Preparation method of pyromellitic acid-terminated methoxypolyethylene glycol concrete viscosity reducer

Abstract

The invention discloses a preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer, and belongs to the technical field of concrete materials and concrete admixtures. The preparation method of the pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer comprises the following steps: mixing pyromellitic anhydride and polyethylene glycol monomethyl ether, and carrying out esterification reaction to obtain the pyromellitic acid-terminated polyethylene glycol monomethyl ether material. According to the invention, the esterification reaction is a reaction between pyromellitic dianhydride with two anhydrides with strong electron withdrawing effects and methoxypolyethylene glycol with nucleophilic hydroxyl groups; the acid anhydride activity of the first reaction of the pyromellitic dianhydride is higher than that of the second reaction of the pyromellitic dianhydride, so that the pyromellitic dianhydride can generate the monoester product with high selectivity, the reaction efficiency is higher, the chemical stability of the monoester product is good, and fewer byproducts are generated.

Description

Technical Field

[0001] The invention relates to the technical field of concrete materials and concrete admixtures, in particular to a method for preparing a pyromellitic acid terminal polyethylene glycol monomethyl ether concrete viscosity reducer. Background Art

[0002] Concrete is a widely used civil engineering material. The rheological properties of fresh concrete, namely plastic viscosity and yield stress, are very important for the pouring and forming process of concrete, affecting workability, consistency, fluidity, pumpability, etc. Processing techniques such as pumping, pouring, spreading or spraying, as well as properties such as self-leveling, forming or self-compacting are closely related to rheological properties. At the same time, the rheological properties of fresh concrete also greatly affect the performance of concrete after hardening, including mechanical properties and durability. Although reducing the water-cement ratio will increase the strength and durability of concrete, it will also increase the plastic viscosity of fresh concrete, resulting in fresh concrete usually requiring longer flow time, which is prone to insufficient formwork filling, low work efficiency, and increased energy consumption. Therefore, finding an effective viscosity reducer is very important for the preparation of high-performance concrete with a low water-cement ratio. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a concrete viscosity reducer containing polyethylene glycol monomethyl ether terminated with pyromellitic acid, so as to solve the above-mentioned problems in the background technology. The esterification reaction of the present invention is a reaction between pyromellitic anhydride with two strong electron-withdrawing anhydrides and polyethylene glycol monomethyl ether with nucleophilic hydroxyl groups; since the anhydride activity of the first reaction of pyromellitic anhydride in the present invention is higher than the anhydride activity of the second reaction, pyromellitic anhydride can generate a monoester product with high selectivity, the reaction efficiency is high, the monoester product has good chemical stability, and less by-products.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention is to provide a method for preparing a pyromellitic acid-terminated polyethylene glycol monomethyl ether material, comprising the following steps:

[0006] The pyromellitic anhydride and polyethylene glycol monomethyl ether are mixed and subjected to esterification reaction to obtain the pyromellitic acid terminal polyethylene glycol monomethyl ether material.

[0007] Preferably, the molecular weight of the polyethylene glycol monomethyl ether is 350-5000.

[0008] Preferably, the molar ratio of pyromellitic anhydride to polyethylene glycol monomethyl ether is 1:1.1-1:1.5.

[0009] Preferably, the esterification reaction temperature is 50-150° C. and the time is 2-6 hours.

[0010] Preferably, after the esterification reaction is completed, a hydrolysis step is further included.

[0011] Preferably, the hydrolysis is carried out by adjusting the pH value of the reaction system to 7-9.

[0012] Preferably, the pH value of the reaction system is adjusted by adding sodium hydroxide and / or potassium hydroxide.

[0013] The reaction formula for preparing the pyromellitic acid-terminated polyethylene glycol monomethyl ether material is as follows:

[0014]

[0015] The present invention can obtain a polyethylene glycol monomethyl ether viscosity reducer containing three carboxyl terminal groups by hydrolyzing the esterification reaction product under alkaline conditions. The product that is only esterified but not hydrolyzed will undergo an anhydride hydrolysis reaction under alkaline conditions to generate two carboxyl groups during the preparation of fresh concrete, and the newly generated carboxyl groups will undergo a neutralization reaction with the alkali to generate carboxylate anions and the like. The product that has been hydrolyzed under alkaline conditions can directly play a role, and the three exposed carboxylate anions can be quickly adsorbed onto the surface of cement particles, thereby reducing the viscosity of the fresh concrete, and the effect is better than that of the product that has not been hydrolyzed.

