[0093] 1g aluminum sulfate, 2g copper sulfate, 2g ammonium oxalate, and 4g aminotrimethylenephosphonic acid pentasodium were dissolved in 90g water, and the pH value of the reaction system was 2-6. After reacting at 50°C for 2h, a stable complex aqueous solution was prepared, i.e., a catalyst shown in the following structure. The NMR hydrogen spectrum of the catalyst is as follows Figure 5 shown.

[0094]

[0095] The deuterated reagent used in the nuclear magnetic resonance test of the catalysts in Examples 1-1 to 1-3 is deuterated water (produced by Qingdao Tenglong Microwave Technology Co., Ltd.).

[0096] Preparation of polycarboxylate water reducer

[0097] Example 2-1:

[0098] 45g of methyl allyl alcohol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-2 were put into a reactor and stirred to dissolve and mix evenly; 3.05g of acrylic acid and 5g of water were prepared as dropwise solution A, 0.1g of L-ascorbic acid, 0.4g of mercaptopropionic acid and 10g of water were prepared as dropwise solution B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T=20°C, ΔT=1°C / 30min, the remaining dropwise solutions A and B were added dropwise at a uniform speed, the addition was completed in 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and a water reducer sample (the acid-ether ratio of the water reducer a / b≈2.2) was obtained.

[0099] The sample corresponds to the GPC (gel chromatography) spectrum as shown Figure 2 shown.

[0100] The NMR spectrum of the water reducer is as follows Figure 3 shown. Figure 3 The integral of a (1.0-2.0 ppm) is 70, which is the integral area of ​​polyacrylic acid, and the integral of b (3.5-4.1 ppm) is 1100, which is the integral area of ​​polyether 2400. The calculation formula is (70 / 72): (1100 / 2400) = 2.2:1. The corresponding sample analysis indicators are shown in Table 1 below.

[0101] Table 1

[0102] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 28500 13800 25000 98.1

[0103] Example 2-2:

[0104] 45g of methyl allyl alcohol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-2 were put into a reactor and stirred to dissolve and mix evenly; 2.5g of acrylic acid and 5g of water were prepared as droplet A, 0.1g of L-ascorbic acid, 0.4g of mercaptopropionic acid and 10g of water were prepared as droplet B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T = 20°C, ΔT = 1°C / 30min, and the remaining droplets A and B were added dropwise at a uniform speed for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample was obtained (the acid-ether ratio of the water reducer was about a / b≈2.2). The corresponding sample analysis indicators are shown in Table 2 below.

[0105] Table 2

[0106] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 24000 11000 21000 95.9

[0107] Embodiment 2-3:

[0108] 45g of methyl allyl alcohol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-1 were put into a reactor and stirred to dissolve and mix evenly; 3g of acrylic acid, 1g of hydroxypropyl acrylate and 5g of water were prepared as droplet A, 0.1g of L-ascorbic acid, 0.4g of mercaptopropionic acid and 10g of water were prepared as droplet B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T = 20°C, ΔT = 1°C / 30min, and the remaining droplets A and B were added dropwise at a uniform speed for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample (the acid-ether ratio of the water reducer a / b≈2.6) was obtained. The corresponding sample analysis indicators are shown in Table 3 below.

[0109] Table 3

[0110] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 21000 9800 17000 96.7

[0111] Embodiment 2-4:

[0112] 45g of isopentanol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-1 were put into a reactor and stirred to dissolve and mix evenly; 3g of acrylic acid, 1g of n-butyl acrylate and 5g of water were prepared as droplet A, 0.15g of Rongalite and 5g of water were prepared as droplet B, and 0.4g of thioglycolic acid and 5g of water were prepared as droplet C; then 0.3g of hydrogen peroxide and 0.4g of ammonium persulfate were added to the reactor, the initial reaction temperature was controlled to be T=20°C, ΔT=1°C / 30min, and droplets A, B and C were added dropwise at a uniform speed for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample (the acid-ether ratio of the water reducer a / b≈2.6) was obtained. The corresponding sample analysis indicators are shown in Table 4 below.

[0113] Table 4

[0114] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 38000 15000 38000 97.7

[0115] Embodiment 2-5:

[0116] 45g of vinyl polyoxyethylene ether with Mn of 3000, 30g of water and 0.5g of the catalyst prepared in Example 1-3 were put into a reactor and stirred to dissolve and mix evenly; 3.5g of acrylic acid and 3.2g of water were prepared as droplet A, 0.1g of L-ascorbic acid, 0.7g of sodium hypophosphite and 10g of water were prepared as droplet B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.8g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T=20°C, ΔT=1°C / 30min, and the remaining droplets A and B were uniformly added dropwise for 1h, and the reaction was terminated by keeping warm for 0.5h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample (the acid-ether ratio of the water reducer a / b≈3.2) was obtained. The corresponding sample analysis indicators are shown in Table 5 below.

