Polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention belongs to the field of additives, and provides a polycarboxylate superplasticizer as well as a preparation method and application thereof. The preparation method of the polycarboxylate superplasticizer comprises the following steps: carrying out free radical polymerization reaction on comonomers including a functional macromonomer, an ether macromonomer I, a polyester phosphate monomer and an unsaturated monomer in water, and neutralizing with alkali to obtain the polycarboxylate superplasticizer. The prepared polycarboxylic acid water reducing agent not only can effectively improve the viscosity of a high-strength concrete mixture, but also can enable the concrete to be softer in state and better in workability.

Description

Technical Field

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

[0002] With the rapid economic development and continuous improvement of technical level, the requirements for the structure and performance of buildings are getting higher and higher, which requires concrete to have higher strength and durability. Reducing the water-binder ratio is the main way to improve the strength of concrete, but it will cause the concrete to have high viscosity, bringing great difficulties to pumping and construction, and greatly restricting the application and development of high-strength concrete.

[0003] In practical engineering applications, on the one hand, high-quality river sand or high-quality manufactured sand can be selected and the concrete mix can be optimized to reduce the viscosity, but this method has problems such as high cost, complex mix design, and construction difficulties; on the other hand, air-entraining agents can be added to improve the fluidity of concrete to reduce the viscosity, but excessive addition of air-entraining agents will significantly affect the strength of concrete. Adding a small amount of polycarboxylate water reducing agent to concrete construction can not only reduce the water consumption, but also optimize the physical and chemical properties of concrete and reduce the pore structure in concrete. However, adding water reducing agents usually affects the strength and fluidity of concrete, resulting in relatively serious slump loss. Therefore, developing a polycarboxylate water reducing agent with excellent viscosity reduction performance has become a research hotspot in the industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a polycarboxylate water reducing agent and a preparation method thereof. The polycarboxylate water reducing agent prepared by the present invention can not only effectively improve the viscosity of the high-strength concrete mixture, but also make the state of the concrete softer and the workability better.

[0005] In the first aspect, the present invention provides a preparation method of a polycarboxylate water reducing agent, and the preparation method includes: performing a free radical polymerization reaction on copolymerization monomers including a functional macromonomer, an ether macromonomer I, a multi-ester phosphate monomer, and an unsaturated monomer in water, and then neutralizing with an alkali to obtain the polycarboxylate water reducing agent; wherein, the unsaturated monomer is an unsaturated carboxylic acid and / or an unsaturated acid anhydride; the structural general formula of the functional macromonomer is as shown in Formula 1:

[0006]

[0007] wherein, R1 represents -(CH2) x -, x is an integer from 1 to 4, n 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 preparation method of the present invention, the functional macromonomer used belongs to a cycloalkyl-modified monomethyl polyether macromonomer. This monomer can reduce the surface tension of the water reducer, change the molecular conformation of the water reducer, enhance the lubrication effect between concrete particles, and continuously hydrolyze and release cycloalkyl hydroxy acids in the alkaline environment provided by the concrete, resulting in good viscosity reduction effect over time for the concrete. In addition, the structural unit provided by the polyester phosphate monomer in the water reducer can inhibit the entry of water molecules at the initial stage of cement hydration, hinder the progress of cement hydration, increase the content of free water, reduce the viscosity of the concrete paste, and this monomer has both an ester group and a phosphate group, and can continuously hydrolyze and release carboxyl groups, hydroxyl groups and phosphate groups during the hydration process of the concrete. In this way, it can combine with the free water of the cement paste through hydrogen bonds, improve the fullness of the paste, and improve the workability of the concrete.

[0009] In some embodiments of the present invention, the ether macromonomer I is isopentenyl polyoxyethylene ether and / or methyl allyl polyoxyethylene ether.

[0010] In some embodiments of the present invention, the average molecular weight of the ether macromonomer I is 2000 - 3000.

[0011] In some embodiments of the present invention, the functional macromonomer is prepared by an esterification reaction of an ether macromonomer II and a hydroxycycloalkane carboxylic acid having a structure as

[0012] shown in Formula 2;

[0013]

[0014] In Formula 2, L is a single bond or an alkylene group with 1 - 4 carbon atoms, and R is a cycloalkylene group with 3 - 8 carbon atoms.

[0015] Furthermore, the hydroxycycloalkane 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.

