Water-soluble polyimide slurry and preparation method thereof

Abstract

The invention provides water-soluble polyimide slurry and a preparation method thereof, and relates to the technical field of water-soluble polyimide slurry preparation, and the water-soluble polyimide slurry comprises a diamine monomer, a dianhydride monomer, a polar aprotic solvent, pure water and a tertiary amine compound, the preparation method of the water-soluble polyimide slurry comprises the following steps: putting a polar aprotic solvent with qualified moisture into a reaction kettle, then putting a diamine monomer into the solvent, fully stirring until the diamine monomer is uniformly dispersed, cooling the solution to a target temperature, putting a dianhydride monomer into the solution, fully stirring until the dianhydride monomer is uniformly dispersed, and cooling to a target temperature to obtain the water-soluble polyimide slurry. The preparation method comprises the following steps: carrying out polymerization reaction to obtain polyamide acid slurry with viscosity, carrying out wet spinning on the slurry to obtain polyamide acid fibers without polar aprotic solvents, mixing the fibers serving as a raw material with a tertiary amine compound, adding pure water, fully stirring, and filtering to obtain the polyamide acid fiber. The water-soluble polyimide slurry with certain viscosity can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of water-soluble polyimide slurries, and more specifically, particularly relates to a water-soluble polyimide slurry and a preparation method thereof. Background Art

[0002] Polyimide (PI for short) refers to a class of polymers containing imide rings (-CO-NR-CO-) in the main chain, and is one of the organic polymer materials with the best comprehensive performance. It can withstand high temperatures above 400°C, the long-term use temperature range is -200 to 300°C, some have no obvious melting point, has high insulation performance, the dielectric constant is 4.0 at 1000 Hz, and the dielectric loss is only 0.004 to 0.007, belonging to insulation grades F to H.

[0003] The synthesis methods of polyimide are usually the "one-step method" and the "two-step method". However, whether it is the "one-step method" or the "two-step method", the synthesis of polyimide is completed in an organic solvent, and in the subsequent processing process, there is a process step of removing the solvent under high-temperature conditions, which will cause a large amount of organic solvents to form steam and volatilize. And polyimide and its precursor polyamic acid cannot be dissolved in water. Therefore, it is difficult to develop water-soluble polyimide materials.

[0004] Polyamide acid salt is a water-soluble polyimide precursor produced by the reaction of an amine substance with polyamic acid. Converting a polyamic acid slurry containing an organic solvent into a polyamide acid salt slurry using water as a solvent can solve the above problems, but a method that can completely displace the organic solvent in the polyamic acid slurry is required.

[0005] The known preparation methods of general water-based polyimide slurries are divided into the following two categories:

[0006] The first category: Under low-temperature conditions, a dianhydride monomer and a diamine monomer are dissolved in an organic solvent to obtain a polyamic acid slurry with a certain viscosity. The slurry is mixed with poor solvents for polyamic acid such as water and ethanol to obtain polyamic acid solid particles, and the solid particles and an amine compound are dissolved in water together to obtain a water-soluble polyimide slurry. However, this method has the problem of excessive residual organic solvents.

[0007] The second category: At a certain temperature, a diamine monomer and an amine compound are completely dissolved in water together, then the above solution is heated to a certain temperature, and then a dianhydride monomer is added. After a certain reaction time, a water-soluble polyimide slurry is obtained. This method has the problems of low molecular weight, too long reaction time, and is limited by the types of monomers. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a water-soluble polyimide slurry and a preparation method thereof to solve the above problems.

[0009] A preparation method of a water-soluble polyimide slurry, comprising the following steps:

[0010] S1: Add an organic solvent with a moisture content lower than 200 ppm to the jacket of a 20L reaction kettle with continuous nitrogen injection;

[0011] S2: Add all diamine monomers to the solvent at one time and continuously stir until completely dissolved;

[0012] S3: Pass a circulating liquid into the jacket of the reaction kettle to control the temperature of the solution in the reaction kettle;

[0013] S4: Add all dianhydride monomers to the reaction kettle at one time and continuously stir until completely dissolved. The viscosity of the reaction system will continuously increase to obtain a polyamic acid slurry with a certain viscosity;

[0014] S5: Transfer the polyamic acid slurry to a transfer storage tank, and then perform wet spinning to obtain dry, fluffy, and divergent polyamic acid fibers;

[0015] S6: Put the above polyamic acid fibers into the reaction kettle, and add an amine compound with a molar amount 2-2.5 times that of the dianhydride monomer, and stir evenly;

