Polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention belongs to the field of building materials, and provides a polycarboxylate superplasticizer as well as a preparation method and application thereof. The preparation method of the polycarboxylic acid water reducer comprises the following steps: in the presence of a viscosity regulator, an initiator, a molecular weight regulator and water, carrying out polymerization reaction on comonomers including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to form polycarboxylic acid; wherein the unsaturated esterification product is a reaction product of an unsaturated monomer II and hydroxyl polycarboxylic acid; the unsaturated monomer I is at least one of unsaturated carboxylic acid, unsaturated carboxylate and unsaturated carboxylic acid anhydride, the unsaturated monomer II is unsaturated carboxylic acid and / or unsaturated carboxylic acid anhydride, and the viscosity modifier is trivalent cation salt. The preparation method provided by the invention can be used for preparing the polycarboxylic acid water reducer with high solid content and low viscosity.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and specifically provides a polycarboxylate water reducer and a preparation method and application thereof. Background Art

[0002] Concrete is a widely used building material on the market. As the fifth component of concrete, water reducer plays a vital role in the performance of concrete. Polycarboxylate water reducer (PCE) is the third generation of high-performance water reducer developed after ordinary water reducers represented by wood calcium and high-efficiency water reducers represented by naphthalene. With its excellent performance, it quickly replaced the first two generations of water reducers and became the preferred admixture for preparing high-performance concrete.

[0003] At present, polycarboxylate water-reducing agents are mainly water-based agents, and there are also a small amount of powdered polycarboxylate water-reducing agents or solid polycarboxylate water-reducing agents on the market, the latter of which is mainly used in the dry mortar industry. The preparation process of powdered polycarboxylate water-reducing agents and solid polycarboxylate water-reducing agents has high energy consumption, and the product performance is also inferior to that of water-based polycarboxylate water-reducing agents. When used in concrete, the solubility is also insufficient. These problems make it difficult to use powdered and solid polycarboxylate water-reducing agents in the concrete industry.

[0004] Increasing the solid content of water-based polycarboxylate water-reducing agent products can save transportation costs and save energy and reduce emissions. In addition, increasing the solid content of water-based polycarboxylate water-reducing agent is also an effective way to achieve low-carbon and environmental protection in the water-reducing agent industry. However, the current high-solid content polycarboxylate water-reducing agent has problems such as high viscosity, which is not conducive to mass transfer and heat transfer, and the material is difficult to pump, and the product performance is poor. Summary of the invention

[0005] In view of the above problems existing in the prior art, the object of the present invention is to provide a polycarboxylate water-reducing agent and a preparation method and application thereof. The preparation method can reduce the viscosity of the polycarboxylate water-reducing agent and obtain a polycarboxylate water-reducing agent with a high solid content.

[0006] In a first aspect, the present invention provides a method for preparing a polycarboxylic acid water-reducing agent, the method comprising: in the presence of a viscosity modifier, an initiator, a molecular weight modifier and water, polymerizing comonomers including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to generate a polycarboxylic acid, thereby obtaining a polycarboxylic acid water-reducing agent; wherein the unsaturated esterification product is a reaction product of an unsaturated monomer II and a hydroxy polycarboxylic acid; the unsaturated monomer I is at least one of an unsaturated carboxylic acid, an unsaturated carboxylate and an unsaturated carboxylic acid anhydride; the unsaturated monomer II is an unsaturated carboxylic acid and / or an unsaturated carboxylic acid anhydride; and the viscosity modifier is a trivalent cation salt.

[0007] In the preparation method of the present invention, the unsaturated esterification product is used to carry out polymerization reaction with the unsaturated monomer I and the unsaturated macromonomer, so that a polycarboxylic acid unit structure can be introduced into the polycarboxylic acid molecular chain. Furthermore, a trivalent cation salt is used as a viscosity modifier, so that a trivalent cation can be introduced into the polycarboxylic acid molecular chain. The carboxylate ions on the polycarboxylic acid molecules are combined with the trivalent cations, so that 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 a hydroxy dibasic acid and a hydroxy tribasic acid.

