Polyimide film prepared by chemical imidization method and continuous production system and process thereof

Abstract

The invention discloses a polyimide film prepared by a chemical imidization method and a continuous production system and process thereof, and relates to the technical field of polyimide films. The invention discloses a production process flow of continuous polyamide acid slurry preparation, film casting, chemical imidization, two-way stretching, heat setting and the like by taking diamine and dianhydride as raw materials, and overcomes the defects of unstable batch-to-batch quality of polyamide acid slurry, wide molecular weight distribution, poor stability and the like in the existing batch polymerization process technology. Product defects exist in polyimide film production, and the waste film rate is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyimide film, in particular to a polyimide film prepared by chemical imidization method, and a continuous production system and process thereof. BACKGROUND

[0002] Polyimide is a kind of polymer with imide (-CO-NH-CO-) structure in the main chain, which has high insulation, excellent mechanical properties, and is resistant to high and low temperature, radiation, high flame retardant, and high stability. In the electronic field, polyimide film has the best matching degree with modern electronic industry processing technology, and is the main material for producing flexible printed circuit board.

[0003] At present, more than 90% of the production capacity of domestic polyimide is mainly based on intermittent thermal imidization method, and the products are concentrated in the middle and low end applications. Compared with the production process of thermal imidization method, the production process of chemical imidization method has the advantages of low imidization temperature, high production efficiency, good film uniformity, and less bubbles or cracks, etc. The polyimide film prepared by chemical imidization method can be used in high-end fields such as flexible circuit board and copper-clad plate.

[0004] At present, the research focus of electronic grade polyimide film by chemical imidization method is mainly on the laboratory formula, and the process flow is mainly based on intermittent polymerization. There is no complete continuous process flow that can be industrialized.

[0005] Chinese patent CN106883431B discloses a preparation method of low water absorption polyimide film. Diamine monomer A and dianhydride monomer A are mixed in a polar solvent to obtain flexible polyamide acid resin solution A. Under the protection of N2, diamine monomer B and dianhydride monomer B are mixed in a polar solvent to obtain rigid polyamide acid resin solution B. Under the protection of N2, flexible polyamide acid resin solution A and rigid polyamide acid resin solution B are blended and stirred. When the viscosity of the reactants reaches 2000-3500 poise, the reaction is terminated. Finally, the accelerator and dehydrating agent are added and uniformly mixed, then cast into a film, and imidized to obtain a low water absorption polyimide film.

[0006] Chinese patent CN110117362B discloses a polyimide film and a preparation method thereof. A benzyl ester-containing aromatic dianhydride is combined with a general aromatic dianhydride, and an aromatic diamine is prepared by a polycondensation reaction to obtain a polyamide acid resin solution. Then, a chemical imidization reagent is added, and then the polyamide acid resin solution is coated into a film under the action of stretching and heating to form a polyimide film.

[0007] Chinese invention patent CN110951099B discloses a polyimide film and its preparation method and a base film of a radio frequency flexible printed circuit, which comprises preparing a polyamide acid resin solution, filtering and waiting for use, the solid content of the polyamide acid resin solution is controlled within the range of 15-35wt.%, the viscosity is controlled within the range of 10-45x10 4 mPa·s; a certain amount of polyamide acid resin solution is weighed, vacuum degassing is performed, and then imidization is performed to obtain a self-supporting semi-cured adhesive film; the self-supporting semi-cured adhesive film is fixed on a frame, the self-supporting semi-cured adhesive film is heated to a set temperature after being warmed, and then cooled to room temperature to obtain a polyimide primary film; the obtained polyimide primary film is subjected to annealing treatment to obtain a polyimide film. The above-mentioned polyimide film and its preparation method and the base film of the radio frequency flexible printed circuit are not limited to one preparation method, the prepared polyimide film has the characteristics of low dielectric constant, low dielectric loss, low thermal expansion coefficient and the like, has excellent comprehensive performance, and meets the use requirements of high-frequency flexible radio frequency printed circuits.

[0008] The above-mentioned patent mainly focuses on laboratory formula research, explores the influence of the formula on the performance of the product, the preparation process is mainly intermittent operation, and specific industrialized continuous complete process flow and process equipment are not involved, so that the quality of the prepared polyamide acid slurry is unstable between batches, the molecular weight distribution is wide, and finally the produced polyimide film has product defects, high waste film rate and the like. SUMMARY

[0009] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a polyimide film prepared by a chemical imidization method and a continuous production system and process thereof, which comprises a continuous polyamide acid slurry preparation, casting film formation, chemical imidization, two-way stretching, heat setting and the like production process using diamine and dianhydride as raw materials, and overcomes the problems of unstable quality between batches of polyamide acid slurry, wide molecular weight distribution, product defects, high waste film rate and the like in the production of polyimide film in the existing intermittent polymerization process technology.

