CN117181022A

CN117181022A - Polyether sulfone ultrafiltration membrane and preparation method and application thereof

Info

Publication number: CN117181022A
Application number: CN202311355840.5A
Authority: CN
Inventors: 朱瑶瑶; 熊桑琪; 钟琳; 孙璞; 公兵
Original assignee: Suzhou Xinrui Medical Technology Co ltd
Current assignee: Suzhou Xinrui Medical Technology Co ltd
Priority date: 2023-10-19
Filing date: 2023-10-19
Publication date: 2023-12-08

Abstract

The invention discloses a polyether sulfone ultrafiltration membrane and a preparation method and application thereof, wherein the preparation method comprises the following steps: weighing polyethersulfone resin, organic solvent, hydrophilic substance additive and pore-forming agent according to a certain proportion, heating to 50-80 ℃ and stirring and dissolving the raw materials under nitrogen atmosphere to obtain casting solution, and standing the casting solution to remove bubbles, wherein the hydrophilic substance additive is nano particles and trimesic acid; and then scraping the obtained casting film liquid on a glass substrate, standing for phase separation, immersing in a coagulating bath, and preparing the polyethersulfone ultrafiltration film by adopting a phase inversion method. The polyethersulfone ultrafiltration membrane prepared by the invention has excellent interception performance on low molecular weight substances, high water flux and outstanding stability, solves the requirements of the fields of biological pharmacy, food industry and the like on high performance, skin thickness and interception of the low molecular weight ultrafiltration membrane, and has great application prospects in the aspects of medicine concentration and purification, water purification, protein separation and the like.

Description

Polyether sulfone ultrafiltration membrane and preparation method and application thereof

Technical Field

The invention belongs to the technical field of membrane separation, and particularly relates to a polyether sulfone ultrafiltration membrane capable of intercepting low molecular weight substances, and a preparation method and application thereof.

Background

The membrane separation technology is to separate, purify and enrich the solute and the solvent in the mixture under the pushing of external energy and chemical potential difference. Compared with other traditional separation methods, the membrane separation has the characteristics of simple process, better economy, no phase change and the like. The membrane separation technology mainly comprises four types of Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and Reverse Osmosis (RO), wherein the ultrafiltration membrane separation technology is widely used in industries such as water treatment, bio-pharmaceuticals, food processing, drinking water preparation and the like due to the characteristics of low operating pressure, large water yield and the like, and has the main functions of separating, concentrating and purifying substances.

Ultrafiltration membranes are classified according to molecular weight cut-off, and can be classified into ultrafiltration membranes of small molecular weight cut-off (MWVO <5000 g/mol) and large pore size ultrafiltration membranes (MWCO >1000000 g/mol). At present, commercial polymer ultrafiltration membranes studied at home and abroad are of a large variety, but most ultrafiltration membrane trapped substances mainly concentrate on the molecular weight of tens of thousands to hundreds of thousands, and few ultrafiltration membranes for trapping small molecular weight substances are studied. The materials of the ultrafiltration membrane with low molecular weight cut-off in the market at present mainly comprise: polyether sulfone (PES), polysulfone (PSF), cellulose Acetate (CA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and other polymer materials.

At present, most ultrafiltration membranes are mainly prepared by non-solvent induced phase separation, and on the basis of polysulfone ultrafiltration base membranes in China patent CN109126489B, the polysulfone membranes have different interception effects on polyethylene glycol (PEG) by adjusting the concentration treatment of a polyvinyl alcohol (PVA) aqueous solution, and the interception rate of PEG (1000-6000) is 40% -60%. Chinese patent CN101484234B is advantageous for hydrophilic polymerization of polysulfone bath, and has an open-cell separation layer in the inner cavity, an adjacent support layer with asymmetric spongy pore structure but without fingerholes, and a certain retention property for substances of 2-20 ten thousand daltons. Also, the mode of adjusting the pore structure of the membrane, such as the mode of adjusting the hydrophilicity of the membrane, such as the mode of adjusting the pore structure of the membrane, such as the mode of adjusting the pore. The technology only solves the problems of stability of an ultrafiltration membrane or separation of separation substances with selectivity or characteristics, but has the disadvantage of retaining small molecular substances, flux and the like.