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

[0010]

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

[0012] Furthermore, the hydroxy polycarboxylic 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 carboxylic acid salt is selected from at least one of sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, sodium itaconate and potassium itaconate; the unsaturated carboxylic acid anhydride is selected from maleic anhydride and / or itaconic anhydride.

[0014] In some embodiments of the present invention, the unsaturated esterification product is obtained by a method comprising the following steps: subjecting the unsaturated monomer II and the hydroxy polycarboxylic acid to an esterification reaction in the presence of a catalyst and an optional 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-toluenesulfonic 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 temperature of the esterification reaction is 80 to 130° C., and the reaction time is 1 to 6 hours.

[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, the unsaturated monomer I and the unsaturated esterification product is 200:(5-40):(1-15).

[0023] In some embodiments of the present invention, the polymerization reaction temperature is 5 to 90° C., and the reaction time is 1 to 5 hours.

[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 mass amount of the viscosity modifier is 0.1% to 3% of the total mass of the comonomer, so that the viscosity of the polycarboxylate water reducer can be effectively reduced while promoting the adsorption of the polycarboxylate water reducer on cement particles, so that the water reducer maintains a high water reducing performance.

[0026] Furthermore, the mass amount of the viscosity modifier is 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 oxide, 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, bleaching powder, 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 mass amount of the initiator is 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 thioglycolic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid and sodium hypophosphite.

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

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

[0035] 1) uniformly mixing the unsaturated macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water, and dropwise adding thereto an aqueous solution of the 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 initiator and water are uniformly mixed, and the aqueous solution of unsaturated monomer I and the aqueous solution of the remaining initiator are added dropwise thereto; wherein,

[0037] The time of the dropwise addition 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 dropwise addition process;

[0038] 2) After the addition is completed, keep the mixture at 10-60°C to continue the reaction for 0.5-1h.

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

[0040] Furthermore, the amount of water used is such that the solid content of the prepared polycarboxylate water-reducing agent is not less than 60%.

[0041] In a second aspect, the present invention provides a polycarboxylate water-reducing agent prepared by the preparation method described in the first aspect of the present invention. The polycarboxylate water-reducing agent of the present invention has a relatively low viscosity under the condition of high solid content.

[0042] In some embodiments of the present invention, the solid content of the polycarboxylate water-reducing agent is ≥ 60%, and the viscosity at 20° C. is ≤ 550 cP.

[0043] In a third aspect, the present invention provides use of the polycarboxylate water-reducing agent in building materials.

[0044] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[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 "range" disclosed in the present invention is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way can be inclusive or exclusive of the end value, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an undefined range, and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an undefined range.

[0047] If not 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 polycarboxylic acid water-reducing agent, comprising: in the presence of a viscosity modifier, an initiator, a molecular weight modifier and water, polymerizing a comonomer including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to synthesize a polycarboxylic acid to obtain the polycarboxylic acid water-reducing agent.

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

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

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

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

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

[0054] As 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] As a preferred embodiment, the unsaturated monomer II is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride.

[0056] In the present 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 the 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 the unsaturated monomer II and the hydroxyl group in the 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 a hydroxy dicarboxylic acid and a hydroxy tricarboxylic acid.

[0058] Preferably, the structure of the hydroxy polycarboxylic acid is as shown in Formula 1:

[0059]

[0060] Wherein, L1, L2 and L3 are each independently a single bond or an alkylene group having 1 to 6 carbon atoms (eg, methylene, ethylene, etc.), and R1 is hydrogen or a carboxyl group.

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

[0062] It can be understood that a single bond represents a direct connection between the two groups to which it is associated. 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 esterification product is obtained by a method comprising the following steps: subjecting the unsaturated monomer II and the hydroxy polycarboxylic acid to an esterification reaction in the presence of a catalyst and an optional inhibitor.

[0065] In the present invention, the molar ratio of the unsaturated monomer II to the hydroxy polycarboxylic acid may be (1-10):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 the present invention, the catalyst may be an acid catalyst. Preferably, the catalyst is selected from at least one of benzenesulfonic acid, p-toluenesulfonic acid, ethylsulfonic acid and concentrated sulfuric acid.

