Preparation method of transparent polyimide powder

Abstract

The invention relates to a preparation method of transparent polyimide powder, a flask and a suction filtration device are included, the suction filtration device comprises an insertion frame, a stirring unit, a rotary lifting unit and a suction filtration unit, the detachable insertion frame is arranged at the upper end of the interior of the flask, the middle of the insertion frame is of a hollow structure, and an annular cavity is formed in the insertion frame; a stirring unit is installed in the middle of the inserting frame, a rotary lifting unit is installed at the lower end of the inserting frame, suction filtration units are evenly installed on the rotary lifting unit, and the upper ends of the suction filtration units are movably arranged in the annular cavity.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to a method for preparing transparent polyimide powder. Background Art

[0002] Polyimide material is a special polymer material that is resistant to high and low temperatures, flame retardant, and dimensionally stable. Due to its excellent performance, it is widely used in communication electronics, aerospace, rail transportation and other fields, especially in defense equipment, electronic and electrical fields for wave-transmitting, dielectric, high and low temperature resistant and other functional products. Polyimide resin and composite materials can be used as wave-transmitting antenna materials, low dielectric conductive materials, 5G communication materials, etc.

[0003] At present, the methods for preparing polyimide particles mainly include dispersion polymerization, emulsion polymerization, solution polymerization, ultrasonic precipitation, reprecipitation, water precipitation, precipitation-crushing-sorting, etc. Some of these methods have complicated reaction processes, some require a large amount of solvents or dispersants, and some have low yields. In addition, the polyimide particles prepared by these methods have a wide particle size distribution problem. In addition, the traditional method for preparing polyimide powder often cannot completely elute the imidization agent, which will cause the transparent polyimide powder to be impure in color and is not suitable for the preparation of transparent polyimide film. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The present invention provides a method for preparing a transparent polyimide powder which can solve the above-mentioned technical problems.

[0006] (II) Technical solution

[0007] In view of the problems raised by the above background technology, the purpose of the present invention is to provide a method for preparing transparent polyimide powder. To achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing transparent polyimide powder comprises the following steps:

[0009] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), an aromatic diamine compound having a fluorine group, were added to a flask and stirred to dissolve TFMB in DMAC;

[0010] (2) Continue to add 12 g of triethylamine and 190 g to 400 g of a poor solvent into the flask and stir thoroughly for 1 hour to make the solution fully uniform;

[0011] (3) while stirring the flask, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0012] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0013] (5) extracting the contents of the detachable flask by using a suction filtration device, washing the contents with a methanol solution, and filtering to obtain a transparent polyimide powder;

[0014] The above-mentioned filtration device includes a plug-in rack, a stirring unit, a rotating lifting unit and a filtration unit. A detachable plug-in rack is arranged at the upper end of the interior of the flask. The middle part of the plug-in rack is a hollow structure. An annular cavity is arranged inside the plug-in rack. A stirring unit is installed in the middle part of the plug-in rack. A rotating lifting unit is installed at the lower end of the plug-in rack. The filtration units are evenly installed on the rotating lifting unit. The upper end of the filtration unit is movably arranged inside the annular cavity.

[0015] Preferably, the poor solvent is methyl formate, ethyl formate, ethyl acetate, methyl acetate, ethanol, methanol or a mixed solvent of two of them containing at least one ester solvent.

[0016] Preferably, the mass ratio of the poor solvent to the good solvent is 1:1-1:1.5, and the molar ratio of the tetracarboxylic dianhydride to the aromatic diamine compound is 1.005:1.

[0017] Preferably, an annular liquid storage cavity is provided at the lower end of the plug-in frame, and liquid inlet holes are evenly provided between the annular liquid storage cavity and the annular cavity.

[0018] Preferably, the stirring unit includes a driving motor, a rotating shaft and stirring blades. The driving motor is installed on the upper end of the plug-in frame through a motor seat, the rotating shaft is installed on the middle part of the plug-in frame through a bearing, the upper end of the rotating shaft is connected to the output shaft of the driving motor, and the stirring blades are evenly installed on the lower end of the rotating shaft.

[0019] Preferably, the rotating and lifting unit includes an electric turntable, a rotating disk, a limiting guide rod and a lifting disk. An annular groove is provided at the lower end of the plug-in frame, in which the electric turntable is installed, and a rotating disk is installed at the lower end of the electric turntable. A sealed cavity is formed between the upper end of the rotating disk and the annular cavity. Limiting guide rods are evenly installed at the lower end of the rotating disk, and a lifting disk is installed between the limiting guide rods. A filtration unit is evenly installed at the upper end of the lifting disk, and a sliding channel that cooperates with the middle part of the filtration unit is provided on the rotating disk.

