Preparation method for improving hydrophobic performance of PTFE-based oleophobic film and application

Abstract

The invention relates to the field of oleophobic film preparation, and discloses a preparation method for improving the hydrophobic performance of a PTFE-based oleophobic film and application, the preparation method comprises the following steps: a, preparing a modification solvent, and then adding a fluorine-containing oleophobic agent to form an oleophobic modifier; b, immersing the PTFE base membrane into an oleophobic modifier, and carrying out padding treatment; c, the PTFE base membrane is taken out and dried, and the modified solvent is deposited on the surface of the PTFE base membrane; d, repeating the steps b and c; and e, carrying out curing treatment on the padded PTFE base film. According to the method, the oleophobic modifier is prepared by mixing the modified solvent and the fluorine-containing oleophobic agent, and then the PTFE porous membrane base material is repeatedly padded, dried and deposited, so that the oleophobic layer can be uniformly and stably attached to the surface of the membrane. Compared with the technical scheme of single-time coating or low-efficiency coating in the prior art, the problems of non-uniform deposition and low adhesive force of the oleophobic layer are avoided, and the comprehensiveness, uniformity and long-term stability of the oleophobic layer on the surface of the film are ensured.

Description

Technical Field

[0001] The present invention relates to the field of oleophobic film preparation, in particular to a preparation method and application of a PTFE-based oleophobic film for improving its hydrophobic performance. Background Art

[0002] PTFE (polytetrafluoroethylene)-based oleophobic membranes are specially treated with PTFE to enhance their hydrophobic and oleophobic properties. PTFE is a polymer material with excellent chemical stability, high-temperature resistance, and corrosion resistance, making it commonly used in a variety of demanding environments. PTFE-based oleophobic membranes are widely used in fields such as protection, filtration, isolation, and surface protection. They are particularly effective in high-temperature, high-humidity, and highly corrosive environments, effectively resisting the adhesion of contaminants such as oil and grease. Common applications include protective films for electronic components, food packaging films, medical protective films, and surface protection for high-end machinery.

[0003] At present, the mainstream technology for preparing PTFE-based oleophobic membranes mainly relies on polymerization process or post-crosslinking process. Although these methods can effectively improve the hydrophobic and oleophobic properties of the membrane, they also have certain limitations. First, the polymerization process and post-crosslinking process usually require more complex equipment and a long processing time, resulting in high production costs and difficulty in large-scale industrial applications. In addition, these methods also have certain problems in terms of the uniformity and stability of the membrane, especially in the coating adhesion and durability on the membrane surface, and are prone to coating peeling or degradation. Secondly, the existing technology requires a higher technical level and strict process control during operation, which increases the difficulty of operation and limits its application in low-cost, high-efficiency production. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a preparation method and application for improving the hydrophobic properties of PTFE-based oleophobic membranes, which solves the problems of high preparation cost, great operation difficulty and poor stability and durability of the membranes in the existing technology.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solutions: A preparation method for improving the hydrophobicity of a PTFE-based oleophobic membrane comprises the following steps: a. preparing a modified solvent, and then adding a fluorinated oleophobic agent to form an oleophobic modifier; b. The PTFE base membrane is immersed in an oleophobic modifier and subjected to padding treatment; The PTFE-based membrane surface is inherently hydrophobic and has a low surface energy. In this step, the polarity and wettability of the modifying solvent enhance the membrane's surface affinity, promoting uniform distribution and penetration of the fluorinated oleophobic agent. Padding not only increases the oleophobic agent's surface area but also promotes uniform distribution of the solution through mechanical friction, further enhancing the membrane's oleophobic properties.

[0006] c. Remove the PTFE base membrane and dry it, and solidify the modified solvent on the surface of the PTFE base membrane; This drying step volatilizes components in the solvent (such as n-hexane and ethanol), allowing the fluorinated oleophobic agent in the modified solvent to gradually aggregate and solidify on the membrane surface. Proper control of drying temperature and time ensures complete solvent evaporation and a uniform and secure adhesion of the oleophobic layer to the membrane surface without compromising the membrane's air permeability. This process increases the thickness and strength of the membrane surface layer, improving its durability and stability.

[0007] d. Repeat steps b and c; Repeated padding and drying continuously increases the oleophobic coating layer on the membrane surface, further enhancing the membrane's oleophobic properties. With each padding cycle, the coating layer becomes thicker and more uniform, making the oleophobic effect on the membrane surface more durable and stable. By controlling the number of coating cycles and layers, the thickness of the oleophobic layer on the membrane surface can be adjusted to achieve optimal oleophobic performance.

