Preparation and fluorination method of porous polyurethane membrane and fluorinated porous polyurethane membrane

Abstract

The invention discloses a method for preparing and fluorinating a porous polyurethane membrane and a fluorinated porous polyurethane membrane, and relates to the technical field of polyurethane membrane preparation, in order to solve the technical problem that the micropores of the polyurethane membrane are shrunk and destroyed when preparing the porous polyurethane membrane in the prior art, and the actual porosity and uniformity of pore distribution of the polyurethane membrane are affected. The method for preparing the porous polyurethane membrane comprises: uniformly dissolving thermoplastic polyurethane particles in an organic solvent to obtain a polyurethane solution; uniformly coating the polyurethane solution on a glass slide to form a polyurethane membrane; soaking the glass slide formed with the polyurethane membrane in a first coagulation bath for 0.5 to 12 hours, soaking it in a second coagulation bath for 0.5 to 12 hours, taking it out and drying it to obtain a porous polyurethane membrane. Soak the porous polyurethane membrane obtained above in a fluorination solution for 0.5 to 12 hours, taking it out and drying it to obtain a fluorinated porous polyurethane membrane.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane film preparation, and in particular to a preparation and fluorination method of a porous polyurethane film and a fluorinated porous polyurethane film. Background Art

[0002] Polyurethane (PU) is a heterochain polymer with carbamate in the main chain, and is a polymer material with a wide range of physical properties. Due to its advantages such as oil resistance, high strength, and stable mechanical properties, it has attracted widespread attention from researchers and has achieved great application results in the fields of biomedicine, aerospace, etc. Polyurethane foam plastics, i.e., polyurethane porous materials, have a high specific surface area and a certain pore size. Because of its excellent processability and good adhesion, it can be used as a cushioning material, thermal insulation material, etc.

[0003] In the process of preparing porous polyurethane membrane by phase inversion method in the prior art, the components of the solvent and coagulation bath system used will play a decisive role in the structure, pore forming speed and pore size of the polyurethane membrane. The prior art discloses a method for preparing a polyurethane membrane with adjustable micropore size, including preparing a coagulation bath, mixing N,N-dimethylformamide (DMF) and water to prepare a coagulation bath; preparing an emulsion, emulsifying and dispersing the solvent N,N-dimethylformamide (DMF), an insoluble solvent and an emulsifier uniformly under mechanical stirring or ultrasound; preparing a slurry, Polyurethane resin, reinforcing material, foam control agent and emulsion are mechanically mixed to prepare polyurethane slurry; polyurethane slurry is coated, and the polyurethane slurry is coated on a glass plate or a plastic plate; solidification, the substrate coated with the polyurethane slurry film is immersed in a coagulation bath, and a polyurethane film is obtained after solidification; water washing, the film-like polyurethane resin obtained by solidification is washed with water in the coagulation bath, and the organic solvent remaining in the polyurethane resin is removed by rolling washing; drying, after water washing, the polyurethane resin is dried; through the above steps, a polyurethane film with adjustable micropore size is obtained. Using the above technical scheme, the substrate coated with the polyurethane slurry film is immersed in a coagulation bath, and after solidification, the polyurethane film is obtained. After that, the organic solvent on the surface of the polyurethane film needs to be removed by water washing and rolling washing to form a microporous structure, which will cause the shrinkage and destruction of the micropores of the polyurethane film, affecting the actual porosity of the polyurethane film and the uniformity of pore distribution. Therefore, a new preparation method of porous polyurethane film is urgently needed to solve the above technical problems. Summary of the invention

[0004] In order to solve the technical problem that the micropores of the polyurethane membrane are shrunk and destroyed when preparing the porous polyurethane membrane in the prior art, which affects the actual porosity and uniformity of the pore distribution of the polyurethane membrane, thereby affecting the performance of the porous polyurethane membrane, the present invention provides a method for preparing and fluorinating a porous polyurethane membrane and a fluorinated porous polyurethane membrane. In view of this, the present invention is implemented through the following technical solutions.

[0005] In a first aspect, the present invention provides a method for preparing a porous polyurethane membrane, comprising:

[0006] Thermoplastic polyurethane particles are uniformly dissolved in an organic solvent to obtain a polyurethane solution; wherein the mixing mass ratio of the thermoplastic polyurethane particles to the organic solvent is 1:(0.2-5);

[0007] Uniformly coating the polyurethane solution on a glass slide to form a polyurethane film;

[0008] The glass slide formed with the polyurethane film is sequentially immersed in a first coagulation bath for 0.5 to 12 hours and in a second coagulation bath for 0.5 to 12 hours, and then taken out and dried to obtain a porous polyurethane film, wherein the volatility of the second coagulation bath is greater than that of the first coagulation bath.

