Polycarboxylic acid water reducing agent, its preparation method and application

Abstract

The application belongs to the field of building materials, and provides a polycarboxylic acid water reducing agent, a preparation method and application thereof. The preparation method of the polycarboxylic acid water reducing agent comprises: in the presence of a viscosity regulator, an initiator, a molecular weight regulator and water, performing a polymerization reaction on comonomers including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to form a polycarboxylic acid; wherein the unsaturated esterification product is a reaction product of an unsaturated monomer II and a hydroxyl polycarboxylic acid; the unsaturated monomer I is at least one of an unsaturated carboxylic acid, an unsaturated carboxylic acid salt and an unsaturated carboxylic anhydride, the unsaturated monomer II is an unsaturated carboxylic acid and / or an unsaturated carboxylic anhydride, and the viscosity regulator is a trivalent cation salt. The preparation method can prepare a polycarboxylic acid water reducing agent with high solid content and low viscosity.

Description

Technical Field

[0001] This invention belongs to the field of building materials, specifically providing a polycarboxylate superplasticizer, its preparation method, and its application. Background Technology

[0002] Concrete is a widely used building material on the market, and water-reducing agents, as the fifth component of concrete, play a crucial role in its performance. Polycarboxylate superplasticizer (PCE) is the third generation of high-performance water-reducing agents, developed after ordinary water-reducing agents represented by lignosulfonate and high-efficiency water-reducing agents represented by naphthalene. With its excellent performance, it has rapidly replaced the first two generations of water-reducing agents and become the preferred admixture for preparing high-performance concrete.

[0003] Currently, polycarboxylate superplasticizers are mainly water-based, with a small amount of powdered or solid polycarboxylate superplasticizers also available on the market. The latter are primarily used in the dry-mix mortar industry. The preparation process of powdered and solid polycarboxylate superplasticizers is energy-intensive, and their performance is inferior to that of water-based polycarboxylate superplasticizers. Furthermore, their solubility in concrete is insufficient. These issues make it difficult to use powdered and solid polycarboxylate superplasticizers in the concrete industry.

[0004] Increasing the solids content of water-based polycarboxylate superplasticizers can save transportation costs and reduce energy consumption and emissions. Furthermore, increasing the solids content of water-based polycarboxylate superplasticizers is currently an effective way to achieve low-carbon and environmentally friendly practices in the superplasticizer industry. However, high-solids-content polycarboxylate superplasticizers currently suffer from problems during synthesis, such as high viscosity, poor mass and heat transfer, difficulty in pumping materials, and suboptimal product performance. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide a polycarboxylate superplasticizer, its preparation method, and its application. The preparation method can reduce the viscosity of the polycarboxylate superplasticizer, obtaining a polycarboxylate superplasticizer with high solids content.

[0006] In a first aspect, the present invention provides a method for preparing a polycarboxylate superplasticizer, the method comprising: in the presence of a viscosity modifier, an initiator, a molecular weight modifier, and water, performing a polymerization reaction on a comonomer including an unsaturated macromonomer, unsaturated monomer I, and an unsaturated esterification product to generate a polycarboxylate, thereby obtaining a polycarboxylate superplasticizer; wherein the unsaturated esterification product is a reaction product of unsaturated monomer II and a hydroxy polycarboxylic acid; the unsaturated monomer I is at least one selected from unsaturated carboxylic acid, unsaturated carboxylate salt, and unsaturated carboxylic anhydride; the unsaturated monomer II is unsaturated carboxylic acid and / or unsaturated carboxylic anhydride; and the viscosity modifier is a trivalent cationic salt.

[0007] In the preparation method of the present invention, unsaturated esterification products are used to carry out polymerization reactions with unsaturated monomer I and unsaturated macromonomers, which can introduce polycarboxylic acid unit structures into the polycarboxylic acid molecular chain. Furthermore, trivalent cationic salts are used as viscosity modifiers to introduce trivalent cations into the polycarboxylic acid molecular chain. By combining the carboxylate ions on the polycarboxylic acid molecules with the trivalent cations, the conformation of the polycarboxylic acid molecules in water is contracted, thereby reducing the viscosity of the polycarboxylic acid water-reducing agent.

[0008] In some embodiments of the present invention, the hydroxy polycarboxylic acid is at least one of hydroxy dicarboxylic acid and hydroxy tricarboxylic acid.

[0009] Furthermore, the structure of the hydroxypolycarboxylic acid is shown in Formula 1:

[0010]

[0011] In this context, L1, L2, and L3 are each independently a single bond or an alkylene group with 1 to 6 carbon atoms, and R1 is a hydrogen or carboxyl group.

[0012] Furthermore, the hydroxypolycarboxylic acid is citric acid and / or malic acid.

[0013] In some embodiments of the present invention, the unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid and itaconic acid; the unsaturated carboxylate is selected from at least one of sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, sodium itaconic acid and potassium itaconic acid; and the unsaturated carboxylic anhydride is selected from maleic anhydride and / or itaconic anhydride.

[0014] In some embodiments of the present invention, the unsaturated esterified product is prepared by a method comprising the steps of esterifying the unsaturated monomer II and the hydroxy polycarboxylic acid in the presence of a catalyst and optionally a polymerization inhibitor.

[0015] Furthermore, the molar ratio of the unsaturated monomer II to the hydroxy polycarboxylic acid is (1-10):1.

[0016] Furthermore, the catalyst is selected from at least one of benzenesulfonic acid, p-benzenesulfonic acid, ethylsulfonic acid, and concentrated sulfuric acid.

[0017] Furthermore, the mass amount of the catalyst is 0.5% to 3% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid.