[0016] S7: Add pure water to the above mixture in batches and stir well for 1-3 h to obtain a water-soluble polyimide slurry;

[0017] S8: Filter the above slurry to remove impurities and then perform vacuum degassing.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] High molecular weight and excellent mechanical properties:

[0020] Through the wet spinning process combined with precise polymerization reaction control (such as the molar ratio of dianhydride to diamine monomer being 1:0.99-1.015), the molecular weight of the generated polyamic acid fibers is significantly increased. The tensile strength of the polyimide films in Examples 1 to 4 reaches 255.49-288.17 MPa, far exceeding that of the direct aqueous phase synthesis method in Comparative Examples 5 and 7 (the tensile strength is only 228.17-234.11 MPa), and approaching that of the traditional organic solvent method (Comparative Examples 1 and 2: 289.34-296.71 MPa), realizing the compatibility of water-soluble slurry and high performance.

[0021] Very low residual organic solvents, green and environmentally friendly:

[0022] In the wet spinning process, a multi-stage coagulation bath (containing 20-40% polar aprotic solvent and 60-80% pure water) and a water washing step are adopted to thoroughly remove organic solvents (such as DMAc) in the polyamic acid fiber. In the examples, the solvent residue amount is lower than the detection limit, avoiding the pollution problem caused by the volatilization of organic solvents in the traditional process and meeting the requirements of green chemistry.

[0023] High production efficiency and strong process stability:

[0024] Through staged temperature control (0-50°C circulating liquid temperature control), optimized stirring duration (>3 hours to ensure uniform dispersion of monomers), and solid content control (10%), the polymerization reaction time is shortened to 2-8 hours, and the slurry viscosity is stably within the spinnable range of 10,000-300,000 cps, which is significantly better than the granulation processes of Comparative Examples 3 and 4 (the slurry viscosity fluctuates greatly and additional crushing and drying steps are required).

[0025] Breaking through the limitation of monomer types and having wide applicability:

[0026] In Comparative Examples 6 and 8, when directly synthesizing in the aqueous phase, special diamine monomers such as R3 and APBOA failed in the reaction due to poor solubility. However, in the present invention, by first synthesizing polyamic acid fiber and then reacting with tertiary amine compounds, direct contact of monomers with the aqueous phase is avoided, and various diamine monomers such as ODA, R3, and p-PDA are successfully compatible, expanding the raw material selection range of water-soluble polyimide slurries.

[0027] Improving the uniformity and stability of the slurry:

[0028] The dosage of tertiary amine compounds (such as TEA and IZ) is 2-2.5 times that of the dianhydride monomer. Combining the process of adding water in batches and vacuum degassing, the slurry viscosities in the examples are uniform (such as Example 1: 61,849 cps, Example 4: 248,854 cps), without bubbles and undissolved residues, and can be directly used for coating and film formation, avoiding film coating defects caused by particle agglomeration in the traditional method (such as Comparative Example 3).

[0029] Simplifying the post-treatment process and reducing costs:

[0030] The traditional process needs to prepare polyamic acid salts through steps such as precipitation, drying, and crushing (Comparative Examples 3 and 4), while the present invention obtains fibrous intermediates in one step through wet spinning, omitting complex post-treatment, reducing energy consumption by more than 30%, and having high reaction efficiency between the fiber and tertiary amine, improving the raw material utilization rate. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the preparation process of the water-soluble polyimide slurry of the present invention. Detailed Embodiments

[0032] The following further describes the embodiments of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0033] Please refer to Figure 1 , the present invention provides a water-soluble polyimide slurry. The raw materials for preparing the water-soluble polyimide slurry include diamine monomers, dianhydride monomers, organic solvents, pure water, and tertiary amine compounds: The diamine monomers are one or two of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-diaminobenzanilide (DABA), 2-(4-aminophenyl)-5-aminobenzimidazole (R3), 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA); The dianhydride monomers are one or two of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 4,4'-biphenylether dianhydride (ODPA), bisphenol A type diether dianhydride (BPADA); The organic solvent is one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), γ-butyrolactone (GBL), cyclohexanone (C6H10O); The tertiary amine compound is one of triethylamine (TEA), imidazole (IZ), 1-methylimidazole (MIZ), isoquinoline (IQL).

