Polycarboxylic acid slump retaining agent as well as preparation method and application thereof

Abstract

The invention belongs to the field of building materials, and provides a polycarboxylic acid slump retaining agent as well as a preparation method and application thereof. The preparation method of the polycarboxylic acid slump retaining agent comprises the following step: in the presence of water, a viscosity modifier, an initiator and an optional chain transfer agent, carrying out polymerization reaction on comonomers including an unsaturated polyether macromonomer, an unsaturated carboxylic ester monomer, an unsaturated monomer I and an unsaturated esterification product to synthesize polycarboxylic acid, thereby obtaining the polycarboxylic acid slump retaining agent. According to the preparation method, the viscosity of the polycarboxylic acid slump retaining agent can be reduced, and the polycarboxylic acid slump retaining agent with high solid content is obtained.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and specifically provides a polycarboxylic acid collapse-preventing agent and a preparation method and application thereof. Background Art

[0002] Slump-preventing agent is an important admixture in concrete. It can improve the fluidity of concrete and significantly reduce the slump loss, ensuring the operability and uniformity of concrete during the construction process. Polycarboxylic acid slump-preventing agent has developed rapidly in recent years due to its superior performance and pollution-free production. In addition to being affected by factors such as synthesis process, raw material quality and concrete mix ratio, the performance of polycarboxylic acid slump-preventing agent is also directly affected by its solid content in concrete. In addition, a higher solid content can not only save the long-distance transportation cost of the admixture, but also be more conducive to the application of the admixture in large-scale construction occasions.

[0003] Increasing the solid content of polycarboxylic acid collapse preventer products can save transportation costs, achieve energy conservation and emission reduction, and be low-carbon and environmentally friendly. However, polycarboxylic acid collapse preventers with high solid content have problems such as high viscosity, difficulty in synthesis and pumping, and poor product performance. Summary of the invention

[0004] In view of the above problems existing in the prior art, the object of the present invention is to provide a polycarboxylic acid collapse-preventing agent and a preparation method and application thereof. The preparation method of the present invention can reduce the viscosity of the polycarboxylic acid collapse-preventing agent and obtain a polycarboxylic acid collapse-preventing agent with a high solid content.

[0005] To achieve the above object, the first aspect of the present invention provides a method for preparing a polycarboxylic acid collapse preventing agent, the method comprising: in the presence of water, a viscosity modifier, an initiator and an optional chain transfer agent, polymerizing comonomers including an unsaturated polyether macromonomer, an unsaturated carboxylic acid ester monomer, an unsaturated monomer I and an unsaturated esterification product to synthesize a polycarboxylic acid to obtain a polycarboxylic acid collapse preventing agent; wherein:

[0006] The structure of the unsaturated carboxylate monomer is shown in Formula 1:

[0007]

[0008] In formula 1, R1 is hydrogen or methyl, and R2 is hydrogen or an alkyl group having 1 to 4 carbon atoms;

[0009] The unsaturated monomer I is at least one of an unsaturated carboxylic acid, an unsaturated carboxylate and an unsaturated carboxylic anhydride;

[0010] The unsaturated esterification product is the reaction product of unsaturated monomer II and hydroxy polycarboxylic acid;

[0011] The unsaturated monomer II is an unsaturated carboxylic acid and / or an unsaturated carboxylic anhydride;

[0012] The viscosity modifier is a trivalent cation salt.

[0013] In the preparation method of the present invention, unsaturated esterification products are used to carry out polymerization reaction with unsaturated carboxylic acid ester monomers, unsaturated monomers I and unsaturated polyether macromonomers, so that a polycarboxylic acid unit structure can be introduced into the polycarboxylic acid molecular chain, and trivalent cation salts are used as viscosity modifiers, so that trivalent cations can be introduced into the polycarboxylic acid molecular chain, and the carboxylate ions on the polycarboxylic acid molecular chain are combined with the trivalent cations to shrink the conformation of the polycarboxylic acid molecule in water, thereby reducing the viscosity of the polycarboxylic acid collapse-preventing agent itself. The method of the present invention not only solves the problem of performance degradation caused by high viscosity during the synthesis of a high-solid-content collapse-preventing agent, but also improves the production and transportation efficiency of the polycarboxylic acid collapse-preventing agent.

[0014] In some embodiments of the present invention, the unsaturated polyether 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.

[0015] In some embodiments of the present invention, the unsaturated carboxylic acid ester monomer is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate.

