Anhydride low-sensitivity polycarboxylic acid water reducing agent, preparation method and application thereof

Abstract

The application provides an acid anhydride low-sensitivity polycarboxylic acid water reducing agent and a preparation method and application thereof, an intermediate is prepared by alcoholysis of maleic anhydride and ring-opening polymerization of maleic acid monoester and ethylene oxide, the carboxyl in the maleic acid ester is esterified by ethylene oxide, a part of carboxylic acid is protected, crosslinking of the main chain is prevented, and then the polymer quality is improved to prevent the generation of later-stage precipitation; and the esterification protects the carboxyl, further improves the slump flow retention performance, makes the slump flow retention agent content lower in the application process of the water reducing agent, and the effect is more obvious. Compared with the prior art, the isopentenyl alcohol polyoxyethylene ether is copolymerized with maleic anhydride and a functional monomer of the maleic anhydride to synthesize a high-conversion-rate low-sensitivity viscosity-reducing mother liquor, the solid content of the base liquid and the catalyst dosage are adjusted, so that the application can occur the polymerization reaction at normal temperature, and the energy consumption is low at normal temperature. The intermediate after functionalization of the maleic anhydride is used to participate 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 application belongs to the field of water reducing agent, and particularly relates to an acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the development of urbanization and the continuous development of the construction industry, two major problems have appeared in the construction engineering industry: first, various types of machine-made sand have become the main fine aggregate in concrete, and the selectivity, adaptability and construction performance of the additive are challenged by different components of mud in machine-made sand; second, a large amount of high-strength concrete above C50 has appeared, and these high-strength concrete has been widely used in bridge engineering and high-rise buildings due to its good fluidity, high strength and excellent durability. The use of a large amount of cementitious materials and a low water-binder ratio in these high-strength concrete results in high viscosity, slow flow rate and difficulty in construction of the concrete.

[0003] The high viscosity of high-strength concrete has become a major problem in its construction application, and the high viscosity of concrete will result in 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 prepared with machine-made sand, not only does the polycarboxylic acid additive need to have good water-reducing and slump-retaining performance, but it also needs to have certain anti-mud effect and excellent low-sensitivity performance.

[0004] The main raw materials for synthesizing polycarboxylic acid water reducing agent in China, except polyether, are mainly acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate and maleic anhydride. Among them, maleic anhydride has relatively low relative activity, is relatively stable, is not easy to homopolymerize and is relatively easy to copolymerize, but also has the phenomenon of low synthesis conversion rate, resulting in a decrease in the effective content of the water reducing agent mother liquor. Maleic anhydride has a symmetrical structure and electron-withdrawing property. When an electron-donating polyether is added to the polymerization system, a complex is first formed, and then free radical copolymerization is carried out, thus generating a copolymer with a crosslinked structure. The alternating distribution of ether and anhydride in the main chain of the polymer results in good dispersing ability of the polymer, but there are also problems such as precipitation of the polymer after standing for a long time, resulting in unstable quality of the polymer. Most of the existing polycarboxylic acid water reducing agents have long main chains and long side chain structures, and the water-reducing performance is provided by the steric hindrance of the long side chain. However, the high clay content in machine-made sand leads to the adsorption of polycarboxylic acid water reducing agent in the layered structure of clay, resulting in failure of the performance of the water reducing agent. Acid anhydride type water reducing agents are reported in many literatures and patents, and most of the synthesis is carried out under high temperature conditions, which has high energy consumption and the reaction is difficult to control. SUMMARY

[0005] The acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and the preparation method thereof have the advantages that the polymerization reaction occurs at normal temperature, the energy consumption is low, the conversion rate is high, the acid anhydride low-sensitivity type polycarboxylic acid water reducing agent prepared has good adaptability and low-sensitivity viscosity reduction effect.

[0006] The acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and the preparation method thereof have the advantages that the polymerization reaction occurs at normal temperature, the energy consumption is low, the conversion rate is high, the acid anhydride low-sensitivity type polycarboxylic acid water reducing agent prepared has good adaptability and low-sensitivity viscosity reduction effect.

