A pore and permeation depth controllable PDMS gas separation composite membrane and a preparation method thereof

Abstract

The application discloses a PDMS gas separation composite membrane with controllable pore penetration depth and a preparation method thereof, and steps are as follows: 1) dissolving silicone oil, a crosslinking agent and a catalyst in a solvent to prepare a PDMS coating solution, 2) S2, wetting-extraction pretreatment is performed on a base film, 3) the PDMS is coated on the surface of the base film and solidified into a film, and 4) the composite film is extracted and dried; the PDMS gas separation composite membrane with controllable pore penetration depth is prepared by adopting the preparation method, the composite film with an ultrathin selection layer and uniform and complete PDMS can be prepared, the gas permeation performance of the PDMS composite film is improved, and the generation of the film with a hole defect is avoided; in addition, the PDMS composite film has the controllable pore penetration depth by the wetting-extraction pretreatment method on the base film in advance, the peeling force between the PDMS selection layer and the base film is improved, the PDMS composite film is more stable and durable in actual application, the practical application value of the PDMS composite film is improved, and the film replacement cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas separation composite membrane, and particularly relates to a PDMS gas separation composite membrane with controllable pore penetration depth and a preparation method thereof. BACKGROUND

[0002] Composite membrane technology is widely used in the preparation of reverse osmosis membranes (RO), nanofiltration membranes (NF), gas separation membranes and pervaporation membranes (PV). The composite membrane is usually composed of a porous support layer and a dense separation layer. The porous support layer provides mechanical strength, and the separation layer determines the separation performance of the composite membrane, which not only ensures the separation performance, but also has a high enough permeation flux. Therefore, the composite membrane shows sustained competitiveness in the commercial market.

[0003] Gas separation membrane is a new technology that has developed rapidly in recent years. Different polymer membranes have different permeation rates and selectivities for different types of gas molecules, so they can be selected to separate a certain gas from a gas mixture. Thomas Graham proposed the famous Graham's Law of Diffusion in 1850, which laid the theoretical foundation for the development of gas separation membranes. Since then, between the 1940s and the 1950s, Barrer and others have gradually perfected the theoretical basis of contemporary gas separation membranes, namely the solution-diffusion theory. This theory is still widely used to describe and explain the mechanism of gas permeation and transmission in dense membrane materials. In 1980, Monsanto Company first developed a membrane separation system named and applied it to hydrogen production. After that, various types of gas separation membranes have been developed and used in natural gas purification, nitrogen separation, H2 separation, CO2 capture and other fields. In recent years, the application range of gas membrane separation has rapidly expanded, and the cost competitiveness has gradually improved. In the foreseeable future, membrane separation technology will continue to develop rapidly and gradually replace some traditional separation technologies.

[0004] Polydimethylsiloxane (PDMS) has high gas permeability, high thermal stability, good mechanical properties and cost-effectiveness, and is a gas separation membrane material. Currently, the main preparation method of PDMS gas separation composite membrane is coating method, but the traditional coating preparation method will form pore penetration phenomenon due to the invasion of the separation layer into the pores of the porous support layer, which not only leads to low gas permeation flux, but also causes poor separation performance due to pinholes or defects. Therefore, it is necessary to improve the coating method of the traditional PDMS gas separation composite membrane and propose a preparation method that can effectively control the pore penetration. SUMMARY

[0005] The application aims to provide a pore and permeation depth controllable PDMS gas separation composite membrane preparation method.

[0006] Another object of the application is to provide a pore and permeation depth controllable PDMS separation composite membrane prepared by the above preparation method.

[0007] To this end, the technical scheme of the application is as follows:

[0008] A pore and permeation depth controllable PDMS gas separation composite membrane preparation method, the steps are as follows:

[0009] S1, dissolving silicon oil, cross-linking agent and catalyst in a solvent to prepare a PDMS coating solution; wherein the silicon oil is vinyl silicone oil, hydroxyl silicone oil or alkoxy-terminated silicone oil with a molecular weight of 500-100000 g / mol; the cross-linking agent is tetraethyl orthosilicate, tetramethoxysilane, methyltrimethoxysilane or hydrogen-containing silicone oil with a hydrogen content of 0.03-1.6%;

[0010] S2, immersing the base film in a wetting agent for 5-24 hours, then placing it in an extracting agent for 2-30 seconds, and then drying it in an oven at 60 DEG C for 30 minutes to prepare a pretreated base film; wherein the wetting agent is glycerol or paraffin oil; the extracting agent is water, ethanol, methanol, isopropyl alcohol, petroleum ether or n-hexane;

[0011] S3, pouring the PDMS coating solution prepared in step S1 on the surface of the pretreated base film prepared in step S2, uniformly coating the PDMS coating solution on the surface of the base film by using a doctor blade, and placing it in an oven to dry at 60 DEG C for 5 minutes first, and then heating to 80-150 DEG C to cure and cross-link for 60 minutes;

[0012] S4, immersing the PDMS composite film cured in step S3 in an extracting agent for 12-24 hours, and then drying it for standby use.