[0016] 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 at least one of maleic anhydride, itaconic anhydride and methacrylic anhydride.

[0017] In some embodiments of the present invention, the structure of the hydroxy polycarboxylic acid is as shown in Formula 2:

[0018]

[0019] Here, L1, L2 and L3 are each independently a single bond or an alkylene group having 1 to 6 carbon atoms, and R is hydrogen or a carboxyl group.

[0020] Furthermore, the hydroxy polycarboxylic acid is selected from citric acid and / or malic acid.

[0021] 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.

[0022] Furthermore, the molar ratio of the unsaturated monomer to the hydroxy polycarboxylic acid is (1-10):1.

[0023] Furthermore, the temperature of the esterification reaction is 80-130° C., and the reaction time is 1-6 hours.

[0024] Furthermore, the catalyst is selected from at least one of benzenesulfonic acid, p-toluenesulfonic acid, ethylsulfonic acid and concentrated sulfuric acid.

[0025] Furthermore, the polymerization inhibitor is hydroquinone and / or phenothiazine.

[0026] In some embodiments of the present invention, relative to 100 parts by weight of the unsaturated polyether macromonomer, the amount of the unsaturated esterification product is 1 to 8 parts by weight, the amount of the unsaturated monomer I is 3 to 12 parts by weight, and the amount of the unsaturated carboxylic acid ester monomer is 15 to 40 parts by weight.

[0027] In some embodiments of the present invention, the viscosity modifier is selected from at least one of ferric citrate, ferric sulfate and potassium aluminum sulfate.

[0028] In some embodiments of the present invention, the mass amount of the viscosity modifier is 0.1% to 2% of the total mass of the comonomer.

[0029] In some embodiments of the present invention, the polymerization reaction temperature is 5 to 90° C., and the reaction time is 1 to 8 hours.

[0030] In some embodiments of the present invention, the amount of water used is such that the solid content of the prepared polycarboxylic acid collapse-preventing agent is not less than 55%.

[0031] Furthermore, the amount of water used is such that the solid content of the prepared polycarboxylic acid collapse-preventing agent is not less than 60%.

[0032] In some embodiments of the present invention, the initiator is a redox initiator.

[0033] Furthermore, 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.

[0034] Furthermore, the mass ratio of the oxidizing agent to the reducing agent is 1:(0.2-2).

[0035] In some embodiments of the present invention, the mass amount of the initiator is 0.1% to 1% of the total mass of the comonomer.

[0036] In some embodiments of the present invention, the chain transfer agent is selected from at least one of mercaptopropionic acid, thioglycolic acid, mercaptoethanol, sodium formate and sodium hypophosphite.

[0037] In some embodiments of the present invention, the mass amount of the chain transfer agent is 0.1% to 2% of the total mass of the comonomer.

[0038] In some embodiments of the present invention, the preparation method comprises the following steps:

[0039] (1) the unsaturated polyether macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water are uniformly mixed, and a mixed aqueous solution of the unsaturated monomer I and the unsaturated carboxylic acid ester monomer, an aqueous solution of the remaining initiator and an aqueous solution of the molecular weight modifier are added dropwise thereto; or

[0040] The unsaturated polyether macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of initiator and water are uniformly mixed, and a mixed aqueous solution of unsaturated monomer I and unsaturated carboxylic acid ester monomer and an aqueous solution of the remaining initiator are added dropwise thereto; wherein,

[0041] 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.;

[0042] (2) After the addition is completed, the temperature is kept at 10-60°C to continue the reaction for 0.5-1 hour.

[0043] The second aspect of the present invention provides a polycarboxylic acid collapse-preserving agent prepared by the preparation method described in the first aspect of the present invention. The polycarboxylic acid collapse-preserving agent of the present invention still has a relatively low viscosity under the condition of high solid content.

[0044] The third aspect of the present invention provides use of the polycarboxylic acid collapse retaining agent described in the second aspect of the present invention in building materials.

[0045] 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

[0046] The following describes the implementation of the present application in detail. The implementation described below is exemplary and is only used to explain the present application, and cannot be understood as limiting the present application.

[0047] The "range" disclosed in the present application 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 end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an unclearly recorded range, and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded 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 unclearly recorded range.