[0009] Compared with the prior art, in the preparation method of the porous polyurethane film of the present invention, a polyurethane solution can be obtained by uniformly dissolving thermoplastic polyurethane particles in an organic solvent, and a polyurethane film can be formed by uniformly coating the polyurethane solution on a glass slide. In the process of obtaining the polyurethane solution, the mixing mass ratio of the thermoplastic polyurethane particles to the organic solvent is controlled to be 1:(0.2-5), so that the polyurethane film has good mechanical properties. In the process of soaking the glass slide formed with the polyurethane film in the first coagulation bath for 0.5-12 hours, the surface of the polyurethane film is solidified, and the first coagulation bath forms a placeholder for the microscopic pores on the surface of the polyurethane film; in the process of soaking the glass slide formed with the polyurethane film in the second coagulation bath for 0.5-12 hours, the polyurethane film is further solidified, and the first coagulation bath in the pores on the surface of the polyurethane film and the second coagulation bath undergo phase transfer, so that the second coagulation bath replaces the first coagulation bath in the pores on the surface of the polyurethane film. In the present invention, the volatility of the second coagulation bath is greater than that of the first coagulation bath. During the drying process of the polyurethane film, the second coagulation bath can be prevented from remaining in the pores of the polyurethane film, thereby obtaining the porous polyurethane film with high porosity. At the same time, the technical solution of the present invention can prevent the pores on the surface of the obtained porous polyurethane film from shrinking or deforming, thereby affecting the porosity of the porous polyurethane film, by curing the polyurethane film twice in the first coagulation bath and the second coagulation bath. The above technical solution of the present invention solves the technical problem that the micropores of the polyurethane film shrink and destroy, which affects the actual porosity and uniformity of the pore distribution of the polyurethane film, and thus affects the performance of the porous polyurethane film when preparing the porous polyurethane film in the prior art.

[0010] Furthermore, in the method for preparing the porous polyurethane membrane of the present invention, the polyurethane solution is evenly coated on a glass slide, and the thickness of the formed polyurethane membrane is 20 to 2000 μm.

[0011] Furthermore, in the method for preparing the porous polyurethane membrane of the present invention, the organic solvent includes one or more of dichloromethane, C5 to C8 alkanes or cycloalkanes, monosubstituted or disubstituted monocyclic aromatic hydrocarbons, oxygen-containing organic solvents, nitrogen-containing organic solvents and heterocyclic organic solvents.

[0012] Furthermore, in the method for preparing the porous polyurethane membrane of the present invention, the polarity of the first coagulation bath is not equal to the polarity of the second coagulation bath.

[0013] Furthermore, in the preparation method of the porous polyurethane membrane of the present invention, the first coagulation bath comprises a mixture of at least two of water, saturated sodium chloride solution, phenol, propylene oxide, cyclohexane or n-hexane, C1 to C3 lower alcohols, oxygen-containing organic solvents, nitrogen-containing organic solvents and heterocyclic organic solvents.

[0014] Furthermore, in the method for preparing the porous polyurethane membrane of the present invention, the second coagulation bath includes one or more of dichloropropane, propylene oxide, C5 to C8 alkanes or cycloalkanes, mono-substituted or di-substituted monocyclic aromatic hydrocarbons, oxygen-containing organic solvents, nitrogen-containing organic solvents and heterocyclic organic solvents.

[0015] Furthermore, in the method for preparing the porous polyurethane membrane of the present invention, the drying temperature is 50-100°C.

[0016] In a second aspect, the present invention provides a method for fluorinating a porous polyurethane membrane, wherein the porous polyurethane membrane prepared by the above-mentioned method for preparing a porous polyurethane membrane further comprises:

[0017] mixing ethanol, perfluorosilicone and aqueous ammonia to obtain a fluorinated solution;

[0018] The porous polyurethane membrane is immersed in the fluorination solution for 0.5 to 12 hours, taken out and dried to obtain a fluorinated porous polyurethane membrane; wherein the volume ratio of the ethanol, perfluorosilicone and ammonia water is (1 to 1000): (0.1 to 10): (0.1 to 20), and the drying temperature is 50 to 100°C.

[0019] Compared with the prior art, the beneficial effects of the fluorination method of the porous polyurethane membrane provided by the present invention are the same as the beneficial effects of the preparation method of the porous polyurethane membrane described in the above technical solution, which will not be described in detail here.

