Acid anhydride low-sensitive polycarboxylic acid water reducing agent as well as preparation method and application thereof

Abstract

The invention provides an anhydride low-sensitive polycarboxylate superplasticizer as well as a preparation method and application thereof, maleic monoester subjected to alcoholysis of maleic anhydride and ethylene oxide are subjected to ring opening polymerization to prepare an intermediate, carboxyl in maleic ester is esterified by ethylene oxide, part of carboxylic acid is protected, main chain cross-linking is prevented, and the anhydride low-sensitive polycarboxylate superplasticizer is prepared. The quality of the polymer is improved; later-stage precipitation is prevented; the slump retaining performance of the slump retaining agent is further improved by protecting carboxyl through esterification, so that the doping amount of the slump retaining agent in the application process of the water reducing agent is lower, and the effect is more obvious. Compared with the prior art, the high-conversion-rate low-sensitivity viscosity reduction type mother liquor is synthesized through copolymerization of the isopentenol polyoxyethylene ether, the maleic anhydride and the functional monomer of the maleic anhydride, the solid content of a base solution and the use amount of a catalyst are adjusted, so that the high-conversion-rate low-sensitivity viscosity reduction type mother liquor can be subjected to a polymerization reaction at the normal temperature, and the reaction energy consumption at the normal temperature is low. The maleic anhydride functionalized intermediate participates in the free radical polymerization reaction, and the monomer conversion rate of the reaction product is generally higher than 80%.

Description

Technical Field

[0001] The invention belongs to the field of water reducing agents, and in particular relates to an acid anhydride low-sensitivity polycarboxylic acid water reducing agent and a preparation method and application thereof. Background Art

[0002] In recent years, with the progress of urbanization and the continuous development of the construction industry, two major problems have emerged in the construction industry: First, various types of machine-made sand have become the main fine aggregate in concrete, and the mud of different components in machine-made sand has brought new challenges to the selectivity, adaptability and construction performance of admixtures; second, a large number of high-strength concretes above C50 have appeared. These concretes have been widely used in bridge projects and high-rise buildings due to their good fluidity, high strength and excellent durability. These high-strength concretes use a large amount of cementitious materials and a low water-cement ratio, resulting in problems such as high viscosity, slow flow rate and difficulty in construction.

[0003] The high viscosity of high-strength concrete has become a major problem in its construction application. The high viscosity of concrete will lead to a series of construction problems such as excessive pumping pressure and pump blockage. At the same time, it also increases the workload of concrete distribution. Therefore, for high-strength concrete configured with machine-made sand, the polycarboxylic acid admixture is required not only to have good water-reducing and slump-retaining properties, but also to have a certain anti-mud effect and excellent low sensitivity.

[0004] In addition to polyether, the mainstream raw materials for the synthesis of polycarboxylic acid water reducers in China are mainly acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, maleic anhydride, etc. Among them, maleic anhydride is relatively less active, relatively stable, not easy to homopolymerize and relatively easy to copolymerize, but it also has the phenomenon of low synthetic conversion rate, resulting in a decrease in the effective content in the water reducer mother liquor. The symmetrical structure of maleic anhydride also has electron-withdrawing properties. When electron-donating polyether is added to the polymerization system, a complex is first formed, and then free radical copolymerization is carried out to generate a copolymer with a cross-linked structure. The alternating distribution of the main chain ether and the anhydride makes the polymer have good dispersibility, but there is also a phenomenon of precipitation of the polymer when it is left to stand in the later stage, resulting in unstable polymer quality and other problems. Most of the existing polycarboxylic acid water reducers have a long main chain and a long side chain structure, and their water-reducing performance is mostly provided by the steric hindrance of the long side chain. However, the clay content in the machine-made sand is relatively high, resulting in the polycarboxylic acid water reducer being adsorbed in the layered structure of the clay, resulting in the failure of the water reducer performance. There are many reports in the literature and patents on anhydride type water reducers. Most of their synthesis is carried out under high temperature conditions, with high energy consumption and difficult to control the reaction. Summary of the invention

[0005] The purpose of the present invention is to provide an acid anhydride low-sensitivity polycarboxylate water reducer and a preparation method thereof, wherein isopentanol polyoxyethylene ether is copolymerized with maleic anhydride and its functionalized monomer to form a high-conversion low-sensitivity viscosity-reducing mother solution, and the present invention is a polymerization reaction at room temperature, with low energy consumption and high conversion rate. The prepared acid anhydride low-sensitivity polycarboxylate water reducer has good adaptability and low-sensitivity viscosity-reducing effect.