[0020] Preferably, feed ports are evenly arranged at the lower end of the lifting plate, and the lower end of the feed port is a trumpet-shaped structure.

[0021] Preferably, the filtration unit includes a filtration frame, a sealing part and a filter plate. The filtration frame is evenly installed on the upper end of the lifting plate. The filtration frame is a rectangular hollow structure. The lower end of the filtration frame is connected to the feed port. A sealing part is provided at the lower end of the filtration frame. An opening is provided on the side of the filtration frame, and a filter plate is installed on the opening on the side of the filtration frame.

[0022] Preferably, filter holes are evenly arranged on the filter plate, and the diameter of the filter holes is 0.15-0.20 mm.

[0023] Preferably, the sealing member includes a sealing plate and a flexible pad. The sealing plate is symmetrically arranged at the lower end of the inner part of the filtration frame. A flexible pad is installed between the sealing plate and the filtration frame. The flexible pad is a rectangular hollow structure, and a negative pressure chamber is arranged inside the flexible pad.

[0024] (III) Beneficial effects

[0025] The invention provides a method for preparing transparent polyimide powder. The method comprises the following steps: adding imidization catalyst triethylamine and a polyimide to an aprotic solvent and stirring the mixture evenly; then adding diamine and dianhydride in sequence to form a polyamic acid solution; and then gradually adding acetic anhydride to the mixed solvent. As the reaction proceeds, polyimide powder is gradually precipitated.

[0026] The advantages of adding triethylamine, an imidization catalyst, in advance are that triethylamine can strongly combine with polyamic acid to form a salt structure. 1) This salt structure can reduce the continued branching reaction of the carboxyl group, reduce the generation of cross-linked structures, and avoid the excessively large crystal nuclei generated during the phase separation of polyimide due to excessive molecular weight. 2) The generation of a salt-like structure will reduce the reaction rate of dehydration of the carboxyl group of acetic anhydride imidization, avoid the phase separation crystallization rate being too fast due to rapid dehydration of polyamic acid, and the larger particle size of the powder precipitation; by adjusting the ratio of good solvent to poor solvent, the particle size of the polyimide powder precipitation can be quantitatively controlled. Since the particle size directly affects the subsequent elution process and thus affects the purity of the polyimide, the ratio of good solvent to poor solvent directly determines the quality of the polyimide powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Figure 1 It is a process flow chart of the present invention.

[0029] Figure 2 It is a three-dimensional structural schematic diagram of the present invention.

[0030] Figure 3It is a schematic diagram of the cutaway structure of the present invention.

[0031] Figure 4 It is a three-dimensional structural schematic diagram of the suction filtration device of the present invention.

[0032] Figure 5 It is a schematic diagram of the cutaway structure of the suction filtration device of the present invention.

[0033] Figure 6 It is a schematic diagram of the cross-section structure between the plug-in frame, the rotating lifting unit and the filtration unit of the present invention.

[0034] Figure 7 It is a schematic diagram of the cutaway structure of the filtration unit of the present invention.

[0035] Explanation of the reference numerals: 1. flask; 2. filtration device; 21. plug-in rack; 22. stirring unit; 221. driving motor; 222. rotating shaft; 223. stirring blade; 23. rotating lifting unit; 231. electric turntable; 232. rotating disk; 233. limiting guide rod; 234. lifting disk; 24. filtration unit; 241. filtration rack; 242. sealing member; 2421. sealing plate; 2422. flexible pad; 243. filter plate. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Embodiment 1:

[0038] A method for preparing transparent polyimide powder comprises the following steps:

[0039] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0040] (2) Continue to add 12 g of triethylamine and 230 g of methyl acetate to flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0041] (3) While stirring the flask 1, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen gas stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0042] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0043] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0044] Examples of the acid dianhydride include alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), fluorine-containing aromatic tetracarboxylic dianhydrides such as 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6-FDA), and / or aromatic tetracarboxylic dianhydrides having two carbonyl groups bonded to different aromatic rings such as 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), bis(trimellitic anhydride) ester (TMHQ), bis(1,3-dihydro-1,3-dioxy-5-isobenzofurancarboxylic acid)-(2,2',3,3',5'-hexamethyl[1'-biphenyl]-4-(TME-4), etc.

