Polyamic acid slurry for chemical preparation of polyimide films, and its production system and method

Abstract

This invention discloses a polyamic acid slurry for the chemical preparation of polyimide films, as well as its production system and method, relating to the field of polyamic acid slurry technology. This invention fully utilizes the reaction characteristics of polyamic acid, and incorporates a closed raw material feeding system, stepwise addition of dianhydrides and third monomer viscosity adjustment, material temporary storage and degassing, and hardener preparation processes, thereby improving the quality of the polyamic acid slurry product and facilitating the industrial production of polyimide films.

Description

Technical Field

[0001] This invention relates to the field of polyamic acid slurry technology, and more specifically to polyamic acid slurry for chemical preparation of polyimide films, as well as its production system and method. Background Technology

[0002] Polyimide (PI) is a polymer containing an imide (-CO-NH-CO-) structure in its main chain. It possesses high insulation, excellent mechanical properties, resistance to high / low temperatures, radiation resistance, high flame retardancy, and high stability. In the electronics field, PI film exhibits the best compatibility with modern electronic manufacturing processes and is a primary material used in the production of flexible printed circuit boards.

[0003] Currently, domestic PI film production mainly relies on the thermal imidization method, accounting for over 90% of the total domestic capacity. The chemical method for PI film production is highly confidential, with limited publicly available information. Compared to the thermal imidization method, the chemical method offers advantages such as lower imidization temperature, higher production efficiency, better film uniformity, and less susceptibility to bubbles or cracks. The resulting PI films can be used in high-end applications such as flexible circuit boards and copper-clad laminates.

[0004] Current research on the chemical production of electronic-grade PI films mainly focuses on laboratory formulations, with no complete industrially feasible process flow yet. For example, Chinese invention patent CN106883431B discloses a method for preparing low-absorbency polyimide films. This method involves mixing diamine monomer A and dianhydride monomer A in a polar solvent to obtain a flexible polyamic acid resin solution A; under N2 protection, mixing diamine monomer B and dianhydride monomer B in a polar solvent to obtain a rigid polyamic acid resin solution B; under N2 protection, mixing the flexible polyamic acid resin solution A and the rigid polyamic acid resin solution B, stirring, and terminating the reaction when the viscosity of the reactants reaches 2000-3500 poise; finally, adding an accelerator and a dehydrating agent, mixing thoroughly, casting to form a film, and then imidizing to obtain the low-absorbency polyimide film.

[0005] The aforementioned patents focus on laboratory formulation research, and the preparation process of polyamic acid slurry only involves laboratory synthesis steps, without addressing specific industrial-scale complete process flows and production systems. This leads to unstable quality of the produced polyamic acid slurry, ultimately resulting in numerous defects in the prepared PI film. Therefore, there is an urgent need to develop a polyamic acid slurry production system and method suitable for industrial application to solve the above problems. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the problems of unstable quality of polyamic acid slurry in the prior art, which leads to defects in film production. This invention provides a polyamic acid slurry for the chemical preparation of polyimide films, as well as its production system and method. This not only systematically solves the problem of precise control of polymerization reaction and improves the stability of polyamic acid synthesis, but also better controls the molecular weight distribution of polyamic acid, thereby improving production efficiency and reducing scrap rate.

[0007] The technical solution of this invention is as follows:

[0008] In a first aspect, the present invention provides a production system for polyamic acid slurry used in the chemical preparation of polyimide films, comprising a dianhydride silo and a diamine silo. The dianhydride silo is connected to a dianhydride weighing device via pipelines, and the diamine silo is connected to a diamine weighing device via pipelines. The dianhydride weighing device and the diamine weighing device are respectively connected to a first polymerization reactor via pipelines. The first polymerization reactor is connected to a solvent inlet pipeline. The dianhydride weighing device is also connected to a dianhydride solution mixing tank via pipelines, and the dianhydride solution mixing tank is connected to a solvent inlet pipeline. The outlets of the first polymerization reactor and the dianhydride solution mixing tank are respectively connected to a second polymerization reactor via pipelines. The inlet of the second polymerization reactor is connected to a third monomer solution mixing tank via pipelines. The mixing tank is connected to a solvent feed line three; the outlet of the second polymerization reactor is connected to a polyamic acid slurry storage tank via a pipeline, the outlet of the polyamic acid slurry storage tank is connected to a deaerator via a pipeline, the deaerator is connected to a vacuum pump via a pipeline, the outlet of the deaerator is connected to an impingement flow mixer via a pipeline, the inlet of the impingement flow mixer is connected to a hardener mixing tank via a pipeline, the hardener mixing tank is connected to a catalyst feed line, a dehydrating agent feed line, and a solvent feed line four, and the outlet of the impingement flow mixer is connected to a needle-rod mixer via a pipeline; the first polymerization reactor, the dianhydride solution mixing tank, the second polymerization reactor, the third monomer solution mixing tank, the polyamic acid slurry storage tank, the deaerator, the hardener mixing tank, and the needle-rod mixer are all equipped with agitators.