[0006] Another object of the present invention is to provide an application of anhydride low-sensitivity polycarboxylate water-reducing agent for concrete.

[0007] The specific technical solutions of the present invention are as follows:

[0008] The present invention provides an acid anhydride low-sensitivity polycarboxylate water reducer, and its structural formula is:

[0009]

[0010] In the structural formula, a ranges from 0 to 3, b ranges from 0 to 2, c ranges from 0 to 3, d ranges from 0 to 2, e ranges from 0 to 4, f ranges from 0 to 2, and g ranges from 0 to 4; a, c, e and g cannot be 0 at the same time, and b, d and e cannot be 0 at the same time.

[0011] In the structural formula, n ranges from 58 to 62;

[0012] Preferably, a:b=(1.2-2.9):1;

[0013] b:c=1:(1.4~2.0);

[0014] d:e=1:(1.5~4.0);

[0015] f:g=1:(2.0~4.0);

[0016] a:b:c:d=(1.2~2.9):1:(1.4~2.0):1;

[0017] a:b:e=(1.2~2.9):1: (1.5~4.0);

[0018] b:c:g=1:(1.4~2.0): (2.0~4.0);

[0019] e:f:g=(1.5~4.0):1:(2.0~4.0).

[0020] The present invention provides a method for preparing an anhydride low-sensitivity polycarboxylate water-reducing agent, comprising the following steps:

[0021] 1) mixing maleic acid ester with ethylene oxide and a catalyst, heating and pressurizing the mixture under a protective atmosphere to obtain an intermediate;

[0022] 2) After uniformly mixing maleic acid ester, the intermediate prepared in step 1), isopentanol polyoxyethylene ether and water, a chain transfer agent, an oxidant and a catalyst are added to react; then an aqueous solution of a reducing agent is added dropwise, and after the reaction is completed, a sodium hydroxide solution is added to adjust the pH value to 5-6, thereby obtaining an anhydride low-sensitive polycarboxylic acid water reducer.

[0023] In step 1), the molar ratio of maleate to ethylene oxide is 1:1.05;

[0024] In step 1), the mass ratio of the maleate to the catalyst is 200:1;

[0025] In step 1), the maleate is selected from methyl maleate (or monomethyl maleate) or ethyl maleate (or monoethyl maleate);

[0026] In step 1), the preparation method of the maleate is as follows: the alcohol is first heated to 60-65°C, stirring is started, maleic anhydride is added in 3 times, each time with an interval of 5-10 minutes, the internal temperature is controlled to be lower than 85°C, and after the maleic anhydride is completely melted, the temperature is raised to 95°C, and the reaction is carried out for 120-150 minutes to obtain the maleate; the alcohol and maleic anhydride are reacted in a molar ratio of 1:1; when the alcohol is methanol, methyl maleate is prepared, and when the alcohol used is ethanol, ethyl maleate is prepared.

[0027] In step 1), the protective atmosphere is nitrogen;

[0028] In step 1), the catalyst is selected from p-toluenesulfonic acid, benzenesulfonic acid, o-toluenesulfonic acid, and trifluoromethanesulfonic acid;

[0029] In step 1), the heating and pressurizing reaction refers to 100-120° C., reaction time 2 h, and pressure 0.2-0.3 MPa;

[0030] In step 2), the mass ratio of the maleate, the intermediate prepared in step 1), isopentanol polyoxyethylene ether, water, chain transfer agent, oxidant, catalyst, and reducing agent is 0-40: 0-80: 200-400: 120-260: 2-5: 1.0-5.0: 0.01-0.05: 0.1-1; wherein the maleate and the intermediate prepared in step 1) are not 0 at the same time;

[0031] Step 2) The aqueous solution of the reducing agent refers to a solution obtained by mixing 0.1 to 1 parts by mass of the reducing agent and 40 to 50 parts by mass of water.

