Preparation method of pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer

Abstract

The invention discloses a preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer, belonging to the technical fields of concrete materials and concrete admixtures. The preparation method of the pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer of the invention comprises the following steps: mixing pyromellitic dianhydride and polyethylene glycol monomethyl ether, and carrying out an esterification reaction to obtain the pyromellitic acid-terminated polyethylene glycol monomethyl ether material. The esterification reaction of the invention is a reaction between pyromellitic dianhydride with two acid anhydrides having strong electron-withdrawing effects and polyethylene glycol monomethyl ether with nucleophilic hydroxyl groups; since the acid anhydride activity of the first reaction of pyromellitic dianhydride in the invention is higher than that of the second reaction, pyromellitic dianhydride can highly selectively generate a monoester product, the reaction efficiency is relatively high, the chemical stability of the monoester product is good, and the by-products are less.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete materials and concrete admixtures, and particularly to a preparation method of a pyromellitic acid-terminated 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 shaping processes of concrete, and affect 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 properties of concrete after hardening, including mechanical properties and durability. Although reducing the water-binder ratio will increase the strength and durability of concrete, it will also increase the plastic viscosity of fresh concrete, resulting in that fresh concrete usually requires a longer flow time, easily leading 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-binder ratio. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer to solve the above problems in the background art. The esterification reaction of the present invention is a reaction between pyromellitic dianhydride with two strongly electron-withdrawing acid anhydrides and polyethylene glycol monomethyl ether with a nucleophilic hydroxyl group; since the acid anhydride activity of the first reaction of pyromellitic dianhydride in the present invention is higher than that of the second reaction, pyromellitic dianhydride can highly selectively generate a monoester product, with a higher reaction efficiency, good chemical stability of the monoester product and fewer by-products.

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

[0005] One of the technical solutions of the present invention: provides a preparation method of a pyromellitic acid-terminated polyethylene glycol monomethyl ether material, comprising the following steps:

[0006] Mix pyromellitic dianhydride and polyethylene glycol monomethyl ether, and carry out an esterification reaction to obtain the pyromellitic acid-terminated 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 dianhydride to polyethylene glycol monomethyl ether is 1:1.1 - 1:1.5.

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

[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] In the present invention, by hydrolyzing the esterification reaction product under alkaline conditions, a polyethylene glycol monomethyl ether viscosity reducer containing three carboxyl end groups can be obtained. The product that is only esterified and not hydrolyzed will undergo an acid anhydride hydrolysis reaction under alkaline conditions during the preparation of fresh concrete to generate two carboxylate groups. The newly generated carboxylate groups will undergo a neutralization reaction with the base to generate carboxylate anions and other processes. However, the product treated by alkaline hydrolysis can directly play a role. The three exposed carboxylate anions can quickly adsorb on the surface of cement particles, achieving the effect of reducing the viscosity of fresh concrete, and the effect is better than that of the product without hydrolysis treatment.

[0016] The second technical solution of the present invention: 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: Provide an application of the above pyromellitic acid-terminated polyethylene glycol monomethyl ether material in the field of concrete viscosity reducers.

[0018] The pyromellitic acid-terminated polyethylene glycol monomethyl ether material after hydrolysis treatment in the present invention contains three negatively charged carboxylate ions, so it can be quickly adsorbed on the surface of cement particles. The polyethylene glycol monomethyl ether long chain plays a role of steric hindrance, preventing cement particles from approaching each other, and 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 method for preparing end-group pyromellitic acid polyether. By using the nucleophilic addition-elimination reaction between the anhydride of pyromellitic dianhydride and the hydroxyl group of methoxypolyethylene glycol, the monoester product of pyromellitic dianhydride and methoxypolyethylene glycol is obtained with high efficiency and high selectivity, converting pyromellitic dianhydride into pyromellitic dianhydride monoester. The present invention uses the esterification reaction between anhydride and hydroxyl group to graft pyromellitic dianhydride onto the end group of methoxypolyethylene glycol, converting anhydride into equivalent ester groups and carboxyl groups. The reaction has the advantages of high reaction efficiency, strong product selectivity, simple reaction conditions, and high structural stability.

[0021] The esterification reaction of the present invention is a reaction between pyromellitic dianhydride with two strongly electron-withdrawing anhydrides and methoxypolyethylene glycol with a nucleophilic hydroxyl group; since the anhydride activity of the first reaction of pyromellitic dianhydride in the present invention is higher than that of the second reaction, pyromellitic dianhydride can generate monoester products with high selectivity, the reaction efficiency is relatively high, the monoester product has good chemical stability, and there are fewer by-products.