[0045] The diamine component includes fluorinated aromatic diamines (including fluoroalkyl-substituted benzidine) such as 2,2'-bis(trifluoromethyl)benzidine (TFMB); and / or aromatic diamines having amino groups bonded to different aromatic rings such as 3,3'-diaminodiphenyl sulfone (3,3'-DDS).

[0046] The above-mentioned filtration device 2 includes a plug-in frame 21, a stirring unit 22, a rotating lifting unit 23 and a filtration unit 24. A detachable plug-in frame 21 is arranged at the upper end of the interior of the flask 1. The middle part of the plug-in frame 21 is a hollow structure. An annular cavity is arranged inside the plug-in frame 21. A stirring unit 22 is installed in the middle part of the plug-in frame 21. A rotating lifting unit 23 is installed at the lower end of the plug-in frame 21. The filtration unit 24 is evenly installed on the rotating lifting unit 23. The upper end of the filtration unit 24 is movably arranged inside the annular cavity.

[0047] As a preferred embodiment of the present invention, an annular liquid storage cavity is provided at the lower end of the plug-in frame 21, liquid inlet holes are evenly provided between the annular liquid storage cavity and the annular cavity, and the interior of the annular liquid storage cavity is filled with methanol solution.

[0048] In the above technical scheme, after the transparent polyimide powder is prepared, the rotating lifting unit 23 drives the filtration unit 24 to move downward along the inside of the flask 1, so that the filtration unit 24 can move to the upper end of the precipitated polyimide powder. As the polyimide powder gradually precipitates, the filtration unit 24 can gradually extract and collect the precipitated polyimide powder; when the precipitated polyimide powder is completely extracted, the rotating lifting unit 23 drives the filtration unit 24 to restore upward, and the filtration unit 24 drives the precipitated polyimide powder into the annular cavity, and the methanol solution filled in the annular liquid storage cavity is injected into the annular cavity, and the polyimide powder inside the filtration unit 24 is cleaned and impurities are removed by the methanol solution, thereby obtaining a transparent polyimide powder.

[0049] After the polyimide powder is cleaned, the annular liquid storage chamber absorbs and recovers the methanol solution through the liquid inlet hole. At the same time, the rotating lifting unit 23 can drive the filtration unit 24 to rotate and centrifuge, so that the methanol solution remaining in the filtration unit 24 can be completely thrown out, which is convenient for the accurate recovery of the methanol solution.

[0050] As a preferred embodiment of the present invention, the poor solvent is methyl formate, ethyl formate, ethyl acetate, methyl acetate, ethanol, methanol or a mixed solvent of two of them including at least one ester solvent.

[0051] As a preferred embodiment of the present invention, the mass ratio of the poor solvent to the good solvent is 1:1-1:1.5, preferably 1:1.2, and the molar ratio of the tetracarboxylic dianhydride to the aromatic diamine compound is 1.005:1.

[0052] As a preferred embodiment of the present invention, the stirring unit 22 includes a driving motor 221, a rotating shaft 222 and stirring blades 223. The driving motor is installed on the upper end of the plug-in frame 21 through a motor seat, and a rotating shaft is installed in the middle of the plug-in frame through a bearing. The upper end of the rotating shaft is connected to the output shaft of the driving motor, and the stirring blades are evenly installed on the lower end of the rotating shaft; when the mixed solution is stirred, the driving motor drives the stirring blades to rotate at a high speed through the rotating shaft, thereby realizing the function of stirring and mixing.

[0053] As a preferred embodiment of the present invention, the rotating and lifting unit 23 includes an electric turntable 231, a rotating disk 232, a limiting guide rod 233 and a lifting disk 234. The lower end of the plug-in frame 21 is provided with an annular groove, in which the electric turntable 231 is installed, and the rotating disk 232 is installed at the lower end of the electric turntable 231. A sealed cavity is formed between the upper end of the rotating disk 232 and the annular cavity. The limiting guide rods 233 are evenly installed at the lower end of the rotating disk 231, and the lifting disk 234 is installed between the limiting guide rods 233. The upper end of the lifting disk 234 is evenly installed with the filtration unit 24, and the rotating disk 232 is provided with a sliding channel that cooperates with the middle part of the filtration unit 24.

[0054] In the above technical solution, after the transparent polyimide powder is prepared, the lifting plate 234 moves downward along the limiting guide rod 233, and the filtration unit 24 can move downward synchronously with the lifting plate 234. When the polyimide powder is precipitated, under the action of negative pressure, the polyimide powder can enter the filtration unit 24.

