CN114479069B

CN114479069B - Novel method for directly synthesizing branched polyethyleneimine from haloethylamine

Info

Publication number: CN114479069B
Application number: CN202210218652.7A
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: 2023-03-31
Anticipated expiration: 2042-03-04
Also published as: CN114479069A

Abstract

The invention discloses a new method for synthesizing branched polyethyleneimine, which comprises the following process steps and conditions: dissolving 1 mol part of 2-halogen ethylamine hydrohalic acid salt in water to ensure that the mass concentration of the 2-halogen ethylamine hydrohalic acid salt is 10-50%, adding 1.8-2.3 mol parts of alkali, and reacting for 0-24 hours at the temperature of 5-50 ℃; then reacting for 12-48 hours at 50-120 ℃; desalting, decompressing and dehydrating the obtained mixture, vacuum drying and the like to obtain a transparent viscous liquid product. The halogen in the 2-halogen ethylamine hydrohalic acid salt is at least one of chlorine and bromine, and the alkali is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide.

Description

Novel method for directly synthesizing branched polyethyleneimine from haloethylamine

Technical Field

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

Background

Polyethyleneimine (PEI) is a widely used high-performance material, and the molecular structure of polyethyleneimine contains primary amine, secondary amine, tertiary amine and other groups, and is a currently known high polymer with the highest amine density, and an organic high polymer with the highest cation density is formed after protonation. PEI has important applications in the fields of biomedicine, environmental protection, electronics, polyurethane foam and the like.

The prior PEI production method is mainly obtained by ring opening polymerization of Ethyleneimine (EI) under acidic conditions. Abroad only BASF in germany and japanese catalytic chemistry can be produced. The monomer EI is prepared by a complex preparation process, can be prepared by performing esterification on ethanolamine and sulfuric acid and then performing cyclization on sodium hydroxide, and can also be prepared by reacting chloroethylamine and sodium hydroxide. EI is a highly toxic substance, and its half Lethal Dose (LD) is orally administered to rats ₅₀ ) At 14mg/kg, the mice inhaled a semi-Lethal Concentration (LC) within 10min ₅₀ ) 2236ppm; EI boiling point was 57 ℃ and saturated vapor pressure at 25 ℃ was 28.5kPa (equivalent to 28.1% by weight of EI gas in air, as the LC ₅₀ 126 times of! ) That is, as long as the EI liquid is open to the air, its vapor concentration is sufficient to kill (mice)! Therefore, the industry producing PEI must be very careful, and must store, transport, and use the monomer EI in a fully enclosed system. And because of the high corrosiveness of EI, no gasket material can bear the long-term contact with EI without leakage, therefore EI metering pump and delivery valve must adopt gasket-free sealing! This requires special equipment to meet the requirements. Therefore, a better method for synthesizing polyethyleneimine is urgently needed.

Disclosure of Invention

The invention aims to provide a novel method for synthesizing polyethyleneimine aiming at the defects of the prior art.

The inventors have noted that 2-haloethylamine ("halo" is either bromo or chloro, and so on) can undergo intramolecular or intermolecular dehydrohalogenation under alkaline conditions, the former producing cyclic monomeric Ethyleneimine (EI) and the latter producing Polyethyleneimine (PEI) oligomers. The traditional method is to separate the two to obtain pure EI, and then to polymerize under acidic condition to obtain PEI. We have found that under high temperature alkaline conditions, the amine groups of PEI oligomers can still undergo ring-opening polymerization with EI to give PEI with high molecular weight. Other active hydrogen-containing compounds, such as ethanolamine, ethylenediamine, piperazine, etc., can also initiate the ring-opening polymerization of EI at high temperatures. Based on this discovery, we propose to polymerize PEI directly from 2-haloethylamine, eliminating the need for separation and storage of the toxic monomer EI, simplifying the polymerization procedure, and allowing for a significant reduction in the production cost of PEI.

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

(1) Dissolving 1 mol part of 2-halogen ethylamine hydrohalic acid salt in water to ensure that the mass concentration of the 2-halogen ethylamine hydrohalic acid salt is 10-50%, adding 1.8-2.3 mol parts of alkali, and reacting for 0-24 hours at the temperature of 5-50 ℃; then reacting for 12-36 hours at 50-120 ℃; the halogen in the 2-halogen ethylamine hydrohalic acid salt is at least one of chlorine and bromine, and the alkali is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide;

(2) And (3) desalting the mixture obtained in the step (1), dehydrating under reduced pressure, drying in vacuum and the like to obtain a transparent viscous liquid product.

It is to be noted that the "2-haloethylamine hydrohalide salt" when the "halogen" is "chlorine", the "2-chloroethylamine hydrochloride" is generally named "2-chloroethylamine hydrochloride", the latter being employed in the present invention.

Further, the 2-halogen ethylamine hydrohalic acid salt is 2-chloroethylamine hydrochloride.

