Viscosity reduction type polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the technical field of water reducing agents, and particularly discloses a viscosity reduction type polycarboxylic acid water reducing agent and a preparation method thereof. The viscosity reduction type polycarboxylate superplasticizer is prepared by compounding a macromolecular polymer and a pre-wrapping micromolecule polymer in a weight ratio of (1.7-2.3): 1; the molecular weight of the macromolecular polymer is between 75000 and 85000; the pre-wrapped small molecule polymer comprises a small molecule polymer, a thickening agent and water in a weight ratio of 1000: (0.7-1.3): (8-10); and the molecular weight of the small molecular polymer is between 14000 and 16000. The viscosity reducer is prepared by compounding a macromolecular polymer and a micromolecular polymer according to a certain proportion, the linkage viscosity reduction effect is achieved, the viscosity of high-performance concrete slurry is effectively reduced, the adaptability of a concrete admixture is improved, and the problem that high-performance concrete site construction is difficult is solved.

Description

Technical Field

[0001] The present application relates to the technical field of water reducers, and in particular to a viscosity-reducing polycarboxylic acid water reducer and a preparation method thereof. Background Art

[0002] With the rapid development of my country's construction and infrastructure, the number of highway, railway, bridge, tunnel and high-rise building projects is increasing. Polycarboxylic acid-based high-performance water reducers are widely used in high-performance concrete due to their high strength and good workability. In practical applications, in order to improve the strength of concrete, high-strength grade cement, increased amount of cementitious materials, and reduced water-cement ratio are usually used. At the same time, the advancement of cement production technology has made the cement finer and increased the water demand of cement. These factors will lead to an increase in concrete viscosity, a slower flow rate, increased construction difficulty and reduced construction efficiency, which greatly limits the application of high-performance concrete.

[0003] At present, the common methods to reduce the viscosity of concrete are to increase the dosage of water reducer, optimize the particle gradation of adhesive, compound air entraining agent and viscosity reducer, etc. When dealing with high-performance concrete, technicians often encounter problems such as segregation and bottoming of concrete caused by increasing the dosage of water reducer; the mix ratio of raw materials and concrete on site cannot be adjusted or optimized on a large scale; the adaptability of air entraining agent is poor due to the complexity and diversity of concrete raw materials, and it has an adverse effect on the strength of concrete; the viscosity reducer has no significant effect on reducing viscosity and cannot improve the excessive viscosity of concrete.

[0004] As the viscosity problem of concrete becomes increasingly prominent, the development of viscosity-reducing polycarboxylic acid water-reducing agents has become a research hotspot in recent years. Viscosity-reducing water-reducing agents can release free water from the pore fluid of concrete during application, thereby achieving the effect of reducing viscosity. However, the reduction in the surface tension of the slurry can easily lead to an increase in the air content, affecting the mechanical properties of concrete.

[0005] Therefore, it is of great significance to develop a viscosity-reducing low-molecular-weight polycarboxylic acid water-reducing agent that can effectively reduce viscosity, has no adverse effects on the mechanical properties of concrete, and can improve the workability of concrete. It can effectively avoid the limitations and adaptability of the effective viscosity-reducing effect brought about by compound viscosity-reducing additives, and has broad application prospects in high-performance concrete such as high-strength, high-grade self-compacting concrete. Summary of the invention

[0006] In order to solve the above technical problems, the present application provides a viscosity-reducing polycarboxylate water-reducing agent and a preparation method thereof. The present application provides a viscosity-reducing polycarboxylate water-reducing agent, wherein the viscosity-reducing polycarboxylate water-reducing agent is compounded by a macromolecular polymer and a pre-wrapped small molecule polymer in a weight ratio of 1.7-2.3:1; The macromolecular polymer specifically comprises the following components in parts by weight: 280-380 parts of ether macromonomer; 10-25 parts of benzene ring functional monomer; 28-45 parts of unsaturated acid; 0.8-1.8 parts of reducing agent; 3-6 parts of chain transfer agent; 2.7-3.8 parts of oxidant; and water; the molecular weight of the macromolecular polymer is between 75000 and 85000; The pre-wrapped small molecule polymer comprises a small molecule polymer, a thickener, and water in a weight ratio of 1000:0.7-1.3:8-10; the small molecule polymer specifically comprises the following components in parts by weight: 200-300 parts of ether macromonomer; 50-100 parts of viscosity-reducing ether macromonomer; 8-18 parts of functional monomer; 25-40 parts of unsaturated acid; 0.5-1.4 parts of reducing agent; 2.2-6.8 parts of chain transfer agent; 2.8-4.2 parts of oxidant; and water; the molecular weight of the small molecule polymer is between 14000 and 16000; The thickener is selected from sodium polyacrylate with a molecular weight of 10,000 or carboxymethyl cellulose with a molecular weight of 10,000.

