Preparation method of hydrophobic modified polyethersulfone porous membrane

Abstract

The invention provides a preparation method of a hydrophobic modified polyethersulfone porous membrane, which comprises the following steps: firstly, preparing a hydrophobic modified solution, then carrying out crosslinking pretreatment to form a hydrophobic crosslinking coating on a polyethersulfone base membrane, then carrying out crosslinking under ultraviolet irradiation, and finally preparing the hydrophobic polyethersulfone porous membrane. The pre-crosslinked membrane formed by crosslinking pretreatment is formed by forming a hydrophobic crosslinked coating on a polyethersulfone base membrane, and a hydrophobic monomer is grafted on the hydrophobic crosslinked coating under the irradiation of ultraviolet light; the hydrophobic cross-linked coating not only coats the outer surface of the polyethersulfone base membrane, but also can be impregnated on a porous structure in the polyethersulfone membrane, and finally the hydrophobic modified polyethersulfone porous membrane is prepared. Wherein the cross-linking agent is a monomer containing a plurality of unsaturated bonds, an addition polymerization reaction can occur among the unsaturated bonds to form a spatial net-shaped structure, the hydrophobic cross-linking coating can be firmly covered on the porous structure of the polyether sulfone and cannot fall off, and the hydrophobic monomer is also provided with unsaturated bonds, so that the addition polymerization reaction occurs between the hydrophobic monomer and the cross-linking agent, and a certain number of hydrophobic groups are grafted.

Description

Technical Field

[0001] The present invention relates to the technical field of separation membranes, and in particular to a method for preparing a hydrophobically modified polyethersulfone porous membrane. Background Art

[0002] Polyethersulfone (PES) is a high-performance separation membrane material with excellent chemical stability and mechanical strength. Porous membranes are often prepared using the solute phase transition method. However, the preparation of polyethersulfone membranes typically requires the addition of hydrophilic porogens such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG). This results in weak hydrophobicity and makes it unsuitable for applications requiring high hydrophobicity, such as sterilization and ventilation of fermentation tanks. Membrane separation processes requiring high hydrophobicity typically utilize materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), and polyethylene (PE). However, PTFE membranes are not resistant to radiation, while PP and PE membranes exhibit poor oxidation resistance and anti-fouling properties. PVDF membranes exhibit lower air permeability than PES membranes. Currently, there is a significant demand for hydrophobic membranes in the market for air or gas filtration. PES membranes offer excellent chemical stability, high mechanical strength, and the ability to withstand gamma irradiation. They can be hydrophobically modified for use in gas filtration applications such as biochemistry, testing, pharmaceuticals, and sterilization, particularly those requiring irradiation.

[0003] Based on this, existing technologies, such as Chinese patent publication number CN118846850A, disclose a method for obtaining a hydrophobic polyethersulfone microporous membrane by immersing a micron-sized polyethersulfone filter base membrane in a modifying solution such as C6 or C8 and then drying it. Although this method offers a simple modification process, easy operation, and the absence of additional equipment, enabling continuous production, it suffers from uneven modification and prone to pore clogging, resulting in differences in hydrophobicity at different locations on the membrane and decreased flux. Most importantly, this type of hydrophobically modified membrane irreversibly reverts to a hydrophilic state upon contact with organic solvents such as ethanol and isopropanol.

[0004] Another example is a Chinese patent application with publication number CN106268355A, which discloses an asymmetric superphilic / hydrophobic bisexual polymer membrane and a preparation method. The membrane is prepared by introducing a hydrophobic substance with extremely low surface energy onto the surface. However, the introduction of superhydrophilic groups or substances onto the superhydrophilic side of the polymer membrane significantly increases the water permeability of the polymer membrane. This means that once the critical breakthrough pressure of water is exceeded, water droplets penetrate into the pores of the bulk membrane from the superhydrophobic side of the asymmetric superphilic / hydrophobic bisexual polymer membrane. This hinders its application in high-pressure environments, and its production process is relatively complex, making it difficult to scale up.