[0048] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0049] In a first aspect, the present invention provides a method for preparing a polycarboxylic acid collapse-preventing agent, the preparation method comprising: in the presence of water, a viscosity modifier, an initiator and an optional chain transfer agent, polymerizing comonomers including an unsaturated polyether macromonomer, an unsaturated carboxylic acid ester monomer, an unsaturated monomer I and an unsaturated esterification product to form a copolymer product (i.e., a polycarboxylic acid), thereby obtaining a polycarboxylic acid collapse-preventing agent.

[0050] In the present invention, the unsaturated polyether macromonomer can be selected from polyether alkenyl macromonomers containing hydrophilic groups such as carboxyl groups and optional amino groups, sulfonic acid groups and other hydrophilic groups. Preferably, the unsaturated polyether macromonomer is 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).

[0051] In the present invention, the number average molecular weight of the unsaturated polyether macromonomer may be 600 to 6000, for example, 1000, 1500, 2400, 3000, 3500, 4000, 5000, etc.

[0052] As some examples, the unsaturated polyether macromonomer may be EPEG2400, EPEG3000, VPEG2400, VPEG3000, IPEG2400 or the like polyether macromonomer.

[0053] The unsaturated polyether macromonomer of the present invention can be obtained commercially, for example, selected from the OXAC-608A, OXAC-609E and other series of polyether products of Jiangsu Aoke Chemical Co., Ltd.

[0054] In the present invention, the structure of the unsaturated carboxylic acid ester monomer is as shown in Formula 1:

[0055]

[0056] In Formula 1, R1 is hydrogen or a methyl group, and R2 is hydrogen or an alkyl group having 1 to 4 carbon atoms.

[0057] As some examples, R2 can be hydrogen, methyl, ethyl, n-propyl, isopropyl, or n-butyl.

[0058] Preferably, the unsaturated carboxylic acid ester monomer is at least one selected from hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA) and hydroxyethyl methacrylate (HEMA).

[0059] In some embodiments, relative to 100 parts by weight of the unsaturated polyether macromonomer, the amount of the unsaturated carboxylic acid ester monomer is 15 to 40 parts by weight, for example, 15 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 38 parts by weight, 40 parts by weight, etc.

[0060] 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.

[0061] 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.

[0062] 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).

[0063] In the present invention, the unsaturated carboxylic anhydride may be a carboxylic anhydride having a double bond and carbon atoms of 3 to 10. Preferably, the unsaturated carboxylic anhydride is at least one of maleic anhydride (MA), itaconic anhydride (ITA) and methacrylic anhydride.

[0064] 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.

[0065] 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.

[0066] As a preferred embodiment, the unsaturated monomer II is selected from one or more of acrylic acid, methacrylic acid and maleic anhydride.

[0067] 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.

[0068] In some embodiments, the hydroxy polycarboxylic acid may be at least one of a hydroxy dicarboxylic acid and a hydroxy tricarboxylic acid.

[0069] Preferably, the structure of the hydroxy polycarboxylic acid is as shown in Formula 2:

[0070]

[0071] 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 R is hydrogen or a carboxyl group.

[0072] 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.

[0073] It can be understood that a single bond indicates a direct connection between the two groups to which it is associated. For example, when L2 is a single bond, the structure of Formula 2 is

[0074] More preferably, the hydroxypolycarboxylic acid is at least one of citric acid and malic acid.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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, in order to reduce the possibility of self-polymerization of the unsaturated monomer II under the esterification reaction conditions. Preferably, the polymerization inhibitor is selected from hydroquinone and / or phenothiazine.

[0080] 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%, 0.6%, 0.8%, 1%, etc.

[0081] In some embodiments, the temperature of the esterification reaction is 80-130°C, for example, 80°C, 85°C, 90°C, 95°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.

[0082] 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.

[0083] In some embodiments, relative to 100 parts by weight of the unsaturated polyether macromonomer, the amount of the unsaturated esterification product is 1 to 8 parts by weight, for example, 1 part by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.1 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, etc.

[0084] In some embodiments, relative to 100 parts by weight of the unsaturated polyether macromonomer, the amount of the unsaturated monomer I is 3 to 12 parts by weight, for example, 3 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 7.2 parts by weight, 7.5 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11.5 parts by weight, 12 parts by weight, etc.

[0085] 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 polycarboxylic acid collapse-preventing agent, the cations on the trivalent cation salt can combine with the carboxylate ions on the polycarboxylic acid molecule, effectively reducing the viscosity of the polycarboxylic acid collapse-preventing agent. According to some embodiments, the viscosity modifier is at least one of ferric citrate, ferric sulfate and potassium aluminum sulfate.