[0007] Preferably, the viscosity-reducing polycarboxylic acid water-reducing agent is compounded by a macromolecular polymer and a pre-wrapped small molecular polymer in a weight ratio of 1.9-2.1:1.

[0008] Preferably, the pre-wrapped small molecule polymer comprises the small molecule polymer, the thickener and water in a weight ratio of 1000:0.9-1.1:8.5-9.5.

[0009] Preferably, the molecular weight of the ether macromonomer is 2400 or 3000, and the ether macromonomer is selected from one or more of methyl allyl polyoxyethylene ether, isopentanol polyoxyethylene ether, propenol polyoxyethylene ether, allyl polyethylene glycol, methoxy polyethylene glycol ether, and vinyloxy polyethylene glycol ether; the molecular weight of the viscosity-reducing ether macromonomer is 600 or 1200, and the viscosity-reducing ether macromonomer is selected from one or more of methyl allyl polyoxyethylene ether, isopentanol polyoxyethylene ether, propenol polyoxyethylene ether, allyl polyethylene glycol, methoxy polyethylene glycol ether, and vinyloxy polyethylene glycol ether.

[0010] Preferably, the benzene ring functional monomer is selected from one or more of ferulic acid, styrene, 1-allyl-4-fluorobenzene, 1-phenylvinylboronic acid, and 4-methoxy-2-vinylaniline.

[0011] Preferably, the functional monomer is selected from one or more of methyl acrylate, methyl methacrylate, propyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, 2-hydroxyethyl methacrylate phosphate, and ammonium acrylate.

[0012] Preferably, the unsaturated acid is selected from one or more of acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and fumaric acid.

[0013] Preferably, the reducing agent is selected from one or more of sodium sulfite, sodium bisulfite, ascorbic acid, ferrous sulfate, sodium hypophosphite, bleaching agent, and E51.

[0014] Preferably, the chain transfer agent is selected from one or more of thioglycolic acid, mercaptopropionic acid, sodium hypophosphite, mercaptoethanol, and dodecyl mercaptan.

[0015] Preferably, the oxidant is selected from one or more of potassium persulfate, sodium bisulfite, ammonium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide.

[0016] Preferably, the thickener is selected from one or more of acrylic acid monomers, pentaerythritol cross-linked copolymers, carboxymethyl cellulose, and water-soluble sodium polyacrylate with a molecular weight of 2000-50000.

[0017] In a second aspect, the present application provides a method for preparing the above-mentioned viscosity-reducing polycarboxylate water-reducing agent, which specifically comprises the following steps: (1) Synthesis of macromolecular polymer: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (1.1) Add the bottom raw materials into a four-necked flask: add ether macromonomer, deionized water and 10-25% of unsaturated acid; (1.2) Prepare the components of material A: add the remaining unsaturated acid, benzene ring work unit, deionized water, and stir thoroughly; (1.3) Prepare the components of material B: add reducing agent, chain transfer agent, deionized water, and stir thoroughly; (1.4) Place the four-necked flask in a water bath, turn on the stirring to make the materials stir evenly, and set the ambient temperature to 20-40°C; After stirring evenly, add the oxidant to the four-necked flask while stirring, and continue stirring for 5-10 minutes; Start dripping material A and material B at the same time while stirring. Material A should be dripped for 80-120 minutes; material B should be dripped for 90-140 minutes. Keep the temperature at the end of the dropwise addition for 50-150 minutes; After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a macromolecular polymer with a molecular weight between 75000 and 85000 can be obtained; (2) Synthesis of small molecule polymers: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (2.1) Add the bottom raw materials into a four-necked flask: ether macromonomer and viscosity-reducing ether macromonomer, deionized water and 10-25% of unsaturated acid; (2.2) Prepare the components of material A: add the remaining unsaturated acid, functional monomer, and deionized water, and stir thoroughly; (2.3) Prepare the components of material B: add reducing agent, chain transfer agent, deionized water, and stir thoroughly; (2.4) Place the four-necked flask in a water bath, turn on the stirring to mix the materials evenly, and set the ambient temperature to 20-40°C; After stirring evenly, add the oxidant or reductant to the four-necked flask while stirring, and continue stirring for 5-10 minutes; Start dripping material A and material B at the same time while stirring. Material A should be dripped for 80-120 minutes; material B should be dripped for 90-140 minutes. Keep the temperature at the end of the dropwise addition for 50-150 minutes; After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a small molecular polymer with a molecular weight between 14000-16000 can be obtained; (3) Preparation of pre-wrapped small molecule polymers: Dissolve the thickener in deionized water, add it to the small molecule polymer after dissolution, stir and mix thoroughly to obtain; (4) pre-mix the macromolecular polymer and the pre-wrapped small molecule polymer according to a certain proportion, stir until completely mixed, to obtain.