[0055] As a preferred embodiment of the present invention, feed ports are evenly arranged at the lower end of the lifting plate 234, and the lower end of the feed port is a trumpet-shaped structure, thereby improving the collection effect of the polyimide powder.

[0056] As a preferred embodiment of the present invention, the filtration unit 24 includes a filtration frame 241, a sealing member 242 and a filter plate 243. The filtration frame 241 is evenly installed on the upper end of the lifting plate 234. The filtration frame 241 is a rectangular hollow structure. The lower end of the filtration frame 241 is connected to the feed port. The sealing member 242 is provided at the lower end of the filtration frame 241. An opening is provided on the side of the filtration frame 241. The filter plate 243 is installed on the opening on the side of the filtration frame 241.

[0057] In the above technical scheme, when the precipitated polyimide powder is collected, the filter frame 241 first moves downward following the lifting plate 234. When the filter frame 241 drops to the lowest point, the sealing member 242 opens, so that the lower end of the filter frame 241 is opened. At the same time, the interior of the filter frame 241 is in a negative pressure state, so that the precipitated polyimide powder can be completely collected inside the filter frame 241, and the filter plate 243 plays the role of filtering and collecting the polyimide powder.

[0058] As a preferred embodiment of the present invention, the filter plate 243 is evenly provided with filter holes, the diameter of the filter holes is 0.15-0.20 mm, the particle size of the precipitated polyimide powder is in the range of 0.2-1.0 mm, and the precipitated polyimide powder can be completely collected inside the filtration frame 241.

[0059] As a preferred embodiment of the present invention, the sealing member 242 includes a sealing plate 2421 and a flexible pad 2422. The sealing plate 2421 is symmetrically arranged at the lower end of the inner part of the filter frame 241, and a flexible pad 2422 is installed between the sealing plate 2421 and the filter frame 241. The flexible pad 2422 is a rectangular hollow structure, and a negative pressure chamber is arranged inside the flexible pad 2422. When the filter frame 241 drops to the lowest point, negative pressure is generated inside the negative pressure chamber, so that the flexible pad 2422 shrinks, and the sealing plate 2421 moves toward the inner wall of the filter frame 241, and the lower end of the filter frame 241 can then be opened, so as to collect the precipitated polyimide powder. When the polyimide powder is collected, the sealing plate 2421 is restored, so that the collected polyimide powder can be accurately stored inside the filter frame 241.

[0060] Embodiment 2:

[0061] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0062] (2) Continue to add 12 g of triethylamine and 230 g of methyl acetate to flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0063] (3) While stirring the flask 1, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen gas stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0064] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0065] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0066] Embodiment 3:

[0067] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0068] (2) Continue to add 12 g of triethylamine and 230 g of ethyl formate into flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0069] (3) While stirring the flask 1, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen gas stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0070] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0071] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0072] Embodiment 4:

[0073] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0074] (2) Continue to add 12 g of triethylamine and 400 g of methyl acetate into flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0075] (3) While stirring the flask 1, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen gas stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0076] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0077] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0078] Comparative Example 1:

[0079] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0080] (2) Continue to add 12 g of triethylamine to flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0081] (3) While stirring the flask 1, 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen gas stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to perform a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0082] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0083] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0084] Comparative Example 2:

[0085] (1) 230 g of a good solvent, N,N-dimethylacetamide (DMAC), and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine compound having a fluorine group, were added to flask 1 and stirred to dissolve TFMB in DMAC;

[0086] (2) Continue to add 12 g of isoquinoline and 400 g of methyl acetate to flask 1 and stir thoroughly for 1 hour to make the solution fully uniform;

[0087] (3) while stirring the flask (1), 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamic acid solution;

[0088] (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated;

[0089] (5) The contents in the removable flask are extracted using the suction filtration device 2, and the contents are washed with a methanol solution and filtered to obtain a transparent polyimide powder.

[0090] Table 1

[0091]