[0008] e. Curing the PTFE base film after padding.

[0009] The curing process involves heating and further cross-linking, causing the cross-linking agent in the modified solvent to react with the oleophobic agent, forming a more stable cross-linked network structure. This cross-linking strengthens the bond between the oleophobic layer and the PTFE membrane, enhancing the durability and adhesion of the oleophobic layer on the membrane surface. This process promotes the cross-linking reaction through the input of thermal energy, thereby improving the overall performance of the membrane.

[0010] Preferably, the modified solvent comprises the following components by mass fraction: n-Hexane: 55-65 parts; Cyclohexene ether: 20-30 parts; Ethanol: 5-10 parts; Olefin cross-linking agent: 2-5 parts; Ester cross-linking agent: 5 to 8 parts.

[0011] Among them, n-hexane acts as a solvent to help dissolve the oleophobic agent and provide sufficient volatility; cyclohexene ether provides polarity, which helps to disperse and evenly deposit the oleophobic agent; the addition of ethanol adjusts the volatility and polarity of the solvent, ensuring uniform coating on the membrane surface; the cross-linking agent reacts with the oleophobic agent to enhance the adhesion and durability of the oleophobic layer on the membrane surface.

[0012] Preferably, the olefin cross-linking agent includes one of a trifluorochloroolefin cross-linking agent and a hexafluoropropylene cross-linking agent, and the ratio of the modified solvent to the fluorinated oleophobic agent is 10:1 to 5:1.

[0013] Preferably, the ester cross-linking agent includes one of an isocyanate cross-linking agent and a hexyl isocyanate cross-linking agent.

[0014] During the coating process, olefin and ester crosslinkers chemically react with the oleophobic agent to form a crosslinked network. This strengthens the interaction between the oleophobic agent molecules, preventing the oleophobic layer from shedding and peeling, significantly improving the film's durability, aging resistance, and stability. The crosslinking reaction also improves the film's mechanical properties, ensuring it maintains excellent oleophobic properties despite external stress or environmental changes.

[0015] Preferably, the preparation of the modified solvent comprises the following steps: S1. Select n-hexane and cyclohexene ether and load the reactor for stirring; S2. Add ethanol to the reactor and continue stirring; S3. Add an olefin crosslinker and an ester crosslinker and continue stirring; S4. Let stand; S5. Filter the solution to remove impurities and obtain a modified solvent.

[0016] As a non-polar solvent, n-hexane effectively dissolves the oleophobic agent and creates suitable wettability on the membrane surface. Cyclohexene ether, with its polarity, further disperses the oleophobic agent molecules and enhances coating uniformity on the membrane surface. Ethanol, by adjusting the polarity and volatility of the solvent system, ensures uniform coating on the membrane surface and enhances the dispersion of the oleophobic agent in the solution.

[0017] Preferably, in step S1, the stirring speed of the reactor is 300-500 rpm, and the stirring time is 45-60 min; In step S2, after adding ethanol, the stirring speed of the reactor is 400-600 rpm and the stirring time is 20-40 minutes.

[0018] Preferably, in step S3, after adding the olefin cross-linking agent and the ester cross-linking agent, the stirring speed of the reactor is 350 to 550 rpm, and the stirring time is 15 to 30 minutes; In step S4, the standing temperature is 25-30° C. and the standing time is 2-4 hours; In the solution filtration step S5, the pore size of the filter is 0.5 to 5 μm.

[0019] Preferably, in step d, steps b and c are repeated 1 to 5 times, and the thickness of the modified solvent finally solidified on the surface of the PTFE base film is 5 to 20 μm.

[0020] Preferably, in step e, when the PTFE base film after padding is cured: Use hot air drying equipment, the temperature is 60-80℃, and the curing time is 1-1.5h.

[0021] The invention discloses an application of a preparation method for improving the hydrophobicity of a PTFE-based oleophobic membrane, characterized in that the preparation method is applied to prepare a PTFE-based oleophobic membrane.