[0016] In some embodiments of the present invention, the structure of the polyester phosphate monomer is as shown in Formula 3:

[0017]

[0018] Among them, R2 and R3 each independently represent an alkylene group with 1 - 4 carbon atoms.

[0019] In some embodiments of the present invention, the unsaturated monomer is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride, and itaconic acid.

[0020] In some embodiments of the present invention, the mass ratio of the functional macromonomer, ether macromonomer I, multi-ester phosphate monomer and unsaturated monomer is 120∶(60 - 90)∶(1 - 5)∶(20 - 30).

[0021] In some embodiments of the present invention, the temperature of the free radical polymerization reaction is 5 - 40 °C, and the reaction time is 2 - 5 h.

[0022] In some embodiments of the present invention, the free radical polymerization reaction is carried out in the presence of an initiator and a chain transfer agent.

[0023] Furthermore, the initiator is a redox initiator.

[0024] Furthermore, the oxidant in the redox initiator is selected from at least one of hydrogen peroxide, ammonium persulfate and sodium persulfate, and the reductant is selected from ascorbic acid and / or sodium formaldehyde sulfoxylate.

[0025] In some embodiments of the present invention, the mass dosage of the initiator is 0.2% - 2% of the total mass of the comonomers.

[0026] In some embodiments of the present invention, the chain transfer agent is selected from at least one of mercaptoethanol, mercaptopropionic acid and mercaptoacetic acid.

[0027] In some embodiments of the present invention, the mass dosage of the chain transfer agent is 0.3 - 2% of the total mass of the comonomers.

[0028] In some embodiments of the present invention, the preparation method includes the following steps:

[0029] (1) Dissolve the functional macromonomer, ether macromonomer I, multi-ester phosphate monomer and oxidant in water, and respectively dropwise add an aqueous solution of a mixture of a reductant and a chain transfer agent and an aqueous solution of an unsaturated monomer thereto for reaction, control the dropping time to be 1 - 3 h, and the temperature during the reaction to be 10 - 40 °C;

[0030] (2) After the dropping is completed, continue the reaction for 1 - 2 h;

[0031] (3) Add an alkali to the product obtained in step (2) to adjust the pH to 6 - 8.

[0032] In some embodiments of the present invention, the amount of water used is such that the solid content of the prepared polycarboxylate water reducer is not less than 45%.

[0033] Second, the present invention provides a polycarboxylate water reducer prepared by the preparation method described in the first aspect of the present invention.

[0034] The polycarboxylate water reducer prepared by the method of the present invention is not only green and environmentally friendly, but also can effectively reduce the viscosity of concrete, and can effectively improve the workability and slump retention of concrete under the condition of maintaining the strength of concrete.

[0035] In a third aspect, the present invention provides the use of the polycarboxylate water reducer described in the second aspect of the present invention in building materials.

[0036] 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 Embodiments

[0037] 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.

[0038] The "range" disclosed in the present invention is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way may or may 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 range not explicitly recorded, and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually 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 range not explicitly recorded.

[0039] If there is no special description, 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.

[0040] In the present invention, expressions such as "first", "second", "monomer I", "monomer II", etc. are only for the purpose of description and explanation, and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0041] The first aspect of the present invention provides a method for preparing a polycarboxylate water reducer, including: subjecting copolymerizable monomers including a functional macromonomer, an ether macromonomer I, a multi-ester phosphate monomer, and an unsaturated monomer to a free radical polymerization reaction in water, and then neutralizing with an alkali to obtain a polycarboxylate water reducer.

[0042] In the present invention, the viscosity-reducing macromonomer has the structure shown in Formula 1:

[0043]

[0044] Among them, R1 represents -(CH2) x -, x is an integer from 1 to 4, specifically can be 1, 2, 3 or 4, preferably 1 or 2; n represents the degree of polymerization, specifically an integer from 8 to 40, preferably an integer from 10 to 30, such as 10, 12, 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 cyclopropylidene, cyclobutylidene, cyclopentylidene, cyclohexylidene, cycloheptylidene, etc.

[0045] In some embodiments, the functional 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:

[0046]

[0047] In Formula 2, the definitions of L and R are the same as those in Formula 1.

[0048] In some embodiments, the molar ratio of the ether macromonomer II to the hydroxycycloalkanecarboxylic acid can be (1.05 - 1)∶1.