[0007] The acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and the preparation method thereof have the advantages that the polymerization reaction occurs at normal temperature, the energy consumption is low, the conversion rate is high, the acid anhydride low-sensitivity type polycarboxylic acid water reducing agent prepared has good adaptability and low-sensitivity viscosity reduction effect.

[0008] The acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and the preparation method thereof have the advantages that the polymerization reaction occurs at normal temperature, the energy consumption is low, the conversion rate is high, the acid anhydride low-sensitivity type polycarboxylic acid water reducing agent prepared has good adaptability and low-sensitivity viscosity reduction effect.

[0009]

[0010] In the structural formula, a is 0-3, b is 0-2, c is 0-3, d is 0-2, e is 0-4, f is 0-2, and g is 0-4; 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 is 58-62;

[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 acid anhydride low-sensitivity type polycarboxylic acid water reducing agent and the preparation method thereof have the advantages that the polymerization reaction occurs at normal temperature, the energy consumption is low, the conversion rate is high, the acid anhydride low-sensitivity type polycarboxylic acid water reducing agent prepared has good adaptability and low-sensitivity viscosity reduction effect.

[0021] 1) Maleic acid ester is mixed with ethylene oxide and a catalyst, and heated and pressurized to react under a protective atmosphere to obtain an intermediate;

[0022] 2) mixing the maleate, the intermediate prepared in step 1), isoprenol polyoxyethylene ether and water, adding chain transfer agent, oxidant and catalyst, and reacting; then adding an aqueous solution of reducing agent drop by drop, and after the reaction is completed, adding sodium hydroxide solution to adjust the pH value to 5-6 to obtain the anhydride low-sensitivity polycarboxylic acid water reducer.

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

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

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

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

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

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

[0029] In step 1), the heating and pressurization reaction refers to 100-120℃, reaction for 2h, and pressure of 0.2-0.3MPa;

[0030] In step 2), the mass ratio of the maleate, the intermediate prepared in step 1), isoprenol 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] The aqueous solution of the reducing agent in step 2) refers to a solution obtained by mixing 0.1-1 parts of the reducing agent and 40-50 parts of water.

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

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

[0034] In step 2), the isopentenyl alcohol polyoxyethylene ether has a molecular weight of 2400.

[0035] In step 2), the reaction is carried out at 20-30℃, and the aqueous solution of the reducing agent is added dropwise within 2.0-3.0 hours, and the reaction is continued for 0.5h after the dropwise addition is completed.

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

[0037] In step 2), the oxidizing agent is selected from one of hydrogen peroxide and ammonium persulfate, wherein the solubility of the 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 dioctyl sodium sulfosuccinate (commonly known as German reducing agent E51).

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

[0041] The water used in the method is desalinated water.

[0042] The application provides the acid anhydride low-sensitivity polycarboxylic acid water reducer and a concrete.

[0043] The application uses maleic anhydride alcoholysis to prepare a maleic acid monoester intermediate, esterifies the carboxyl group in the maleic acid ester with ethylene oxide, protects part of the carboxylic acid to prevent the generation of main chain crosslinking, and further improves the polymer quality to prevent the generation of late-stage precipitation; and further improves the slump retention performance of the carboxyl group by esterification protection, so that the slump retention agent content is lower and the effect is more obvious in the application process of the water reducing agent. The maleic anhydride is subjected to two-step esterification reaction, in the first step, an ester group is introduced to improve the reactivity; in the second step, the carboxyl group is protected and further esterified to improve the original performance, further improve the reactivity, and solve the problem of abnormal precipitation of the late-stage polymer. In addition, the synthesis process is optimized, the catalyst dosage is increased, and the solid content of the bottom liquid is reduced to realize the synthesis of anhydride type water reducing agent at room temperature (below 30 DEG C). Finally, an anhydride type water reducing agent with low sensitivity, low molecular weight, short main chain and long side chain can be prepared. Maleic anhydride has low activity and is relatively stable, and is relatively easy to copolymerize rather than homopolymerize. However, according to the existing literature and patents, MA and TPEG are copolymerized, and the monomer conversion rate is less than 60% under high temperature conditions. Unless a third functional monomer is added to reduce the amount of anhydride, the monomer conversion rate of the product can be increased. The application can realize the copolymerization of MA and TPEG at room temperature, and the monomer conversion rate is greater than 80%. After the esterification of MA is functionalized, it can participate in the free radical polymerization to realize the monomer conversion rate of the product up to 88.59%.

