A method for preparing a siloxane composite separation membrane

Abstract

The present invention discloses a method for preparing a siloxane composite separation membrane, belonging to the technical field of polymer separation membranes. Its technical characteristics are: a membrane-forming substance, siloxane, and an auxiliary agent are dissolved in a solvent to prepare a casting solution, which is then applied to a carrier by scraping, allowed to stand under certain humidity conditions to form a film, and then allowed to stand in water to obtain a siloxane composite separation membrane. The proportions of each component are as follows: 10 to 30 parts of a film-forming polymer; 1 to 10 parts of an auxiliary agent; 1 to 10 parts of siloxane; and 50 to 88 parts of a solvent. The composite separation membrane prepared by the present invention has a uniform surface layer of siloxane and a support layer of a membrane-forming substance at the bottom, which is a relatively ideal composite membrane structure. The technical process is simple and efficient, and the structure is controllable. Therefore, the membrane-forming technology has good prospects for promotion and application.

Description

Technical Field

[0001] The present invention relates to the field of polymer separation membranes, and in particular to a method for preparing a siloxane composite separation membrane. Background Art

[0002] Membrane separation technology is a new and highly efficient separation technology, and one of the most promising high-tech technologies of the 21st century. As a highly efficient separation, concentration, purification, and cleansing technology, the membrane separation process offers unparalleled advantages over traditional separation methods (such as evaporation, extraction, or ion exchange). Consequently, it has been widely used in desalination, environmental protection, petrochemicals, energy-saving technologies, clean production, medicine, food, and electronics. It is poised to become a crucial tool for addressing energy and resource scarcity and environmental crises, significantly promoting social, economic, and technological development. Numerous experts and scholars have conducted extensive research on the preparation, structure, modification, and performance of polymer separation membrane materials, driving the rapid development of membrane science.

[0003] In addition to homogeneous and asymmetric membranes, composite separation membranes, due to their unique composite structure, can combine the performance of two membrane materials, making them suitable for a variety of complex and demanding environments. For example, a high-strength polymer can be used as the base membrane, while a hydrophilic polymer can be used as the surface layer to withstand high-pressure separations. Alternatively, more common materials such as polypropylene and polyvinylidene fluoride can be used, while functional polyimide and tetrafluoroethylene can be used as the surface separation layer. This not only saves costs but also fully utilizes the performance of both membrane materials. Therefore, composite separation membranes have significant application prospects.

[0004] Currently, there are two main methods for preparing composite separation membranes: interfacial polymerization and surface coating. Both require two steps: preparing the base membrane in the first step and constructing the surface separation membrane in the second step. This results in complex processes and low efficiency. Therefore, to address these shortcomings, the present invention provides a simple and efficient method for preparing polymer separation composite membranes. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a convenient and efficient method for preparing a siloxane composite separation membrane.

[0006] The described method for preparing a convenient and efficient siloxane composite separation membrane features a method for blending siloxane with other film-forming polymers and additives to form a casting solution, which is then applied to a carrier under certain humidity conditions to induce the siloxane to migrate to the surface. Under the action of water vapor, a polycondensation reaction forms the membrane surface structure, resulting in a siloxane composite separation membrane. This technology offers advantages such as simplicity, efficiency, and structural control, and has promising prospects for widespread application.

[0007] The present invention provides a convenient and efficient method for preparing a siloxane composite separation membrane, which specifically comprises the following steps:

[0008] (1) Mixing a film-forming polymer, an additive, and silicone in a certain proportion, dissolving them in a solvent, and obtaining a uniform casting solution;

[0009] (2) applying the above-mentioned casting solution on the support, placing it under certain humidity conditions, and letting it stand for a period of time;

[0010] (3) Place the above-mentioned carrier in water to form a film.

[0011] Furthermore, the film-forming polymer is a material such as polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylonitrile (PAN), or polysulfone (PSF).

[0012] Furthermore, the auxiliary agent is ethanol, acetone, ether, etc.

[0013] Furthermore, the siloxane includes bis(3-triethoxysilylpropyl)amine (BTESPA), bis-(3-(triethoxysiloxane)propyl)-disulfide (TSDS), 1,2-bis(triethoxysilyl)ethane (BTESE), and the chemical structural formulas of the above-mentioned siloxane cross-linking modifiers are as follows:

[0014]

[0015] Furthermore, the mass fractions of the film-forming polymer, the auxiliary agent, the silicone, and the solvent are as follows: film-forming polymer: 10 to 30 parts;

[0016] Additives: 1 to 10 parts;

[0017] Silicone: 1-10 parts;

[0018] Solvent: 50-88 parts.

[0019] Furthermore, the humidity condition is 50-99%.

[0020] Furthermore, the standing time is 1 to 15 minutes.

[0021] Compared with the prior art, the siloxane composite film prepared by the above technology has the following beneficial effects:

[0022] (1) The preparation process of the siloxane composite membrane of the present invention is simple and efficient, and the composite membrane can be obtained in one step, which is easy to industrialize.

[0023] (2) The organic siloxane composite membrane prepared by the present invention has a controllable structure, and the siloxane skin layer is thin, continuous and uniform, which is an ideal composite membrane structure.

[0024] (3) The organic siloxane composite membrane prepared by the present invention has a strong bond between the siloxane skin layer and the supporting membrane and has stable performance.

