Long-acting non-destructive hydrophilic modification method of polytetrafluoroethylene separation membrane
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-20
- Publication Date
- 2026-08-04
AI Technical Summary
钠-萘处理液改性是较早用于聚四氟乙烯膜亲水化的方法，但是其具有强烈的腐蚀性，导致膜机械性能下降，难以实现“无损”改性
[0005] This application provides a long-lasting, non-destructive hydrophilic modification method for polytetrafluoroethylene separation membranes to solve the above-mentioned technical problems.
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Figure CN122499651A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of separation membrane materials technology, and in particular to a long-lasting, non-destructive hydrophilic modification method for polytetrafluoroethylene (PTFE) separation membranes. Background Technology
[0002] Polytetrafluoroethylene (PTFE) possesses excellent physicochemical stability, making it an ideal substrate for separation membranes. However, its strong hydrophobicity results in significant resistance to water transport within the membrane material. This often necessitates higher transmembrane pressures to maintain throughput, leading to high system energy consumption. Hydrophilic modification of PTFE membrane materials can effectively overcome these drawbacks.
[0003] From a practical application perspective, the hydrophilic modification methods for polytetrafluoroethylene (PTFE) membranes must meet two basic conditions: long-lasting and non-destructive. "Long-lasting" means that the modified functional components can stably exist on the membrane material, and the hydrophilicity and water flux of the PTFE membrane do not change significantly with operating time. Surfactants are frequently reported hydrophilic modifiers for PTFE membrane materials. Their hydrophobic ends adsorb onto the PTFE surface through hydrophobic interactions, while the hydrophilic ends face the fluid side to reduce water permeation resistance. PTFE membranes treated with surfactants initially have high water flux, but as operating time increases, the surfactant is gradually lost under shear forces, leading to a rapid decrease in hydrophilicity and water flux, indicating insufficient long-lasting modification. "Non-destructive" means that the modification process does not damage the intrinsic structure of the PTFE membrane. Sodium-naphthalene treatment solution modification was an early method used for hydrophilicating PTFE membranes, but its strong corrosiveness leads to a decline in membrane mechanical properties, making it difficult to achieve "non-destructive" modification.
[0004] Therefore, it is necessary to develop a new method for long-lasting, non-destructive hydrophilic modification of polytetrafluoroethylene separation membranes. Summary of the Invention
[0005] This application provides a long-lasting, non-destructive hydrophilic modification method for polytetrafluoroethylene separation membranes to solve the above-mentioned technical problems.
[0006] This application provides a method for long-lasting, non-destructive hydrophilic modification of a polytetrafluoroethylene (PTFE) separation membrane, the modification method comprising:
[0007] Impurities are removed from the polytetrafluoroethylene (PTFE) separation membrane to obtain a pretreated PTFE separation membrane;
[0008] The pretreated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of a surfactant to obtain an interface-activated polytetrafluoroethylene separation membrane. The surfactant is one or more of sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, and cocamidopropyl betaine.
[0009] The interface-activated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of an active monomer for crosslinking to obtain a preliminarily modified polytetrafluoroethylene separation membrane. The active monomer is 3-glycidyl etheroxypropyltrimethoxysilane.
[0010] The preliminarily modified polytetrafluoroethylene (PTFE) separation membrane is immersed in an aqueous solution of a crosslinking agent for secondary crosslinking, followed by rinsing and drying to complete the long-term, non-destructive hydrophilic modification of the PTFE separation membrane. The crosslinking agent is a water-soluble polymer containing multiple primary amine groups.
[0011] Furthermore, the mass concentration of the surfactant is 1 wt% to 3 wt%.
[0012] Furthermore, the pretreated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of surfactant for 12 hours.
[0013] Furthermore, the mass concentration of the active monomer is 6 wt% to 10 wt%, and the pH of the aqueous solution of the active monomer is 3.0.
[0014] Furthermore, the interface-activated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of the active monomer for 12 hours.
[0015] Furthermore, the water-soluble polymer is one or more of polylysine, branched polyethyleneimine, and polyethyleneamine.
[0016] Furthermore, the mass concentration of the crosslinking agent is 3 wt% to 5 wt%.
[0017] Furthermore, the preliminarily modified polytetrafluoroethylene separation membrane is immersed in an aqueous solution of a crosslinking agent for 12 hours.