[0018] Furthermore, the polymerization inhibitor is selected from at least one of hydroquinone and phenothiazine.

[0019] Furthermore, the amount of the polymerization inhibitor is 0 to 1% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid.

[0020] In some embodiments of the present invention, the esterification reaction is carried out at a temperature of 80–130°C and for a reaction time of 1–6 h.

[0021] In some embodiments of the present invention, the unsaturated macromonomer is selected from at least one of 3-methylbut-3-enyl polyethylene glycol ether, 2-methylprop-2-enyl polyethylene glycol ether, ethylene glycol monovinyl polyethylene glycol ether, and vinyl hydroxybutyl polyoxyethylene ether.

[0022] In some embodiments of the present invention, the mass ratio of the unsaturated macromonomer, unsaturated monomer I and unsaturated esterification product is 200:(5-40):(1-15).

[0023] In some embodiments of the present invention, the polymerization reaction is carried out at a temperature of 5–90°C and for a reaction time of 1–5 h.

[0024] In some embodiments of the present invention, the viscosity modifier is at least one of ferric citrate, ferric sulfate, and potassium aluminum sulfate.

[0025] In some embodiments of the present invention, the viscosity modifier is used in an amount of 0.1% to 3% of the total mass of the comonomer. This effectively reduces the viscosity of the polycarboxylate superplasticizer while promoting its adsorption onto cement particles, thus maintaining the superplasticizer's high water-reducing performance.

[0026] Furthermore, the viscosity modifier is used in an amount of 0.5% to 1.5% of the total mass of the comonomer.

[0027] In some embodiments of the present invention, the initiator is at least one of a redox initiator, a persulfate initiator, and a peroxide initiator.

[0028] Furthermore, the initiator is a redox initiator.

[0029] Furthermore, the oxidant in the redox initiator is selected from at least one of benzoyl peroxide, hydrogen peroxide, tert-butyl hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent in the redox initiator is selected from at least one of ferrous sulfate, sodium formaldehyde sulfoxylate, BRUGGOLITE E51, and ascorbic acid.

[0030] Furthermore, the mass ratio of the oxidant to the initiator is 1:(0.2-2).

[0031] In some embodiments of the present invention, the initiator is used in an amount of 0.1% to 2% of the total mass of the comonomer.

[0032] In some embodiments of the present invention, the molecular weight regulator is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid, and sodium hypophosphite.

[0033] In some embodiments of the present invention, the mass amount of the molecular weight regulator is 0.2% to 3% of the total mass of the comonomer.

[0034] In some embodiments of the present invention, the preparation method includes the following steps:

[0035] 1) Mix the unsaturated macromonomer, unsaturated esterification product, viscosity modifier, part of the initiator, and water evenly, and then add dropwise an aqueous solution of unsaturated monomer I, an aqueous solution of the remaining initiator, and an aqueous solution of the molecular weight modifier; or

[0036] The unsaturated macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of the initiator, and water are mixed evenly, and then an aqueous solution of unsaturated monomer I and an aqueous solution of the remaining initiator are added dropwise; wherein,

[0037] The dropping time is controlled to be 0.5 to 3 hours, and the temperature of the reaction system is controlled to be 10 to 60°C during the dropping process;

[0038] 2) After the addition is complete, keep the temperature at 10-60℃ to continue the reaction for 0.5-1h.

[0039] In some embodiments of the present invention, the amount of water used in the preparation method is such that the solid content of the prepared polycarboxylate superplasticizer is not less than 55%.

[0040] Furthermore, the amount of water used ensures that the solid content of the prepared polycarboxylate superplasticizer is not less than 60%.

[0041] Secondly, the present invention provides a polycarboxylate superplasticizer prepared by the preparation method described in the first aspect of the present invention. The polycarboxylate superplasticizer of the present invention maintains a low viscosity even at high solids content.

[0042] In some embodiments of the present invention, the polycarboxylate superplasticizer has a solid content ≥60% and a viscosity ≤550 cP at 20°C.

[0043] Thirdly, the present invention provides the application of the polycarboxylate superplasticizer in building materials.

[0044] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0045] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0046] The "scope" disclosed in this invention is defined in the form of a lower limit and / or an upper limit, whereby a given scope is defined by selecting a lower limit and / or an upper limit. This scope may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined scope, and any lower limit can be combined with other lower limits to form an undefined scope, similarly, any upper limit can be combined with any other upper limit to form an undefined scope. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and can be combined with any other point or single value, or with other lower or upper limits, to form an undefined scope.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0048] The first aspect of the present invention provides a method for preparing a polycarboxylate superplasticizer, comprising: in the presence of a viscosity modifier, an initiator, a molecular weight modifier and water, performing a polymerization reaction on a comonomer including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to synthesize a polycarboxylate, thereby obtaining a polycarboxylate superplasticizer.

[0049] In this invention, the unsaturated monomer I is at least one of unsaturated carboxylic acid, unsaturated carboxylate salt, and unsaturated carboxylic anhydride.

[0050] In this invention, the unsaturated esterification product is the reaction product of unsaturated monomer II and hydroxy polycarboxylic acid, wherein the unsaturated monomer II is one or more of unsaturated carboxylic acid and unsaturated carboxylic anhydride.

[0051] In this invention, the unsaturated carboxylic acid can be a carboxylic acid having 3 to 8 carbon atoms with a double bond. Preferably, the unsaturated carboxylic acid is at least one selected from acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA).

[0052] In this invention, the unsaturated carboxylic acid can be a carboxylic anhydride having 3 to 10 carbon atoms with double bonds. Preferably, the unsaturated carboxylic anhydride is maleic anhydride (MA) and / or itaconic anhydride (ITA).

