A polyimide membrane material, its preparation method, and its application in iodine adsorption.

Abstract

This invention provides a polyimide membrane material, its preparation method, and its application in iodine adsorption, relating to the field of adsorption materials technology. The invention involves mixing a crosslinking agent, a dialdehyde monomer, a diamine monomer, and an aprotic solvent to undergo a Schiff base reaction. The resulting polyimide solution is then desolventized to form a membrane, yielding the polyimide membrane material. The crosslinking agent includes 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine. The polyimide membrane material prepared by this invention exhibits excellent iodine adsorption capacity and adsorption stability; it contains dynamic imine bonds, allowing broken polyimide membrane materials to be reshaped and restored under hot-pressing conditions, making it easily recyclable; the polyimide membrane material also possesses excellent mechanical properties. Furthermore, compared to powdered iodine adsorption materials, the membrane material overcomes the tendency to agglomerate, demonstrating good cost-effectiveness and user-friendliness; and the invention allows for the preparation of polyimide at room temperature, making the process simple.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, and in particular to a polyimide membrane material, its preparation method, and its application in iodine adsorption. Background Technology

[0002] Radioactive iodine ( 129 I and 131 I) are common pollutants associated with nuclear power plant proliferation. They have high chemical reactivity and long half-lives (e.g., 129 The half-life of I is 1.61 × 10⁻⁶. 7 Radioactive iodine (IoDI) can exist in the atmosphere for extended periods as vapor and aerosols. This iodine can be absorbed by the body through inhalation, skin contact, or ingestion, and then accumulate in the thyroid gland over time. This gradual accumulation damages blood vessels and tissues, eventually leading to cancer after a long latency period. Therefore, researchers have been exploring efficient methods for capturing radioactive iodine. Among various methods, solid-state adsorption is widely recognized as one of the most promising technologies due to its simplicity, low maintenance costs, and lack of the need for highly corrosive solutions.

[0003] Porous materials (zeolites, activated carbon, covalent organic frameworks, metal-organic frameworks, etc.) have long been considered the most effective adsorbents for capturing iodine. This is because porous materials have a high surface area, theoretically providing a large number of iodine-binding active sites, thus making them relatively effective in capturing iodine and other radioactive contaminants. However, the preparation process of these porous materials is complex and requires harsh conditions; moreover, these materials are usually in powder form, exhibiting severe agglomeration and making them difficult to recycle. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a polyimide membrane material, its preparation method, and its application in iodine adsorption. The preparation method of this invention is simple and can be completed at room temperature, and the prepared polyimide membrane material possesses both high iodine adsorption capacity and recyclability.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a polyimide film material, comprising the following steps:

[0007] A Schiff base reaction is carried out by mixing a crosslinking agent, a dialdehyde monomer, a diamine monomer, and an aprotic solvent to obtain a polyimide solution; the crosslinking agent includes 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine;

[0008] The polyimide solution is desolventized and a film is formed to obtain the polyimide film material.

[0009] Preferably, the diamine monomer includes one or more of diethylenetriamine, bifenthrinamine, and 4,4'-dithiodiphenylamine.

[0010] Preferably, the dialdehyde monomer includes one or more of terephthalaldehyde, 2,6-pyridinedicarboxaldehyde, and 4-(4-formylphenoxy)-3-methoxybenzaldehyde.

[0011] Preferably, the molar ratio of -NH2 in the crosslinking agent to -NH2 in the diamine monomer is 1:(0.25-4).

[0012] Preferably, the ratio of the total molar amount of -NH2 in the crosslinking agent and diamine monomer to the molar amount of aldehyde group in the dialdehyde monomer is 1:1.

[0013] Preferably, the aprotic solvent includes one or more of N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide.

[0014] Preferably, the Schiff base reaction is carried out at room temperature for 3 to 10 minutes; the Schiff base reaction is carried out under stirring or shaking conditions.

[0015] Preferably, the solvent removal film-forming temperature is 120°C, and the temperature is increased from room temperature to the solvent removal film-forming temperature within 30 minutes.

[0016] This invention provides a polyimide film material prepared by the preparation method described above.

[0017] This invention provides the application of the polyimide membrane material described above in iodine adsorption.