[0049] It can be understood that a single bond means 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

[0050]

[0051] 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.

[0052] In the present invention, the structure of the ether macromonomer II can be

[0053]

[0054] In Formula a, the definitions of R1 and n1 are the same as those in Formula 1.

[0055] In some embodiments, the average molecular weight of the ether macromonomer II can be 500 to 1400. The ether macromonomer II can be isopentenyl polyoxyethylene ether (TPEG) and / or methallyl polyoxyethylene ether (HPEG). Specific examples of the ether macromonomer II can include, but are not limited to, TPEG-600, TPEG-1000, TPEG-1200, etc.

[0056] As some specific embodiments, the functional macromonomer is prepared by the following method: The ether macromonomer II and hydroxycycloalkane carboxylic 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 can be 80 to 130 °C, such as 90 °C, 95 °C, 100 °C, 110 °C, etc., and the reaction time can be 1 to 6 h, such as 2 h, 3 h or 5 h.

[0057] In the present invention, the first catalyst can be selected from various compounds that can improve the reaction efficiency. For example, it can be 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 can 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, aromatic amine inhibitors. Among them, specific examples of the phenolic inhibitor include, but are not limited to, hydroquinone, p-tert-butylcatechol, pyrogallol, 2,6-di-tert-butyl-p-cresol, 4,4-dihydroxybiphenyl, bisphenol A. Specific examples of the ether inhibitor include, but are not limited to, hydroxyanisole. Specific examples of the quinone inhibitor include, but are not limited to, benzoquinone, tetrachlorobenzoquinone, naphthoquinone, anthraquinone. Examples of the aromatic amine inhibitor can include phenothiazine, p-phenylenediamine, p-toluidine, diphenylamine, methylaniline, benzidine, β-naphthylamine, N-nitrosodiphenylamine, etc. The dosage of the first inhibitor can 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.

[0058] In the present invention, the structure of the polyether macromonomer I can be:

[0059]

[0060] Wherein, R 1 represents -(CH2) y -, y is an integer from 1 to 4, specifically can be 1, 2, 3 or 4, preferably 1 or 2; n1 represents the degree of polymerization, which can specifically be an integer from 40 to 100, such as 40, 45, 50, 60, 65, 66, 70, 90, etc.

[0061] Preferably, the ether macromonomer I is selected from isopentenyl polyethylene glycol ether (TPEG) and / or methallyl polyethylene glycol ether (HPEG), more preferably isopentenyl polyethylene glycol ether.

[0062] In some embodiments, the average molecular weight of the ether macromonomer I can be 1500 - 5000, preferably 2000 - 4000. As some examples, the ether macromonomer II can be HPEG - 2400, HPEG - 3000, HPEG - 4000, TPEG - 2400, TPEG - 3000, etc.

[0063] 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, the series of polyether macromonomers from Fujian Zhongshan Chemical Co., Ltd. and Oak Chemical Co., Ltd.

[0064] In some embodiments, the structure of the multi - ester - based phosphate monomer is shown in Formula 3:

[0065]

[0066] wherein, R2 and R3 each independently represent an alkylene group with 1 - 4 carbon atoms;

[0067] Preferably, R2 and R3 each independently represent methylene, ethylene or n - propylene.

[0068] As some specific examples, the multi - ester - based phosphate monomer is selected from at least one of the following compounds C1 - C3:

[0069]

[0070]

[0071] In the present invention, the multi - ester - based phosphate monomer can be obtained through commercial purchase or prepared by methods well - known in the art. For example, by esterifying an unsaturated acid shown in Formula 3 - a with a hydroxyalkyl phosphate shown in Formula 3 - b (the definitions of R2 and R3 are as shown in Formula 3) in the presence of an acid catalyst and a second inhibitor at 90 - 120 °C for 2 - 8 h:

[0072]

[0073] 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 0.2-2% of the total amount of 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, for example, selected from one or more of phenothiazine, p-phenylenediamine, and benzoquinone. The mass dosage of the second inhibitor accounts for 0.05-2% of the total amount of 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.

[0074] In the present invention, the unsaturated monomer is selected from unsaturated carboxylic acids and / or unsaturated carboxylic anhydrides. Generally, the unsaturated carboxylic acid can be selected from carboxylic acids having 3-8 carbon atoms with double bonds, and the unsaturated carboxylic anhydride can be selected from carboxylic anhydrides having 3-10 carbon atoms with double bonds, for example.