[0067] In the present invention, the amount of the catalyst can be selected according to the total amount of the 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, such as 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 the present invention, a polymerization inhibitor may or may not be added to the esterification reaction, and may be selected according to the type of the unsaturated monomer II to reduce the possibility of self-polymerization of the unsaturated monomer II under the 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 inhibitor is 0-1% by mass 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 1-6h, for example, 1h, 2h, 2.5h, 3h, 3.5h, 4h, 5h, etc.

[0071] In the present invention, in order to improve the yield of the esterification product, it is preferred to perform a dehydration operation during the esterification reaction, such as 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 the present invention, the unsaturated macromonomer can be selected from polyether or polyester alkenyl macromonomers containing hydrophilic groups such as carboxyl groups and optional amino groups, sulfonic acid groups and 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 the present invention, the number average molecular weight of the unsaturated macromonomer may be 600 to 6000, for example, 1000, 1500, 2400, 3000, 3500, 4000, 5000, etc.

[0074] As some examples, the unsaturated macromonomer may be a polyether macromonomer such as EPEG2400, EPEG3000, VPEG2400, VPEG3000, or IPEG2400.

[0075] The unsaturated monomer of the present invention can be obtained commercially, for example, it can be selected from the series of polyether products with the brand names of OXAC-608A, OXAC-609E, etc. of Jiangsu Aoke Chemical Co., Ltd.

[0076] In the present invention, as comonomers, the unsaturated macromonomer, the unsaturated monomer I and the unsaturated esterification product can be synthesized into a copolymer product (i.e., polycarboxylic acid) by free radical polymerization. According to some embodiments, the mass ratio of the unsaturated macromonomer, the unsaturated monomer I and the 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 the present 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 a redox initiator, a persulfate initiator, and a peroxide initiator, and preferably the initiator is a redox initiator.

[0078] In the present 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 the present invention, specific examples of the peroxide initiator include, but are not limited to, one or more of hydrogen peroxide, tert-butyl hydroperoxide, and benzoyl oxide.

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

[0081] As some examples, the redox initiator may be hydrogen peroxide-ascorbic acid, hydrogen peroxide-bleaching powder, hydrogen peroxide-BRUGGOLITE E51, hydrogen peroxide-ascorbic acid-ferrous sulfate, hydrogen peroxide-bleaching powder-ferrous sulfate, hydrogen peroxide-BRUGGOLITE E51-ferrous sulfate.

[0082] It is understood that in the description of the redox initiator, the expression "AB" means a combination of A and B, and the expression "ABC" means a combination of A, B and C. For example, "hydrogen peroxide-ascorbic acid" refers to a combination of hydrogen peroxide and ascorbic acid as a redox initiator, and "hydrogen peroxide-ascorbic acid-ferrous sulfate" refers to a combination of hydrogen peroxide, ascorbic acid and ferrous sulfate as a redox initiator. The hydrogen peroxide in the initiator can usually be used in the form of hydrogen peroxide, and the mass content of hydrogen peroxide in the hydrogen peroxide can be, for example, 27.5%.

[0083] In some embodiments, in the redox initiator, the mass ratio of the oxidant to the initiator can be 1:(0.2-2), 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 the present invention, the amount of the initiator can be selected according to the total amount of the 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, the unsaturated monomer I and the 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 the present invention, the molecular weight regulator can be selected from chain transfer agents in free radical polymerization. According to some embodiments, the molecular weight regulator is selected from at least one of thioglycolic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid and sodium hypophosphite.

[0086] In the present invention, the amount of the molecular weight regulator can be selected according to the total amount of the 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, such as 0.3%, 0.4%, 0.5%, 0.8%, 1.2%, 1.5%, 2.2%, 2.5%, 2.5%, 2.8%, etc.