[0010] The technical solution of the present application is: In a first aspect, the present application provides a continuous production system for polyimide film prepared by chemical imidization method, comprising a dianhydride bin and a diamine bin, the dianhydride bin is connected with a dianhydride weighing device through a pipeline, the dianhydride weighing device is connected with a dianhydride solution preparation tank through a pipeline, the dianhydride solution preparation tank is connected with a solvent feeding pipeline one; the diamine bin is connected with a diamine weighing device through a pipeline, the diamine weighing device is connected with a diamine solution preparation tank through a pipeline, the diamine solution preparation tank is connected with a solvent feeding pipeline two; the dianhydride solution preparation tank is connected with a cooler one through a pipeline, the diamine solution preparation tank is connected with a cooler two through a pipeline, the cooler one and the cooler two are respectively connected with an impinging stream mixer one through a pipeline, the impinging stream mixer one is connected with a first polymerization reactor through a pipeline, the first polymerization reactor is connected with an impinging stream mixer two through a pipeline, the inlet of the impinging stream mixer two is connected with a third monomer solution preparation tank through a pipeline, the third monomer solution preparation tank is connected with a solvent feeding pipeline three and a third monomer weighing device through a pipeline, the third monomer weighing device is connected with a third monomer bin through a pipeline; the outlet of the impinging stream mixer two is connected with a second polymerization reactor through a pipeline, the outlet of the second polymerization reactor is connected with a defoaming device through a pipeline, the outlet of the defoaming device is connected with an impinging stream mixer three through a pipeline, the inlet of the impinging stream mixer three is connected with a hardener preparation tank through a pipeline, the hardener preparation tank is connected with a catalyst feeding pipeline, a dehydrating agent feeding pipeline and a solvent feeding pipeline four, the outlet of the impinging stream mixer three is connected with a pin-bar mixer; the outlet of the pin-bar mixer is connected with a flow coater, the outlet of the flow coater is connected with a steel belt dryer, the outlet of the steel belt dryer is connected with a stretcher; the first polymerization reactor and the second polymerization reactor adopt a tubular reactor or a double screw reactor.

[0011] Preferably, the dianhydride solution preparation tank, the diamine solution preparation tank, the third monomer solution preparation tank, the hardener preparation tank and the pin-bar mixer are all provided with a stirrer.

[0012] Preferably, the outer parts of the dianhydride solution preparation tank, the diamine solution preparation tank, the third monomer solution preparation tank, the first polymerization reactor, the second polymerization reactor, the defoaming device, the hardener preparation tank and the pin-bar mixer are respectively provided with a cooling jacket.

[0013] In a second aspect, the present application provides a continuous production process for polyimide film prepared by chemical imidization method, which is produced by the above-mentioned continuous production system for polyimide film prepared by chemical imidization method, comprising the following steps: S1: after the solid raw materials dianhydride and diamine are weighed, they are respectively put into the dianhydride solution preparation tank and the diamine solution preparation tank together with the solvent to prepare dianhydride solution and diamine solution; S2: the dianhydride solution and the diamine solution are cooled to -10~0℃ and then delivered to the impinging stream mixer 1 for mixing, and after mixing, the mixture is delivered to the first polymerization reactor for polymerization at -10~50℃ for 1~3h; S3: the material after the reaction in the first polymerization reactor is delivered to the impinging stream mixer 2 for mixing with the third monomer solution in the third monomer solution preparation tank, and after mixing, the mixture is delivered to the second polymerization reactor for polymerization at 0~40℃ for 2~5h to obtain a polyamic acid slurry; S4: the polyamic acid slurry is delivered to a deaerator for deaeration; S5: the catalyst, the dehydrating agent and the solvent are prepared into a hardener in the hardener preparation tank, and then the hardener is mixed with the deaerated polyamic acid slurry in the impinging stream mixer 3 for premixing, and then the mixture is delivered to a pin-bar mixer for further mixing; S6: after mixing, the mixture is delivered to the die head of a casting machine, extruded through the film lip of the die head, and then a liquid film is formed on the casting steel belt to obtain a polyamic acid gel film; the polyamic acid gel film is delivered to a steel belt dryer, the solvent is evaporated, and the polyamic acid is dehydrated and cyclized to form a polyimide film; the polyimide film is delivered to a stretching machine, and the film is sequentially subjected to longitudinal stretching, transverse stretching and heat setting to complete the remaining imidization, thereby obtaining the final polyimide film.

[0014] Preferably, in step S1, the dianhydride is pyromellitic dianhydride (PMDA), 2,3,3',4'-biphenyl tetracarboxylic dianhydride (BPDA) or hexafluoroisopropyl phthalic anhydride (6FDA); the diamine is 4,4'-oxydianiline (ODA), 2,2'-bis(4-aminophenoxyphenyl)propane (BAPP) or 4,4'-diamino-2,2'-bistrifluoromethyl biphenyl (TFMB); the concentration of the dianhydride solution and the diamine solution is 10~30wt.%; the solvent used in step S1, the solvent used in the third monomer solution preparation tank in step S3 and the solvent used in step S5 are dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) or N-methyl pyrrolidone (NMP).