[0022] The present invention provides a preparation method and application for improving the hydrophobicity of a PTFE-based oleophobic membrane. The invention has the following beneficial effects: 1. The present invention prepares an oleophobic modifier by mixing a modified solvent with a fluorinated oleophobic agent, and then repeatedly padding and drying the PTFE porous membrane substrate to deposit the oleophobic layer uniformly and stably on the membrane surface. Compared with the existing single-coating or inefficient coating solutions, the present invention avoids the problems of uneven deposition and weak adhesion of the oleophobic layer, ensuring the comprehensiveness, uniformity, and long-term stability of the oleophobic layer on the membrane surface.

[0023] 2. The present invention enhances the crosslinking structure of the oleophobic layer on the membrane surface by using olefin and ester crosslinkers in combination with an oleophobic modifier. This crosslinking reaction effectively improves the water resistance, heat resistance, and wear resistance of the oleophobic layer. Compared with traditional polymerization or post-crosslinking processes, the present invention avoids the problem of shedding or aging of the oleophobic layer on the membrane surface, significantly extending the service life of the oleophobic membrane and enhancing the long-term stability and performance reliability of the membrane.

[0024] 3. The present invention forms an oleophobic modifier by mixing a modified solvent with a fluorinated oleophobic agent, and then forms an improved PTFE-based oleophobic film by multiple impregnation and rolling, thereby reducing complex process steps and dependence on expensive equipment, and optimizing the film coating process. Compared with the processes in the prior art that require complex cross-linking or long-term reaction, the present invention significantly improves production efficiency and reduces production costs. In addition, the processing process is simple and fast, which can greatly improve production benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the preparation method of the present invention; DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the specification of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] In order to better understand the present invention, the above contents are described in detail below in conjunction with specific embodiments.

[0028] Please see the attached Figure 1 ; Example

[0029] step: Preparation of modified solvent: Take 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol and mix them evenly; Add 3 parts of trifluorochloroolefin crosslinking agent and 4 parts of hexyl hexaisocyanate crosslinking agent to the above solution, stir at 500 rpm for 30 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (8:1), and stir them evenly to form an oleophobic modifier.

[0030] Padding treatment: Immerse the PTFE membrane in the oleophobic modifier and perform padding treatment to ensure uniform coating on the membrane surface; Drying treatment: The coated membrane was dried at 60 °C for 45 min to ensure that the modified solvent was completely deposited on the membrane surface; Repeat coating and drying: Repeat steps 3 and 4 for a total of 2 coating and drying processes; Curing treatment: Use hot air drying equipment, temperature 70℃, curing time is 1 hour.

[0031] Example 2 step: Preparation of modified solvent: Take 63 parts of n-hexane, 22 parts of cyclohexene ether, and 7 parts of ethanol and mix them evenly; 4 parts of hexafluoropropylene crosslinking agent and 5 parts of isocyanate crosslinking agent were added to the solution and stirred at 450 rpm for 35 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (7:1), and stir them evenly to form an oleophobic modifier.

[0032] Padding treatment: The PTFE membrane is immersed in the oleophobic modifier and coated by a padding method, and the membrane is removed after coating; Drying treatment: The membrane was taken out and dried at 60°C for 50 minutes; Repeat coating and drying: Repeat steps 3 and 4 for a total of 3 coating and drying processes; Curing treatment: Use hot air drying equipment, temperature 75 ℃, curing time is 1.5 hours.

[0033] Example 3 step: Preparation of modified solvent: Take 55 parts of n-hexane, 28 parts of cyclohexene ether, and 6 parts of ethanol and mix them evenly; Add 3 parts of trifluorochloroolefin crosslinking agent and 4 parts of hexyl hexaisocyanate crosslinking agent, and stir at 450 rpm for 40 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (10:1), and stir them evenly to form an oleophobic modifier.

[0034] Padding treatment: The PTFE membrane is immersed in the oleophobic modifier and coated by a padding method, and the membrane is removed after coating; Drying treatment: Drying temperature: 50°C, time: 30 minutes; Curing treatment: The curing temperature is 65°C and the curing time is 1 hour.

[0035] Example 4 step: Preparation of modified solvent: Take 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol and mix them evenly; Add 4 parts of trifluorochloroolefin crosslinking agent and 5 parts of hexyl hexaisocyanate crosslinking agent, and continue stirring at 500 rpm for 40 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (6:1), and stir them evenly to form an oleophobic modifier.