[0020] Furthermore, in the fluorination method of the porous polyurethane membrane of the present invention, the perfluorosiloxane includes one or more of perfluorododecyltrichlorosilane, perfluorooctyltrimethoxysilane, perfluoroheptadecantrimethyloxysilane and perfluorodecyltriethoxysilane.

[0021] In a third aspect, the present invention provides a fluorinated porous polyurethane membrane, which is prepared by the above-mentioned fluorination method of the porous polyurethane membrane.

[0022] Compared with the prior art, the beneficial effects of the fluorinated porous polyurethane membrane provided by the present invention are the same as the beneficial effects of the fluorination method of the porous polyurethane membrane described in the above technical solution, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 Schematic diagram of a scanning electron microscope image of the fluorinated porous polyurethane membrane prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In the process of preparing porous polyurethane membrane by phase inversion method in the prior art, the components of the solvent and coagulation bath system used will play a decisive role in the structure, pore forming speed and pore size of the polyurethane membrane. The prior art discloses a method for preparing a polyurethane membrane with adjustable micropore size, including preparing a coagulation bath, mixing N,N-dimethylformamide (DMF) and water to prepare a coagulation bath; preparing an emulsion, emulsifying and dispersing the solvent N,N-dimethylformamide (DMF), an insoluble solvent and an emulsifier uniformly under mechanical stirring or ultrasound; preparing a slurry, The polyurethane resin, reinforcing material, foam control agent and emulsion are mechanically mixed to prepare polyurethane slurry; the polyurethane slurry is coated on a glass plate or a plastic plate; solidification is performed, the substrate coated with the polyurethane slurry film is immersed in a solidification bath, and a polyurethane film is obtained after solidification; water washing is performed, the film-like polyurethane resin obtained by solidification is washed with water in the solidification bath, and the organic solvent remaining in the polyurethane resin is removed by rolling washing; drying is performed after water washing, and the polyurethane resin is dried; through the above steps, a polyurethane film with adjustable micropore size is obtained. Using the above technical scheme, the substrate coated with the polyurethane slurry film is immersed in a solidification bath, and after solidification, the polyurethane film is obtained, and the organic solvent on the surface of the polyurethane film needs to be removed by water washing and rolling washing to form a microporous structure, which will cause the shrinkage or destruction of the micropores of the polyurethane film, affecting the actual porosity and uniformity of the pore distribution of the polyurethane film.

[0027] In order to solve the above technical problems, in a first aspect, the present invention provides a method for preparing a porous polyurethane membrane, comprising:

[0028] Thermoplastic polyurethane particles are uniformly dissolved in an organic solvent to obtain a polyurethane solution; wherein the mixing mass ratio of the thermoplastic polyurethane particles to the organic solvent is 1:(0.2-5);

[0029] Uniformly coating the polyurethane solution on a glass slide to form a polyurethane film;

[0030] The glass slide formed with the polyurethane film is sequentially immersed in a first coagulation bath for 0.5 to 12 hours and in a second coagulation bath for 0.5 to 12 hours, and then taken out and dried to obtain a porous polyurethane film, wherein the volatility of the second coagulation bath is greater than that of the first coagulation bath.

[0031] By adopting the above technical scheme, in the preparation method of the porous polyurethane film of the present invention, a polyurethane solution can be obtained by uniformly dissolving thermoplastic polyurethane particles in an organic solvent, and a polyurethane film can be formed by uniformly coating the polyurethane solution on a glass slide. In the process of obtaining the polyurethane solution, the mixing mass ratio of the thermoplastic polyurethane particles to the organic solvent is controlled to be 1: (0.2-5), so that the polyurethane film has good mechanical properties. In the process of soaking the glass slide formed with the polyurethane film in the first coagulation bath for 0.5-12 hours, the surface of the polyurethane film is solidified, and the first coagulation bath forms a placeholder for the microscopic pores on the surface of the polyurethane film; in the process of soaking the glass slide formed with the polyurethane film in the second coagulation bath for 0.5-12 hours, the polyurethane film is further solidified, and the first coagulation bath in the pores on the surface of the polyurethane film and the second coagulation bath undergo phase transfer, so that the second coagulation bath replaces the first coagulation bath in the pores on the surface of the polyurethane film. In the present invention, the volatility of the second coagulation bath is greater than that of the first coagulation bath, and during the drying process of the polyurethane film, the second coagulation bath can be prevented from remaining in the pores of the polyurethane film, thereby obtaining the porous polyurethane film with high porosity. At the same time, the technical solution of the present invention can prevent the pores on the surface of the obtained porous polyurethane film from shrinking or deforming, thereby affecting the porosity of the porous polyurethane film, by curing the polyurethane film twice in the first coagulation bath and the second coagulation bath. The polyurethane film is taken out from the second coagulation bath and dried to obtain a porous polyurethane film.