[0032] In step 2), the maleate is selected from one or more of methyl maleate and ethyl maleate, and can be methyl maleate, ethyl maleate, or a mixture of methyl maleate and ethyl maleate;

[0033] In step 2), the intermediate is the intermediate prepared in step 1) using methyl maleate or ethyl maleate, or a mixture of intermediates prepared using methyl maleate and ethyl maleate.

[0034] In step 2), the molecular weight of the isopentanol polyoxyethylene ether is 2400;

[0035] In step 2), the reaction is carried out at 20°C to 30°C, and an aqueous solution of a reducing agent is added dropwise within 2.0 to 3.0 hours of the reaction. After the addition is complete, the reaction is continued for 0.5 hours.

[0036] In step 2), the chain transfer agent includes one of sodium hypophosphite and sodium methyl methacrylate sulfonate.

[0037] In step 2), the oxidant is selected from one of hydrogen peroxide and ammonium persulfate, wherein the solubility of hydrogen peroxide is 27.5%.

[0038] In step 2), the catalyst includes ferrous sulfate heptahydrate;

[0039] In step 2), the reducing agent is selected from one of sodium formaldehyde sulfoxylate, L-ascorbic acid, and sodium dioctyl sulfosuccinate (commonly known as German reducing agent E51).

[0040] In step 2), after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5-6.

[0041] The water used in the method of the present invention is desalted water.

[0042] The invention provides an application of an acid anhydride low-sensitivity polycarboxylate water reducer for concrete.

[0043] The present invention uses maleic anhydride alcoholysis to prepare maleic acid monoester and ethylene oxide ring-opening polymerization to prepare an intermediate, uses ethylene oxide to esterify the carboxyl group in maleic ester, protects a part of the carboxylic acid, prevents the generation of main chain crosslinking, and further improves the polymer quality to prevent the generation of later precipitation; and further improves its slump retention performance by esterification protection of the carboxyl group, so that the amount of slump retention agent is lower during the application of the water reducer, and the effect is more obvious. Maleic anhydride is subjected to a two-step esterification reaction, the first step is to introduce an ester group to improve its reaction activity; the second step is to protect its carboxyl group, further esterify to improve the original performance, further improve its reaction activity, and solve the precipitation problem that is prone to occur in the abnormal quality of the polymer in the later stage. In addition, the synthesis process is optimized, the amount of catalyst is increased, the solid content of the bottom liquid is reduced, and the anhydride type water reducer is synthesized at room temperature (below 30°C). Finally, an anhydride type water reducer with low molecular weight, short main chain, and side chains of different lengths and low sensitivity can be prepared. Maleic anhydride has low activity and is relatively stable. It is not easy to homopolymerize but easy to copolymerize. However, according to existing literature and patent reports, the monomer conversion rate of MA and TPEG binary copolymerization under high temperature conditions is less than 60%, unless a third functional monomer is added to reduce the amount of anhydride to increase the monomer conversion rate of the product. The invention can achieve the copolymerization of MA and TPEG at room temperature, with a monomer conversion rate of more than 80%. After MA is esterified and functionalized and then participates in free radical polymerization, the product monomer conversion rate can reach up to 88.59%.