[0018] The present application provides a viscosity-reducing polycarboxylic acid water-reducing agent and a preparation method thereof, which effectively reduces the viscosity of high-performance concrete paste, improves the adaptability of concrete admixtures and solves the problem of difficult on-site construction of high-performance concrete. The preparation process first uses a plurality of macromonomers with different molecular weights in combination, and by adjusting the initiator system concentration, acid-ether ratio, chain transfer agent, type and amount of functional monomers, initial reaction environment temperature, etc., a macromolecular polymer and a small molecular polymer that can effectively reduce the viscosity of concrete paste are obtained respectively, and then the small molecular polymer is premixed with a thickener, and finally the two polymers are compounded in a certain proportion for use, which has a significant effect on reducing the viscosity of concrete.

[0019] The viscosity-reducing polycarboxylate water-reducing agent prepared in the present application has a green and environmentally friendly production process, wherein the molecular weight of the macromolecular polymer is controlled between 75,000 and 85,000, and the molecular weight of the small molecule polymer is controlled between 14,000 and 16,000. By optimizing the design of the molecular structure of the polycarboxylate water-reducing agent, the macromolecular polymer increases the hydrophilicity of the PCE (polycarboxylate water-reducing agent) to reduce the plastic viscosity of the cement slurry, and improves the dispersibility and increases the lubrication between particles by adjusting the thickness of the water film layer around the particles. The small molecule polymer is released after the thickener is hydrolyzed by alkali, and can play a role in assisting dispersion and lubrication. Under the linkage effect, the viscosity of the concrete slurry can be effectively reduced, and there is no adverse effect on the bulk density and mechanical properties of the concrete, and the workability of the concrete can be improved.

[0020] In summary, the technical solution of this application has the following effects: The viscosity-reducing polycarboxylic acid water-reducing agent described in the present application is prepared by compounding a macromolecular polymer and a small molecular polymer in a certain ratio, and exerts a linkage viscosity-reducing effect.

[0021] Benzene ring groups are added to macromolecular polymers during the polymerization process. The grafted benzene ring groups increase the polarity of the polymer, lock in more free water and increase the thickness of the water film layer. The increase in polarity increases the steric hindrance between molecules, improves the dispersion performance, and manifests itself as a decrease in the viscosity of the concrete.

[0022] By designing the molecular structure of small molecule polymers, the molecular weight is controlled between 14,000 and 16,000 while ensuring sufficient electrostatic repulsion and steric hindrance. It plays an auxiliary dispersion role in the pore solution of cement slurry, helps to disperse cement particles, does not affect the normal adsorption of PCE, and can be dissolved in the pore solution to provide lubrication between particles and reduce friction, thereby achieving a viscosity reduction effect.

[0023] The small molecule polymer is coated with a thickener in advance and then compounded with the large molecule polymer in proportion. When the viscosity-reducing water-reducing agent is added to the concrete, the large molecule polymer is normally adsorbed, dispersed and viscosity-reduced. Furthermore, the sodium polyacrylate coated on the outside of the small molecule polymer is hydrolyzed in the alkaline environment of the cement slurry to release the small molecule polymer. The small molecule polymer is dissolved in the pore solution and provides lubrication. The two aspects have a synergistic viscosity-reducing effect on the concrete. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application. Example

[0025] Example 1 Example 1 provides a viscosity-reducing polycarboxylate water-reducing agent.

[0026] The types of raw materials in Example 1 are as follows.

[0027] Raw materials of macromolecular polymer: ether macromonomer: HPEG (2400), benzene ring functional monomer: 4-methoxy-2-vinylaniline, unsaturated acid: acrylic acid, reducing agent: Vc, oxidizing agent: hydrogen peroxide, chain transfer agent: mercaptopropionic acid.