[0018] This invention provides a method for preparing a polyimide membrane material. The method uses 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine as crosslinking agents, reacting them with a diamine monomer and a dialdehyde monomer in an aprotic solvent via a Schiff base reaction to obtain a polyimide solution. The polyimide solution is then formed into a film to obtain the polyimide membrane material. Compared with the prior art, this invention has the following advantages:

[0019] The polymer backbone of the polyimide membrane material prepared by this invention has a large number of imine bonds. These imine bonds can effectively bind iodine atoms through strong interactions comparable to hydrogen bonds. This characteristic ensures the stability of the polyimide material and its high efficiency in iodine adsorption. When the crosslinking agent is 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine, pyridine units are also introduced. Due to their polarization, both pyridine-N and imine-N are electron-rich and act as Lewis bases. Therefore, they can capture iodine (iodine is a Lewis acid) through charge transfer. Thus, the introduction of pyridine units can improve the iodine adsorption capacity of polyimide. In addition, the electron-rich aromatic backbone can also adsorb iodine to a certain extent through electrostatic interactions. Furthermore, the polymer backbone of the polyimide membrane material prepared by this invention has a large number of heteroatoms. The introduction of N heteroatoms, oxygen heteroatoms, and sulfur heteroatoms can all improve the polymer's iodine adsorption capacity to a certain extent. Therefore, the polyimide membrane material prepared by this invention has excellent iodine adsorption capacity and adsorption stability.

[0020] The polyimide membrane material prepared by this invention contains dynamic imide bonds, which can help reshape and restore the broken polyimide membrane material under hot pressing conditions, making the material easy to recycle.

[0021] The membrane-based material prepared by this invention overcomes the tendency to clump compared to powdered iodine adsorbent materials, thus demonstrating good cost-effectiveness and user-friendliness.

[0022] Moreover, the present invention can prepare polyimide simply by reacting at room temperature, which is simple and overcomes the relatively cumbersome disadvantage of traditional iodine adsorption materials (covalent organic frameworks, metal-organic frameworks, porous organic polymers, non-porous adaptive crystals, macrocyclic non-porous amorphous materials).

[0023] Furthermore, when the dialdehyde monomer is 4-(4-formylphenoxy)-3-methoxybenzaldehyde, it is a vanillin derivative, which can further reduce the cost of raw materials and improve the biocompatibility of the polymer.

[0024] The results of the examples show that the iodine adsorption capacity of the polyimide membrane material prepared by the present invention is 1.6-5.73 g / g, and it exhibits excellent adsorption stability. After five cycles of adsorption, the membrane material still retains 94% of the iodine adsorption capacity. After hot pressing at 100℃ and 10MPa pressure for 45 min, the sheared polyimide membrane can completely recover to its initial state. The surface of the reprocessed film is very smooth, without cracks, and has the characteristics of recyclability. The tensile strength of the polyimide membrane material is 11.5-83.2 MPa, and it has excellent mechanical properties. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for preparing polyimide film materials according to an embodiment of the present invention;

[0026] Figure 2 The reaction route diagram for preparing polyimide film material (taking 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine as a crosslinking agent) in an embodiment of the present invention is shown below.

[0027] Figure 3 The Schiff base reaction is a reaction between 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine, diethylenetriamine, and terephthalaldehyde.

[0028] Figure 4 Schiff base reaction of tris(2-aminoethyl)amine, bifenthidine and 4-(4-formylphenoxy)-3-methoxybenzaldehyde;

[0029] Figure 5 Schiff base reaction of tris(2-aminoethyl)amine, 4,4'-dithiodiphenylamine and 2,6-pyridinedicarboxaldehyde;

[0030] Figure 6 Infrared contrast spectra of polyimide film material (PI-40) and raw materials;

[0031] Figure 7 Infrared spectra of polyimide film materials (PI-20 to PI-40);

[0032] Figure 8 The mechanical property test results are for polyimide film materials (PI-20 to PI-40);

[0033] Figure 9 A schematic diagram of hot-pressing reshaping of shattered polyimide film material (PI-24);

[0034] Figure 10 A schematic diagram of the iodine adsorption device (a) and the color change of the polyimide membrane material before and after iodine adsorption (b);

[0035] Figure 11 Bar chart showing the iodine adsorption performance of polyimide membrane materials (PI-20 to PI-36);

[0036] Figure 12 The results show the cyclic iodine adsorption performance of the polyimide membrane material (PI-36).