[0044] Compared with the prior art, the present invention uses isopentanol polyoxyethylene ether and maleic anhydride and its functionalized monomers to copolymerize to form a high conversion rate, low sensitivity and viscosity reduction mother liquid, adjusts the solid content of the bottom liquid and the amount of catalyst, so that the present invention can undergo polymerization reaction at room temperature. Compared with the prior art, the reaction energy consumption at room temperature is low, the safety is high, and it is conducive to industrial production. The present invention uses maleic anhydride functionalized intermediates to participate in free radical polymerization reaction, and the monomer conversion rate of the reaction product is generally higher than 80%, which solves the sequelae of the later acid anhydride type water reducer gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the test graph of the monomer conversion rate of the product in Example 1, with a conversion rate of 80.21%;

[0046] Figure 2 This is the test graph of the monomer conversion rate of the product of Example 2, with a conversion rate of 81.41%;

[0047] Figure 3 This is the test diagram of the monomer conversion rate of the product of Example 3, with a conversion rate of 82.54%;

[0048] Figure 4 This is the test graph of the monomer conversion rate of the product of Example 4, with a conversion rate of 83.45%;

[0049] Figure 5This is the test graph of the monomer conversion rate of the product in Example 5, with a conversion rate of 80.25%;

[0050] Figure 6 This is the test graph of the monomer conversion rate of the product in Example 6, with a conversion rate of 80.10%;

[0051] Figure 7 This is the test graph of the monomer conversion rate of the product of Example 7, with a conversion rate of 84.21%;

[0052] Figure 8 This is a test chart of the monomer conversion rate of the product of Example 8, with a conversion rate of 88.59%;

[0053] Fig. 9 This is the test graph of the monomer conversion rate of the product of Comparative Example 1, with a conversion rate of 67.28%;

[0054] Fig.10 This is a test chart of the monomer conversion rate of the product of Comparative Example 2, with a conversion rate of 72.12%. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0057] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0058] The present invention provides a method for preparing an anhydride low-sensitivity polycarboxylate water-reducing agent, which is specifically:

[0059] 1) The alcohol and maleic anhydride are measured in a molar ratio of 1:1. First, the alcohol (excluding water and impurities) is put into a dry glass reactor, the temperature is raised to 65°C, stirring is started, and maleic anhydride is added three times, each time with an interval of 10 minutes, and the internal temperature is controlled below 85°C. After the maleic anhydride is completely melted, the temperature is raised to 95°C and the reaction is carried out for 130 minutes to obtain maleic acid monoester;

[0060] When the alcohol is methanol, methyl maleate is prepared, and when the alcohol is ethanol, ethyl maleate is prepared.

[0061] The reaction equation of methyl maleate is as follows:

[0062]

[0063] The reaction equation of ethyl maleate is as follows:

[0064]

[0065] 2) Preparation of intermediate 1: Methyl maleate and ethylene oxide are calculated in a molar ratio of 1:1.05. Under the protection of a nitrogen atmosphere, methyl maleate and ethylene oxide are reacted in the presence of p-toluenesulfonic acid as a catalyst, with a mass ratio of methyl maleate to the catalyst being 200:1. After nitrogen replacement, ring-opening polymerization is carried out at 110° C., 0.2 MPa, and a reaction time of 2 h to obtain intermediate 1. The reaction equation is as follows:

[0066]

[0067] Preparation of intermediate 2: ethyl maleate and ethylene oxide are calculated in a molar ratio of 1:1.05. Under the protection of nitrogen atmosphere, ethyl maleate and ethylene oxide are reacted in the presence of p-toluenesulfonic acid as a catalyst. The mass ratio of ethyl maleate to the catalyst is 200:1. After nitrogen replacement, ring-opening polymerization is carried out at 110°C, 0.2MPa, and reaction time for 2h to obtain intermediate 2. The reaction equation is as follows:

[0068]

[0069] 3) 0-40 parts of maleic acid monoester in step 1) and 0-80 parts of intermediate in step 2) (both cannot be 0 at the same time), 200-400 parts of isopentanol polyoxyethylene ether and 120-260 parts of water are added to a reaction container and fully dissolved and mixed, and then 2-5 parts of a chain transfer agent, 1.0-5.0 parts of an oxidant, and 0.01-0.05 parts of a catalyst are added; the reaction temperature in the reaction container is maintained at 20° C. to 30° C., and a mixed solution obtained by mixing 0.1-1 parts of a reducing agent and 40-50 parts of water is added dropwise within 2.0 to 3.0 hours. After the reaction is completed, the reaction is continued for 0.5 hours after the addition is completed; and a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5-6, which is an acid anhydride low-sensitive polycarboxylic acid water reducer.