[0086] 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 2% of the total mass of the comonomer (i.e., the total amount of the unsaturated polyether macromonomer, the unsaturated monomer I, the unsaturated carboxylic acid ester monomer and the unsaturated esterification product), such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.7%, 1.8%, etc. Usually, a low amount of viscosity modifier may not be enough to form enough combinations with carboxylate ions, and the viscosity reduction effect on the collapse retaining agent is limited. Too high an amount may affect the use effect of the collapse retaining agent. Preferably, the mass amount of the viscosity modifier is 0.3% to 1% of the total mass of the comonomer.

[0087] In the present invention, the polymerization temperature can be 5-90°C, such as 5°C, 10°C, 13°C, 15°C, 18°C, 30°C, 32°C, 35°C, 40°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 10-40°C, between 13-25°C, between 15-30°C, between 40-60°C, etc.

[0088] In the present invention, the polymerization reaction time can be determined according to the conversion degree of the reactants, and can generally be 1 to 8 hours, such as 1 hour, 2 hours, 3.5 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0089] 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.

[0090] In the present invention, the alkali may include but is not limited to sodium hydroxide and 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 15% to 35%.

[0091] In the present invention, the initiator can be selected from various water-soluble initiators, for example, one or more selected from redox initiators, persulfate initiators, and peroxide initiators. Preferably, the initiator is a redox initiator.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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%.

[0097] In some embodiments, in the redox initiator, the mass ratio of the oxidant to the initiator can be 1:(0.2-2), for example, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:1, 1:2, etc.

[0098] 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 1% of the total mass of the comonomers, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0099] In some embodiments, the chain transfer agent may be selected from at least one of mercaptopropionic acid, thioglycolic acid, mercaptoethanol, sodium formate, and sodium hypophosphite.

[0100] In some embodiments, the mass dosage of the chain transfer agent is 0.1% to 2% of the total mass of the comonomer, 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.

[0101] In order to improve the effect of the polymerization reaction, according to some preferred embodiments, the preparation method of the polycarboxylic acid collapse retaining agent comprises the following steps:

[0102] (1) uniformly mixing the unsaturated polyether macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water, and dropwise adding thereto a mixed aqueous solution of the unsaturated monomer I and the hydroxycarboxylic acid ester, an aqueous solution of the remaining initiator and an aqueous solution of the molecular weight modifier; or

[0103] The unsaturated polyether macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of initiator and water are uniformly mixed, and a mixed aqueous solution of unsaturated monomer I and hydroxycarboxylic acid ester and an aqueous solution of the remaining initiator are added dropwise thereto; wherein,

[0104] 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.;

[0105] (2) After the addition is completed, the temperature is kept at 10-60°C to continue the reaction for 0.5-1 hour.

[0106] Optionally, it also includes:

[0107] (3) Adding the aqueous solution of the alkali to the product obtained in step (2) to adjust the pH to 3 to 7.5.

[0108] 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.

[0109] 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, which is beneficial to improving the stability of the product.

[0110] In step (2), the heat preservation after the dropwise addition is completed can further improve the conversion degree of the reactants.

[0111] In the present invention, the amount of water can be selected according to the solid content of the required polycarboxylic acid collapse-preventing agent and the viscosity of the system. Generally, as the amount of water increases, the viscosity of the polycarboxylic acid collapse-preventing 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 polycarboxylic acid collapse-preventing agent, and is particularly suitable for the preparation of a high-solid content polycarboxylic acid collapse-preventing agent. In other words, the preparation method of the present invention can increase the solid content of the polycarboxylic acid collapse-preventing agent while maintaining the low viscosity of the collapse-preventing agent.

[0112] In some embodiments, the amount of water used is such that the solid content of the polycarboxylic acid collapse retaining agent is not less than 55%, preferably not less than 60%.

[0113] In a second aspect, the present invention provides a polycarboxylic acid collapse-preventing agent prepared by the preparation method described in the first aspect of the present invention. Compared with a conventional polycarboxylic acid collapse-preventing agent, the polycarboxylic acid collapse-preventing agent of the present invention has a lower viscosity at the same solid content; or, under the condition of equivalent viscosity, the polycarboxylic acid collapse-preventing agent of the present invention has a higher solid content.

[0114] In some embodiments, the polycarboxylic acid slump retaining agent has a solid content of ≥60% and a viscosity of <600 cP at 20°C.