[0013] In the preparation method of the present application, since the PDMS film can improve its adhesion to the base film by invading the voids of the base film, and the use of coating method to composite the PDMS film on the base film will cause pore penetration to cause the performance of the composite film to decline, therefore, in step S2, the base film is pretreated with a wetting agent, that is, the pores on the base film are filled, and then the wetting agent on the surface of the base film and the wetting agent at the port of the base film pores are removed by an extracting agent, and then the PDMS coating solution prepared in step S1 is coated on the base film to form a film, which not only effectively prevents the problem of pore penetration, ensures the film-forming property and permeability of the PDMS film, and can realize the preparation of a thin composite film; at the same time, the PDMS coating solution can also invade the base film pores at the port of the base film pores by using the pore penetration phenomenon, and improve the adhesion between the porous support layer and the dense separation layer, to avoid the PDMS film from separating from the base film; specifically, the wetting agent uses glycerol or paraffin oil, both of which have the advantages of ① good affinity with the base film, and will not cause the base material to dissolve or swell, ② the pre-wetting agent is not soluble with the casting liquid, but is soluble in the extracting agent, ③ easy to remove; in addition, since the wetting agent has a high boiling point, it can further improve the film-forming temperature of the composite film from 50℃ to 60℃ as defined by the traditional coating method to 80℃ to 150℃, thereby further shortening the crosslinking and curing time of the composite film and improving the production efficiency of the composite film.

[0014] Preferably, in step S1, the weight ratio of the silicone oil, the crosslinking agent and the catalyst is (1-20):1:(0.01-0.5).

[0015] Preferably, in step S1, the catalyst uses platinum gold catalyst or organic tin catalyst.

[0016] Preferably, in step S1, the solvent is n-hexane, n-heptane, chloroform, dichloromethane, or toluene.

[0017] Preferably, in step S1, after adding the silicone oil, the crosslinking agent and the catalyst into the solvent, first stir at -30℃ to 25℃ for 5min to 60min, and then stand at -30℃ to 5℃ for 30min to 12h to remove bubbles.

[0018] Preferably, in step S2, the base film uses polyvinylidene fluoride (PVDF) base film, polysulfone (PSF) base film, polyacrylonitrile (PAN) base film, polypropylene (PP) base film, polyethylene (PE) base film, polytetrafluoroethylene (PTFE) base film, polyether sulfone (PES) base film, sulfonated polyether sulfone (SPES) base film, polyimide (PI) base film, or polyetherimide (PEI) base film.

[0019] Preferably, before step S2, the base film is first soaked in deionized water for at least 24h, and then dried in an oven at 60℃ to 100℃ for 12h to 24h.

[0020] Preferably, in step S3, the doctor knife adopts a doctor knife gap of 10-300 μm.

[0021] Preferably, in step S4, the composite film treated by the extracting agent is dried in an oven at 60-100 °C for 12-24 h.

[0022] A PDMS gas separation composite film with controllable pore penetration depth prepared according to the above preparation method.

[0023] Compared with the prior art, the PDMS gas separation composite film preparation method with controllable pore penetration depth can prepare a composite film with an ultra-thin selective layer and uniform and complete PDMS, improve the gas permeability of the PDMS composite film, and eliminate the production of defective films with holes; in addition, through the pre-treatment method of wetting-extraction of the base film, the PDMS composite film also has a controllable pore penetration depth, improves the peeling force of the PDMS selective layer and the base film, makes the PDMS composite film more stable and durable in practical application, improves the practical application value of the PDMS composite film, and reduces the cost of film replacement. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 An ethanol section electron microscope graph of the PDMS gas separation composite film prepared for Example 1 of the present application;

[0025] Figure 2 A section electron microscope graph of the PDMS gas separation composite film prepared for Comparative Example 1 of the present application;

[0026] Figure 3 A section electron microscope graph of the PDMS gas separation composite film prepared for Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0027] The present application will be further described below in combination with the drawings and specific examples, but the following examples are by no means any limitation on the present application. In the following examples, the chemical reagents used in each preparation step are all commercially available products.