[0032] It should be understood that in the present invention, the polyurethane solution is evenly coated on the glass slide. In the process of forming the polyurethane film, in order to ensure the porosity requirement of the polyurethane film, the thickness of the polyurethane film needs to be controlled. It should be understood that the polyurethane solution is evenly coated on the glass slide, and the thickness of the polyurethane film formed can be 20 to 2000 μm. For example, the polyurethane solution is evenly coated on the glass slide, and the thickness of the polyurethane film formed can be 20 μm, 500 μm, 1000 μm, 1500 μm or 2000 μm.

[0033] It should also be understood that the thermoplastic polyurethane particles are uniformly dissolved in an organic solvent to obtain a polyurethane solution. The selection of the organic solvent has a great influence on the mechanical properties of the polyurethane film. The polar organic solvent can hydrogen bond with the polyurethane in the polyurethane solution, so that the molecular chains are arranged in order, and the obtained polyurethane film has good mechanical properties. Therefore, in order to obtain a polyurethane film with good mechanical properties, it is also necessary to control the type of the organic solvent. For example, the organic solvent includes one or more of dichloromethane, polar C5 to C8 alkanes or cycloalkanes, monosubstituted or disubstituted monocyclic aromatic hydrocarbons, oxygen-containing organic solvents, nitrogen-containing organic solvents, and heterocyclic organic solvents. As another example, the C5 to C8 alkane or cycloalkane, such as one or more of cyclohexane, n-hexane, pentane and octane, the mono-substituted or di-substituted monocyclic aromatic hydrocarbon, such as one or more of toluene, xylene, chlorobenzene, dichlorobenzene and phenol, the oxygen-containing organic solvent, such as one or more of cyclohexanone, toluene cyclohexanone, methanol, ethanol, isopropanol, ether, methyl acetate, ethyl acetate, propyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, the nitrogen-containing organic solvent, such as one or more of acetonitrile, N,N-dimethylformamide and dimethyl sulfoxide, the heterocyclic organic solvent, such as one or more of pyridine, tetrahydrofuran and dioxane.

[0034] As a possible implementation manner, in the method for preparing a porous polyurethane membrane provided by the present invention, the polarity of the first coagulation bath is not equal to the polarity of the second coagulation bath.

[0035] By adopting the above technical scheme, by controlling the polarity of the first coagulation bath to be not equal to the polarity of the second coagulation bath, during the process of preparing the porous polyurethane membrane, the first coagulation bath and the second coagulation bath in the pores on the surface of the polyurethane membrane are facilitated to phase transfer, so that the second coagulation bath replaces the first coagulation bath in the pores on the surface of the polyurethane membrane.

[0036] It should be understood that while the first coagulation bath forms a stable position on the micropores on the surface of the polyurethane film, in order to improve the curing efficiency of the polyurethane film surface, it is also necessary to control the type of the first coagulation bath. For example, the first coagulation bath includes a mixture of at least two of water, saturated sodium chloride solution, phenol, propylene oxide, cyclohexane or n-hexane, C1 to C3 lower alcohols, oxygen-containing organic solvents, nitrogen-containing organic solvents and heterocyclic organic solvents. For another example, the C1 to C3 lower alcohols are such as methanol, ethanol, and isopropanol, the oxygen-containing organic solvents are such as methyl acetate, ethyl acetate, propyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, the nitrogen-containing organic solvents are such as acetonitrile, N,N-dimethylformamide and dimethyl sulfoxide, and the heterocyclic organic solvents are such as pyridine, tetrahydrofuran and dioxane.

[0037] It should also be understood that in order to improve the phase transfer efficiency between the first coagulation bath and the second coagulation bath, and to increase the volatilization rate of the second coagulation bath when the polyurethane film is dried, it is also necessary to control the type of the second coagulation bath. The type of the second coagulation bath can be determined according to the polarity, and optionally should be a type with a polarity different from that of the first coagulation bath. For example, the second coagulation bath includes one or more of dichloropropane, propylene oxide, C5 to C8 alkanes or cycloalkanes, mono-substituted or di-substituted monocyclic aromatic hydrocarbons, oxygen-containing organic solvents, nitrogen-containing organic solvents and heterocyclic organic solvents. For another example, the C5 to C8 alkanes or cycloalkanes include cycloalkanes. One or more of hexane, n-hexane, pentane and octane, the monosubstituted or disubstituted monocyclic aromatic hydrocarbons include one or more of toluene, xylene, chlorobenzene, dichlorobenzene and phenol, the oxygen-containing organic solvent includes one or more of cyclohexanone, toluene cyclohexanone, methanol, ethanol, isopropanol, ether, methyl acetate, ethyl acetate, propyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, the nitrogen-containing organic solvent includes one or more of acetonitrile, N,N-dimethylformamide and dimethyl sulfoxide, and the heterocyclic organic solvent includes one or more of pyridine, tetrahydrofuran and dioxane.