[0015] Preferably, in step S2, the molar ratio of the diamine to the dianhydride is (0.4~0.9):1; after the reaction in the first polymerization reactor, the viscosity of the material is 5000~30000cP.

[0016] Preferably, in step S3, 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.%; the molar ratio of the third monomer to the dianhydride is (0.1-0.6):1; after the second polymerization reactor is finished, the viscosity of the material is 100-1000 Pa·s; in step S4, the defoaming temperature is -15-10℃, and the defoaming pressure is 10-1000 Pa.

[0017] Preferably, in step S5, the catalyst is isoquinoline, pyridine or triethylamine, and the dehydrating agent is acetic anhydride, propionic anhydride or butyric anhydride; in the hardening agent, the concentration of the catalyst is 5-10 wt.%, and the concentration of the dehydrating agent is 30-50 wt.%; the mass ratio of the polyamic acid slurry to the hardening agent is (2.5-3.5):1.

[0018] Preferably, in step S6, the steel belt dryer is divided into three drying sections, which are drying section one for heating from 0℃ to 50-80℃, drying section two for continuously heating to 80-120℃, and drying section three for continuously heating to 120-200℃; the inlet air temperature of the steel belt air duct is 120-195℃, and the inlet air temperature of the lower air duct is 150-220℃.

[0019] In a third aspect, the present application provides a polyimide film prepared by the chemical imidization method.

[0020] Compared with the prior art, the present application has the following beneficial effects: 1. According to the reaction characteristics of polyamic acid, the present application adopts a closed feeding method, uses a first polymerization reactor and a second polymerization reactor in the form of a plug flow reactor, realizes the industrialized continuous production of polyamic acid slurry, which is a precursor of polyimide film, improves the production operation efficiency, and matches with the continuous film forming process such as casting, chemical imidization, biaxial stretching and heat setting, etc., to form a continuous production process of polyimide film prepared by the chemical imidization method. The process uses a first polymerization reactor and a second polymerization reactor in the form of a plug flow reactor, effectively reduces the molecular weight distribution width of the polyamic acid slurry, and improves the product quality of the polymer precursor; and the process fully connects and cooperates with the continuous film forming process, can efficiently and high-quality prepare the polyimide film prepared by the chemical imidization method, and overcomes the problems of unstable quality between batches of polyamic acid slurry, wide molecular weight distribution, product defects, high waste film rate, etc. in the existing batch polymerization process, fundamentally solves the differences between batches of polyamic acid slurry, improves the quality of the polyimide film, and reduces the waste film rate.

[0021] 2. In the process of the present application, diamine and dianhydride are first prepared into a solution, which is introduced into the first polymerization reactor in the form of a solution, so that the first polymerization reaction is carried out under homogeneous conditions, effectively improving the reaction efficiency; an impinging stream mixer is arranged at the inlet of the first polymerization reactor, so that the diamine solution and the dianhydride solution are quickly mixed, solving the problem of uneven mixing of solid feed.

[0022] 3. The present application fully describes the continuous production process of polyimide film, which is universal, and can produce polyimide film products of various grades by replacing dianhydride or diamine raw materials. The process is simple and effective, and has obvious effect on improving product quality, and is easy to popularize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the continuous production system of the polyimide film prepared by the chemical imidization method of the present application.

[0024] In the figure, 1 is a dianhydride bin, 2 is a diamine bin, 3 is a dianhydride weighing device, 4 is a dianhydride solution preparation tank, 401 is a solvent feed pipeline one, 402 is a dianhydride solution metering pump, 5 is a diamine weighing device, 6 is a diamine solution preparation tank, 601 is a solvent feed pipeline two, 602 is a diamine solution metering pump, 7 is a cooler one, 8 is a cooler two, 9 is an impinging stream mixer one, 10 is a first polymerization reactor, 11 is an impinging stream mixer two, 12 is a third monomer solution preparation tank, 1201 is a solvent feed pipeline three, 1202 is a third monomer solution metering pump, 13 is a third monomer weighing device, 1301 is a third monomer bin, 14 is a second polymerization reactor, 1401 is a polyamic acid slurry metering pump, 15 is a defoaming device, 1501 is a vacuum pump, 1502 is a defoaming polyamic acid slurry metering pump, 16 is an impinging stream mixer three, 17 is a hardener preparation tank, 1701 is a catalyst feed pipeline, 1702 is a dehydrating agent feed pipeline, 1703 is a solvent feed pipeline four, 1704 is a hardener metering pump, 18 is a pin-bar mixer, 19 is a casting machine, 20 is a steel belt dryer, and 21 is a stretching machine.

[0025] Figure 2 is a structural schematic diagram of the batch production system of the polyimide film prepared by the chemical imidization method of Comparative Example 4.