[0075] In some embodiments, the unsaturated monomer is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride, and itaconic acid.

[0076] In the present invention, as comonomers, the functional macromonomer, ether macromonomer I, poly-ester-based phosphate monomer, and unsaturated monomer form a copolymer product (i.e., polycarboxylic acid) through a radical polymerization reaction. According to some embodiments, the mass ratio of the functional macromonomer, ether macromonomer I, poly-ester-based phosphate monomer, and unsaturated monomer is 120:(60-90):(1-5):(20-30), such as 120:80:3:25, 120:80:4:25, 120:90:5:25, 120:85:5:22, 120:70:5:25, 120:70:5:28, etc.

[0077] In the present invention, the temperature of the radical polymerization reaction can be 5-40°C, such as 10°C, 15°C, 15°C, 18°C, 30°C, 32°C, 35°C, 40°C, etc. The temperature of the radical polymerization reaction can also be controlled within any temperature range within the above range, for example, controlled between 15-30°C, or controlled between 20-35°C, etc.

[0078] In the present invention, the time of the polymerization reaction can be determined according to the conversion degree of the comonomers, and generally can be 2-5 h, such as 2 h, 3 h, 3.5 h, 4 h, 5 h, etc.

[0079] In the present invention, the unreacted monomers, etc. can be neutralized by adding a base. As some embodiments, the pH of the reaction system obtained from the polymerization reaction can be adjusted to 6-8 by adding a base, and it is more preferably adjusted to be neutral.

[0080] In the present invention, the base may include sodium hydroxide. Preferably, the base is added in the form of an aqueous solution of the base.

[0081] In some embodiments, the radical polymerization reaction is carried out in the presence of an initiator and a chain transfer agent.

[0082] In the present invention, the initiator may be selected from various water-soluble radical initiators. As some embodiments, the initiator is a redox initiator.

[0083] In the present invention, the redox initiator includes an oxidizing agent and a reducing agent. According to some embodiments, 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.

[0084] In some embodiments, in the redox initiator, the mass ratio of the oxidizing agent to the reducing agent may be 1:(0.1 - 0.8), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc.

[0085] In the present invention, the amount of the initiator used can be selected according to the total amount of the comonomers. According to some embodiments, the mass amount of the initiator is 0.2% - 2% of the total mass of the comonomers (i.e., the total amount of the functional macromonomer, ether macromonomer I, poly-ester phosphate monomer, and unsaturated monomer), such as 0.6%, 0.7%, 0.9%, 1.0%, 1.1%, 1.5%, 1.7%, 1.8%, etc.

[0086] In the present invention, the chain transfer agent may be selected from water-soluble chain transfer agents commonly used in radical polymerization. According to some embodiments, the chain transfer agent is selected from one or more of mercaptoethanol, mercaptopropionic acid, and mercaptoacetic acid.

[0087] In the present invention, the amount of the chain transfer agent used can be selected according to the total amount of the comonomers. According to some embodiments, the mass amount of the chain transfer agent is 0.3% - 2% of the total mass of the comonomers, such as 0.4%, 0.5%, 0.8%, 1.2%, 1.5%, 1.7%, 2%, etc.

[0088] In order to improve the effect of the polymerization reaction, according to some preferred embodiments, the preparation method of the polycarboxylate water reducer comprises the following steps:

[0089] (1) Dissolve the functional macromonomer, ether macromonomer I, poly-ester phosphate monomer, and oxidizing agent in water, and simultaneously dropwise add the following two reaction solutions thereto to carry out the polymerization reaction.

[0090] Reaction solution 1: An aqueous solution mixture of a reducing agent and a chain transfer agent;

[0091] Reaction solution 2: An aqueous solution of an unsaturated monomer;

[0092] (2) After the dropping is completed, continue the reaction for 1 - 2 h;

[0093] (3) Add an alkali to the product obtained in step (2) to adjust the pH to 6 - 8, preferably adjusted to neutral;

[0094] In step (1), control the dropping time to be 1 - 3 h. Before the dropping of the reaction solution or at the initial stage of dropping, preferably control the temperature of the system to be 5 - 20 °C. Preferably, the temperature during the reaction is 10 - 40 °C.