[0034] Put the moisture-qualified polar aprotic solvent into the reaction kettle, and then put the diamine monomers into the solvent. The circulation liquid is filled into the jacket of the reaction kettle for solution temperature control. Stir well until evenly dispersed. After the solution reaches the target temperature, put the dianhydride monomers into the above solution. As the polymerization reaction proceeds, a polyamic acid slurry with viscosity is obtained. The polyamic acid fiber from which the polar aprotic solvent is removed is obtained by wet spinning of this slurry. Using this fiber as a raw material, it is mixed with a tertiary amine compound, and pure water is added to obtain a water-soluble polyimide slurry with viscosity.

[0035] The moisture qualified standard of the polar aprotic solvent is less than 300 ppm. The temperature of the circulation liquid is between 0-50 °C. The circulation liquid temperature control link is divided into 1 or 2 stages, which are adjusted and set according to the monomer characteristics. The molar ratio of the dianhydride monomers to the diamine monomers is 1:0.99-1.015 to form a higher molecular weight in the polymerization stage. The sign of the even dispersion of the diamine monomers is that there are no obvious visible lumps of the diamine monomers in the reaction kettle, and the stirring time is greater than 3 hours. When preparing the polyamic acid slurry, the solid content is set to 10%. The viscosity of the polyamic acid slurry should be controlled within the suitable spinning range of 100,000-300,000 cps to facilitate spinning to obtain soft and divergent polyamic acid fibers.

[0036] Wet spinning, the process is as follows:

[0037] S1: The polyamic acid slurry is extruded from a spinneret by a metering pump and enters a coagulation bath. The coagulation bath solution is composed of 20 - 40% polar aprotic solvent and 60 - 80% pure water;

[0038] S2: The nascent polyamic acid fibers formed in the coagulation bath are removed of the residual polar aprotic solvent on and inside the fiber surface through a water washing process;

[0039] S3: The nascent fibers after water washing enter the drying section. The temperature environment in this section is 150°C, and the water on and inside the nascent fiber surface is removed by drying, thus obtaining dry, fluffy and divergent polyamic acid fibers.

[0040] Tertiary amine compounds, with the feeding amount being 2 - 2.5 times the molar amount of the dianhydride monomer. The feeding sequence is as follows: Under a 45°C water bath heating, the polyamic acid fibers are fully dispersed and then put into a reaction kettle. Secondly, the tertiary amine compounds are put into the reaction kettle and stirred evenly. Finally, pure water is slowly added into the reaction kettle and stirred fully for 3 - 5 hours to obtain a water-soluble polyimide slurry with a certain viscosity. Its solid content is 10%. It is necessary to filter to remove the incompletely dissolved residual filaments and perform vacuum degassing to remove the air bubbles inside the slurry.

[0041] Example 1:

[0042] S1: Add 1.5 kg of DMAc solvent with a moisture content of 89.045 ppm into the jacket of a 2L reaction kettle with continuous nitrogen purging;

[0043] S2: Pass a coolant at 0°C into the jacket of the reaction kettle to cool down the solution in the reaction kettle;

[0044] S3: Dispose of 79.772 g of ODA monomer into the DMAc solvent at one time and stir fully until completely dissolved. At the same time, the solution is continuously cooled down to 0°C under a cold water bath;

[0045] S4: Slowly add 86.895 g of PMDA monomer into the above solution at one time and continuously stir for 2 h. The viscosity of the reaction system continuously increases;

[0046] S5: Take a sample to test that the viscosity of the slurry is 86451 cps;

[0047] S6: Extrude the above slurry through nitrogen and transfer it into a transfer storage tank after passing through a 5μm filter, and then carry out wet spinning on the machine. Among them, the spinneret specification is 1000×0.03 mm, the first coagulation bath is composed of 30% DMAc and 70% pure water, the second coagulation bath is composed of 15% DMAc and 85% pure water, the washing consists of water washing and ethanol washing, and the drying temperature is set at 110°C;

[0048] S7: After collecting 100 g of the polyamic acid fiber obtained by wet spinning, put it into a dry and clean 1 L reaction kettle, add 50.793 g of TEA, stir evenly, add 900 g of pure water into the reaction kettle in three equal portions, and continuously stir for 2 h;

[0049] S8: Sampling and testing show that the viscosity of the slurry is 61849 cps;

[0050] S9: Use nitrogen to squeeze the above slurry into a 2 μm filter for filtration and then perform vacuum degassing.

[0051] S10: Coat the above slurry on the surface of a clean glass with a coating ingot, and perform thermal imidization according to the following temperature gradient settings:

[0052] 80 °C / 15 min, 150 °C / 15 min, 300 °C / 30 min.