[0028] Small molecule polymer raw materials: ether macromonomer: HPEG (2400), viscosity-reducing ether macromonomer: APEG (600), unsaturated acid: acrylic acid, functional monomer: methyl acrylate, reducing agent: Vc, oxidizing agent: hydrogen peroxide, chain transfer agent: mercaptopropionic acid.

[0029] Pre-coated thickener: sodium polyacrylate (10000).

[0030] The raw material amounts of each raw material in Example 1 are shown in Table 1.

[0031] Table 1 Amount of each raw material in Example 1 The preparation method of the viscosity-reducing polycarboxylic acid water-reducing agent in Example 1 is specifically as follows.

[0032] (1) Synthesis of macromolecular polymer: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (1.1) Add the following raw materials to a four-necked flask: ether macromonomer, deionized water and partially unsaturated acid acrylic acid; (1.2) Prepare the components of material A: add all the remaining unsaturated acrylic acid, benzene ring work units, and deionized water, and stir thoroughly; (1.3) Prepare the components of material B: add reducing agent, chain transfer agent mercaptopropionic acid, and deionized water, and stir thoroughly; (1.4) Place the four-necked flask in a water bath, turn on the stirring to make the materials stir evenly, and set the ambient temperature to 35°C; After stirring evenly, add the oxidant to the four-necked flask while stirring, and continue stirring for 5-10 minutes; Start to add material A and material B at the same time while stirring. Material A is added for 120 minutes; material B is added for 135 minutes. Keep the temperature at the end of the dropwise addition for 60 minutes; After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a macromolecular polymer with a molecular weight between 75000 and 85000 can be obtained; (2) Synthesis of small molecule polymers: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (2.1) Add the bottom materials into a four-necked flask: macromonomer, deionized water, APEG and part of acrylic acid; (2.2) Prepare the components of material A: add all the remaining acrylic acid, methyl acrylate, and deionized water, and stir thoroughly; (2.3) Prepare the components of material B: add Vc, chain transfer agent mercaptopropionic acid, and deionized water, and stir thoroughly; (2.4) Place the four-necked flask in a room temperature environment and start stirring to mix the materials evenly. The ambient temperature is about 20°C.

[0033] After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0034] While stirring, material A and material B were added dropwise simultaneously. Material A was added dropwise for 110 min; material B was added dropwise for 130 min.

[0035] Maintain the temperature at the end of the dropwise addition for 60 minutes.

[0036] After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a small molecular polymer with a molecular weight between 14000-16000 can be obtained; (3) Preparation of pre-wrapped small molecule polymers: The weight ratio of the small molecule polymer, thickener and water is 1000:1:9; the thickener is dissolved in deionized water, and after the dissolution is complete, it is added to the small molecule polymer, and the mixture is stirred and mixed thoroughly to obtain the product; (4) Premix the macromolecular polymer and the pre-wrapped small molecular polymer: The materials are respectively extracted into a stirring kettle or a compounding tank in a ratio of 1:1 between the macromolecular polymer and the pretreated small molecular polymer, and stirred evenly to obtain the product.

[0037] Example 2 Example 2 provides a viscosity-reducing polycarboxylate water-reducing agent.

[0038] The types of raw materials in Example 2 are as follows.

[0039] Raw materials of macromolecular polymer: ether macromonomer: HPEG (2400), benzene ring functional monomer: styrene, unsaturated acid: acrylic acid, reducing agent: Vc, oxidizing agent: hydrogen peroxide, chain transfer agent: mercaptopropionic acid.

[0040] Small molecule polymer raw materials: ether macromonomer: HPEG (2400), viscosity-reducing ether macromonomer: APEG (1200), unsaturated acid: acrylic acid, functional monomer: hydroxypropyl acrylate, reducing agent: Vc, oxidizing agent: hydrogen peroxide, chain transfer agent: mercaptopropionic acid.

[0041] Pre-coated thickener: carboxymethyl cellulose (10000).

[0042] The raw material amounts of each raw material in Example 2 are shown in Table 2.

[0043] Table 2 Amounts of raw materials in Example 2 The preparation method of the viscosity-reducing polycarboxylic acid water-reducing agent in Example 2 is specifically as follows.

