Surface-modified polyimide film, method for preparing hollow fiber, and application thereof

Abstract

The embodiments of the present disclosure disclose a surface-modified polyimide film, a preparation method and application of hollow fibers. The preparation method of the surface-modified polyimide film comprises: preparing a polyimide; implanting a bromine group on the main chain of the polyimide to obtain a brominated polyimide; forming a film from the brominated polyimide to obtain a brominated polyimide film; and treating the surface of the brominated polyimide film with a CO2-philic group to obtain a surface-modified polyimide film. The surface-modified polyimide film prepared by the preparation method has high selectivity and high permeability in CO2 capture.

Description

Technical Field

[0001] This disclosure relates to the field of gas separation technology, and in particular to the preparation methods and applications of surface-modified polyimide films and hollow fibers. Background Technology

[0002] Excessive CO2 emissions into the atmosphere have a severe impact on the ecological environment and human life, making it one of the major environmental problems today. Controlling CO2 emissions through carbon capture and storage (CCS) is an effective method to mitigate this environmental problem. Membrane technology has shown great potential in CO2 separation. Gas separation membranes made from cellulose acetate (CA), polysulfone (PSf), polydimethylsiloxane (PDMS), and polyimide (PI) have been widely developed for industrial applications. Among them, polyimide membranes have the advantages of excellent thermal and chemical stability and are easy to fabricate, making them the most widely used in industrial applications.

[0003] However, the inventors discovered that existing polyimide films cannot simultaneously possess both high selectivity and high permeability in CO2 capture, and their performance needs further improvement. Summary of the Invention

[0004] In view of this, the present disclosure provides a method for preparing surface-modified polyimide films and hollow fibers, and their applications, which can achieve both high selectivity and high permeability in CO2 capture.

[0005] In a first aspect, embodiments of this disclosure provide a method for preparing a surface-modified polyimide film, employing the following technical solution:

[0006] The method for preparing the surface-modified polyimide film includes:

[0007] Preparation of polyimide;

[0008] By inserting bromine groups into the main chain of polyimide, bromine-substituted polyimide is obtained;

[0009] The brominated polyimide was made into a thin film to obtain a brominated polyimide film;

[0010] The surface of a brominated polyimide film was treated with CO2-loving groups to obtain a surface-modified polyimide film.

[0011] Optionally, the surface treatment of the brominated polyimide film using CO2-loving groups includes:

[0012] The brominated polyimide film is fixed in the film-forming frame;

[0013] A CO2-loving solution is poured into the film-forming framework and reacted with the surface of the brominated polyimide film.

[0014] Optionally, the CO2-loving group is one of ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-aniline, 2,2'-diaminobiphenyl, 4,4”-diaminoterphenyl, p-aminobenzoic acid, m-aminobenzoic acid, 3,5-diaminobenzoic acid, glycine, L-serine, L-threonine, L-glutamic acid, L-arginine, L-histidine, L-tyrosine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyethyleneimine.

[0015] Optionally, the concentration range of the CO2-loving group solution is 0.01 wt% to 10 wt%.

[0016] Optionally, the solvent in the CO2-loving group solution is one of water, methanol, or ethanol.

[0017] Optionally, the reaction time between the CO2-loving solution and the surface of the brominated polyimide film is between 1 min and 60 min.

[0018] Optionally, the surface treatment of the brominated polyimide film using CO2-loving groups further includes:

[0019] After the reaction is complete, the surface is washed and soaked with a solvent containing CO2-loving groups to remove excess CO2-loving groups.

[0020] Secondly, the embodiments of this disclosure provide the application of surface-modified polyimide films prepared by the preparation method of any of the above-described surface-modified polyimide films in CO2 capture.

[0021] Thirdly, this disclosure provides a method for preparing surface-modified polyimide hollow fibers, employing the following technical solution:

[0022] The method for preparing the surface-modified polyimide hollow fiber includes:

[0023] Preparation of polyimide;

[0024] By inserting bromine groups into the main chain of polyimide, bromine-substituted polyimide is obtained;

[0025] The brominated polyimide is spun to obtain brominated polyimide hollow fibers;

[0026] By treating the inner surface of brominated polyimide hollow fibers with CO2-loving groups, surface-modified polyimide hollow fibers are obtained.

