Viscosity reduction type polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention belongs to the field of additives, and provides a viscosity reduction type polycarboxylate superplasticizer as well as a preparation method and application thereof. The method for preparing the viscosity-reducing polycarboxylic acid water reducer comprises the following steps: carrying out free radical polymerization reaction on comonomers including a viscosity-reducing macromonomer, an ether macromonomer I, a polyester phosphate monomer, an unsaturated monomer I and an unsaturated monomer II in water, and neutralizing with alkali to obtain the viscosity-reducing polycarboxylic acid water reducer. The polycarboxylate superplasticizer prepared by the method disclosed by the invention has rapid dispersing capacity, and not only can effectively improve the flowability of a concrete mixture, but also can improve the workability of concrete.

Description

Technical Field

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

[0002] With the rapid economic development and continuous improvement of technical level, the performance requirements of building structures for concrete are becoming increasingly strict, especially in terms of strength and durability. To improve the strength of concrete, reducing the water-binder ratio is one of the main means. High-strength concrete is C50 - C80 grade concrete prepared with cement, sand, stone, water-reducing agents and other admixtures, and mineral admixtures such as fly ash, ultrafine slag, and silica fume. Among them, the water-reducing agent improves the dispersibility of cement particles through a dispersion effect, reduces the unit water consumption, and improves the fluidity of the concrete mixture. However, due to the large amount of binder used in high-strength concrete, the viscosity of the concrete is high and the dispersibility is poor. Usually, it takes a long time of stirring to reach a uniform state, and the pumping is difficult due to the high viscosity, which limits its wide application in engineering.

[0003] Therefore, there is an urgent need to develop a viscosity-reducing mother liquor with rapid dispersion ability, which will greatly shorten the stirring time and improve the construction performance of high-strength concrete. Summary of the Invention

[0004] The purpose of the present invention is to provide a viscosity-reducing polycarboxylate water reducer, a preparation method thereof, and an application thereof. The viscosity-reducing polycarboxylate water reducer prepared by the present invention has rapid dispersion ability, and can not only effectively improve the fluidity of the concrete mixture, but also improve the workability of the concrete.

[0005] In a first aspect, the present invention provides a method for preparing a polycarboxylate water reducer, the method comprising: subjecting copolymerizable monomers including a viscosity-reducing macromonomer, an ether macromonomer I, a multi-ester phosphate monomer, an unsaturated monomer I, and an unsaturated monomer II to a free radical polymerization reaction in water, and then neutralizing with an alkali to obtain the viscosity-reducing polycarboxylate water reducer; wherein the unsaturated monomer I is at least one of acrylic acid, maleic anhydride, and itaconic acid, and the unsaturated monomer II is methacrylic acid; the viscosity-reducing macromonomer has the structure shown in Formula 1:

[0006]

[0007] wherein, R1 represents -(CH2) x -, x is an integer from 1 to 4, n1 is an integer from 8 to 40, L is a single bond or an alkylene group with 1 to 4 carbon atoms, and R is a cycloalkylene group with 3 to 8 carbon atoms.

[0008] In the method of the present invention, through the polymerization reaction of the comonomer in solvent water, after the formed polycarboxylic acid is neutralized with alkali, the prepared water reducer can effectively reduce the viscosity of concrete and improve its dispersion ability. Specifically, on the one hand, the segment provided by the viscosity-reducing macromonomer having a naphthenic structure (R) in the polycarboxylic acid can reduce the surface tension and enhance the lubrication effect between cement particles. And under the alkaline conditions provided by the concrete, it can continuously hydrolyze and release naphthenic hydroxy acids, resulting in good viscosity reduction effect over time for the concrete. On the other hand, the ether macromonomer II with a long side chain can improve the viscosity reduction effect under the condition of maintaining the water reduction rate. Moreover, the phosphate group provided by the multi-ester phosphate monomer has strong adsorption on the surface of cement particles, and can also form a phosphate thin layer on the cement surface to inhibit the entry of water molecules and hinder the progress of cement hydration, increasing the content of free water, thereby reducing the viscosity of the concrete paste. And this phosphate monomer can continuously hydrolyze and release carboxyl groups, hydroxyl groups and phosphate groups during the hydration process, and can combine with the free water of the cement paste through hydrogen bonds to enhance the fullness of the paste and improve the workability and workability over time of the concrete. In addition, introducing acrylic acid or anhydride to participate in the copolymerization with methacrylic acid can increase the rigidity of the main chain of the polycarboxylic acid structure, make the water reducer adsorbed on the cement particle structure more stretched, and promote the more rapid dispersion of the concrete.

[0009] In some embodiments of the present invention, the mass ratio of the viscosity-reducing macromonomer, ether macromonomer I, multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II is 100∶(80 - 100)∶(1 - 5)∶(15 - 25)∶(1 - 5).

[0010] In some embodiments of the present invention, the ether macromonomer I is selected from ethylene glycol mono vinyl polyoxyethylene ether and / or 4-hydroxybutyl vinyl polyoxyethylene ether.

