A pore-controllable polytetrafluoroethylene microporous membrane, a preparation method thereof and application thereof in marine antifouling

Abstract

The application discloses a kind of polytetrafluoroethylene microporous membrane with controllable porosity and its preparation method and application in marine antifouling, belong to polytetrafluoroethylene film processing and manufacturing technical field, the polytetrafluoroethylene film is prepared by blending nano heat swellable microspheres in polytetrafluoroethylene granules in the application, then melt modification is added on the film Anti-fouling particles, remove auxiliary oil by heating, in this process, microspheres are expanded and broken by heating, and form polytetrafluoroethylene microporous membrane with uniform pore size;The application utilizes surface enrichment strategy, forms antifouling layer in the outermost layer of polytetrafluoroethylene film, so that filler is not directly blended with polytetrafluoroethylene matrix, overcome the problem that filler is agglomerated in polymer matrix, unevenly dispersed, avoid the weakening of mechanical properties of polytetrafluoroethylene microporous membrane caused by the addition of filler;High-temperature physical foaming method is used in the preparation process of the application, simple operation and green, can be widely applied in medical and health materials, water treatment and air purification and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polytetrafluoroethylene membrane processing and manufacturing technology, specifically relating to a polytetrafluoroethylene microporous membrane with controllable pores, its preparation method, and its application in marine antifouling. Background Technology

[0002] Polytetrafluoroethylene (PTFE) microporous membranes are thin films with micropores and excellent filtration performance, formed by mixing and curing PTFE resin particles with additives such as oil, followed by expansion, stretching, and heat setting at temperatures below their melting point. PTFE microporous membranes have a microporous structure with interwoven fibers, exhibiting advantages such as high porosity, low resistance, high particle rejection rate, good temperature resistance, resistance to strong acids and alkalis, resistance to organic solvents, antioxidants, and aging. Filter bags, cartridges, and filters made by coating PTFE microporous membranes onto support materials such as polyester felt, PET, and PTFE fiber felt have shown good results in flue gas and dust treatment and recovery in the cement, metallurgy, petrochemical, and plastics industries. Filter sheets and filters made by coating PTFE microporous membranes onto support materials such as PET and PP nonwoven fabrics also have good application results in the chemical, pharmaceutical, and electronics industries. However, research on the application of PTFE microporous membranes in marine antifouling is still scarce.

[0003] Currently, almost all commercially available polytetrafluoroethylene (PTFE) microporous membranes are produced using the extrusion molding-stretching method. The core process of each method involves mixing PTFE dispersion resin with additives, followed by extrusion molding, additive removal, stretching, and shaping to obtain the PTFE microporous membrane. The membrane micropore morphology is a dotted-line structure composed of "microfibers" and "nodes." However, due to process limitations, the membranes prepared by these methods have a wide micropore size distribution and poor uniformity. Reducing the pore size leads to a simultaneous decrease in membrane porosity, and the membrane feels soft and thin, resulting in low mechanical strength and hindering subsequent processing. Furthermore, because the "microfibers" constituting the membrane micropore structure are too fine and weak, they are prone to deformation or breakage during use, causing an increase in micropore size and a decrease in separation performance.

[0004] The invention patent with publication number CN114272764A discloses "a polytetrafluoroethylene microporous membrane and its preparation method and application". The method involves blending nano-silica with polytetrafluoroethylene to form a membrane, and then using hydrofluoric acid etching to remove the nano-silica microspheres inside the membrane to prepare a polytetrafluoroethylene microporous membrane. This method is simple to operate, but the use of hydrofluoric acid etching requires high operational skills and is difficult to industrialize.

[0005] The invention patent with publication number CN105014982A discloses a "method for preparing graphene-polytetrafluoroethylene permeation distillation membrane". The method involves mixing nano-graphene or graphene oxide with polytetrafluoroethylene to prepare a permeation distillation membrane. However, this method has difficulties in achieving uniformity of graphene dispersion. The added graphene disrupts the connections between polytetrafluoroethylene molecular chains, reducing the original performance of the microporous membrane.