[0025] In summary, the technology adopted in the present invention is simple, efficient and easy to industrialize; the prepared siloxane composite membrane has a reasonable structure and stable performance, so the technology has good prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Scanning electron microscopy image of the surface of the siloxane composite film of Example 5 of the present invention;

[0027] Figure 2 : Scanning electron microscope image of a cross section of the siloxane composite membrane of Example 5 of the present invention;

[0028] Figure 3 : XPS spectrum of the surface of the siloxane composite film of Example 5 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] Example 1:

[0031] A method for preparing a siloxane composite separation membrane, the method is as follows:

[0032] 1) Mix 10 parts of polyvinylidene fluoride, 1 part of acetone, 1 part of bis(3-triethoxysilylpropyl)amine, and 88 parts of DMF solvent and dissolve them uniformly;

[0033] 2) evenly apply the casting solution on the substrate;

[0034] 3) Place the substrate in a 50% humidity environment and let it sit for 1 minute;

[0035] 4) Immerse the substrate in water to form a film by phase separation.

[0036] Example 2:

[0037] A method for preparing a siloxane composite separation membrane, the method is as follows:

[0038] 1) 30 parts of polyamide, 10 parts of acetone, 10 parts of bis-(3-(triethoxysiloxane)propyl)-disulfide (TSDS), and 50 parts of DMAc solvent were mixed and dissolved uniformly;

[0039] 2) evenly apply the casting solution on the substrate;

[0040] 3) Place the substrate in an environment with 99% humidity and let it stand for 15 minutes;

[0041] 4) Immerse the substrate in water to form a film by phase separation.

[0042] Example 3:

[0043] 1) Mix 20 parts of polysulfone, 5 parts of diethyl ether, 5 parts of 1,2-bis(triethoxysilyl)ethane (BTESE), and 70 parts of THF solvent and dissolve them uniformly;

[0044] 2) evenly apply the casting solution on the substrate;

[0045] 3) Place the substrate in an environment with 70% humidity and let it stand for 10 minutes;

[0046] 4) Immerse the substrate in water to form a film by phase separation.

[0047] Example 4:

[0048] A method for preparing a siloxane composite separation membrane, the method is as follows:

[0049] 1) Mix 15 parts of polyacrylonitrile, 5 parts of acetone, 10 parts of bis(3-triethoxysilylpropyl)amine, and 70 parts of NVP solvent and dissolve them uniformly;

[0050] 2) evenly apply the casting solution on the substrate;

[0051] 3) Place the substrate in an environment with 99% humidity and let it stand for 5 minutes;

[0052] 4) Immerse the substrate in water to form a film by phase separation.

[0053] Example 5:

[0054] A method for preparing a siloxane composite separation membrane, the method is as follows:

[0055] 1) Mix 15 parts of polyvinylidene fluoride, 10 parts of ethanol, 5 parts of bis(3-triethoxysilylpropyl)amine, and 70 parts of DMF solvent and dissolve them uniformly;

[0056] 2) evenly apply the casting solution on the substrate;

[0057] 3) Place the substrate in an environment with 99% humidity and let it stand for 10 minutes;

[0058] 4) Immerse the substrate in water to form a film by phase separation.

[0059] like Figure 1 It can be seen that the siloxane composite separation membrane prepared by the method has micron pores on the surface, high porosity and uniform pore size; Figure 2 It can be seen that the membrane cross section presents an obvious asymmetric structure, the skin layer and the support layer are tightly bonded, there is no obvious interface, and it shows a strong bonding force; and the XPS spectrum of the composite membrane surface Figure 3The results showed that its main component was siloxane, indicating that during the membrane formation process, siloxane had the behavior of migrating and enriching to the membrane surface, thus a siloxane composite separation membrane could be obtained in one step.

Claims

1. A method for preparing a siloxane composite separation membrane, characterized in that: The steps include: (1) Mixing a film-forming polymer, an additive, and silicone in a certain proportion and dissolving them in a solvent to obtain a uniform casting solution; (2) applying the above casting solution on the support, placing it under certain humidity conditions, and letting it stand for a period of time; (3) placing the above-mentioned carrier in water to form a film; The siloxane is one of bis(3-triethoxysilylpropyl)amine, bis-(3-(triethoxysiloxane)propyl)-disulfide, and 1,2-bis(triethoxysilyl)ethane; the auxiliary agent is one of ethanol, acetone, and ether; The certain humidity condition in step (2) is a film-forming humidity range of 50 to 99%; and the film-forming standing time in step (2) is 1 to 15 minutes.

2. The method for preparing a siloxane composite separation membrane according to claim 1, wherein: The mass fractions of the film-forming polymer, the auxiliary agent, the siloxane, and the solvent in step (1) are as follows: the film-forming polymer: 10 to 30 parts; the auxiliary agent: 1 to 10 parts; Silicone: 1-10 parts; Solvent: 50~88 parts.

3. The method for preparing a siloxane composite separation membrane according to claim 1, wherein: The film-forming polymer is one of polyvinylidene fluoride, polyamide, polyacrylonitrile and polysulfone.

4. The method for preparing a siloxane composite separation membrane according to claim 1, wherein: The solvent is one of DMF, DMAc, THF and NVP.

5. A siloxane composite separation membrane, characterized in that: The composite separation membrane is prepared by the preparation method according to any one of claims 1 to 4, and comprises a firmly bonded silicone skin layer and a polymer support layer.

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