[0011] In some embodiments of the present invention, the hydroxy naphthenic carboxylic acid has the structure shown in Formula 2:

[0012]

[0013] Among them, the definitions of L and R are the same as those in Formula 1.

[0014] Furthermore, the hydroxy naphthenic carboxylic acid is selected from at least one of 3-(hydroxymethyl)cyclobutane carboxylic acid, cis-4-(hydroxymethyl)cyclohexanecarboxylic acid, 4-hydroxycyclohexanecarboxylic acid, 1-hydroxycyclopropane carboxylic acid, (1R,3R)3-hydroxycyclopentane carboxylic acid and 2-hydroxycyclopropane carboxylic acid.

[0015] In some embodiments of the present invention, the structure of the multi-ester phosphate monomer is as shown in Formula 3:

[0016]

[0017] Among them, R2 and R3 each independently represent an alkylene group having 1 to 4 carbon atoms.

[0018] In some embodiments of the present invention, the radical polymerization reaction is carried out in the presence of an initiator, a chain transfer agent and a second catalyst, and the second catalyst is ferrous sulfate.

[0019] In some embodiments of the present invention, the initiator is a redox initiator.

[0020] In some embodiments of the present invention, the method comprises the following steps:

[0021] S1: Mix the viscosity-reducing macromonomer, ether macromonomer I, second catalyst, oxidant and water evenly, and then dropwise add the first reaction solution and the second reaction solution thereto. The dropping time is 40 to 80 min, and the temperature during the reaction process is controlled to be 10 to 40 °C. Among them, the first reaction solution is a mixed aqueous solution of the reducing agent and the chain transfer agent, and the second reaction solution is a mixed monomer or its aqueous solution composed of the multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II;

[0022] S2: After the dropping is completed, continue the reaction for 1 to 2 h;

[0023] S3: Add an alkali to the product obtained in step S2 to adjust the pH to 6 to 8.

[0024] In a second aspect, the present invention provides a viscosity-reducing polycarboxylate water reducer prepared by the method described in the first aspect of the present invention. The polycarboxylate water reducer prepared by the method of the present invention is environmentally friendly in production and can also effectively reduce the viscosity of concrete and improve the workability of concrete.

[0025] In a third aspect, the present invention provides the application of the viscosity-reducing polycarboxylate water reducer described in the second aspect of the present invention in building materials.

[0026] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Detailed Description of the Invention

[0027] The embodiments of the present invention will be 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 a limitation of the present invention.

[0028] The "scope" disclosed by the present invention is defined in the form of a lower limit and / or an upper limit. A given scope is defined by selecting a lower limit and / or an upper limit. The scope defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope not explicitly recorded, and any lower limit can be combined with other lower limits to form a scope not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a scope not explicitly recorded. In addition, each separately disclosed point or single value itself can be used as a lower limit or an upper limit and combined with any other point or single value or combined with other lower limits or upper limits to form a scope not explicitly recorded.

[0029] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present invention.

[0030] In the present invention, expressions such as "first", "second", "monomer I", "monomer II", etc. are only for the purpose of description and explanation, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0031] In a first aspect, the present invention provides a method for preparing a viscosity-reducing polycarboxylate water reducer, the method comprising: subjecting copolymerizable monomers including a viscosity-reducing macromonomer, an ether macromonomer I, a poly-ester phosphate monomer, an unsaturated monomer I and an unsaturated monomer II to free radical polymerization in water to form a polycarboxylic acid, and then neutralizing with an alkali to obtain the viscosity-reducing polycarboxylate water reducer.

[0032] In the present invention, the viscosity-reducing macromonomer has the structure shown in Formula 1:

[0033]

[0034] Wherein, R1 represents -(CH2) x -, x is an integer from 1 to 4, specifically can be 1, 2, 3 or 4, preferably 2 or 4; n1 represents the degree of polymerization, specifically an integer from 8 to 40, preferably an integer from 10 to 30, such as 10, 12, 15, 20, 22, 24, 25, 26, 28 or 30; L is a single bond or an alkylene group with 1 to 4 carbon atoms, and R is a cycloalkylene group with 3 to 8 carbon atoms. As some specific examples, L can be a single bond, methylene (-CH2-), ethylene (-CH2CH2-), n-propylene (-CH2CH2CH2-), etc., and R can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc.

[0035] In some embodiments, the viscosity-reducing macromonomer is prepared by an esterification reaction of an ether macromonomer II and a hydroxycycloalkanecarboxylic acid, and the structure of the hydroxycycloalkanecarboxylic acid is shown in Formula 2:

[0036]

[0037] In Formula 2, L and R are defined the same as in Formula 1.

[0038] In some embodiments, the molar ratio of the amount of the ether macromonomer II to the hydroxycycloalkanecarboxylic acid may be (1.05 - 1):1.

