Polyimide photocatalytic fiber and preparation method and application thereof

Abstract

The application provides a polyimide photocatalytic fiber and a preparation method and application thereof, and the polyimide photocatalytic fiber comprises a polyimide fiber and photocatalytic polyimide loaded on the surface of the polyimide fiber; in the application, the photocatalytic polyimide is loaded on the surface of the polyimide fiber, the problem that the polyimide fiber does not have photocatalytic function is solved, the affinity between the two is high, and problems such as peeling and falling of the photocatalytic material do not occur; the stability and durability of the photocatalytic fiber are improved; under the premise that the mechanical properties of the fiber are not affected, the photocatalytic fiber has excellent photocatalytic effect and high degradation efficiency on photodegradable compounds, such as rhodamine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic fiber materials, and particularly relates to a polyimide photocatalytic fiber and a preparation method and application thereof. BACKGROUND

[0002] Photocatalysis technology is a technology for realizing catalytic reaction by using light energy to excite catalyst to produce active species. Fiber materials have wide application prospects as an important functional material. Polyimide is a high polymer material with excellent performance and is commonly used for preparing fiber materials. A conventional method for preparing polyimide fiber is to obtain polyimide fiber by spinning and imidization treatment of polyamic acid (PAA, generally synthesized by using pyromellitic dianhydride PMDA and oxydianiline ODA), but the obtained polyimide fiber cannot realize photocatalysis effect.

[0003] In the prior art, a method for obtaining polyimide photocatalytic fiber is generally to load photocatalytic particles onto polyimide fiber to realize photocatalytic properties of the fiber by using photocatalytic properties of the photocatalytic particles. Common photocatalytic particles include TiO2, ZnO and the like. However, in the process of loading particles, the fiber often needs to be treated to realize effective combination of the particles and the fiber, which reduces the strength of the fiber and affects subsequent use. In the process of loading treatment, the nanoparticles may be coated by the polyimide material, which may not realize photocatalytic effect and reduces photocatalytic efficiency. Meanwhile, the photocatalytic particles also have the risk of falling off in the process of use.

[0004] Therefore, it is an urgent problem to be solved in the field to develop a polyimide photocatalytic fiber with excellent photocatalytic effect, high loading firmness and no falling off, which does not affect the strength of the fiber. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a polyimide photocatalytic fiber and a preparation method and application thereof. The photocatalytic fiber is used for photocatalytic degradation of rhodamine, has excellent photocatalytic effect, high degradation efficiency, high loading firmness and no risk of material falling off, and avoids the influence of photocatalytic particles on the mechanical properties of the fiber.

[0006] To achieve the purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a polyimide photocatalytic fiber, which comprises a polyimide fiber and photocatalytic polyimide loaded on the surface of the polyimide fiber.

[0008] In the present application, by loading the photocatalytic polyimide onto the surface of the polyimide fiber, both the problem that the polyimide fiber does not have photocatalytic function and the problem that the photocatalytic polyimide cannot be spun are solved, and the affinity between the two is high, and problems such as peeling, falling off, and separation of the photocatalytic material do not occur; the stability and durability of the photocatalytic fiber are improved; under the premise of ensuring that the mechanical properties of the fiber are not affected, the photocatalytic fiber has excellent photocatalytic effect, and the degradation efficiency of the photocatalytic fiber on light-degradable compounds such as rhodamine is high.

[0009] Preferably, the mass ratio of the photocatalytic polyimide to the polyimide fiber is (0.03-0.2):1, wherein the specific value in (0.03-0.2) can be, for example, 0.03, 0.035, 0.04, 0.045, 0.048, 0.05, 0.052, 0.055, 0.056, 0.058, 0.06, 0.062, 0.064, 0.066, 0.068, 0.07, 0.072, 0.074, 0.078, 0.08, 0.082, 0.085, 0.088, 0.09, 0.092, 0.095, 0.098, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, etc.; preferably (0.05-0.08):1.

[0010] In the present application, the mass ratio of the photocatalytic polyimide to the polyimide fiber is within the range defined above, and the photocatalytic degradation effect is more optimal; less than 0.03:1, the photocatalytic effect is poor; greater than 0.2:1, the fiber surface is loaded with too much photocatalytic polyimide, which can cause the fiber diameter to be too thick, reducing the surface area per unit weight of the material, and the reduction of the surface area can seriously reduce the photocatalytic performance of the material. Excessive loading can cause the fiber surface structure to be loose and easy to fall off.