[0044] (1) Add the bottom raw materials of the kettle, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the proportion of the macromolecular polymer; (1.1) Add the bottom materials into a four-necked flask: macromonomer, deionized water and part of acrylic acid; (1.2) Prepare the components of material A: add all the remaining acrylic acid, styrene, and deionized water and stir thoroughly; (1.3) Prepare the components of material B: add reducing agent and deionized water and stir thoroughly; (1.4) Place the four-necked flask in a water bath, turn on the stirring function to mix the materials evenly, and set the water bath temperature to about 40°C; After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0045] While stirring, material A and material B were added dropwise simultaneously. Material A was added dropwise for 120 minutes, and material B was added dropwise for 132 minutes.

[0046] Maintain the temperature at the end of the dropwise addition for 60 minutes.

[0047] After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a macromolecular polymer with a molecular weight between 75,000 and 85,000 can be obtained.

[0048] (2) Synthesis of small molecule polymers: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (2.1) Add the bottom materials into a four-necked flask: macromonomer, deionized water, APEG and part of acrylic acid; (2.2) Prepare the components of material A: add all the remaining acrylic acid, hydroxypropyl acrylate, and deionized water, and stir thoroughly; (2.3) Prepare the components of material B: add Vc, mercaptopropionic acid, and deionized water, and stir thoroughly; (2.4) Place the four-necked flask in a room temperature environment and start stirring to mix the materials evenly. The ambient temperature is about 20°C.

[0049] After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0050] While stirring, material A and material B were added dropwise simultaneously. Material A was added dropwise for 120 minutes, and material B was added dropwise for 132 minutes.

[0051] Maintain the temperature at the end of the dropwise addition for 60 minutes.

[0052] After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a small molecular polymer with a molecular weight between 14000 and 16000 can be obtained.

[0053] (3) Preparation of pre-wrapped small molecule polymers: The weight ratio of the small molecule polymer, thickener and water is 1000:1:9; the thickener is dissolved in deionized water, and after the dissolution is complete, it is added to the small molecule polymer, and the mixture is stirred and mixed thoroughly to obtain the product; (4) Mix the macromolecular polymer and the pre-wrapped small molecular polymer in a ratio of 2:1 and stir evenly.

[0054] Embodiment 3-4 Examples 3-4 respectively provide a viscosity-reducing polycarboxylic acid water-reducing agent.

[0055] The difference between the above embodiment and embodiment 2 lies in the compounding ratio of the macromolecular polymer and the pre-wrapped small molecular polymer.

[0056] In Example 3, the weight ratio of the macromolecular polymer to the pre-wrapped small molecular polymer is 1.7:1.

[0057] In Example 4, the weight ratio of the macromolecular polymer to the pre-wrapped small molecular polymer is 2.3:1.

[0058] The remaining steps of the above embodiment are the same as those of embodiment 2.

[0059] Embodiment 5-6 Examples 5-6 each provide a viscosity-reducing polycarboxylic acid water-reducing agent.

[0060] The difference between the above embodiment and embodiment 2 lies in the weight ratio of the small molecule polymer, the thickener and the water in the pre-wrapped small molecule polymer.

[0061] In Example 5, the weight ratio of small molecule polymer, thickener and water is 1000:0.7:8 In Example 6: the weight ratio of the small molecule polymer, the thickener, and water is 1000:1.3:10.

[0062] The remaining steps of the above embodiment are the same as those of embodiment 2.

[0063] Comparative Example Comparative Example 1 This comparative example provides a water reducing agent.

[0064] Commercially available viscosity-reducing polycarboxylic acid water-reducing agent mother liquor, solid content 40%.

[0065] Comparative Example 2 This comparative example provides a water reducing agent.

[0066] The types of raw materials in this comparative example are as follows.

[0067] Ether macromonomer: HPEG (2400), benzene ring work unit: 4-methoxy-2-vinylaniline, unsaturated acid: methacrylic acid, reducing agent: E51, oxidizing agent: hydrogen peroxide, chain transfer agent: sodium hypophosphite.

[0068] The amount of each raw material used in this comparative example is shown in Table 3.

[0069] Table 3 Amount of each raw material in comparative example 2 The preparation method of the viscosity-reducing polycarboxylic acid water-reducing agent in this comparative example is specifically as follows.