[0037] Figure 13 Bar chart showing the iodine adsorption performance of polyimide membrane materials (XC-0 to XC-100);

[0038] Figure 14 The bar chart shows the iodine adsorption performance of polyimide membrane materials (SPI-0 to SPI-100). Detailed Implementation

[0039] This invention provides a method for preparing a polyimide film material, comprising the following steps:

[0040] A Schiff base reaction is carried out by mixing a crosslinking agent, a dialdehyde monomer, a diamine monomer, and an aprotic solvent to obtain a polyimide solution; the crosslinking agent includes 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine;

[0041] The polyimide solution is desolventized and a film is formed to obtain the polyimide film material.

[0042] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0043] Figure 1 and Figure 2 The following are schematic diagrams of the process and reaction route for preparing polyimide film materials according to embodiments of the present invention. Figures 1-2 Please provide a detailed explanation.

[0044] This invention involves mixing a crosslinking agent, a dialdehyde monomer, a diamine monomer, and an aprotic solvent to perform a Schiff base reaction, thereby obtaining a polyimide solution (or a polyimide mixed solution).

[0045] In this invention, the crosslinking agent comprises 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine (Py-TAB) and / or tris(2-aminoethyl)amine. In this invention, the structure of the 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine is as shown in Formula I. This invention does not have particular requirements regarding the source of the 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine; it can be obtained from commercially available products or prepared using methods well-known in the art. In this invention, the diamine monomer preferably includes one or more of diethylenetriamine, bifenthrinamine, and 4,4'-dithiodiphenylamine; the dialdehyde monomer preferably includes one or more of terephthalaldehyde, 2,6-pyridinedicarboxaldehyde, and 4-(4-formylphenoxy)-3-methoxybenzaldehyde, the structure of which is shown in Formula II. This invention does not have any particular requirements for the source of the 4-(4-formylphenoxy)-3-methoxybenzaldehyde, which can be prepared using commercially available products or by preparation methods well known in the art.

[0046]

[0047] In this invention, the molar ratio of -NH2 in the crosslinking agent to -NH2 in the diamine monomer is preferably 1:(0.25-4), and can be 1:0.25, 1:0.66, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.1, 1:3.2, 1:3.5, or 1:4; the ratio of the total molar amount of -NH2 in the crosslinking agent and diamine monomer to the molar amount of aldehyde groups in the dialdehyde monomer is preferably 1:1. This invention uses 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine as crosslinking agents. By controlling the feed ratio of bis(3′,4′-diaminophenyl)-4-phenylpyridine to dialdehyde monomer, a Schiff base reaction (polycondensation) can be carried out to prepare polyimides with appropriate crosslinking density and rigid structures, thereby enhancing mechanical properties and iodine adsorption capacity.

[0048] In this invention, the aprotic solvent preferably includes one or more of N,N-dimethylformamide (DMF), N-methylpyrrolidone, and N,N-dimethylacetamide. This invention does not have specific requirements regarding the amount of the aprotic solvent used, as long as it ensures complete dissolution of the raw materials.

[0049] In this invention, the preferred method for mixing the crosslinking agent, dialdehyde monomer, diamine monomer, and aprotic solvent is as follows: dissolving the crosslinking agent and diamine monomer in an aprotic solvent at room temperature to obtain solution one; dissolving the dialdehyde monomer in an aprotic solvent at room temperature to obtain solution two; and adding solution two to solution one under stirring.

[0050] In this invention, the Schiff base reaction is preferably carried out at room temperature and for a time of 3 to 10 minutes, which can be 3, 4, 5, 6, 7, 8, 9 or 10 minutes. The Schiff base reaction time is calculated from the time the second solution is added. The Schiff base reaction is preferably carried out under stirring or shaking conditions.