[0036] Padding treatment: Immerse the PTFE membrane in the oleophobic modifier and apply the coating using the padding method to ensure uniform coating on the membrane surface; Drying treatment: Drying temperature 65°C, time 60 minutes; Repeat coating and drying: Repeat steps 3 and 4 for a total of 3 coating and drying processes; Curing treatment: Use hot air drying equipment, curing temperature 70 ℃, curing time is 1 hour.

[0037] Comparative Example 1 step: Preparation of modified solvent: Take 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol and mix them evenly; 6 parts of trifluorochloroolefin crosslinking agent were added to the solution and stirred at 500 rpm for 30 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (8:1), and stir them evenly to form an oleophobic modifier.

[0038] Padding treatment: Immerse the PTFE membrane in the oleophobic modifier and perform padding treatment to ensure uniform coating on the membrane surface; Drying treatment: The coated membrane was dried at 60 °C for 45 min to ensure that the modified solvent was completely deposited on the membrane surface; Repeat coating and drying: Repeat steps 3 and 4 for a total of 2 coating and drying processes; Curing treatment: Use hot air drying equipment, temperature 70℃, curing time is 1 hour.

[0039] Comparative Example 2 step: Preparation of modified solvent: Take 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol and mix them evenly; Add 6 parts of trifluorochloroolefin crosslinking agent and stir at 500 rpm for 30 minutes to form a modified solvent; Adding conventional oleophobic agent: Add a conventional non-fluorinated oleophobic agent (such as paraffin oil or synthetic oleophobic agent) to the above solvent, mix in a ratio of (5:1), and stir evenly to form an oleophobic modifier; Padding treatment: The PTFE membrane is immersed in an oleophobic modifier and subjected to a padding treatment; Drying treatment: The coated film was dried at 60 °C for 45 min; Repeat coating and drying: Repeat steps 3 and 4 for a total of 2 coating and drying processes; Curing treatment: Use hot air drying equipment, temperature 70℃, curing time is 1 hour.

[0040] Comparative Example 3 step: Prepare solvent: Take 60 parts of n-hexane and 25 parts of cyclohexene ether and mix them evenly; No ethanol and cross-linking agent are used, and solvent mixing is performed directly; Adding fluorinated oleophobic agent: Adding a fluorinated oleophobic agent to the above solvent, mixing in a ratio of (10:1), and stirring evenly to form an oleophobic modifier; Padding treatment: The PTFE membrane is immersed in an oleophobic modifier and subjected to a padding treatment; Drying treatment: The coated film was dried at 60 °C for 45 min; Repeat coating and drying: Repeat steps 3 and 4 for a total of 2 coating and drying processes; Curing treatment: Use hot air drying equipment, temperature 70℃, curing time is 1 hour.

[0041] Comparative Example 4: step Preparation of modified solvent: Take 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol and mix them evenly; 6 parts of trifluorochloroolefin crosslinking agent were added to the solution and stirred at 500 rpm for 30 minutes to form a modified solvent; Adding fluorinated oleophobic agent: Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (8:1), and stir them evenly to form an oleophobic modifier.

[0042] Single coating process: Immersing the PTFE membrane in the oleophobic modifier, performing a dip coating, and removing the membrane after coating; Drying treatment: The coated film was dried at 60 °C for 45 min; Curing treatment: Use hot air drying equipment, temperature 70℃, curing time is 1 hour.

[0043] Experiment 1: Effect of double cross-linker on the stability of oleophobic layer Purpose of the experiment The difference between the dual cross-linker system (Example 1) and the single cross-linker system (Comparative Example 1) in improving the stability of the membrane oleophobic layer was verified, focusing on the changes in the oleophobicity of the membrane surface and its resistance to high temperature and humidity environments.

[0044] Experimental procedures Membrane preparation Films were prepared according to the methods of Example 1 (double cross-linking agent) and Comparative Example 1 (single cross-linking agent).

[0045] Example 1: 60 parts n-hexane, 25 parts cyclohexene ether, and 8 parts ethanol were used as a modifying solvent. 3 parts chlorotrifluoroolefin crosslinker and 4 parts hexyl hexaisocyanate crosslinker were added and stirred for 30 minutes to form a modified solvent. A fluorinated oleophobic agent was then added and mixed in a ratio of 8:1 to form an oleophobic modifier. Double coating, drying, and curing were performed.

[0046] Comparative Example 1: 60 parts n-hexane, 25 parts cyclohexene ether, and 8 parts ethanol were added with 6 parts of a chlorotrifluoroolefin crosslinker and stirred for 30 minutes to form a modified solvent. A fluorinated oleophobic agent was then added in a ratio of 8:1 to form an oleophobic modifier. The same coating, drying, and curing steps were followed.