[0006] Therefore, researching a polytetrafluoroethylene microporous membrane with controllable pore size, simple preparation method, and the ability to be used in marine antifouling without compromising mechanical properties, as well as its preparation method, has great practical significance and broad application prospects. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention utilizes a surface enrichment strategy to form an antifouling layer on the outermost layer of a polytetrafluoroethylene (PTFE) film, thereby constructing a PTFE microporous membrane with controllable pores that can be used for marine antifouling.

[0008] The technical solution of the present invention is as follows:

[0009] One objective of this invention is to provide a method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size, comprising the following steps:

[0010] (1) The antifouling filler nanoparticles and dispersant were ultrasonically dispersed in an alkane additive and mixed evenly to obtain an antifouling liquid;

[0011] (2) Mix the nano-thermally expandable microspheres and polytetrafluoroethylene powder evenly to obtain a mixture, and then add additives to the mixture and mix and mature to obtain a film-forming mixture;

[0012] (3) Place the film-forming mixture into a film press and press it into a film;

[0013] (4) Spray or brush the antifouling liquid prepared in step (1) onto the surface of the film;

[0014] (5) The film is subjected to high temperature treatment, so that the thermally expandable microspheres in the film expand when heated;

[0015] (6) Further increase the temperature and hot press the film to make the thermally expandable microspheres break into pores. At the same time, high temperature melt modification is carried out to embed anti-fouling nanoparticles on the surface of the polytetrafluoroethylene film to form an anti-fouling layer. After cooling treatment, anhydrous ethanol is used to clean and dry the film to obtain a polytetrafluoroethylene microporous membrane with uniform pores.

[0016] Furthermore, the antifouling filler used in step (1) is one or a combination of Al2O3, ZnO, carbon nanotubes, SiO2, TiO2, and Fe3O4 nanoparticles, with the diameter of the nanoparticles ranging from 25 to 300 nm.

[0017] Furthermore, the diameter of the nanoparticles is between 100-200 nm.

[0018] Furthermore, the alkane auxiliary in step (1) is an isoparaffin auxiliary.

[0019] Furthermore, in step (2), the nano-thermally expandable microspheres are thermoplastic hollow polymer microspheres, and the polytetrafluoroethylene powder has a relative molecular weight of 200-1000 million and a particle size of 300-400 μm.

[0020] Furthermore, the nano-thermally expandable microspheres are thermoplastic hollow polymer microspheres.

[0021] Furthermore, the thermally expandable nanospheres are polystyrene microspheres, acrylic resin microspheres, polypropylene microspheres, etc.

[0022] Furthermore, in step (2), the additive is an isoparaffinic additive oil, and the mixing ratio of polytetrafluoroethylene powder and additive is 100:18-30.

[0023] Furthermore, in step (3), the film press uses a pressure of 8-10 MPa, and the thickness of the pressed film is less than 1 mm.

[0024] Furthermore, in step (5), the high-temperature expansion temperature is 80-230℃, the heating rate is 10℃ / min, and after reaching the predetermined temperature, it is kept at the temperature for 5 minutes to allow the thermally expandable microspheres to fully expand.

[0025] Furthermore, the hot pressing process of the film in step (6) is as follows: continue to heat up to 350°C at a rate of 5°C / min. After the temperature reaches 350°C, keep it at that temperature for 15 minutes to cause the thermally expandable microspheres to rupture and form perforations. The antifouling particles are embedded in the surface of the polytetrafluoroethylene film. Then, cool down to 60°C at a rate of 10°C / min.

[0026] Furthermore, in step (6), anhydrous ethanol is used for ultrasonic cleaning for 15 minutes, followed by drying in an 80°C oven.

[0027] The second objective of this invention is to provide a polytetrafluoroethylene microporous membrane with controllable pore size, wherein the polytetrafluoroethylene microporous membrane has uniform pore size and an antifouling layer formed by antifouling particles on its surface.

[0028] Furthermore, the porosity of polytetrafluoroethylene microporous membranes is 40-90%.

[0029] The third objective of this invention is to provide an application of a polytetrafluoroethylene microporous membrane with controllable pore size in marine antifouling.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention innovates a method for preparing polytetrafluoroethylene (PTFE) microporous membranes. A PTFE film is prepared by co-blending nano-thermally expandable microspheres with PTFE granules. Then, using a surface enrichment strategy, antifouling particles are added to the PTFE film through melt modification, forming an antifouling layer on the outermost layer of the PTFE film. The filler is not directly blended with the PTFE body. Finally, the microspheres are heated and degreased, causing them to expand and rupture, thus forming a PTFE microporous membrane with uniform pore size.