[0044] Compared with the prior art, the application uses isopentenyl alcohol polyoxyethylene ether to copolymerize with maleic anhydride and its functionalized monomer to synthesize a high-conversion-rate low-sensitivity viscosity-reducing mother liquor. By adjusting the solid content of the bottom liquid and the catalyst dosage, the application can occur polymerization reaction at room temperature. Compared with the prior art, the energy consumption of the reaction at room temperature is low, the safety is higher, and the industrial production is beneficial. The intermediate of the application participates in the free radical polymerization reaction after the functionalization of maleic anhydride. The monomer conversion rate of the reaction product is generally higher than 80%, and the sequelae of the late-stage anhydride type water reducing agent gel are solved. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is the monomer conversion rate test diagram of the product of example 1, and the conversion rate is 80.21%;

[0046] Figure 2 It is the monomer conversion rate test diagram of the product of example 2, and the conversion rate is 81.41%;

[0047] Figure 3 It is the monomer conversion rate test diagram of the product of example 3, and the conversion rate is 82.54%;

[0048] Figure 4 It is the monomer conversion rate test diagram of the product of example 4, and the conversion rate is 83.45%;

[0049] Figure 5The monomer conversion rate test chart of the product of Example 5 is shown in the figure, and the conversion rate is 80.25%;

[0050] Figure 6 The monomer conversion rate test chart of the product of Example 6 is shown in the figure, and the conversion rate is 80.10%;

[0051] Figure 7 The monomer conversion rate test chart of the product of Example 7 is shown in the figure, and the conversion rate is 84.21%;

[0052] Figure 8 The monomer conversion rate test chart of the product of Example 8 is shown in the figure, and the conversion rate is 88.59%;

[0053] Figure 9 The monomer conversion rate test chart of the product of Comparative Example 1 is shown in the figure, and the conversion rate is 67.28%;

[0054] Figure 10 The monomer conversion rate test chart of the product of Comparative Example 2 is shown in the figure, and the conversion rate is 72.12%. DETAILED DESCRIPTION

[0055] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0056] The test materials and reagents used in the following examples, and the like, can be obtained from commercial channels if not otherwise specified.

[0057] If the specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or according to the product instructions can be used.

[0058] The present application provides a preparation method of an anhydride low-sensitivity polycarboxylic acid water reducing agent, specifically comprising the following steps:

[0059] 1) The alcohol and maleic anhydride are metered according to a molar ratio of 1:1, the alcohol (free of impurities) is first put into anhydrous glass reactor, heated to 65℃, and stirred, and the maleic anhydride is put in three times with an interval of 10 minutes each time, the internal temperature is controlled to be lower than 85℃, after the maleic anhydride is completely melted, the temperature is raised to 95℃, and the reaction is carried out for 130 minutes, to obtain maleic acid monoester;

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

[0061] The reaction equation of maleic acid methyl ester is as follows:

[0062]

[0063] The reaction equation of maleic acid ethyl ester is as follows:

[0064]

[0065] 2) Preparation of intermediate 1: maleic acid methyl ester and ethylene oxide are calculated at a molar ratio of 1:1.05, under the protection of nitrogen atmosphere, maleic acid methyl ester and ethylene oxide are subjected to ring-opening polymerization under the action of a catalyst p-toluene sulfonic acid, the mass ratio of maleic acid methyl ester and the catalyst is 200:1, after nitrogen replacement, the reaction is carried out at 110°C, 0.2MPa for 2h, to obtain intermediate 1, the reaction equation is as follows:

[0066]