[0051] In this invention, taking diethylenetriamine as the diamine monomer, terephthalaldehyde as the dialdehyde monomer, and 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine as the crosslinking agent as an example, the reactions involved in the Schiff base reaction are as follows: Figure 3 As shown; taking bifenthionine as the diamine monomer, 4-(4-formylphenoxy)-3-methoxybenzaldehyde as the dialdehyde monomer, and tris(2-aminoethyl)amine as the crosslinking agent as an example, the reactions involved in the Schiff base reaction are as follows: Figure 4 As shown; taking 4,4'-dithiodiphenylamine as the diamine monomer, 2,6-pyridinedicarboxaldehyde as the dialdehyde monomer, and tris(2-aminoethyl)amine as the crosslinking agent as an example, the reactions involved in the Schiff base reaction are as follows: Figure 5 As shown (since the polymer is a random copolymer, therefore...) Figures 3-5 It showcases its most representative structural components.

[0052] This invention allows for the preparation of polyimide at room temperature (with stirring or oscillation), overcoming the relatively cumbersome preparation of traditional iodine adsorbent materials (covalent organic frameworks, metal-organic frameworks, porous organic polymers, non-porous adaptive crystals, macrocyclic non-porous amorphous materials).

[0053] After obtaining the polyimide solution, the present invention removes the solvent from the polyimide solution to form a film, thereby obtaining the polyimide film material.

[0054] In this invention, the solvent removal film-forming temperature is preferably 120°C, and preferably raised from room temperature to the solvent removal film-forming temperature within 30 minutes. During the process of raising the temperature from room temperature to the solvent removal film-forming temperature, the Schiff base reaction proceeds further, and the elimination of bubbles introduced into the solution can be promoted. This invention does not have a particular requirement for the solvent removal film-forming time, as long as the solvent is fully removed. In this embodiment, the solvent removal film-forming time is 4 hours. In this embodiment, the solvent removal film-forming method is used, specifically: the polyimide solution is cast onto a clean glass plate, then heated to 120°C from room temperature within 30 minutes in a muffle furnace, held at that temperature for 4 hours, and the solvent is dried to obtain the polyimide film material.

[0055] The preparation method provided by this invention has a simple and direct synthesis process, and is therefore cost-effective and scalable.

[0056] This invention provides a polyimide membrane material prepared by the method described above. In this invention, the polymer backbone of the polyimide membrane material contains a large number of imine bonds and heteroatoms. These imine bonds, through strong interactions comparable to hydrogen bonds, can very effectively bind iodine atoms. This characteristic ensures the stability of the polyimide material and its high-efficiency iodine adsorption capacity. Simultaneously, when 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine is used as the crosslinking agent, the polyimide membrane material contains pyridine units. Due to their polarization, both pyridine-N and imine-N are electron-rich and act as Lewis bases. Therefore, they can capture iodine (iodine is a Lewis acid) through charge transfer. Thus, the introduction of pyridine units can improve the iodine adsorption capacity of the polyimide. Furthermore, the polyimide membrane material has an electron-rich aromatic backbone, which can also adsorb iodine to a certain extent through electrostatic interactions. The polyimide membrane material provided by this invention combines high iodine adsorption capacity and recyclability, and has excellent mechanical properties, offering cost advantages and user-friendliness.

[0057] This invention provides the application of the polyimide membrane material described in the above technical solution in iodine adsorption. The method of application is not particularly required by this invention; any application method well-known to those skilled in the art can be used. The polyimide membrane material provided by this invention has excellent iodine adsorption capacity and adsorption stability, enabling efficient adsorption of iodine.

[0058] To further illustrate the present invention, the following detailed description, in conjunction with examples, of the polyimide membrane material provided by the present invention, its preparation method, and its application in iodine adsorption, shall not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] At room temperature, 0.2063 g of diethylenetriamine (DETA) and 0.0918 g of 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine (Py-TAB) were added to a single-necked flask equipped with a stirrer and dissolved completely in 8 mL of LDM to obtain solution one. 0.3353 g of 1,4-phthalaldehyde was added to a single-necked flask equipped with a stirrer and dissolved completely in 4 mL of LDM to obtain solution two. Solution two was then added to solution one under stirring for 5 min. The resulting polyimide mixture was then poured onto a clean glass plate and heated to 120 °C over 30 min (to complete degassing). The mixture was then held at 120 °C for 4 h to allow the solvent to evaporate completely, yielding the polyimide film material.