[0039] It can be understood that a single bond represents a direct connection between the two groups it is associated with. For example, when L is a single bond, the structure of Formula 2 is as follows

[0040]

[0041] Preferably, the hydroxycycloalkanecarboxylic acid is selected from at least one of 3-(hydroxymethyl)cyclobutanecarboxylic acid, cis-4-(hydroxymethyl)cyclohexanecarboxylic acid, 4-hydroxycyclohexanecarboxylic acid (including trans-4-hydroxycyclohexanecarboxylic acid and / or cis-4-hydroxycyclohexanecarboxylic acid), 1-hydroxycyclopropanecarboxylic acid, (1R,3R)3-hydroxycyclopentanecarboxylic acid, and 2-hydroxycyclopropanecarboxylic acid.

[0042] In the present invention, the structure of the ether macromonomer II may be

[0043]

[0044] In Formula a, R1 and n1 are defined the same as in Formula 1.

[0045] In some embodiments, the average molecular weight of the ether macromonomer II may be 500 - 1400. The ether macromonomer II may be ethylene glycol mono vinyl polyoxyethylene ether (EPEG) and / or 4-hydroxybutyl vinyl polyoxyethylene ether (VPEG), preferably EPEG. Specific examples of the ether macromonomer II may include, but are not limited to, EPEG-600, EPEG-800, EPEG-1000, EPEG-1200, VPEG-1300, etc.

[0046] As some specific embodiments, the viscosity-reducing macromonomer is prepared by the following method: The ether macromonomer II and the hydroxycycloalkanecarboxylic acid are subjected to an esterification reaction in the presence of a first catalyst and an optional first inhibitor. The temperature of the esterification reaction may be 80 - 130 °C, such as 90 °C, 95 °C, 100 °C, 110 °C, etc., and the reaction time may be 1 - 6 h, such as 2 h, 3 h, or 5 h.

[0047] In the present invention, the first catalyst may be selected from various compounds that can improve the reaction efficiency, such as at least one of concentrated sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, strongly acidic cation exchange resin, Lewis acid, etc., and is preferably selected from one or more of concentrated sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid. The dosage of the first catalyst is preferably 0.1% to 3% of the mass of the ether macromonomer II, such as 0.2%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, 1.8%, etc. The first inhibitor may be various existing compounds that can inhibit the polymerization reaction, including but not limited to one or more selected from the following types of inhibitors: phenolic inhibitors, ether inhibitors, quinone inhibitors, and aromatic amine inhibitors. Among them, specific examples of phenolic inhibitors include but are not limited to hydroquinone, p-tert-butylcatechol, pyrogallol, 2,6-di-tert-butyl-p-cresol, 4,4-dihydroxybiphenyl, and bisphenol A. Specific examples of the ether inhibitor include but are not limited to methoxyphenol. Specific examples of the quinone inhibitor include but are not limited to benzoquinone, tetrachlorobenzoquinone, naphthoquinone, and anthraquinone. Examples of the aromatic amine inhibitor include phenothiazine, p-phenylenediamine, p-toluidine, diphenylamine, methylaniline, benzidine, β-naphthylamine, N-nitrosodiphenylamine, etc. The dosage of the first inhibitor may be 0 to 1% of the mass of the ether macromonomer II, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc.

[0048] In the present invention, the structure of the ether macromonomer I may be:

[0049]

[0050] Among them, R 1 represents -(CH2) y -, y is an integer from 1 to 4, specifically can be 1, 2, 3, or 4, preferably 2 or 4; n 1 represents the degree of polymerization, specifically an integer from 30 to 100, such as 30, 35, 40, 45, 50, 60, 65, 66, 70, 90, etc.

[0051] Preferably, the ether macromonomer I is selected from ethylene glycol mono vinyl polyoxyethylene ether (EPEG) and / or 4-hydroxybutyl vinyl polyoxyethylene ether (VPEG).

[0052] In some embodiments, the average molecular weight of the ether macromonomer I may be 1500 to 5000, preferably 2000 to 3000. As some specific examples, the ether macromonomer I may be EPEG-2400, EPEG-3000, VPEG-2400, VPEG-3000, etc.

[0053] In the present invention, the ether macromonomer I and the ether macromonomer II can be prepared by methods well-known in the art or obtained through commercial purchase. For example, but not limited to, a series of ether macromonomers from Ouke Chemical Co., Ltd. and Fujian Zhongshan Chemical Co., Ltd.

[0054] In some embodiments, the structure of the multi-ester phosphate monomer is shown in Formula 3:

[0055]

[0056] Wherein, R2 and R3 are the same or different and each independently represents an alkylene group having 1 to 4 carbon atoms. Preferably, R2 and R3 each independently represent a methylene group, an ethylene group or a n-propylene group.