[0067] Preparation of intermediate 2: maleic acid ethyl ester and ethylene oxide are calculated at a molar ratio of 1:1.05, under the protection of nitrogen atmosphere, maleic acid ethyl ester and ethylene oxide are subjected to ring-opening polymerization under the action of a catalyst p-toluene sulfonic acid, the mass ratio of maleic acid ethyl ester and the catalyst is 200:1, after nitrogen replacement, the reaction is carried out at 110°C, 0.2MPa 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) and 200-400 parts of isopentenyl alcohol polyoxyethylene ether and 120-260 parts of water are added into a reaction vessel and fully dissolved and mixed, then 2-5 parts of a chain transfer agent, 1.0-5.0 parts of an oxidizing agent and 0.01-0.05 parts of a catalyst are added; the reaction temperature in the reaction vessel is kept at 20-30°C, a mixed solution obtained by mixing 0.1-1 parts of a reducing agent and 40-50 parts of water is added dropwise within 2.0-3.0 hours, after the dropwise addition is completed, the reaction is continued for 0.5h; then a 30% sodium hydroxide solution is added to adjust the pH value to 5-6, to obtain an anhydride low-sensitivity polycarboxylic acid water reducer.

[0070] The present application is by designing the molecular structure of polycarboxylic acid, using maleic anhydride esterification to further improve the reactivity of maleic anhydride, and introducing ester group to improve the slump performance of the polycarboxylic acid water reducing agent; secondly, using ethylene oxide to esterify the carboxyl group in maleic acid ester, protecting a part of carboxylic acid to prevent the generation of main chain crosslinking; moreover, when it and maleic acid ester are used as main chain together, the stiffness of the main chain in the molecular structure of polycarboxylic acid water reducing agent can be improved, and the mutual entanglement of polycarboxylic acid water reducing agent molecules can be prevented; furthermore, the long side chain and broken chain on the main chain are in a three-dimensional structure under the structure of the main chain and steric hindrance, so that the consumption of other components in clay is reduced, and thus the original energy efficiency of the water reducing agent can be maximized.

[0071] The present application is further illustrated by the following specific examples.

[0072] Example 1

[0073] A preparation method of an anhydride low sensitivity type polycarboxylic acid water reducing agent, specifically:

[0074] 35 parts of maleic acid methyl ester prepared above and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water are selected by mass fraction, and after being fully mixed and dissolved, 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 25-30℃, and within 3 hours, a mixed solution obtained by mixing 0.5 parts of succinic acid dioctyl ester sulfonate sodium and 50 parts of water is added dropwise, the solution is added dropwise, and the reaction is continued for 0.5 hours; after the reaction is completed, a 30% sodium hydroxide solution is added to adjust the pH value to 5-6, and the anhydride low sensitivity type polycarboxylic acid water reducing agent is obtained.

[0075] Product structure: n is in the range of 58-62,

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

[0077] Example 2

[0078] A preparation method of an anhydride low sensitivity type polycarboxylic acid water reducing agent, specifically:

[0079] Selecting 40 parts of maleic acid ethyl ester and 360 parts of isopentenyl alcohol polyoxyethylene ether, and 260 parts of water in step 1 by mass fraction, after fully mixing and dissolving, add 4 parts of sodium hypophosphite, 5.0 parts of hydrogen peroxide, 0.02 parts of ferrous sulfate heptahydrate catalyst; keep the reaction temperature in the reaction vessel at 20-25℃, in 2 hours, add the mixed solution obtained by mixing 0.5 parts of succinic acid dioctyl sulfonate sodium and 50 parts of water, after the solution is added, continue to react for 0.5 hours; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 5-6, which is the acid anhydride low sensitivity polycarboxylic acid water reducer.

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

[0081] Example 3

[0082] A preparation method of an acid anhydride low sensitivity polycarboxylic acid water reducer, specifically:

[0083] Selecting 60 parts of the above prepared intermediate 1 and 360 parts of isopentenyl alcohol polyoxyethylene ether, and 260 parts of water by mass fraction, after fully mixing and dissolving in the reaction vessel, add 5 parts of sodium methacrylate, 3.0 parts of ammonium persulfate, 0.02 parts of ferrous sulfate heptahydrate catalyst; keep the reaction temperature in the reaction vessel at 25-30℃, in 3 hours, add the mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water, after the solution is added, continue to react for 0.5 hours; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 5-6, which is the acid anhydride low sensitivity 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 preparation method of an acid anhydride low sensitivity polycarboxylic acid water reducer, specifically:

[0088] Selecting by mass fraction, 65 parts of the above prepared intermediate 2 and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water are added into a reaction vessel and fully mixed and dissolved, 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 vessel is kept at 25-30℃, 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 30% sodium hydroxide solution is added to adjust the pH value to 5-6, and the acid anhydride low-sensitivity polycarboxylic acid water reducer is obtained.