[0005] Another example is Chinese patent publication CN105251370A, which discloses a superhydrophobic air filtration membrane, its preparation method, and its use. The membrane is formed by adding a low-surface tension additive to the casting solution. While seemingly simple, this method requires consideration of the compatibility of the low-surface tension additive with the polymer and casting solution, as well as the potential for loss of the low-surface tension additive and its significant impact on the membrane's structure and mechanical strength.

[0006] In view of this, it is necessary to improve the hydrophobic modification method of polyethersulfone membrane in the prior art to solve the above problems. Summary of the Invention

[0007] The inventive concept of the present invention is: using a polyethersulfone hydrophilic membrane as a base membrane, coating, impregnating and forming a hydrophobic cross-linked layer on the outer surface and internal porous structure of the polyethersulfone, and then completing cross-linking through ultraviolet light and a cross-linking agent, that is, grafting hydrophobic monomers onto the hydrophobic cross-linked coating to complete the hydrophobic modification of the polyethersulfone porous membrane.

[0008] The purpose of the present invention is to disclose a method for hydrophobic modification of polyethersulfone membranes, which can not only coat the outer surface of the polyethersulfone membrane but also impregnate the inner porous structure of the polyethersulfone membrane to ensure hydrophobicity and tolerance.

[0009] To achieve the above object, the present invention provides a method for preparing a hydrophobically modified polyethersulfone porous membrane, comprising the following steps:

[0010] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.05-0.8 parts of an initiator, 4-15 parts of a hydrophobic monomer, 4-15 parts of a cross-linking agent, and 70-92 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0011] S2 cross-linking pretreatment: dip-coating, spraying or spin-coating the hydrophobic modification solution in S1 on the polyethersulfone base membrane for a certain period of time, and then removing excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0012] S3 cross-linking: The pre-cross-linked membrane is cross-linked under ultraviolet irradiation at a temperature of 20-60°C for 10-30 minutes. After the cross-linking is completed, the membrane is dried to obtain a hydrophobic polyethersulfone porous membrane.

[0013] The pre-crosslinked membrane formed by the crosslinking pretreatment is a hydrophobic crosslinked coating formed on the polyethersulfone base membrane, and the hydrophobic monomer is grafted onto the hydrophobic crosslinked coating under ultraviolet light irradiation;

[0014] The hydrophobic cross-linked coating not only coats the outer surface of the polyethersulfone base membrane, but can also be impregnated into the internal porous structure of the polyethersulfone membrane, thereby finally preparing a hydrophobically modified polyethersulfone porous membrane.

[0015] In some embodiments, the initiator in S1 is a free radical photoinitiator.

[0016] In some embodiments, the initiator is one or more of benzoin and its derivatives, benzophenones, α-hydroxyketones, acylphosphine oxides, and thioxanthones.

[0017] In some embodiments, the initiator is 1-hydroxycyclohexylphenyl ketone or 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0018] In some embodiments, the hydrophobic monomer in S1 is an unsaturated monomer containing a hydrophobic group.

[0019] In some embodiments, the hydrophobic monomer in S1 is a perfluoroalkyl acrylate monomer or a fluorine-free acrylate monomer.

[0020] In some embodiments, the perfluoroalkyl acrylate monomer is one or more of perfluoroalkyl ethyl acrylate, perfluorodecyl ethyl acrylate, 2-perfluorododecylethyl methacrylate, and perfluorohexylethyl chloroacrylate.

[0021] In some embodiments, the cross-linking agent in S1 is a monomer containing multiple unsaturated bonds, and the unsaturated bonds are carbon-carbon double bonds and / or carbon-carbon triple bonds.

[0022] In some embodiments, the cross-linking agent in S1 is an acrylate cross-linking agent.

[0023] In some embodiments, the solvent in S1 is one or more of methanol, ethanol, isopropanol, propanol, butanol and trifluorotoluene.

[0024] In some embodiments, the pore size of the polyethersulfone-based membrane in S2 is 0.02 μm to 10 μm.

[0025] In some embodiments, the time of dip coating, spray coating or spin coating in S2 is 20-120 seconds, and then the film is placed at a temperature of 30-70° C. for 5-15 minutes to remove excess hydrophobic modification solution on the polyethersulfone-based membrane.

[0026] In some embodiments, the wavelength of the ultraviolet light in S3 is 200-300 nm.