[0032] 2. The novel polytetrafluoroethylene (PTFE) microporous membrane constructed in this invention uses nano-thermally expandable microspheres to fill the PTFE matrix. After molding, it is heated, degreased, expanded, and ruptured to form a microporous membrane with uniform size. This method can accurately control the size of the micropores, avoiding the problem of inconsistent pore sizes in existing PTFE microporous membranes that lead to unstable functions. In addition, this invention attaches antifouling particles to the surface of the film, so that the PTFE microporous membrane overcomes the disadvantages of mechanical stress concentration and uneven performance caused by the agglomeration and uneven dispersion of fillers in the polymer matrix, and avoids the weakening of the mechanical properties of the PTFE microporous membrane due to the addition of fillers.

[0033] 3. The polytetrafluoroethylene microporous membrane disclosed in this invention is prepared by high-temperature physical foaming, which is simple to operate and environmentally friendly. The resulting polytetrafluoroethylene microporous membrane has a high pore regularity and uniform and controllable pore size. Its contact angle is larger than that of polytetrafluoroethylene microporous membranes prepared by conventional biaxial stretching method, which can have a wider contact area with marine pollutants. Furthermore, the antifouling particles on the surface of the microporous membrane can effectively inhibit the adhesion of marine pollutants, giving it better antifouling effect and higher antifouling efficiency.

[0034] Figure Labels

[0035] Figure 1 This is a schematic diagram of the structure of the polytetrafluoroethylene microporous membrane with controllable pores described in this invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0037] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0038] In the quantitative experiments in the following examples, three replicate experiments were set up, and the average value of the results was taken.

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0040] In this embodiment of the invention, the polytetrafluoroethylene powder was purchased from Chemours Chemical Co., Ltd., and the nano-thermally expandable microspheres were purchased from Dongguan Mingyuan Plastics Co., Ltd.

[0041] Example 1

[0042] This embodiment provides a polytetrafluoroethylene microporous membrane with controllable pore size, and the preparation method includes the following steps:

[0043] S1. Add TiO2 nanoparticles with a particle size of 50nm and dispersant polyvinylpyrrolidone to isoparaffin G additive, wherein the mass ratio of dispersant to nanoparticles is 1:5. After mechanical dispersion, ultrasonic dispersion is performed for 30 minutes to prepare a 10mg / mL antifouling liquid.

[0044] S2. Use polystyrene microspheres with a particle size of 450nm and polytetrafluoroethylene with a relative molecular mass of 8 million and a particle size of 300μm to mix evenly at a mass ratio of 1:100. Then add isoparaffin G-type auxiliary oil to the mixture, with a mass ratio of auxiliary oil to mixture of 9:50. Mix the above raw materials evenly and let it stand at 50℃ for 72h.

[0045] S3. Weigh 0.3g of film-forming mixture, put it into the film-forming mold, and press the film-forming mixture into a film using a pressure of 8MPa;

[0046] S4. Spray the antifouling liquid prepared in S1 onto the film surface and press the film using a pressure plate.

[0047] S5. The film is heated in a high-temperature furnace under the following conditions: the temperature is increased from room temperature to 150°C at a rate of 10°C / min. After reaching the predetermined temperature, the temperature is maintained for 5 minutes to allow the microspheres to fully expand. The temperature is then increased to 350°C at a rate of 5°C / min. After reaching 350°C, the temperature is maintained for 15 minutes to allow the microspheres to rupture and form perforations. The antifouling particles are then embedded in the surface of the polytetrafluoroethylene film at high temperature. The film is then cooled to 60°C at a rate of 10°C / min and removed.

[0048] S6. Ultrasonically clean the membrane with anhydrous ethanol for 15 min, and dry it in an oven at 80℃ to obtain a polytetrafluoroethylene microporous membrane with a pore size of 4.5 μm, a porosity of 85%, and a thickness of 0.8 mm.