[0089] Product structure: n is in the range of 58-62, and f:g = 1:(2.0-4.0).

[0090] Example 5

[0091] A preparation method of an acid anhydride low-sensitivity polycarboxylic acid water reducer, specifically:

[0092] Selecting by mass fraction, 20 parts of methyl maleate and 20 parts of ethyl maleate in step 1 and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water are added into a reaction vessel and fully mixed and dissolved, then 4.5 parts of sodium methallyl sulfonate, 5.0 parts of hydrogen peroxide and 0.02 parts of ferrous sulfate heptahydrate catalyst are added; the reaction temperature in the reaction vessel is kept at 25-30℃, and a mixed solution obtained by mixing 0.5 parts of formaldehyde sodium bisulfite and 50 parts of water is added dropwise within 2 hours, after the solution is added dropwise, the reaction is continued for 0.5 hours; after the reaction is completed, a 30% sodium hydroxide solution is added to adjust the pH value to 5-6, and the acid anhydride low-sensitivity polycarboxylic acid water reducer is obtained.

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

[0094] Example 6

[0095] A preparation method of an acid anhydride low-sensitivity polycarboxylic acid water reducer, specifically:

[0096] Selecting 20 parts of the above prepared methyl maleate and 40 parts of intermediate 1 and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water by mass fraction, after fully mixing and dissolving, add 3.5 parts of sodium hypophosphite, 4.0 parts of ammonium persulfate, 0.01 parts of ferrous sulfate heptahydrate catalyst; keep the reaction temperature in the reaction vessel at 20-25℃, in 3 hours, drop the mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water, after the solution is added, continue to react for 0.5 hours; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 5-6, which is the said anhydride low sensitive polycarboxylic acid water reducer.

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

[0098] Example 7

[0099] A preparation method of an anhydride low sensitive polycarboxylic acid water reducer, specifically:

[0100] Selecting 25 parts of the above prepared ethyl maleate and 35 parts of the above prepared intermediate 2 and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water by mass fraction, after fully mixing and dissolving, add 4 parts of sodium hypophosphite, 3.0 parts of ammonium persulfate, 0.01 parts of ferrous sulfate heptahydrate catalyst; keep the reaction temperature in the reaction vessel at 25-30℃, in 2 hours, drop the mixed solution obtained by mixing 0.5 parts of L-ascorbic acid and 50 parts of water, after the solution is added, continue to react for 0.5 hours; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 5-6, which is the said anhydride low sensitive polycarboxylic acid water reducer.

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

[0102] Example 8

[0103] A preparation method of an anhydride low sensitive polycarboxylic acid water reducer, specifically:

[0104] Select 10 parts of intermediate 1 and 50 parts of intermediate 2 and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water in step 2 by mass fraction, add 5 parts of sodium methallyl sulfonate, 5.0 parts of hydrogen peroxide, 0.02 parts of ferrous sulfate heptahydrate catalyst, mix well and dissolve, keep the reaction temperature in the reaction vessel at 25-30℃, add the mixed solution obtained by mixing 0.5 parts of formaldehyde sodium bisulfite and 50 parts of water in 2 hours, continue to react for 0.5 hours after the solution is added completely, adjust the pH value to 5-6 by adding 30% sodium hydroxide solution after the reaction is completed, and the anhydride low sensitivity polycarboxylic acid water reducing agent is obtained.

[0105] The product structure is: n is in the range of 58-62, e:f:g = (1.5-4.0):1:(2.0-4.0).

[0106] Comparative example 1

[0107] A preparation method of a polycarboxylic acid water reducing agent, specifically:

[0108] Select 40 parts of maleic anhydride and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water by mass fraction, add 3 parts of sodium hypophosphite, 5.0 parts of hydrogen peroxide, 0.02 parts of catalyst ferrous sulfate heptahydrate, mix well and dissolve, keep the reaction temperature in the reaction vessel at 55-80℃, add the mixed solution obtained by mixing 0.5 parts of formaldehyde sodium bisulfite and 50 parts of water in 2 hours, continue to react for 0.5 hours after the solution is added completely, adjust the pH value to 5-6 by adding 30% sodium hydroxide solution after the reaction is completed, and the polycarboxylic acid water reducing agent is obtained.