[0061] Examples 2-6

[0062] The preparation method is basically the same as in Example 1, except that the ratio of diethylenetriamine to 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine is different, as shown in Table 1. The solvent (DMF) used in each example is 12 mL. The polyimide membrane materials prepared in Examples 1 to 6 are denoted as PI-X (X = 20, 24, 28, 32, 36, 40, where X represents the molar percentage of -NH2 in the pyridine crosslinking agent, i.e., 2,6-bis(3′,4′-diaminophenyl)-4-phenylpyridine, to the total -NH2 in the crosslinking agent and diethylenetriamine).

[0063] Table 1. Amounts of reaction raw materials used in Examples 1-6

[0064]

[0065]

[0066] The polyimide film material prepared in the examples was characterized by its chemical structure and tested for its performance, as detailed below:

[0067] (I) Chemical Characterization of Polyimide Membrane Materials

[0068] Figure 6 Infrared comparison spectra of polyimide film material (PI-40) and raw materials.

[0069] Figure 7The infrared spectrum of polyimide film materials (PI-20 to PI-40) is shown.

[0070] like Figures 6-7 As shown, polyimide film (PI-X) at 2932 and 2860 cm⁻¹ -1 The peak at 1694 cm⁻¹ shows a methylene stretching vibration caused by diethylenetriamine. Furthermore, the PI-X film exhibits a peak at 1694 cm⁻¹. -1 The characteristic peak of the aldehyde group almost disappeared at 1643 cm⁻¹, while at 1643 cm⁻¹... -1 The presence of a characteristic peak for an imine bond indicates the efficient occurrence of the Schiff base reaction. Simultaneously, due to the transformation of the amino group into an imine bond, a peak appears at 3400 cm⁻¹. -1 The sharp double peaks nearby turned into blunt single peaks. This indicates that PI-X films can be successfully synthesized under extremely mild conditions.

[0071] (II) Mechanical Properties of Polyimide Film Materials

[0072] Figure 8 The mechanical property test results are for polyimide film materials (PI-20 to PI-40). The tensile properties of each polyimide film material are as follows:

[0073] PI-20: 39.3MPa, PI-24: 83.2MPa, PI-28: 55.1MPa, PI-32: 35.1MPa, PI-36: 30.8MPa, PI-40: 11.5MPa.

[0074] Generally, the mechanical properties of copolymers can be adjusted by regulating the proportions of different monomers. For example... Figure 8 As shown, PI-24 film exhibits the best tensile properties. Although the crosslinking density of PI-28, PI-32, PI-36, and PI-40 increases with increasing crosslinking agent content, their tensile properties decrease. This is because when the crosslinking density is too high, the orientation of the molecular chains is severely affected, and the entangled polymer chains have difficulty responding to stress in a timely manner, leading to uneven stress distribution and fracture. Meanwhile, due to its lower crosslinking density, PI-20's tensile properties (39.3 MPa) are lower than those of PI-24 film (83.2 MPa). Furthermore, PI-X films exhibit typical brittle fracture curves, with elongation at break ranging from 0.52% to 2.52%. Changes in crosslinking agent content have little effect on the elongation at break of PI-X films. This may be due to the inherent rigidity of PI-X films, making the introduction of a small amount of rigid structure insufficient to significantly affect their elongation at break.

[0075] (III) Recyclability Testing of Polyimide Membrane Materials

[0076] The fragmented polyimide film material (PI-24) is reshaped by hot pressing, such as... Figure 9 As shown, after hot pressing at 100℃ and 10MPa for 45 minutes, the sheared PI-24 film can completely recover to its initial state. The surface of the reprocessed film is very smooth and free of cracks.

[0077] (iv) Iodine adsorption capacity test of polyimide membrane material

[0078] Because the prepared polyimide film has excellent mechanical properties, iodine adsorption was studied to broaden its application potential.