[0009] Preferably, two second polymerization reactors are connected in parallel; two polyamic acid slurry storage tanks are connected in parallel.

[0010] Preferably, the first polymerization reactor, the dianhydride solution mixing tank, the second polymerization reactor, the third monomer solution mixing tank, the polyamic acid slurry temporary storage tank, the degasser, the hardener mixing tank, and the needle-bar mixer are each provided with a cooling jacket.

[0011] Secondly, the present invention provides a method for producing a polyamic acid slurry for chemically preparing polyimide films, wherein the method is carried out using the aforementioned production system for producing polyamic acid slurry for chemically preparing polyimide films, and includes the following steps:

[0012] S1: Solid raw materials diamine, dianhydride, and solvent are added to the first polymerization reactor and polymerized at atmospheric pressure at -10~50℃ for 1~3 hours. The dianhydride is added to the first polymerization reactor in 3~5 portions, with an interval of 20~40 minutes between each addition. The amount of dianhydride added each time accounts for 20~33.4% of the total mass of dianhydride added to the first polymerization reactor. The dianhydride is added in 3~5 portions to ensure that the reaction temperature rise after each addition is less than 10℃, which can make the molecular weight distribution narrower. After the addition, the dianhydride is rapidly dispersed under the action of the stirrer.

[0013] S2: After the material from the first polymerization reactor has been reacted, it is transferred to the second polymerization reactor. The dianhydride solution is added to the second polymerization reactor, and the addition time of the dianhydride solution is controlled to be >2h. Then, the third monomer solution is added dropwise, and the addition time of the third monomer solution is controlled to be >2h. The dropwise addition is stopped when the viscosity of the material is 100~1000Pa·s. The polymerization reaction is carried out at 40~60℃ under normal pressure for 3~7h.

[0014] S3: After the reaction of 2 to 5 batches of the second polymerization reactor, the material is transported to the polyamic acid slurry temporary storage tank for storage and uniform mixing. The storage temperature is -15 to 0℃. Then, the uniformly mixed polyamic acid slurry is transported to the deaerator for vacuum deaeration. The vacuum deaeration temperature is -15 to 10℃ and the pressure is 10 to 1000Pa.

[0015] S4: After the catalyst, dehydrating agent and solvent are mixed into a hardener in the hardener mixing tank, they are added together with the vacuum degassed polyamic acid slurry into the impingement flow mixer to complete the premixing; then it is transported to the needle bar mixer for further mixing. The mixing temperature is -15~0℃. After uniform mixing, the polyamic acid slurry used for the chemical preparation of polyimide films is obtained.

[0016] Preferably, in step S1, the dianhydride is pyromellitic dianhydride (PMDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA), or hexafluoroisopropylphthalic anhydride (6FDA); the diamine is 4,4'-diaminodiphenyl ether (ODA), 2,2'-bis(4-aminophenoxyphenyl)propane (BAPP), or 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl (TFMB); the solvent used in step S1, the solvent used in the dianhydride solution and the third monomer solution in step S2, and the solvent used in step S4 are dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP).

[0017] Preferably, in step S1, the molar ratio of diamine to dianhydride is (1.1-1.5):1, the viscosity of the material is 5000~30000 cP after the reaction in the first polymerization reactor is completed, and the stirring speed of the first polymerization reactor is 10~80 rpm.

[0018] Preferably, in step S2, the concentration of the dianhydride solution is 10-20 wt.%, and the molar ratio of the dianhydride in the dianhydride solution to the dianhydride in step S1 is (0.4-1):1; the third monomer is p-phenylenediamine (PDA), m-phenylenediamine (MPD), or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF); the concentration of the third monomer solution is 10-15 wt.%.

[0019] Preferably, in step S2, the stirring speed of the second polymerization reactor is 10~120 rpm; nitrogen is purged during the discharge process of the second polymerization reactor, and the pressure inside the second polymerization reactor is 0.1~0.25 MPaG at this time.

[0020] Preferably, in step S4, the catalyst is isoquinoline, pyridine, or triethylamine, and the dehydrating agent is acetic anhydride, propionic anhydride, or butyric anhydride; in the hardener, the catalyst concentration is 5~10 wt.%, and the dehydrating agent concentration is 20~50 wt.%; the mass ratio of polyamic acid slurry to hardener is (2.5~3.5):1, and the stirring speed of the needle-bar mixer is 5~20 rpm.

[0021] Thirdly, the present invention provides a polyamic acid slurry for chemically preparing polyimide films, which is produced by the above-described production method of the polyamic acid slurry for chemically preparing polyimide films.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention provides a complete production system for polyamic acid slurry, employing a closed feeding method to reduce the contact between materials and air, thereby improving material metering accuracy. Furthermore, the polyamic acid slurry production process of this invention adopts a two-step reaction and stepwise addition of dianhydride monomers, allowing for more flexible control of the reaction process and improved process stability. Simultaneously, the third monomer corrects viscosity deviations during polymerization, inhibiting or promoting molecular weight growth to ensure the viscosity of the material in the second polymerization reactor reaches 100~1000 Pa·s, guaranteeing that the polyamic acid slurry meets the requirements of downstream film-forming processes, thereby reducing downstream waste film.