[0070] Add the bottom raw materials, the components of material A and the components of material B into a four-necked flask according to the proportions; (1) Add the following raw materials to a four-necked flask: macromonomer, deionized water, chain transfer agent and part of methacrylic acid; (2) Prepare the components of material A: add all the remaining methacrylic acid, benzene ring functional monomers, and deionized water, and stir thoroughly; (3) Prepare the components of material B: add E51 and deionized water, and stir thoroughly; (4) Place the four-necked flask in a room temperature environment and start stirring to mix the materials evenly. The ambient temperature is about 20°C.

[0071] After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0072] While stirring, material A and material B were added dropwise at the same time. Material A was added dropwise for 90 minutes, and material B was added dropwise for 110 minutes.

[0073] Maintain the temperature at the end of the dropwise addition for 60 minutes.

[0074] After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, so as to obtain a macromolecular polymer with a molecular weight between 75000 and 85000; it can be used as a water reducing agent.

[0075] Comparative Example 3 This comparative example provides a water reducing agent.

[0076] The types of raw materials in this comparative example are as follows.

[0077] Ether macromonomer: GPEG (3000), viscosity-reducing ether macromonomer: methoxy polyethylene glycol ether, unsaturated acid: acrylic acid, functional monomer: acrylamide, reducing agent: E51, oxidizing agent: hydrogen peroxide, chain transfer agent: mercaptoethanol.

[0078] The amount of each raw material used in this comparative example is shown in Table 4.

[0079] Table 4 Amount of each raw material in comparative example 3 The preparation method of the viscosity-reducing polycarboxylic acid water-reducing agent in this comparative example is specifically as follows.

[0080] Add the bottom raw materials, the components of material A and the components of material B into a four-necked flask according to the proportions; (1) Add the bottom raw materials into a four-necked flask: macromonomer, deionized water, acrylamide and viscosity-reducing ether macromonomer; (2) Prepare the components of material A: add acrylic acid and deionized water and stir thoroughly; (3) Prepare the components of material B: add E51, mercaptoethanol, and deionized water and stir thoroughly; (4) Place the four-necked flask in a water bath, turn on the stirring to make the materials evenly stirred, and set the water bath temperature to about 30°C.

[0081] After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0082] While stirring, material A and material B were added dropwise simultaneously. Material A was added dropwise for 100 min; material B was added dropwise for 125 min.

[0083] Maintain the temperature at the end of the dropwise addition for 75 minutes.

[0084] After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a small molecular polymer with a molecular weight between 14000 and 16000 can be obtained; it can be used as a water reducing agent.

[0085] Comparative Example 4 This comparative example provides a water reducing agent (common water reducing polycarboxylate water reducing agent).

[0086] The types of raw materials in this comparative example are as follows.

[0087] Ether macromonomer: GPEG (3000), unsaturated acid: acrylic acid, reducing agent: Vc, oxidizing agent: hydrogen peroxide, chain transfer agent: sodium hypophosphite.

[0088] The raw material dosage of each raw material in this comparative example is shown in Table 5.

[0089] Table 5 Amount of each raw material in Comparative Example 4 The preparation method of the viscosity-reducing polycarboxylic acid water-reducing agent in this comparative example is specifically as follows.

[0090] Add the bottom raw materials, the components of material A and the components of material B into a four-necked flask according to the proportions; (1) Add the following raw materials to a four-necked flask: C6 monomer, deionized water and part of acrylic acid; (2) Prepare the components of material A: add all the remaining acrylic acid, functional monomers, and deionized water, and stir thoroughly; (3) Prepare the components of material B: add reducing agent, deionized water, and sodium hypophosphite, and stir thoroughly; (4) Place the four-necked flask in a negative temperature water bath, turn on the stirring to make the materials stir evenly, and set the ambient temperature to 10°C.

[0091] After stirring evenly, add hydrogen peroxide into the four-necked flask and continue stirring for 5-10 minutes.

[0092] While stirring, material A and material B were added dropwise at the same time. Material A was added dropwise for 45 minutes, and material B was added dropwise for 55 minutes.

[0093] Maintain the temperature at the end of the dropwise addition for 60 minutes.

[0094] After the insulation is completed, add deionized water to dilute and stir until uniform.

[0095] Performance testing The prepared water reducers were subjected to cement paste comparison tests.

[0096] Test condition 1: According to GB / T8077-2012 "Test method for homogeneity of concrete admixtures", the cement paste base cement is 600 grams, the designed water-cement ratio is 0.20, the water is 120 grams (the water in the water reducer needs to be deducted), and the water reducer solid content is set to 0.45%. The fluidity of the prepared water reducer paste and the Marsh emptying time of the paste are tested respectively.