[0028] Example 1

[0029] A PDMS gas separation composite film, the preparation steps of which are as follows:

[0030] S1, 10 g of vinyl silicone oil (molecular weight 1000 g / mol), 1 g of hydrogen-containing silicone oil (hydrogen content 1.6%), and 0.15 g of platinum gold catalyst were dissolved in 209 g of n-hexane, stirred at -10 °C for 30 min, and then placed at -30 °C for 1 h to prepare a PDMS coating solution;

[0031] S2, the PSF base film is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film is first soaked in glycerol for 24 h, and then placed in deionized water for 5 s, and then dried in an oven at 60°C for 30 min to obtain a pretreated PSF base film;

[0032] S3, the PDMS coating solution prepared in step S1 is poured onto the surface of the pretreated PSF base film prepared in step S2, and a 50 μm spatula is used to uniformly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution is placed in an oven, and first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0033] S4, the PDMS composite film obtained by curing in step S3 is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0034] Example 2

[0035] A PDMS gas separation composite film is prepared by the following steps:

[0036] S1, 10 g of vinyl silicone oil (molecular weight 1000 g / mol), 1 g of hydrogen-containing silicone oil (hydrogen content 1.6%), and 0.15 g of platinum gold catalyst are dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then placed at -30°C for 1 h to obtain a PDMS coating solution;

[0037] S2, the PSF base film is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film is first soaked in glycerol for 24 h, and then placed in ethanol for 30 s, and then dried in an oven at 60°C for 30 min to obtain a pretreated PSF base film;

[0038] S3, the PDMS coating solution prepared in step S1 is poured onto the surface of the pretreated PSF base film prepared in step S2, and a 25 μm spatula is used to uniformly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution is placed in an oven, and first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 10 min;

[0039] S4, the PDMS composite film obtained by curing in step S3 is soaked in ethanol for 24 h, and then dried in an oven at 60°C for 12 h.

[0040] Example 3

[0041] A PDMS gas separation composite film is prepared by the following steps:

[0042] S1, 10 g of vinyl silicone oil (molecular weight 100000 g / mol), 1 g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.1 g of platinum gold catalyst were dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then left to stand at -30°C for 1 h to prepare a PDMS coating solution;

[0043] S2, the PSF base film was soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film was first soaked in paraffin oil for 5 min, then placed in deionized water for 5 s, and then dried in an oven at 60°C for 30 min to prepare a pretreated PSF base film;

[0044] S3, the PDMS coating solution prepared in step S1 was poured onto the surface of the pretreated PSF base film prepared in step S2, and a 50 μm spatula was used to evenly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution was placed in an oven, first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0045] S4, the PDMS composite film obtained by curing in step S3 was soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0046] Example 4

[0047] A PDMS gas separation composite film was prepared by the following steps:

[0048] S1, 10 g of vinyl silicone oil (molecular weight 10000 g / mol), 1 g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.1 g of platinum gold catalyst were dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then left to stand at -30°C for 1 h to prepare a PDMS coating solution;

[0049] S2, the PE base film was soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film was first soaked in paraffin oil for 5 min, then placed in deionized water for 5 s, and then dried in an oven at 60°C for 30 min to prepare a pretreated PE base film;

[0050] S3, the PDMS coating solution prepared in step S1 was poured onto the surface of the pretreated PSF base film prepared in step S2, and a 50 μm spatula was used to evenly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution was placed in an oven, first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0051] S4, the PDMS composite film obtained by curing in step S3 was soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0052] Example 5

[0053] A PDMS gas separation composite membrane is prepared by the following steps:

[0054] S1, 10 g of hydroxyl silicone oil (molecular weight 10000 g / mol), 0.5 g of ethyl silicate, and 0.1 g of dibutyltin dilaurate are dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then placed at -30°C for 1 h to prepare a PDMS coating solution;

[0055] S2, the PSF base film is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film is first soaked in paraffin oil for 5 min, then placed in deionized water for 5 s, and then dried in an oven at 60°C for 30 min to prepare a pretreated PSF base film;

[0056] S3, the PDMS coating solution prepared in step S1 is poured onto the surface of the pretreated PSF base film prepared in step S2, and a 25 μm spatula is used to evenly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution is placed in an oven, first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0057] S4, the PDMS composite film obtained by curing in step S3 is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0058] Comparative Example 1

[0059] A PDMS gas separation composite membrane is prepared by the following steps:

[0060] S1, 10 g of hydroxyl silicone oil (molecular weight 10000 g / mol), 0.5 g of ethyl silicate, and 0.1 g of dibutyltin dilaurate are dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then placed at -30°C for 1 h to prepare a PDMS coating solution;