[0024] 2. By setting up a polyamic acid slurry temporary storage tank, this invention adds a multi-batch polyamic acid slurry mixing process to the production process, effectively resolving the differences between different batches of polyamic acid slurry, averaging and correcting the characteristics (such as molecular weight, solid content, viscosity, etc.) of multiple batches of polyamic acid slurry, eliminating single-batch fluctuations, ensuring uniform characteristics, thereby avoiding quality deviations of polyimide films from the source and improving product stability.

[0025] 3. The process flow of this invention is universal; by changing the dianhydride or diamine raw materials, various grades of polyimide film products can be produced. This invention's process is simple and effective, significantly improving the quality of polyimide film products and is easy to promote and apply. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the production system for polyamic acid slurry used in the chemical preparation of polyimide films according to the present invention.

[0027] In the diagram, 1. Dianhydride silo; 2. Diamine silo; 3. Dianhydride weighing device; 4. Diamine weighing device; 5. First polymerization reactor; 501. Solvent feed line one; 502. First polymer transfer pump; 6. Dianhydride solution mixing tank; 601. Solvent feed line two; 602. Dianhydride solution transfer pump; 7. Second polymerization reactor; 701. Second polymer transfer pump; 8. Third monomer solution mixing tank; 801. Third monomer solution transfer pump; 80 2. Solvent feed line three; 9. Polyamic acid slurry temporary storage tank; 901. Polyamic acid slurry transfer pump; 10. Deaerator; 1001. Vacuum pump; 1002. Deaerated polyamic acid slurry transfer pump; 11. Impingement flow mixer; 12. Hardener mixing tank; 1201. Hardener transfer pump; 1202. Catalyst feed line; 1203. Dehydrating agent feed line; 1204. Solvent feed line four; 13. Needle bar mixer; 14. Agitator. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0029] like Figure 1 As shown in the following embodiments, the production system used to produce polyamic acid slurry for the chemical preparation of polyimide films includes a dianhydride silo 1 and a diamine silo 2. The dianhydride silo 1 is connected to a dianhydride weighing device 3 via pipelines, and the diamine silo 2 is connected to a diamine weighing device 4 via pipelines. The dianhydride weighing device 3 and the diamine weighing device 4 are respectively connected to a first polymerization reactor 5 via pipelines. The first polymerization reactor 5 is connected to a solvent feed pipeline 501. The weighed raw materials, dianhydride and diamine, are added to the first polymerization reactor 5 in solid form, and a polymerization reaction is carried out in the solvent.

[0030] The dianhydride weighing device 3 is also connected to a dianhydride solution mixing tank 6 via a pipeline, and the dianhydride solution mixing tank 6 is connected to a solvent feed pipeline 601. The outlet of the first polymerization reactor 5 is connected to a second polymerization reactor 7 via a pipeline, and a first polymer transfer pump 502 is installed on the pipeline; the outlet of the dianhydride solution mixing tank 6 is connected to the second polymerization reactor 7 via a pipeline, and a dianhydride solution transfer pump 602 is installed on the pipeline; the inlet of the second polymerization reactor 7 is connected to a third monomer solution mixing tank 8 via a pipeline, and a third monomer solution transfer pump 801 is installed on the pipeline; the third monomer solution mixing tank 8 is connected to a solvent feed pipeline 802. The material after the reaction in the first polymerization reactor 5 is transported to the second polymerization reactor 7 via the first polymer transfer pump 502, the dianhydride solution prepared in the dianhydride solution mixing tank 6 is transported to the second polymerization reactor 7 via the dianhydride solution transfer pump 602, and the solvent is added to the second polymerization reactor 7 via the solvent feed pipeline 802 for a second polymerization reaction. Among them, there are two second polymerization reactors 7 connected in parallel, one for use and one for standby.

[0031] Meanwhile, the outlet of the second polymerization reactor 7 is connected to a polyamic acid slurry storage tank 9 via a pipeline, and a second polymer transfer pump 701 is installed on the pipeline. The outlet of the polyamic acid slurry storage tank 9 is connected to a deaerator 10 via a pipeline, and a polyamic acid slurry transfer pump 901 is installed on the pipeline. The deaerator 10 is connected to a vacuum pump 1001 via a pipeline. After the reaction in the second polymerization reactor 7, the material is transported to the polyamic acid slurry storage tank 9 for storage via the second polymer transfer pump 701. Two to five batches of reacted material can be stored together in the polyamic acid slurry storage tank 9 for uniform mixing, which can effectively resolve the differences between different batches of polyamic acid slurry and improve the quality of the subsequently prepared polyimide film. There are two polyamic acid slurry storage tanks 9 connected in parallel, one for use and one for standby. Different batches of polyamic acid slurry after mixing are then transported to the deaerator 10 for vacuum deaeration via the polyamic acid slurry transfer pump 901.