[0053] In this invention, the unsaturated carboxylate can be a metal salt of an unsaturated carboxylic acid. Preferably, the unsaturated carboxylate is selected from at least one of sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, sodium itaconic acid, and potassium itaconic acid.

[0054] In a preferred embodiment, the unsaturated monomer I is selected from one or more of acrylic acid, methacrylic acid, maleic anhydride, sodium acrylate, and sodium methacrylate.

[0055] In a preferred embodiment, the unsaturated monomer II is selected from one or more of acrylic acid, methacrylic acid, and maleic anhydride.

[0056] In this invention, the unsaturated esterification product can be an esterification product having a double bond and multiple carboxyl groups, wherein the double bond can be provided by unsaturated monomer II, and the multiple carboxyl groups can be provided by hydroxy polycarboxylic acid. For example, in the esterification reaction, the carboxyl group in unsaturated monomer II and the hydroxyl group in hydroxy polycarboxylic acid remove water molecules to form the unsaturated esterification product.

[0057] In some embodiments, the hydroxy polycarboxylic acid may be at least one of hydroxy dicarboxylic acid and hydroxy tricarboxylic acid.

[0058] Preferably, the structure of the hydroxypolycarboxylic acid is shown in Formula 1:

[0059]

[0060] In this context, L1, L2, and L3 are each independently a single bond or an alkylene group with 1 to 6 carbon atoms (e.g., methylene, ethylene, etc.), and R1 is a hydrogen or carboxyl group.

[0061] As some examples, L1 is a single bond, L2 is a single bond, methylene or ethylene, and L3 is methylene or ethylene.

[0062] Understandably, a single bond indicates a direct connection between the two groups it relates to. For example, when L2 is a single bond, the structure of Formula 1 is...

[0063] More preferably, the hydroxypolycarboxylic acid is citric acid and / or malic acid.

[0064] In some embodiments, the unsaturated esterified product is prepared by a method comprising the steps of esterifying the unsaturated monomer II and the hydroxy polycarboxylic acid in the presence of a catalyst and optionally a polymerization inhibitor.

[0065] In this invention, the molar ratio of the unsaturated monomer II to the hydroxy polycarboxylic acid can be (1 to 10):1, for example, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 9:1, 10:1, etc.

[0066] In this invention, the catalyst can be an acid catalyst. Preferably, the catalyst is selected from at least one of benzenesulfonic acid, p-benzenesulfonic acid, ethylsulfonic acid, and concentrated sulfuric acid.

[0067] In this invention, the amount of catalyst used can be selected according to the total amount of reactants. According to some embodiments, the mass amount of the catalyst is 0.5% to 3% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid, for example 0.8%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.6%, 1.8%, 1.9%, 2.2%, 2.5%, 2.8%, 3%, etc.

[0068] In this invention, a polymerization inhibitor may or may not be added to the esterification reaction, specifically depending on the type of unsaturated monomer II, to reduce the possibility of self-polymerization of unsaturated monomer II under esterification reaction conditions. Preferably, the polymerization inhibitor is selected from at least one of hydroquinone and phenothiazine.

[0069] In some embodiments, the amount of the polymerization inhibitor is 0 to 1% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0070] In some embodiments, the temperature of the esterification reaction is 80–130°C, for example 80°C, 90°C, 100°C, 105°C, 110°C, 120°C, 125°C, 130°C, etc.; the time of the esterification reaction is 1–6 hours, for example 1 hour, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 5 hours, etc.

[0071] In this invention, to improve the yield of the esterification product, it is preferable to perform a dehydration operation during the esterification reaction, for example, by vacuum dehydration or dehydration using an inert gas as a carrier gas. The inert gas is, for example, but not limited to, nitrogen.

[0072] In this invention, the unsaturated macromonomer can be selected from polyether or polyester-based macromonomers containing hydrophilic carboxyl groups and optionally amino, sulfonic acid, or other hydrophilic groups, such as allyl polyethylene glycol, modified polyethers, etc. Preferably, the unsaturated macromonomer is selected from at least one of 3-methylbut-3-enyl polyethylene glycol ether (IPEG), 2-methylprop-2-enyl polyethylene glycol ether (HPEG), ethylene glycol monovinyl polyethylene glycol ether (EPEG), and vinyl hydroxybutyl polyoxyethylene ether (VPEG).

[0073] In this invention, the number-average molecular weight of the unsaturated macromonomer can be 600 to 6000, for example 1000, 1500, 2400, 3000, 3500, 4000, 5000, etc.

[0074] As examples, the unsaturated macromonomer can be polyether macromonomers such as EPEG2400, EPEG3000, VPEG2400, VPEG3000, and IPEG2400.

[0075] The unsaturated monomers of the present invention are commercially available, for example, from the series of polyether products of Jiangsu Aoke Chemical Co., Ltd., such as OXAC-608A and OXAC-609E.

[0076] In this invention, the unsaturated macromonomer, unsaturated monomer I, and unsaturated esterification product, as comonomers, can be synthesized into a copolymer (i.e., polycarboxylic acid) via free radical polymerization. According to some embodiments, the mass ratio of the unsaturated macromonomer, unsaturated monomer I, and unsaturated esterification product is 200:(5–40):(1–15), for example, 200:5:3, 200:5:10, 200:5:10, 200:15:5, 200:14:6, 200:10:10, etc.

[0077] In this invention, the initiator can be selected from various water-soluble free radical initiators. According to some embodiments, the initiator is selected from at least one of redox initiators, persulfate initiators, and peroxide initiators, preferably a redox initiator.