[0053] S11: After removing the imidized polyimide film, perform mechanical property testing according to ASTM-D882 standard, and the tensile strength is 276.53 MPa.

[0054] Example 2:

[0055] S1: Add 1.5 kg of DMAc solvent with a moisture content of 73.881 ppm to the jacket of a 2 L reaction kettle with continuous nitrogen injection;

[0056] S2: Pass 40 °C circulating warm water into the jacket of the reaction kettle for the first-stage circulating liquid temperature control to raise the temperature of the solution in the reaction kettle;

[0057] S3: Dispose of 54.093 g of R3 monomer and 11.180 g of p-PDA monomer into the DMAc solvent at one time, stir well for 3 h. At the same time, the solution is continuously heated to 40 °C in a warm water bath to facilitate the complete dispersion of the R3 monomer in DMAc and avoid agglomeration into blocks;

[0058] S4: Drain the warm water in the jacket of the reaction kettle, and pass in 0 °C freezing liquid to cool the solution in the reaction kettle to 5 °C or below;

[0059] S5: Slowly add 101.390 g of BPDA monomer to the above solution at one time, and continuously stir for 8 h. The viscosity of the reaction system continues to increase;

[0060] S6: Sampling and testing show that the viscosity of the slurry is 119427 cps;

[0061] S7: Transfer the above-mentioned slurry into the intermediate storage tank through nitrogen extrusion and then through a 5-μm filter, and then carry out wet spinning on the machine. Among them, the spinneret has a specification of 1000×0.03 mm. The first coagulation bath consists of 30% DMAc and 70% pure water, the second coagulation bath consists of 15% DMAc and 85% pure water, the washing consists of water washing and ethanol washing, and the drying temperature is set at 110°C;

[0062] S8: Collect 100 g of the polyamic acid fiber obtained by wet spinning and put it into a dry and clean 1-L reaction kettle, add 43.937 g of TEA, stir evenly, add 900 g of pure water into the reaction kettle in three equal portions, and continuously stir for 2 h;

[0063] S9: Take a sample to test that the viscosity of the slurry is 41533 cps;

[0064] S10: Use nitrogen to squeeze the above-mentioned slurry into a 2-μm filter to complete the filtration and then carry out vacuum degassing.

[0065] S11: Coat the above-mentioned slurry on the surface of a clean glass with a film applicator, and carry out thermal imidization according to the following temperature gradient settings:

[0066] 80°C / 15 min, 150°C / 15 min, 300°C / 30 min.

[0067] S12: After removing the imidized polyimide film, carry out mechanical property testing according to the ASTM-D882 standard, and the tensile strength is 288.17 MPa.

[0068] Example 3:

[0069] S1: Add 1.5 kg of DMAc solvent with a moisture content of 93.144 ppm to the jacket of a 2-L reaction kettle with continuous nitrogen injection;

[0070] S2: Inject a coolant at 0°C into the jacket of the reaction kettle to cool down the solution in the reaction kettle;

[0071] S3: Dispose of 79.772 g of ODA monomer into the DMAc solvent at one time, stir thoroughly until completely dissolved. At the same time, the solution is continuously cooled to 0°C in a cold water bath;

[0072] S4: Slowly add 86.895 g of PMDA monomer to the above-mentioned solution at one time, continuously stir for 2 h, and the viscosity of the reaction system continuously increases;

[0073] S5: Take a sample to test that the viscosity of the slurry is 80024 cps;

[0074] S6: Transfer the above-mentioned slurry into the transfer storage tank through nitrogen extrusion and then through a 5-μm filter, and then carry out wet spinning on the machine. Among them, the spinneret has a specification of 1000×0.03 mm. The first coagulation bath consists of 30% DMAc and 70% pure water, the second coagulation bath consists of 15% DMAc and 85% pure water, the washing consists of water washing and ethanol washing, and the drying temperature is set at 110°C;

[0075] S7: Collect 100 g of the polyamic acid fiber obtained by wet spinning and put it into a dry and clean 1-L reaction kettle, add 34.172 g of IZ, stir evenly, and add 900 g of pure water to the reaction kettle in three equal portions, and continuously stir for 2 h;

[0076] S8: Take a sample and test that the viscosity of the slurry is 47952 cps;

[0077] S9: Use nitrogen to extrude the above-mentioned slurry into a 2-μm filter, complete the filtration, and then carry out vacuum degassing.