[0038] It should also be understood that in order to improve the drying efficiency of the polyurethane film without affecting the physical properties of the polyurethane film, the drying temperature must be controlled. For example, the drying temperature can be selected to be 50-100°C. Specifically, the drying temperature can be 50-65°C, 65-80°C, 80-100°C. For example, the drying temperature can be 50, 65°C, 80°C, 90°C, or 100°C.

[0039] In a second aspect, the present invention provides a method for fluorinating a porous polyurethane membrane, wherein the porous polyurethane membrane prepared by the above-mentioned method for preparing a porous polyurethane membrane further comprises:

[0040] mixing ethanol, perfluorosilicone and aqueous ammonia to obtain a fluorinated solution;

[0041] The porous polyurethane membrane is immersed in the fluorination solution for 0.5 to 12 hours, taken out and dried to obtain a fluorinated porous polyurethane membrane; wherein the volume ratio of the ethanol, perfluorosilicone and ammonia water is (1 to 1000): (0.1 to 10): (0.1 to 20), and the drying temperature is 50 to 100°C.

[0042] Compared with the prior art, the beneficial effects of the fluorination method of the porous polyurethane membrane provided by the present invention are the same as the beneficial effects of the preparation method of the porous polyurethane membrane described in the above technical scheme. At the same time, by adopting the above technical scheme, ethanol has a dispersing effect on the perfluorosiloxane to obtain a uniform fluorination solution, and ammonia water is used to activate the fluorination reaction on the surface and in the micropores of the porous polyurethane membrane, so that the perfluorosiloxane modifies the functional groups on the surface and in the micropores of the porous polyurethane membrane, so that the surface and micropores of the porous polyurethane membrane are fluorinated, and a fluorinated porous polyurethane membrane is obtained. It should be understood that in order to improve the fluorination efficiency of the porous polyurethane membrane and obtain a porous polyurethane membrane with low surface energy, it is also necessary to control the mixing volume ratio of ethanol, perfluorosiloxane and ammonia water in the fluorination solution, as well as the fluorination time of the porous polyurethane membrane. For example, the volume ratio of ethanol, perfluorosiloxane and ammonia water in the fluorination solution is (1-1000): (0.1-10): (0.1-20), and the fluorination time is 0.5-12h. For another example, the volume ratio of ethanol, perfluorosiloxane and ammonia water in the fluorination solution can be 10:1:1, and the fluorination time can be 8h.

[0043] It should also be understood that in order to obtain the above-mentioned fluorinated porous polyurethane membrane with lower surface energy, it is also necessary to control the type of the perfluorosilicone. For example, the perfluorosilicone includes one or more of perfluorododecyltrichlorosilane, perfluorooctyltrimethoxysilane, perfluoroheptadecantrimethyloxysilane and perfluorodecyltriethoxysilane. For another example, the perfluorosilicone can be perfluorododecyltrichlorosilane.

[0044] In a third aspect, the present invention provides a fluorinated porous polyurethane membrane, which is prepared by the above-mentioned fluorination method of the porous polyurethane membrane.

[0045] Compared with the prior art, the beneficial effects of the fluorinated porous polyurethane membrane provided by the present invention are the same as the beneficial effects of the fluorination method of the porous polyurethane membrane described in the above technical solution, which will not be described in detail here.

[0046] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0047] Unless otherwise specified, the raw materials used in the following examples are commercially available.

[0048] Example 1

[0049] This embodiment provides a method for preparing a porous polyurethane film, comprising the following steps:

[0050] S100, 20 g of thermoplastic polyurethane particles and methyl acetate are mixed in a mass ratio of 1:1, and then treated with an ultrasonic dispersing mixer for 2 minutes to obtain a uniformly dissolved polyurethane solution, wherein the ultrasonic dispersing mixer has a treatment temperature of 40° C. and an operating frequency of 28 KHz;

[0051] S200, uniformly coating the polyurethane solution in step S100 on a glass slide with a scraper to form a polyurethane film with a thickness of 500 μm;

[0052] S300, soaking the glass slide with the polyurethane film formed in step S200 in N,N-dimethylformamide for 5 hours, and then soaking it in ethanol for 10 hours to allow the ethanol and the N,N-dimethylformamide to undergo phase transfer in the pores of the polyurethane film, and then taking it out and drying it to obtain a porous polyurethane film; wherein the drying temperature is 65°C.