With the continuous improvement of requirements of biopharmaceuticals, food industry and environmental protection, the demands on low-molecular-weight ultrafiltration membranes in the market are increased, the requirements are also continuously improved, and the defects of thick skin, low water flux, easy pollution and the like are that the common diseases of the commercial low-molecular-weight ultrafiltration membranes are studied at present, so that the demands of part of market industry are not met. Therefore, it is urgent to develop an ultrafiltration membrane having a low molecular weight cut-off and excellent stability.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a polyether sulfone ultrafiltration membrane, a preparation method and application thereof, wherein the polyether sulfone ultrafiltration membrane has excellent interception performance on low molecular weight substances, high water flux and outstanding stability, solves the requirements of the fields of biopharmaceuticals, food industry and the like on the ultrafiltration membrane with high performance, skin thickness and interception of the low molecular weight substances, and has a wide application prospect in the aspects of drug concentration and purification, water purification, protein separation and the like.

The technical scheme of the invention is as follows:

the invention relates to a preparation method of a polyethersulfone ultrafiltration membrane, which comprises the following steps:

(1) Weighing polyethersulfone resin, organic solvent, hydrophilic substance additive and pore-forming agent according to a certain proportion, heating to 50-80 ℃ and stirring and dissolving the raw materials in nitrogen atmosphere to obtain casting solution, and standing the casting solution to remove bubbles; the hydrophilic substance additive is nano particles and trimesic acid;

(2) Scraping the casting film liquid obtained in the step (1) on a glass substrate, standing and phase-separating for 0-10s, then immersing in a coagulating bath, and preparing the polyethersulfone ultrafiltration film by adopting a phase inversion method.

Preferably, the polyether sulfone resin comprises, by mass, 10-16 parts of polyether sulfone resin, 77-85 parts of organic solvent, 0-5 parts of hydrophilic substance additive and 0-2 parts of pore-forming agent, wherein the hydrophilic substance additive and the pore-forming agent do not comprise 0.

Preferably, the polyether sulfone resin comprises 15 parts by mass of polyether sulfone resin, 80 parts by mass of organic solvent, 4 parts by mass of hydrophilic substance additive and 1 part by mass of pore-forming agent.

Preferably, the molecular weight of the polyethersulfone resin is 53000-82000g/mol, more preferably 58000g/mol, and the molecular weight of the polyethersulfone resin is moderate, so that the film formation and the film pore structure adjustment are facilitated;

the organic solvent is one or more of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), N-Dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO) and butyl lactate;

the nano particles are nano titanium oxide and/or nano silicon oxide, the nano particles provide roughness, trimesic acid plays a role of hydrophilia and pore-forming, the hydrophilicity of the nano particles is not high when the nano particles are singly used, and the hydrophilia performance is greatly improved after the nano particles are used with the assistance of trimesic acid;

the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, lithium chloride and sodium chloride, the molecular weight of polyvinylpyrrolidone (PVP) is 5000-58000g/mol, and the molecular weight of polyethylene glycol (PEG) is 400-2000g/mol.

Preferably, in the step (1), stirring and dissolving are carried out for 6-10 hours.

Preferably, in the step (2), the phase separation is carried out by standing for 0-10s, the standing environment temperature is 20-35 ℃, and the relative humidity is 30-70%.