[0027] In some embodiments, the water contact angle of the hydrophobically modified polyethersulfone porous membrane is greater than 90°.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) the cross-linking agent is a monomer containing multiple (at least 2) unsaturated bonds, the unsaturated bonds are mainly carbon-carbon double bonds and carbon-carbon triple bonds, and polyaddition reaction occurs between the unsaturated bonds to form a spatial network structure, i.e., a hydrophobic cross-linked coating, which ensures that the hydrophobic cross-linked coating is firmly covered on the polyethersulfone porous structure and will not fall off, and the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the unsaturated monomer indicates that the hydrophobic monomer also has an unsaturated bond (carbon-carbon double bond and carbon-carbon triple bond), which can undergo polyaddition reaction with the cross-linking agent, thereby connecting a certain number of hydrophobic groups; (2) the present invention is based on the existing polyethersulfone. The ethersulfone hydrophilic membrane is the base membrane, and a hydrophobic cross-linked layer is covered on the outer surface and the internal porous structure of the polyethersulfone. The cross-linking is formed by a cross-linking agent, and the hydrophobic monomer is grafted onto the hydrophobic cross-linked coating, that is, the polyethersulfone porous membrane is cross-linked and hydrophobically modified. The membrane pores are not easily blocked, and the porosity of the porous membrane is not affected, so that the polyethersulfone porous membrane still has a large air flux; (3) in a high-pressure or high-humidity environment, the hydrophobic modified membrane will not have the phenomenon of retained water droplets blocking the membrane ventilation volume, and can maintain a high flux state; in addition, the hydrophobic performance of the modified membrane is uniform, stable and long-lasting, and the hydrophobic modified membrane will not become a hydrophilic membrane again after contacting an alcohol organic solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The scanning electron micrographs of the polyethersulfone porous membrane before and after modification shown in Example 2 are shown;

[0030] Figure 2 The scanning electron micrographs of the polyethersulfone porous membrane before and after modification shown in Comparative Example 1 are shown;

[0031] Figure 3 The figure is a flow chart of the continuous production process of hydrophobic modification shown in the present invention. DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention.

[0033] Example 1

[0034] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0035] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.05 parts of an initiator, 4 parts of a hydrophobic monomer, 4 parts of a cross-linking agent, and 70 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0036] The initiator is benzophenone, the hydrophobic monomer is perfluoroalkylethyl acrylate, the crosslinking agent is ethylene glycol dimethacrylate, and the solvent is trifluorotoluene.

[0037] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 120 seconds, and then place it at 70°C for 15 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0038] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, and preferably 0.02 μm in this embodiment.

[0039] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 200 nm, the cross-linking temperature was 20°C, the cross-linking time was 30 min, and after the cross-linking was completed, it was dried to obtain a hydrophobic polyethersulfone porous membrane.

[0040] Example 2

[0041] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0042] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.3 parts of an initiator, 10 parts of a hydrophobic monomer, 10 parts of a cross-linking agent, and 85.7 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0043] The initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, the hydrophobic monomer is 2-perfluorododecylethyl methacrylate, the crosslinking agent is ethylene glycol dimethacrylate, and the solvent is a mixture of trifluorotoluene and isopropyl alcohol, with a mass ratio of 1:1.

[0044] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 50 seconds, and then place it at 55°C for 10 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0045] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, and preferably 0.22 μm in this embodiment.

[0046] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 250 nm, the cross-linking temperature was 40°C, the cross-linking time was 15 min, and the cross-linking was completed and then dried to obtain a hydrophobic polyethersulfone porous membrane.

[0047] Example 3

[0048] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0049] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.8 parts of an initiator, 15 parts of a hydrophobic monomer, 15 parts of a cross-linking agent, and 92 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0050] The initiator is 1-hydroxycyclohexyl phenyl ketone, the hydrophobic monomer is perfluorodecyl ethyl acrylate, the crosslinking agent is ethylene glycol diacrylate, and the solvent is a mixture of trifluorotoluene and ethanol, with a mass ratio of 1:1.

[0051] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 20 seconds, and then place it at 30°C for 5 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0052] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, preferably 5 μm in this embodiment.