[0057] As some specific examples, the multi-ester phosphate monomer is selected from at least one of the following compounds C1 to C3:

[0058]

[0059] In the present invention, the multi-ester phosphate monomer can be obtained through commercial purchase or prepared by methods well-known in the art. For example, an unsaturated acid shown in Formula 3-a and a hydroxyalkyl phosphate shown in Formula 3-b (wherein the definitions of R2 and R3 are as shown in Formula 3) are esterified at 90 to 120 °C for 2 to 8 h in the presence of an acid catalyst and a second inhibitor:

[0060]

[0061] The acid catalyst can be, for example, one or more of concentrated sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid. The mass dosage of the acid catalyst accounts for 0.2 to 2% of the total amount of the reactants (the sum of the masses of the unsaturated acid and the hydroxyalkyl phosphate), such as 0.2%, 0.4%, 0.5%, 0.7%, 0.8%, 1.0%, 1.2%, 1.5%, etc. The second inhibitor can be selected from, for example, one or more of phenothiazine, p-phenylenediamine, and benzoquinone. The mass dosage of the second inhibitor accounts for 0.05 to 2% of the total amount of the reactants (the sum of the masses of the unsaturated acid and the hydroxyalkyl phosphate), such as 0.05%, 0.08%, 0.10%, 0.15%, 0.2%, 0.5%, 1%, etc.

[0062] As a specific example, the unsaturated acid is β-(acryloyloxy)propionic acid and the hydroxyalkyl phosphate is 2-hydroxyethyl phosphate.

[0063] In the present invention, the unsaturated monomer I is selected from at least one of acrylic acid (AA), maleic anhydride (MA), and itaconic acid (IA).

[0064] In the present invention, the unsaturated monomer II is methacrylic acid (MAA).

[0065] In the present invention, as comonomers, the viscosity-reducing macromonomer, ether macromonomer I, multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II undergo free radical polymerization to form a copolymerization product (polycarboxylic acid). According to some embodiments, the mass ratio of the viscosity-reducing macromonomer, ether macromonomer I, multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II can be 100∶(80 - 100)∶(1 - 5)∶(15 - 25)∶(1 - 5), such as 100∶100∶3∶23∶3, 100∶95∶4∶25∶3, 100∶85∶5∶25∶3, 100∶100∶3∶25∶3, 100∶95∶5∶25∶2, 100∶90∶5∶20∶4, etc.

[0066] In the present invention, the temperature of the copolymerization reaction can be 5 - 40°C, such as 5°C, 10°C, 15°C, 18°C, 20°C, 30°C, 32°C, 35°C, 40°C, etc. The temperature of the copolymerization reaction can also be controlled within any temperature range within the above range, such as controlled between 5 - 15°C, or controlled between 20 - 35°C, etc.

[0067] In the present invention, the time of the copolymerization reaction can be determined according to the conversion degree of the comonomers, and generally can be 1 - 6 h, such as 1 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, etc.

[0068] In the present invention, unreacted monomers, etc. can be neutralized by adding an alkali. As some embodiments, the pH of the reaction system obtained from the polymerization reaction can be adjusted to 6 - 8 by adding an alkali, and more preferably the system is adjusted to be neutral. The alkali can include but is not limited to sodium hydroxide, and preferably the alkali is added in the form of an alkali solution (such as a sodium hydroxide solution with a concentration of 32 wt%).

[0069] In some embodiments, the free radical polymerization reaction is carried out in the presence of an initiator, a chain transfer agent and a second catalyst, and the second catalyst is ferrous sulfate.

[0070] In the present invention, the mass dosage of the second catalyst can be 0.01 - 3% of the total mass of the comonomers (i.e., the total amount of the viscosity-reducing macromonomer, ether macromonomer I, multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II), preferably 0.05% - 2%, such as 0.2%, 0.3%, 0.4%, 0.45%, 0.5%, 0.7%, 0.9%, 1%, 1.1%, 1.2%, 1.6%, etc.

[0071] In the present invention, the initiator can be selected from various water-soluble free radical initiators, preferably redox initiators. The redox initiator includes an oxidizing agent and a reducing agent.

[0072] As some preferred examples, the oxidizing agent is selected from at least one of hydrogen peroxide, ammonium persulfate and sodium persulfate, and the reducing agent is selected from ascorbic acid and / or sodium formaldehyde sulfoxylate.

[0073] In some embodiments, in the redox initiator, the mass ratio of the oxidizing agent to the reducing agent can be 1:(0.2 - 1.5), such as 1:0.2, 1:0.4, 1:0.5, 1:1, etc.

[0074] In the present invention, the dosage of the initiator can be selected according to the total amount of the comonomers. According to some embodiments, the mass dosage of the initiator is 0.1% - 2% of the total mass of the comonomers, such as 0.6%, 0.7%, 0.9%, 1.0%, 1.1%, 1.5%, 1.7%, 1.8%, etc.

[0075] In the present invention, the chain transfer agent can be selected from water-soluble chain transfer agents commonly used in free radical polymerization. According to some embodiments, the chain transfer agent is selected from one or more of mercaptoethanol, mercaptopropionic acid and mercaptoacetic acid.

[0076] In the present invention, the dosage of the chain transfer agent can be selected according to the total amount of the comonomers. According to some embodiments, the mass dosage of the chain transfer agent is 0.1% - 1% of the total mass of the comonomers, such as 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, etc.