Preferably, in the step (2), the coagulating bath is a mixed solution of pure water and methanol, the volume ratio of the pure water to the methanol is 9:1, the temperature of the coagulating bath is 20-40 ℃, and the immersing time in the coagulating bath is 10-30min. Because of the addition of alcohols, the exchange speed of the solvent in the casting solution is regulated and controlled, and the thermodynamic stability in the film forming process is changed. It is generally believed that alcohols contained in the coagulation bath tend to reduce thermodynamic stability, and that the phase separation speed of the casting solution after immersion in the coagulation bath changes, so that a porous structure of the film is obtained. The structural influence of the alcohol content on the membrane can change the porosity and the pore diameter of the membrane cortex, and the uniform influence on the membrane water flux and the retention rate is realized.

The invention adopts pure water/alcohol as the coagulating bath, the volume ratio is preferably 9/1, the proportion is moderate and less than 9/1, the effect is not ideal, the thermodynamic influence of the existence of the alcohol in the film forming process is small, and a compact skin layer is easy to form, which is unfavorable for the change of the performance. If the ratio is higher than 9/1, the uncontrollable change of the thermodynamic stability during the film formation will be increased. The exchange speed is increased and then slowly reduced, the formed membrane pore structure is gradually biased to large finger-shaped pores, the membrane cortex pore structure is much larger, and the performance influence is greatly changed.

In the formula system, the existence of alcohols increases the diffusion exchange speed, combines the trimesic acid crosslinking characteristic, has controllable exchange speed under the alcohol system condition, is beneficial to the diffusion and dispersion of nano particles, and reduces the particle agglomeration risk. The principle is similar compatibility, and the hydrogen bond acting force increases the controllability of the particle and the exchange speed.

Preferably, in the step (2), the casting solution is scraped onto the glass substrate, and the thickness of the scraper is 150 μm to 300 μm. The thickness of the film is too low, the thickness of the skin layer is thinner, and the interception performance is not high; too high a thickness can result in too thick a skin structure, slightly higher retention but poorer flux performance.

Preferably, the polyethersulfone ultrafiltration membrane taken out of the coagulating bath is also required to be cleaned and dried in vacuum to obtain a dry film, wherein the vacuum drying temperature is 20-35 ℃ and the vacuum drying time is 4-6 hours; the cleaning process is to clean the ultrafiltration membrane for a plurality of times by using pure water to remove residual solvents, pore-forming agents and other substances.

The invention also relates to a polyethersulfone ultrafiltration membrane which is characterized by being prepared by adopting the preparation method. Wet film: the ultrafiltration membrane washed by pure water for many times is stored in a mixed solution of pure water and glycerol (volume ratio is 4:1), and the ultrafiltration membrane is required to be washed by pure water and then tested during testing.

The invention also relates to the use of polyethersulfone ultrafiltration membranes for the entrapment of low molecular weight substances having a molecular weight of 800-4000g/mol, more preferably 800-2000g/mol.

The beneficial effects of the invention are as follows:

(1) The invention prepares the casting film liquid by dissolving polyether sulfone resin with relatively low molecular weight in an organic reagent, adding hydrophilic substances (mixture of nano silicon oxide and trimesic acid) and pore-forming agent and stirring. Wherein the low molecular weight polyethersulfone resin is favorable for film formation and a film with a relatively thin thickness is easily obtained; the use of the nano particles can increase the roughness of the surface and pore channels of the membrane, and the hydrophilic substance is combined to improve the hydrophilicity of the membrane; the pore-forming agent is added to adjust the size of the membrane pores, so that a small pore membrane structure can be conveniently obtained; under the synergistic effect of several substances, the phase separation speed of the film, the surface structure of the film and the hydrophilic performance can be regulated.

(2) The invention not only realizes the interception of low-component substances, but also has higher water flux and better stability. The interception performance is that substances with large molecular weight are difficult to pass through due to a compact cortex and a small-aperture structure on the surface of the membrane material; stability and water flux are achieved by adjusting the molecular weight and content of hydrophilic materials and polyethersulfone resin to optimize membrane structure and hydrophilicity. According to the invention, the polyether sulfone ultrafiltration membrane with small molecular weight substances interception and excellent stability is obtained by optimizing the formula.