[0032] The outlet of the deaerator 10 is connected to an impingement flow mixer 11 via a pipeline, and a deaerated polyamic acid slurry delivery pump 1002 is installed on the pipeline. The inlet of the impingement flow mixer 11 is connected to a hardener mixing tank 12 via a pipeline, and a hardener delivery pump 1201 is installed on the pipeline. The hardener mixing tank 12 is connected to a catalyst feed pipeline 1202, a dehydrating agent feed pipeline 1203, and a solvent feed pipeline 1204. The outlet of the impingement flow mixer 11 is connected to a needle-rod mixer 13 via a pipeline. The first polymerization reactor 5, the dianhydride solution mixing tank 6, the second polymerization reactor 7, the third monomer solution mixing tank 8, the polyamic acid slurry temporary storage tank 9, the deaerator 10, the hardener mixing tank 12, and the needle-rod mixer 13 are all equipped with agitators 14. The catalyst, dehydrating agent and solvent are mixed together in the hardener mixing tank 12 to form a hardener, which is then premixed with the degassed polyamic acid slurry in the impingement flow mixer 11 and then further mixed in the needle bar mixer 13. After discharge, the polyamic acid slurry used for the chemical preparation of polyimide films is obtained.

[0033] In addition, cooling jackets are provided on the exterior of the first polymerization reactor 5, the dianhydride solution mixing tank 6, the second polymerization reactor 7, the third monomer solution mixing tank 8, the polyamic acid slurry temporary storage tank 9, the deaerator 10, the hardener mixing tank 12, and the needle-bar mixer 13. The operating temperature of each device is controlled by circulating chilled water into the cooling jackets.

[0034] Example 1

[0035] The method for producing polyamic acid slurry for chemically preparing polyimide films according to this embodiment includes the following steps:

[0036] S1: Add 255 kg of DMF to the first polymerization reactor 5; seal the drummed ODA and PMDA and separately add them to the diamine silo 2 and dianhydride silo 1, respectively. Weigh 25.9 kg of ODA and 18.8 kg of PMDA and add them to the first polymerization reactor 5 for reaction. The reaction temperature is controlled at 45℃, the stirrer 14 speed is 80 rpm, and the reaction time is 2.5 h. After the reaction, the viscosity of the material is 30000 cP. Among them, PMDA is added to the first polymerization reactor 5 in 4 portions, with an interval of 30 min between each addition, and the amount of PMDA added each time is 4.7 kg.

[0037] S2: After the reaction in the first polymerization reactor 5 is completed, the material is transported to the second polymerization reactor 7 via the first polymer transfer pump 502. 125.3 kg of a 15 wt.% PMDA solution (DMF solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 50.2 kg / h. Subsequently, 30.67 kg of a 15 wt.% PDA solution (DMF solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 14.56 kg / h. When the PDA solution reaches 95 wt.%, the addition is switched to dropwise addition. When the polymer viscosity reaches 300 Pa·s, the addition of PDA solution is stopped. The reaction temperature in the second polymerization reactor 7 is controlled at 50℃, the stirrer 14 rotates at 100 rpm, and the reaction time is 5 hours.

[0038] S3: After the second polymerization reaction is completed, the material is transported to the polyamic acid slurry storage tank 9 via the second polymer transfer pump 701 for storage. Nitrogen gas is purged during the discharge process from the second polymerization reactor 7 at a pressure of 0.1 MPaG. Steps S1 and S2 are repeated three times, with the material from each second polymerization reaction being transported to the polyamic acid slurry storage tank 9 for storage, ensuring uniform mixing of these batches of reactants. Chilled water is circulated into the cooling jacket of the polyamic acid slurry storage tank 9 to maintain the storage temperature of the reactants at 0°C.

[0039] The mixed reactants are pumped to a deaerator 10 via a polyamic acid slurry pump 901 for degassing. The deaerator 10 is evacuated by a vacuum pump 1001. The operating pressure of the deaerator 10 is 500 Pa, and the operating temperature is controlled at 0 °C by circulating chilled water into the cooling jacket of the deaerator 10.

[0040] S4: 36.4 kg of isoquinoline, 145.6 kg of acetic anhydride, and 546 kg of DMF are added to the hardener mixing tank 12 to prepare the hardener. This hardener is then pumped to the impingement mixer 11 via the hardener delivery pump 1201, where it is pre-mixed with 1822.68 kg of degassed polyamic acid slurry through high-speed impingement. It is then further mixed in the needle-and-bar mixer 13, with the stirrer 14 rotating at 10 rpm. The mixing temperature is controlled at 0°C by circulating chilled water into the cooling jacket of the needle-and-bar mixer 13. After homogeneous mixing, the polyamic acid slurry for chemically preparing polyimide films is obtained.