[0078] In this invention, specific examples of the persulfate initiator include, but are not limited to, one or more of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0079] In this invention, specific examples of the peroxide initiator include, but are not limited to, one or more of hydrogen peroxide, tert-butylhydrogen peroxide, and benzoyl oxide.

[0080] In this invention, the redox initiator comprises an oxidant and a reducing agent. Preferably, the oxidant is selected from at least one of benzoyl peroxide, hydrogen peroxide, tert-butyl hydroperoxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is selected from at least one of ferrous sulfate, sodium formaldehyde sulfoxylate, BRUGGOLITE E51, and ascorbic acid.

[0081] As some examples, the redox initiator may be hydrogen peroxide-ascorbic acid, hydrogen peroxide-sodium formaldehyde sulfoxylate, hydrogen peroxide-BRUGGOLITE E51, hydrogen peroxide-ascorbic acid-ferrous sulfate, hydrogen peroxide-sodium formaldehyde sulfoxylate-ferrous sulfate, or hydrogen peroxide-BRUGGOLITE E51-ferrous sulfate.

[0082] Understandably, in descriptions of redox initiators, "AB" indicates a combination of A and B, while "ABC" indicates a combination of A, B, and C. For example, "hydrogen peroxide-ascorbic acid" refers to a combination of hydrogen peroxide and ascorbic acid as the redox initiator, and "hydrogen peroxide-ascorbic acid-ferrous sulfate" refers to a combination of hydrogen peroxide, ascorbic acid, and ferrous sulfate as the redox initiator. Hydrogen peroxide in the initiator is usually used in the form of hydrogen peroxide solution, with a hydrogen peroxide content of, for example, 27.5% by mass.

[0083] In some embodiments, the mass ratio of oxidant to initiator in the redox initiator can be 1:(0.2 to 2), for example 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:2, etc.

[0084] In this invention, the amount of initiator can be selected based on the total amount of comonomers. According to some embodiments, the mass amount of the initiator is 0.1% to 2% of the total mass of the comonomers (i.e., the total amount of the unsaturated macromonomer, unsaturated monomer I, and unsaturated esterification product), for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.1%, 1.5%, 1.7%, 1.8%, etc.

[0085] In this invention, the molecular weight regulator may be selected from chain transfer agents used in free radical polymerization. According to some embodiments, the molecular weight regulator is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid, and sodium hypophosphite.

[0086] In this invention, the amount of the molecular weight regulator can be selected based on the total amount of comonomers. According to some embodiments, the mass amount of the molecular weight regulator is 0.2% to 3% of the total mass of the comonomers, for example, 0.3%, 0.4%, 0.5%, 0.8%, 1.2%, 1.5%, 2.2%, 2.5%, 2.5%, 2.8%, etc.

[0087] In this invention, the viscosity modifier is a trivalent cationic salt. The trivalent cationic salt refers to a salt that provides trivalent cations after dissolving in water; it can be a simple salt or a complex salt. During the preparation of the polycarboxylate superplasticizer, the cations on the trivalent cationic salt can combine with the carboxylate ions on the polycarboxylate molecules, effectively reducing the viscosity of the polycarboxylate superplasticizer. According to some embodiments, the viscosity modifier is at least one of ferric citrate, ferric sulfate, and potassium aluminum sulfate.

[0088] In this invention, the amount of viscosity modifier can be selected based on the amount of comonomer. According to some embodiments, the mass amount of the viscosity modifier is 0.1% to 3% of the total mass of the comonomer, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, etc. Generally, a low amount of viscosity modifier may not be sufficient to form enough bonds with carboxylate ions, resulting in limited viscosity reduction of the water-reducing agent; an excessively high amount may affect the adsorption of the water-reducing agent on cement particles. Preferably, the mass amount of the viscosity modifier is 0.5% to 1.5% of the total mass of the comonomer.

[0089] In this invention, the polymerization reaction temperature can be from 5 to 90°C, for example, 10°C, 15°C, 15°C, 18°C, 30°C, 32°C, 35°C, 40°C, 50°C, 50°C, 55°C, 60°C, 70°C, 80°C, etc. In some embodiments, the polymerization reaction temperature can be controlled within any temperature range mentioned above, for example, controlled between 15 and 30°C, or controlled between 40 and 60°C, etc.

[0090] In this invention, the polymerization reaction time can be determined according to the degree of conversion of the comonomer, and is usually 1 to 5 hours, such as 1 hour, 1.5 hours, 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0091] In this invention, after the polymerization reaction is completed, an alkali may or may not be added to adjust the pH, depending on the monomer type. Preferably, the product's pH is slightly acidic or neutral. As some specific embodiments, the preparation method further includes adding an alkali after the polymerization reaction to adjust the product's pH to 3-7.5. Preferably, the amount of alkali used is 0-1% of the total mass of the comonomer.

[0092] In this invention, the alkali may include, but is not limited to, sodium hydroxide and / or potassium hydroxide. Preferably, the alkali is added in the form of an alkaline solution. As a specific example, the alkaline solution is a 32% (w / w) aqueous solution of sodium hydroxide.

[0093] To improve the polymerization reaction effect, according to some preferred embodiments, the preparation method of the polycarboxylate superplasticizer includes the following steps:

[0094] 1) Mix the unsaturated macromonomer, unsaturated esterification product, viscosity modifier, part of the initiator, and water evenly, and then add dropwise an aqueous solution of unsaturated monomer I, an aqueous solution of the remaining initiator, and an aqueous solution of the molecular weight modifier; or

[0095] The unsaturated macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of the initiator and water are mixed evenly, and an aqueous solution of unsaturated monomer I and the remaining aqueous solution of initiator are added dropwise to the mixture.