Further, the base is sodium hydroxide. The inventor finds that when sodium carbonate and potassium carbonate are used as alkali, the hydrohalic acid of 2-halogen ethylamine cannot be completely removed, and strong alkali is required to meet the requirement.

Further, the molar part of the base was 2.0.

Furthermore, the reaction is divided into two stages, the first stage (stage I) is firstly reacted for 12 to 24 hours at the temperature of between 10 and 30 ℃; the second stage (stage II) is carried out at 90-110 ℃ for 12-24 hours.

Desalting, dehydration under reduced pressure and vacuum drying in step (2) of the above reaction are conventional operations. Wherein the desalting can be one of dialysis, nanofiltration membrane desalting, filtration desalting after concentration and the like; or concentrating, adding solvent to precipitate salt, and removing organic solvent, wherein the organic solvent is at least one of methanol, ethanol and diethyl ether. One skilled in the art can readily select an appropriate desalting means for purifying the synthesized PEI as desired.

Compared with the prior art, the invention has the following positive effects:

1. the invention takes 2-bromoethylamine hydrobromide or 2-chloroethylamine hydrochloride as a raw material, sodium hydroxide or potassium hydroxide as alkali and water as a solvent, and adopts a one-pot method to directly synthesize the PEI polymer, thereby omitting the steps of separation, storage and the like of toxic monomer EI, and being a more environment-friendly and safer synthesis method.

2. The polyethyleneimine prepared by the invention has the advantages of cheap and easily-obtained raw materials, high yield, less pollution, simple operation and easy industrial popularization.

Drawings

FIG. 1 is a chart of an infrared absorption spectrum of polyethyleneimine prepared in example 2.

FIG. 2 is a NMR spectrum of polyethyleneimine prepared in example 2. Description of the symbols: p in the nmr carbon spectrum represents the carbon on the piperazine ring.

FIG. 3 is a NMR carbon spectrum of polyethyleneimine prepared in example 2.

FIG. 4 is a high resolution mass spectrum of polyethyleneimine prepared in example 2. Italics is the theoretical value.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be merely illustrative of the practice and effects of the present invention, and are not intended to limit the invention in any way.

Examples 1 to 28

The process parameters and conditions of this set of examples are as follows: 1 mole of 2-haloethylamine hydrohalic acid salt ("halo" is chloro, 115.99g; halo "is bromo, 204.89g; dissolved in water to a mass concentration of 33.3% (" halo "is chloro) or 45.4% (" halo "is bromo), 2 moles of sodium hydroxide are added and reacted at 25 ℃ for 24 hours (stage I); then reacting at 100 ℃ for 24 hours (stage II), evaporating the obtained mixture to dryness under reduced pressure to obtain a solvent, adding a mixed solvent of methanol and ether (the volume ratio is 2:1), separating out a salt, concentrating the organic phase under reduced pressure for 1h, and continuously drying in vacuum at 50 ℃ for 24h to obtain a transparent oily viscous substance. The above process conditions and parameters describe the process parameters for example 2 (PEI 2, when "halo" is chloro) and example 5 (PEI 5, when "halo" is bromo). When the "halogen" in the starting material is chlorine, other examples vary the parameters on the basis of example 2; other examples vary the parameters based on example 5 when the "halo" in the feed is bromine. Table 1 lists the values of the parameters changed, and the structural parameters of the resulting PEI, where "halogen" refers to the type of halogen in the starting material. It is to be noted that the numbers of the samples in Table 1 are the numbers of the examples, and that PEI 6 indicates the product obtained in example 6.

TABLE 1

The molecular weight of the obtained polymer is measured by a Ubbelohde viscosity method, the inner diameter of the Ubbelohde viscometer is 0.4-0.5mm, and the test 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 ℃. With different ratios of amino groups (primary, secondary, tertiary) (1 °:2 °:3 °) ¹³ C quantitative nuclear magnetic resonance. The piperazine content in Table 1 was also used ¹³ C quantitative nmr measurements were made as the percentage of C in piperazine to total polymer carbon.

FIG. 1 is an IR spectrum of PEI 2 obtained in example 2 showing a distinct N-H vibrational peak; N-CH is observed in nuclear magnetic hydrogen spectrum (figure 2) ₂ A proton peak of (a); 8C peaks were observed in the NMR spectrum (FIG. 3), which is the same as commercial PEI, and further has a peak (P) of piperazine ring. The mass spectrum of the product obtained (FIG. 4) shows that the molecular weight of the PEI obtained is an integer multiple of the molecular weight of the monomeric ethyleneimine (43.0422). The remaining samples showed similar spectra but with piperazine contentThe difference is that.

In examples 1 to 6 in Table 1, the concentrations of the raw materials were changed, the piperazine content in the product was increased as the mass concentration of the raw materials was increased, and the concentration of the raw materials was decreased in order to obtain a product having a high purity (low piperazine content), but the concentration was too low, the yield was low, and mass production was not facilitated, and the raw material mass concentration of 30 to 40% was an appropriate concentration.