[0041] Example 2

[0042] The method for producing polyamic acid slurry for chemically preparing polyimide films according to this embodiment includes the following steps:

[0043] S1: Add 80 kg of DMAc to the first polymerization reactor 5; seal the drummed 6FDA and TFMB separately into the diamine silo 2 and dianhydride silo 1, respectively; weigh 6.9 kg of TFMB and 6.95 kg of 6FDA and add them to the first polymerization reactor 5 for reaction. The reaction temperature is controlled at 50℃, the stirrer 14 speed is 50 rpm, and the reaction time is 1 hour. After the reaction, the viscosity of the material is approximately 25000 cP. 6FDA is added to the first polymerization reactor 5 in 5 portions, 40 minutes apart, with each addition being 1.39 kg.

[0044] S2: After the reaction in the first polymerization reactor 5 is completed, the material is transported to the second polymerization reactor 7 via the first polymer transfer pump 502. 34.75 kg of a 20 wt.% 6FDA solution (DMAc solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 13.9 kg / h. Subsequently, 41.67 kg of a 12 wt.% BDAF solution (DMAc solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 15.83 kg / h. When the BDAF solution reaches 95 wt.%, the addition is switched to dropwise addition. When the polymer viscosity reaches 1000 Pa·s, the addition of BDAF solution is stopped. The reaction temperature in the second polymerization reactor 7 is controlled at 60℃, the stirrer 14 rotates at 120 rpm, and the reaction time is 3 hours.

[0045] S3: After the second polymerization reaction is completed, the material is transported to the polyamic acid slurry storage tank 9 via the second polymer transfer pump 701 for storage. Nitrogen gas is purged during the discharge process from the second polymerization reactor 7 at a pressure of 0.25 MPaG. Steps S1 and S2 are repeated once more, with each batch of material after the second polymerization reaction being transported to the polyamic acid slurry storage tank 9 for storage, ensuring uniform mixing of these batches of reactants. Chilled water is circulated into the cooling jacket of the polyamic acid slurry storage tank 9 to maintain the storage temperature of the reactants at -5°C.

[0046] The mixed reactants are pumped to the deaerator 10 by the polyamic acid slurry transfer pump 901 for degassing. The deaerator 10 is evacuated by the vacuum pump 1001. The operating pressure of the deaerator 10 is 10 Pa, and the operating temperature is controlled at 10 °C by circulating chilled water into the cooling jacket of the deaerator 10.

[0047] S4: 9.04 kg of pyridine catalyst, 33.9 kg of propionic anhydride dehydrating agent, and 70 kg of DMAc are added to the hardener mixing tank 12 to prepare the hardener. This hardener is then pumped to the impingement mixer 11 via the hardener delivery pump 1201, where it is pre-mixed with 340.54 kg of degassed polyamic acid slurry through high-speed collision. It is then further mixed in the needle-and-bar mixer 13, with the stirrer 14 rotating at 20 rpm. The mixing temperature is controlled at -5°C by circulating chilled water into the cooling jacket of the needle-and-bar mixer 13. After homogeneous mixing, the polyamic acid slurry for chemical preparation of polyimide films is obtained.

[0048] Example 3

[0049] The method for producing polyamic acid slurry for chemically preparing polyimide films according to this embodiment includes the following steps:

[0050] S1: Add 191 kg of NMP to the first polymerization reactor 5; seal the drummed BPDA and BAPP into the diamine silo 2 and dianhydride silo 1 respectively, and weigh 26 kg of BAPP and 16.2 kg of BPDA into the first polymerization reactor 5 for reaction. The reaction temperature is controlled at -10℃, the stirrer 14 speed is 10 rpm, and the reaction time is 3 hours. After the reaction, the viscosity of the material is about 5000 cP. BPDA is added to the first polymerization reactor 5 in 3 portions, 20 minutes apart, with each addition being 5.4 kg.

[0051] S2: After the reaction in the first polymerization reactor 5 is completed, the material is transported to the second polymerization reactor 7 via the first polymer transfer pump 502. 69.5 kg of a 10 wt.% BPDA solution (NMP solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 27.8 kg / h. Subsequently, 16.5 kg of a 10 wt.% MPD solution (NMP solvent) is added dropwise to the second polymerization reactor 7 at a flow rate of 7.84 kg / h. When the MPD solution reaches 95 wt.%, the addition is switched to dropwise addition. When the polymer viscosity reaches 100 Pa·s, the addition of MPD solution is stopped. The reaction temperature in the second polymerization reactor 7 is controlled at 40℃, the stirrer 14 rotates at 10 rpm, and the reaction time is 7 hours.

[0052] S3: After the second polymerization reaction is completed, the material is transported to the polyamic acid slurry storage tank 9 via the second polymer transfer pump 701 for storage. Nitrogen gas is purged during the discharge process from the second polymerization reactor 7 at a pressure of 0.2 MPaG. Steps S1 and S2 are repeated four times, with the material from each second polymerization reaction being transported to the polyamic acid slurry storage tank 9 for storage, ensuring uniform mixing of these batches of reactants. Chilled water is circulated into the cooling jacket of the polyamic acid slurry storage tank 9 to maintain the storage temperature of the reactants at -15°C.