[0047] Initial contact angle testing The initial water drop contact angle value of each film was measured using a water drop contact angle meter to record the initial oleophobic properties of the film.

[0048] Environmental stability test The membrane samples were placed in an environment of 60°C and 90% relative humidity for 24 hours.

[0049] Take out the sample and cool it to room temperature, measure its water drop contact angle value, and observe the change in contact angle.

[0050] Data Analysis The stability of the oleophobic layer was evaluated by comparing the initial contact angle and the change in contact angle after exposure to high temperature and humidity.

[0051] Experimental data Table 1: Comparative data on the stability of oleophobic layers with double crosslinkers and single crosslinkers

[0052] Experimental Summary The experimental data clearly demonstrates the superiority of the dual-crosslinker system. The contact angle of the sample in Example 1 remained within a range of 2.8° to 4.3° under a high-temperature, humid environment, while the contact angle of the sample in Comparative Example 1 varied significantly more, reaching 10.1° to 12.5°. This demonstrates that the dual-crosslinker system is more capable of maintaining the stability of the oleophobic layer on the membrane surface, while the single-crosslinker system is more fragile in extreme environments, making the oleophobic layer more susceptible to degradation or structural changes.

[0053] The explanation for this phenomenon can be found in the mechanism of the cross-linking structure. In the dual-crosslinker system, the synergistic action of trifluorochloroolefin crosslinkers and hexyl hexaisocyanate crosslinkers forms a denser three-dimensional cross-linked network, significantly improving the cross-linking density and chemical stability of the membrane surface. Especially in high-temperature and humid environments, this multi-cross-linked structure effectively prevents molecular chain breakage, inhibiting the peeling and reconstruction of the oleophobic layer, thereby maintaining a high contact angle and excellent oleophobic properties.

[0054] In Comparative Example 1, due to the use of only trifluorochloroolefin crosslinkers, the crosslinked network has a low complexity and density, making the surface more susceptible to damage in high humidity and high temperature environments, resulting in a rapid decrease in contact angle. The data shows that the contact angle of the samples in Comparative Examples 1-2 decreased from 121.8° to 109.3°, a significant decrease of 12.5°. This is significantly higher than the maximum change of 4.3° in the dual-crosslinker system, demonstrating the clear advantage of an optimized crosslinker system.

[0055] In summary, the present invention successfully overcomes the shortcomings of existing single-crosslinker systems, which are prone to failure in extreme environments, by introducing a dual crosslinker. This not only gives the oleophobic film greater environmental adaptability but also lays a solid foundation for future applications in multiple scenarios. For example, the potential value of this technology in applications such as electronic device protection, outdoor waterproof coatings, and functional materials for high-humidity environments cannot be ignored. Experimental results fully demonstrate the innovativeness and practical application of this invention.

[0056] Experiment 2: Comparison of coating adhesion (multiple coatings and single coating) Purpose of the experiment The differences in adhesion of the oleophobic layer on the membrane surface between multiple coatings (Example 2) and single coating (Comparative Example 2) were compared to verify how the multiple coating process significantly improves the adhesion and durability of the coating.

[0057] Experimental procedures Membrane preparation Film samples were prepared according to the methods of Example 2 and Comparative Example 2, respectively.

[0058] Example 2: 63 parts n-hexane, 22 parts cyclohexene ether, and 7 parts ethanol were added with 4 parts hexafluoropropylene crosslinker and 5 parts isocyanate crosslinker. The mixture was stirred at 450 rpm for 35 minutes to form a modified solvent. A fluorinated oleophobic agent was added to the modified solvent in a ratio of 7:1. The mixture was then coated, dried, and cured three times.

[0059] Comparative Example 2: 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol were added with 6 parts of a chlorotrifluoroolefin crosslinker and stirred for 30 minutes to form a modified solvent. A fluorinated oleophobic agent was added to the modified solvent in a ratio of 8:1. A single coating was performed. The subsequent drying and curing procedures were consistent with those in the previous example.

[0060] Adhesion test The adhesion of the film sample was tested using a tensile peel tester to test the maximum peeling force of the film surface coating in N / cm 2 .

[0061] Test method: Select 6 points on each film surface for testing, record the peel force value at each point, calculate the average peel force, and evaluate the adhesion strength of the coating.

