An epoxy-crosslinked polyimide film and a method for preparing the same

Abstract

The application discloses a polyimide film with epoxy cross-linking and a preparation method thereof. The preparation method comprises the following steps: step one, preparation of a polyamide acid solution; step two, preparation of a polyimide solution; and step three, preparation of a polyimide film. The polyimide film disclosed by the application forms a network microporous structure between polymer molecular chains by introducing a large-volume flexible cross-linking agent, increases gas permeability and gas selectivity, and thus improves the comprehensive gas separation performance of the polymer film material.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane technology, and more particularly to a polyimide membrane with epoxy crosslinking and its preparation method. Background Technology

[0002] Hydrogen and methane, as clean and low-carbon energy sources, are increasingly in demand in energy systems and transportation sectors (such as power generation, heating, and vehicle fuel). However, these feedstock streams often contain impurities such as CO2 and water, which must be removed to meet the purity requirements of end users.

[0003] Compared to traditional separation technologies such as chemical absorption, pressure swing adsorption, and cryogenic distillation, membrane-based separation technology, as an energy-saving and environmentally friendly process, is currently receiving special attention for specific CO2 removal applications. Among them, polyimide, due to its stable chemical structure and excellent mechanical properties, exhibits both high permeate flux and high selectivity when separating gas mixtures. Therefore, polyimide has become the most promising candidate for membrane materials and is widely used in the preparation of gas separation membranes.

[0004] Linear polyimide membranes have high permeability but low selectivity, while network polyimide membranes exhibit both high selectivity and low permeability. Combining the advantages of both to prepare polyimide membranes with excellent overall performance is of great significance for promoting the industrial application of this type of membrane. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a microporous polyimide membrane containing epoxy crosslinking with good thermal stability and excellent gas separation performance, as well as a method for its synthesis and preparation, so as to be suitable for fields such as greenhouse gas CO2 capture and natural gas helium extraction.

[0006] This application provides a polyimide film with epoxy crosslinking, wherein the polyimide film is obtained through the following chemical reaction;

[0007] .

[0008] A method for preparing an epoxy crosslinked polyimide film includes the following steps:

[0009] Step 1: Preparation of polyamic acid solution:

[0010] 1) Measure DAM and APAF with two amino groups (-NH2) into a reaction vessel and mix them. After mixing, evacuate the vessel and replace the nitrogen gas. Then add DMF into the reaction vessel and stir to obtain a mixed solution. The molar ratio of DAM to APAF is 19:1.

[0011] 2) Add 6FDA with two anhydride groups (-CO-O-CO-) to the mixed solution in batches and stir vigorously at room temperature for 12-36 h. After stirring, a polyamic acid solution is obtained.

[0012] Step 2: Preparation of polyimide solution:

[0013] 1) Add o-dichlorobenzene and isoquinoline to the polyamic acid solution prepared in step 1(2), and stir at 210°C for 12-36 h;

[0014] 2) After stirring, cool the solution to room temperature, then pour it into anhydrous methanol to precipitate solid powder, which is polyimide powder;

[0015] 3) The prepared polyimide powder was washed and dried, and then dissolved in DMF to obtain a polyimide solution;

[0016] Step 3: Preparation of the polyimide film:

[0017] 1) Add PGGE to the polyimide solution prepared in step 2 3) and keep it at 140℃ for 8~12 h. Then coat it on the surface of a clean glass plate and vacuum dry it at 50~80℃ to form a film; the molar ratio of PGGE to APAF is 2:1.

[0018] 2) After film formation, heat the film to 250-350℃ at a heating rate of 1-5℃ / min and maintain the temperature at this temperature for 1-5 h to obtain a polyimide film with epoxy crosslinking.

[0019] Preferably, the overall mass ratio of DAM, APAF and 6FDA in step 1) to DMF in step 1) is 1:5.

[0020] Preferably, the molar ratio of 6FDA in step 1(2) to the total molar ratio of DAM and APAF in step 1(1) is 1:1.

[0021] Preferably, the volume ratio of o-dichlorobenzene in step 2(1) to DMF in step 1(1) is 1:2.

[0022] Preferably, the mass ratio of polyimide powder to DMF in step 2 (3) is 1:10.