[0016] The second technical solution of the present invention is to provide a pyromellitic acid-terminated polyethylene glycol monomethyl ether material obtained according to the above preparation method.

[0017] The third technical solution of the present invention is to provide an application of the above-mentioned pyromellitic acid-terminated polyethylene glycol monomethyl ether material in the field of concrete viscosity reducers.

[0018] The hydrolyzed pyromellitic acid-terminated polyethylene glycol monomethyl ether material of the present invention contains three negatively charged carboxylate ions, so it can be quickly adsorbed on the surface of cement particles. The long chain of polyethylene glycol monomethyl ether plays a role of steric hindrance, preventing cement particles from approaching each other, thereby greatly reducing the viscosity of the concrete system.

[0019] The beneficial technical effects of the present invention are as follows:

[0020] The present invention designs a simple and efficient preparation method of terminal pyromellitic acid polyether, which utilizes the nucleophilic addition-elimination reaction of the anhydride of pyromellitic anhydride and the hydroxyl group of polyethylene glycol monomethyl ether to obtain the monoester product of pyromellitic anhydride and polyethylene glycol monomethyl ether with high efficiency and high selectivity, so that pyromellitic anhydride is converted into pyromellitic anhydride monoester. The present invention adopts the esterification reaction of the anhydride and the hydroxyl group to graft the pyromellitic anhydride onto the terminal group of polyethylene glycol monomethyl ether, so that the anhydride is converted into an equivalent ester group and a carboxyl group, and the reaction has the advantages of high reaction efficiency, strong product selectivity, simple reaction conditions, high structural stability, etc.

[0021] The esterification reaction of the present invention is a reaction between pyromellitic anhydride having two strong electron-withdrawing anhydrides and polyethylene glycol monomethyl ether having a nucleophilic hydroxyl group; since the anhydride activity of the first reaction of pyromellitic anhydride in the present invention is higher than the anhydride activity of the second reaction, pyromellitic anhydride can generate a monoester product with high selectivity, the reaction efficiency is high, the monoester product has good chemical stability and less by-products.

[0022] The preparation method of the invention has the characteristics of good atom economy, easy raw materials, no need for auxiliary catalysts and solvents, and few by-products. The pyromellitic anhydride terminal single-chain polyethylene glycol monomethyl ether concrete viscosity reducer of the invention has excellent viscosity reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is the H NMR spectrum of the product of Example 2. DETAILED DESCRIPTION

[0025] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0026] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0029] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0030] Example 1

[0031] A preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer:

[0032] 40g of pyromellitic anhydride and 77g of polyethylene glycol monomethyl ether 350 were mixed, stirred at 60°C for 2h, and water was added to prepare a solution with a solid mass fraction of 40%, thereby obtaining a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer. The yield was measured to be 97.6%, and the mass content of the effective component (i.e., pyromellitic anhydride monoester) accounted for 28.5% of the viscosity reducer solution.

[0033] Example 2

[0034] A preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer:

[0035] 10g of pyromellitic anhydride and 101g of polyethylene glycol monomethyl ether 2000 were mixed (molar ratio of about 1:1.1), stirred at 130°C for 4h, and water was added to prepare a solution with a solid mass fraction of 40%, thereby obtaining a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer. The yield was measured to be 99.0%, and the mass content of the effective component accounted for 33.0% of the viscosity reducer solution.

[0036] Example 3

[0037] A preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer:

[0038] 20g of pyromellitic anhydride and 110g of polyethylene glycol monomethyl ether 1000 were mixed (molar ratio of about 1:1.2), stirred at 90°C for 6h, and water was added to prepare a solution with a solid mass fraction of 40%. The reaction system was then dissolved in 130g of water, and the pH value of the reaction system was adjusted to 7 by adding sodium hydroxide solution (30wt%) for hydrolysis, and then water was continued to be added until the total mass of water was 195g, to obtain a concrete viscosity reducer solution with a concentration of 40% of pyromellitic acid end group polyethylene glycol monomethyl ether. It was measured that the yield was 98.1%, and the mass content of the effective component accounted for 27.5% of the viscosity reducer solution.

[0039] Comparative Example 1

[0040] 40g of maleic anhydride and 77g of polyethylene glycol monomethyl ether 350 were mixed, stirred at 60°C for 2h, and water was added to prepare a solution with a solid mass fraction of 40% to obtain the final product. The yield was measured to be 98.2%, and the mass content of the active ingredient accounted for 33.6% of the viscosity reducer solution.