[0027] Fourthly, this disclosure provides an application of surface-modified polyimide hollow fibers prepared by the above-described method in CO2 capture.

[0028] This disclosure provides a method for preparing surface-modified polyimide films and hollow fibers, as well as their applications. In the preparation of the surface-modified polyimide film, on one hand, bromine groups are implanted into the main chain of the polyimide to obtain brominated polyimide. The introduction of bromine groups alters the original pore structure of the polyimide, increasing free volume and facilitating CO2 transport, thus improving CO2 solubility and permeability. On the other hand, the surface of the brominated polyimide film is treated with CO2-loving groups. During this treatment, the high reactivity between the CO2-loving groups and the bromine groups modifies the surface of the brominated polyimide film, completing the grafting process and thereby improving the selectivity for CO2. Therefore, the surface-modified polyimide film prepared by the method provided in this disclosure exhibits both high selectivity and high permeability in CO2 capture.

[0029] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A flowchart illustrating the method for preparing a surface-modified polyimide film according to embodiments of this disclosure;

[0032] Figure 2 A flowchart illustrating the preparation method of surface-modified polyimide hollow fibers provided in this disclosure embodiment. Detailed Implementation

[0033] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the accompanying drawings.

[0034] It should be noted that, where there is no conflict, the embodiments and features described in this disclosure can be combined with each other. The technical solutions of this disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] Unless otherwise stated, the exemplary implementations / embodiments shown are to be understood as providing exemplary features of various details that provide ways in which the technical concepts of this disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of various implementations / embodiments may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concepts of this disclosure.

[0036] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0037] This disclosure provides a method for preparing a surface-modified polyimide film, specifically, as follows: Figure 1 As shown, the method for preparing this surface-modified polyimide film includes:

[0038] Step S11: Prepare polyimide.

[0039] Optionally, the preparation of polyimide includes: preparing a polyamic acid solution, and chemically imidizing the polyamic acid solution to obtain polyimide (PI).

[0040] For example, under an argon atmosphere, diamine is added to a three-necked flask, followed by anhydrous N,N-dimethylacetamide (DMAc). After complete dissolution, dianhydride is added in batches, followed by DMAc washing. The reaction is carried out at a low temperature (generally using an ice bath or circulating cooling pump to maintain the low temperature, within the range of 0-5°C) for 24 hours to obtain a polyamic acid solution with a solid content of 25%. Acetic anhydride and 3-methylpyridine are slowly added to the polyamic acid solution, and the reaction is stirred at room temperature for 24 hours to obtain a polyimide solution. After the reaction is complete, the polyimide solution can be slowly poured into an appropriate amount of methanol to precipitate, thus obtaining filamentous polyimide. This filamentous polyimide is then washed three times with methanol and dried in a vacuum oven at 60°C for 24 hours.

[0041] The diamine can be one of 2,4,6-trimethyl-1,3-phenylenediamine (DAM), 2,3,5,6-tetramethyl-1,4-phenylenediamine (MPD), 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD), or 4,4'-diamino-3,3'-dimethylbiphenyl (OTD), and the dianhydride can be one of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) or bisphenol A type diether dianhydride (BPADA).

[0042] Step S12: Insert bromine groups into the main chain of polyimide to obtain bromine polyimide.

[0043] Optionally, the polyimide synthesized in step S11 is dissolved in 1,2-dichloroethane, and N-bromosuccinimide (NBS) and 2,2-azobisisobutyronitrile (AIBN) are added. The mixture is refluxed and the reaction is carried out. The solution after the reaction is slowly poured into an appropriate amount of methanol to precipitate the precipitate, which is the bromopolyimide (PI-Br).

[0044] For example, the polyimide synthesized in step S11 is added to a three-necked flask, 1,2-dichloroethane is added and magnetically stirred to dissolve it, N-bromosuccinimide (NBS) and 2,2-azobisisobutyronitrile (AIBN) are added to the three-necked flask, and the mixture is refluxed at 80°C for 4 hours. The resulting solution is slowly poured into an appropriate amount of methanol to precipitate the polymer. The precipitated polymer is washed three times with methanol and then dried in a vacuum oven at 60°C for 24 hours to obtain brominated polyimide.