[0053] The porosity of the porous polyurethane membrane prepared in this example is 42.56%.

[0054] Example 2

[0055] This embodiment provides a method for fluorinating a porous polyurethane membrane, comprising the following steps:

[0056] S100, 50 g of thermoplastic polyurethane particles are mixed with a mixed solution of dioxane and N,N-dimethylformamide at a mass ratio of 1:0.2, and then treated with an ultrasonic dispersing mixer for 2 minutes to obtain a uniformly dissolved polyurethane solution, wherein the amount of dioxane and N,N-dimethylformamide is 5 g, and the treatment temperature of the ultrasonic dispersing mixer is 40° C. and the operating frequency is 28 KHz;

[0057] S200, evenly coating the polyurethane solution in step S100 on a glass slide with a scraper to form a polyurethane film with a thickness of 20 μm;

[0058] S300, soaking the glass slide with the polyurethane film formed in step S200 in a mixed solution of ethanol and ether for 0.5 h, then soaking it in ethanol for 1 h, taking it out and drying it to obtain a porous polyurethane film; wherein the concentration of ethanol in the mixed solution is 70wt%, the concentration of ether is 30wt%, and the drying temperature is 50°C;

[0059] S400, 100 ml of ethanol is mixed with perfluoroheptadecantrimethylsilane and ammonia water in a volume ratio of 100:2:5 to obtain a fluorinated solution; the porous polyurethane membrane in the above step S300 is immersed in the fluorinated solution for 5 hours, and then taken out and dried to obtain a fluorinated porous polyurethane membrane; wherein the concentration of the ammonia water is 10wt%, and the drying method is to place it at room temperature for 24 hours to dry.

[0060] The porosity of the porous polyurethane membrane prepared in this embodiment is 39.27%. The surface energy of the porous polyurethane membrane prepared in this embodiment and the fluorinated porous polyurethane membrane are tested respectively, and the surface tension of the porous polyurethane membrane is 48.18 N / m 2 The surface tension of the fluorinated porous polyurethane membrane is 22.16 N / m 2 It can be seen that after the porous polyurethane membrane is fluorinated, its surface energy can be greatly reduced.

[0061] Example 3

[0062] This embodiment provides a method for fluorinating a porous polyurethane membrane, comprising the following steps:

[0063] S100, 20 g of thermoplastic polyurethane particles are mixed with a mixed solution of dioxane and N,N-dimethylformamide at a mass ratio of 1:5, and then treated with an ultrasonic disperser for 2 minutes to obtain a uniformly dissolved polyurethane solution, wherein the amount of dioxane and N,N-dimethylformamide is 50 g each, and the ultrasonic disperser is treated at a temperature of 40° C. and an operating frequency of 28 KHz;

[0064] S200, uniformly coating the polyurethane solution in step S100 on a glass slide with a scraper to form a polyurethane film with a thickness of 2000 μm;

[0065] S300, soaking the glass slide with the polyurethane film formed in step S200 in a mixed solution of methanol and ether for 12 hours, then soaking it in methanol for 12 hours, taking it out and drying it to obtain a porous polyurethane film; wherein the methanol in the mixed solution is 60wt%, the concentration of the ether is 40wt%, and the drying temperature is 100°C;

[0066] S400, 100 ml of ethanol is mixed with perfluorooctyltrimethoxysilane and ammonia water in a volume ratio of 50:1:5 to obtain a fluorination solution; the porous polyurethane membrane in the above step S300 is immersed in the fluorination solution for 7 hours, and then taken out and dried to obtain a fluorinated porous polyurethane membrane; wherein the concentration of the ammonia water is 10wt%, and the drying temperature is 45°C.

[0067] The porosity of the porous polyurethane membrane prepared in this embodiment is 36.48%. The surface energy of the porous polyurethane membrane prepared in this embodiment and the fluorinated porous polyurethane membrane are tested respectively, and the surface tension of the porous polyurethane membrane is 46.52 N / m 2 The surface tension of the fluorinated porous polyurethane membrane is 20.65 N / m 2 It can be seen that after the porous polyurethane membrane is fluorinated, its surface energy can be greatly reduced.

[0068] Comparative Example 1

[0069] The preparation method of the porous polyurethane membrane provided in this comparative example is basically the same as that of Example 1, except that in step S300, the glass slide formed with the polyurethane membrane is immersed in N,N-dimethylformamide for 5 hours, then taken out and dried to obtain the porous polyurethane membrane.