[0018] The long-lasting, non-destructive hydrophilic modification method for polytetrafluoroethylene (PTFE) separation membranes provided in this application involves surfactant treatment, which activates the PTFE separation membrane interface, transforming it from an initial hydrophobic interface to a transitional hydrophilic interface. This facilitates the wetting of the membrane substrate by the aqueous solution in subsequent reactions. During the treatment with the active monomer aqueous solution, the methoxysilyl groups contained therein undergo hydrolysis and crosslinking (primary crosslinking) under acidic conditions, forming a preliminary hydrophilic network within the membrane substrate. During the treatment with the crosslinking agent aqueous solution, the multiple primary amine groups contained therein react with the epoxy groups in the active monomer. The cross-linking reaction of the groups forms covalent bonds (secondary cross-linking), which further strengthens the hydrophilic network formed by the cross-linking of methoxysilane. The hydrophilic network formed by the two cross-linkings has an interlocking and spatially interlocked positional relationship with the fibrils and nodes of the polytetrafluoroethylene separation membrane itself. The hydrophilic network is not easily lost under the action of hydraulic shear force, which endows the polytetrafluoroethylene separation membrane with long-term hydrophilicity. There are no chemical bonds between the hydrophilic network formed by the two cross-linkings and the polytetrafluoroethylene separation membrane body. The physical and chemical structure of the membrane material itself does not change during the modification process, realizing non-destructive modification. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of a long-lasting, non-destructive hydrophilic modification method for a polytetrafluoroethylene separation membrane provided in an embodiment of this application. Detailed Implementation
[0020] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other well-known modifications within the scope of the claims of the present invention.
[0021] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0022] Materials used in this invention: There are no special restrictions on the source of all raw materials in this invention and the following embodiments and comparative examples; they can be commercially available.
[0023] Figure 1 This is a schematic diagram of a long-lasting, non-destructive hydrophilic modification method for a polytetrafluoroethylene (PTFE) separation membrane provided in an embodiment of this application. Figure 1 As shown, the modification methods include:
[0024] Step S101: Remove impurities from the polytetrafluoroethylene separation membrane to obtain a pretreated polytetrafluoroethylene separation membrane.
[0025] In the embodiments of this specification, the following method is used to remove impurities from the polytetrafluoroethylene separation membrane:
[0026] The polytetrafluoroethylene (PTFE) separation membrane was immersed in ethanol for 2 hours to wash away impurities from the membrane surface and pores. The ethanol used was anhydrous ethanol.
[0027] Step S103: Immerse the pretreated polytetrafluoroethylene separation membrane in an aqueous solution of a surfactant to obtain an interface-activated polytetrafluoroethylene separation membrane. The surfactant is one or more of sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, and cocamidopropyl betaine.
[0028] In the embodiments of this specification, the mass concentration of the surfactant is 1 wt% to 3 wt%.
[0029] In the embodiments of this specification, the pretreated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of surfactant for 12 hours.
[0030] Step S105: Immerse the interface-activated polytetrafluoroethylene separation membrane in an aqueous solution of the active monomer to perform a crosslinking process, thereby obtaining a preliminarily modified polytetrafluoroethylene separation membrane. The active monomer is 3-glycidyl etheroxypropyltrimethoxysilane.
[0031] In the embodiments of this specification, the mass concentration of the active monomer is 6 wt% to 10 wt%, and the pH of the aqueous solution of the active monomer is 3.0.
[0032] In the embodiments of this specification, the interface-activated polytetrafluoroethylene separation membrane is immersed in the aqueous solution of the active monomer for 12 hours.
[0033] Step S107: Immerse the preliminarily modified polytetrafluoroethylene separation membrane in an aqueous solution of a crosslinking agent for secondary crosslinking, then rinse and dry to complete the long-term non-destructive hydrophilic modification of the polytetrafluoroethylene separation membrane. The crosslinking agent is a water-soluble polymer containing multiple primary amine groups.
[0034] In the embodiments described in this specification, the water-soluble polymer is one or more of polylysine, branched polyethyleneimine, and polyethyleneamine.
[0035] In the embodiments described in this specification, the mass concentration of the crosslinking agent is 3 wt% to 5 wt%.
[0036] In the embodiments of this specification, the preliminarily modified polytetrafluoroethylene separation membrane is immersed in an aqueous solution of a crosslinking agent for 12 hours.
[0037] The preliminarily modified polytetrafluoroethylene separation membrane was immersed in an aqueous solution of a crosslinking agent for secondary crosslinking. When rinsing and drying, it was rinsed three times with pure water and then dried at room temperature.