[0053] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 300 nm, the cross-linking temperature was 20°C, the cross-linking time was 10 min, and after the cross-linking was completed, it was dried to obtain a hydrophobic polyethersulfone porous membrane.

[0054] Comparative Example 1

[0055] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0056] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.3 parts of an initiator, 10 parts of a hydrophobic monomer, 10 parts of a cross-linking agent, and 85.7 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0057] The initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, the hydrophobic monomer is 2-perfluorododecylethyl methacrylate, the crosslinking agent is ethylene glycol dimethacrylate, and the solvent is a mixture of trifluorotoluene and isopropyl alcohol, with a mass ratio of 1:1.

[0058] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 50 seconds, and then place it at 55°C for 10 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0059] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, and preferably 0.22 μm in this embodiment.

[0060] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 250 nm, the cross-linking temperature was 40°C, the cross-linking time was 15 min, and the cross-linking was completed and then dried to obtain a hydrophobic polyethersulfone porous membrane.

[0061] Comparative Example 2

[0062] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0063] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.3 parts of an initiator, 2 parts of a hydrophobic monomer, 3 parts of a cross-linking agent, and 70 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0064] The initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, the hydrophobic monomer is 2-perfluorododecylethyl methacrylate, the crosslinking agent is ethylene glycol dimethacrylate, and the solvent is a mixture of trifluorotoluene and isopropyl alcohol, with a mass ratio of 1:1.

[0065] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 50 seconds, and then place it at 55°C for 10 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0066] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, and preferably 0.22 μm in this embodiment.

[0067] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 250 nm, the cross-linking temperature was 40°C, the cross-linking time was 15 min, and the cross-linking was completed and then dried to obtain a hydrophobic polyethersulfone porous membrane.

[0068] Comparative Example 3

[0069] A method for preparing a hydrophobically modified polyethersulfone porous membrane comprises the following steps:

[0070] S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.8 parts of an initiator, 20 parts of a hydrophobic monomer, 22 parts of a cross-linking agent, and 60 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups;

[0071] The initiator is 1-hydroxycyclohexyl phenyl ketone, the hydrophobic monomer is perfluorodecyl ethyl acrylate, the crosslinking agent is ethylene glycol diacrylate, and the solvent is a mixture of trifluorotoluene and ethanol, with a mass ratio of 1:1.

[0072] S2 cross-linking pretreatment: dip-coat, spray-coat, or spin-coat the hydrophobic modification solution in S1 onto the polyethersulfone base membrane for 120 seconds, and then place it at 70°C for 5 minutes to remove excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane;

[0073] The pore size of the polyethersulfone-based membrane is 0.02 μm to 10 μm, and preferably 0.22 μm in this embodiment.

[0074] S3 cross-linking: The pre-cross-linked membrane was cross-linked under ultraviolet irradiation with a wavelength of 300 nm, the cross-linking temperature was 60°C, the cross-linking time was 10 min, and after the cross-linking was completed, it was dried to obtain a hydrophobic polyethersulfone porous membrane.

[0075] Comparative Example 4

[0076] A commercially available hydrophobic 0.22 μm PES membrane was selected, which was coated with a fluorine-based waterproofing agent on a hydrophilic PES membrane and then dried at high temperature.

[0077] In the above Examples 1-3 and Comparative Examples 2-3, the applicant's self-made polyethersulfone membrane was selected, Comparative Example 1 selected the hydrophilic polyethersulfone membrane of 3M Company, and Comparative Example 4 selected the hydrophobic polyethersulfone membrane of Xinna Company.

[0078] Hydrophobic polyethersulfone membrane performance test

[0079] 1. Contact angle test

[0080] The contact angle of the film surface was measured using an SDC-100 contact angle meter.

[0081] 2. Microstructure

[0082] The membrane surface and cross-sectional morphology were observed using a scanning electron microscope Regulus 8100.

[0083] 3. The hydrophobic polyethersulfone membrane and the disc filter prepared from the membrane were tested for air flow rate and water resistance.