[0079] Test method: The prepared polyimide membrane material was subjected to an adsorption test of gaseous iodine. Specifically, approximately 15 mg of the prepared polyimide membrane material (mass denoted as W1) and excess iodine were placed in a sealed glass bottle (50 mL), heated at 333 K, and after the membrane was saturated (mass no longer changed), the mass was weighed and recorded as W2. Then, the amount of iodine adsorbed was calculated using the following formula 1 to determine its iodine adsorption capacity:

[0080] Iodine adsorption capacity = (W2-W1) / W1 (Formula 1)

[0081] Figure 10 A schematic diagram of the iodine adsorption device (a) and the color change of the polyimide membrane material before and after iodine adsorption (b) are shown. The pyridine unit was introduced to enhance the iodine adsorption capacity of the PI-X film. Due to their polarization, both pyridine-N and imine-N are electron-rich and behave as Lewis bases. Therefore, they can capture I2 (a Lewis acid) through charge transfer. Similar to most iodine adsorption materials, the color of the PI-X film changes from orange-red to purplish-black as adsorption proceeds. Figure 10 (b)

[0082] Figure 11 The bar chart shows the iodine adsorption performance of polyimide membrane materials (PI-20 to PI-36). The iodine adsorption capacities of each polyimide membrane material are: PI-20: 1.6 g / g, PI-24: 2.13 g / g, PI-28: 2.87 g / g, PI-32: 3.48 g / g, and PI-36: 4.07 g / g. The iodine adsorption capacity of the PI-X films (PI-20 to PI-36) ranges from 1.6 to 4.07 g / g, increasing with increasing crosslinking agent content. However, the high iodine adsorption capacity causes the PI-40 film to lose its natural shape and adhere to the inner wall of the absorber device; therefore, it is impossible to collect iodine adsorption data for the PI-40 film.

[0083] The cyclic iodine adsorption performance of polyimide membrane material (PI-36) was tested. During the cycle, the PI-36 membrane with adsorbed iodine was ultrasonically treated in DMF, and the adsorbed iodine was dissociated. Iodine adsorption continued thereafter. Figure 12The results show the cyclic iodine adsorption performance of polyimide membrane material PI-36. PI-36 exhibits excellent adsorption stability; after five cycles of adsorption, the PI-36 film still retains 94% of its iodine adsorption capacity (3.83 g / g).

[0084] Examples 7-12

[0085] At room temperature, tris(2-aminoethyl)amine (TREN) and bifenthidine amine were added to a single-necked flask equipped with a stirrer and dissolved completely in 8 mL of DMF to obtain solution one. 4-(4-formylphenoxy)-3-methoxybenzaldehyde was added to the same single-necked flask and dissolved completely in 4 mL of DMF to obtain solution two. Solution two was then added to solution one under stirring for 5 minutes. The resulting polyimide mixture was then poured onto a clean glass plate and heated to 120°C over 30 minutes (to complete degassing). The mixture was then held at 120°C for 4 hours to allow the solvent to evaporate completely, yielding the polyimide film material. The amounts of tris(2-aminoethyl)amine, bifenthidine, and 4-(4-formylphenoxy)-3-methoxybenzaldehyde used in Examples 7-12 are shown in Table 2. The polyimide film materials prepared in Examples 7-12 are denoted as XC-X (X = 0, 20, 40, 60, 80, 100, where X represents the molar percentage of -NH2 in the crosslinking agent, i.e., tris(2-aminoethyl)amine, to the total -NH2 in the crosslinking agent and bifenthidine).

[0086] Table 2 shows the amounts of reaction raw materials used in Examples 7-12.

[0087]

[0088] The iodine adsorption capacity of the polyimide membrane materials prepared in Examples 7 to 12 was tested using the same method as described in "(IV) Iodine Adsorption Capacity Test of Polyimide Membrane Materials" above. Figure 13 The bar chart shows the iodine adsorption performance of polyimide membrane materials (XC-0 to XC-100). The iodine adsorption capacity of each polyimide membrane material in Examples 7 to 12 is as follows: XC-0: 0.2 g / g, XC-20: 3.72 g / g, XC-40: 4.63 g / g, XC-60: 5.73 g / g, XC-80: 5.25 g / g, XC-100: 4.67 g / g, among which XC-60 has the best iodine adsorption capacity.