[0049] Example 2

[0050] This embodiment provides a method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size, comprising the following steps:

[0051] S1. Add Al2O3 nanoparticles with a particle size of 100nm and dispersant polyvinylpyrrolidone to ExxonMobil G, wherein the mass ratio of dispersant to nanoparticles is 1:5. After mechanical dispersion, ultrasonic dispersion is performed for 30 minutes to prepare a 10mg / mL antifouling solution.

[0052] S2. Use acrylic polymer microspheres with a particle size of 10μm and polytetrafluoroethylene with a relative molecular mass of 8 million and a particle size of 300μm to mix evenly at a mass ratio of 1:100. Then add isoparaffin G-type auxiliary oil and dispersant ammonium polyacrylate to the mixture. The mass ratio of auxiliary oil to mixture is 1:4 and the dispersant content is 10%. Mix the above raw materials evenly and let it stand at 70℃ for 36 hours.

[0053] S3. Weigh 0.3g of film-forming mixture, put it into the film-forming mold, and press the film-forming mixture into a film using a pressure of 10MPa;

[0054] S4. Spray the antifouling liquid prepared in S1 onto the film surface and press the film using a pressure plate.

[0055] S5. The film is heated in a high-temperature furnace under the following conditions: the temperature is increased from room temperature to 100°C at a rate of 10°C / min. After reaching the predetermined temperature, the temperature is maintained for 5 minutes to allow the microspheres to fully expand. The temperature is then increased to 350°C at a rate of 5°C / min. After reaching 350°C, the temperature is maintained for 15 minutes to allow the microspheres to rupture and form perforations. The antifouling particles are then embedded in the surface of the polytetrafluoroethylene film at high temperature. The temperature is then reduced to 60°C at a rate of 10°C / min, and the film is removed.

[0056] S6. Ultrasonically clean the membrane with anhydrous ethanol for 15 min, and dry it in an oven at 80℃ to obtain a polytetrafluoroethylene microporous membrane with a pore size of 100μm, a porosity of 80%, and a thickness of 0.8mm.

[0057] Example 3

[0058] This embodiment provides a method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size, comprising the following steps:

[0059] S1. Add TiO2 nanoparticles with a particle size of 50nm, MnO2 nanorods with a length of 30nm, and dispersant polyvinylpyrrolidone to ExxonMobil G, wherein the mass ratio of dispersant to nanoparticles is 1:5. After mechanical dispersion, ultrasonic dispersion is performed for 30 minutes to prepare an antifouling solution with a concentration of 10mg / mL.

[0060] S2. Use polypropylene microspheres with a particle size of 450nm and polytetrafluoroethylene with a relative molecular mass of 8 million and a particle size of 300μm to mix evenly at a mass ratio of 1:100. Then add isoparaffin G-type auxiliary oil to the mixture, with a mass ratio of auxiliary oil to mixture of 3:10. Mix the above raw materials evenly and let it stand at 50℃ for 72h.

[0061] S3. Weigh 0.3g of film-forming mixture, put it into the film-forming mold, and press the film-forming mixture into a film using a pressure of 10MPa;

[0062] S4. Spray the antifouling liquid prepared in S1 onto the film surface and press the film using a pressure plate.

[0063] S5. The film is heated in a high-temperature furnace under the following conditions: the temperature is increased from room temperature to 150°C at a rate of 10°C / min. After reaching the predetermined temperature, the temperature is maintained for 5 minutes to allow the microspheres to fully expand. The temperature is then increased to 350°C at a rate of 5°C / min. After reaching 350°C, the temperature is maintained for 15 minutes to allow the microspheres to rupture and form perforations. The antifouling particles are then embedded in the surface of the polytetrafluoroethylene film at high temperature. The film is then cooled to 60°C at a rate of 10°C / min and removed.

[0064] S6. Ultrasonically clean the membrane with anhydrous ethanol for 15 min, and dry it in an oven at 80℃ to obtain a polytetrafluoroethylene microporous membrane with a pore size of 3μm, a porosity of 86%, and a thickness of 0.8mm.

[0065] In the above embodiments, the antifouling filler can also be selected as one or a combination of ZnO, carbon nanotubes, SiO2, TiO2, and Fe3O4 nanoparticles, depending on the actual operation; any one of the isoparaffinic auxiliaries can be selected as the alkane auxiliary; the diameter of the antifouling nanoparticles can be adjusted to 25-300 nm; the relative molecular weight of the polytetrafluoroethylene powder can be adjusted to 2-10 million, the particle size to 300-400 μm; and the thermal expansion temperature to 80-230℃.