[0061] S2, the PSF base film is soaked in deionized water for 24 h, and then the water droplets on the surface are wiped off to prepare a pretreated PSF base film;

[0062] S3, the PDMS coating solution prepared in step S1 is poured onto the surface of the pretreated PSF base film prepared in step S2, and a 25 μm spatula is used to evenly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution is placed in an oven, first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0063] S4, the PDMS composite membrane obtained by curing in step S3 is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0064] Comparative Example 2

[0065] A PDMS gas separation composite membrane is prepared by the following steps:

[0066] S1, 10 g of vinyl silicone oil (molecular weight 1000 g / mol), 1 g of hydrogen-containing silicone oil (hydrogen content 1.6%), and 0.15 g of platinum gold catalyst are dissolved in 209 g of n-hexane, stirred at -10°C for 30 min, and then placed at -30°C for 1 h to prepare a PDMS coating solution;

[0067] S2, the PSF base film is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h; the dried film is first soaked in glycerol for 24 h, then taken out and dried in an oven at 60°C for 30 min to prepare a pretreated PSF base film;

[0068] S3, the PDMS coating solution prepared in step S1 is poured onto the surface of the pretreated PSF base film prepared in step S2, and a 50 μm doctor blade is used to uniformly coat the PDMS coating solution on the surface of the PSF base film; the PSF base film coated with the PDMS coating solution is placed in an oven, first dried at 60°C for 5 min, and then heated to 150°C for crosslinking for 60 min;

[0069] S4, the PDMS composite membrane obtained by curing in step S3 is soaked in deionized water for 24 h, and then dried in an oven at 60°C for 12 h.

[0070] Performance test:

[0071] The performance of the PDMS gas separation composite membranes prepared in Examples 1-5 and Comparative Examples 1-2 is tested, including composite membrane separation performance test and peel strength test; specifically,

[0072] (1) The separation coefficient and gas permeation flux are used to characterize the membrane separation performance, and the calculation formula is:

[0073]

[0074]

[0075] In the above two formulas, Q is the gas flow (cm 3 / min), L is the membrane thickness (cm), P is the gas permeation flux, and the unit is GPU (1 GPU = 10 -6 cm 3 (STP) / (cm 2• s • cm Hg), P / L is the gas permeance, ΔP is the pressure difference (cm Hg) ; a A / B is the separation factor, which is the ratio of the permeation fluxes of gas A and gas B;

[0076] (2) Composite film peeling strength test method:

[0077] The PET film is pasted on the upper and lower surfaces of the composite film with polyurethane adhesive, then the load and peeling distance are recorded using a universal testing machine, and the average load is compared. The specific peeling force F peel The calculation method is as follows:

[0078]

[0079] In the formula, F 0.2 and F 0.8 are the force values corresponding to 20% and 80% of the displacement value, respectively.

[0080] The specific test results are shown in Table 1.

[0081] Table 1:

[0082] Examples [P(02)(GPU)] [P(N2)(GPU)] Separation coefficient Peeling force (N) Example 1 473.7 217.3 2.18 0.072 Example 2 498.6 231.9 2.15 0.104 Example 3 516.6 241.4 2.14 0.056 Example 4 731.5 337.1 2.17 0.113 Example 5 461.3 214.6 2.15 0.061 Comparative Example 1 196.4 116.2 1.69 -- Comparative Example 2 569.3 263.6 2.16 0.028

[0083] As can be seen from the test results in Table 1, the PDMS gas separation composite film prepared in Examples 1-5 can be prepared to have a higher permeation flux and form a defect-free separation layer surface by using a pre-wetting agent to block the pores. Moreover, the preparation of the PDMS composite film at a higher temperature does not cause the phenomenon of increased pore penetration due to the volatilization of the pre-wetting agent. In addition, the preparation method utilizes the control of pore penetration, and the peeling force is obviously improved, which can increase the service life of the composite film.

[0084] Compared with Example 1, the PDMS gas separation composite film prepared in Comparative Example 1 does not have the extraction pre-wetting agent treatment step for the base film, resulting in the presence of pinhole defects on the surface of the PDMS film during the compounding process with the base film due to the pore penetration problem, and the interface between the composite films is blurred, and the peeling force cannot be measured. The PDMS gas separation composite film prepared in Comparative Example 2 is only wetted on the base film without subsequent extraction treatment step, resulting in that the PDMS film cannot utilize the micropore penetration to generate good adhesion with the base film, the peeling force of the composite film is low, and the PDMS film is easily separated from the base film.