[0095] In step (2), the continuous reaction after the dropping is completed can further improve the conversion degree of the reactants.

[0096] In the present invention, the amount of water can be selected according to the solid content of the viscosity-reducing polycarboxylate water reducer required. According to some embodiments, the amount of water is such that the solid content of the viscosity-reducing polycarboxylate water reducer is not less than 45%, preferably 45% - 60%, for example 50%.

[0097] The second aspect of the present invention provides a polycarboxylate water reducer prepared by the preparation method described in the first aspect of the present invention.

[0098] The polycarboxylate water reducer of the present invention belongs to a viscosity-reducing water reducer. As an admixture, it can effectively improve the workability of concrete, and also has an obvious effect in viscosity reduction. At the same time, while maintaining the compressive strength of concrete, it can also improve the water-reducing and slump-retention properties.

[0099] The third aspect of the present invention provides the application of the polycarboxylate water reducer described in the second aspect of the present invention in building materials.

[0100] 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 to the present invention. Unless otherwise specified, the parts described below all refer to parts by weight.

[0101] The following Synthesis Examples 1 - 4 are used to illustrate the functional macromonomers and their preparation methods used in the examples and comparative examples.

[0102] Synthesis Example 1

[0103] HPEG-1200, 1-hydroxycyclopropanecarboxylic acid, concentrated sulfuric acid and hydroquinone were added into a reactor equipped with a condensation device. The molar ratio of HPEG-1200 to 1-hydroxycyclopropanecarboxylic acid was 1.05∶1. The amount of concentrated sulfuric acid used was 1.0% of the mass of HPEG-1200, and the amount of hydroquinone used was 0.5% of the mass of HPEG-1200. The reaction was carried out at a constant temperature of 100 °C for 5 h under nitrogen protection. After the reaction was completed, it was naturally cooled to room temperature to obtain a viscosity-reducing macromonomer, denoted as monomer A1, and its structure is shown below:

[0104]

[0105] Synthesis Examples 2-4

[0106] Functional macromonomers were prepared according to the method of Synthesis Example 1. The difference was that, as shown in Table 1, the types of reactants were replaced, and the synthesized functional macromonomers were denoted as A2, A3, and A4, respectively.

[0107] Table 1

[0108]

[0109] Synthesis Example 5

[0110] 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 into 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 was completed, it was naturally cooled to obtain a polyester phosphate monomer (i.e., compound C2):

[0111]

[0112] In the following examples and comparative examples, the mass concentration of hydrogen peroxide in hydrogen peroxide solution was 27.5%

[0113] Example 1

[0114] 120 parts of functional macromonomer A1, 80 parts of HPEG-2400, 4 parts of compound C2 and 185 parts of water were added into a reactor. The stirrer and temperature control device were started. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide solution) was added. After stirring for 5 min, the initial temperature was controlled at 5-20 °C, and an aqueous solution of a chain transfer agent and a reducing agent (1.0 part of mercaptoacetic acid, 0.6 part of ascorbic acid, 30 parts of water) and an aqueous solution of an unsaturated monomer (25 parts of acrylic acid, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 20-25 °C, and the dropping time was 2 h. After the dropping was completed, the reaction was continued for 1 h, and then sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-1.

[0115] Example 2

[0116] 120 parts of functional macromonomer A2, 80 parts of TPEG-3000, 4 parts of compound C2 and 190 parts of water were added to a reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide) was added. After stirring for 5 min, the initial temperature was controlled at 5 - 20 °C, and an aqueous solution of a chain transfer agent and a reducing agent (0.7 part of mercaptoacetic acid, 0.6 part of ascorbic acid, 30 parts of water) and an aqueous solution of an unsaturated monomer (28 parts of acrylic acid, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 20 - 25 °C, and the dropping time was 2 h. After the dropping was completed, the reaction continued for 1 h, and then sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-2.

[0117] Example 3

[0118] 120 parts of functional macromonomer A3, 90 parts of TPEG-2400, 5 parts of compound C2 and 190 parts of water were added to a reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide) was added. After stirring for 5 min, the initial temperature was controlled at 5 - 20 °C, and then an aqueous solution of a chain transfer agent and a reducing agent (1.0 part of mercaptoacetic acid, 0.8 part of ascorbic acid, 30 parts of water) and an aqueous solution of an unsaturated monomer (22 parts of acrylic acid, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 25 - 30 °C, and the dropping time was 2 h. After the dropping was completed, the reaction continued for 1 h, and then sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-3.