[0077] In order to improve the effect of the polymerization reaction, according to some preferred embodiments, the method for preparing the viscosity-reducing polycarboxylate water reducer includes the following steps:

[0078] S1: Mix the functional macromonomer, ether macromonomer I, the second catalyst, the oxidizing agent and water uniformly, and dropwise add the first reaction solution and the second reaction solution thereto. The dropping time is 40 - 80 min, and the temperature of the reaction process is controlled at 10 - 40 °C;

[0079] S2: After the dropping is completed, continue the reaction for 1 - 2 h;

[0080] S3: Add an alkali to the product obtained in step S2 to adjust the pH to 6 - 8.

[0081] In step S1, the first reaction solution is an aqueous solution mixture of the reducing agent and the chain transfer agent, and the second reaction solution is a monomer mixture composed of a multi-ester phosphate monomer, unsaturated monomer I and unsaturated monomer II or an aqueous solution of the monomer mixture. Before or at the initial stage of dropping the reaction solution, it is preferred to control the temperature of the system at 5-20 °C.

[0082] In step S2, the reaction after the dropping is completed can further increase the conversion degree of the reactants.

[0083] In the present invention, the amount of water used can be selected according to the solid content of the viscosity-reducing polycarboxylate water reducer required. According to some embodiments, the amount of water used is such that the solid content of the viscosity-reducing polycarboxylate water reducer is not less than 45%, preferably 45%-60%.

[0084] In a second aspect, the present invention provides a viscosity-reducing polycarboxylate water reducer prepared by the preparation method described in the first aspect of the present invention.

[0085] The viscosity-reducing polycarboxylate water reducer of the present invention can effectively improve the fluidity of concrete as an admixture mother liquor, and can improve the workability while maintaining the water reduction rate of the concrete.

[0086] The following describes the embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. Unless otherwise specified, the parts described below all refer to parts by weight.

[0087] Synthesis Example 1

[0088] Add EPEG-1200 (the structure is shown in formula a, x = 2, n1 = 25), 1-hydroxycyclopropanecarboxylic acid, benzenesulfonic acid and hydroquinone into a reactor equipped with a condensation device. The molar ratio of EPEG-1200 to 1-hydroxycyclopropanecarboxylic acid is 1.05:1. The amount of benzenesulfonic acid used is 1.2% of the mass of EPEG-1200, and the amount of hydroquinone used is 0.3% of the mass of EPEG-1200. React at a constant temperature of 100 °C for 6 h under nitrogen protection. After the reaction is completed, cool naturally to room temperature to obtain a viscosity-reducing macromonomer, denoted as monomer A1, and its structure is shown in formula 1-1:

[0089]

[0090] Synthesis Examples 2-4

[0091] Prepare the viscosity-reducing macromonomer according to the method of Synthesis Example 1. The difference is that 1-hydroxycyclopropanecarboxylic acid is replaced by 2-hydroxycyclopropanecarboxylic acid, 3-(hydroxymethyl)cyclobutanecarboxylic acid, and trans-4-hydroxycyclohexanecarboxylic acid respectively. The prepared viscosity-reducing macromonomers are denoted as monomer A2, A3 and A4 respectively, and the structures of A2-A4 are shown below:

[0092]

[0093] Synthesis Example 5

[0094] 100 parts of reactants (β-(acryloyloxy)propionic acid and 2-hydroxyethyl phosphoric acid, molar ratio 1.1:1), 1 part of concentrated sulfuric acid and 0.3 part of phenothiazine were added to a reactor and stirred. Under nitrogen protection, it was heated to 110 °C and reacted at a constant temperature for 5 h. After the reaction ended, it was naturally cooled to obtain a polyester-based phosphate monomer (i.e., Compound C2):

[0095]

[0096] In the following examples and comparative examples, the mass concentration of hydrogen peroxide in hydrogen peroxide solution was 27.5%.

[0097] Example 1

[0098] 100 parts of viscosity-reducing macromonomer A1 and 100 parts of EPEG-3000 were placed in a reactor, 180 parts of water was added, the stirrer and temperature control device were turned on. After the materials were dissolved evenly, a ferrous sulfate solution (1 part of ferrous sulfate, 10 parts of water) and a hydrogen peroxide solution (2.0 parts of hydrogen peroxide, 5 parts of water) were added. After stirring for 5 min, the starting temperature was controlled at 5 - 20 °C, and a mixed solution of ascorbic acid and mercaptoethanol (0.5 part of ascorbic acid, 1.2 parts of mercaptoethanol, 8 parts of water), an aqueous mixed solution of Compound C2, acrylic acid and methacrylic acid (3 parts of Compound C2, 23 parts of acrylic acid, 3 parts of methacrylic acid, 40 parts of water) were respectively added dropwise. During the reaction process, the temperature was controlled at 25 - 35 °C, the dropping time was 60 min, and the reaction continued for 1.5 h. Finally, sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate water reducer, denoted as VPCE-1.