[0011] Preferably, the photocatalytic polyimide is a sheet photocatalytic polyimide.

[0012] In the present application, the sheet photocatalytic polyimide is used, and compared with the traditional particulate photocatalyst, the special morphology photocatalyst has a larger specific surface area and a longer photo-generated carrier migration path, thereby providing more reactive sites and higher photo-generated electron-hole separation efficiency. Therefore, compared with ordinary spherical polyimide, the sheet or sheet layer of polyimide loaded on the fiber will bring better photocatalytic effect.

[0013] Preferably, the polyimide photocatalytic fiber has a skin-core structure, the polyimide fiber is the core layer; and the photocatalytic polyimide is the skin layer, which is loaded on the outer surface of the polyimide fiber.

[0014] Preferably, the raw material for preparing the photocatalytic polyimide comprises a dianhydride having a conjugated structure and a diamine having a conjugated structure.

[0015] Preferably, the dianhydride comprises at least one of pyromellitic dianhydride, biphenyl dianhydride, naphthalene tetracarboxylic dianhydride, or perylene tetracarboxylic dianhydride.

[0016] Preferably, the diamine comprises at least one of phenylenediamine, p-phenylenediamine, naphthalene diamine, biphenyl diamine, binaphthyl diamine, diaminofluorene, diaminophenanthrene, diaminanthraquinone, diaminopyridine, methyl guanidine, melamine, or miller amine.

[0017] In a second aspect, the present application provides a method for preparing the polyimide photocatalytic fiber according to the first aspect, the method comprising:

[0018] loading the photocatalytic polyimide on the surface of the polyimide fiber to obtain the polyimide photocatalytic fiber.

[0019] Preferably, the loading method comprises: soaking the polyimide fiber in a photocatalytic polyimide precursor, and after heat treatment, obtaining the polyimide photocatalytic fiber.

[0020] Preferably, the photocatalytic polyimide precursor is a photocatalytic polyamic acid.

[0021] Preferably, the mass concentration of the photocatalytic polyamic acid is 5-20%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.; further preferably, it is 5-10%.

[0022] Preferably, the method for preparing the photocatalytic polyamic acid comprises: mixing a dianhydride having a conjugated structure and a diamine having a conjugated structure with a solvent to obtain the polyamic acid.

[0023] In the present application, the solvent includes but is not limited to N,N-dimethylformamide (DMF), N-methyl pyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or ethanol, etc.

[0024] In the present application, the mixing can be stopped when the system viscosity is unchanged.

[0025] Preferably, the soaking further comprises a drying step.

[0026] Preferably, the drying temperature is 60-130℃, for example, it can be 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, etc.; further preferably, it is 100-125℃.

[0027] Preferably, the heat treatment comprises heat treatment with gradient temperature rising and holding.

[0028] Preferably, the heat treatment comprises heat treatment with first temperature rising and holding, second temperature rising and holding and third temperature rising and holding.

[0029] Preferably, the first temperature rising and holding is raised to 100-150℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 122℃, 125℃, 128℃, 130℃, 132℃, 135℃, 138℃, 140℃, 142℃, 145℃, 148℃, 150℃, etc.; and held for 0.5-2h, for example, it can be 0.5h, 0.6h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, etc.

[0030] Preferably, the second temperature rising and holding is raised to 200-230℃, for example, it can be 200℃, 202℃, 205℃, 208℃, 210℃, 212℃, 215℃, 218℃, 220℃, 222℃, 225℃, 228℃, 230℃, etc.; and held for 30-60min, for example, it can be 30min, 32min, 35min, 38min, 40min, 42min, 45min, 48min, 50min, 52min, 55min, 58min, 60min, etc.

[0031] Preferably, the third temperature rising and holding is raised to 250-320℃, for example, it can be 250℃, 255℃, 260℃, 265℃, 270℃, 272℃, 275℃, 278℃, 280℃, 282℃, 285℃, 288℃, 290℃, 295℃, 300℃, 305℃, 310℃, 315℃, 320℃, etc.; and held for 0.5-3h, for example, it can be 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.5h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, etc.