[0026] In the diagram, 22. Dianone silo A; 23. Diamine silo A; 24. Dianone weighing device A; 25. Diamine weighing device A; 26. First polymerization reactor A; 2601. Solvent feed line 1 A; 2602. First polymer transfer pump A; 27. Dianone solution mixing tank A; 2701. Solvent feed line 2 A; 2702. Dianone solution transfer pump A; 28. Second polymerization reactor A; 2801. Polyamic acid slurry transfer pump A; 29. ​​Third monomer solution mixing tank A; 2901. Three monomer solution transfer pump A; 2902, Solvent feed line three A; 30, Deaerator A; 3001, Vacuum pump A; 3002, Deaerated polyamic acid slurry transfer pump A; 31, Impingement flow mixer A; 32, Hardener mixing tank A; 3201, Hardener transfer pump A; 3202, Catalyst feed line A; 3203, Dehydrating agent feed line A; 3204, Solvent feed line four A; 35, Needle bar mixer A; 36, Casting machine A; 37, Steel strip dryer A; 38, Stretching machine A. Detailed Implementation

[0027] 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.

[0028] like Figure 1 As shown in the following embodiments, the continuous production system for polyimide films prepared by chemical imidization 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 dianhydride weighing device 3 is connected to a dianhydride solution mixing tank 4 via a pipeline. The dianhydride solution mixing tank 4 is connected to a solvent inlet pipeline 401. The diamine silo 2 is connected to a diamine weighing device 5 via a pipeline. The diamine weighing device 5 is connected to a diamine solution mixing tank 6 via a pipeline. The diamine solution mixing tank 6 is connected to a solvent inlet pipeline 601. Both the dianhydride solution mixing tank 4 and the diamine solution mixing tank 6 are equipped with stirrers. Two dianhydride solution mixing tanks 4 and 6 are connected in parallel, one for use and one for standby.

[0029] like Figure 1 As shown, the dianhydride solution mixing tank 4 is connected to a cooler 7 via a pipeline, and a dianhydride solution metering pump 402 is installed on the pipeline; the diamine solution mixing tank 6 is connected to a cooler 8 via a pipeline, and a diamine solution metering pump 602 is installed on the pipeline; cooler 7 and cooler 8 are respectively connected to an impingement flow mixer 9 via pipelines, and impingement flow mixer 9 is connected to a first polymerization reactor 10 via pipelines. Solid raw materials dianhydride and diamine are first mixed into dianhydride solution and diamine solution in the dianhydride solution mixing tank 4 and the diamine solution mixing tank 6, respectively. After cooling, they enter the impingement flow mixer 9 for mixing. After being mixed evenly, they enter the first polymerization reactor 10 in solution form for the first polymerization reaction.

[0030] As shown in Figure 1 , the first polymerization reactor 10 is connected with an impinging stream mixer two 11 through a pipeline, the inlet of the impinging stream mixer two 11 is connected with a third monomer solution preparation tank 12 through a pipeline, and a third monomer solution metering pump 1202 is arranged on the pipeline; the third monomer solution preparation tank 12 is connected with a solvent feeding pipeline three 1201, the third monomer solution preparation tank 12 is provided with a stirrer and is connected with a third monomer weighing device 13 through a pipeline, and the third monomer weighing device 13 is connected with a third monomer bin 1301 through a pipeline; the outlet of the impinging stream mixer two 11 is connected with a second polymerization reactor 14. Wherein, two third monomer solution preparation tanks 12 are arranged in parallel, one is used and the other is standby. The material after the reaction of the first polymerization reactor 10 enters the impinging stream mixer two 11, is mixed with the third monomer solution, enters the second polymerization reactor 14 for the second polymerization reaction after the mixing is completed, and polyamic acid slurry is obtained.

[0031] As shown in Figure 1 , the outlet of the second polymerization reactor 14 is connected with a defoaming device 15 through a pipeline, a polyamic acid slurry metering pump 1401 is arranged on the pipeline, and the defoaming device 15 is connected with a vacuum pump 1501 through a pipeline; the outlet of the defoaming device 15 is connected with an impinging stream mixer three 16 through a pipeline, and a defoamed polyamic acid slurry metering pump 1502 is arranged on the pipeline; the inlet of the impinging stream mixer three 16 is connected with a hardener preparation tank 17 through a pipeline, and a hardener metering pump 1704 is arranged on the pipeline; the hardener preparation tank 17 is connected with a catalyst feeding pipeline 1701, a dehydrating agent feeding pipeline 1702 and a solvent feeding pipeline four 1703, the hardener preparation tank 17 is provided with a stirrer, and the outlet of the impinging stream mixer three 16 is connected with a needle bar mixer 18 through a pipeline, and the needle bar mixer 18 is provided with a stirrer. The catalyst, the dehydrating agent and the solvent are prepared into a hardener in the hardener preparation tank 17, and then are mixed with the defoamed polyamic acid slurry, are premixed in the impinging stream mixer three 16, and then are further mixed in the needle bar mixer 18, so that the polyamic acid slurry for preparing a polyimide film is obtained.

