CN114539522B

CN114539522B - Method for synthesizing branched polyethyleneimine without catalyst

Info

Publication number: CN114539522B
Application number: CN202210212872.9A
Authority: CN
Inventors: 谢兴益; 张文
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2023-05-02
Anticipated expiration: 2042-03-04
Also published as: CN114539522A

Abstract

The invention discloses a method for preparing polyethyleneimine without adding an acid catalyst. The method comprises the following process steps and conditions: 1 molar part of EI is dissolved in water to make the mass concentration of the EI be 10 to 50 percent, 0 to 0.1 molar part of compound containing active hydrogen is added, and the EI is reacted for 12 to 36 hours at the temperature of 50 to 120 ℃; the active hydrogen-containing compound is at least one of ethylenediamine, ethanolamine, piperazine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine; the resulting reaction mixture was then dehydrated under reduced pressure and dried in vacuo to give a transparent viscous liquid-like product.

Description

Method for synthesizing branched polyethyleneimine without catalyst

Technical Field

The invention relates to the technical field of high molecular synthesis, in particular to a method for preparing polyethyleneimine.

Background

Polyethyleneimines (PEI) are widely used high-performance materials, and the molecular structure of polyethyleneimines contains groups such as primary amine, secondary amine, tertiary amine and the like, and are currently known polymers with highest amino density, and organic polymers with highest cation density are formed after protonation. PEI has important application in the fields of biomedicine, environmental protection, electronics, polyurethane foam and the like.

The current PEI production process is mainly achieved by ring-opening polymerization of Ethyleneimine (EI) under acidic conditions. The acid usually used is hydrochloric acid, and the added acid needs to be neutralized by adding a base after the polymerization is completed to generate a small amount of salt (such as sodium chloride), which needs to be desalted by dialysis, membrane separation and other techniques, thus causing cost increase.

Disclosure of Invention

The invention aims at overcoming the defects of the prior art and provides a novel method for synthesizing polyethyleneimine without adding a catalyst.

The inventor discovers through research that EI water solution can be subjected to ring-opening polymerization to obtain PEI polymer at high temperature, thereby laying the foundation of the invention. Meanwhile, other compounds containing active hydrogen, such as ethanolamine, ethylenediamine, piperazine and the like, can also initiate ring-opening polymerization of EI at high temperature.

In order to achieve the purpose of the invention, the invention adopts the following technical scheme:

(1) 1 molar part of EI is dissolved in water to make the mass concentration of the EI be 10 to 50 percent, 0 to 0.1 molar part of compound containing active hydrogen is added, and the EI is reacted for 12 to 36 hours at the temperature of 50 to 120 ℃; the active hydrogen-containing compound is at least one of ethylenediamine, ethanolamine, piperazine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine;

(2) And (3) carrying out the steps of decompression, dehydration, vacuum drying and the like on the mixture obtained in the step (1) to obtain a transparent viscous liquid product.

In the above-mentioned step (2), both the dehydration under reduced pressure and the vacuum drying are conventional operations. If some applications only require an aqueous solution of PEI (e.g., PEI flocculant), the product of the first step synthesis is cooled to obtain the product.

The active hydrogen-containing compound is mainly added in the scheme to obtain PEI with terminal amino groups, if the active hydrogen-containing compound is not added; the resulting PEI should contain an ethyleneimine ring, a piperazine ring, or a larger ethyleneamine containing ring.

Compared with the prior art, the invention has the following positive effects: the method for synthesizing PEI does not need a catalyst, omits the step of removing the catalyst in the conventional synthesis method of PEI, and has the advantages of high purity of the obtained product, lower cost and easy industrial production.

Drawings

FIG. 1 shows the nuclear magnetic resonance hydrogen spectra of polyethyleneimine prepared in examples 1 and 2.

FIG. 2 shows the nuclear magnetic resonance carbon spectra of polyethyleneimine prepared in examples 1 and 2.

FIG. 3 is a low resolution mass spectrum of polyethyleneimine prepared in example 1. Italic values are theoretical values.

FIG. 4 is a low resolution mass spectrum of polyethyleneimine prepared in example 2. Italic values are theoretical values.