Claims

1. A method for preparing a transparent polyimide powder, characterized in that: (1) 230 g of a good solvent N,N-dimethylacetamide (DMAC) and 32.024 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) as an aromatic diamine compound having a fluorine group were added to a flask (1) and stirred to dissolve TFMB in DMAC; (2) Continue to add 12 g of triethylamine and 190 g to 400 g of a poor solvent to the flask (1), and stir thoroughly for 1 hour to make the solution fully uniform; (3) while stirring the flask (1), 44.647 g of 4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic dianhydride (6FDA) as a tetracarboxylic dianhydride was added under a nitrogen stream over a period of 10 minutes, and the temperature was adjusted to a temperature range of 20 to 40° C. while continuously stirring for 6 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamic acid solution; (4) adding 60 g of acetic anhydride dropwise to the polyamic acid solution at a rate of 10 g / min, and as the acetic anhydride is gradually added, powdery particles are gradually precipitated; (5) extracting the contents of the detachable flask using the suction filtration device (2), washing the contents with a methanol solution, and filtering to obtain a transparent polyimide powder; The suction filtration device (2) comprises a plug-in frame (21), a stirring unit (22), a rotating lifting unit (23) and a suction filtration unit (24); a detachable plug-in frame (21) is arranged at the upper end of the interior of the flask (1); the middle of the plug-in frame (21) is a hollow structure; an annular cavity is arranged inside the plug-in frame (21); the stirring unit (22) is installed in the middle of the plug-in frame (21); a rotating lifting unit (23) is installed at the lower end of the plug-in frame (21); the suction filtration unit (24) is evenly installed on the rotating lifting unit (23); and the upper end of the suction filtration unit (24) is movably arranged inside the annular cavity.

2. The method for preparing a transparent polyimide powder according to claim 1, characterized in that: The poor solvent is methyl formate, ethyl formate, ethyl acetate, methyl acetate, ethanol, methanol or a mixed solvent of two of the two poor solvents including at least one ester solvent.

3. The method for preparing a transparent polyimide powder according to claim 1, characterized in that: The mass ratio of the poor solvent to the good solvent is 1:1-1:1.5, and the molar ratio of the tetracarboxylic dianhydride to the aromatic diamine compound is 1.005:

1.

4. The method for preparing a transparent polyimide powder according to claim 1, characterized in that: An annular liquid storage cavity is arranged at the lower end of the plug-in frame (21), and liquid inlet holes are evenly arranged between the annular liquid storage cavity and the annular cavity.

5. The method for preparing a transparent polyimide powder according to claim 1, characterized in that: The stirring unit (22) comprises a driving motor (221), a rotating shaft (222) and stirring blades (223); the driving motor (221) is mounted on the upper end of the plug-in frame (21) via a motor seat; the rotating shaft (222) is mounted on the middle part of the plug-in frame (21) via a bearing; the upper end of the rotating shaft (222) is connected to the output shaft of the driving motor (221); and the stirring blades (223) are evenly mounted on the lower end of the rotating shaft (222).

6. The method for preparing a transparent polyimide powder according to claim 1, characterized in that: The rotating lifting unit (23) comprises an electric turntable (231), a rotating disk (232), a limiting guide rod (233) and a lifting disk (234); an annular groove is provided at the lower end of the plug-in frame (21), the electric turntable (231) is installed in the annular groove, a rotating disk (232) is installed at the lower end of the electric turntable (231), a sealed cavity is formed between the upper end of the rotating disk (232) and the annular cavity, limiting guide rods (233) are evenly installed at the lower end of the rotating disk (232), a lifting disk (234) is installed between the limiting guide rods (233), a suction filter unit (24) is evenly installed at the upper end of the lifting disk (234), and a sliding channel matched with the middle part of the suction filter unit (24) is provided on the rotating disk (232).

7. The method for preparing a transparent polyimide powder according to claim 6, characterized in that: The lower end of the lifting plate (234) is evenly provided with feed ports, and the lower end of the feed port is a trumpet-shaped structure.

8. The method for preparing a transparent polyimide powder according to claim 7, characterized in that: The filtration unit (24) comprises a filtration frame (241), a sealing member (242) and a filter plate (243); the filtration frame (241) is evenly mounted on the upper end of the lifting plate (234); the filtration frame (241) is a rectangular hollow structure; the lower end of the filtration frame (241) is connected to the feed inlet; the sealing member (242) is arranged at the lower end of the filtration frame (241); an opening is arranged on the side of the filtration frame (241); and the filter plate (243) is mounted on the opening on the side of the filtration frame (241).

9. The method for preparing a transparent polyimide powder according to claim 8, characterized in that: The filter plate (243) is evenly provided with filter holes, and the diameter of the filter holes is 0.15-0.20 mm.

10. The method for preparing a transparent polyimide powder according to claim 8, characterized in that: The sealing member (242) comprises a sealing plate (2421) and a flexible pad (2422); the sealing plate (2421) is symmetrically arranged at the lower end of the interior of the filtration frame (241); a flexible pad (2422) is installed between the sealing plate (2421) and the filtration frame (241); the flexible pad (2422) is a rectangular hollow structure; a negative pressure chamber is arranged inside the flexible pad (2422).

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