[0115] In a third aspect, the present invention provides the use of the polycarboxylic acid collapse-preventing agent described in the second aspect of the present invention in building materials. The polycarboxylic acid collapse-preventing agent of the present invention has the characteristics of low viscosity and has a high collapse-preventing effect on building materials, especially concrete.

[0116] 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.

[0117] In the following examples and comparative examples, the concentration of hydrogen peroxide in the hydrogen peroxide solution was 27.5 wt %, and the mass concentration of NaOH in the sodium hydroxide aqueous solution was 32%.

[0118] Example 1

[0119] (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.

[0120] (2) 12 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, a mixed aqueous solution of acrylic acid and hydroxyethyl acrylate (36.00 g of acrylic acid, 173.00 g of hydroxyethyl acrylate, 127.60 g of water), an aqueous hydrogen peroxide solution (4.30 g of hydrogen peroxide, 15.00 g of water), an aqueous solution of mercaptopropionic acid (2.40 g of mercaptopropionic acid, 15.00 g of water), and an aqueous solution of BRUGGOLITE E51 (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 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.

[0121] (3) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylic acid collapse retaining agent KZJ-1.

[0122] Example 2

[0123] (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.

[0124] (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, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, a mixed aqueous solution of acrylic acid and hydroxypropyl acrylate (34.00 g of acrylic acid, 163.00 g of hydroxypropyl acrylate, 122.30 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 powder aqueous solution (1.20 g of bleaching powder, 15 g of water) were added dropwise. The initial reaction temperature was 17° C., the dropping time was 50 min, and the material temperature was controlled to be ≤30° C. During the dropping process, the mixture was kept warm for 1 h to obtain a copolymer product.

[0125] (3) Add 12 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylic acid collapse-preventing agent KZJ-2.

[0126] Example 3

[0127] (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.

[0128] (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, a mixed aqueous solution of acrylic acid and hydroxyethyl methacrylate (24.00 g of acrylic acid, 115.00 g of hydroxyethyl methacrylate, 88.00 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 13° C., the dropping time was 1 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;

[0129] (3) Add 2 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylic acid collapse-preventing agent KZJ-3.

[0130] Example 4

[0131] Take 15.00 g of the unsaturated esterification product A-1 prepared in Example 1, 480 g EPEG3000, 6.0g ferric sulfate, 0.012g ferrous sulfate and 310.00g water were added to the reactor, and the agitator and temperature control device were turned on. After the materials were evenly mixed, a mixed aqueous solution of acrylic acid, sodium acrylate, maleic anhydride and hydroxyethyl acrylate (18.00g acrylic acid, 12.00g sodium acrylate, 6.00g maleic anhydride, 173.00g hydroxyethyl acrylate, 124.70g water), a hydrogen peroxide aqueous solution (4.00g hydrogen peroxide, 10.00g water), a thioglycolic acid aqueous solution (2.00g thioglycolic acid, 10.00g water), and a bleaching solution (1.30g bleaching solution, 15.00g water) were added dropwise. The initial reaction temperature was 20°C, the dropping time was 1h, and the material temperature was controlled to be ≤25°C during the dropping process. After the dropping was completed, the temperature was kept for 1.5h to obtain a copolymer product.

[0132] (3) Add 4 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylic acid collapse-preventing agent KZJ-4.

[0133] Example 5

[0134] (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.

[0135] (2) 12 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 300.00 g of water were added to a reactor, and the agitator and temperature control device were turned on. After the materials were evenly mixed, a mixed aqueous solution of acrylic acid, sodium methacrylate and hydroxyethyl acrylate (33.00 g of acrylic acid, 5.00 g of sodium methacrylate, 183.00 g of hydroxyethyl acrylate, 137.20 g of water), hydrogen peroxide (4.1 g of hydrogen peroxide, 10.00 g of water), an aqueous solution of mercaptopropionic acid (2.20 g of mercaptopropionic acid, 10.00 g of water), and an aqueous solution of BRUGGOLITE E51 (BRUGGOLITE E51 0.70g, water 15.00g), the initial reaction temperature is 15°C, the dropping time is 1.0h, the material temperature is controlled to be ≤40°C during the dropping process, and the temperature is kept for 1h after the dropping is completed to obtain a copolymer product;

[0136] (3) Add 5.00 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain polycarboxylic acid collapse retaining agent KZJ-5.