[0045] Optionally, in step S12, the molar ratio of N-bromosuccinimide (NBS) to 2,2-azobisisobutyronitrile (AIBN) is 1:1 to 10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. Within this range of molar ratios, bromine groups can be sufficiently implanted into the main chain of the polyimide without wasting raw materials.

[0046] For example, the chemical reaction that occurs in step S12 when bromine groups are implanted into the main chain of polyimide is as follows:

[0047]

[0048] Ar1 is selected from 4,4'-(hexafluoroisopropene) phthalic anhydride (6FDA) and bisphenol A type diether dianhydride (BPADA);

[0049] Ar2 is selected from one of 2,4,6-trimethyl-1,3-phenylenediamine (DAM), 2,3,5,6-tetramethyl-1,4-phenylenediamine (MPD), 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD), and 4,4'-diamino-3,3'-dimethylbiphenyl (OTD).

[0050] Step S13: The brominated polyimide is made into a film to obtain a brominated polyimide film.

[0051] For example, brominated polyimide is dissolved and dried to form a film, thereby obtaining a brominated polyimide film.

[0052] Step S14: Treat the surface of the brominated polyimide film with CO2-loving groups to obtain a surface-modified polyimide film.

[0053] Optionally, in step S14, the surface of the brominated polyimide film is treated with CO2-loving groups, including:

[0054] The brominated polyimide film is fixed in the film-forming frame;

[0055] A CO2-loving solution is poured into the film-forming framework and reacted with the surface of the brominated polyimide film.

[0056] Optionally, the CO2-loving group in the embodiments of this disclosure may be one of ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-aniline, 2,2'-diaminobiphenyl, 4,4”-diaminoterphenyl, p-aminobenzoic acid, m-aminobenzoic acid, 3,5-diaminobenzoic acid, glycine, L-serine, L-threonine, L-glutamic acid, L-arginine, L-histidine, L-tyrosine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyethyleneimine.

[0057] Optionally, the concentration of the CO2-loving group solution ranges from 0.01 wt% to 10 wt%, for example, the concentration of the CO2-loving group solution is 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. Within this concentration range, the CO2-loving groups can react sufficiently with the surface of the brominated polyimide film without wasting raw materials.

[0058] Optionally, the solvent in the CO2-loving group solution is one of water, methanol, or ethanol.

[0059] Optionally, the reaction time between the CO2-loving group solution and the surface of the brominated polyimide film is between 1 min and 60 min, for example, 1 min, 2 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min. Within this time range, the CO2-loving groups can react fully with the surface of the brominated polyimide film with high efficiency.

[0060] For example, the chemical reaction between the CO2-loving solution and the surface of the brominated polyimide film in step S14 is as follows:

[0061]

[0062] Ar1 is selected from 4,4'-(hexafluoroisopropene) phthalic anhydride (6FDA) and bisphenol A type diether dianhydride (BPADA);

[0063] Ar2 is selected from one of 2,4,6-trimethyl-1,3-phenylenediamine (DAM), 2,3,5,6-tetramethyl-1,4-phenylenediamine (MPD), 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD), and 4,4'-diamino-3,3'-dimethylbiphenyl (OTD);

[0064] Ar3 is selected from one of the following: ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-aniline, 2,2'-diaminobiphenyl, 4,4”-diaminoterphenyl, p-aminobenzoic acid, m-aminobenzoic acid, 3,5-diaminobenzoic acid, glycine, L-serine, L-threonine, L-glutamic acid, L-arginine, L-histidine, L-tyrosine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyethyleneimine.

[0065] Optionally, treating the surface of the brominated polyimide film with CO2-loving groups further includes: after the reaction, washing and soaking with a solvent containing CO2-loving groups to remove excess CO2-loving groups from the surface. Specifically, after the reaction, the excess CO2-loving group solution is poured out, the brominated polyimide film is removed from the film-forming frame, and washed and soaked with a solvent containing CO2-loving groups for 72 hours to remove excess CO2-loving groups from the surface, then dried and collected.