Drawings

The invention is further described below with reference to the accompanying drawings and examples:

FIG. 1 an enlarged view of a scanning electron microscope of a polyethersulfone ultrafiltration membrane prepared in example 1;

FIG. 2 example 1 low molecular weight cut-off performance graph for polyethersulfone membranes;

FIG. 3 is a graph of water flux performance versus membrane preparation for various examples;

FIG. 4 example 1 preparation of a polyethersulfone membrane cycle stability test chart;

FIG. 5 SEM sectional structure of the polyether sulfone membrane prepared in example 5;

FIG. 6 is a graph of flux comparison of example 1 with each of the comparative examples;

FIG. 7 example 1 water contact angle plot;

fig. 8 is a graph of the water contact angle of comparative example 3.

Detailed Description

The objects, technical solutions and advantages of the present invention will become more apparent by the following detailed description of the present invention with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention.

Example 1

Preparing casting solution: 15g of polyethersulfone (58000 g/mol), 79.5g of N, N-dimethylacetamide, 1.33g of nano silicon oxide (50-100 nm), 2.67g of trimesic acid (TMA) and 1.5g of polyethylene glycol (400 g/mol) are weighed, heated in an oil bath at 80 ℃ and stirred and dissolved for 8 hours under nitrogen atmosphere. And after stirring, standing the casting solution to remove bubbles, and removing redundant bubbles in the casting solution.

Coagulation bath: the composition is composed of pure water and methanol, and the volume ratio is 9:1. The methanol has the functions of regulating the solvent diffusion speed in the phase inversion process and improving the surface compactness of the membrane; the more the solvent content in the coagulating bath, the more the system is thermodynamically unstable, the pore diameter is increased, and the experiment shows that 10% of methanol is beneficial to forming a small pore structure under the system. The water temperature of the coagulating bath is 25 ℃, and when the water temperature is too high, the solvent diffusion is accelerated, and the macroporous surface is easy to form.

Film scraping process: the casting solution was scraped onto the glass plate substrate, and the thickness of the doctor blade was controlled to 250. Mu.m. The ambient temperature is 28 ℃, the relative humidity is 55%, and the exposure time of the liquid film in the air is controlled to be 4s, so that the liquid film is initially phase-formed. The phase inversion film is controlled in the coagulating bath for 15min, and is soaked and washed by pure water for multiple times after being taken out, and residual solvents, hydrophilic substances and the like are removed.

And (3) testing and verifying: and taking the cleaned polyethersulfone ultrafiltration membrane, and performing performance test verification.

Prepressing the wet polyether sulfone ultrafiltration membrane for 20min and testing the pressure to be 0.2MPa; the dry polyethersulfone membrane is wetted with the test solution and then tested. The result shows that the polyethersulfone ultrafiltration membrane has better retention performance on small molecular substances, wherein the retention rate of PEG800 molecular weight is about 77%, the retention rate of PEG4000 is more than 90%, and the retention rates of different molecular weights are shown in figure 2. The polyethersulfone ultrafiltration membrane has a relatively small surface pore size, about 10-30nm (as shown in FIG. 1), and a water contact angle of about 30 ° (FIG. 7). The polyethersulfone ultrafiltration membrane has excellent stability through polyethylene glycol (1000 g/mol) test, and the water flux performance of the membrane is basically stable after repeated cycle test (the test result is shown in figure 4).

Example 2

The preparation conditions and the test method were the same as in example 1 except for the raw material ratio of the casting solution based on example 1.

Proportioning: 15g of polyethersulfone (58000 g/mol), 78g of N, N-dimethylacetamide, 1.67g of nano silicon oxide (50-100 nm), 3.33g of trimesic acid (TMA) and 2.0g of polyethylene glycol (400 g/mol).

Test conditions: the membranes prepared in this example had 46% retention of PEG800 and 75% retention of PEG 4000. The main factors are that the content of the pore-forming agent is more, the speed is slightly high in the phase inversion process, so that the pore diameter of the surface of the membrane is slightly increased, the interception performance is reduced, and the water flux is improved (as shown in figure 3).