[0117] Table 5

[0118]

[0119]

[0120] Embodiment 2-6:

[0121] 45g of vinyl polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-3 were put into a reactor and stirred to dissolve and mix evenly; 2.5g of acrylic acid, 1g of hydroxypropyl acrylate and 5g of water were prepared as drop solution A, 0.1g of sodium hypophosphite, 0.7g of mercaptopropionic acid and 10g of water were prepared as drop solution B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T = 20°C, ΔT = 1°C / 30min, and the remaining drop solutions A and B were added dropwise at a uniform speed for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample was obtained (the acid-ether ratio of the water reducer was about a / b≈2.2). The corresponding sample analysis indicators are shown in Table 6 below.

[0122] Table 6

[0123] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 8000 6000 7300 94.5

[0124] Embodiment 2-7:

[0125] 45g of methyl allyl alcohol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-2 were put into a reactor and stirred to dissolve and mix evenly; 3.5g of acrylic acid and 5g of water were prepared as droplet A, 0.1g of L-ascorbic acid, 0.65g of mercaptopropionic acid and 10g of water were prepared as droplet B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T = 20°C, ΔT = 1°C / 30min, and the remaining droplets A and B were uniformly added dropwise for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample was obtained (the acid-ether ratio of the water reducer was about a / b≈2.6). The corresponding sample analysis indicators are shown in Table 7 below.

[0126] Table 7

[0127] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 10000 6500 9800 94.9

[0128] Embodiment 2-8:

[0129] 45g of isopentanol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-1 were put into a reactor and stirred to dissolve and mix evenly; 2g of acrylic acid, 1.5g of n-butyl acrylate and 5g of water were prepared as droplet A, 0.15g of Rongalite and 5g of water were prepared as droplet B, and 0.6g of thioglycolic acid and 5g of water were prepared as droplet C; then 0.3g of hydrogen peroxide and 0.4g of ammonium persulfate were added to the reactor, the initial reaction temperature T = 20°C, ΔT = 1°C / 30min, and droplets A, droplets B and droplets C were added at a uniform speed, and the reaction was completed in 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample (the acid-ether ratio of the water reducer a / b≈2.1) was obtained. The corresponding sample analysis indicators are shown in Table 8 below.

[0130] Table 8

[0131] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 12000 8000 11500 96.7

[0132] Embodiment 2-9:

[0133] 45g of methyl allyl alcohol polyoxyethylene ether with Mn of 2400, 30g of water and 0.5g of the catalyst prepared in Example 1-1 were put into a reactor and stirred to dissolve and mix evenly; 3.5g of acrylic acid and 5g of water were prepared as droplet A, 0.1g of L-ascorbic acid, 0.53g of mercaptopropionic acid and 10g of water were prepared as droplet B; 1 / 3 of A and B were put into the bottom of the reactor and homogenized, and then 0.6g of hydrogen peroxide was added to the reactor, the initial reaction temperature was controlled to be T = 20°C, ΔT = 1°C / 30min, and the remaining droplets A and B were uniformly added dropwise for 2h, and the reaction was terminated by keeping warm for 1h; after the reaction was completed, 30wt% of NaOH aqueous solution was added to adjust the pH to 5, and the desired water reducer sample (the acid-ether ratio of the water reducer a / b≈2.6) was obtained. The corresponding sample analysis indicators are shown in Table 9 below.

[0134] Table 9

[0135] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 15000 11000 13800 96.9

[0136] It can be seen from the above Examples 2-1 to 2-9 that the conversion rate of the low acid-to-ether ratio water reducer obtained by using the catalyst and preparation method of the present invention is greater than 94%, and the molecular weight and molecular weight distribution are controllable.

[0137] Application Examples

[0138] Comparative Example 1

[0139] Concrete was prepared from a commercially available water reducing agent sample (Jiangsu Chaoli Building Materials Technology Co., Ltd., brand C7 water reducing mother liquor, medium acid ether ratio water reducing agent: acid ether ratio ≈ 4.7, the polyether monomer used was methyl allyl polyoxyethylene ether, and the polyether molecular weight was 3000). The cement used was Southern 42.5 grade cement. The mother liquor information of Comparative Example 1 is shown in Table 10 below.

[0140] Table 10

[0141] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 46000 24000 45000 92.4

[0142] Comparative Example 2

[0143] Concrete prepared from a commercially available water-reducing agent sample (Jiangsu Chaoli Building Materials Technology Co., Ltd., brand C3 water-reducing mother liquor, medium acid-ether ratio water-reducing agent: acid-ether ratio ≈ 4.1, the polyether monomer used is methyl allyl polyoxyethylene ether, and the polyether molecular weight is 3000). The cement used is Southern 42.5 grade cement. The mother liquor information of Comparative Example 2 is shown in Table 11 below.

[0144] Table 11

[0145] Weight average molecular weight Mw Number average molecular weight Mn Peak molecular weight Mp Monomer conversion rate % 42000 26000 40000 84.6

[0146] Application Testing

[0147] Example 3-1

[0148] The water reducing agent samples in Examples 2-1 to 2-9 and Comparative Example 1-2 were used, the cement used was Southern 42.5 grade cement, and the water reducing agent solid content was 0.24 g; parallel comparative tests were performed under the same conditions and the same content.

[0149] The pure slurry test method was carried out in accordance with the national standard (GB8077-2008), and the results are shown in Table 12 below.