Detailed Description

The invention is further illustrated by the following examples, which are provided to illustrate the practice and effect of the invention and are not to be construed as limiting the invention in any way.

Example 1

1 mol of EI (43.07 g) was dissolved in water to a mass concentration of 45%, and reacted at 100℃for 24 hours, the resultant mixture was decompressed to remove water, and vacuum drying was continued at 50℃for 24 hours to obtain a transparent oily viscous material having a molecular weight of 25 kDa as measured by the Ubbelohde viscosity method.

Example 2

1 mol of EI (43.07 g) is dissolved in water with the mass concentration of 30%, 0.1 mol of ethylenediamine is added, the reaction is carried out for 36 hours at 50 ℃, the obtained mixture is decompressed to remove the water, the vacuum drying is continued for 24 hours at 50 ℃ to obtain transparent oily sticky substance, and the molecular weight is 6.2k Da by using the Ubbelohde viscosity method.

Example 3

1 mol of EI (43.07 g) was dissolved in water at a mass concentration of about 20%, 0.01 mol of ethanolamine was added, and the resultant mixture was reacted at 80℃for 36 hours, and the water was removed under reduced pressure, and vacuum drying was continued at 50℃for 24 hours to obtain a transparent oily viscous material having a molecular weight of 10.5 kDa as measured by the Ubbelohde viscosity method.

Example 4

1 mol of EI (43.07 g) was dissolved in water at a mass concentration of about 10%, piperazine was added in an amount of 0.02 mol, and the resultant mixture was reacted at 120℃for 12 hours, and the water was removed under reduced pressure, and vacuum drying was continued at 50℃for 24 hours to obtain a transparent oily viscous material having a molecular weight of 8.3 kDa as measured by the Ubbelohde viscosity method.

Example 5

1 mol of EI (43.07 g) was dissolved in water at a mass concentration of about 50%, diethylenetriamine 0.06 mol was added, the resultant mixture was reacted at 110℃for 12 hours, the water was removed under reduced pressure, and vacuum drying was continued at 50℃for 24 hours to obtain a transparent oily viscous material having a molecular weight of 4.5 kDa as measured by the Ubbelohde viscosity method.

The molecular weight of the obtained polymer is measured by the Ubbelohde viscosity method, the internal diameter of the Ubbelohde viscometer is 0.4-0.5mm, and the testing conditions are as follows: the polymer was dissolved with 0.5M sodium chloride solution to a polymer concentration of 2-4g/dL and tested in a constant temperature water bath at 32 ℃.

FIG. 1 is a nuclear magnetic resonance spectrum of PEI prepared in examples 1 and 2 showing N-CH in PEI structure ₂ Proton peaks of (2). The nuclear magnetic carbon spectrum of fig. 2 shows the signal peaks of the eight carbons of the branched PEI. FIG. 3 is a mass spectrum of PEI prepared in example 1, showing that the molecular weight of the PEI obtained is an integer multiple (43.04 n) of the molecular weight of monomer EI, indicating that the PEI obtained contains at least one ring (ethyleneimine ring, piperazine ring or larger ring) in its structure. In addition, there is a small amount of molecular peak (x) of PEI obtained by ring opening EI of ethanolamine, which indicates that a small amount of EI reacts with water at high temperature to form ethanolamine, and finally enters into the molecular structure of PEI. FIG. 4 is a mass spectrum of PEI prepared in example 2, showing that most of PEI molecules are obtained by ring-opening EI monomers of ethylenediamine, and that the ring-opening reaction of ethylenediamine and EI is performed to obtain PEI without a cyclic structure.

Claims

1. A method for preparing polyethyleneimine without catalyst is characterized by comprising the following process steps and conditions:

(1) Dissolving 1 molar part of ethylenimine into water to make the mass concentration of the ethylenimine be 10% -50%, adding 0-0.1 molar part of active hydrogen-containing compound, and reacting for 12-36 hours at 100-120 ℃; the active hydrogen-containing compound is at least one of ethylenediamine, ethanolamine, piperazine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine;

(2) And (3) carrying out decompression dehydration and vacuum drying on the mixture obtained in the step (1) to obtain a transparent viscous liquid product.