[0032] As shown in Figure 1As shown, the outlet of the needle rod mixer 18 is connected with a casting machine 19 through a pipeline, the casting machine 19 is connected with a steel belt dryer 20 through a pipeline, and the outlet of the steel belt dryer 20 is connected with a stretcher 21 through a pipeline. The polyamide acid slurry is delivered to the die head of the casting machine 19, and after being extruded through the film lip of the die head, a liquid film with uniform thickness is formed on the casting steel belt. The steel belt is a mirror surface stainless steel. After casting, the polyamide acid gel film containing a large amount of solvent is sent to the steel belt dryer 20, and clean and dry air is preheated and then enters the upper and lower drying channels. The hot air flows in the opposite direction to the running direction of the steel belt. The film runs on the steel belt for one cycle, the solvent evaporates, the polyamide acid dehydrates and cyclizes to complete most of the chemical imidization, and the polyimide film is formed. After drying, the polyimide film is peeled off from the steel belt and enters the stretcher 21. After longitudinal stretching, it is stretched transversely, and the width of the polyamide acid gel film is gradually stretched to the width before longitudinal stretching by a needle plate or a chain clip; after transverse stretching, it enters the heat setting zone to complete the remaining imidization and produce a 12.5 μm thick polyimide film.

[0033] The first polymerization reactor 10 is a tubular reactor, and the second polymerization reactor 14 is a double-screw reactor. The material flows in the first polymerization reactor 10 and the second polymerization reactor 14 in a plug flow manner, which fully connects and cooperates with the subsequent film drawing device such as the casting machine 19 to realize the continuous production of the polyimide film. In addition, the outer parts of the dianhydride solution preparation tank 4, the diamine solution preparation tank 6, the third monomer solution preparation tank 12, the first polymerization reactor 10, the second polymerization reactor 14, the defoaming device 15, the hardener preparation tank 17 and the needle rod mixer 18 are respectively provided with cooling jackets. The operating temperature of each device is controlled by circulating chilled water in the cooling jackets.

[0034] Example 1 The continuous production process of the polyimide film prepared by the chemical imidization method in this example includes the following steps: S1: The barreled ODA and PMDA are respectively sealed and put into the diamine bin 2 and the dianhydride bin 1, PMDA and solvent DMF are added to the dianhydride solution preparation tank 4, and ODA and solvent DMF are added to the diamine solution preparation tank 6, so that the concentrations of the PMDA solution and the ODA solution are both 15 wt.%.

[0035] S2: The prepared ODA solution and PMDA solution are respectively delivered to cooler one 7 and cooler two 8 by the diamine solution metering pump 602 and the dianhydride solution metering pump 402, and then are cooled to 0°C and are fed into the impinging stream mixer one 9. The flow rate of the PMDA solution is 80 kg / h, and the flow rate of the ODA solution is 51.4 kg / h. After being preliminarily mixed uniformly in the impinging stream mixer one 9, the mixture is fed into the tubular reactor, the reaction temperature is controlled at 45°C, the residence time of the polymer in the tubular reactor is 2 h, and after the reaction is completed, the viscosity of the material is 10000 cP.

[0036] S3: The material after the reaction in the tubular reactor is delivered to the impinging stream mixer two 11, and is mixed with 15 wt.% of the PDA solution (the solvent is DMF), and the flow rate of the PDA solution is 16.5 kg / h. After the mixing is completed, the mixture is fed into the double screw reactor to react, the reaction temperature is controlled at 35°C, the stirring speed of the double screw reactor is 100 rmp, the residence time of the polymer is 3 h, and after the reaction is completed, the viscosity of the material is 500 Pa·s, and the polyamic acid slurry is obtained.

[0037] S4: The polyamic acid slurry is delivered to the deaerator 15 by the polyamic acid slurry metering pump 1401 to be deaerated, the deaeration temperature is 0°C, and the deaeration pressure is 100 Pa.

[0038] S5: The isoquinoline, acetic anhydride and DMF are prepared into the hardener in the hardener preparation tank 17, wherein the concentration of the isoquinoline is 6.34 wt.% and the concentration of the acetic anhydride is 47.29 wt.%. The hardener and the deaerated polyamic acid slurry are fed into the impinging stream mixer three 16 to be premixed, wherein the flow rate of the hardener is 49.3 kg / h and the flow rate of the deaerated polyamic acid slurry is 147.9 kg / h. Then, the premixed material is delivered to the pin-bar mixer 18 to be further mixed.

[0039] S6: The uniformly mixed material is delivered to the die head of the casting machine 19, is extruded through the film lip of the die head, and then is formed into a liquid film with uniform thickness on the casting steel belt to obtain the polyamic acid gel film. The polyamic acid gel film is delivered to the steel belt dryer 20, the solvent is evaporated, the polyamic acid is dehydrated and cyclized to complete the partial chemical imidization to form the polyimide film. The steel belt dryer 20 is divided into three drying sections, which are drying section one with the temperature rising from 0°C to 60°C, drying section two with the temperature continuously rising to 100°C and drying section three with the temperature continuously rising to 150°C. The air inlet temperature of the steel belt air duct is 175°C, and the air inlet temperature of the lower air duct is 170°C. The polyimide film is fed into the stretcher 21 to be subjected to longitudinal stretching, transverse stretching and heat setting in sequence, and the remaining imidization is completed, and the final polyimide film is obtained.