[0023] Compared with the prior art, the beneficial effects of this application are:

[0024] (1) This invention designs and synthesizes a type of linear polyimide with hydroxyl groups as crosslinking points. By regulating the crosslinking structure, the gas separation performance of the polymer material is improved. Based on this, a polyimide membrane with epoxy crosslinking micropores is designed and synthesized. By introducing a large-volume flexible crosslinking agent, a network microporous structure is formed between the polymer molecular chains, increasing gas permeability and gas selectivity, thereby improving the overall gas separation performance of the polymer membrane material. This solves the problems of low gas selectivity and poor plasticization resistance of existing polyimide membranes during use. It can be widely used in the fields of CO2 capture in the atmosphere, helium extraction from natural gas and other gas separation.

[0025] (2) The method for preparing a polyimide membrane with epoxy crosslinked micropores provided by the present invention uses 2,4,6-trimethyl-1,3-phenylenediamine (DAM), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (APAF) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as raw materials, and obtains a polyimide solution by sequentially passing polycondensation reaction and azeotropic imidization. Using polyethylene glycol diglycidyl ether (PGGE) as a crosslinking agent, a polyimide membrane with epoxy crosslinked micropores is obtained by sequentially passing epoxy ring-opening reaction, flat sheet film laying and thermal crosslinking. The prepared membrane has good gas selectivity and gas permeability, and the preparation process is simple and easy to operate, highly feasible, economical and environmentally friendly, and cost-saving.

[0026] It should be understood that the description in the Summary Section is not intended to limit the key or essential features of the embodiments of this application, nor is it intended to restrict the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0027] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0028] Figure 1 The chemical structural formula of DAM in the embodiments of the present invention is shown below;

[0029] Figure 2 The chemical structural formula of APAF in the embodiments of the present invention;

[0030] Figure 3 The chemical structural formula of 6FDA in the embodiments of the present invention;

[0031] Figure 4 The chemical structural formula of the crosslinking agent PGGE in the embodiments of the present invention is shown below;

[0032] Figure 5 This is a schematic diagram of the synthesis and preparation route of polyimide with epoxy cross-linked micropores in an embodiment of the present invention;

[0033] Figure 6 Figure 1 shows the gas separation characteristics of the polyimide membrane prepared in the embodiments of the present invention. (a) Figure 2 shows the relationship between the O2 permeability and O2 / N2 selectivity of the polyimide membrane with the upper limit of Robertson's rule; (b) Figure 3 shows the relationship between the CO2 permeability and CO2 / N2 selectivity of the polyimide membrane with the upper limit of Robertson's rule. Detailed Implementation

[0034] The present application 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 merely illustrative of the relevant application and not intended to limit the application. Furthermore, it should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available. This application will now be described in detail with reference to the accompanying drawings and embodiments. Example

[0036] Preparation of polyimide film CPI-T:

[0037] Step 1: Preparation of polyamic acid solution:

[0038] 1) Dry the reaction vessel at 120℃ for 3 h, cool it to room temperature, and measure 0.47 g (3.14 mmol) of DAM with two amino groups (-NH2) and 0.06 g (0.16 mmol) of APAF with two amino groups (-NH2) into the reaction vessel and mix them. After mixing, evacuate the vessel for 30 min and replace it with nitrogen three times. Then add 10 ml of DMF into the reaction vessel and stir until completely dissolved to obtain a mixed solution.

[0039] 2) Add a total of 1.47 g (3.3 mmol) of 6FDA with two anhydride groups (-CO-O-CO-) to the mixed solution in three portions, and stir vigorously at room temperature for 24 h. After stirring, a polyamic acid solution is obtained.

[0040] Step 2: Preparation of polyimide solution:

[0041] 1) Add 5 ml of o-dichlorobenzene and five drops of isoquinoline to the polyamic acid solution prepared in step 1(2), heat to 210°C, and stir at 210°C for 24 h;

[0042] 2) After stirring, cool the solution to room temperature, then pour it into anhydrous methanol to precipitate solid powder, which is polyimide powder;

[0043] 3) The prepared polyimide powder was washed three times with anhydrous methanol and water respectively, and then dried in a vacuum at 120°C for 24 h. After drying, 200 mg was weighed and dissolved in 2 ml of DMF to obtain a polyimide solution.