[0053] The mixed reactants are pumped to the deaerator 10 via the polyamic acid slurry transfer pump 901 for degassing. The deaerator 10 is evacuated by the vacuum pump 1001. The operating pressure of the deaerator 10 is 1000 Pa, and the operating temperature is controlled at -15°C by circulating chilled water into the cooling jacket of the deaerator 10.

[0054] S4: 45.6 kg of triethylamine catalyst, 228 kg of butyric anhydride dehydrating agent, and 182.4 kg of NMP are added to the hardener mixing tank 12 to prepare the hardener. This hardener is then pumped to the impingement mixer 11 via the hardener delivery pump 1201, where it is pre-mixed with 1596 kg of degassed polyamic acid slurry through high-speed impingement. It is then further mixed in the needle-and-bar mixer 13, with the stirrer 14 rotating at 5 rpm. The mixing temperature is controlled at -15°C by circulating chilled water into the cooling jacket of the needle-and-bar mixer 13. After homogeneous mixing, the polyamic acid slurry for chemical preparation of polyimide films is obtained.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that in step S1, PMDA is added to the first polymerization reactor 5 all at once.

[0057] The molecular weight distribution index (PDI) of the reaction products obtained after the second polymerization reaction in step S2 of Example 1 and Comparative Example 1 was tested. The PDI of the product in Example 1 was 1.6, and the PDI of the product in Comparative Example 1 was 1.8. The comparison shows that the molecular weight distribution of the product in the second polymerization reaction of Example 1 is narrower. This is because Comparative Example 1 added the solid dianhydride raw material to the first polymerization reactor 5 all at once, resulting in a temperature rise of approximately 23°C. In contrast, Example 1 added the solid dianhydride raw material PMDA in small batches multiple times during the first polymerization reaction, which prevented local accumulation of PMDA and uneven reaction. The temperature rise for each addition was approximately 10°C, and the low temperature rise suppressed side reactions, thus narrowing the molecular weight distribution of the reaction product.

[0058] Comparative Example 2

[0059] The difference from Example 1 is that PMDA and PDA in step S2 are added to the first polymerization reactor 5 in the form of solid raw materials, and the solvent DMF of PMDA solution and PDA solution is added to the first polymerization reactor 5 together with DMF in step S1.

[0060] The PDI of the reaction product obtained after the second polymerization reaction in step S2 of Comparative Example 2 was 2. Compared with Example 1, Example 1, using a stepwise polymerization method, allows for precise control of the reaction parameters at different stages, enabling refined regulation of the polymerization process. Comparative Example 2, using a one-step polymerization reaction, is prone to large differences in local reaction rates, leading to some chain segments growing too fast and others too slowly, ultimately resulting in a wider molecular weight distribution. Stepwise polymerization, by breaking down the reaction process into ordered stages, allows for targeted regulation of the reaction process at each stage, reducing uneven chain growth caused by drastic changes in the reaction environment, thereby effectively narrowing the molecular weight distribution of the product.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that in step S2, PDA solution is not added to the second polymerization reactor 7.

[0063] The PDI of the reaction product obtained after the second polymerization reaction in step S2 of Comparative Example 3 was 1.7. This comparison shows that the molecular weight distribution of the product from the second polymerization reaction in Example 1 is narrower. This is because the third monomer PDA added in Example 1 is a rigid short-chain diamine, and its reactivity differs from that of ODA: when PDA is added dropwise in step S2, it preferentially binds to the ends of excessively growing high-molecular-weight active chains in the system, terminating further chain growth through its rigid short-chain structure; simultaneously, PDA can also bind to low-molecular-weight active chains, moderately extending their chain length, ultimately achieving bidirectional regulation by inhibiting high-molecular-weight chains and completing low-molecular-weight chains, thereby narrowing the molecular weight distribution range.

[0064] Comparative Example 4

[0065] The difference from Example 1 is that in step S1, the amount of ODA added is 30 kg; and in step S2, the amount of PDA solution added is 16 kg.

[0066] The PDI of the reaction product obtained after the second polymerization reaction in step S2 of Comparative Example 4 was 1.7. This comparison shows that the molecular weight distribution of the product from the second polymerization reaction in Example 1 is narrower. This is because the ratio of diamine ODA to dianhydride PMDA added to the first polymerization reactor 5 in Comparative Example 1 was unbalanced. The excessive amount of ODA resulted in a polymer viscosity as low as 1000 cP in the first polymerization reactor 5, while simultaneously reducing the amount of PDA added to the second polymerization reactor 7, thus weakening the control of the third monomer on product performance. Due to the imbalance in the proportion control of key monomers in the stepwise reaction, even with a stepwise polymerization process, improper raw material ratios at a certain stage can still lead to a decrease in chain growth uniformity, resulting in a higher PDI of the product.

[0067] Comparative Example 5

[0068] The difference from Example 1 is that in step S2, when the PDA solution is added dropwise to 95 wt.%, the addition is switched to dropwise addition, and when the polymer viscosity is 1200 Pa·s, the addition of PDA solution is stopped.

[0069] Comparative Example 6

[0070] The difference from Example 1 is that in step S3, the material after the second polymerization reaction is completed is directly transported to the deaerator 10 for deaeration, and is not transported to the polyamic acid slurry temporary storage tank 9 for storage.