[0040] Example 2 The continuous production process of the polyimide film prepared by the chemical imidization method of the embodiment comprises the following steps: S1: The TFMB and 6FDA in barrels are respectively sealed and put into the diamine bin 2 and the dianhydride bin 1, 6FDA and the solvent DMAc are added into the dianhydride solution preparation tank 4, and TFMB and the solvent DMAc are added into the diamine solution preparation tank 6, so that the concentrations of the 6FDA solution and the TFMB solution are both 30wt.%.

[0041] S2: The prepared TFMB solution and 6FDA solution are respectively transported to the cooler one 7 and the cooler two 8 through the diamine solution metering pump 602 and the dianhydride solution metering pump 402, and then enter the impinging stream mixer one 9 after being cooled to-5℃. The flow rate of the 6FDA solution is 173.3kg / h, and the flow rate of the TFMB solution is 50kg / h. After being uniformly mixed in the impinging stream mixer one 9, the mixture enters the tubular reactor, the reaction temperature is controlled at 50℃, the residence time of the polymer in the tubular reactor is 1h, and after the reaction is completed, the viscosity of the material is 30000cP.

[0042] S3: The material after the reaction of the tubular reactor is transported to the impinging stream mixer two 11 and mixed with the 12wt.% BDAF solution (the solvent is DMAc), the flow rate of the BDAF solution is 303.5kg / h; after the mixing is completed, the mixture enters the double screw reactor for reaction, the reaction temperature is controlled at 40℃, the stirring speed of the double screw reactor is 50rmp, the residence time of the polymer is 2h, after the reaction is completed, the viscosity of the material is 1000Pa·s, and the polyamic acid slurry is obtained.

[0043] S4: The polyamic acid slurry is transported to the defoaming device 15 through the polyamic acid slurry metering pump 1401 for defoaming, the defoaming temperature is 10℃, and the defoaming pressure is 1000Pa.

[0044] S5: Pyridine, propionic anhydride and DMAc are prepared into a hardening agent in the hardening agent preparation tank 17, wherein the concentration of pyridine is 5.11wt.% and the concentration of propionic anhydride is 40.14wt.%; the hardening agent and the defoamed polyamic acid slurry are added into the impinging stream mixer three 16 together to complete the premixing. The flow rate of the hardening agent is 210.73kg / h, and the flow rate of the defoamed polyamic acid slurry is 527kg / h. Then the premixed material is transported to the pin bar mixer 18 for further mixing.

[0045] S6: The mixed material is transported to the die head of the casting machine 19, and after being extruded through the film lip of the die head, a liquid film with uniform thickness is formed on the casting steel belt to obtain a polyamic acid gel film. The polyamic acid gel film is transported to the steel belt dryer 20, the solvent is evaporated, and the polyamic acid is dehydrated and cyclized to complete partial chemical imidization to form a polyimide film. The steel belt dryer 20 is divided into three drying sections, which are drying section one with a temperature rising from 0°C to 80°C, drying section two with a temperature rising to 120°C, and drying section three with a temperature rising to 200°C; the air inlet temperature of the steel belt air duct is 195°C, and the air inlet temperature of the lower air duct is 220°C. The polyimide film enters the stretching machine 21, and after longitudinal stretching, transverse stretching and heat setting, the remaining imidization is completed, and the final polyimide film is obtained.

[0046] Example 3 The continuous production process of the polyimide film prepared by the chemical imidization method in this example includes the following steps: S1: The BAPP and BPDA in barrels are respectively sealed and put into the diamine bin 2 and the dianhydride bin 1, BPDA and the solvent NMP are added to the dianhydride solution preparation tank 4, and BAPP and the solvent NMP are added to the diamine solution preparation tank 6, so that the concentrations of the BAPP solution and the BPDA solution are both 10wt.%.

[0047] S2: The prepared BAPP solution and BPDA solution are respectively transported to the cooler one 7 and the cooler two 8 through the diamine solution metering pump 602 and the dianhydride solution metering pump 402, and then cooled to-10°C and then entered into the impinging stream mixer one 9. The flow rate of the BPDA solution is 300kg / h, and the flow rate of the BAPP solution is 376.7kg / h. After being preliminarily mixed uniformly in the impinging stream mixer one 9, the material is transported into the tubular reactor, the reaction temperature is controlled at-10°C, the residence time of the polymer in the tubular reactor is 3h, and after the reaction is completed, the viscosity of the material is 5000cP.

[0048] S3: The material after the reaction in the tubular reactor is transported to the impinging stream mixer two 11 and mixed with 10wt.% MPD solution (the solvent is NMP), and the flow rate of the MPD solution is 12kg / h; after the mixing is completed, the material is transported into the double screw reactor for reaction, the reaction temperature is controlled at 0°C, the stirring speed of the double screw reactor is 50rmp, the residence time of the polymer is 5h, and after the reaction is completed, the viscosity of the material is 100Pa·s, and the polyamic acid slurry is obtained.