[0041] Effect verification

[0042] (1) Using a 400 MHz nuclear magnetic resonance instrument and deuterated chloroform as solvent, the nuclear magnetic resonance hydrogen spectrum test of the product of Example 2 was performed. The results are as follows: Figure 1 shown.

[0043] Figure 1 This is the H NMR spectrum of the product of Example 2.

[0044] Depend on Figure 1 It can be seen that there is no reactant at around chemical shift 8.7, and the benzene ring hydrogen peak of pyromellitic anhydride indicates that all the pyromellitic anhydride has reacted, and the conversion rate is 100%; the integral area ratio of b and d is 2:3, indicating that the polyethylene glycol monomethyl ether has reacted completely, and the conversion rate is 100%. Therefore, the product structure represented by this H-NMR spectrum is the monoester of pyromellitic anhydride and polyethylene glycol monomethyl ether: the diester of pyromellitic anhydride and polyethylene glycol monomethyl ether = 9:1 (molar ratio), that is, the mass fraction of the active ingredient is 82.6%.

[0045] (2) According to JGJ / T283-2012 "Technical Application Specifications for Self-compacting Concrete", the working performance test of cement concrete was carried out. The samples of each embodiment and comparative example were mixed with a commercially available water-reducing agent as a modifier and added to the concrete (the mass ratio of the sample to the commercially available water-reducing agent was 1:10) to verify the relevant modification effect, and the performance was compared with the scheme of adding polyethylene glycol monomethyl ether 1000; the commercially available water-reducing agent used was selected from GK-3000 of Shijiazhuang Changan Yucai Building Materials Co., Ltd.

[0046] The water-cement ratio of the concrete is 0.27, and the initial expansion is controlled to 650±5mm. The water-reducing agent dosage and concrete mix ratio are shown in Table 1, and the concrete performance test results are shown in Table 2.

[0047] Table 1 Concrete mix ratio

[0048] W C SF F S G5-10 mm G10-20 mm 150 470 40 40 830 655 280

[0049] In Table 1, W represents water, C represents cement, SF represents silica fume, F represents fly ash, S represents sand, G5-10 mm represents gravel with a particle size of 5-10 mm, and G10-20 mm represents gravel with a particle size of 10-20 mm.

[0050] Table 2 Concrete test results

[0051]

[0052] As can be seen from Table 2, on the basis of the same extension (650 ± 5mm), the samples of Examples 1-3 of the present invention can effectively shorten the V-groove flow time and the inverted lifting time. It can be seen that compared with the benchmark group (GK-3000 group) without using the viscosity reducer of the present invention, adding 10wt% of the viscosity reducer of the present invention to the modifier can reduce the plastic viscosity of the fresh concrete. In addition, while reducing the plastic viscosity of the fresh concrete system, the 3-day strength and 7-day strength of the concrete did not significantly decrease, and the 28-day strength did not decrease. Compared with the solution of adding polyethylene glycol monomethyl ether 1000 and comparative example 1, Examples 1-3 of the present invention effectively reduce the plastic viscosity of the fresh concrete. Therefore, the pyromellitic anhydride end group single-chain polyethylene glycol monomethyl ether concrete viscosity reducer of the present invention has an excellent viscosity reduction effect.

[0053] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a pyromellitic acid-terminated polyethylene glycol monomethyl ether material, characterized in that: The following steps are involved: The pyromellitic anhydride and polyethylene glycol monomethyl ether are mixed and subjected to esterification reaction to obtain the pyromellitic acid terminal polyethylene glycol monomethyl ether material.

2. The preparation method according to claim 1, characterized in that: The molecular weight of the polyethylene glycol monomethyl ether is 350-5000.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the pyromellitic anhydride to polyethylene glycol monomethyl ether is 1:1.1-1:1.

5.

4. The preparation method according to claim 1, characterized in that: The temperature of the esterification reaction is 50-150° C. and the time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that: After the esterification reaction is completed, a hydrolysis step is also included.

6. The preparation method according to claim 5, characterized in that: The hydrolysis is carried out by adjusting the pH value of the reaction system to 7-9.

7. A pyromellitic acid-terminated polyethylene glycol monomethyl ether material obtained according to the preparation method according to any one of claims 1 to 6.

8. Use of the pyromellitic acid-terminated polyethylene glycol monomethyl ether material according to claim 7 in the field of concrete viscosity reducers.

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