[0087] In the present invention, the viscosity modifier is a trivalent cation salt. The trivalent cation salt refers to a salt that can provide trivalent cations after dissolving in water, and can be a simple salt or a complex salt. In the process of preparing the polycarboxylate water-reducing agent, the cations on the trivalent cation salt can combine with the carboxylate ions on the polycarboxylic acid molecules, effectively reducing the viscosity of the polycarboxylate water-reducing agent. According to some embodiments, the viscosity modifier is at least one of ferric citrate, ferric sulfate and potassium aluminum sulfate.

[0088] In the present invention, the amount of the viscosity modifier can be selected according to the amount of the comonomer. According to some embodiments, the mass amount of the viscosity modifier is 0.1% to 3% of the total mass of the comonomer, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, etc. Usually, a low amount of viscosity modifier may not be enough to form enough bonds with carboxylate ions, and the effect of reducing the viscosity of the water reducer is limited. Too high an amount may affect the adsorption of the water reducer 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 the present invention, the polymerization temperature can be 5 to 90°C, such as 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 temperature can be controlled within any temperature range within the above range, such as between 15 and 30°C, or between 40 and 60°C, etc.

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

[0091] In the present invention, after the polymerization reaction is completed, a base may or may not be added to adjust the pH, which may be determined specifically according to the type of monomer, and preferably the pH of the product is weakly acidic or neutral. As some specific embodiments, the preparation method further includes: after the polymerization reaction, adding a base to adjust the pH of the product to 3 to 7.5. Preferably, the mass amount of the base can be 0 to 1% of the total mass of the comonomer.

[0092] In the present invention, the alkali may include, but is not limited to, sodium hydroxide and / or potassium hydroxide. The alkali is preferably added in the form of alkali solution. As a specific example, the alkali solution is a sodium hydroxide aqueous solution with a mass concentration of 32%.

[0093] In order to improve the effect of the polymerization reaction, according to some preferred embodiments, the preparation method of the polycarboxylate water-reducing agent comprises the following steps:

[0094] 1) uniformly mixing the unsaturated macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water, and dropwise adding thereto an aqueous solution of the unsaturated monomer I, an aqueous solution of the remaining initiator and an aqueous solution of the molecular weight modifier; or

[0095] The unsaturated macromonomer, the unsaturated esterification product, the viscosity modifier, the molecular weight modifier, part of the initiator and water are uniformly mixed, and the aqueous solution of the unsaturated monomer I and the aqueous solution of the remaining initiator are added dropwise thereto;

[0096] 2) After the addition is completed, keep the temperature at 10-60°C to continue the reaction for 0.5-1h;

[0097] Optionally, it also includes:

[0098] 3) Adding the aqueous solution of the base to the product obtained in step 1) to adjust the pH to 3-7.5.

[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 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 a redox initiator, part of the initiator may be one component thereof, and the remaining initiator may be another component thereof.

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

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

[0103] In the present invention, the amount of water can be selected according to the solid content of the required polycarboxylate water-reducing agent and the viscosity of the system. Generally, as the amount of water increases, the viscosity of the polycarboxylate water-reducing agent decreases, which is beneficial to pumping and mass transfer and heat transfer, but the solid content also decreases, which will cause a decrease in production and transportation efficiency. In particular, the preparation method of the present invention can reduce the viscosity of the polycarboxylate water-reducing agent, and is particularly suitable for the preparation of a high-solid content polycarboxylate water-reducing agent. In other words, the preparation method of the present invention can increase the solid content of the polycarboxylate water-reducing agent while maintaining the low viscosity of the water-reducing agent.

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

[0105] The method of the present invention can not only solve the problem of water reducer performance degradation caused by high viscosity and poor mass transfer and heat transfer during the synthesis process, but can also synthesize high-solid content polycarboxylate water reducer and improve the production and transportation efficiency of the polycarboxylate water reducer.

[0106] The second aspect of the present invention provides a polycarboxylate water-reducing agent prepared by the preparation method of the first aspect of the present invention. Compared with the conventional polycarboxylate water-reducing agent, the polycarboxylate water-reducing agent of the present invention has a lower viscosity at the same solid content; or, under the condition of equivalent viscosity, the polycarboxylate water-reducing agent of the present invention has a higher solid content.