[0049] S4: The polyamic acid slurry is transported to the deaerator 15 through the polyamic acid slurry metering pump 1401 for deaeration, the deaeration temperature is-15°C, and the deaeration pressure is 10Pa.

[0050] S5: Triethylamine, butyric anhydride and NMP are mixed into hardener in hardener preparation tank 17, wherein the concentration of triethylamine is 10 wt.%, and the concentration of butyric anhydride is 32.23 wt.%; the hardener is added into impinging stream mixer three 16 together with the defoamed polyamic acid slurry to complete premixing. The flow rate of the hardener is 294.71 kg / h, and the flow rate of the defoamed polyamic acid slurry is 1031 kg / h. Then the premixed material is transported to pin-bar mixer 18 for further mixing.

[0051] S6: The uniformly mixed material is transported to the die head of casting machine 19, and after extrusion through the film lip of the die head, a liquid film with uniform thickness is formed on the casting steel belt to obtain a polyamic acid gel film. The polyamic acid gel film is transported to steel belt dryer 20, and the solvent is evaporated to complete the dehydration and cyclization of polyamic acid and form a polyimide film. Steel belt dryer 20 is divided into three drying sections, which are drying section one with temperature rising from 0°C to 50°C, drying section two with temperature rising to 80°C, and drying section three with temperature rising to 120°C; the inlet air temperature of the steel belt air duct is 120°C, and the inlet air temperature of the lower air duct is 150°C. The polyimide film enters the stretching machine 21, and sequentially undergoes longitudinal stretching, transverse stretching and heat setting to complete the remaining imidization, and the final polyimide film is obtained.

[0052] Comparative Example 1 The difference from Example 1 is that the third monomer solution metering pump 1202 on the pipeline between the third monomer solution preparation tank 12 and the impinging stream mixer two 11 is closed, a new pipeline is added between the third monomer solution preparation tank 12 and the impinging stream mixer one 9, a new third monomer solution metering pump is installed on the pipeline, and the third monomer solution metering pump is opened to mix the PDA solution with the ODA solution and the PMDA solution in the impinging stream mixer one 9, and then the mixture is introduced into the tubular reactor for polymerization reaction.

[0053] The polydispersity index (PDI) of the polyamic acid product obtained after the completion of all polymerization reactions in Example 1 and Comparative Example 1 is tested. The PDI of the product in Example 1 is 1.5, and the PDI of the product in Comparative Example 1 is 1.8. It can be seen from the comparison that the molecular weight distribution of the product obtained in Example 1 is narrower. This is because in Comparative Example 1, the diamine, dianhydride and third monomer are added into the tubular reactor at one time, which is prone to cause large local reaction rate difference, resulting in too fast growth of part of the chain segments and too slow growth of part of the chain segments, and finally forming a wider molecular weight distribution. The step-by-step polymerization in Example 1 can control the reaction process in each stage by decomposing the reaction process into different stages in an orderly manner, reducing the uneven chain growth phenomenon caused by the drastic change of the reaction environment, and effectively narrowing the molecular weight distribution of the product.

[0054] Comparative Example 2 The difference from Example 1 is that the third monomer solution metering pump 1202 and the polyamic acid slurry metering pump 1401 are closed, a pipeline is added between the impinging stream mixer two 11 and the deaerator 15, a new polyamic acid slurry metering pump is installed on the pipeline, the polyamic acid slurry metering pump is opened, and the material reacted in the tubular reactor is directly introduced into the deaerator 15 for deaeration treatment after being mixed by the impinging stream mixer two 11, without adding the third monomer solution for the second polymerization reaction.

[0055] The PDI of the polyamic acid product obtained after all the polymerization reactions in Comparative Example 2 is 1.7, and it can be seen by comparison that the polyamic acid product of Example 1 has a narrower molecular weight distribution. 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 the PDA solution is added in the double screw reactor reaction stage, it preferentially combines with the overgrown high molecular weight active chain ends in the system, and terminates the further growth of this part of the chain through the rigid short-chain structure; at the same time, PDA can also combine with low molecular weight active chains to moderately extend their chain length, ultimately achieving the bidirectional regulation of inhibiting high molecular weight chains and completing low molecular weight chains, thereby narrowing the range of molecular weight distribution.

[0056] Comparative Example 3 The difference from Example 1 is that in step S2, the flow rate of the ODA solution is 70 kg / h; and in step S3, the flow rate of the PDA solution is 2.6 kg / h.

[0057] The PDI of the polyamic acid product obtained after all the polymerization reactions in Comparative Example 3 is 1.7, and it can be seen by comparison that the polyamic acid product of Example 1 has a narrower molecular weight distribution. This is because in Comparative Example 1, the ratio of the diamine ODA to the dianhydride PMDA added in the first polymerization kettle 10 is imbalanced, and the amount of ODA added is too large, resulting in a polymer viscosity as low as 1000 cP in the tubular reactor, and simultaneously resulting in a decrease in the amount of PDA added in the double screw reactor, which weakens the regulation of the third monomer on product performance. Because the ratio of the key monomers is imbalanced in the stepwise polymerization process, even if a stepwise polymerization process is used, the improper ratio of raw materials in a certain stage will still result in a decrease in chain growth uniformity, making the PDI of the polyamic acid product high.