[0137] Comparative Example 1

[0138] (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, a mixed aqueous solution of acrylic acid and hydroxyethyl acrylate (36.00 g acrylic acid, 173.00 g hydroxyethyl acrylate, 127.60 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 collapse retaining agent, which is recorded as comparative sample PCE-1.

[0140] Comparative Example 2

[0141] (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.

[0142] (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, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, a mixed aqueous solution of acrylic acid and hydroxyethyl acrylate (36.00 g of acrylic acid, 173.00 g of hydroxyethyl acrylate, 127.60 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, 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.

[0143] (3) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (2) to obtain a polyacid collapse retainer, which is used as a comparative sample PCE-2.

[0144] Comparative Example 3

[0145] (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, a mixed aqueous solution of acrylic acid and hydroxyethyl acrylate (36.00 g acrylic acid, 173.00 g hydroxyethyl acrylate, 127.60 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.

[0146] (2) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain a polyacid collapse retainer, which is used as a comparative sample PCE-3.

[0147] Comparative Example 4

[0148] (1) 480.00 g EPEG3000, 0.016 g ferrous sulfate and 513.00 g water were added to a reactor, and the stirrer and temperature control device were turned on. After the materials were evenly mixed, a mixed aqueous solution of acrylic acid and hydroxyethyl acrylate (36.00 g acrylic acid, 173.00 g hydroxyethyl acrylate, 127.60 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. After the dropping was completed, the mixture was kept warm for 1 h to obtain a copolymer product.

[0149] (2) Add 6 g of sodium hydroxide aqueous solution to the copolymer product obtained in step (1) to obtain a polyacid collapse retaining agent, which is used as a comparative sample PCE-4.

[0150] Test Case

[0151] The following test examples are used to illustrate the performance of the polycarboxylic acid collapse inhibitors KZJ-1 to KZJ-5 and comparative samples PCE-1 to PCE-4 prepared in the above examples and comparative examples.

[0152] 1. Viscosity test: The viscosity of each polycarboxylic acid slump retaining agent was tested at 20°C using a rotational viscometer NDJ-8T (rotor No. 2, rotation speed 30 rpm). The test results are shown in Table 1.

[0153] Table 1

[0154]

[0155]

[0156] 2. Collapse performance test: Referring to the concrete mixture performance test method of GB / T 8076-2008 "Concrete Admixtures", the collapse agent and the water reducer PC (Point-S polycarboxylate water reducer, Kezhijie New Materials Co., Ltd.) were mixed (the mass ratio of collapse agent to water reducer PC was 3:7) to form an admixture sample with a solid content of 20%, and a concrete performance comparison test was carried out. The specific concrete mix is ​​shown in Table 2, and the test results are shown in Table 3:

[0157] Table 2

[0158] <![CDATA[Cement (kg / m 3 )]]> <![CDATA[Sand (kg / m 3 )]]> <![CDATA[Stone (kg / m 3 )]]> <![CDATA[Water (kg / m 3 )]]> 360 865 980 175

[0159] Table 3

[0160]

[0161] Combining Table 1 and Table 3, the comparison of the results of KZJ-1 and PCE-1 shows that PCE-1 (Comparative Example 1) without the addition of unsaturated esterification product A-1 has a lower collapse retention performance than KZJ-1 prepared in Example 1, and its viscosity is also higher than KZJ-1. This is mainly because the absence of unsaturated esterification product A-1 reduces the number of carboxylic acid structures in the molecular structure of the copolymer, and reduces the number of carboxylic acid structures that can form a bond with the viscosity modifier. Therefore, the viscosity is relatively high, and the high viscosity affects the mass transfer and heat transfer effects, resulting in the poor collapse retention performance of the product.

[0162] The comparison results of KZJ-1 and PCE-2 show that the collapse retention performance of PCE-2 (Comparative Example 2) without the addition of viscosity modifier is worse than that of KZJ-1, and the viscosity is significantly higher than that of KZJ-1, indicating that under the same copolymer 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 poor collapse retention performance of the synthesized product.

[0163] The comparison results between KZJ-1 and PCE-3 show that the collapse retention performance of PCE-3 without the addition of unsaturated esterification product A-1 and viscosity regulator is worse than that of KZJ-1, and the viscosity is also higher than that of KZJ-1.