[0038] To further illustrate the present invention, the following detailed description of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane provided by the present invention is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0039] Example 1
[0040] The long-term, non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment includes the following steps:
[0041] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0042] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0043] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0044] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0045] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0046] Example 2
[0047] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0048] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0049] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of hexadecyltrimethylammonium bromide with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0050] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0051] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0052] Example 3
[0053] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0054] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0055] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of cocamidopropyl betaine with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0056] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0057] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0058] Example 4
[0059] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0060] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0061] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 1 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0062] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0063] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0064] Example 5
[0065] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0066] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0067] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 3 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0068] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0069] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0070] Example 6
[0071] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0072] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0073] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0074] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with pH 3.0 and a mass concentration of 6 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain the preliminarily modified polytetrafluoroethylene separation membrane.
[0075] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0076] Example 7
[0077] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0078] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0079] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0080] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with pH 3.0 and a mass concentration of 10 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain the preliminarily modified polytetrafluoroethylene separation membrane.
[0081] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0082] Example 8
[0083] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0084] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0085] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0086] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0087] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of branched polyethyleneimine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0088] Example 9
[0089] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0090] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0091] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0092] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with pH 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain the preliminarily modified polytetrafluoroethylene separation membrane.
[0093] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of 4wt% polyethyleneamine for 12 h, then rinsed with pure water 3 times and dried at room temperature to complete the hydrophilic modification.
[0094] Example 10
[0095] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0096] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0097] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0098] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0099] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 3wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0100] Example 11
[0101] The operation steps of the long-term non-destructive hydrophilic modification method for the polytetrafluoroethylene separation membrane in this embodiment are as follows:
[0102] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0103] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0104] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to obtain a preliminarily modified polytetrafluoroethylene separation membrane.
[0105] (4) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (3) is immersed in an aqueous solution of polylysine with a mass concentration of 5wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0106] Comparative Example 1
[0107] An unmodified polytetrafluoroethylene separation membrane was used as a comparative example 1.
[0108] Comparative Example 2
[0109] Using the case without interface activation as Comparative Example 2, the operation steps are as follows:
[0110] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0111] (2) First crosslinking: The pretreated polytetrafluoroethylene separation membrane obtained in step (2) was immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the pre-modified polytetrafluoroethylene separation membrane.
[0112] (3) Secondary crosslinking: The preliminarily modified polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of polylysine with a mass concentration of 4wt% for 12 h, then rinsed with pure water 3 times, and dried at room temperature to complete the hydrophilic modification.
[0113] Comparative Example 3
[0114] Comparative Example 3 uses cases without primary crosslinking and cases without secondary crosslinking as examples. The operation steps are as follows:
[0115] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0116] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h, then rinsed with pure water 3 times and dried at room temperature to complete the modification.
[0117] Comparative Example 4
[0118] Comparative Example 4 uses the case without secondary crosslinking as an example. The operation steps are as follows:
[0119] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0120] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0121] (3) First crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) is immersed in an aqueous solution of 3-glycidyl etheroxypropyltrimethoxysilane with a pH of 3.0 and a mass concentration of 8 wt% for 12 h. After completion, the residual solution is drained at room temperature to complete the modification.
[0122] Comparative Example 5
[0123] Comparative Example 5 uses the simultaneous occurrence of primary and secondary crosslinking, and the operation steps are as follows:
[0124] (1) Pretreatment: The polytetrafluoroethylene separation membrane was soaked in ethanol for 2 h to wash out impurities on the membrane surface and in the membrane pores, and the pretreated polytetrafluoroethylene separation membrane was obtained.
[0125] (2) Interface activation: The polytetrafluoroethylene separation membrane pretreated in step (1) was immersed in an aqueous solution of sodium dodecyl sulfonate with a mass concentration of 2 wt% for 12 h. After completion, the residual solution was drained at room temperature to obtain the interface activated polytetrafluoroethylene separation membrane.
[0126] (3) Crosslinking: The interface-activated polytetrafluoroethylene separation membrane obtained in step (2) was immersed in an aqueous solution of tris(hydroxymethyl)aminomethane (Tris) with pH 8.5, 3-glycidyl etheroxypropyltrimethoxysilane at a mass concentration of 8 wt%, and polylysine at a mass concentration of 4 wt% for 12 h. After completion, it was heat-treated at 80℃ for 12 h, then rinsed with pure water 3 times and dried at room temperature to complete the hydrophilic modification.