[0078] S10: Coat the above-mentioned slurry on the surface of a clean glass with a coating ingot, and carry out thermal imidization according to the following temperature gradient settings:

[0079] 80°C / 15 min, 150°C / 15 min, 300°C / 30 min.

[0080] S11: After removing the imidized polyimide film, carry out mechanical property testing according to the ASTM-D882 standard, and the tensile strength is 255.49 MPa

[0081] Example 4:

[0082] S1: Add 1.5 kg of DMAc solvent with a moisture content of 61.355 ppm to the jacket of a 20-L reaction kettle with continuous nitrogen injection;

[0083] S2: Pass 40°C circulating warm water into the jacket of the reaction kettle to carry out the first-stage circulating liquid temperature control to raise the temperature of the solution in the reaction kettle;

[0084] S3: Add 54.093 g of R3 monomer and 11.180 g of p-PDA monomer into the DMAc solvent at one time, stir well for 3 h. At the same time, the solution is continuously heated to 40°C in a warm water bath to facilitate the complete dispersion of the R3 monomer in DMAc and avoid agglomeration into blocks;

[0085] S4: Drain the warm water in the jacket of the reaction kettle, and pass in 0°C coolant to cool the solution in the reaction kettle to 5°C or below;

[0086] S5: Slowly add 101.390 g of BPDA monomer to the above solution at one time, and continuously stir for 8 h. The viscosity of the reaction system continues to increase;

[0087] S6: The viscosity of the sampled slurry is 119427 cps;

[0088] S7: The above slurry is transferred into a transfer storage tank through nitrogen extrusion and passed through a 5-μm filter, and then wet spinning is carried out on a machine. Among them, the spinneret specifications are 1000×0.03 mm, the first coagulation bath consists of 30% DMAc and 70% pure water, the second coagulation bath consists of 15% DMAc and 85% pure water, the washing consists of water washing and ethanol washing, and the drying temperature is set at 110 °C;

[0089] S8: 100 g of the polyamic acid fiber obtained by wet spinning is collected and put into a dry and clean 1-L reaction kettle, 29.559 g of IZ is added, and after stirring evenly, 900 g of pure water is evenly added to the reaction kettle in 3 times, and stirring is continued for 2 h;

[0090] S9: The viscosity of the sampled slurry is 248854 cps;

[0091] S10: The above slurry is extruded into a 2-μm filter by nitrogen for filtration and then vacuum degassed.

[0092] S11: The above slurry is coated on the surface of a clean glass by a coating ingot, and thermal imidization is carried out according to the following temperature gradient settings:

[0093] 80 °C / 15 min, 150 °C / 15 min, 300 °C / 30 min.

[0094] S12: After the imidized polyimide film is removed, mechanical property testing is carried out according to ASTM-D882 standard, and the tensile strength is 271.39 MPa.

[0095] Comparative Example 1:

[0096] S1: 1.5 kg of DMAc solvent with a moisture content of 75.344 ppm is added to the jacket of a 2-L reaction kettle with continuous nitrogen injection;

[0097] S2: A coolant at 0 °C is introduced into the jacket of the reaction kettle to cool the solution in the reaction kettle;

[0098] S3: 79.772 g of ODA monomer is added to the DMAc solvent at one time and stirred thoroughly until completely dissolved. At the same time, the solution is continuously cooled to 0 °C in a cold water bath;

[0099] S4: 86.895 g of PMDA monomer is slowly added to the above solution at one time, and stirring is continued for 2 h, and the viscosity of the reaction system continuously increases;

[0100] S5: The viscosity of the sampled slurry is 80024 cps;

[0101] S6: The slurry is coated on the clean glass surface with a coating ingot, and thermal imidization is performed according to the following temperature gradient setting:

[0102] 80℃ / 15min, 150℃ / 15min, 350℃ / 30min.

[0103] S11: After the imidization of the polyimide film is removed, the mechanical properties are tested according to ASTM-D882. The tensile strength is 289.34 MPa.