[0164] The comparison results of PCE-3 and PCE-4 show that under the same material ratio, when the solid content of PCE-4 is reduced from 60.0% to 50.0% by adding more water, the viscosity decreases significantly and the collapse retention performance is improved to a certain extent. However, due to the low solid content, the transportation cost will be too high.

[0165] In summary, the preparation method of the present invention can effectively reduce the viscosity of the product and improve the slump-retaining performance of the product while increasing the solid content of the polycarboxylic acid slump-retaining agent.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application 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 application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application 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 polycarboxylic acid collapse-preventing agent, characterized in that: include: In the presence of water, a viscosity modifier, an initiator and an optional chain transfer agent, a copolymerization reaction is carried out to synthesize a polycarboxylic acid by polymerizing comonomers including an unsaturated polyether macromonomer, an unsaturated carboxylic acid ester monomer, an unsaturated monomer I and an unsaturated esterification product to obtain a polycarboxylic acid collapse-preventing agent; wherein, The structure of the unsaturated carboxylate monomer is shown in Formula 1: In formula 1, R1 is hydrogen or methyl, and R2 is hydrogen or an alkyl group having 1 to 4 carbon atoms; The unsaturated monomer I is at least one of an unsaturated carboxylic acid, an unsaturated carboxylate and an unsaturated carboxylic anhydride; The unsaturated esterification product is the reaction product of unsaturated monomer II and hydroxy polycarboxylic acid; 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 unsaturated polyether 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.

3. The preparation method according to claim 1 or 2, characterized in that: The unsaturated carboxylic acid ester monomer is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate; Preferably, 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 itaconate and potassium itaconate; the unsaturated carboxylic anhydride is selected from at least one of maleic anhydride, itaconic anhydride and methacrylic anhydride.

4. The preparation method according to any one of claims 1 to 3, characterized in that The structure of the hydroxy polycarboxylic acid is shown in Formula 2: wherein L1, L2 and L3 are each independently a single bond or an alkylene group having 1 to 6 carbon atoms, and R is hydrogen or a carboxyl group; Preferably, the hydroxypolycarboxylic acid is citric acid and / or malic acid; 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 temperature of the esterification reaction is 80-130°C, and the reaction time is 1-6h; Preferably, the catalyst is selected from at least one of benzenesulfonic acid, p-toluenesulfonic acid, ethylsulfonic acid and concentrated sulfuric acid; Preferably, the polymerization inhibitor is hydroquinone and / or phenothiazine.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Relative to 100 parts by weight of the unsaturated polyether macromonomer, the amount of the unsaturated esterification product is 1 to 8 parts by weight, the amount of the unsaturated monomer I is 3 to 12 parts by weight, and the amount of the unsaturated carboxylic acid ester monomer is 15 to 40 parts by weight.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The viscosity modifier is selected from at least one of ferric citrate, ferric sulfate and potassium aluminum sulfate; Preferably, the mass amount of the viscosity modifier is 0.1% to 2% of the total mass of the comonomer.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The polymerization reaction temperature is 5 to 90° C., and the reaction time is 1 to 8 hours; Preferably, the amount of water used is such that the solid content of the prepared polycarboxylic acid collapse-preventing agent is not less than 55%, more preferably not less than 60%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The initiator is 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 reductant is 1:(0.2-2); Preferably, the mass amount of the initiator is 0.1% to 1% of the total mass of the comonomer; Preferably, the chain transfer agent is selected from at least one of mercaptopropionic acid, thioglycolic acid, mercaptoethanol, sodium formate and sodium hypophosphite; Preferably, the mass amount of the chain transfer agent is 0.1% to 2% of the total mass of the comonomer; Preferably, the preparation method comprises the following steps: (1) uniformly mixing the unsaturated polyether macromonomer, the unsaturated esterification product, the viscosity modifier, part of the initiator and water, and dropwise adding thereto a mixed aqueous solution of the unsaturated monomer I and the unsaturated carboxylic acid ester monomer, an aqueous solution of the remaining initiator and an aqueous solution of the molecular weight modifier; or The unsaturated polyether macromonomer, unsaturated esterification product, viscosity modifier, molecular weight modifier, part of initiator and water are uniformly mixed, and a mixed aqueous solution of unsaturated monomer I and unsaturated carboxylic acid ester monomer and an 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, the temperature is kept at 10-60°C to continue the reaction for 0.5-1 hour.

9. The polycarboxylic acid collapse-preventing agent is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the polycarboxylic acid collapse-preventing agent according to claim 9 in building materials.

Images