[0032] Preferably, the temperature rising rate of the first temperature rising and holding, the second temperature rising and holding and the third temperature rising and holding is independently 3-8℃ / min, for example, it can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, etc.

[0033] Preferably, the heat treatment comprises: heating from room temperature to 125-135 DEG C, holding for 0.8-1.2 h, then heating to 205-215 DEG C, holding for 35-45 min, and then heating to 275-285 DEG C, holding for 1.5-2.5 h.

[0034] In the present application, the heat treatment adopts a specific process, and the loading efficiency of the photocatalytic polyamide is high, so that the photocatalytic efficiency of the polyimide photocatalytic fiber can be ensured.

[0035] In a third aspect, the present application provides a use of the polyimide photocatalytic fiber according to the first aspect in a photocatalytic degradation reaction.

[0036] Preferably, the photocatalytic degradation reaction comprises photocatalytic degradation of rhodamine.

[0037] The numerical range in the present application includes not only the point values listed above, but also any point values between the above numerical ranges which are not listed, and the present application does not list the specific point values included in the range for the sake of brevity and simplicity.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] The polyimide photocatalytic fiber provided by the present application can obtain a polyimide photocatalytic fiber with excellent photocatalytic effect by loading polyimide with photocatalytic properties on the surface of the polyimide fiber, solves the problem that the traditional polyimide fiber cannot achieve photocatalytic effect, and the polyimide photocatalytic fiber provided by the present application can also have good photocatalytic effect without affecting the mechanical properties of the polyimide fiber; the photocatalytic polyimide can be firmly loaded on the polyimide fiber, avoiding problems such as peeling, falling off and delamination, and ensuring the stability and durability of the fiber; compared with the traditional polyimide fiber, the polyimide photocatalytic fiber has a broader application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a scanning electron microscope image of the polyimide fiber in Example 3 of the present application.

[0041] Figure 2 It is a scanning electron microscope image of the polyimide photocatalytic fiber provided in Example 3 of the present application. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as a specific limitation on the present application.

[0043] Example 1

[0044] The embodiment provides a polyimide photocatalytic fiber, which comprises a polyimide fiber (P84 fiber of Lenzing AG in Austria) and a sheet photocatalytic polyimide loaded on the surface of the polyimide fiber (raw materials comprising naphthalene tetracarboxylic anhydride and phenylenediamine in a molar ratio of 1:1); and the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber is 0.2:1.

[0045] The embodiment provides a preparation method of the polyimide photocatalytic fiber, and specifically comprises the following steps.

[0046] (1) 2.18 g (20 mmol) of phenylenediamine is dissolved in DMF under nitrogen protection, then 5.36 g (20 mmol) of naphthalene tetracarboxylic anhydride is added, and the system is stirred at room temperature until the viscosity is constant, to obtain a photocatalytic polyamic acid (PAA) solution with a concentration of 20%;

[0047] (2) The polyimide fiber is immersed in the PAA solution obtained in the step (1), and after the polyimide fiber is completely immersed, it is taken out and dried at 120 DEG C in a drying oven until no obvious solution is left; then gradient temperature rising and heat preservation treatment are carried out, the heat treatment process comprises the following steps: all the temperature rising rates are kept at 5 DEG C / min, the temperature is raised from room temperature to 150 DEG C, the temperature is kept constant for 0.5 h, the temperature is raised to 200 DEG C, the temperature is kept constant for 1 h, the temperature is continuously raised to 320 DEG C, and the temperature is kept constant for 0.5 h for heat treatment, and then the temperature is cooled, to obtain the polyimide photocatalytic fiber.

[0048] Embodiment 2

[0049] The embodiment provides a polyimide photocatalytic fiber, which comprises a polyimide fiber (P84 fiber of Lenzing AG in Austria) and a sheet photocatalytic polyimide loaded on the surface of the polyimide fiber (raw materials comprising naphthalene tetracarboxylic anhydride and phenylenediamine in a molar ratio of 1:1); and the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber is 0.2:1.

[0050] The embodiment provides a preparation method of the polyimide photocatalytic fiber, and specifically comprises the following steps.