[0096] 2) After the addition is complete, keep the temperature at 10–60℃ to continue the reaction for 0.5–1 hour;

[0097] Optionally, it also includes:

[0098] 3) Add an aqueous solution of the alkali to the product obtained in step 1) to adjust the pH to 3 to 7.5.

[0099] In step 1), the molecular weight regulator can be added to the reaction system together with the unsaturated macromonomer during the mixing process, or it can be introduced into the reaction system together with the unsaturated monomer II during the dropwise addition process.

[0100] In step 1), when the initiator is selected from redox initiators, some of the initiators may be one of the components, and the remaining initiators may be some of the other components.

[0101] In step 1), the dropping time is controlled to be 0.5–3 h, and the temperature of the reaction system during the dropping process is 10–60 °C. Under these conditions, the conversion rate of the reactants can be improved, and mass and heat transfer during the reaction process can be facilitated.

[0102] In step 2), the heat preservation after the addition can further improve the conversion degree of the reactants.

[0103] In this invention, the amount of water used can be selected based on the desired solids content of the polycarboxylate superplasticizer and the viscosity of the system. Generally, as the amount of water increases, the viscosity of the polycarboxylate superplasticizer decreases, which is beneficial for pumping and mass and heat transfer, but the solids content also decreases, leading to a decrease in production and transportation efficiency. In particular, the preparation method of this invention can reduce the viscosity of the polycarboxylate superplasticizer, making it particularly suitable for the preparation of polycarboxylate superplasticizers with high solids content. In other words, the preparation method of this invention can increase the solids content of the polycarboxylate superplasticizer while maintaining a low viscosity.

[0104] In some embodiments, the amount of water used is such that the solid content of the polycarboxylate superplasticizer is not less than 55%, preferably not less than 60%.

[0105] The method of this invention can not only solve the problem of reduced performance of water-reducing agents caused by poor mass and heat transfer due to high viscosity during the synthesis process, but also synthesize polycarboxylate water-reducing agents with high solid content, thereby improving the production and transportation efficiency of polycarboxylate water-reducing agents.

[0106] A second aspect of the present invention provides a polycarboxylate superplasticizer prepared by the preparation method described in the first aspect of the present invention. Compared with conventional polycarboxylate superplasticizers, the polycarboxylate superplasticizer of the present invention has a lower viscosity at the same solids content; or, at comparable viscosity, the polycarboxylate superplasticizer of the present invention has a higher solids content.

[0107] In some embodiments, the polycarboxylate superplasticizer has a solids content ≥60% and a viscosity ≤550 cP at 20°C.

[0108] A third aspect of the present invention provides the application of the polycarboxylate superplasticizer described in the second aspect of the present invention in building materials. The polycarboxylate superplasticizer of the present invention has low viscosity and exhibits a high water-reducing effect on building materials, especially concrete.

[0109] The following describes embodiments of the present invention. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0110] In the following examples and comparative examples, the hydrogen peroxide concentration in the hydrogen peroxide solution was 27.5 wt%, and the NaOH concentration in the sodium hydroxide aqueous solution was 32 wt%.

[0111] Example 1

[0112] (1) 192.00g citric acid, 288.00g acrylic acid, 5.90g p-toluenesulfonic acid and 2.00g hydroquinone were added to the reactor and stirred. The temperature was raised to 105℃ and water was removed by purging with nitrogen. The reaction was carried out for 3 hours to obtain unsaturated esterification product A-1.

[0113] (2) Take 12.00g of unsaturated esterification product A-1, 480g of EPEG3000, 5.00g of ferric citrate, 0.016g of ferrous sulfate and 293.00g of water and add them to the reactor. Turn on the stirrer and temperature control device. After the materials are mixed evenly, start to add acrylic acid aqueous solution (36.00g of acrylic acid and 10.00g of water), hydrogen peroxide aqueous solution (4.30g of hydrogen peroxide and 15.00g of water), mercaptopropionic acid aqueous solution (2.40g of mercaptopropionic acid and 15.00g of water), and BRUGGOLITE E51 aqueous solution (0.70g of BRUGGOLITE E51 and 15.00g of water). The initial reaction temperature is 15℃, the adding time is 1.0h, and the material temperature is controlled ≤30℃ during the adding process. After the adding is completed, keep warm for 1h to obtain the copolymer product.

[0114] (3) Add 6g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylate superplasticizer KZJ-1.

[0115] Example 2

[0116] (1) 134.00g malic acid, 43.00g methacrylic acid, 288.00g acrylic acid, 8.80g p-toluenesulfonic acid, 1.00g hydroquinone and 0.50g phenthiazide were added to the reactor and stirred. The temperature was raised to 110℃ and water was removed by vacuum. The reaction was carried out for 4 hours to obtain unsaturated esterification product A-2.

[0117] (2) Take 15.00g of unsaturated esterification product A-2, 380g of EPEG3000, 100.00g of VPEG3000, 4.60g of ferric sulfate, 0.012g of ferrous sulfate and 290.00g of water and add them to the reactor. Turn on the stirrer and temperature control device. After the materials are mixed evenly, start to dropwise add acrylic acid aqueous solution (34.00g of acrylic acid and 10.00g of water), hydrogen peroxide aqueous solution (3.80g of hydrogen peroxide and 15.00g of water), mercaptoacetic acid aqueous solution (2.20g of mercaptoacetic acid and 15.00g of water), and sodium formaldehyde sulfoxylate aqueous solution (1.20g of sodium formaldehyde sulfoxylate and 15g of water). The initial reaction temperature is 13℃, the dropping time is 45min, the material temperature is controlled ≤25℃ during the dropping process, and the temperature is kept warm for 1h after the dropping is completed to obtain the copolymer product.