[0099] Example 2

[0100] 100 parts of viscosity-reducing macromonomer A2 and 95 parts of EPEG-3000 were placed in a reactor, 175 parts of water was added, the stirrer and temperature control device were turned on. After the materials were dissolved evenly, a ferrous sulfate solution (1 part of ferrous sulfate, 10 parts of water) and a hydrogen peroxide solution (2.2 parts of hydrogen peroxide, 5 parts of water) were added. After stirring for 5 min, the starting temperature was controlled at 5 - 20 °C, and a mixed solution of ascorbic acid and mercaptoethanol (0.5 part of ascorbic acid, 1.2 parts of mercaptoethanol, 8 parts of water), an aqueous mixed solution of Compound C2, acrylic acid and methacrylic acid (5 parts of Compound C2, 23 parts of acrylic acid, 5 parts of methacrylic acid, 40 parts of water) were respectively added dropwise. During the reaction process, the temperature was controlled at 20 - 35 °C, the dropping time was 60 min. After the dropping ended, the reaction continued for 1.5 h. Finally, sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate water reducer, denoted as VPCE-2.

[0101] Example 3

[0102] Put 100 parts of viscosity-reducing macromonomer A3 and 90 parts of EPEG-3000 into a reactor, add 170 parts of water, turn on the stirrer and temperature control device. After the materials are dissolved evenly, add ferrous sulfate solution (1 part of ferrous sulfate and 10 parts of water) and hydrogen peroxide solution (2.0 parts of hydrogen peroxide and 5 parts of water). After stirring for 5 min, control the initial temperature to be 5 - 20 °C, and respectively dropwise add a mixed solution of ascorbic acid and mercaptoethanol (0.6 part of ascorbic acid, 1.3 parts of mercaptoacetic acid, and 8 parts of water), an aqueous mixed solution of compound C2, acrylic acid, and methacrylic acid (3 parts of compound C2, 25 parts of acrylic acid, 3 parts of methacrylic acid, and 40 parts of water). During the reaction process, control the temperature to be 20 - 35 °C, the dropping time to be 80 min. After the dropping is completed, continue the reaction for 2 h. Finally, add sodium hydroxide to adjust the pH to neutral to obtain a polycarboxylate water reducer, denoted as VPCE-3.

[0103] Example 4

[0104] Put 100 parts of viscosity-reducing macromonomer A4 and 100 parts of EPEG-3000 into a reactor, add 180 parts of water, turn on the stirrer and temperature control device. After the materials are dissolved evenly, add ferrous sulfate solution (1 part of ferrous sulfate and 10 parts of water) and hydrogen peroxide solution (2.0 parts of hydrogen peroxide and 5 parts of water). Stir for 5 min, control the initial temperature to be 5 - 20 °C, and respectively dropwise add a mixed solution of ascorbic acid and mercaptoethanol (0.5 part of ascorbic acid, 1.2 parts of mercaptoethanol, and 8 parts of water), an aqueous mixed solution of compound C2, acrylic acid, and methacrylic acid (3 parts of compound C2, 20 parts of acrylic acid, 3 parts of methacrylic acid, and 35 parts of water). During the reaction process, control the temperature to be 30 - 35 °C, the dropping time to be 60 min. After the dropping is completed, continue the reaction for 1.5 h. Finally, add sodium hydroxide to adjust the pH to neutral to obtain a polycarboxylate water reducer, denoted as VPCE-4.

[0105] Example 5

[0106] Put 100 parts of viscosity-reducing macromonomer A4 and 85 parts of EPEG-3000 into a reactor, add 180 parts of water, turn on the stirrer and temperature control device. After the materials are dissolved evenly, add ferrous sulfate solution (1 part of ferrous sulfate, 10 parts of water) and hydrogen peroxide solution (2.2 parts of hydrogen peroxide, 5 parts of water), stir for 5 min, control the starting temperature at 5 - 20 °C, and respectively dropwise add a mixed solution of ascorbic acid and mercaptoethanol (0.7 part of ascorbic acid, 1.2 parts of mercaptoethanol, 8 parts of water), and a mixed aqueous solution of compound C2, acrylic acid, maleic anhydride and methacrylic acid (4 parts of compound C2, 20 parts of acrylic acid, 5 parts of maleic anhydride, 4 parts of methacrylic acid, 35 parts of water). During the reaction process, control the temperature at 20 - 35 °C, the dropping time is 60 min. After the dropping is completed, continue the reaction for 2 h. Finally, add sodium hydroxide to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as VPCE-5.

[0107] Comparative Example 1

[0108] Prepare the polycarboxylate superplasticizer according to the method of Example 1. The difference is that viscosity-reducing macromonomer A1 is not used, and the dosage of EPEG-3000 is adjusted to 200 parts. The prepared polycarboxylate superplasticizer is denoted as VPCE-d1.