[0150] Table 12

[0151] Water reducing agent sample Initial clean pulp / mm Clean pulp 1h / mm Clean pulp 1.5h / mm Example 2-1 220 215 198 Example 2-2 200 202 195 Example 2-3 180 135 90 Embodiment 2-4 240 190 143 Embodiment 2-5 240 210 190 Embodiment 2-6 170 125 83 Embodiment 2-7 175 128 87 Embodiment 2-8 177 131 90 Embodiment 2-9 180 135 93 Comparative Example 1 250 185 130 Comparative Example 2 200 170 138

[0152] The tests in Tables 1-12 above show that the water-reducing agent provided by the present invention, when the molecular weight Mw = 8000-50000 and the acid-ether ratio = 1.5-3.5, exhibits good initial water reduction and the ability to maintain the pure slurry during operation, and can be used as a commercial concrete water-reducing agent.

[0153] Example 3-2

[0154] The water reducers prepared in Examples 2-6 to 2-9 were tested in parallel with increasing dosage (Comparative Examples 1 and 2) for pure slurry. The cement used was Southern 42.5 grade cement. Under the same conditions, the solid dosage of the water reducers in Examples 2-6 to 2-9 was 0.45g, and the parallel comparison samples (water reducers in Comparative Examples 1 and 2) were tested in parallel with a dosage of 0.3g.

[0155] The slurry purification method is in accordance with the national standard (GB8077-2008). The comparison results are shown in Table 13 below.

[0156] Table 13

[0157] Water reducing agent number Initial clean pulp / mm Clean pulp 1h / mm Clean pulp 1.5h / mm Water seepage scraper Embodiment 2-6 300 320 300 slight Embodiment 2-7 300 330 310 slight Embodiment 2-8 300 330 320 slight Embodiment 2-9 310 335 330 slight Comparative Example 1 330 350 240 serious Comparative Example 2 300 330 260 serious

[0158] The above tests show that the water reducer provided by the present invention has a smaller initial dispersion when the molecular weight Mw is 8000-15000 and the acid-ether ratio is 1.5-3.5. Therefore, the slurry mixed with the low molecular weight water reducer exhibits a lower viscosity, and the amount of the water reducer can be increased to use it as a viscosity-reducing water reducer for high-grade concrete.

[0159] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a water reducing agent, comprising: The polyether monomer, the acrylic monomer, the initiator and the reducing agent are reacted to prepare a water reducing agent; The preparation method is carried out in the presence of a chain transfer agent and a complex catalyst represented by formula (C); The complex catalyst represented by formula (C) is: 【M x 】L y (C) Wherein, M is selected from metal ions, selected from Mg 2+ 、Al 3+ , Cu 2+ 、Ni 2+ , Fe 3+ , Fe 2+ 、Ti 2+ One or more of; L is a ligand containing a functional group, and the coordination number x:y is 1:3-1:5; the preparation method of the catalyst comprises reacting a salt of M with a chemical substance containing a functional group to prepare the catalyst; the chemical substance containing a functional group is selected from one or more of a carbonyl compound, a phosphine-containing compound, and a nitrogen-containing compound; the carbonyl compound is formic acid, acetic acid, oxalic acid or ammonium oxalate; the phosphine-containing compound is hydroxyethylidene diphosphonic acid or pentasodium aminotrimethylene phosphonate; the nitrogen-containing compound is sodium ethylenediaminetetraacetate or an ammonium salt; The weight average molecular weight of the water reducer is 8000-50000; The amount of the initiator is 0.7-1.8% of the mass of the polyether monomer; The acrylic monomer is selected from at least one of acrylic acid, maleic anhydride, itaconic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate; The polyether monomer is selected from at least one of methyl allyl alcohol polyoxyethylene ether, isopentanol polyoxyethylene ether, allyl polyoxyethylene ether and vinyl polyoxyethylene ether; The molar ratio of acrylic monomer to polyether monomer is (1.5~3.5):

1.

2. The method according to claim 1, wherein: The salt of M is selected from at least one of titanium sulfate, ferrous sulfate, ferric sulfate, nickel sulfate, aluminum sulfate, copper sulfate and magnesium sulfate.

3. The method according to claim 1, wherein: The number average molecular weight of the water reducer is 6000-30000; The peak molecular weight of the water reducer is 7000-30000. The method according to claim 1 , wherein the preparation method is carried out in the presence of water.

5. The method according to claim 1, wherein: The initiator is selected from at least one of hydrogen peroxide, persulfate or azobisisobutylamidine; The reducing agent is at least one selected from L-ascorbic acid, Rongalite, sodium hypophosphite, sodium disulfite, and ammonium ferrous sulfate; The chain transfer agent is selected from at least one of sodium hypophosphite, mercaptoethanol, thioglycolic acid, mercaptopropionic acid, sodium bisulfite, isopropanol, sodium methacrylic acid, and sodium allyl sulfonate.

6. The method according to claim 1, wherein: The amount of the reducing agent is 0.1-0.4% of the mass of the polyether monomer; The amount of the chain transfer agent used is 0.1-2% of the mass of the polyether monomer.

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