[0107] In some embodiments, the polycarboxylate water-reducing agent has a solid content of ≥60% and a viscosity of ≤550 cP at 20°C.

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

[0109] The following are examples of the present invention. The following examples 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 concentration of hydrogen peroxide in the hydrogen peroxide solution was 27.5 wt %, and the concentration of NaOH in the sodium hydroxide aqueous solution was 32 wt %.

[0111] Example 1

[0112] (1) 192.00 g of citric acid, 288.00 g of acrylic acid, 5.90 g of p-toluenesulfonic acid and 2.00 g of hydroquinone were added to a reactor and stirred. The temperature was raised to 105° C., water was removed by nitrogen flow, and the reaction was continued for 3 h to obtain an unsaturated esterification product A-1.

[0113] (2) 12.00 g of unsaturated esterification product A-1, 480 g of EPEG3000, 5.00 g of ferric citrate, 0.016 g of ferrous sulfate and 293.00 g of water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, an acrylic acid aqueous solution (36.00 g of acrylic acid and 10.00 g of water), a hydrogen peroxide aqueous solution (4.30 g of hydrogen peroxide and 15.00 g of water), an aqueous solution of mercaptopropionic acid (2.40 g of mercaptopropionic acid and 15.00 g of water) and an aqueous solution of BRUGGOLITE E51 (0.70 g of BRUGGOLITE E51 and 15.00 g of water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1.0 h, and the material temperature was controlled to be ≤30° C. After the dropping was completed, the mixture was kept warm for 1 h to obtain a copolymer product.

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

[0115] Example 2

[0116] (1) 134.00 g of malic acid, 43.00 g of methacrylic acid, 288.00 g of acrylic acid, 8.80 g of p-toluenesulfonic acid, 1.00 g of hydroquinone, and 0.50 g of phenothiazine were added to a reactor and stirred. The temperature was raised to 110° C. and water was removed by vacuuming. The reaction was continued for 4 h to obtain an unsaturated esterification product A-2.

[0117] (2) 15.00 g of unsaturated esterification product A-2, 380 g of EPEG3000, 100.00 g of VPEG3000, 4.60 g of ferric sulfate, 0.012 g of ferrous sulfate and 290.00 g of water were added to the reactor, the stirrer and the temperature control device were turned on, and after the materials were evenly mixed, an acrylic acid aqueous solution (34.00 g of acrylic acid, 10.00 g of water), a hydrogen peroxide aqueous solution (3.80 g of hydrogen peroxide, 15.00 g of water), a thioglycolic acid aqueous solution (2.20 g of thioglycolic acid, 15.00 g of water), and a bleaching agent aqueous solution (1.20 g of bleaching agent, 15 g of water) were added dropwise, the initial reaction temperature was 13 ° C, the dropping time was 45 min, the material temperature was controlled to be ≤25 ° C during the dropping process, and the temperature was kept for 1 hour after the dropping was completed to obtain a copolymer product;

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

[0119] Example 3

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

[0121] (2) 24.00 g of unsaturated esterification product A-3, 400 g of EPEG2400, 80.00 g of IPEG2400, 4.00 g of ferric citrate, 2.00 g of potassium aluminum sulfate, 7.50 g of sodium hypophosphite, 0.015 g of ferrous sulfate and 314.00 g of water were added to a reactor, and the agitator and temperature control device were turned on. After the materials were evenly mixed, an acrylic acid aqueous solution (24.00 g of acrylic acid, 10.00 g of water), a hydrogen peroxide aqueous solution (5.70 g of hydrogen peroxide, 15.00 g of water), and an ascorbic acid aqueous solution (1.50 g of ascorbic acid, 15.00 g of water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1 h, and the material temperature was controlled to be ≤30° C. After the dropping was completed, the temperature was kept for 1 h to obtain a copolymer product;