[0089] Examples 13-18

[0090] At room temperature, tris(2-aminoethyl)amine (TREN) and 4,4'-dithiodiphenylamine were added to a single-necked flask equipped with a stirrer and dissolved completely in 8 mL of DMF to obtain solution one. 2,6-pyridinedicarboxaldehyde was added to the same single-necked flask and dissolved completely in 4 mL of DMF to obtain solution two. Solution two was then added to solution one under stirring for 5 minutes. The resulting polyimide mixture was then poured onto a clean glass plate and heated to 120°C over 30 minutes (to complete degassing). The mixture was then held at 120°C for 4 hours to allow the solvent to evaporate completely, yielding the polyimide film material. The amounts of tris(2-aminoethyl)amine, 4,4'-dithiodiphenylamine, and 2,6-pyridinedicarboxaldehyde used in Examples 13-18 are shown in Table 3. The polyimide film materials prepared in Examples 13-18 are denoted as SPI-X (X = 0, 20, 40, 60, 80, 100, where X represents the molar percentage of -NH2 in the crosslinking agent, i.e., tris(2-aminoethyl)amine, to the total -NH2 in the crosslinking agent and 4,4'-dithiodiphenylamine).

[0091] Table 3 shows the amounts of reaction materials used in Examples 13-18.

[0092] Example Tris(2-aminoethyl)amine (g) 4,4'-Dithiodiphenylamine (g) 2,6-Pyridinedicarboxaldehyde (g) Example 13 (SPI-0) 0 0.1863 0.1013 Example 14 (SPI-20) 0.0146 0.1490 0.1013 Example 15 (SPI-40) 0.0292 0.1118 0.1013 Example 16 (SPI-60) 0.0439 0.0745 0.1013 Example 17 (SPI-80) 0.0585 0.0373 0.1013 Example 18 (SPI-100) 0.0731 0 0.1013

[0093] The iodine adsorption capacity of the polyimide membrane materials prepared in Examples 13-18 was tested, and the test method was the same as that in "(IV) Iodine Adsorption Capacity Test of Polyimide Membrane Materials" above. Figure 14 The bar chart shows the iodine adsorption performance of polyimide membrane materials (SPI-0 to SPI-100). The iodine adsorption capacity of each polyimide membrane material in Test Examples 13 to 18 is as follows: SPI-0: 1.55 g / g, SPI-20: 3.48 g / g, SPI-40: 3.81 g / g, SPI-60: 4.21 g / g, SPI-80: 4.53 g / g, and SPI-100: 3.10 g / g. Among them, SPI-80 has the best iodine adsorption capacity.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Use of a polyimine film material in iodine adsorption, a preparation method of the polyimine film material comprising the following steps: mixing a crosslinking agent, a dialdehyde monomer, a diamine monomer and an aprotic solvent to perform a Schiff base reaction to obtain a polyimine solution; the crosslinking agent comprises 2,6-bis(3',4'-diaminophenyl)-4-phenylpyridine and / or tris(2-aminoethyl)amine; removing solvent from the polyimine solution to form a film to obtain the polyimine film material.

2. Use according to claim 1, characterized in that, The diamine monomer comprises one or more of diethylenetriamine, bisanisidine and 4,4'-dithiodianiline.

3. Use according to claim 1, characterized in that, The dialdehyde monomer comprises one or more of terephthaldehyde, 2,6-pyridine dicarboxaldehyde and 4-(4-formylphenoxy)-3-methoxybenzaldehyde.

4. The use according to any one of claims 1 to 3, characterized in that, The molar ratio of -NH2 in the crosslinking agent to -NH2 in the diamine monomer is 1:(0.25-4).

5. Use according to claim 4, characterized in that, The ratio of the total molar amount of -NH2 in the crosslinking agent and the diamine monomer to the molar amount of aldehyde groups in the dialdehyde monomer is 1:

1.

6. Use according to claim 1, characterized in that, The aprotic solvent comprises one or more of N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylacetamide.

7. The use according to claim 1, characterized in that, The temperature of the Schiff base reaction is room temperature, and the time is 3-10 min; the Schiff base reaction is performed under stirring or oscillation.

8. The use according to claim 1, characterized in that, The temperature of removing solvent to form a film is 120°C, and the temperature is raised from room temperature to the temperature of removing solvent to form a film within 30 min.

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