[0085] As Figure 1The image shows a cross-sectional electron microscope (EMS) image of the PDMS gas separation composite membrane prepared in Example 1. As can be seen from the image, a uniform dense PDMS layer is formed on the surface of the PSF base membrane. However, no clear boundary is observed between the PSF base membrane and the dense PDMS layer. This is because the wetting agent in the pores of the PSF base membrane is partially extracted and removed, allowing the PDMS coating solution to penetrate into the pores of the PSF base membrane that are not occupied by the wetting agent, forming a strong transition layer with the base membrane.

[0086] like Figure 2 The image shows a cross-sectional electron microscope (EM) image of the PDMS gas separation composite membrane prepared in Comparative Example 1. As can be seen from the image, when water with a boiling point of 100℃ is used as a wetting agent, and the membrane is cured at 150℃, the water evaporates instantly. Because the PDMS coating solution has not yet fully cured, it penetrates the entire PSF membrane layer, resulting in severe porosity and causing serious defects in the PDMS separation layer.

[0087] like Figure 3 The image shows a cross-sectional electron microscope (EM) image of the PDMS gas separation composite membrane prepared in Comparative Example 2. As can be seen from the image, unlike Example 1 where the pre-wetting agent in the base membrane was extracted, resulting in a clear transition layer between the PDMS layer and the base membrane, the PDMS composite membrane in Comparative Example 2, which was not extracted, lacks a clear pore-permeability transition layer. This leads to weak adhesion between the PDMS layer and the base membrane.

[0088] In summary, the gas separation composite membrane prepared by the method of this application can not only improve the bonding force between the PDMS layer and the base membrane, thus improving the stability of the composite membrane during application, but also prevent the composite membrane's permeability performance from declining due to severe pore leakage.

[0089] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth, characterized in that, The steps are as follows: S1. Dissolve silicone oil, crosslinking agent, and catalyst in a solvent to prepare PDMS coating solution; wherein the silicone oil is vinyl silicone oil, hydroxyl silicone oil, or alkoxy-terminated silicone oil with a molecular weight of 500 g / mol to 100,000 g / mol; the crosslinking agent is tetraethyl orthosilicate, tetramethoxysilane, methyltrimethoxysilane, or hydrogen-containing silicone oil with a hydrogen content of 0.03% to 1.6%; S2. The base film is first soaked in a wetting agent for 5 min to 24 h, then placed in an extractant for 2 s to 30 s, and then dried in an oven at 60 ℃ for 30 min to obtain a pretreated base film; wherein the wetting agent is glycerol or paraffin oil; the extractant is water, ethanol, methanol, isopropanol, petroleum ether or n-hexane; S3. Pour the PDMS coating liquid obtained in step S1 onto the surface of the pretreated base film obtained in step S2. Use a scraper to evenly coat the PDMS coating liquid onto the surface of the base film, and place it in an oven to dry at 60°C for 5 minutes, and then heat it to 80°C to 150°C to cure and crosslink for 60 minutes. S4. Soak the PDMS composite membrane obtained by curing in step S3 in the extractant for 12h to 24h, and then dry it for later use.

2. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S1, the weight ratio of silicone oil, crosslinking agent and catalyst is (1-20):1:(0.01-0.5).

3. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S1, the catalyst is a platinum catalyst or an organotin catalyst.

4. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S1, the solvent is n-hexane, n-heptane, chloroform, dichloromethane, or toluene.

5. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S1, after adding silicone oil, crosslinking agent and catalyst to solvent, stir for 5 min to 60 min at -30℃ to 25℃, and then let stand for degassing for 30 min to 12 h at -30℃ to 5℃.

6. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S2, the base film is made of polyvinylidene fluoride film, polysulfone film, polyacrylonitrile film, polypropylene film, polyethylene film, polytetrafluoroethylene film, polyethersulfone film, sulfonated polyethersulfone film, polyimide film, or polyetherimide film.

7. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, Before step S2, the base film is first soaked in deionized water for at least 24 hours, and then placed in an oven at 60℃~100℃ to dry for 12 hours~24 hours.

8. The method for preparing a PDMS gas separation composite membrane with controllable pore penetration depth according to claim 1, characterized in that, In step S3, the scraper is a scraper with a scraper gap of 10μm to 300μm.

9. The method for preparing a PDMS gas separation composite membrane with controllable pore depth according to claim 1, characterized in that, In step S4, the composite membrane treated with the extractant is dried in an oven at 60℃~100℃ for 12h~24h.

10. A polydimethylsiloxane gas separation composite membrane with controllable pore permeation depth prepared by the preparation method according to any one of claims 1 to 4.

Images