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

[0123] Example 4

[0124] Take 15.00g of unsaturated esterification product A-1 prepared in Example 1, 480g of EPEG3000, 6.00g of ferrous sulfate, 0.012g of ferrous sulfate and 297.00g of water, add them into the reactor, turn on the agitator and the temperature control device, until the materials are evenly mixed, start to drip acrylic acid, sodium acrylate and maleic anhydride aqueous solution (acrylic acid 18.00g, sodium acrylate 12.00g, maleic anhydride 6.00g, water 20.00g), hydrogen peroxide aqueous solution (hydrogen peroxide 4.00g, water 10.00g), thioglycolic acid aqueous solution (thioglycolic acid 2.00g, water 10.00g), bleaching powder aqueous solution (bleaching powder 1.30g, water 15.00g), the initial reaction temperature is 20°C, the dropping time is 1h, the material temperature is controlled to be ≤25°C during the dropping process, and the addition is completed. Keep warm for 1.5h to obtain a copolymer product;

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

[0126] Example 5

[0127] (1) 192.00 g of citric acid, 144.00 g of acrylic acid, 2.90 g of p-toluenesulfonic acid and 1.30 g of hydroquinone were added to a reactor and stirred. The temperature was raised to 105° C., water was removed by nitrogen flow, and the reaction was continued for 3 h to obtain an unsaturated esterification product A-4.

[0128] (2) 12.00 g of unsaturated esterification product A-4, 480 g of EPEG3000, 5.00 g of potassium aluminum sulfate, 0.016 g of ferrous sulfate and 296.00 g of water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, acrylic acid, sodium methacrylate aqueous solution (33.00 g of acrylic acid, 5.00 g of sodium methacrylate, 20.00 g of water), hydrogen peroxide (4.1 g of hydrogen peroxide, 10.00 g of water), mercaptopropionic acid aqueous solution (2.20 g of mercaptopropionic acid, 10.00 g of water), BRUGGOLITE E51 aqueous solution (0.70 g of BRUGGOLITE E51, 15.00 g of water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1.0 h, and the material temperature was controlled to be ≤40° C. After the dropping was completed, the temperature was kept at 1 h to obtain a copolymer product.

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

[0130] Comparative Example 1

[0131] (1) 480.00 g EPEG3000, 5.00 g ferric citrate, 0.016 g ferrous sulfate and 293.00 g water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, an acrylic acid aqueous solution (36.00 g acrylic acid, 10.00 g water), a hydrogen peroxide aqueous solution (4.30 g hydrogen peroxide, 15.00 g water), a mercaptopropionic acid aqueous solution (2.40 g mercaptopropionic acid, 15.00 g water), and a BRUGGOLITE E51 aqueous solution (0.70 g BRUGGOLITE E51, 15.00 g water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1.0 h, and the material temperature was controlled to be ≤30° C. During the dropping process, the temperature was kept at 1 h after the dropping was completed to obtain a copolymer product.

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

[0133] Comparative Example 2

[0134] (1) 192.00 g of citric acid, 288.00 g of acrylic acid, 5.90 g of p-toluenesulfonic acid, and 2.00 g of hydroquinone were added to a reactor and stirred. The temperature was raised to 105° C., water was removed by nitrogen flow, and the reaction was continued for 3 h to obtain an esterification product A-1.

[0135] (2) 12.00 g of the esterification product A-1 obtained in step (1), 480.00 g of EPEG3000, 0.016 g of ferrous sulfate and 293.00 g of water were added to the reactor, the stirrer and the temperature control device were turned on, and after the materials were evenly mixed, an acrylic acid aqueous solution (36.00 g of acrylic acid, 10.00 g of water), a hydrogen peroxide aqueous solution (4.30 g of hydrogen peroxide, 15.00 g of water), a mercaptopropionic acid aqueous solution (2.40 g of mercaptopropionic acid, 15.00 g of water), and a BRUGGOLITE E51 aqueous solution (0.70 g of BRUGGOLITE E51, 15.00 g of water) were added dropwise, the initial reaction temperature was 15° C., the dropping time was 1.0 h, the material temperature was controlled to be ≤30° C., and the temperature was kept for 1 h after the dropping was completed to obtain a copolymer product;

[0136] (3) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain a polyacid water reducer as a comparative sample PCE-2.