[0051] (1) 2.18 g (20 mmol) of phenylenediamine is dissolved in DMF under nitrogen protection, then 5.36 g (20 mmol) of naphthalene tetracarboxylic anhydride is added, and the system is stirred at room temperature until the viscosity is constant, to obtain a photocatalytic polyamic acid (PAA) solution with a concentration of 20%;

[0052] (2) The polyimide fiber is immersed in the PAA solution obtained in step (1), and after the polyimide fiber is completely infiltrated, it is taken out and dried in a drying oven at 130°C until there is no obvious solution; then it is subjected to gradient temperature holding heat treatment, and the heat treatment process comprises: all the heating rates are kept at 5°C / min, from room temperature to 100°C, constant temperature for 2h, then to 230°C, constant temperature for 0.5h, continue to heat to 250°C, constant temperature for 3h, and then cool down, to obtain the polyimide photocatalytic fiber.

[0053] Example 3

[0054] The polyimide photocatalytic fiber provided in the embodiment comprises a polyimide fiber (Changchun Gaoqi Yilun polyimide fiber) and a lamellar photocatalytic polyimide loaded on the surface thereof (raw materials include 1:1 molar ratio of pyromellitic dianhydride and p-phenylenediamine); the mass ratio of the lamellar photocatalytic polyimide to the polyimide fiber is 0.06:1.

[0055] The embodiment provides a preparation method of the polyimide photocatalytic fiber, and specifically comprises the following steps:

[0056] (1) 1.08g (10mmol) of p-phenylenediamine is dissolved in ethanol under nitrogen protection, then 2.18g (10mmol) of pyromellitic dianhydride is added thereto, and the system is stirred at room temperature until the viscosity is constant to obtain a photocatalytic polyamic acid (PAA) solution with a concentration of 7%;

[0057] (2) The polyimide fiber is immersed in the PAA solution obtained in step (1), and after the polyimide fiber is completely infiltrated, it is taken out and dried in a drying oven at 60°C until there is no obvious solution; then it is subjected to gradient temperature holding heat treatment, and the heat treatment process comprises: all the heating rates are kept at 5°C / min, from room temperature to 130°C, constant temperature for 1h, then to 210°C, constant temperature for 40min, continue to heat to 280°C, constant temperature for 2h, and then cool down, to obtain the polyimide photocatalytic fiber.

[0058] The morphology of the polyimide fiber and the polyimide photocatalytic fiber in Example 3 is characterized by a scanning electron microscope, and the results are shown in Figure 1 (polyimide fiber), Figure 2 (polyimide photocatalytic fiber), Figure 1 and Figure 2 It can be known that the lamellar photocatalytic polyimide is loaded on the surface of the polyimide fiber.

[0059] Example 4

[0060] The embodiment provides a polyimide photocatalytic fiber, which is different from the embodiment 3 only in that the content of the sheet photocatalytic polyimide is increased, so that the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber (Aoshenjianlon polyimide fiber) is 0.08:1; in the preparation method, the heat treatment process comprises the following steps: all the temperature increasing rates are kept as 5 ℃ / min, the temperature is increased from room temperature to 120 ℃, the temperature is kept constant for 1.2 h, the temperature is increased to 215 ℃, the temperature is kept constant for 45 min, the temperature is continuously increased to 285 ℃, and the temperature is kept constant for heat treatment for 1.5 h, and the other raw materials, the dosages and the preparation method are the same as those in the embodiment 3.

[0061] Embodiment 5

[0062] The embodiment provides a polyimide photocatalytic fiber, which is different from the embodiment 3 only in that the content of the sheet photocatalytic polyimide is increased, so that the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber (Aoshenjianlon polyimide fiber) is 0.08:1; in the preparation method, the heat treatment process comprises the following steps: all the temperature increasing rates are kept as 5 ℃ / min, the temperature is increased from room temperature to 120 ℃, the temperature is kept constant for 1.2 h, the temperature is increased to 215 ℃, the temperature is kept constant for 45 min, the temperature is continuously increased to 285 ℃, and the temperature is kept constant for heat treatment for 1.5 h, and the other raw materials, the dosages and the preparation method are the same as those in the embodiment 3.