[0062] Data recording and analysis The adhesion data of the two groups of samples were compared to analyze the effects of multiple coating and single coating processes on coating adhesion.

[0063] Experimental data Table 2: Comparison of adhesion between multiple coatings and single coating

[0064] Experimental Summary The experimental data fully demonstrates the significant effect of multiple coating processes in improving the adhesion of the film surface. The average peel force of the sample in Example 2 is maintained at 8.27N / cm 2 Up to 8.45N / cm 2 , while the peeling force of the sample in comparative example 2 is only 5.82N / cm 2 Up to 5.92N / cm 2 The difference is significant. Multiple coats create a more uniform and dense structure on the film surface, thereby enhancing the adhesion between the coating and the substrate. In contrast, single-coated film samples are more likely to experience localized damage during peel testing, demonstrating a clear lack of adhesion.

[0065] The advantage of the multi-coating process lies not only in the increased coating thickness but also in the fact that after each drying and curing step, the oleophobic layer further crosslinks and fills the microscopic pores, forming a continuous, stable coating structure. This cumulative effect significantly enhances the oleophobic layer's cohesion and surface adhesion, preventing the coating from cracking and separating under high shear forces. This, combined with the strengthening effect of the multi-crosslinked network, significantly improves the membrane's overall performance.

[0066] The reason why the single-coating sample showed a lower peeling force was mainly due to the uneven distribution of the coating on the film surface. The local weak area became a stress concentration point, resulting in a rapid decrease in peeling force. In addition, the single-coating process was difficult to completely cover the tiny pores and defects on the film surface, further weakening the stability of the coating. It can be seen that although the peeling force value of the comparative example 2 sample was 6N / cm 2 However, in actual use, this difference will significantly affect the long-term durability and stability of the membrane.

[0067] In summary, the multi-coating process of the present invention clearly offers advantages. It not only significantly improves the adhesion of the coating but also provides greater reliability for the industrial application of oleophobic films. Such process improvements will greatly expand the application range of oleophobic films, especially in scenarios requiring high durability and protective properties, such as electronic device packaging and outdoor equipment coatings. Multi-coating technology will undoubtedly bring long-term value.

[0068] Experiment 3: Water resistance and heat resistance test Purpose of the experiment The differences in water resistance and heat resistance of the membranes using a cross-linking agent and a fluorinated oleophobic agent in combination (Example 3) and without a cross-linking agent (Comparative Example 3) were verified, with a focus on the stability of the oleophobic layer of the membrane in high humidity and high temperature environments.

[0069] Experimental procedures Membrane preparation Film samples were prepared according to the methods of Example 3 and Comparative Example 3, respectively.

[0070] Example 3: 55 parts of n-hexane, 28 parts of cyclohexene ether, and 6 parts of ethanol were added, 3 parts of trifluorochloroolefin crosslinking agent and 4 parts of hexyl hexaisocyanate crosslinking agent were added, and stirred at 450 rpm for 40 minutes.

[0071] Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (10:1), and stir them evenly to form an oleophobic modifier.

[0072] Carry out coating, drying and curing treatment.

[0073] Comparative Example 3: 60 parts of n-hexane, 25 parts of cyclohexene ether and 8 parts of ethanol were mixed uniformly.

[0074] Add the fluorinated oleophobic agent to the modified solvent, mix them in a ratio of (10:1), and stir them evenly to form an oleophobic modifier.

[0075] Carry out coating, drying and curing treatment.

[0076] Initial contact angle testing The initial contact angle of the membrane surface was measured using a water drop contact angle meter to evaluate the initial oleophobicity of the membrane.

[0077] Water resistance test The sample membrane was immersed in room temperature water for 72 hours. The sample was then removed, the water surface was wiped dry, and the contact angle was measured to evaluate the change in the membrane's oleophobic properties after immersion.

[0078] Heat resistance test The sample film was placed in an oven at 80°C for 72 hours. The sample was then removed and cooled to room temperature before the contact angle was measured to evaluate the effect of the high temperature environment on the oleophobic properties of the film.

[0079] Data recording and analysis The changes in contact angles of the two groups of samples before and after the water resistance and heat resistance tests were compared to evaluate the water resistance and heat resistance of the membranes.