[0070] The invention designs the molecular structure of polycarboxylic acid, further improves the reaction activity of maleic anhydride by esterification with maleic anhydride, and introduces ester groups to improve the collapse retention performance of the polymerized water reducer; secondly, ethylene oxide is used to esterify the carboxyl groups in maleic acid ester to protect a part of the carboxylic acid and prevent the main chain from being cross-linked; furthermore, when the maleic acid ester and the maleic acid ester are used as the main chain together, the rigidity of the main chain in the molecular structure of the polycarboxylic acid water reducer can be improved to prevent the polycarboxylic acid water reducer molecules from being entangled with each other; moreover, the long side chains and the broken branches on the main chain present a three-dimensional structure under the steric hindrance and the structure of the main chain, thereby reducing the consumption of the other components in the clay, and thus the original performance of the water reducer can be exerted to the maximum extent.

[0071] The present invention is further described below through several specific embodiments.

[0072] Example 1

[0073] A method for preparing anhydride low-sensitivity polycarboxylate water-reducing agent, specifically comprising:

[0074] 35 parts of methyl maleate, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water prepared above are selected and added to a reaction container, mixed and dissolved thoroughly, and then 3.5 parts of sodium hypophosphite, 3.0 parts of hydrogen peroxide and 0.01 parts of ferrous sulfate heptahydrate are added; the reaction temperature in the reaction container is maintained at 25°C to 30°C, and a mixed solution obtained by mixing 0.5 parts of sodium dioctyl sulfosuccinate and 50 parts of water is added dropwise within 3 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, which is the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0075] Product structure: n value range 58-62,

[0076] a:b=(1.2~2.9):1.

[0077] Example 2

[0078] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0079] In parts by mass, 40 parts of ethyl maleate and 360 parts of isopentanol polyoxyethylene ether and 260 parts of water in step 1 are added to a reaction container and mixed and dissolved thoroughly, and then 4 parts of sodium hypophosphite, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 20°C to 25°C, and a mixed solution obtained by mixing 0.5 parts of dioctyl sodium succinate sulfonyl and 50 parts of water is added dropwise within 2 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, that is, the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0080] Product structure: The value range of n is 58-62, b:c=1: (1.4~2.0).

[0081] Example 3

[0082] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0083] 60 parts of the intermediate 1 prepared above, 360 parts of isopentanol polyoxyethylene ether, and 260 parts of water are selected and added to a reaction container, mixed and dissolved thoroughly, and then 5 parts of sodium methyl propylene sulfonate, 3.0 parts of ammonium persulfate, and 0.02 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 25°C to 30°C, and a mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water is added dropwise within 3 hours. After the solution is added dropwise, the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, which is the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0084] Product structure: n value range 58-62, d:e=1:

[0085] (1.5~4.0).

[0086] Example 4

[0087] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0088] By mass, 65 parts of the intermediate 2 prepared above, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water are selected and added to a reaction container, mixed and dissolved thoroughly, and then 4.5 parts of sodium hypophosphite, 5.0 parts of ammonium persulfate and 0.015 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 25°C to 30°C, and a mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water is added dropwise within 3 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, which is the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0089] Product structure: The value range of n is 58-62, f:g=1:(2.0~4.0).

[0090] Example 5

[0091] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0092] In parts by mass, 20 parts of methyl maleate and 20 parts of ethyl maleate and 360 parts of isopentanol polyoxyethylene ether and 260 parts of water in step 1 are added to a reaction container, mixed and dissolved thoroughly, and then 4.5 parts of sodium methyl propylene sulfonate, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 25° C. to 30° C., and within 2 hours, a mixed solution obtained by mixing 0.5 parts of sodium formaldehyde sulfoxylate and 50 parts of water is added dropwise, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, that is, the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0093] Product structure: The value range of n is 58-62, a:b:c:d=(1.2~2.9):1:(1.4~2.0):1.