Example 3

The preparation conditions and the test method were the same as in example 1 except for the raw material ratio of the casting solution and the following conditions in the phase inversion process, based on example 1.

Proportioning: 16g of polyethersulfone (58000 g/mol), 78g of N, N-dimethylacetamide, 1.33g of nano silicon oxide (50-100 nm), 2.67g of trimesic acid (TMA) and 2.0g of polyethylene glycol (400 g/mol).

Phase inversion process: the thickness of the scraping film is 350 mu m, the ambient temperature is 25 ℃, the relative humidity is 70 percent, and the scraping film is kept stand in the air for 8s. After phase inversion to form a film, the thickness of a dense cortex on the surface of the film is increased by SEM, and the flux of the film is reduced by 540LMH (L.times.m) ² * h) Range. The retention rate of the PEG800 for the small molecular substance is 52 percent, and the retention rate of the PEG1000 is about 60 percent.

Example 4

Proportioning: 15g of polyethersulfone (58000 g/mol), 80g of N, N-dimethylacetamide, 1.33g of nano silicon oxide (50-100 nm), 2.67g of trimesic acid (TMA) and 1.0g of polyvinylpyrrolidone (10000 g/mol).

Test conditions: the water flux of the prepared polyethersulfone membrane was tested at about 648LMH. Probably because the high molecular weight polyvinylpyrrolidone has better pore-forming effect, the membrane pore structure is slightly increased; meanwhile, the retention rate of the PEG800 of the low molecular weight substance is 53 percent, and the retention rate of the PEG4000 is 66 percent.

Example 5

Proportioning: 15g of polyethersulfone (82000 g/mol), 80g of N, N-dimethylacetamide, 1.33g of nano silicon oxide (50-100 nm), 2.67g of trimesic acid (TMA) and 1.0g of polyvinylpyrrolidone (10000 g/mol).

Test conditions: the water flux of the prepared polyethersulfone membrane is about 480LMH, the retention rate of PEG800 is 43% and the retention rate of PEG4000 is 74% for low molecular weight substances. The performance was significantly improved over the water flux performance of comparative example 2, mainly due to the addition of hydrophilic agents and porogens, but the membrane surface still formed a relatively dense skin, support layer structure (shown in fig. 5).

Comparative example 1

Proportioning: 15g of polyethersulfone (58000 g/mol), 80g of N-methylpyrrolidone, 3g of trimesic acid (TMA) and 1.0g of polyethylene glycol (400 g/mol).

Test conditions: the water flux of the prepared polyethersulfone membrane reaches 667LMH, and the hydrophilic monomer trimesic acid is high in amount, so that the inter-diffusion rate between a solvent and a non-solvent is influenced, and the structure and the performance of the membrane are further influenced. The retention rate of the polyethersulfone ultrafiltration membrane on the low molecular weight substance PEG800 is 43 percent, and the retention rate of PEG4000 is 70 percent.

The hydrophilic coupling crosslinking property of trimesic acid can easily lead the casting film to be uniformly in the coagulating bath, and the exchange rate is accelerated in the film forming process, so that the surface density of the film is relatively low (the water contact angle is about 37 degrees), and the performance of the film is low.

Comparative example 2

Based on the embodiment 1, the proportion of the casting solution is as follows: polyether sulfone (82000 g/mol) was weighed as 16g, N-dimethylacetamide was taken as 84g, and no pore-forming agent and hydrophilic substance was used, pure polysulfone type casting solution. Other conditions were the same as in example 1.

Test conditions: the prepared pure polyethersulfone membrane has low water flux, about 320LMH, 71% retention rate of PEG800 and 92.5% retention rate of PEG4000 for low molecular weight substances. The polyether sulfone has the advantages that the molecular weight is large, the viscosity is slightly high, the porosity of a supporting layer formed during film forming phase inversion is reduced, the density of a film surface cortex is increased, the pore diameter in an SEM image of the film surface is about 15nm-20nm, and therefore the water flux of the film is low and the rejection rate is increased.