[0104] Comparative Example 2:

[0105] S1: Add 1.5 kg of DMAc solvent with a water content of 97.112 ppm into a 2 L reactor into which nitrogen is continuously introduced;

[0106] S2: Circulating warm water at 40°C is introduced into the jacket of the reactor to carry out the first stage of circulating liquid temperature control to increase the temperature of the solution in the reactor;

[0107] S3: 54.093g of R3 monomer and 11.180g of p-PDA monomer were added into DMAc solvent at one time and stirred for 3h. Meanwhile, the solution was heated to 40°C in a warm water bath to facilitate the complete dispersion of R3 monomer in DMAc and avoid agglomeration;

[0108] S4: drain the warm water in the jacket of the reactor, pass 0°C freezing liquid into it, and cool the solution in the reactor to 5°C or below;

[0109] S5: 101.390 g of BPDA monomer was slowly added to the above solution at one time, and the stirring was continued for 8 h. The viscosity of the reaction system continued to increase;

[0110] S6: The viscosity of the sampled slurry was 64218 cps;

[0111] S7: The slurry is coated on the clean glass surface with a coating ingot, and thermal imidization is performed according to the following temperature gradient setting:

[0112] 80℃ / 15min, 150℃ / 15min, 350℃ / 30min.

[0113] S12: After the imidization-completed polyimide film is removed, a mechanical property test is performed according to ASTM-D882, and the tensile strength is 296.71 MPa.

[0114] Comparative Example 3:

[0115] S1: Add 1.5 kg of DMAc solvent with a water content of 75.813 ppm into a 2 L reactor into which nitrogen is continuously introduced;

[0116] S2: Feed the coolant at 0 °C into the jacket of the reaction kettle to cool down the solution in the reaction kettle.

[0117] S3: Dispose 79.772 g of ODA monomer into the DMAc solvent at one time and stir thoroughly until it is completely dissolved. Meanwhile, continuously cool down the solution to 0 °C in a cold water bath.

[0118] S4: Slowly add 86.895 g of PMDA monomer into the above solution at one time and continuously stir for 2 h. The viscosity of the reaction system continuously increases.

[0119] S5: Take a sample to test the viscosity of the slurry, which is 68411 cps.

[0120] S6: Pour the above slurry into a perforated tray with a pore diameter of 5 mm. Place a water tank filled with pure water below the tray. The slurry drops into the water tank drop by drop to form polyamic acid solid particles. Collect and dry all the polyamic acid solid particles under the conditions of 70 °C / 6 h.

[0121] S7: Crush the dried polyamic acid particles into powder in a crusher and dry the polyamic acid powder under the conditions of 70 °C / 3 h.

[0122] S8: Take 100 g of polyamic acid powder into a 1 L reaction kettle, add 50.793 g of TEA, stir evenly, and add 900 g of pure water into the reaction kettle in three equal portions and continuously stir for 2 h.

[0123] S9: Take a sample to test the viscosity of the slurry, which is 36548 cps.

[0124] S10: Use nitrogen to squeeze the above slurry into a 2 μm filter, complete the filtration, and then perform vacuum defoaming.

[0125] S11: Coat the above slurry on the surface of a clean glass with a coating ingot and perform thermal imidization according to the following temperature gradient settings:

[0126] 80 °C / 15 min, 150 °C / 15 min, 300 °C / 30 min.

[0127] S12: After removing the imidized polyimide film, perform mechanical property testing according to the ASTM-D882 standard. The tensile strength is 255.09 MPa.

[0128] Comparative Example 4:

[0129] S1: Add 1.5 kg of DMAc solvent with a water content of 66.229 ppm into the jacket of a 2 L reaction kettle continuously filled with nitrogen.

[0130] S2: Feed the circulating warm water at 40 °C into the jacket of the reaction kettle to carry out the first-stage circulating liquid temperature control, so that the solution in the reaction kettle is heated up.

[0131] S3: Dispose 54.093 g of R3 monomer and 11.180 g of p-PDA monomer into the DMAc solvent at one time, and stir well for 3 h. At the same time, the solution is continuously heated up to 40 °C in a warm water bath to facilitate the complete dispersion of R3 monomer in DMAc and avoid agglomeration into lumps.

[0132] S4: Drain the warm water in the jacket of the reaction kettle completely, and feed the freezing liquid at 0 °C to cool down the solution in the reaction kettle to 5 °C or below.

[0133] S5: Slowly add 101.390 g of BPDA monomer into the above solution at one time, and continuously stir for 8 h. The viscosity of the reaction system continuously increases.

[0134] S6: Take a sample to test that the viscosity of the slurry is 94153 cps.

[0135] S7: Pour the above slurry into a perforated tray with a pore diameter of 5 mm. Place a water tank filled with pure water below the tray. The slurry drops into the water tank drop by drop to form polyamic acid solid particles. Collect and dry all the polyamic acid solid particles under the conditions of 70 °C / 6 h.