[0022] The preparation method of the present invention has the characteristics of good atom economy, easy availability of raw materials, no need for auxiliary catalysts and solvents, and few by-products. The pyromellitic dianhydride end-group single-chain methoxypolyethylene glycol concrete viscosity reducer of the present invention has excellent viscosity reduction effect. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is the 1H NMR spectrum of the product of Example 2. Detailed Description of the Embodiments

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

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

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

[0028] Regarding "comprising", "including", "having", "containing", etc. used in this invention, they are all open-ended terms, meaning including but not limited to.

[0029] All raw materials used in the following examples and comparative examples of this 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] Mix 40 g of pyromellitic dianhydride and 77 g of polyethylene glycol monomethyl ether 350, stir well at 60 °C for 2 h, and add water to prepare a solution with a solid mass fraction of 40% to obtain a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer. It is measured that its yield is 97.6%, and the mass content of the active ingredient (i.e., pyromellitic dianhydride monoester) accounts 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] Mix 10 g of pyromellitic dianhydride and 101 g of polyethylene glycol monomethyl ether 2000 (molar ratio is about 1:1.1), stir well at 130 °C for 4 h, and add water to prepare a solution with a solid mass fraction of 40% to obtain a pyromellitic acid-terminated polyethylene glycol monomethyl ether concrete viscosity reducer. It is measured that its yield is 99.0%, and the mass content of the active ingredient accounts 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] Mix 20 g of pyromellitic dianhydride with 110 g of methoxypolyethylene glycol 1000 (molar ratio is about 1:1.2), stir well at 90 °C for 6 h, add water to prepare a solution with a solid mass fraction of 40%, then dissolve the reaction system in 130 g of water, and carry out hydrolysis by adjusting the pH value of the reaction system to 7 by adding sodium hydroxide solution (30 wt%), then continue to add water until the total mass of water is 195 g to obtain a concrete viscosity reducer solution with a concentration of 40% of the polyethylene glycol monomethyl ether with pyromellitic acid end groups. It is measured that the yield is 98.1%, and the mass content of the active ingredient accounts for 27.5% of the viscosity reducer solution.

[0039] Comparative Example 1

[0040] Mix 40 g of maleic anhydride with 77 g of methoxypolyethylene glycol 350, stir well at 60 °C for 2 h, add water to prepare a solution with a solid mass fraction of 40% to obtain the final product. It is measured that the yield is 98.2%, and the mass content of the active ingredient accounts for 33.6% of the viscosity reducer solution.

[0041] Effect verification

[0042] (1) Use a nuclear magnetic resonance instrument with a frequency of 400 MHz, and use deuterated chloroform as the solvent to test the 1H NMR spectrum of the product of Example 2. The results are as Figure 1 shown.

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

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

[0045] (2) According to JGJ / T 283-2012 "Technical Application Regulations for Self-Compacting Concrete", carry out the work performance test of cement concrete. Modify by mixing the samples of each example and comparative example with a commercially available water reducer as a modifier and adding it to the concrete (the mass ratio of the sample to the commercially available water reducer is 1:10) to verify the relevant modification effects, and compare the performance with the scheme of adding methoxypolyethylene glycol 1000; the commercially available water reducer used is GK-3000 from Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.

[0046] Among them, the water-binder ratio of the concrete is 0.27, and the initial slump is controlled to 650±5 mm. The admixture dosage of the water reducer and the concrete mix ratio are shown in Table 1, and the test results of the concrete performance 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] It can be seen from Table 2 that on the basis of the same slump (650±5 mm), the samples of Examples 1-3 of the present invention can effectively shorten the V-groove flow time and the upending time. Thus, compared with the reference group (GK-3000 group) without using the viscosity reducer of the present invention, adding 10 wt% 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 do not decrease significantly, and the 28-day strength does not decrease. Compared with the scheme 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 dianhydride end-group single-chain polyethylene glycol monomethyl ether concrete viscosity reducer of the present invention has excellent viscosity reduction effect.

[0053] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. Application of a pyromellitic acid-terminated polyethylene glycol monomethyl ether material in the field of concrete viscosity reducers, characterized in that, The preparation method of the pyromellitic acid-terminated methoxypolyethylene glycol material comprises the following steps: Mix pyromellitic dianhydride and methoxypolyethylene glycol, and carry out an esterification reaction to obtain the pyromellitic acid-terminated methoxypolyethylene glycol material; The molar ratio of the pyromellitic dianhydride to the methoxypolyethylene glycol is 1:1.1 - 1:1.5; After the esterification reaction, a hydrolysis step is further included; the hydrolysis is carried out by adjusting the pH value of the reaction system to 7 - 9.

2. The application according to claim 1, wherein The molecular weight of the methoxypolyethylene glycol is 350 - 5000.

3. The application according to claim 1, characterized in that, The temperature of the esterification reaction is 50 - 150 °C, and the time is 2 - 6 h.

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