[0118] (3) Add 12g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylate superplasticizer KZJ-2.

[0119] Example 3

[0120] (1) 32.00g citric acid, 33.00g malic acid, 196.00g maleic anhydride, 86.00g methacrylic acid, 72.00g acrylic acid, 6.80g p-toluenesulfonic acid and 1.20g hydroquinone were added to a reactor and stirred. The temperature was raised to 100℃ and water was removed by vacuum. The reaction was carried out for 3 hours to obtain unsaturated esterification product A-3.

[0121] (2) Add 24.00g of unsaturated esterification product A-3, 400g of EPEG2400, 80.00g of IPEG2400, 4.00g of ferric citrate, 2.00g of potassium aluminum sulfate, 7.50g of sodium hypophosphite, 0.015g of ferrous sulfate and 314.00g of water to the reactor. Turn on the stirrer and temperature control device. After the materials are mixed evenly, start to add acrylic acid aqueous solution (24.00g of acrylic acid and 10.00g of water), hydrogen peroxide aqueous solution (5.70g of hydrogen peroxide and 15.00g of water), and ascorbic acid aqueous solution (1.50g of ascorbic acid and 15.00g of water) dropwise. The initial reaction temperature is 15℃, the dropwise addition time is 1h, the material temperature is controlled ≤30℃ during the dropwise addition process, and the temperature is kept warm for 1h after the dropwise addition is completed to obtain the copolymer product.

[0122] (3) Add 2g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylate superplasticizer KZJ-3.

[0123] Example 4

[0124] 15.00g of unsaturated esterification product A-1 prepared in Example 1, 480g of EPEG3000, 6.00g of ferric sulfate, 0.012g of ferrous sulfate and 297.00g of water were added to the reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, the following solutions were added dropwise: an aqueous solution of acrylic acid, sodium acrylate and maleic anhydride (18.00g acrylic acid, 12.00g sodium acrylate, 6.00g maleic anhydride and 20.00g water), an aqueous solution of hydrogen peroxide (4.00g hydrogen peroxide and 10.00g water), an aqueous solution of mercaptoacetic acid (2.00g mercaptoacetic acid and 10.00g water), and an aqueous solution of sodium formaldehyde sulfoxylate (1.30g sodium formaldehyde sulfoxylate and 15.00g water). The initial reaction temperature was 20℃, the dropwise addition time was 1h, the material temperature was controlled to be ≤25℃ during the dropwise addition process, and the temperature was kept warm for 1.5h after the dropwise addition was completed to obtain the copolymer product.

[0125] (3) Add 4g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylate superplasticizer KZJ-4.

[0126] Example 5

[0127] (1) 192.00g citric acid, 144.00g acrylic acid, 2.90g p-toluenesulfonic acid and 1.30g hydroquinone were added to the reactor and stirred. The temperature was raised to 105℃ and water was removed by purging with nitrogen. The reaction was carried out for 3 hours to obtain the unsaturated esterification product A-4.

[0128] (2) Take 12.00g of unsaturated esterification product A-4, 480g of EPEG3000, 5.00g of potassium aluminum sulfate, 0.016g of ferrous sulfate and 296.00g of water and add them to the reactor. Turn on the stirrer and temperature control device. After the materials are mixed evenly, start to add acrylic acid, sodium methacrylate aqueous solution (33.00g of acrylic acid, 5.00g of sodium methacrylate and 20.00g of water), hydrogen peroxide (4.1g of hydrogen peroxide and 10.00g of water), mercaptopropionic acid aqueous solution (2.20g of mercaptopropionic acid and 10.00g of water), and BRUGGOLITE E51 aqueous solution (0.70g of BRUGGOLITE E51 and 15.00g of water). The initial reaction temperature is 15℃, the dropping time is 1.0h, the material temperature is controlled ≤40℃ during the dropping process, and the temperature is kept warm for 1h after the dropping is completed to obtain the copolymer product.

[0129] (3) Add 5g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylate superplasticizer KZJ-5.

[0130] Comparative Example 1

[0131] (1) Add 480.00g EPEG3000, 5.00g ferric citrate, 0.016g ferrous sulfate and 293.00g water to the reactor, turn on the stirrer and temperature control device, and wait for the materials to mix evenly. Then start to dropwise add acrylic acid aqueous solution (36.00g acrylic acid, 10.00g water), hydrogen peroxide aqueous solution (4.30g hydrogen peroxide, 15.00g water), mercaptopropionic acid aqueous solution (2.40g mercaptopropionic acid, 15.00g water), and BRUGGOLITE E51 aqueous solution (0.70g BRUGGOLITE E51, 15.00g water). The initial reaction temperature is 15℃, the dropping time is 1.0h, the material temperature is controlled ≤30℃ during the dropping process, and the temperature is kept warm for 1h after the dropping is completed to obtain the copolymer product.

[0132] (2) Add 6g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain polyacid water-reducing agent, which is designated as control sample PCE-1.

[0133] Comparative Example 2

[0134] (1) 192.00g citric acid, 288.00g acrylic acid, 5.90g p-toluenesulfonic acid and 2.00g hydroquinone were added to the reactor and stirred. The temperature was raised to 105℃ and water was removed by purging with nitrogen. The reaction was carried out for 3 hours to obtain esterified product A-1.