[0080] Experimental data Table 3: Water resistance and heat resistance test data

[0081] Experimental Summary By comparing the experimental data of Example 3 with that of Comparative Example 3, it is obvious that the dual cross-linker system has advantages in improving the water resistance and heat resistance of the membrane. The contact angle in Example 3 changes less, with the contact angle varying from 2.3° to 2.8° after water immersion, and from 3.6° to 3.7° after heat treatment. In contrast, the contact angle of the membrane surface in Comparative Example 3 changes more, with the contact angle varying from 5.7° to 6.4° after water immersion, and from 8.2° to 9.2° after heat treatment. This difference indicates that the dual cross-linker system significantly enhances the stability of the membrane, especially in extreme environments, and can effectively maintain the oleophobicity of the membrane surface.

[0082] From a mechanistic perspective, the dual-crosslinker system, through the synergistic action of trifluorochloroolefin crosslinkers and hexyl hexaisocyanate crosslinkers, forms a more complex and tightly linked structure. This crosslinked network not only enhances the membrane's surface adhesion but also improves its water and heat resistance. When the membrane is exposed to water or high temperatures, the crosslinked structure effectively inhibits molecular chain breakage, preventing the coating from swelling or shedding, thereby ensuring the stability of the oleophobic layer.

[0083] In contrast, the membrane in Comparative Example 3, which did not use a crosslinker, had a looser surface structure, with looser connections between the molecular chains, which were susceptible to changes in high temperature and high humidity. This resulted in a significant decrease in the membrane contact angle, demonstrating the key role of the crosslinker in improving membrane stability. The experimental results further demonstrated that the dual-crosslinker system not only improved the membrane's oleophobicity but also enhanced its long-term stability in harsh environments, offering significant application advantages.

[0084] These experimental data and mechanism analysis clearly demonstrate the innovation and technical advantages of the present invention, especially in application fields requiring higher durability and stability, such as outdoor protection and electronic component protection, the present invention provides a more reliable solution.

[0085] Experiment 4: Production efficiency and cost comparison Purpose of the experiment The advantages of the multiple coating and dual cross-linking agent system of the present invention (Example 4) and the traditional single coating process (Comparative Example 4) in terms of production efficiency and cost are compared, especially the difference in time and cost during the film preparation process.

[0086] Experimental procedures Membrane preparation Film samples were prepared according to the methods of Example 4 and Comparative Example 4, respectively.

[0087] Example 4: 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol were added, 4 parts of trifluorochloroolefin crosslinking agent and 5 parts of hexyl hexaisocyanate crosslinking agent were added, and finally a fluorinated oleophobic agent was added, mixed in a ratio of (6:1), and stirred evenly.

[0088] Three coating, drying and curing processes are used.

[0089] Comparative Example 4: 60 parts of n-hexane, 25 parts of cyclohexene ether, and 8 parts of ethanol were added, 6 parts of trifluorochloroolefin crosslinking agent were added, and finally a fluorinated oleophobic agent was added, mixed in a ratio of (8:1), and stirred evenly.

[0090] Use only a single coat, dry and cure process.

[0091] Production time measurement Measure the time required to produce each batch of membranes, including: Coating time Drying time Curing time Cost Calculation Calculate the production cost of each batch of membrane, including: Raw material costs (including solvents, cross-linking agents, and fluorinated oleophobic agents) Energy consumption (electricity consumption required for drying and curing) Labor costs (operation time and number of people) Data Analysis The production efficiency and cost of Example 4 were compared with those of Comparative Example 4, and the differences in time and cost between multiple coatings and single coatings were analyzed.

[0092] Experimental data Table 4: Comparison of production efficiency and cost

[0093] Based on experimental data, Example 4 (multiple coatings and dual crosslinkers) is indeed more time-consuming and costly to produce than Comparative Example 4 (single coating). The total production time for Example 4 is 124-135 minutes, while the total production time for Comparative Example 4 is only 102-110 minutes. This is because the multiple coating process involves repeated coating, drying, and curing. Despite this, Example 4 incurs slightly higher raw material and labor costs than Comparative Example 4, resulting in a total cost difference of 3.5-4.5 yuan.

[0094] This is partly due to the increased chemical reaction time required for the dual cross-linking agent, while the additional number of coating layers also requires additional drying and curing processes. However, it's worth noting that this additional investment in time and cost significantly improves film surface adhesion, stability, and other properties. Experimental data shows that the film of Example 4 is significantly more stable in high-temperature, high-humidity environments than that of Comparative Example 4. This difference lays a solid foundation for the durability and reliability of future products.