[0136] S8: Crush the dried polyamic acid particles into powder in a crusher, and dry the polyamic acid powder under the conditions of 70 °C / 3 h.

[0137] S9: Take 100 g of polyamic acid powder into a 1 L reaction kettle, add 43.937 g of TEA, stir evenly, and add 900 g of pure water into the reaction kettle in three equal portions, and continuously stir for 2 h.

[0138] S10: Take a sample to test that the viscosity of the slurry is 88612 cps.

[0139] S11: Use nitrogen to squeeze the above slurry into a 2 μm filter, and then carry out vacuum degassing after filtration.

[0140] S12: Coat the above slurry on the surface of a clean glass with a coating ingot, and carry out thermal imidization according to the following temperature gradient settings:

[0141] 80 °C / 15 min, 150 °C / 15 min, 300 °C / 30 min.

[0142] S13: After removing the imidized polyimide film, carry out mechanical property tests according to the ASTM-D882 standard. The tensile strength is 261.77 MPa.

[0143] Comparative Example 5:

[0144] S1: Add 900 g of pure water into a 1 L reactor with continuous nitrogen injection. At the same time, continuously inject 25°C constant temperature circulating water into the jacket of the reactor to keep the temperature of the pure water in the reactor at 25°C;

[0145] S2: Add 47.863 g of ODA monomer and 50.793 g of TEA into the reactor at one time, and continuously stir for 30 min until the solid is completely dissolved;

[0146] S3: Add 52.137 g of PMDA monomer into the reactor at one time, and continuously stir;

[0147] S4: Replace the 25°C constant temperature circulating water in the jacket of the reactor with 75°C constant temperature water;

[0148] S5: After continuously stirring for 4 h, a slurry is obtained, and its viscosity is measured to be 25481 cps;

[0149] S6: Coat the above slurry on the surface of a clean glass with a film coating ingot, and carry out thermal imidization according to the following temperature gradient settings:

[0150] 80°C / 15 min, 150°C / 15 min, 300°C / 30 min.

[0151] S7: After removing the imidized polyimide film, carry out mechanical property testing according to ASTM-D882 standard, and the tensile strength is 234.11 MPa.

[0152] Comparative Example Six:

[0153] S1: Add 900 g of pure water into a 1 L reactor with continuous nitrogen injection. At the same time, continuously inject 25°C constant temperature circulating water into the jacket of the reactor to keep the temperature of the pure water in the reactor at 25°C;

[0154] S2: Add 5.524 g of p-PDA monomer, 34.364 g of R3 monomer, and 43.416 g of TEA into the reactor at one time, and continuously stir for 30 min, but the solid is not completely dissolved;

[0155] S3: Add 60.112 g of BPDA monomer into the reactor at one time, and continuously stir;

[0156] S4: Replace the 25°C constant temperature circulating water in the jacket of the reactor with 75°C constant temperature water;

[0157] S5: After continuously stirring for 6 h, no slurry is obtained.

[0158] Comparative Example Seven:

[0159] S1: S1: Add 900g of pure water into a 1L reactor into which nitrogen is continuously introduced. At the same time, 25°C constant temperature circulating water is continuously introduced into the jacket of the reactor to keep the pure water temperature in the reactor at 25°C;

[0160] S2: 47.863 g of ODA monomer and 34.172 g of IZ were added into the reactor at once and stirred for 30 min until the solid was completely dissolved;

[0161] S3: Add 52.137 g of PMDA monomer into the reactor at one time and continue stirring;

[0162] S4: Replace the 25°C constant temperature water in the jacket of the reactor with 75°C constant temperature water;

[0163] S5: After continuous stirring for 4 hours, a slurry was obtained, and its viscosity was tested to be 67118 cps;

[0164] S6: The slurry is coated on the clean glass surface with a coating ingot, and thermal imidization is performed according to the following temperature gradient setting:

[0165] 80℃ / 15min, 150℃ / 15min, 300℃ / 30min.

[0166] S7: After the imidization of the polyimide film is removed, a mechanical property test is performed according to ASTM-D882, and the tensile strength is 228.117 MPa.

[0167] Comparative Example 8:

[0168] S1: Add 900g of pure water into a 1L reactor into which nitrogen is continuously introduced. At the same time, 25°C constant temperature circulating water is continuously introduced into the jacket of the reactor to keep the pure water temperature in the reactor at 25°C;

[0169] S2: 5.524 g p-PDA monomer, 34.364 g R3 monomer, and 29.209 g IZ were added into the reactor at once and stirred for 30 min. The solid was not completely dissolved.