[0119] Example 4

[0120] 120 parts of functional macromonomer A4, 80 parts of TPEG-2400, 5 parts of compound C2 and 180 parts of water were added to a reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide) was added. After stirring for 5 min, the initial temperature was controlled at 5 - 20 °C, and then an aqueous solution of a chain transfer agent and a reducing agent (1 part of mercaptoacetic acid, 0.6 part of ascorbic acid, 30 parts of water) and a mixed solution of unsaturated monomers (18 parts of acrylic acid, 3 parts of maleic anhydride, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 25 - 30 °C, and the dropping time was 2 h. After the dropping was completed, the reaction continued for 1 h, and then an aqueous solution of sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-4.

[0121] Example 5

[0122] 120 parts of functional macromonomer A1, 80 parts of TPEG-2400, 4 parts of compound C2 and 185 parts of water were added to a reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide) was added. After stirring for 5 min, the initial temperature was controlled at 5-20 °C, and an aqueous solution mixture of a chain transfer agent and a reducing agent (1.0 part of mercaptoacetic acid, 0.6 part of ascorbic acid, 30 parts of water) and an aqueous solution of an unsaturated monomer (25 parts of acrylic acid, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 20-25 °C, and the dropping time was 2 h. After the dropping was completed, the reaction was continued for 1 h, and then sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-5.

[0123] Example 6

[0124] 120 parts of functional macromonomer A1, 70 parts of TPEG-2400, 3 parts of compound C2 and 175 parts of water were added to a reactor. The stirrer and temperature control device were turned on. After the materials were mixed evenly, an oxidant (2.2 parts of hydrogen peroxide solution) was added. After stirring for 5 min, the initial temperature was controlled at 5-20 °C, and an aqueous solution mixture of a chain transfer agent and a reducing agent (1.2 parts of mercaptoacetic acid, 0.8 part of ascorbic acid, 30 parts of water) and an aqueous solution of an unsaturated monomer (15 parts of acrylic acid, 10 parts of maleic anhydride, 15 parts of water) were added dropwise. During the reaction process, the temperature was controlled at 20-35 °C, and the dropping time was 1.5 h. After the dropping was completed, the reaction was continued for 1.5 h, and then sodium hydroxide was added to adjust the pH to neutral to obtain a polycarboxylate superplasticizer, denoted as PCE-6.

[0125] Comparative Example 1

[0126] The polycarboxylate superplasticizer was prepared according to the method of Example 5, except that functional macromonomer A1 and compound C1 were not added, and the dosage of TPEG-2400 was adjusted to 204 parts. The prepared polycarboxylate superplasticizer was denoted as PCE-d1.

[0127] Comparative Example 2

[0128] The polycarboxylate superplasticizer was prepared according to the method of Example 5, except that functional macromonomer A1 was not used, and the dosage of TPEG-2400 was adjusted to 200 parts. The prepared polycarboxylate superplasticizer was denoted as PCE-d2.

[0129] Comparative Example 3

[0130] The polycarboxylate superplasticizer was prepared according to the method of Example 5, except that compound C1 was not used, and the dosage of TPEG-2400 was adjusted to 84 parts. The prepared polycarboxylate superplasticizer was denoted as PCE-d3.

[0131] Test Example

[0132] The test examples are used to illustrate the application performance of the polycarboxylate superplasticizers PCE-1 to PCE-6 and PCE-d1 to PCE-d3 prepared in the above examples and comparative examples.

[0133] Using Jidong Cement, adjusting the dosage of the admixture to make the slump of the concrete be (240±10) mm and the spread be (650±10) mm, according to GB 8076-2008 "Concrete Admixtures", test the properties of the superplasticizer on the initial and 3h slump and spread of the concrete, the emptying time of the inverted slump cone at 0h, and the compressive strength at each age.

[0134] The concrete mix ratio is: cement 430 kg / m 3 , fly ash 30 kg / m 3 , common sand 551 kg / m 3 , fine sand 184 kg / m 3 , small stones (particle size between 5 and 10 mm) 317 kg / m 3 , large stones (particle size 10 - 15 mm) 740 kg / m 3 , water 153 kg / m 3 .