[0094] Example 6

[0095] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0096] In parts by mass, 20 parts of methyl maleate and 40 parts of intermediate 1 prepared above, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water are selected and added to a reaction container, mixed and dissolved thoroughly, and then 3.5 parts of sodium hypophosphite, 4.0 parts of ammonium persulfate and 0.01 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 20°C to 25°C, and a mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water is added dropwise within 3 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, that is, the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0097] Product structure: The value range of n is 58-62, a:b:e=(1.2~2.9):1:(1.5~4.0).

[0098] Example 7

[0099] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0100] In parts by mass, 25 parts of ethyl maleate prepared above, 35 parts of intermediate 2 prepared above, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water are selected and added to a reaction container, mixed and dissolved thoroughly, and then 4 parts of sodium hypophosphite, 3.0 parts of ammonium persulfate and 0.01 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 25°C to 30°C, and within 2 hours, a mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water is added dropwise, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, which is the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0101] Product structure The value range of n is 58-62, b:c:g=1:(1.4~2.0):(2.0~4.0).

[0102] Example 8

[0103] A method for preparing anhydride low-sensitivity polycarboxylate water reducer, specifically comprising:

[0104] In parts by mass, 10 parts of intermediate 1 and 50 parts of intermediate 2 and 360 parts of isopentanol polyoxyethylene ether and 260 parts of water in step 2 are selected and added to a reaction container, mixed and dissolved thoroughly, and then 5 parts of sodium methyl propylene sulfonate, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction container is maintained at 25°C to 30°C, and a mixed solution obtained by mixing 0.5 parts of sodium formaldehyde sulfoxylate and 50 parts of water is added dropwise within 2 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, that is, the acid anhydride low-sensitive polycarboxylic acid water reducer.

[0105] Product structure: The value range of n is 58-62, and e:f:g=(1.5~4.0):1:(2.0~4.0).

[0106] Comparative Example 1

[0107] A method for preparing a polycarboxylate water-reducing agent, specifically comprising:

[0108] 40 parts of maleic anhydride, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water are selected by weight and added to a reaction container, and then fully mixed and dissolved, and then 3 parts of sodium hypophosphite, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate as a catalyst are added; the reaction temperature in the reaction container is maintained at 55°C to 80°C, and a mixed solution obtained by mixing 0.5 parts of sodium formaldehyde sulfoxylate and 50 parts of water is added dropwise within 2 hours, and the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5-6, which is a polycarboxylic acid water reducer.

[0109] Comparative Example 2

[0110] A method for preparing a polycarboxylate water-reducing agent, specifically comprising:

[0111] 45 parts of maleic anhydride, 360 parts of isopentanol polyoxyethylene ether and 260 parts of water are selected by mass and added to a reaction container, after being fully mixed and dissolved, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate as a catalyst are added; the reaction temperature in the reaction container is maintained at 70°C to 80°C, and a mixed solution obtained by mixing 0.5 parts of dioctyl sodium succinate sulfonyl and 50 parts of water is added dropwise within 3 hours, and after the solution is added dropwise, the reaction is continued for 0.5 to 1.0 hours; after the reaction is completed, a sodium hydroxide solution with a mass concentration of 30% is added to adjust the pH value to 5 to 6, thereby obtaining a polycarboxylic acid water reducer.

[0112] Comparative Example 1 Comparative Example 2 The molecular structure is as follows, in which n ranges from 58 to 62, and b:a=1: (2 to 4)

[0113]

[0114] In the application examples of the present invention, unless otherwise specified, the cement used is ordinary Portland cement (P.O42.5). In order to compare the dispersibility and dispersion retention performance of the water reducing agent prepared by the present invention, the cement paste fluidity test was carried out with reference to the GB / T8077-2012 standard. The cement was 300g and the amount of water was 87g. After stirring for 4 minutes, the cement paste fluidity was measured on a flat glass, and the paste fluidity and the rotational viscosity of the cement paste at different times were tested. The test data are shown in Table 1.