[0170] S3: Add 60.112 g of BPDA monomer into the reactor at one time and continue stirring;

[0171] S4: Replace the 25°C constant temperature water in the jacket of the reactor with 75°C constant temperature water;

[0172] S5: No slurry was obtained after continuous stirring for 6 h.

[0173] The statistical examples and comparative examples are shown in the following table.

[0174]

[0175]

[0176] It can be seen from the above data that the water-soluble polyimide slurry of the present invention not only enables the water-based polyimide slurry to have excellent performance, but also has the characteristics of higher molecular weight, high production efficiency, simple production process, low solvent residue, and more green and environmentally friendly.

[0177] Comparative Examples 1 and 2 are polyimide films obtained by thermal imidization of traditional organic solvent-based polyimide slurry, and their tensile strength is used as a reference for other embodiments and comparative examples. Compared with the polyimide films made from water-soluble polyimide slurries prepared by other methods in Comparative Examples 3, 4, 5, and 7, the polyimide films obtained in Examples 1 to 4 by using the water-soluble polyimide slurry prepared by the wet spinning method in the present invention for film making have better mechanical properties. This fully demonstrates that the water-soluble polyimide slurry and its preparation method provided by the present invention are advanced.

[0178] However, in Comparative Examples 6 and 8, no water-soluble polyimide slurry for film making can be obtained, and the products are solids without viscosity, indicating that the synthesis of polyimide slurry directly in water is limited by the type of monomers, while the water-soluble polyimide slurry and the preparation method thereof provided by the present invention are not subject to this limitation.

[0179] In the present invention, the preparation of high-performance water-soluble polyimide slurry is achieved by combining the "wet spinning" process, which is of great significance to the field related to high-performance water-soluble polyimide.

[0180] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A water-soluble polyimide slurry, characterized in that, The raw materials for its preparation include diamine monomers, dianhydride monomers, polar aprotic solvents, pure water and tertiary amine compounds; the preparation method includes the following steps: (a) Put a polar aprotic solvent with a water content of less than 300 ppm into a reaction kettle, add diamine monomers and stir until completely dispersed; (b) Control the reaction temperature to 0 - 50 °C, add dianhydride monomers to carry out a polymerization reaction to generate a polyamic acid slurry; (c) Make the polyamic acid slurry into polyamic acid fibers through a wet spinning process and remove the solvent; (d) Mix the polyamic acid fibers with tertiary amine compounds, add pure water and stir, filter and defoam to obtain a water-soluble polyimide slurry.

2. The water-soluble polyimide paste according to claim 1, characterized in that The diamine monomers are selected from one or two of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-diaminobenzanilide (DABA), 2-(4-aminophenyl)-5-aminobenzimidazole (R3), 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA).

3. The water-soluble polyimide paste according to claim 1, characterized in that, The dianhydride monomers are selected from one or two of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 4,4'-biphenylether dianhydride (ODPA), bisphenol A type diether dianhydride (BPADA).

4. The water-soluble polyimide slurry according to claim 1, wherein, The polar aprotic solvent is one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), γ-butyrolactone (GBL), cyclohexanone.

5. The water-soluble polyimide slurry according to claim 1, wherein The tertiary amine compounds are selected from one of triethylamine (TEA), imidazole (IZ), 1-methylimidazole (MIZ), isoquinoline (IQL).

6. The water-soluble polyimide slurry according to claim 1, wherein In step (b), the molar ratio of dianhydride monomers to diamine monomers is 1:0.99 - 1.

015.

7. The water-soluble polyimide paste according to claim 1, characterized in that In step (c), the wet spinning process includes: (i) Extrude the polyamic acid slurry through a spinneret into a coagulation bath, and the coagulation bath is composed of 20 - 40% polar aprotic solvent and 60 - 80% pure water; (ii) Wash and dry the nascent fibers, and the drying temperature is 100 - 150 °C.

8. The water-soluble polyimide paste according to claim 1, wherein, In step (d), the feeding amount of the tertiary amine compound is 2 - 2.5 times the amount of substance of the dianhydride monomer.

9. The water-soluble polyimide paste according to claim 1, wherein, In step (d), the stirring time is 3 - 5 hours, the viscosity of the obtained slurry is 10,000 - 300,000 cps, and the solid content is 10%.

10. A method for preparing the water-soluble polyimide slurry according to any one of claims 1-9, characterized in that, It includes all the process steps of steps (a) to (d) in claim 1.

Images