[0127] Test Example 1
[0128] The polytetrafluoroethylene separation membranes corresponding to Examples 1-11 and Comparative Examples 1-4 were used as samples for water contact angle testing. The testing method is as follows:
[0129] The contact angle of the membrane material surface was determined using the static drop method. A drop of pure water was carefully added to the fully dried membrane material, and the contact angle value was recorded after 15 seconds. Five different locations were tested for each sample, and the average value was taken as the final result. The measured water contact angle data are shown in Table 1. A smaller contact angle indicates better hydrophilicity of the membrane material.
[0130] Test Example 2
[0131] The polytetrafluoroethylene (PTFE) separation membranes corresponding to Examples 1-11 and Comparative Examples 1-4 were used as samples for pure water flux testing. The testing method was as follows: Three PTFE separation membrane materials were placed into a Φ 8×250 mm membrane shell, and the ends were sealed with epoxy resin. After curing for 24 hours, a membrane filter was obtained. External pressure filtration was used, and the amount of water passing through a unit membrane area per unit time was calculated at a test pressure of 1 bar. The initial flux was recorded, and the flux decay rate after 24 hours of operation was calculated. The lower the flux decay rate, the better the long-term effectiveness of the hydrophilic modification. The measured data are shown in Table 1. Each sample was measured three times in parallel according to the above method, and the average value was taken as the final result.
[0132] Table 1. Water contact angle, initial pure water flux, and 24-h flux decay rate of the polytetrafluoroethylene (PTFE) separation membrane.
[0133]
[0134] Comparing the data from Examples 1 to 3 in Table 1, the polytetrafluoroethylene (PTFE) separation membrane in Example 1 exhibits a smaller water contact angle, higher pure water flux, and a lower 24-hour flux decay rate. Therefore, sodium dodecyl sulfate is the optimal surfactant used in the interface activation process.
[0135] Comparing the data from Examples 1, 4, and 5 in Table 1, it was found that when the surfactant concentration was increased from 1 wt% to 2 wt% during the interface activation process, the water contact angle of the polytetrafluoroethylene (PTFE) membrane decreased, the pure water flux increased, and the 24-hour flux decay rate decreased. When the surfactant concentration was increased to 3 wt%, the membrane performance remained essentially unchanged. From an economic perspective, a surfactant concentration of 2 wt% is optimal during the interface activation process.
[0136] Comparing the data from Examples 1, 6, and 7 in Table 1, it was found that when the active monomer concentration was increased from 6 wt% to 8 wt% during the single crosslinking process, the water contact angle of the PTFE separation membrane decreased, the pure water flux increased, and the 24-hour flux decay rate decreased. When the surfactant concentration was increased to 10 wt%, the water contact angle of the PTFE separation membrane remained almost unchanged, but the pure water flux decreased and the 24-hour flux decay rate slightly increased. Therefore, an active monomer concentration of 8 wt% is optimal during the single crosslinking process.
[0137] Comparing the data from Examples 1, 8, and 9 in Table 1, the polytetrafluoroethylene (PTFE) separation membrane of Example 1 exhibits a smaller water contact angle, higher pure water flux, and lower 24-hour flux decay rate. Therefore, polylysine is the optimal crosslinking agent for the secondary crosslinking process.
[0138] Comparing the data from Examples 1, 10, and 11 in Table 1, it was found that when the crosslinking agent concentration was increased from 3 wt% to 4 wt% during the secondary crosslinking process, the water contact angle of the PTFE separation membrane decreased, the pure water flux increased, and the 24-hour flux decay rate decreased. When the crosslinking agent concentration was increased to 5 wt%, the water contact angle and 24-hour flux decay rate of the PTFE separation membrane remained almost unchanged, but the pure water flux decreased. Therefore, a crosslinking agent concentration of 4 wt% is optimal during the secondary crosslinking process.
[0139] Comparing the data of Examples 1 to 11 in Table 1 with Comparative Example 1, the polytetrafluoroethylene separation membranes of Examples 1 to 11 have smaller water contact angles and higher pure water flux, indicating that the technical solution of the present invention is very effective.
[0140] Comparing the data of Examples 1 to 11 in Table 1 with Comparative Example 2, the polytetrafluoroethylene separation membranes of Examples 1 to 11 have smaller water contact angles and higher pure water flux, indicating that the interface activation step is essential.