[0063] Embodiment 6

[0064] The embodiment provides a polyimide photocatalytic fiber, which is different from the embodiment 3 only in that the content of the sheet photocatalytic polyimide is increased, so that the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber (Aoshenjianlon polyimide fiber) is 0.08:1; in the preparation method, the heat treatment process comprises the following steps: all the temperature increasing rates are kept as 5 ℃ / min, the temperature is increased from room temperature to 120 ℃, the temperature is kept constant for 1.2 h, the temperature is increased to 215 ℃, the temperature is kept constant for 45 min, the temperature is continuously increased to 285 ℃, and the temperature is kept constant for heat treatment for 1.5 h, and the other raw materials, the dosages and the preparation method are the same as those in the embodiment 3.

[0065] Embodiment 7

[0066] The embodiment provides a polyimide photocatalytic fiber, which is different from the embodiment 3 only in that the content of the sheet photocatalytic polyimide is increased, so that the mass ratio of the sheet photocatalytic polyimide to the polyimide fiber (Aoshenjianlon polyimide fiber) is 0.08:1; in the preparation method, the heat treatment process comprises the following steps: all the temperature increasing rates are kept as 5 ℃ / min, the temperature is increased from room temperature to 120 ℃, the temperature is kept constant for 1.2 h, the temperature is increased to 215 ℃, the temperature is kept constant for 45 min, the temperature is continuously increased to 285 ℃, and the temperature is kept constant for heat treatment for 1.5 h, and the other raw materials, the dosages and the preparation method are the same as those in the embodiment 3.

[0067] Comparative Example 1

[0068] The comparative example provides a polyimide photocatalytic fiber, which is different from the embodiment 3 only in that sheet photocatalytic polyimide is replaced by an equal amount of titanium dioxide particles, and the specific preparation method can refer to the method disclosed in the embodiment 1 in the document CN 106824294A, and the other raw materials and the dosages are the same as those in the embodiment 3.

[0069] Performance test

[0070] (1) Test of photocatalytic effect

[0071] Take 5 g of the polyimide photocatalytic fiber provided in Examples 1-7, respectively, and take pure polyimide fiber without treatment as a control group, and place them in 100 mL of a 4 mg / L rhodamine B (RhB) solution, stir in the dark environment for 1 h to reach adsorption equilibrium of RhB, and then irradiate under a 300 W xenon lamp for 2 h of photocatalytic degradation of RhB. Take the supernatant every 0.5 h, and use a UV-visible spectrophotometer to measure the absorbance at 554 nm, calculate the residual rate of RhB in the solution, and then investigate the visible light catalytic activity of the sample; the smaller the residual rate in the same time, the better the photocatalytic effect. The test results are shown in Table 1. Before the light irradiation starts, the fibers will automatically adsorb some dye molecules, so the initial amount of dye in the liquid is not 100%.

[0072] (2) Test of loading fastness:

[0073] Take 5 g of the polyimide photocatalytic fiber provided in Examples 1, 3, and Comparative Example 1, respectively, and place them in a water washing color fastness test device, add deionized water, and perform mechanical stirring at 40℃ for 30 min, then rinse with deionized water and dry at room temperature to obtain fastness test samples;

[0074] Then place the above treated polyimide photocatalytic fiber (after treatment) and 5 g of the same fiber without washing treatment (before treatment) in 100 mL of a 4 mg / L rhodamine B (RhB) solution, stir in the dark environment for 1 h to reach adsorption equilibrium of RhB, and then irradiate under a 300 W xenon lamp for 2 h of photocatalytic degradation of RhB. Take the supernatant every 0.5 h, and use a UV-visible spectrophotometer to measure the absorbance at 554 nm, calculate the residual rate of RhB, and then investigate the photocatalytic activity of the fiber after the fastness test of the sample, so as to judge the fastness level of the photocatalytic polyimide loaded on the fiber. The specific test results are shown in Table 2:

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] As can be seen from Tables 1 and 2, the polyimide photocatalytic fiber provided in the present application, by loading sheet-shaped polyimide with photocatalytic properties on the surface of the polyimide fiber, and with a loading amount within a specific range and using a specific heat treatment process, can have good photocatalytic effect without affecting the mechanical properties of the polyimide fiber; and the photocatalytic polyimide can be firmly loaded on the polyimide fiber, avoiding problems such as peeling and falling off, and ensuring the stability and durability of the fiber.

[0080] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the present application.