[0135] (2) Add 12.00g of the esterified product A-1 obtained in step (1), 480.00g of EPEG3000, 0.016g of ferrous sulfate and 293.00g of water to the reactor, turn on the stirrer and temperature control device, and wait for the materials to be mixed evenly. Then start to add acrylic acid aqueous solution (36.00g of acrylic acid and 10.00g of water), hydrogen peroxide aqueous solution (4.30g of hydrogen peroxide and 15.00g of water), mercaptopropionic acid aqueous solution (2.40g of mercaptopropionic acid and 15.00g of water), and BRUGGOLITE E51 aqueous solution (0.70g of BRUGGOLITE E51 and 15.00g of water). The initial reaction temperature is 15℃, the adding time is 1.0h, the material temperature is controlled to be ≤30℃ during the adding process, and the temperature is kept warm for 1h after the adding is completed to obtain the copolymer product.

[0136] (3) Add 6g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polyacid water-reducing agent, which is used as a control sample PCE-2.

[0137] Comparative Example 3

[0138] (1) Add 480.00g EPEG3000, 0.016g ferrous sulfate and 293.00g water to the reactor, turn on the stirrer and temperature control device, and wait for the materials to mix evenly. Then start to add acrylic acid aqueous solution (36.00g acrylic acid, 10.00g water), hydrogen peroxide aqueous solution (4.30g hydrogen peroxide, 15.00g water), mercaptopropionic acid aqueous solution (2.40g mercaptopropionic acid, 15.00g water) and BRUGGOLITE E51 aqueous solution (0.70g BRUGGOLITE E51, 15.00g water). The initial reaction temperature is 15℃, the dropping time is 1.0h, the material temperature is controlled ≤30℃ during the dropping process, and the temperature is kept warm for 1h after the dropping is completed to obtain the copolymer product.

[0139] (2) Add 6g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain polyacid water-reducing agent, which is used as a control sample PCE-3.

[0140] Comparative Example 4

[0141] (1) Add 480.00g EPEG3000, 0.016g ferrous sulfate and 455.00g water to the reactor, turn on the stirrer and temperature control device, and wait for the materials to mix evenly. Then start to dropwise add acrylic acid aqueous solution (36.00g acrylic acid and 10.00g water), hydrogen peroxide aqueous solution (4.30g hydrogen peroxide and 15.00g water), mercaptopropionic acid aqueous solution (2.40g mercaptopropionic acid and 15.00g water), and BRUGGOLITE E51 aqueous solution (0.70g BRUGGOLITE E51 and 15.00g water). The initial reaction temperature is 15℃, the dropping time is 1.0h, the material temperature is controlled ≤30℃ during the dropping process, and the temperature is kept warm for 1h after the dropping is completed to obtain the copolymer product.

[0142] (2) Add 6g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain polyacid water-reducing agent, which is used as a control sample PCE-4.

[0143] Test case

[0144] The following test examples illustrate the performance of polycarboxylate superplasticizers KZJ-1 to KZJ-5 prepared in Test Examples 1 to 5 and comparative samples PCE-1 to PCE-4 prepared in Comparative Examples 1 to 4.

[0145] 1. Viscosity test: The viscosity of each polycarboxylate superplasticizer was tested at 20℃ using a rotational viscometer NDJ-8T (using rotor No. 2, rotation speed 30 rpm).

[0146] 2. Water reduction rate test: The concrete performance of each polycarboxylate superplasticizer was tested according to GB / T8076-2008.

[0147] The test results are shown in Table 1.

[0148] Table 1

[0149]

[0150]

[0151] Table 1 shows that the results of KZJ-1 and PCE-1 are compared. PCE-1 (Comparative Example 1), which does not contain unsaturated esterification product A-1, has a smaller water reduction rate and a larger viscosity than KZJ-1 prepared in Example 1. This is mainly because the absence of unsaturated esterification product A-1 reduces the number of carboxylic acid structures in the copolymer molecular structure, resulting in a lower water reduction rate. At the same time, fewer carboxylic acid structures can form bonds with the viscosity modifier, thus resulting in a higher viscosity.

[0152] The comparison results between KZJ-1 and PCE-2 show that PCE-2 (Comparative Example 2), without the addition of viscosity modifier, has a slightly lower water reduction rate and a significantly higher viscosity than KZJ-1. This indicates that under the same monomer composition, the viscosity is higher without the addition of viscosity modifier. Furthermore, the high viscosity during the synthesis process will affect the mass and heat transfer effect, resulting in poor water reduction performance of the synthesized product.

[0153] The comparison results between KZJ-1 and PCE-3 show that PCE-3, which does not contain unsaturated esterification product A-1 and viscosity modifier, has a significantly lower water reduction rate and a significantly higher viscosity than KZJ-1. This is mainly because the absence of esterification product A-1 reduces the number of carboxylic acid structures in the product's molecular structure, resulting in a lower water reduction rate. At the same time, the lack of viscosity modifier leads to a higher viscosity during synthesis, which affects mass and heat transfer, resulting in poorer performance of the final product.

[0154] The comparison results between PCE-3 and PCE-4 show that, under the material ratio of PCE-3, when the synthesis concentration is reduced from about 60% to 50.0%, the water reduction rate of the final product is improved and the viscosity is significantly reduced.

[0155] In summary, the preparation method of the present invention can effectively reduce the viscosity of the product and increase the water reduction rate while increasing the solid content of the polycarboxylate superplasticizer.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a polycarboxylate superplasticizer, characterized in that, include: In the presence of viscosity modifiers, initiators, molecular weight regulators, and water, comonomers, including unsaturated macromonomers, unsaturated monomer I, and unsaturated esterification products, undergo a polymerization reaction to obtain a polycarboxylate superplasticizer; wherein... The unsaturated esterification product is the reaction product of unsaturated monomer II and hydroxy polycarboxylic acid; The unsaturated monomer I is at least one of unsaturated carboxylic acid, unsaturated carboxylate, and unsaturated carboxylic anhydride; The unsaturated monomer II is an unsaturated carboxylic acid and / or an unsaturated carboxylic anhydride; The viscosity modifier is a trivalent cationic salt.