[0071] Comparative Example 7

[0072] The difference from Example 1 is that in step S4, the hardener and the degassed polyamic acid slurry are directly fed into the needle-bar mixer 13 without being premixed in the impingement flow mixer 11.

[0073] The polyamic acid slurries produced in Examples 1-3 and Comparative Examples 1-7 were fed into a film stretching device for film stretching. After casting, transverse stretching, longitudinal stretching, and slitting, 12.5 μm thick polyimide films were formed. The polyimide films prepared in Examples 1-3 and Comparative Examples 1-7 were tested. The coefficient of thermal expansion was determined according to ASTM D696, "Standard Test Method for Determining the Linear Coefficient of Thermal Expansion of Plastics in the Range of -30°C and 30°C Using a Quartz Glass Expansion Meter"; the tensile strength was determined according to ASTM D882, "Standard Test Method for Tensile Properties of Plastic Sheets"; and the glass transition temperature was determined according to GB / T 22567, "Test Method for Determining the Glass Transition Temperature of Electrical Insulating Materials". The test results are shown in Table 1.

[0074] Table 1 Performance test results of polyimide films prepared in Examples 1-3 and Comparative Examples 1-7

[0075]

[0076] As can be seen from Table 1, due to the wide molecular weight distribution of polyamic acid prepared in Comparative Examples 1-4, the coexistence of low molecular weight oligomers and high molecular weight long chains will form defects and non-uniform structures during the imidization process. This leads to the weakening of intermolecular forces in the polyimide film, the increase of micro-defects, and the destruction of structural uniformity. Consequently, the mechanical, thermal stability, and density properties of the polyimide film decrease, the product qualification rate decreases, and the amount of waste adhesive increases.

[0077] Due to improper adjustment of the viscosity of the PDA solution added in the comparative example 5, the polymer viscosity was too high, making it difficult to form a film, resulting in incomplete degassing, difficulty in mixing the polyamic acid slurry and the hardener, and uneven imidization reaction. This reduced the performance of the polyimide film, decreased the product qualification rate, and increased the amount of waste adhesive.

[0078] In Comparative Example 6, different batches of polyamic acid slurry were not mixed. Due to the differences in the core physicochemical properties of polyamic acid slurry between different batches, these differences will be transferred through processing and reaction, directly leading to a decrease in the processing stability and performance consistency of polyimide film, ultimately resulting in a lower product qualification rate. This is especially true for high-end polyimide films, where the product qualification rate decreases and the amount of waste glue increases.

[0079] In Comparative Example 7, the impingement flow mixer 11 was not used to premix the polyamic acid slurry and the hardener, resulting in uneven mixing and local imbalance of hardener concentration in the system. Some areas had excessive hardener, while others had insufficient hardener, which caused uneven imidization reaction and disordered molecular chains. This led to structural defects in the polyimide film, resulting in decreased polyimide film performance, reduced product qualification rate, and increased waste adhesive.

Claims

1. A production system for polyamic acid slurry used in the chemical preparation of polyimide films, characterized in that, It includes a dianhydride silo (1) and a diamine silo (2). The dianhydride silo (1) is connected to a dianhydride weighing device (3) via a pipeline. The diamine silo (2) is connected to a diamine weighing device (4) via a pipeline. The dianhydride weighing device (3) and the diamine weighing device (4) are respectively connected to a first polymerization reactor (5) via pipelines. The first polymerization reactor (5) is connected to a solvent feed pipeline (501). The dianhydride weighing device (3) is also connected to a dianhydride solution mixing tank (6) via a pipeline. The dianhydride solution mixing tank (6) is connected to a solvent feed pipeline (501). 601); The outlets of the first polymerization reactor (5) and the dianhydride solution mixing tank (6) are respectively connected to the second polymerization reactor (7) via pipelines. The inlet of the second polymerization reactor (7) is connected to the third monomer solution mixing tank (8) via pipelines. The third monomer solution mixing tank (8) is connected to the solvent feed pipeline (3) (802); The outlet of the second polymerization reactor (7) is connected to the polyamic acid slurry temporary storage tank (9) via pipelines. The outlet of the polyamic acid slurry temporary storage tank (9) is connected to the deaerator (10) via pipelines. The deaerator (10) is connected to the... A vacuum pump (1001) is connected via a pipeline. The outlet of the deaerator (10) is connected via a pipeline to an impingement flow mixer (11). The inlet of the impingement flow mixer (11) is connected via a pipeline to a hardener mixing tank (12). The hardener mixing tank (12) is connected to a catalyst feed pipeline (1202), a dehydrating agent feed pipeline (1203), and a solvent feed pipeline (1204). The outlet of the impingement flow mixer (11) is connected via a pipeline to a needle-rod mixer (13). The first polymerization reactor (5) and the dianhydride solution mixing tank (6) are also connected. The first polymerization reactor (5), the second polymerization reactor (7), the third monomer solution mixing tank (8), the polyamic acid slurry temporary storage tank (9), the deaerator (10), the hardener mixing tank (12), and the needle-and-bar mixer (13) are all equipped with a stirrer (14); the first polymerization reactor (5), the dianhydride solution mixing tank (6), the second polymerization reactor (7), the third monomer solution mixing tank (8), the polyamic acid slurry temporary storage tank (9), the deaerator (10), the hardener mixing tank (12), and the needle-and-bar mixer (13) are respectively equipped with cooling jackets.