[0084] Table 1 Contact angle, air flow rate and water barrier properties of polyethersulfone membrane after hydrophobic modification

[0085]

[0086] Table 2 Air flow rate test of disc filter before and after ethanol treatment

[0087]

[0088] As can be seen from Table 1, the hydrophobically modified polyethersulfone porous membrane prepared in the embodiment of the present invention has excellent performance, high water barrier ability, and a water contact angle of >90°.

[0089] The air flow rate of the membrane decreased slightly before and after modification, indicating that the membrane had good air permeability. By comparing Example 2 with Comparative Example 1, it was found that the physical properties of the polyethersulfone porous membrane were basically the same before and after modification, regardless of whether the hydrophobic modification was performed using the homemade membrane or the commercially available hydrophilic membrane. This shows that the hydrophobic modification method of the present invention has universal applicability and can achieve excellent hydrophobic modification effects on polyethersulfone porous membranes.

[0090] By comparing Examples 1-3 with Comparative Examples 2-3, it was found that the ratio of the hydrophobically modified solution was not within the scope of the patent of the present invention, resulting in the overall performance of the hydrophobically modified polyethersulfone porous membrane not meeting the standards, or the water blocking pressure was significantly reduced, or the air flow rate was significantly reduced, which would seriously affect the usage.

[0091] By comparing Examples 1-3 with Comparative Example 4, it was found that the overall performance of the hydrophobically modified polyethersulfone porous membrane prepared in the examples of the present invention is better than that of the same type of commercially available membranes: under the same water blocking pressure, the hydrophobically modified polyethersulfone porous membrane of the present invention has a higher air flow rate and stronger hydrophobicity; and after being treated with 99% ethanol for 1 hour, the hydrophobicity of the modified membrane shown in the present invention remains basically unchanged, while the commercially available membrane changes from a hydrophobic membrane to a hydrophilic membrane, and has stronger tolerance.

[0092] like Figure 1 and Figure 2 As shown in the scanning electron microscope images, whether it is a homemade polyethersulfone membrane or a commercially available polyethersulfone membrane, the hydrophobic polyethersulfone porous membrane prepared by the hydrophobic modification method of the present invention has no change in membrane structure before and after modification, which indicates that the hydrophobic modification method of the present invention does not change the bulk structure of the membrane, but only changes the hydrophobicity of the membrane surface.

[0093] Table 2 shows the data of air flow rate before and after steam sterilization when the hydrophobic membranes of Example 2 and Comparative Example 4 were made into disc filters, and then treated with 99% ethanol for 1 hour and then dried, or without ethanol treatment. As shown in Table 2, the air flow rate of the hydrophobically modified polyethersulfone porous membrane prepared in Example 2 of the present invention after being made into a disc filter, whether or not it was treated with ethanol, was almost unchanged before and after steam sterilization; while the air flow rate of the filter prepared by the commercially available polyethersulfone porous membrane was basically unchanged before and after steam sterilization when it was not treated with ethanol, but was almost halved after being treated with ethanol. This shows that the modification method shown in the present invention is more excellent and has very high substitutability and economic value.

[0094] In summary, the method for hydrophobic modification of polyethersulfone membrane disclosed in the present application is based on the existing polyethersulfone hydrophilic membrane as the base membrane, and a hydrophobic cross-linked layer is covered on the outer surface and internal porous structure of the polyethersulfone. Cross-linking is formed by a cross-linking agent, and hydrophobic monomers are grafted onto the hydrophobic cross-linked coating, that is, the polyethersulfone porous membrane is cross-linked and hydrophobic modified. The membrane pores are not easily clogged, and the porosity of the porous membrane is not affected, so that the polyethersulfone porous membrane still has a large air flux.