2. The preparation method according to claim 1, characterized in that, The hydroxy polycarboxylic acid is at least one of hydroxy dicarboxylic acid and hydroxy tricarboxylic acid.

3. The preparation method according to claim 1, characterized in that, The structure of the hydroxy polycarboxylic acid is shown in Formula 1: Formula 1 In this context, L1, L2, and L3 are each independently a single bond or an alkylene group with 1 to 6 carbon atoms, and R1 is a hydrogen or carboxyl group.

4. The preparation method according to claim 1, characterized in that, The hydroxy polycarboxylic acid is citric acid and / or malic acid.

5. The preparation method according to any one of claims 1-4, characterized in that, The unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, and itaconic acid; the unsaturated carboxylate is selected from at least one of sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, sodium itaconic acid, and potassium itaconic acid; the unsaturated carboxylic anhydride is selected from maleic anhydride and / or itaconic anhydride.

6. The preparation method according to any one of claims 1-4, characterized in that, The unsaturated esterified product is prepared by a method comprising the following steps: The unsaturated monomer II and the hydroxy polycarboxylic acid are subjected to esterification in the presence of a catalyst and optionally a polymerization inhibitor.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the unsaturated monomer II to the hydroxy polycarboxylic acid is (1~10):

1.

8. The preparation method according to claim 6, characterized in that, The catalyst is selected from at least one of benzenesulfonic acid, p-benzenesulfonic acid, ethylsulfonic acid, and concentrated sulfuric acid.

9. The preparation method according to claim 6, characterized in that, The mass amount of the catalyst is 0.5% to 3% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid.

10. The preparation method according to claim 6, characterized in that, The polymerization inhibitor is selected from at least one of hydroquinone and phenothiazine.

11. The preparation method according to claim 6, characterized in that, The amount of the polymerization inhibitor is 0 to 1% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid.

12. The preparation method according to claim 6, characterized in that, The esterification reaction is carried out at a temperature of 80~130℃ for 1~6 hours.

13. The preparation method according to any one of claims 1-4, characterized in that, The unsaturated macromonomer is selected from at least one of 3-methylbut-3-enyl polyethylene glycol ether, 2-methylprop-2-enyl polyethylene glycol ether, ethylene glycol monovinyl polyethylene glycol ether, and vinyl hydroxybutyl polyoxyethylene ether.

14. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of the unsaturated macromonomer, unsaturated monomer I, and unsaturated esterification product is 200:(5~40):(1~15).

15. The preparation method according to any one of claims 1-4, characterized in that, The polymerization reaction is carried out at a temperature of 5~90℃ for 1~5 hours.

16. The preparation method according to any one of claims 1-4, characterized in that, The viscosity modifier is at least one of ferric citrate, ferric sulfate, and potassium aluminum sulfate.

17. The preparation method according to any one of claims 1-4, characterized in that, The viscosity modifier is used at a mass ratio of 0.1% to 3% of the total mass of the comonomer.

18. The preparation method according to claim 17, characterized in that, The viscosity modifier is used at a mass ratio of 0.5% to 1.5% of the total mass of the comonomer.

19. The preparation method according to any one of claims 1-4, characterized in that, The initiator is at least one of redox initiators, persulfate initiators, and peroxide initiators.

20. The preparation method according to claim 19, characterized in that, The initiator is a redox initiator.

21. The preparation method according to claim 19, characterized in that, The oxidant in the redox initiator is selected from at least one of benzoyl peroxide, hydrogen peroxide, tert-butyl hydroperoxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent in the redox initiator is selected from at least one of ferrous sulfate, sodium formaldehyde sulfoxylate, BRUGGOLITE E51, and ascorbic acid.

22. The preparation method according to any one of claims 1-4, characterized in that, The initiator is used at a mass ratio of 0.1% to 2% of the total mass of the comonomer.

23. The preparation method according to any one of claims 1-4, characterized in that, The molecular weight regulator is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid, and sodium hypophosphite.

24. The preparation method according to any one of claims 1-4, characterized in that, The mass amount of the molecular weight regulator is 0.2% to 3% of the total mass of the comonomer.

25. The preparation method according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: 1) Mix the unsaturated macromonomer, unsaturated esterification product, viscosity modifier, part of the initiator, and water evenly, and then add dropwise an aqueous solution of unsaturated monomer I, an aqueous solution of the remaining initiator, and an aqueous solution of the molecular weight modifier; or The unsaturated macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of the initiator, and water are mixed evenly, and then an aqueous solution of unsaturated monomer I and an aqueous solution of the remaining initiator are added dropwise; wherein, The dropping time is controlled to be 0.5~3h, and the temperature of the reaction system during the dropping process is 10~60℃; 2) After the addition is complete, keep the temperature at 10~60℃ to continue the reaction for 0.5~1h.

26. The preparation method according to any one of claims 1-4, characterized in that, The amount of water used ensures that the solid content of the prepared polycarboxylate superplasticizer is not less than 55%.

27. The preparation method according to claim 26, characterized in that, The amount of water used ensures that the solid content of the prepared polycarboxylate superplasticizer is not less than 60%.

28. A polycarboxylate superplasticizer prepared by the preparation method according to any one of claims 1-27.

29. The polycarboxylate superplasticizer according to claim 28, characterized in that, The polycarboxylate superplasticizer has a solids content of ≥60% and a viscosity of ≤550 cP at 20℃.

30. The application of the polycarboxylate superplasticizer according to claim 28 or 29 in building materials.

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