[0135] The admixture formula is: standard polycarboxylate superplasticizer (PCE-SP type): viscosity-reducing polycarboxylate superplasticizer = 1:1 compounded (mass ratio), and formulated into an external solution with a solid content of 15%.

[0136] The test results of the concrete are shown in Table 2.

[0137] Table 2

[0138]

[0139] Combined with Table 2, it can be seen from the application data of the polycarboxylate superplasticizers provided in Examples 1 - 6 and Comparative Examples 1 - 3 that when the polycarboxylate superplasticizers prepared by the methods of Examples 1 - 6 are applied to concrete, they can improve the water-reducing performance (the percentage of the admixture in the cementitious material is relatively low), reduce the viscosity of the concrete (the initial emptying time is not higher than 13 s), and the difference in the loss of spread and slump retention is small, indicating that it has high slump retention and little impact on fluidity, and does not affect the compressive strength either.

[0140] Comparing Example 5 with Comparative Examples 1 - 3, it can be seen that the viscosity-reducing mother liquor prepared by adding the functional macromonomer (A1) and the multi-ester phosphate monomer (Compound C2) simultaneously has better slump retention performance and a greater reduction in the viscosity of the concrete. In addition, comparing Example 5 with Example 1, it can be seen that the slump retention loss of the viscosity reduction prepared with the five-carbon polyether macromonomer (TPEG) is smaller than that with the four-carbon polyether macromonomer (HPEG).

[0141] In summary, the polycarboxylate water reducer prepared by the present invention has obvious effects as a viscosity-reducing mother liquor in improving the fluidity of concrete and reducing viscosity. The water-reducing performance and slump retention performance are also improved, and there is no negative impact on the strength.

[0142] 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 cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the specification 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 in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a polycarboxylate water-reducing agent, characterized in that: include: The comonomers including the functional macromonomer, the ether macromonomer I, the multiester phosphate monomer and the unsaturated monomer are subjected to a free radical polymerization reaction in water, and then neutralized with a base to obtain a polycarboxylic acid water-reducing agent; wherein the unsaturated monomer is an unsaturated carboxylic acid and / or an unsaturated acid anhydride, and the general structural formula of the functional macromonomer is shown in Formula 1: Wherein, R1 represents -(CH2) x -, x is an integer of 1 to 4, n 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 preparation method according to claim 1, characterized in that: The ether macromonomer I is isopentenyl polyoxyethylene ether and / or methylallyl polyoxyethylene ether; Preferably, the average molecular weight of the ether macromonomer I is 2000-3000.

3. The preparation method according to claim 1 or 2, characterized in that: The functional 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 isopentenyl polyoxyethylene ether and / or methylallyl polyoxyethylene ether; Preferably, in Formula 1, n is an integer of 10 to 30; Preferably, 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.

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

5. The preparation method according to any one of claims 1 to 4, characterized in that: The unsaturated monomer is selected from at least one of acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The mass ratio of the functional macromonomer, ether macromonomer I, polyester phosphate monomer and unsaturated monomer is 120: (60-90): (1-5): (20-30); Preferably, the temperature of the free radical polymerization reaction is 5 to 40° C., and the reaction time is 2 to 5 hours.

7. The preparation 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 and a chain transfer agent; Preferably, the initiator is a redox initiator; Preferably, the oxidizing agent in the redox initiator is selected from at least one of hydrogen peroxide, ammonium persulfate and sodium persulfate, and the reducing agent in the redox initiator is selected from at least one of ascorbic acid and sodium formaldehyde sulfoxylate; Preferably, the mass amount of the initiator is 0.2% 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 0.3% to 2% of the total mass of the comonomer.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises the following steps: (1) dissolving the functional macromonomer, ether macromonomer I, polyester phosphate monomer and oxidant in water, and respectively adding a mixed aqueous solution of a reducing agent and a chain transfer agent and an aqueous solution of an unsaturated monomer thereto; controlling the dropping time to be 1 to 3 hours, and the temperature during the reaction to be 10 to 40° C.; (2) After the addition is completed, continue the reaction for 1 to 2 hours; (3) adding a base to the product obtained in step (2) to adjust the pH to 6 to 8; Preferably, the amount of water used is such that the solid content of the prepared polycarboxylate water-reducing agent is not less than 45%.

9. The polycarboxylate water-reducing agent prepared by the preparation 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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