[0066] This disclosure provides a method for preparing surface-modified polyimide films and hollow fibers, as well as their applications. In the preparation of the surface-modified polyimide film, on one hand, bromine groups are implanted into the main chain of the polyimide to obtain brominated polyimide. The introduction of bromine groups alters the original pore structure of the polyimide, increasing free volume and facilitating CO2 transport, thus improving CO2 solubility and permeability. On the other hand, the surface of the brominated polyimide film is treated with CO2-loving groups. During this treatment, the high reactivity between the CO2-loving groups and the bromine groups modifies the surface of the brominated polyimide, completing grafting and forming a naturally ordered nano-molecular brush structure on the film surface, thereby enhancing CO2 selectivity. Therefore, the surface-modified polyimide film prepared by the method provided in this disclosure exhibits both high selectivity and high permeability in CO2 capture.

[0067] Furthermore, CO2-loving groups can further enhance the CO2 permeability of surface-modified polyimide films. The reason is as follows: A special case of CO2 permeation is chemically enhanced transport, in which CO2 molecules react with specific chemical groups in the hydrated membrane, thus permeating more quickly. CO2-loving groups can reversibly absorb CO2 under pressure changes, binding with CO2 at high pressure and releasing CO2 at low pressure. After surface monomolecular modification of brominated polyimide films with CO2-loving groups, the pressure difference across the surface-modified polyimide film will significantly promote CO2 transport across the film.

[0068] In addition, the preparation method of the surface-modified polyimide film provided in this disclosure is simple, the raw materials are readily available, the conditions are mild, the structural properties of the surface-modified polyimide film are controllable, and it is easy to mass-produce.

[0069] Furthermore, this disclosure also provides a method for preparing surface-modified polyimide hollow fibers, specifically, as follows: Figure 2 As shown, the preparation method of surface-modified polyimide hollow fibers includes:

[0070] Step S21: Prepare polyimide.

[0071] Step S22: Insert bromine groups into the main chain of polyimide to obtain bromine polyimide.

[0072] Step S23: Spin the brominated polyimide to obtain brominated polyimide hollow fibers.

[0073] Step S24: Treat the inner surface of the brominated polyimide hollow fiber with CO2-loving groups to obtain surface-modified polyimide hollow fiber.

[0074] It should be noted that the specific details of each of the above steps can be found in the corresponding steps of the preparation method of surface-modified polyimide film, and will not be repeated here.

[0075] The surface-modified polyimide film and surface-modified polyimide hollow fiber prepared in the embodiments of this disclosure can be applied to CO2 capture, and both can effectively improve the selectivity and permeability of CO2 capture.

[0076] To facilitate a better understanding and implementation of the preparation method of surface-modified polyimide film provided in the embodiments of this disclosure by those skilled in the art, several specific embodiments are provided below for illustration.

[0077] Example 1

[0078] The preparation process of surface-modified polyimide films is as follows:

[0079] (1) Add 3.0044 g of 2,4,6-trimethyl-1,3-phenylenediamine (DAM) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0080] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine were slowly added to the solution obtained in (1), and the mixture was stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction was slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide was then washed three times with methanol and dried in a vacuum oven at 60 °C for 24 h.

[0081] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 4.7805g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:1). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0082] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0083] (5) Prepare a 0.01 wt% 1,6-hexanediamine solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 60 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0084] Example 2

[0085] The preparation process of surface-modified polyimide films is as follows:

[0086] (1) Add 3.2845 g of 2,3,5,6-tetramethyl-1,4-phenylenediamine (MPD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0087] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0088] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 14.3415g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:3). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0089] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0090] (5) Prepare a 0.1 wt% naphthalene diamine solution with ethanol, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 30 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with ethanol for 72 h to remove excess groups on the surface, and collect it after drying.

[0091] Example 3

[0092] The preparation process of surface-modified polyimide films is as follows:

[0093] (1) Add 4.2458 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0094] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0095] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 23.9025g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:5). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0096] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0097] (5) Prepare a 1 wt% p-phenylenediamine solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 10 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0098] Example 4

[0099] The preparation process of surface-modified polyimide films is as follows:

[0100] (1) Add 4.2458 g of 4,4'-diamino-3,3'-dimethylbiphenyl (OTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0101] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain polyimide (PI). The polyimide solution obtained by reaction is slowly poured into an appropriate amount of methanol to precipitate, and filamentous PI is obtained. The PI is then washed three times with methanol and dried in a vacuum oven at 60 °C for 24 h.