[0095] Modification principle: cross-linking agent is a monomer containing multiple (at least 2) unsaturated bonds, and the unsaturated bonds are mainly carbon-carbon double bonds and carbon-carbon triple bonds. Addition polymerization occurs between the unsaturated bonds to form a spatial network structure, i.e., a hydrophobic cross-linked coating, which ensures that the hydrophobic cross-linked coating is firmly covered on the polyethersulfone porous structure and does not fall off. The hydrophobic monomer is an unsaturated monomer containing a hydrophobic group. The unsaturated monomer illustrates that the hydrophobic monomer also has an unsaturated bond (carbon-carbon double bond and carbon-carbon triple bond), which can undergo addition polymerization with the cross-linking agent, thereby accessing a certain number of hydrophobic groups. Compared with the prior art, the method disclosed in the present application can make the polyethersulfone membrane hydrophobically modified, and it will not become hydrophilic again because of the influence of solvents such as ethanol, and the tolerance is stronger; the microstructures such as the pore size and porosity of the membrane after modification by this method are not changed, and the basic performance of the membrane will not be greatly reduced. It is only the hydrophobic effect that is achieved, and the modification method is more universal.

[0096] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0097] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a hydrophobically modified polyethersulfone porous membrane, characterized in that: The following steps are involved: S1: preparing a hydrophobic modification solution: the hydrophobic modification solution is composed of the following components in parts by weight: 0.05-0.8 parts of an initiator, 4-15 parts of a hydrophobic monomer, 4-15 parts of a cross-linking agent, and 70-92 parts of a solvent; the hydrophobic monomer is an unsaturated monomer containing a hydrophobic group, and the cross-linking agent is a monomer containing multiple unsaturated functional groups; S2 cross-linking pretreatment: dip-coating, spraying or spin-coating the hydrophobic modification solution in S1 on the polyethersulfone base membrane for a certain period of time, and then removing excess hydrophobic modification solution on the polyethersulfone base membrane to form a pre-cross-linked membrane; S3 cross-linking: The pre-cross-linked membrane is cross-linked under ultraviolet irradiation at a temperature of 20-60°C for 10-30 minutes. After the cross-linking is completed, the membrane is dried to obtain a hydrophobic polyethersulfone porous membrane. The pre-crosslinked membrane formed by the crosslinking pretreatment is a hydrophobic crosslinked coating formed on the polyethersulfone base membrane, and the hydrophobic monomer is grafted onto the hydrophobic crosslinked coating under ultraviolet light irradiation; The hydrophobic cross-linked coating not only coats the outer surface of the polyethersulfone base membrane, but can also be impregnated into the internal porous structure of the polyethersulfone membrane, thereby finally preparing a hydrophobically modified polyethersulfone porous membrane.

2. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein The initiator in S1 is a free radical photoinitiator.

3. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 2, wherein The initiator is one or more of benzoin and its derivatives, benzophenones, α-hydroxyketones, acylphosphine oxides and thioxanthones.

4. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 3, wherein The initiator is 1-hydroxycyclohexylphenyl ketone or 2-hydroxy-2-methyl-1-phenyl-1-propanone.

5. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein The hydrophobic monomer in S1 is an unsaturated monomer containing a hydrophobic group.

6. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 5, wherein: The hydrophobic monomer in S1 is a perfluoroalkyl acrylate monomer or a fluorine-free acrylate monomer.

7. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 6, wherein: The perfluoroalkyl acrylate monomer is one or more of perfluoroalkyl ethyl acrylate, perfluorodecyl ethyl acrylate, 2-perfluorododecyl ethyl methacrylate, and perfluorohexyl ethyl chloroacrylate.

8. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein The cross-linking agent in S1 is a monomer containing multiple unsaturated bonds, and the unsaturated bonds are carbon-carbon double bonds and / or carbon-carbon triple bonds.

9. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 8, wherein: The crosslinking agent in S1 is an acrylate crosslinking agent.

10. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein The solvent in S1 is one or more of methanol, ethanol, isopropanol, propanol, butanol and trifluorotoluene.

11. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein: The pore size of the polyethersulfone-based membrane in S2 is 0.02 μm to 10 μm.

12. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein: The time of dipping, spraying or spin coating in S2 is 20-120 seconds, and then the film is placed at a temperature of 30-70° C. for 5-15 minutes to remove excess hydrophobic modification solution on the polyethersulfone-based membrane.

13. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein: The wavelength of the ultraviolet light in S3 is 200-300nm.

14. The method for preparing a hydrophobically modified polyethersulfone porous membrane according to claim 1, wherein: The water contact angle of the hydrophobically modified polyethersulfone porous membrane is greater than 90°.

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