[0137] Comparative Example 3

[0138] (1) 480.00 g EPEG3000, 0.016 g ferrous sulfate and 293.00 g water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, an acrylic acid aqueous solution (36.00 g acrylic acid, 10.00 g water), a hydrogen peroxide aqueous solution (4.30 g hydrogen peroxide, 15.00 g water), a mercaptopropionic acid aqueous solution (2.40 g mercaptopropionic acid, 15.00 g water), and a BRUGGOLITE E51 aqueous solution (0.70 g BRUGGOLITE E51, 15.00 g water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1.0 h, and the material temperature was controlled to be ≤30° C. During the dropping process, the temperature was kept at 1 h after the dropping was completed to obtain a copolymer product.

[0139] (2) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain a polyacid water reducer as a comparative sample PCE-3.

[0140] Comparative Example 4

[0141] (1) 480.00 g EPEG3000, 0.016 g ferrous sulfate and 455.00 g water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, an acrylic acid aqueous solution (including 36.00 g acrylic acid and 10.00 g water), a hydrogen peroxide aqueous solution (4.30 g hydrogen peroxide and 15.00 g water), a mercaptopropionic acid aqueous solution (2.40 g mercaptopropionic acid and 15.00 g water), and a BRUGGOLITE E51 aqueous solution (0.70 g BRUGGOLITE E51 and 15.00 g water) were added dropwise. The initial reaction temperature was 15° C., the dropping time was 1.0 h, and the material temperature was controlled to be ≤30° C. During the dropping process, the temperature was kept at 1 h after the dropping was completed to obtain a copolymer product.

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

[0143] Test Case

[0144] The following test examples are used to illustrate the performance of polycarboxylate water reducers 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: Use a rotational viscometer NDJ-8T to test the viscosity of each polycarboxylate water-reducing agent at 20°C (using rotor No. 2, speed 30 rpm).

[0146] 2. Water reduction rate test: Carry out equal-consolidation concrete performance test on each polycarboxylate water reducer in accordance with GB / T8076-2008.

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

[0148] Table 1

[0149]

[0150]

[0151] Combined with Table 1, the comparison of the results of KZJ-1 and PCE-1 shows that the PCE-1 (Comparative Example 1) without the addition of the unsaturated esterification product A-1 has a lower water reduction rate than the KZJ-1 prepared in Example 1, and a higher viscosity than KZJ-1. This is mainly because the number of carboxylic acid structures in the molecular structure of the copolymer is reduced by not using the unsaturated esterification product A-1, resulting in a decrease in the water reduction rate. At the same time, there are fewer carboxylic acid structures that can form a bond with the viscosity modifier, so the viscosity is also greater.

[0152] The comparison results of KZJ-1 and PCE-2 show that the water reduction rate of PCE-2 (Comparative Example 2) without the addition of viscosity modifier is slightly lower than that of KZJ-1, and the viscosity is significantly higher than that of KZJ-1, indicating that under the same monomer composition, the viscosity is higher without the addition of viscosity modifier, and due to the high viscosity during the synthesis process, it will affect the mass transfer and heat transfer effects, resulting in the water reduction performance of the synthesized product is also relatively poor.

[0153] The comparison results of KZJ-1 and PCE-3 show that the water reduction rate of PCE-3 without the addition of unsaturated esterification product A-1 and viscosity regulator is much lower than that of KZJ-1, and the viscosity is also much higher than that of KZJ-1. This is mainly because the absence of esterification product A-1 reduces the number of carboxylic acid structures in the product molecular structure and reduces the water reduction rate. At the same time, without the viscosity regulator, the viscosity is high during the synthesis process, which affects the mass transfer and heat transfer effects, making the final product performance worse.

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

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

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in 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 each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a polycarboxylate water-reducing agent, characterized in that: include: In the presence of a viscosity modifier, an initiator, a molecular weight modifier and water, a copolymerization reaction is carried out on a comonomer including an unsaturated macromonomer, an unsaturated monomer I and an unsaturated esterification product to obtain a polycarboxylic acid water-reducing agent; 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 an unsaturated carboxylic acid, an unsaturated carboxylate and an unsaturated carboxylic anhydride; The unsaturated monomer II is an unsaturated carboxylic acid and / or an unsaturated carboxylic anhydride; The viscosity modifier is a trivalent cation salt.