[0141] Comparing the data of Examples 1 to 11 in Table 1 with Comparative Example 3, the polytetrafluoroethylene separation membranes of Examples 1 to 11 have smaller water contact angles, higher pure water flux, and lower 24-hour flux decay rates. Comparing the data of Examples 1 to 11 in Table 1 with Comparative Example 4, the polytetrafluoroethylene separation membranes of Examples 1 to 11 have lower 24-hour flux decay rates. The above results indicate that the primary and secondary crosslinking steps are essential.
[0142] Comparing the data of Examples 1 to 11 in Table 1 with Comparative Example 5, the polytetrafluoroethylene separation membranes of Examples 1 to 11 have smaller water contact angles, higher pure water flux, and lower 24-hour flux decay rates, indicating that it is essential to perform the primary crosslinking and secondary crosslinking steps in separate steps.
[0143] The long-lasting, non-destructive hydrophilic modification method for polytetrafluoroethylene (PTFE) separation membranes provided in this application involves surfactant treatment, which activates the PTFE separation membrane interface, transforming it from an initial hydrophobic interface to a transitional hydrophilic interface. This facilitates the wetting of the membrane substrate by the aqueous solution in subsequent reactions. During the treatment with the active monomer aqueous solution, the methoxysilyl groups contained therein undergo hydrolysis and crosslinking (primary crosslinking) under acidic conditions, forming a preliminary hydrophilic network within the membrane substrate. During the treatment with the crosslinking agent aqueous solution, the multiple primary amine groups contained therein react with the epoxy groups in the active monomer. The cross-linking reaction of the groups forms covalent bonds (secondary cross-linking), which further strengthens the hydrophilic network formed by the cross-linking of methoxysilane. The hydrophilic network formed by the two cross-linkings has an interlocking and spatially interlocked positional relationship with the fibrils and nodes of the polytetrafluoroethylene separation membrane itself. The hydrophilic network is not easily lost under the action of hydraulic shear force, which endows the polytetrafluoroethylene separation membrane with long-term hydrophilicity. There are no chemical bonds between the hydrophilic network formed by the two cross-linkings and the polytetrafluoroethylene separation membrane body. The physical and chemical structure of the membrane material itself does not change during the modification process, realizing non-destructive modification.
[0144] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation. It should be noted that those skilled in the art can make other variations or modifications without departing from the principles of the present invention, and any obvious variations or modifications derived therefrom are still within the protection scope of the present invention.
Claims
1. A method for long-lasting, non-destructive hydrophilic modification of a polytetrafluoroethylene (PTFE) separation membrane, characterized in that, The modification method includes: Impurities are removed from the polytetrafluoroethylene (PTFE) separation membrane to obtain a pretreated PTFE separation membrane; The pretreated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of a surfactant to obtain an interface-activated polytetrafluoroethylene separation membrane. The surfactant is one or more of sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, and cocamidopropyl betaine. The interface-activated polytetrafluoroethylene separation membrane is immersed in an aqueous solution of an active monomer for crosslinking to obtain a preliminarily modified polytetrafluoroethylene separation membrane. The active monomer is 3-glycidyl etheroxypropyltrimethoxysilane. The preliminarily modified polytetrafluoroethylene (PTFE) separation membrane is immersed in an aqueous solution of a crosslinking agent for secondary crosslinking, followed by rinsing and drying to complete the long-term, non-destructive hydrophilic modification of the PTFE separation membrane. The crosslinking agent is a water-soluble polymer containing multiple primary amine groups.
2. The modification method as described in claim 1, characterized in that, The mass concentration of the surfactant is 1 wt% to 3 wt%.
3. The modification method as described in claim 1, characterized in that, The pretreated polytetrafluoroethylene separation membrane was immersed in an aqueous solution of surfactant for 12 hours.
4. The modification method as described in claim 1, characterized in that, The active monomer has a mass concentration of 6 wt% to 10 wt%, and the pH of the aqueous solution of the active monomer is 3.
0.
5. The modification method as described in claim 1, characterized in that, The interface-activated polytetrafluoroethylene separation membrane was immersed in an aqueous solution of the active monomer for 12 hours.
6. The modification method as described in claim 1, characterized in that, The water-soluble polymer is one or more of polylysine, branched polyethyleneimine, and polyethyleneamine.
7. The modification method as described in claim 1, characterized in that, The mass concentration of the crosslinking agent is 3 wt% to 5 wt%.
8. The modification method as described in claim 1, characterized in that, The preliminarily modified polytetrafluoroethylene separation membrane was immersed in an aqueous solution of a crosslinking agent for 12 hours.