[0095] From a mechanistic perspective, the multiple coating processes and the dual cross-linking agent create a more stable cross-linked network. The curing of each coating layer not only increases the film's thickness but also strengthens the interactions between molecules on the film's surface, significantly enhancing the film's adhesion, impact resistance, and durability. This dual optimization of the modified solvent and coating process results in a denser overall film structure, preventing the coating from shedding or damaging over time.

[0096] While Example 4 requires a higher production time and cost, considering its long-term performance, especially in demanding applications (such as outdoor coatings, protective films, and electronic component packaging), this combination of multiple coatings and a dual crosslinker is undoubtedly a more competitive technology. In these demanding applications, the stability and performance advantages of Example 4 far outweigh the additional production investment.

[0097] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method for improving the hydrophobicity of a PTFE-based oleophobic membrane, characterized in that: The following steps are involved: a. preparing a modified solvent, and then adding a fluorinated oleophobic agent to form an oleophobic modifier; b. The PTFE base membrane is immersed in an oleophobic modifier and subjected to padding treatment; c. Remove the PTFE base membrane and dry it, and deposit the modified solvent on the surface of the PTFE base membrane; d. Repeat steps b and c; e. Curing the PTFE base film after padding.

2. a kind of preparation method improving the hydrophobicity of PTFE-based oleophobic membrane according to claim 1, is characterized in that, The modified solvent comprises the following components by mass fraction: n-Hexane: 55-65 parts; Cyclohexene ether: 20-30 parts; Ethanol: 5-10 parts; Olefin cross-linking agent: 2-5 parts; Ester cross-linking agent: 5 to 8 parts.

3. a kind of preparation method improving the hydrophobicity of PTFE-based oleophobic membrane according to claim 2, is characterized in that, The olefin crosslinking agent includes one of a trifluorochloroolefin crosslinking agent and a hexafluoropropylene crosslinking agent, and the ratio of the modified solvent to the fluorinated oleophobic agent is 10:1 to 5:

1.

4. a kind of preparation method improving the hydrophobicity of PTFE-based oleophobic membrane according to claim 2, is characterized in that, The ester cross-linking agent includes one of an isocyanate cross-linking agent and a hexyl hexyl isocyanate cross-linking agent.

5. a kind of preparation method improving the hydrophobicity of PTFE-based oleophobic membrane according to claim 2, is characterized in that, The preparation of the modified solvent comprises the following steps: S1. Select n-hexane and cyclohexene ether and load the reactor for stirring; S2. Add ethanol to the reactor and continue stirring; S3. Add an olefin crosslinker and an ester crosslinker and continue stirring; S4. Let stand; S5. Filter the solution to remove impurities and obtain a modified solvent.

6. A method for preparing a PTFE-based oleophobic membrane having hydrophobic properties according to claim 5, wherein: In step S1, the stirring speed of the reactor is 300-500 rpm, and the stirring time is 45-60 min; In step S2, after adding ethanol, the stirring speed of the reactor is 400-600 rpm and the stirring time is 20-40 minutes.

7. A method for preparing a PTFE-based oleophobic membrane having hydrophobic properties according to claim 5, wherein: In step S3, after adding the olefin cross-linking agent and the ester cross-linking agent, the stirring speed of the reactor is 350-550 rpm, and the stirring time is 15-30 minutes; In step S4, the standing temperature is 25-30° C. and the standing time is 2-4 hours; In the solution filtration step S5, the pore size of the filter is 0.5 to 5 μm.

8. A method for preparing a PTFE-based oleophobic membrane having hydrophobic properties according to claim 1, wherein In the step d, steps b and c are repeated 1 to 5 times, and the thickness of the modified solvent deposited on the surface of the PTFE base film is finally 5 to 20 μm.

9. a kind of preparation method improving the hydrophobicity of PTFE-based oleophobic membrane according to claim 1, is characterized in that, In the step e, when the PTFE base film after padding is cured: Use hot air drying equipment, the temperature is 60-80℃, and the curing time is 1-1.5h.

10. Application of a preparation method for improving the hydrophobicity of a PTFE-based oleophobic membrane, based on the preparation method for improving the hydrophobicity of a PTFE-based oleophobic membrane according to claim 1, characterized in that: The preparation method is applied to preparing a PTFE-based oleophobic membrane.

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