2. The preparation method according to claim 1, characterized in that: The hydroxy polycarboxylic acid is at least one of a hydroxy dibasic acid and a hydroxy tribasic acid; Preferably, the structure of the hydroxy polycarboxylic acid is as shown in Formula 1: Wherein, L1, L2 and L3 are each independently a single bond or an alkylene group having 1 to 6 carbon atoms, and R1 is hydrogen or a carboxyl group; Preferably, the hydroxypolycarboxylic acid is citric acid and / or malic acid.

3. The preparation method according to claim 1 or 2, characterized in that: The unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid and itaconic acid; the unsaturated carboxylic acid salt is selected from at least one of sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, sodium itaconate and potassium itaconate; the unsaturated carboxylic anhydride is selected from maleic anhydride and / or itaconic anhydride; Preferably, the unsaturated esterification product is prepared by a method comprising the steps of: The unsaturated monomer II and the hydroxy polycarboxylic acid are subjected to an esterification reaction in the presence of a catalyst and an optional inhibitor; Preferably, the molar ratio of the unsaturated monomer II to the hydroxy polycarboxylic acid is (1-10):1; Preferably, the catalyst is selected from at least one of benzenesulfonic acid, p-toluenesulfonic acid, ethylsulfonic acid and concentrated sulfuric acid; Preferably, 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; Preferably, the polymerization inhibitor is selected from at least one of hydroquinone and phenothiazine; Preferably, the mass amount of the polymerization inhibitor is 0 to 1% of the total mass of the unsaturated monomer II and the hydroxy polycarboxylic acid; Preferably, the temperature of the esterification reaction is 80-130° C., and the reaction time is 1-6 hours.

4. The preparation method according to any one of claims 1 to 3, 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.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mass ratio of the unsaturated macromonomer, the unsaturated monomer I and the unsaturated esterification product is 200:(5-40):(1-15); Preferably, the polymerization reaction temperature is 5 to 90° C., and the reaction time is 1 to 5 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The viscosity modifier is at least one of ferric citrate, ferric sulfate and potassium aluminum sulfate; Preferably, the mass amount of the viscosity modifier is 0.1% to 3% of the total mass of the comonomer, and more preferably 0.5% to 1.5%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The initiator is at least one of a redox initiator, a persulfate initiator and a peroxide initiator, preferably a redox initiator; Preferably, 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, bleaching powder, BRUGGOLITE E51 and ascorbic acid; Preferably, the mass ratio of the oxidant to the initiator is 1:(0.2-2); Preferably, the mass amount of the initiator is 0.1% to 2% of the total mass of the comonomer; Preferably, the molecular weight regulator is selected from at least one of thioglycolic acid, mercaptoethanol, mercaptopropionic acid, sulfonated mercaptopropionic acid and sodium hypophosphite; Preferably, the mass amount of the molecular weight regulator is 0.2% to 3% of the total mass of the comonomer.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: 1) uniformly mixing the unsaturated macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water, and dropwise adding thereto an aqueous solution of the 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 initiator and water are uniformly mixed, and the aqueous solution of unsaturated monomer I and the aqueous solution of the remaining initiator are added dropwise thereto; wherein, The dripping time is controlled to be 0.5 to 3 hours, and the temperature of the reaction system during the dripping process is 10 to 60° C.; 2) After the addition is completed, keep the temperature at 10-60°C to continue the reaction for 0.5-1h; Preferably, the amount of water used is such that the solid content of the prepared polycarboxylate water-reducing agent is not less than 55%, more preferably not less than 60%.

9. The polycarboxylate water-reducing agent prepared by the preparation method according to any one of claims 1 to 8; Preferably, the polycarboxylate water-reducing agent has a solid content of ≥60% and a viscosity of ≤550 cP at 20°C.

10. Use of the polycarboxylate water-reducing agent according to claim 9 in building materials.

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