[0102] (3) Weigh 5g of PI obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 33.4635g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:7). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0103] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0104] (5) Prepare a 3wt% p-aminobenzoic acid solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 5 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0105] Example 5

[0106] The preparation process of surface-modified polyimide films is as follows:

[0107] (1) Add 4.2458 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 5.2049 g of bisphenol A type diether dianhydride (BPADA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0108] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0109] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 47.8050g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:10). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0110] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0111] (5) Prepare a 5wt% glycine solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 3 minutes, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 hours to remove excess groups on the surface, and collect it after drying.

[0112] Example 6

[0113] The preparation process of surface-modified polyimide films is as follows:

[0114] (1) Add 4.2458 g of 4,4'-diamino-3,3'-dimethylbiphenyl (OTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 5.2049 g of bisphenol A type diether dianhydride (BPADA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0115] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0116] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 47.8050g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:10). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0117] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0118] (5) Prepare a 10wt% L-histidine solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 1 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0119] Example 7

[0120] The preparation process of surface-modified polyimide films is as follows:

[0121] (1) Add 4.2458 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (MOTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0122] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0123] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 47.8050g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:10). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0124] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0125] (5) Prepare a 7wt% m-aminobenzoic acid solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 1 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0126] Example 8

[0127] The preparation process of surface-modified polyimide films is as follows:

[0128] (1) Add 4.2458 g of 4,4'-diamino-3,3'-dimethylbiphenyl (OTD) to a three-necked flask that has been pre-dried, then add 20 ml of anhydrous N,N-dimethylacetamide (DMAc) solvent and stir. After complete dissolution, add 8.8848 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) and add 40 ml of DMAc to wash. React at low temperature for 24 h to obtain a polyamic acid solution with a solid content of 25%.

[0129] (2) Imidization of polyamic acid solution by chemical method: 38 ml of acetic anhydride and 15 ml of 3-methylpyridine are slowly added to the solution obtained in (1), and the mixture is stirred at room temperature for 24 h to obtain a polyimide solution. The polyimide solution obtained by the reaction is slowly poured into an appropriate amount of methanol to precipitate, thereby obtaining filamentous polyimide. The filamentous polyimide is then washed three times with methanol and placed in a vacuum oven at 60°C for 24 hours to dry.

[0130] (3) Weigh 5g of the polyimide obtained in (2) and add it to a 250mL three-necked flask. Add 100mL of 1,2-dichloroethane and stir magnetically to dissolve. Add 47.8050g of N-bromosuccinimide (NBS) and 4.4110g of 2,2-azobisisobutyronitrile (AIBN) to the three-necked flask (the molar ratio of AIBN to NBS is 1:10). Reflux the mixture at 80℃ for 4h. Slowly pour the resulting solution into an appropriate amount of methanol to precipitate the polymer. Wash the precipitated polymer three times with methanol and dry it in a vacuum oven at 60℃ for 24 hours to obtain brominated polyimide.

[0131] (4) The brominated polyimide is coated and fixed in the film-forming frame. The film-forming frame consists of a solid acrylic plate and a hollow acrylic plate of 3.5cm×3.5cm.

[0132] (5) Prepare a 9wt% 4,4”-diaminoterphenyl solution with deionized water, introduce the solution into the film-forming frame, react with the surface of the brominated polyimide film for 1 min, pour out the excess solution, take out the surface-modified polyimide film, wash and soak it with deionized water for 72 h to remove excess groups on the surface, and collect it after drying.

[0133] In comparison, this disclosure also provides eight comparative polyimide films. The preparation processes of the comparative polyimide films of Comparative Examples 1 to 8 correspond to steps (1), (2) and (4) in Examples 1-8, respectively. In step (4), the brominated polyimide is replaced with polyimide.

[0134] The comparison results of CO2 permeability and selectivity of the surface-modified polyimide film (i.e., the surface-modified polyimide film prepared in Examples 1-8) and the surface-unmodified polyimide film (i.e., the comparative polyimide film prepared in Comparative Examples 1-8) are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] As shown in Table 1, the CO2 permeability coefficient P(Barrer) of the surface-modified polyimide films is significantly higher than that of the corresponding control polyimide films. The CH4 permeability coefficient P(Barrer) of some surface-modified polyimide films is lower than that of the corresponding control polyimide films, while the CH4 permeability coefficient P(Barrer) of some surface-modified polyimide films is higher than that of the corresponding control polyimide films. However, the CO2 / CH4 selectivity of all surface-modified polyimide films is significantly higher than that of the corresponding control polyimide films.