[0070] The porosity of the porous polyurethane film prepared in this comparative example is 30.12%, which is less than 42.56% in Example 1. The reason why the porosity of the porous polyurethane film in this comparative example is reduced is that after the glass slide formed with the polyurethane film is immersed in N,N-dimethylformamide for 5 hours, the micropores on the surface of the polyurethane film are not significantly cured compared with Example 1, causing the micropores on the surface of the formed polyurethane film to shrink.

[0071] Comparative Example 2

[0072] The preparation method of the porous polyurethane membrane provided in this comparative example is basically the same as that in Example 1, except that in step S300, the glass slide formed with the polyurethane membrane is not soaked in N,N-dimethylformamide, but is soaked in ethanol for 10 hours, taken out and dried to obtain a porous polyurethane membrane.

[0073] The porosity of the porous polyurethane film prepared in this comparative example is 27.32%, which is less than 42.56% in Example 1. The reason why the porosity of the porous polyurethane film in this comparative example is reduced is that after the glass slide formed with the polyurethane film is immersed in ethanol for 10 hours, the micropores on the surface of the polyurethane film are not significantly cured compared with Example 1, causing the micropores on the surface of the formed polyurethane film to shrink.

[0074] Comparative Example 3

[0075] This comparative example provides a method for preparing a porous polyurethane film, comprising the following steps:

[0076] S100, preparing a coagulation bath, mixing DMF and water to prepare a coagulation bath, wherein the DMF accounts for 5% of the total weight of the coagulation bath;

[0077] S200, preparing an emulsion, emulsifying the solvent, the insoluble solvent and the emulsifier under mechanical stirring or ultrasound;

[0078] 60 parts of N,N-dimethylformamide

[0079] 3 parts white oil

[0080] Fatty alcohol polyoxyethylene ether AEO-20 5 parts

[0081] S300, prepare slurry, polyurethane slurry is prepared according to the following formula:

[0082]

[0083] The polyurethane resin and the emulsion in S200 are uniformly mixed by mechanical stirring at room temperature to obtain a polyurethane slurry;

[0084] S400, coating polyurethane slurry, coating the polyurethane slurry on the glass plate with a coating thickness of 0.8 mm;

[0085] S500 coagulation: the polyurethane slurry coating after the slurry is coated on the substrate is subjected to wet coagulation treatment to obtain a polyurethane film after coagulation. The coagulation conditions are: DMF concentration 5%, temperature 15°C, and time 5 minutes;

[0086] S600, washing with water, removing the organic solvent remaining in the polyurethane resin from the cured film by rolling washing with water;

[0087] S700, drying, after washing with water, the polyurethane resin can be dried in a dryer at 60° C. for 5 minutes to obtain the porous polyurethane membrane;

[0088] The porosity of the porous polyurethane film prepared in this comparative example is 29.45%, which is less than 42.56% in Example 1. The reason why the porosity of the porous polyurethane film in this comparative example is less than that in Example 1 is that after the substrate coated with the polyurethane slurry film is immersed in a coagulation bath and the polyurethane film is obtained after coagulation, it is necessary to remove the organic solvent on the surface of the polyurethane film by water washing and rolling to form a microscopic pore structure, which will cause the shrinkage and destruction of the micropores of the polyurethane film, affecting the actual porosity of the polyurethane film.

[0089] Comparative Example 4

[0090] The fluorination method of the porous polyurethane membrane provided in this comparative example is basically the same as that of Example 1, except that in step S400, the fluorination solution consists of ethanol and perfluoroheptadecantrimethylsilane, and the mixing volume ratio of ethanol to perfluoroheptadecantrimethylsilane is 100:2.

[0091] The surface energy of the fluorinated porous polyurethane membrane prepared in this comparative example was tested, and the surface tension of the fluorinated porous polyurethane membrane was 32.45 N / m 2The surface energy of the fluorinated porous polyurethane membrane is higher than 22.16 N / m in Example 2. 2 This is because the fluorination solution in Example 2 contains ammonia water, and the presence of ammonia water can activate the functional groups on the surface of the porous polyurethane membrane, thereby enhancing the fluorination degree and fluorination efficiency of the porous polyurethane membrane.