[0109] Comparative Example 2

[0110] Prepare the polycarboxylate superplasticizer according to the method of Example 1. The difference is that EPEG-3000 is not used, and the dosage of viscosity-reducing macromonomer A1 is adjusted to 200 parts. The prepared polycarboxylate superplasticizer is denoted as VPCE-d2.

[0111] Comparative Example 3

[0112] Prepare the polycarboxylate superplasticizer according to the method of Example 1. The difference is that compound C2 and methacrylic acid are not used, and the dosage of EPEG-3000 is adjusted to 106 parts. The prepared polycarboxylate superplasticizer is denoted as VPCE-d3.

[0113] Comparative Example 4

[0114] Prepare the polycarboxylate superplasticizer according to the method of Example 1. The difference is that viscosity-reducing macromonomer A1, compound C2, and methacrylic acid are not used, and the dosage of EPEG-3000 is adjusted to 200 parts. The prepared polycarboxylate superplasticizer is denoted as VPCE-d4.

[0115] Test Example

[0116] The test example is used to illustrate the application performance of the polycarboxylate superplasticizers VPCE-1 to VPCE-5 and VPCE-d1 to VPCE-d4 prepared in the above examples and comparative examples as admixtures in concrete.

[0117] Using Runfeng Cement and adjusting the dosage of water reducer, when the slump flow of the concrete is (650±10) mm, according to GB8076-2008 "Concrete Admixtures", test the performance of the water reducer on the initial and 2-hour slump flow of the concrete, the emptying time of the inverted slump cone, and the compressive strength at each age. In order to test the dispersion rate simultaneously, test the initial slump flow and the emptying time when the concrete is stirred for 2 minutes.

[0118] The concrete mix ratio is as follows: cement 380 kg / m 3 、fly ash 70 kg / m 3 、ground granulated blast-furnace slag 70 kg / m 3 、manufactured sand 759 kg / m 3 、small stones (particle size between 5 and 10 mm) 201 kg / m 3 、big stones (particle size of 10 to 15 mm) 805 kg / m 3 、water 145 kg / m 3 。

[0119] Table 1

[0120]

[0121]

[0122] Combining the data in Table 1 and comparing the polycarboxylate water reducers of Examples 1 to 5 with those of Comparative Examples 1 to 4, it can be seen that when the polycarboxylate water reducers prepared by the methods of Examples 1 to 5 are applied to concrete, the difference in slump flow loss after 2 hours is small, indicating a small impact on fluidity. The emptying time at the initial stage and after 2 hours is not higher than 15 s, indicating low viscosity of the concrete, and it does not affect the compressive strength either. It can be seen that copolymerizing with a viscosity-reducing macromonomer, EPEG, a multi-ester phosphate monomer, and an acrylic monomer can improve the flow rate simultaneously, and there are also significant improvements in the softness of the slurry and the slurry wrapping property.

[0123] Comparing Example 1 with Comparative Example 1, it can be seen that on the basis of EPEG-3000, multi-ester phosphate monomer, AA, and MAA as monomers, further introducing the viscosity-reducing macromonomer A1, the prepared polycarboxylate water reducer can not only improve the flow rate and wrapping property, but also has a good effect on improving the viscosity-reducing effect.

[0124] Comparing Example 1 with Comparative Example 2, it can be seen that when EPEG-3000 macromonomer is not used and only copolymerized with the viscosity-reducing macromonomer A1, multi-ester phosphate monomer, AA, and MAA, the prepared polycarboxylate water reducer has an effect of improving the flow rate, but the water reduction rate is low.

[0125] Comparing Example 1 with Comparative Example 3, it can be seen that when the multi-ester phosphate monomer and MAA are not used, and the viscosity-reducing mother liquor prepared by copolymerizing only the viscosity-reducing macromonomer A1, EPEG-3000 macromonomer and AA has improved flow velocity, but the workability is poor and the dispersion velocity is also poor.

[0126] In addition, for the water reducer prepared by copolymerizing only the EPEG-3000 macromonomer and AA in Comparative Example 4, when the concrete is stirred for 2 minutes, the evacuation time is not less than 30 s, indicating that its fluidity is poor and it cannot be dispersed evenly in a short time. Moreover, due to the slow release, the phenomenon of increasing slump over time occurs.

[0127] In summary, the polycarboxylate water reducer prepared by the method of the present invention can be used as the viscosity-reducing mother liquor for high-strength concrete, and has obvious effects in improving the workability and flow velocity of concrete, and has no negative impact on the strength.

[0128] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; 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 covered by the scope of the claims and the description of the present invention. In particular, as long as there is no structural conflict, the 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 falling within the scope of the claims.

Claims

1. A method for preparing a viscosity-reducing polycarboxylate water-reducing agent, characterized in that: The method comprises: subjecting comonomers including a viscosity-reducing macromonomer, an ether macromonomer I, a polyester phosphate monomer, an unsaturated monomer I and an unsaturated monomer II to a free radical polymerization reaction in water, and then neutralizing with a base to obtain the viscosity-reducing polycarboxylic acid water-reducing agent; wherein the unsaturated monomer I is at least one of acrylic acid, maleic anhydride and itaconic acid, and the unsaturated monomer II is methacrylic acid; The viscosity-reducing macromonomer has a structure shown in Formula 1: Wherein, R1 represents -(CH2) x -, x is an integer of 1 to 4, n1 is an integer of 8 to 40, L is a single bond or an alkylene group having 1 to 4 carbon atoms, and R is a cycloalkylene group having 3 to 8 carbon atoms.