[0066] Performance testing

[0067] The contact angle of the polytetrafluoroethylene microporous membranes prepared in Examples 1-3 and the polytetrafluoroethylene microporous membranes prepared by conventional biaxial stretching method (control group 1) was tested. The membranes were placed in the same simulated marine environment for 30 days to observe the adhesion of pantrophic paracocci (Gram-negative bacteria) on the surface of the microporous membranes. The specific test results are shown in Table 1.

[0068] Table 1. Contact angle and antifouling test results of polytetrafluoroethylene microporous membrane

[0069] Example Contact angle anti-fouling effect Example 1 132° A small amount of yellow bacterial film Example 2 136° A small amount of yellow bacterial film Example 3 140° There is almost no yellow bacterial film. Control group 1 102° Covered with yellow bacterial film

[0070] As can be seen from the table above, the polytetrafluoroethylene microporous membrane prepared by this invention has a larger contact angle than the traditional polytetrafluoroethylene microporous membrane, and can perform better antifouling performance in marine environments.

[0071] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size, characterized in that, Includes the following steps: (1) The antifouling filler nanoparticles and dispersant are ultrasonically dispersed in alkane additives and mixed evenly to obtain an antifouling liquid; (2) Mix the nano-thermally expandable microspheres and polytetrafluoroethylene powder evenly to obtain a mixture, and then add additives to the mixture and mix and mature to obtain a film-forming mixture; (3) Place the film-forming mixture into a film press and press it into a polytetrafluoroethylene film; (4) Spray or brush the antifouling liquid prepared in step (1) onto the surface of the film; (5) The film is subjected to high temperature treatment, so that the thermally expandable microspheres in the polytetrafluoroethylene film expand when heated; (6) Further increase the temperature and hot press the film to make the thermally expandable microspheres break and form pores. At the same time, the polytetrafluoroethylene film is modified by high temperature melting. The antifouling nanoparticles are embedded in the film surface at high temperature to form an antifouling layer. After cooling treatment, anhydrous ethanol is used to clean and dry the film to obtain a polytetrafluoroethylene microporous membrane with uniform pores. The antifouling filler used in step (1) is one or a combination of Al2O3, ZnO, carbon nanotubes, SiO2, TiO2, and Fe3O4 nanoparticles, with a diameter of 25-300 nm; the alkane auxiliary in step (1) is an isoparaffin auxiliary. In step (2), the additive is an isoparaffinic additive oil, and the mixing ratio of polytetrafluoroethylene powder and additive is 100:18-30; in step (2), the nano-thermally expandable microspheres are thermoplastic hollow polymer microspheres, and the polytetrafluoroethylene powder has a relative molecular weight of 200-1000 million and a particle size of 300-400 μm. In step (3), the film press uses a pressure of 8-10 MPa, and the thickness of the pressed film is less than 1 mm.

2. The method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size as described in claim 1, characterized in that, In step (5), the high-temperature expansion temperature is 80-230℃, the heating rate is 10℃ / min, and after reaching the predetermined temperature, it is kept at the temperature for 5 minutes to allow the thermally expandable microspheres to fully expand.

3. The method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size as described in claim 1, characterized in that, The hot pressing process of the film in step (6) is as follows: continue to heat up to 350°C at a rate of 5°C / min. After the temperature reaches 350°C, keep it at that temperature for 15 minutes to cause the thermally expandable microspheres to rupture and form perforations. The antifouling particles are embedded in the surface of the polytetrafluoroethylene film. Then, cool down to 60°C at a rate of 10°C / min.

4. A polytetrafluoroethylene microporous membrane prepared by the method for preparing a polytetrafluoroethylene microporous membrane with controllable pore size according to any one of claims 1 to 3, characterized in that, The polytetrafluoroethylene microporous membrane has uniform pore size and an antifouling layer formed by attached antifouling particles on its surface.

5. The application of a polytetrafluoroethylene microporous membrane with controllable pore size prepared by the method according to any one of claims 1 to 3 in marine antifouling.

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