[0092] It can be seen from the above embodiments, comparative examples, and test data that under the conditions of the embodiments of the present invention, a porous polyurethane membrane with high porosity can be obtained by soaking the polyurethane membrane in the first coagulation bath and the second coagulation bath in sequence and then taking it out and drying it. When the porous polyurethane membrane is fluorinated with a fluorination solution prepared from ethanol, perfluorosilicone and ammonia water, the fluorination efficiency can be improved and the surface energy of the porous polyurethane membrane can be significantly reduced. The fluorinated porous polyurethane membrane with low surface energy can be used to fill its micropores with functional materials according to the use requirements of the fluorinated porous polyurethane membrane, so that it can adapt to different application scenarios. At the same time, by fluorinating the surface and pores of the porous polyurethane membrane, even if the fluorination layer on the surface of the porous polyurethane membrane is worn during use, the porous polyurethane membrane still has low surface energy characteristics.

[0093] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0094] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a porous polyurethane membrane, characterized in that: Prepared by the following steps: Thermoplastic polyurethane particles are uniformly dissolved in an organic solvent to obtain a polyurethane solution; wherein the mixing mass ratio of the thermoplastic polyurethane particles to the organic solvent is 1:(0.2-5); Uniformly coating the polyurethane solution on a glass slide to form a polyurethane film; The glass slide formed with the polyurethane film is sequentially immersed in a first coagulation bath for 0.5 to 12 hours and in a second coagulation bath for 0.5 to 12 hours, and then taken out and dried to obtain a porous polyurethane film, wherein the volatility of the second coagulation bath is greater than that of the first coagulation bath; The organic solvent includes one or more of dichloromethane, a monosubstituted or disubstituted monocyclic aromatic hydrocarbon 1, an oxygen-containing organic solvent 1, a nitrogen-containing organic solvent 1, and a heterocyclic organic solvent 1; The first coagulation bath comprises a mixture of at least two of water, saturated sodium chloride solution, phenol, propylene oxide, cyclohexane, n-hexane, C1 to C3 lower alcohols, oxygen-containing organic solvent 2, nitrogen-containing organic solvent 2 and heterocyclic organic solvent 2; wherein, The oxygen-containing organic solvent 2 is methyl acetate, ethyl acetate, propyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether or ethylene glycol monobutyl ether; The nitrogen-containing organic solvent 2 is acetonitrile or N,N-dimethylformamide; The heterocyclic organic solvent 2 is pyridine, tetrahydrofuran or dioxane; The second coagulation bath comprises one or more of dichloropropane, propylene oxide, C5 to C8 alkanes, C5 to C8 cycloalkanes, monosubstituted or disubstituted monocyclic aromatic hydrocarbons 2, oxygen-containing organic solvents 3, nitrogen-containing organic solvents 3 and heterocyclic organic solvents 3; wherein, The monosubstituted or disubstituted monocyclic aromatic hydrocarbon 2 is one or more of toluene, xylene, chlorobenzene, dichlorobenzene and phenol; The oxygen-containing organic solvent 3 is one or more of cyclohexanone, toluene cyclohexanone, methanol, ethanol, isopropanol, ethyl ether, methyl acetate, ethyl acetate, propyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; The nitrogen-containing organic solvent 3 is one or more of acetonitrile and N,N-dimethylformamide; The heterocyclic organic solvent 3 is one or more of pyridine, tetrahydrofuran and dioxane.

2. The method for preparing a porous polyurethane membrane according to claim 1, characterized in that: The polyurethane solution is evenly coated on a glass slide, and the thickness of the formed polyurethane film is 20 to 2000 μm.

3. The method for preparing a porous polyurethane membrane according to claim 1, characterized in that: The polarity of the first coagulation bath is not equal to the polarity of the second coagulation bath.

4. The method for preparing a porous polyurethane membrane according to claim 1, characterized in that: The drying temperature is 50-100°C.

5. A method for fluorinating a porous polyurethane membrane, characterized in that: The porous polyurethane membrane prepared by the method for preparing a porous polyurethane membrane according to any one of claims 1 to 4 further comprises: mixing ethanol, perfluorosilicone and aqueous ammonia to obtain a fluorinated solution; The porous polyurethane membrane is immersed in the fluorination solution for 0.5 to 12 hours, taken out and dried to obtain a fluorinated porous polyurethane membrane; wherein the volume ratio of the ethanol, perfluorosilicone and ammonia water is (1 to 1000): (0.1 to 10): (0.1 to 20), and the drying temperature is 50 to 100°C.

6. The method for fluorination of a porous polyurethane membrane according to claim 5, characterized in that: The perfluorosiloxane includes one or more of perfluorooctyltrimethoxysilane, perfluoroheptadecantrimethoxysilane and perfluorodecyltriethoxysilane.

7. A fluorinated porous polyurethane membrane, characterized in that: The porous polyurethane film is prepared by the fluorination method of claim 5 or 6.

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