Comparative example 3

On the basis of example 1, the proportion of the casting solution to the coagulation bath was adjusted, and other experimental conditions were unchanged.

Pure water is used as a coagulating bath of the casting film liquid in the experiment, the surface structure of the prepared film is extremely compact, the pore diameter of the film surface is about 20nm, and the water contacts with water at about 80 degrees (figure 8), and the main factor is that the pure water influences the exchange speed between an organic solution in the casting film liquid and the coagulating bath, so that the film surface is extremely easy to form a compact skin structure. The water flux of the comparative membrane was low, about 300LMH, the retention rate for PEG 2000 was 94% and the retention rate for PEG800 was 80%.

Comparative example 4

On the basis of example 1, experiments were carried out by adjusting the ratio of methanol to water in the coagulation bath, and other experimental conditions were unchanged.

In the experiment, the ratio of the coagulating bath water to the methanol is 8:2, the surface cortex of the prepared membrane is loose, the membrane pore structure is larger, the proportion of the methanol is mainly increased, the earlier exchange speed of the organic solvent in the casting solution is accelerated, and a macroporous structure is easily formed at a higher exchange speed. The membrane performance, water flux about 800LMH, retention of PEG 2000 about 40%, retention of PEG 10000 about 65%.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explanation of the principles of the present invention and are in no way limiting of the invention. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the scope and boundary of the appended claims, or equivalents of such scope and boundary.

Claims

1. The preparation method of the polyethersulfone ultrafiltration membrane is characterized by comprising the following steps of:

(2) Scraping the casting film liquid obtained in the step (1) on a glass substrate, standing for phase separation, immersing in a coagulating bath, and preparing the polyethersulfone ultrafiltration film by adopting a phase inversion method.

2. The production method according to claim 1, wherein the mass parts of the hydrophilic substance additive and the porogen do not include 0, and the mass parts of the polyether sulfone resin are 10 to 16, the organic solvent is 77 to 85, the hydrophilic substance additive is 0 to 5, and the porogen is 0 to 2.

3. The production method according to claim 1, wherein the molecular weight of the polyethersulfone resin is 53000-82000g/mol;

the organic solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and butyl lactate;

the nano particles are nano titanium oxide and/or nano silicon oxide;

the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol and lithium chloride, wherein the molecular weight of polyvinylpyrrolidone is 5000-58000g/mol, and the molecular weight of polyethylene glycol is 400-2000g/mol.

4. The process according to claim 1, wherein in step (1), the stirring and dissolving are carried out for a period of 6 to 10 hours.

5. The method according to claim 1, wherein in the step (2), the phase separation is performed for 0 to 10 seconds at a standing temperature of 20 to 35 ℃ and a relative humidity of 30 to 70%.

6. The method according to claim 1, wherein in the step (2), the coagulation bath is a mixed solution of pure water and methanol, and the volume ratio of the pure water to the methanol is 9:1; the temperature of the coagulating bath is 20-40deg.C, and the soaking time in the coagulating bath is 10-30min.

7. The method according to claim 1, wherein in the step (2), the casting solution is scraped onto the glass substrate, and the thickness of the scraper is 150 μm to 300. Mu.m.

8. The preparation method according to claim 1, wherein the polyethersulfone ultrafiltration membrane taken out of the coagulation bath is further subjected to washing and vacuum drying to obtain a dry film, wherein the vacuum drying temperature is 20-35 ℃ and the vacuum drying time is 4-6h.

9. A polyethersulfone ultrafiltration membrane prepared by the method of any one of claims 1-8.

10. Use of the polyethersulfone ultrafiltration membrane of claim 9 for the rejection of low molecular weight materials having a molecular weight of 800-4000g/mol.