The results of example 2 and examples 7 to 9 show that the reaction temperature in stage I is suitably low, the reaction temperature is high, and the amounts of by-products of piperazine and ethanolamine are large, although the temperature and time in stage I are changed under the same conditions. In the first stage, mainly ethylene imine and polyethyleneimine oligomer are generated, and the amount of byproducts is large, so that the molecular weight of the product is reduced, and the content of piperazine is increased. The reaction temperature in the first stage is 5-50 deg.c, preferably 10-30 deg.c, the reaction time is 0-24 hr, and the reaction time may be short. In example 9, stage I was not present (stage I reaction time was 0), the reaction mixture was heated directly to 100 ℃ and held for 24h, the molecular weight of the product obtained was very low, the viscosity average molecular weight was only 1000, and the piperazine content was as high as 10.7%.

Examples 10-17 the reaction parameters for stage II were fixed at 120 ℃ and 24h, with only the temperature (5-50 ℃) and time (0-24 h) of stage I being varied. From the results obtained, the temperature of stage II increased from 100 ℃ to 120 ℃ resulting in a slight increase in molecular weight, the parameters of stage I had a great influence on the molecular weight and purity of the product, and the low temperature of stage I was favorable for obtaining a product of high molecular weight and high purity. The products obtained without stage I (i.e. with a stage I reaction time of 0) both have a low molecular weight (PEI 13 and PEI 17) and a high piperazine content.

In example 2 and examples 18-22, other reaction parameters were varied and the table shows the optimum number of moles of base to be 2, which is advantageous for obtaining high molecular weight products. When NaOH is added at 2.2 and 2.5 moles, the molecular weight of the resulting product is significantly reduced, since excess base will cause hydrolysis of 2-haloethylamine to ethanolamine; in stage II, ethanolamine initiates ring-opening polymerization of ethylene imine to obtain the product. If too much ethanolamine is produced as a by-product, the molecular weight of the resulting PEI may be reduced. When NaOH is insufficient, such as the mole number is reduced to 1.9, part of chloroethylamine can not be converted into an ethylene imine monomer, and the reaction is not facilitated; of course, also in this case PEI products (PEI 18, table 1) were obtained, which products also had a relatively high piperazine ring content (PEI (6.2%). The amount of base used cannot be too low, and below 1.8 moles, the molecular weight of the product decreases to several hundred and the product contains a large amount of C-Cl end groups.

Examples 23-28 were conducted by varying the reaction time and temperature of stage II, and it was found from the results that the relationship between the piperazine content of the product and the reaction parameters of stage II was not very large, since the piperazine ring was mainly derived from the piperazine by-product formed in stage I; the resulting extended reaction time may increase the molecular weight of the final product. The low reaction temperature in stage II is not favorable for obtaining high molecular weight products (such as PEI 28).

Generally speaking, the production of PEI by using halogen ethylamine as a raw material can be completed by a one-pot method, and the reaction is preferably divided into two stages, wherein the stage I is at 10-30 ℃ for 12-24 hours, and the stage II is at 90-110 ℃ for 12-24 hours. Stage I, generating an ethylene imine monomer, a PEI oligomer and a small amount of piperazine and ethanolamine by-products; and in the stage II, PEI oligomer, piperazine and ethanolamine are mainly generated to initiate EI ring-opening polymerization, and the polymer is obtained.

It is noted that the corresponding PEI can also be synthesized using lithium hydroxide or potassium hydroxide as the base.

Claims

1. A method for preparing polyethyleneimine is characterized in that the method comprises the following process steps and conditions:

(1) Dissolving 1 mol part of 2-halogen ethylamine hydrohalic acid salt in water to ensure that the mass concentration of the 2-halogen ethylamine hydrohalic acid salt is 10-50%, adding 1.8-2.3 mol parts of alkali, and reacting for 12-24 hours at the temperature of 5-30 ℃; then reacting for 12-48 hours at 50-120 ℃; the halogen in the 2-halogen ethylamine hydrohalic acid salt is at least one of chlorine and bromine, and the alkali is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide;

(2) And (3) desalting the mixture obtained in the step (1), dehydrating under reduced pressure, and drying in vacuum to obtain a transparent viscous liquid product.

2. The method for preparing polyethyleneimine according to claim 1, wherein the mass concentration of the 2-haloethylamine hydrohalide salt is 30% to 40%.

3. A process for preparing polyethyleneimine according to claim 1, wherein the molar fraction of the base is 2.0.

4. The method of preparing polyethyleneimine according to claim 1, wherein the reaction conditions are such that the reaction is performed at 10 to 30 ℃ for 12 to 24 hours, and then at 90 to 110 ℃ for 12 to 24 hours.