[0115] Table 1 Cement paste fluidity and viscosity test

[0116]

[0117]

[0118] From the above data analysis, it can be seen that under the same cement paste fluidity, compared with the comparative example, the product of the present invention can significantly reduce the rotational viscosity of the cement paste.

[0119] Gel permeation chromatography (GPC) was performed on each embodiment and comparative example. The main peak area can be used to visually determine the monomer conversion rate of the product, and the molecular weight of the product can also be detected. It can be seen that the monomer conversion rate prepared in each embodiment is relatively high.

[0120] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. An acid anhydride low-sensitivity polycarboxylate water reducer, characterized in that: The structural formula of the anhydride low-sensitivity polycarboxylate water reducer is: In the structural formula, a ranges from 0 to 3, b ranges from 0 to 2, c ranges from 0 to 3, d ranges from 0 to 2, e ranges from 0 to 4, f ranges from 0 to 2, and g ranges from 0 to 4; a, c, e and g cannot be 0 at the same time, b, d and e cannot be 0 at the same time; n ranges from 58 to 62.

2. A method for preparing the anhydride low-sensitivity polycarboxylate water-reducing agent according to claim 1, characterized in that: The preparation method comprises the following steps: 1) mixing maleic acid ester with ethylene oxide and a catalyst, heating and pressurizing the mixture under a protective atmosphere to obtain an intermediate; 2) After uniformly mixing maleic acid ester, the intermediate prepared in step 1), isopentanol polyoxyethylene ether and water, a chain transfer agent, an oxidant and a catalyst are added to react; then an aqueous solution of a reducing agent is added dropwise, and after the reaction is completed, a sodium hydroxide solution is added to adjust the pH value to 5-6, thereby obtaining an anhydride low-sensitive polycarboxylic acid water reducer.

3. The preparation method according to claim 2, characterized in that: In step 1), the molar ratio of maleate to ethylene oxide is 1:1.05; In step 1), the mass ratio of the maleate to the catalyst is 200:

1.

4. The preparation method according to claim 2, characterized in that: In step 1), the heating and pressurizing reaction refers to 100-120° C., reaction time 2 h, and pressure 0.2-0.3 MPa.

5. The preparation method according to claim 2, characterized in that: In step 1), the preparation method of the maleate is as follows: In step 1), the preparation method of the maleate is as follows: the alcohol is first heated to 60-65°C, stirring is started, maleic anhydride is added in 3 times, each time with an interval of 5-10 minutes, the internal temperature is controlled to be lower than 85°C, and after the maleic anhydride is completely melted, the temperature is raised to 95°C, and the reaction is carried out for 120-150 minutes to obtain the maleate.

6. The preparation method according to claim 2, characterized in that: In step 2), the mass ratio of the maleate, the intermediate prepared in step 1), isopentanol polyoxyethylene ether, water, chain transfer agent, oxidant, catalyst and reducing agent is 0-40: 0-80: 200-400: 120-260: 2-5: 1.0-5.0: 0.01-0.05: 0.1-1; wherein the maleate and the intermediate prepared in step 1) are not 0 at the same time.

7. The preparation method according to claim 2, characterized in that: In step 2), the maleate is selected from one or more of methyl maleate and ethyl maleate.

8. The preparation method according to claim 2, characterized in that: In step 2), the intermediate is one or more of the intermediates prepared from methyl maleate or ethyl maleate in step 1).

9. The preparation method according to claim 2, characterized in that: In step 2), the reaction is carried out at 20°C to 30°C, and an aqueous solution of a reducing agent is added dropwise within 2.0 to 3.0 hours of the reaction. After the addition is complete, the reaction is continued for 0.5 hours.

10. An application of the anhydride low-sensitivity polycarboxylate water-reducing agent according to claim 1, characterized in that: For concrete.

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