2. The method according to claim 1, characterized in that The mass ratio of the viscosity-reducing macromonomer, the ether macromonomer I, the polyester phosphate monomer, the unsaturated monomer I and the unsaturated monomer II is 100:(80-100):(1-5):(15-25):(1-5); Preferably, the temperature of the free radical polymerization reaction is 5 to 40° C., and the reaction time is 1 to 8 hours.

3. The method according to claim 1 or 2, characterized in that: The ether macromonomer I is ethylene glycol monovinyl polyoxyethylene ether and / or 4-hydroxybutyl vinyl polyoxyethylene ether; Preferably, the average molecular weight of the ether macromonomer I is 2000-3000.

4. The method according to any one of claims 1 to 3, characterized in that: The viscosity-reducing macromonomer is prepared by esterification reaction between an ether macromonomer II and a hydroxycycloalkanecarboxylic acid having a structure as shown in Formula 2; In Formula 2, L is a single bond or an alkylene group having 1 to 4 carbon atoms, and R is a cycloalkylene group having 3 to 8 carbon atoms; Preferably, the hydroxycycloalkanecarboxylic acid is selected from at least one of 3-(hydroxymethyl)cyclobutanecarboxylic acid, cis-4-(hydroxymethyl)cyclohexanecarboxylic acid, 4-hydroxycyclohexanecarboxylic acid, 1-hydroxycyclopropanecarboxylic acid, (1R,3R)3-hydroxycyclopentanecarboxylic acid and 2-hydroxycyclopropanecarboxylic acid; Preferably, the molar ratio of the ether macromonomer II to the hydroxycycloalkanecarboxylic acid is (1.05-1):1; Preferably, the ether macromonomer II is ethylene glycol monovinyl polyoxyethylene ether; Preferably, in Formula 1, n1 is an integer of 10 to 30.

5. The method according to claim 4, characterized in that The esterification reaction is carried out in the presence of a first catalyst and an optional first polymerization inhibitor, the temperature of the esterification reaction is 80 to 130° C., and the reaction time is 1 to 6 hours; Preferably, the first catalyst is selected from at least one of concentrated sulfuric acid, benzenesulfonic acid and p-toluenesulfonic acid, and the amount of the first catalyst used is 0.1% to 3% of the mass of the ether macromonomer II.

6. The method according to any one of claims 1 to 5, characterized in that: The structure of the multiester phosphate monomer is shown in Formula 3: Wherein, R2 and R3 each independently represent an alkylene group having 1 to 4 carbon atoms; Preferably, R2 and R3 each independently represent a methylene group, an ethylene group or an n-propylene group.

7. The method according to any one of claims 1 to 6, characterized in that: The free radical polymerization reaction is carried out in the presence of an initiator, a chain transfer agent and a second catalyst, wherein the second catalyst is ferrous sulfate; Preferably, the mass dosage of the second catalyst is 0.05% to 2% of the total mass of the comonomer; Preferably, the initiator is a redox initiator; Preferably, the reducing agent in the redox initiator is ascorbic acid and / or sodium formaldehyde sulfoxylate, and the oxidizing agent in the redox initiator is selected from at least one of hydrogen peroxide, sodium persulfate and ammonium persulfate; Preferably, the mass amount of the initiator is 0.1% to 2% of the total mass of the comonomer; Preferably, the chain transfer agent is selected from at least one of mercaptoethanol, mercaptopropionic acid and thioglycolic acid; Preferably, the mass amount of the chain transfer agent is 0.1% to 1% of the total mass of the comonomer.

8. The method according to claim 7, characterized in that The method comprises the following steps: S1: The viscosity-reducing macromonomer, ether macromonomer I, second catalyst, oxidant and water are uniformly mixed, and the first reaction liquid and the second reaction liquid are added dropwise thereto for 40 to 80 minutes, and the temperature of the reaction process is controlled to be 10 to 40° C., wherein: The first reaction liquid is a mixed aqueous solution of the reducing agent and the chain transfer agent; The second reaction liquid is a mixed monomer consisting of the polyester phosphate monomer, unsaturated monomer I and unsaturated monomer II or an aqueous solution thereof; S2: After the addition is completed, the reaction continues for 1 to 2 hours; S3: adding a base to the product obtained in step S2 to adjust the pH to 6-8; Preferably, the amount of water used is such that the solid content of the prepared viscosity-reducing polycarboxylate water-reducing agent is not less than 45%.

9. A viscosity-reducing polycarboxylate water-reducing agent prepared by the method according to any one of claims 1 to 8.

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

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