2. The production system for polyamic acid slurry for chemically preparing polyimide films as described in claim 1, characterized in that, There are two second polymerization reactors (7) connected in parallel; there are two polyamic acid slurry storage tanks (9) connected in parallel.

3. A method for producing polyamic acid slurry for chemically preparing polyimide films, characterized in that, Production is carried out using the polyamic acid slurry production system for chemically preparing polyimide films as described in claim 1 or 2, comprising the following steps: S1: Solid raw materials diamine, dianhydride and solvent are added to the first polymerization reactor (5) and polymerized at atmospheric pressure at -10~50℃ for 1~3h; wherein, dianhydride is added to the first polymerization reactor (5) in 3~5 portions, with an interval of 20~40min each time, and the amount of dianhydride added each time accounts for 20~33.4% of the total mass of dianhydride added to the first polymerization reactor (5); S2: After the reaction in the first polymerization reactor (5) is completed, the material is transferred to the second polymerization reactor (7). The dianhydride solution is added to the second polymerization reactor (7), and the addition time of the dianhydride solution is controlled to be >2h. Then, the third monomer solution is added dropwise, and the addition time of the third monomer solution is controlled to be >2h. When the viscosity of the material is 100~1000Pa·s, the dropwise addition is stopped. The polymerization reaction is carried out at atmospheric pressure at 40~60℃ for 3~7h. The third monomer is p-phenylenediamine, m-phenylenediamine or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. S3: After the second polymerization reactor (7) has completed the reaction of 2 to 5 batches, the material is transported to the polyamic acid slurry temporary storage tank (9) for storage and uniform mixing. The storage temperature is -15 to 0℃. Then, the uniformly mixed polyamic acid slurry is transported to the degasser (10) for vacuum degassing. The vacuum degassing temperature is -15 to 10℃ and the pressure is 10 to 1000 Pa. S4: After the catalyst, dehydrating agent and solvent are mixed into a hardener in the hardener mixing tank (12), they are added together with the vacuum degassed polyamic acid slurry into the impingement flow mixer (11) to complete the premixing; then it is transported to the needle bar mixer (13) for further mixing. The mixing temperature is -15~0℃. After uniform mixing, the polyamic acid slurry for chemical preparation of polyimide film is obtained.

4. The method for producing polyamic acid slurry for chemically preparing polyimide films as described in claim 3, characterized in that, In step S1, the dianhydride is pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, or hexafluoroisopropylphthalic anhydride; the diamine is 4,4'-diaminodiphenyl ether, 2,2'-bis(4-aminophenoxyphenyl)propane, or 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl; the solvent used in step S1, the solvent used in the dianhydride solution and the third monomer solution in step S2, and the solvent used in step S4 are dimethylacetamide, N,N-dimethylformamide, or N-methylpyrrolidone.

5. The method for producing polyamic acid slurry for chemically preparing polyimide films as described in claim 3, characterized in that, In step S1, the molar ratio of diamine to dianhydride is (1.1-1.5):

1. After the reaction in the first polymerization reactor (5) is completed, the viscosity of the material is 5000~30000 cP. The stirring speed of the first polymerization reactor (5) is 10~80 rpm.

6. The method for producing polyamic acid slurry for chemically preparing polyimide films as described in claim 3, characterized in that, In step S2, the concentration of the dianhydride solution is 10-20 wt.%, and the molar ratio of the dianhydride in the dianhydride solution to the dianhydride in step S1 is (0.4-1):1; the concentration of the third monomer solution is 10-15 wt.%.

7. The method for producing polyamic acid slurry for chemically preparing polyimide films as described in claim 3, characterized in that, In step S2, the stirring speed of the second polymerization reactor (7) is 10~120 rpm; nitrogen is purged during the discharge process of the second polymerization reactor (7), and the pressure inside the second polymerization reactor (7) is 0.1~0.25 MPaG.

8. The method for producing polyamic acid slurry for chemically preparing polyimide films as described in claim 3, characterized in that, In step S4, the catalyst is isoquinoline, pyridine or triethylamine, and the dehydrating agent is acetic anhydride, propionic anhydride or butyric anhydride; in the hardener, the catalyst concentration is 5~10wt.% and the dehydrating agent concentration is 20~50wt.%; the mass ratio of polyamic acid slurry to hardener is (2.5~3.5):1, and the stirring speed of the needle-bar mixer (13) is 5~20rpm.

9. A polyamic acid slurry for chemically preparing polyimide films, characterized in that, It is produced by the production method of polyamic acid slurry for chemical preparation of polyimide films as described in any one of claims 3-8.

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