[0044] Step 3: Preparation of the polyimide film:

[0045] 1) Add 23 μl (0.032 mmol) of PGGE (the molar ratio of PGGE to APAF is 2:1, because only 200 mg of polyimide powder is taken here, and PGGE is weighed according to the molar ratio of 2:1, so the molar amount of PGGE is 0.032 mmol) to the polyimide solution prepared in step 2 3), heat to 140 °C, and keep at 140 °C for 10 h, then coat it on the surface of a clean glass plate, and vacuum dry at 60 °C for 12 h to form a film;

[0046] 2) After film formation, the temperature is increased to 300℃ at a rate of 5℃ / min and maintained at this temperature for 2 h to prepare polyimide film Film CPI-T.

[0047] Example 2: Gas separation performance test of polyimide membrane:

[0048] The gas separation characteristics test method for polyimide membranes is the "constant volume change pressure method": under working pressure conditions of 303.15 K and 0.2 MPa, a 2 cm... 2 The permeability of the polyimide membrane to N2, O2 and CO2 was tested respectively.

[0049] The gas separation performance test results of the polyimide membrane Film CPI-T are as follows: the permeability coefficient of N2 is 10.05 Barrer, the permeability coefficient of O2 is 34.4 Barrer, the permeability coefficient of CO2 is 326.8 Barrer, the CO2 / N2 selectivity is 32.5, and the O2 / N2 selectivity is 3.4.

[0050] The gas separation performance results are attached. Figure 6 As shown, the separation performance of CO2 / N2 and O2 / N2 is close to the upper limit of Robeson's 2008 standard. The test results indicate that the prepared polyimide membrane with epoxy cross-linked micropores possesses excellent gas permeability and gas selectivity, making it highly valuable in the field of gas separation membranes and possessing significant industrial application potential.

[0051] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0052] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An epoxy-crosslinked polyimide film, characterized by, The polyimide film is obtained by the following chemical reaction: 。 2. A method for producing an epoxy-crosslinked polyimide film, characterized by, The method comprises the following steps: Step one: preparation of a polyamide acid solution 1) A DAM with two amino groups (-NH2) and an APAF are weighed into a reaction container and mixed. After mixing, vacuum is applied and replaced with nitrogen. Then, DMF is added to the reaction container, and stirring is performed to obtain a mixed solution. The molar ratio of DAM to APAF is 19:1; 2) A 6FDA with two anhydride groups (-CO-O-CO-) is added to the mixed solution in batches, and vigorous stirring is performed at room temperature for 12-36 h. After stirring is completed, the polyamide acid solution is obtained; Step two: preparation of a polyimide solution 1) The polyamide acid solution prepared in step one 2) is added with o-dichlorobenzene and isoquinoline, and stirring is performed at 210°C for 12-36 h; 2) The solution after stirring is completed is cooled to room temperature, and then poured into anhydrous methanol to precipitate a solid powder, which is a polyimide powder; 3) The prepared polyimide powder is washed and dried, and then dissolved in DMF to obtain the polyimide solution; Step three: preparation of a polyimide film 1) The polyimide solution prepared in step two 3) is added with PGGE, and kept at 140°C for 8-12 h. Then, the solution is coated on the surface of a clean glass plate, and vacuum dried at 50-80°C to form a film. The molar ratio of PGGE to APAF is 2:1; 2) After film formation, the temperature is increased to 250-350°C at a temperature increasing rate of 1-5°C / min, and kept at the temperature for 1-5 h, to obtain a polyimide film with epoxy crosslinking.

3. The method for producing a polyimide film having an epoxy crosslink according to claim 2, characterized by, The total mass of DAM, APAF in step one 1) and 6FDA in step one 2) is 1:5 of the mass of DMF in step one 1).

4. The method for producing a polyimide film having an epoxy crosslink according to claim 3, characterized by, The molar amount of 6FDA in step one 2) is 1:1 of the total molar amount of DAM and APAF in step one 1).

5. The method for producing a polyimide film having an epoxy crosslink according to claim 4, characterized by, The volume ratio of o-dichlorobenzene in step two 1) to DMF in step one 1) is 1:

2.

6. The method for producing a polyimide film having an epoxy crosslink according to claim 5, characterized by, The mass ratio of the polyimide powder in step two 3) to DMF is 1:10.

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