[0097] The Marsh emptying time test uses a standard inverted cone funnel. The experimental design is that after 250 ml of cement slurry is placed in the funnel, the timing starts when the bottom valve is opened. The time taken to completely empty the slurry is tested to evaluate the differences in viscosity reduction performance of each group of water reducers.

[0098] Test results: as shown in Table 6.

[0099] It can be seen from the table that the fluidity of each group is within the range of 260±5 mm. Under the same initial fluidity, the viscosity-reducing polycarboxylic acid water-reducing agent Marsh prepared in Example 2 has a fast emptying time and excellent mother liquor viscosity-reducing performance.

[0100] Test condition 2: According to GB / T8077-2012 "Test method for homogeneity of concrete admixtures", the cement paste base cement is 600 grams, the designed water-cement ratio is 0.18, the water is 108 grams (the water in the water reducer needs to be deducted), and the water reducer solid content is set to 0.55%. The fluidity of the prepared water reducer paste and the Marsh emptying time of the paste are tested respectively.

[0101] The Marsh emptying time test uses a standard inverted cone funnel. The experimental design is that after 250 ml of cement slurry is placed in the funnel, the timing starts when the bottom valve is opened. The time taken to completely empty the slurry is tested to evaluate the differences in viscosity reduction performance of each group of water reducers.

[0102] The experimental results are shown in Table 6 below; It can be seen from the table that after reducing the water-binder ratio to 0.18 and increasing the reduced-solid dosage, the fluidity of each group is within the range of 260±5mm. Under the same initial fluidity, the viscosity-reducing polycarboxylic acid water-reducing agent Marsh prepared in Example 2 has a fast emptying time and excellent mother liquor viscosity-reducing performance.

[0103] Test condition 3: According to GB / T8077-2012 "Test method for homogeneity of concrete admixtures", the cement paste base cement is 600 grams, the designed water-cement ratio is 0.16, the water is 96 grams (the water in the water reducer needs to be deducted), the water-reducing agent is set to 0.70% in terms of solid content, and the fluidity of the prepared water reducer and the Marsh emptying time of the paste are tested respectively.

[0104] The Marsh emptying time test uses a standard inverted cone funnel. The experimental design is that after 250 ml of cement slurry is placed in the funnel, the timing starts when the bottom valve is opened. The time taken to completely empty the slurry is tested to evaluate the differences in viscosity reduction performance of each group of water reducers.

[0105] The experimental results are shown in Table 6 below; It can be seen from the table that after reducing the water-binder ratio to 0.16 and increasing the reduced-solid content to 0.70%, the fluidity of each group is within the range of 260±5mm. Under the same initial fluidity, the viscosity-reducing polycarboxylic acid water-reducing agent Marsh prepared in Example 2 has a fast emptying time and excellent mother liquor viscosity-reducing performance.

[0106] Table 6 Performance test results of water reducing agent in examples and comparative examples Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A viscosity-reducing polycarboxylate water-reducing agent, characterized in that: The viscosity-reducing polycarboxylic acid water-reducing agent is obtained by compounding a macromolecular polymer and a pre-wrapped small molecular polymer in a weight ratio of 1.7-2.3:1; The macromolecular polymer specifically comprises the following components in parts by weight: 280-380 parts of ether macromonomer; 10-25 parts of benzene ring functional monomer; 28-45 parts of unsaturated acid; 0.8-1.8 parts of reducing agent; 3-6 parts of chain transfer agent; 2.7-3.8 parts of oxidant; and water; the molecular weight of the macromolecular polymer is between 75000 and 85000; The pre-wrapped small molecule polymer comprises a small molecule polymer, a thickener, and water in a weight ratio of 1000:0.7-1.3:8-10; the small molecule polymer specifically comprises the following components in parts by weight: 200-300 parts of ether macromonomer; 50-100 parts of viscosity-reducing ether macromonomer; 8-18 parts of functional monomer; 25-40 parts of unsaturated acid; 0.5-1.4 parts of reducing agent; 2.2-6.8 parts of chain transfer agent; 2.8-4.2 parts of oxidant; and water; the molecular weight of the small molecule polymer is between 14000 and 16000; The thickener is selected from sodium polyacrylate with a molecular weight of 10,000 or carboxymethyl cellulose with a molecular weight of 10,000.

2. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The molecular weight of the ether macromonomer is 2400 or 3000, and the ether macromonomer is selected from one or more of methyl allyl polyoxyethylene ether, isopentanol polyoxyethylene ether, propenol polyoxyethylene ether, allyl polyethylene glycol, methoxy polyethylene glycol ether, and vinyloxy polyethylene glycol ether; the molecular weight of the viscosity-reducing ether macromonomer is 600 or 1200, and the viscosity-reducing ether macromonomer is selected from one or more of methyl allyl polyoxyethylene ether, isopentanol polyoxyethylene ether, propenol polyoxyethylene ether, allyl polyethylene glycol, methoxy polyethylene glycol ether, and vinyloxy polyethylene glycol ether.

3. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The benzene ring functional monomer is selected from one or more of ferulic acid, styrene, 1-allyl-4-fluorobenzene, 1-phenylvinylboronic acid, and 4-methoxy-2-vinylaniline.

4. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The functional monomer is selected from one or more of methyl acrylate, methyl methacrylate, propyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, 2-hydroxyethyl methacrylate phosphate, and ammonium acrylate.

5. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The unsaturated acid is selected from one or more of acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and fumaric acid.

6. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The reducing agent is selected from one or more of sodium sulfite, sodium bisulfite, ascorbic acid, ferrous sulfate, sodium hypophosphite, bleaching agent, and E51.

7. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The chain transfer agent is selected from one or more of thioglycolic acid, mercaptopropionic acid, sodium hypophosphite, mercaptoethanol, and dodecyl mercaptan.

8. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The oxidant is selected from one or more of potassium persulfate, sodium bisulfite, ammonium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide.

9. The viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The thickener is selected from one or more of acrylic acid monomers, pentaerythritol cross-linked copolymers, carboxymethyl cellulose, and water-soluble sodium polyacrylate with a molecular weight of 2000-50000.

10. The method for preparing the viscosity-reducing polycarboxylate water-reducing agent according to any one of claims 1 to 9, characterized in that: The specific steps include: (1) Synthesis of macromolecular polymers: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (1.1) Add the following raw materials to a four-necked flask: ether macromonomer, deionized water and 10-25% of unsaturated acid; (1.2) Prepare the components of material A: add the remaining unsaturated acid, benzene ring work unit, and deionized water, and stir thoroughly; (1.3) Prepare the components of material B: add reducing agent, chain transfer agent, deionized water, and stir thoroughly; (1.4) Place the four-necked flask in a water bath, turn on the stirring to make the materials evenly stirred, and set the ambient temperature to 20-40℃; After stirring evenly, add the oxidant to the four-necked flask while stirring, and continue stirring for 5-10 minutes; Start dripping material A and material B at the same time while stirring. Material A should be dripped for 80-120 minutes; material B should be dripped for 90-140 minutes. Keep the temperature at the end of the dropwise addition for 50-150 minutes; After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a macromolecular polymer with a molecular weight between 75000 and 85000 can be obtained; (2) Synthesis of small molecule polymers: Add the bottom raw materials, prepare the components of material A, and prepare the components of material B in a four-necked flask according to the ratio; (2.1) Add the following raw materials to a four-necked flask: ether macromonomer, viscosity-reducing ether macromonomer, deionized water and 10-25% of unsaturated acid; (2.2) Prepare the components of material A: add the remaining unsaturated acid, functional monomer, and deionized water, and stir thoroughly; (2.3) Prepare the components of material B: add reducing agent, chain transfer agent, deionized water, and stir thoroughly; (2.4) Place the four-necked flask in a water bath, turn on the stirring to mix the materials evenly, and set the ambient temperature to 20-40℃; After stirring evenly, add the oxidant or reductant to the four-necked flask while stirring, and continue stirring for 5-10 minutes; Start dripping material A and material B at the same time while stirring. Material A should be dripped for 80-120 minutes; material B should be dripped for 90-140 minutes. Keep the temperature at the end of the dropwise addition for 50-150 minutes; After the heat preservation is completed, deionized water is added to dilute and stirred until uniform, and a small molecular polymer with a molecular weight between 14000-16000 can be obtained; (3) Preparation of pre-wrapped small molecule polymers: Dissolve the thickener in deionized water, add it to the small molecule polymer after dissolution, and stir and mix thoroughly to obtain; (4) Premixing the macromolecular polymer and the pre-wrapped small molecular polymer according to a certain proportion, and stirring until they are completely mixed.

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