[0109] Comparative example 2

[0110] A preparation method of a polycarboxylic acid water reducing agent, specifically:

[0111] Select 45 parts of maleic anhydride and 360 parts of isopentenyl alcohol polyoxyethylene ether and 260 parts of water by mass fraction, add 5.0 parts of hydrogen peroxide, 0.02 parts of catalyst ferrous sulfate heptahydrate, mix well and dissolve, keep the reaction temperature in the reaction vessel at 70-80℃, add the mixed solution obtained by mixing 0.5 parts of succinic acid dioctyl sulfonate sodium and 50 parts of water in 3 hours, continue to react for 0.5-1.0 hours after the solution is added completely, adjust the pH value to 5-6 by adding 30% sodium hydroxide solution after the reaction is completed, and the polycarboxylic acid water reducing agent is obtained.

[0112] The molecular structure of comparative example 1 and comparative example 2 is as follows, in the structure, n is in the range of 58-62, b:a = 1:(2-4)

[0113]

[0114] In the application examples, the cement used is Portland cement (P.O 42.5) unless otherwise specified. In order to compare the dispersing performance and dispersion retention performance of the water reducing agent prepared in the application, the cement paste fluidity test was carried out according to the GB / T8077-2012 standard, 300 g of cement was added with 87 g of water, and the cement paste fluidity was measured on a flat glass plate after stirring for 4 minutes, and the paste fluidity at different times and the rotary viscosity of the cement paste 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 examples, the product of the application can significantly reduce the rotary viscosity of the cement paste.

[0119] Each example and comparative example was subjected to gel permeation chromatography (GPC) detection. According to the area of the main peak, the size of the monomer conversion rate of the product can be directly observed, and the molecular weight of the product can also be detected. It can be seen that the monomer conversion rate prepared in each example is high.

[0120] The above examples are described in order to facilitate the understanding and use of the application by those of ordinary skill in the art. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without having to go through creative labor. Therefore, the present application is not limited to the above examples, and improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for preparing an acid anhydride low-sensitivity polycarboxylic acid water reducing agent, characterized by, The preparation method comprises the following steps: 1) mixing maleate with ethylene oxide and a catalyst, and performing a heating and pressurizing reaction under a protective atmosphere to obtain an intermediate; 2) mixing maleate, the intermediate prepared in step 1), isoprenol polyoxyethylene ether and water, adding a chain transfer agent, an oxidizing agent and a catalyst, and then adding an aqueous solution of a reducing agent dropwise, adjusting the pH value to 5-6 by adding sodium hydroxide solution after the reaction is completed, to obtain an anhydride low-sensitivity polycarboxylic acid water reducer; In step 2), the maleate is one or more of methyl maleate and ethyl maleate; and the intermediate is one or more of the intermediates prepared from methyl maleate or ethyl maleate in step 1).

2. The production method according to claim 1, characterized by, In step 1), the molar ratio of the maleate to the ethylene oxide is 1:1.

05. In step 1), the mass ratio of the maleate to the catalyst is 200:

1.

3. The preparation method according to claim 1, characterized in that, In step 1), the heating and pressurizing reaction is performed at 100-120 ℃ for 2 h under a pressure of 0.2-0.3 MPa.

4. The method of claim 1, wherein, In step 1), the maleate is prepared by the following method: in step 1), the maleate is prepared by the following method: the alcohol is first heated to 60-65 ℃, and stirring is started; maleic anhydride is added in three portions with an interval of 5-10 min, and the internal temperature is controlled to be lower than 85 ℃; after the maleic anhydride is completely melted, the temperature is increased to 95 ℃, and the reaction is performed for 120-150 min to obtain the maleate.

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

6. The method of claim 1, wherein, In step 2), the reaction is performed at 20-30 ℃, the aqueous solution of the reducing agent is added dropwise within 2.0-3.0 h, and the reaction is continued for 0.5 h after the dropwise addition is completed.

7. The anhydride low-sensitivity polycarboxylic acid water reducer prepared by the preparation method in claim 1.

8. Use of the anhydride low-sensitizing polycarboxylate water reducer of claim 7, characterized in that, For concrete.

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