Claims

1. A polyimide photocatalytic fiber, characterized by, The polyimide photocatalytic fiber comprises a polyimide fiber and a photocatalytic polyimide loaded on the surface of the polyimide fiber. The mass ratio of the photocatalytic polyimide to the polyimide fiber is (0.05-0.08):

1. The photocatalytic polyimide is a sheet photocatalytic polyimide. The polyimide photocatalytic fiber is prepared by the following method, which comprises the following steps: The photocatalytic polyimide is loaded on the surface of the polyimide fiber, and the loading method comprises the following steps: the polyimide fiber is soaked in a photocatalytic polyimide precursor, and after heat treatment, the polyimide photocatalytic fiber is obtained. The photocatalytic polyimide precursor is photocatalytic polyamide acid. The heat treatment comprises gradient heat treatment. The heat treatment comprises the following steps: first heat treatment at 100-150℃ for 0.5-2h, second heat treatment at 200-230℃ for 30-60min, and third heat treatment at 250-320℃ for 0.5-3h. The heating rate of the first heat treatment, the second heat treatment and the third heat treatment is independently 3-8℃ / min.

2. The polyimide photocatalytic fiber of claim 1, wherein, The polyimide photocatalytic fiber has a skin-core structure, the polyimide fiber is the core layer, and the photocatalytic polyimide is the skin layer and is loaded on the outer surface of the polyimide fiber.

3. The polyimide photocatalytic fiber of claim 1, wherein The raw materials for preparing the photocatalytic polyimide comprise a diacid anhydride with a conjugated structure and a diamine with a conjugated structure.

4. The polyimide photocatalytic fiber according to claim 3, characterized by, The diacid anhydride comprises at least one of the following: pyromellitic dianhydride, biphenyl dianhydride, naphthalene tetracarboxylic dianhydride or perylene tetracarboxylic dianhydride.

5. The polyimide photocatalytic fiber according to claim 3, characterized by, The diamine comprises at least one of the following: phenylenediamine, p-phenylenediamine, naphthalene diamine, biphenyl diamine, binaphthyl diamine, diaminofluorene, diaminophenanthrene, diaminium anthraquinone, diaminopyridine, methyl guanamine, melamine or miller amine.

6. A method for preparing the polyimide photocatalytic fiber according to any one of claims 1 to 5, characterized by, The preparation method comprises the following steps: The photocatalytic polyimide is loaded on the surface of the polyimide fiber to obtain the polyimide photocatalytic fiber; The loading method comprises the following steps: the polyimide fiber is soaked in a photocatalytic polyimide precursor, and after heat treatment, the polyimide photocatalytic fiber is obtained. The photocatalytic polyimide precursor is photocatalytic polyamide acid. The heat treatment comprises gradient heat treatment. The heat treatment comprises the following steps: first heat treatment, second heat treatment and third heat treatment. The first heat treatment is at 100-150℃ for 0.5-2h. The second heat treatment is at 200-230℃ for 30-60min. The third heat treatment is at 250-320℃ for 0.5-3h. The heating rate of the first heat treatment, the second heat treatment and the third heat treatment is independently 3-8℃ / min.

7. The production method according to claim 6, wherein The mass concentration of the photocatalytic polyamide acid is 5-20%.

8. The production method according to claim 7, characterized by, The mass concentration of the photocatalytic polyamide acid is 5-10%.

9. The preparation method according to claim 6, characterized in that, The preparation method of the photocatalytic polyamide acid comprises mixing a diacid anhydride with a conjugated structure and a diamine with a conjugated structure with a solvent to obtain the polyamide acid.

10. The method of claim 6, wherein, After the soaking, a drying step is further included.

11. The method of claim 10, wherein, The temperature of the drying is 60-130 DEG C.

12. The method of claim 11, wherein, The temperature of the drying is 100-125 DEG C.

13. The preparation method according to claim 6, characterized in that, The heat treatment comprises: heating from room temperature to 125-135 DEG C, keeping for 0.8-1.2 h, then heating to 205-215 DEG C, keeping for 35-45 min, and then heating to 275-285 DEG C, keeping for 1.5-2.5 h.

14. Application of the polyimide photocatalytic fiber according to any one of claims 1-5 in a photocatalytic degradation reaction.

15. Use according to claim 14, characterized in that, The photocatalytic degradation reaction comprises photocatalytic degradation of rhodamine.

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