[0139] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0140] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0141] Those skilled in the art should understand that the above embodiments are merely for illustrating the present disclosure and are not intended to limit the scope of the disclosure. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present disclosure.

Claims

1. A method for preparing a surface-modified polyimide film, characterized in that, include: The preparation of polyimide includes: preparing a polyamic acid solution, and imidizing the polyamic acid solution using a chemical method to obtain polyimide; Brominated polyimide is obtained by implanting bromine groups into the main chain of polyimide, including: dissolving the synthesized polyimide in 1,2-dichloroethane, adding N-bromosuccinimide (NBS) and 2,2-azobisisobutyronitrile (AIBN), refluxing the reaction, and slowly pouring the solution after the reaction into an appropriate amount of methanol to precipitate the precipitate, which is the brominated polyimide; The process of forming a bromopolyimide film includes: dissolving and drying the bromopolyimide to form a film, thereby obtaining a bromopolyimide film. A surface-modified polyimide film is obtained by treating the surface of a brominated polyimide film with CO2-loving groups, including: fixing the brominated polyimide film in a film-forming frame; pouring a CO2-loving group solution into the film-forming frame and reacting it with the surface of the brominated polyimide film; The CO2-loving group is one of the following: ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-aniline, 2,2'-diaminobiphenyl, 4,4''-diaminoterphenyl, p-aminobenzoic acid, m-aminobenzoic acid, 3,5-diaminobenzoic acid, glycine, L-serine, L-threonine, L-glutamic acid, L-arginine, L-histidine, L-tyrosine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyethyleneimine.

2. The preparation method according to claim 1, characterized in that, The concentration range of the CO2-loving group solution is 0.01wt% to 10wt%.

3. The preparation method according to claim 1, characterized in that, The solvent in the CO2-loving solution is one of water, methanol, or ethanol.

4. The preparation method according to claim 1, characterized in that, The reaction time between the CO2-loving solution and the surface of the brominated polyimide film ranged from 1 min to 60 min.

5. The preparation method according to claim 1, characterized in that, The surface treatment of the brominated polyimide film using CO2-loving groups further includes: After the reaction is complete, the surface is washed and soaked with a solvent containing CO2-loving groups to remove excess CO2-loving groups.

6. The application of the surface-modified polyimide film prepared by the method of any one of claims 1 to 5 in CO2 capture.

7. A method for preparing surface-modified polyimide hollow fibers, characterized in that, include: The preparation of polyimide includes: preparing a polyamic acid solution, and imidizing the polyamic acid solution using a chemical method to obtain polyimide; Brominated polyimide is obtained by implanting bromine groups into the main chain of polyimide, including: dissolving the synthesized polyimide in 1,2-dichloroethane, adding N-bromosuccinimide (NBS) and 2,2-azobisisobutyronitrile (AIBN), refluxing the reaction, and slowly pouring the solution after the reaction into an appropriate amount of methanol to precipitate the precipitate, which is the brominated polyimide; Spinning the brominated polyimide to obtain brominated polyimide hollow fibers includes: dissolving the brominated polyimide and spinning it to obtain brominated polyimide hollow fibers. The inner surface of brominated polyimide hollow fibers is treated with CO2-loving groups to obtain surface-modified polyimide hollow fibers. The process includes: pouring a CO2-loving group solution into a container holding brominated polyimide hollow fibers and reacting it with the inner surface of the brominated polyimide hollow fibers. The CO2-loving group is one of the following: ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, o-aniline, 2,2'-diaminobiphenyl, 4,4''-diaminoterphenyl, p-aminobenzoic acid, m-aminobenzoic acid, 3,5-diaminobenzoic acid, glycine, L-serine, L-threonine, L-glutamic acid, L-arginine, L-histidine, L-tyrosine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and polyethyleneimine.

8. The application of surface-modified polyimide hollow fibers prepared by the method of claim 7 in CO2 capture.

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