[0058] Comparative Example 4 Comparative Example 4 uses a batch production system for preparing polyimide films by chemical imidization, as shown in Figure 2As shown, it comprises dianhydride silo A 22 and diamine silo A 23, the dianhydride silo A 22 is connected with dianhydride weighing device A 24 through a pipeline, the diamine silo A 23 is connected with diamine weighing device A 25 through a pipeline, the dianhydride weighing device A 24 and the diamine weighing device A 25 are respectively connected with the first polymerization reactor A 26 (adopting vertical stirring kettle) through a pipeline, and the first polymerization reactor A 26 is connected with solvent feeding pipeline one A 2601. The weighed raw materials dianhydride and diamine are added into the first polymerization reactor A 26 in solid form, and the polymerization reaction is carried out in the solvent.

[0059] The dianhydride weighing device A 24 is also connected with the dianhydride solution blending tank A 27 through a pipeline, and the dianhydride solution blending tank A 27 is connected with solvent feeding pipeline two A 2701. The outlet of the first polymerization reactor A 26 is connected with the second polymerization reactor A 28 (adopting vertical stirring kettle) through a pipeline, and a first polymer conveying pump A 2602 is arranged on the pipeline; the outlet of the dianhydride solution blending tank A 27 is connected with the second polymerization reactor A 28 through a pipeline, and a dianhydride solution conveying pump A 2702 is arranged on the pipeline; the inlet of the second polymerization reactor A 28 is connected with the third monomer solution blending tank A 29 through a pipeline, and a third monomer solution conveying pump A 2901 is arranged on the pipeline; and the third monomer solution blending tank A 29 is connected with solvent feeding pipeline three A 2902. The material after the reaction of the first polymerization reactor A 26 is conveyed to the second polymerization reactor A 28 through the first polymer conveying pump A 2602, the dianhydride solution blended by the dianhydride solution blending tank A 27 is conveyed to the second polymerization reactor A 28 through the dianhydride solution conveying pump A 2702, and the solvent is added into the second polymerization reactor A 28 through the solvent feeding pipeline three A 2902 to carry out the second polymerization reaction. Among them, two second polymerization reactors A 28 are arranged in parallel, one is used and the other is reserved.

[0060] Meanwhile, the outlet of the second polymerization reactor A 28 is connected with a defoaming device A 30 through a pipeline, and a polyamide acid slurry conveying pump A 2801 is arranged on the pipeline, and the defoaming device A 30 is connected with a vacuum pump A 3001 through a pipeline. The material after the reaction of the second polymerization reactor A 28 is conveyed to the defoaming device A 30 through the polyamide acid slurry conveying pump A 2801 for vacuum defoaming. The outlet of the defoaming device A 30 is connected with an impinging stream mixer A 31 through a pipeline, and a defoamed polyamide acid slurry conveying pump A 3002 is arranged on the pipeline; the inlet of the impinging stream mixer A 31 is connected with a hardener preparation tank A 32 through a pipeline, and a hardener conveying pump A 3201 is arranged on the pipeline. The hardener preparation tank A 32 is connected with a catalyst feeding pipeline A 3202, a dehydrating agent feeding pipeline A 3203 and a solvent feeding pipeline A 3204, and the outlet of the impinging stream mixer A 31 is connected with a pin-bar mixer A 35. The first polymerization reactor A 26, the dianhydride solution preparation tank A 27, the second polymerization reactor A 28, the third monomer solution preparation tank A 29, the defoaming device A 30, the hardener preparation tank A 32 and the pin-bar mixer A 35 are all provided with stirrers. The catalyst, the dehydrating agent and the solvent are prepared into a hardener in the hardener preparation tank A 32, and then the defoamed polyamide acid slurry is pre-mixed in the impinging stream mixer A 31 and then further mixed in the pin-bar mixer A 35, and the polyamide acid slurry is obtained after discharging. The subsequent film-drawing devices such as the casting machine A 36, the steel-belt drying machine A 37 and the stretching machine A 38 are the same as the film-drawing devices such as the casting machine 19, the steel-belt drying machine 20 and the stretching machine 21 in Example 1, and will not be described here.

[0061] The intermittent production method of the polyimide film prepared by the chemical imidization method of Comparative Example 4 includes the following steps: S1: 255 kg of DMF was added to the first polymerization reactor A 26; the barreled ODA and PMDA were respectively sealed and put into the diamine bin A 23 and the dianhydride bin A 22, 25.9 kg of ODA and 18.8 kg of PMDA were weighed and put into the first polymerization reactor A 26 for reaction, the reaction temperature was controlled at 45°C, the stirring speed was 80 rmp, the reaction time was 2.5 h, and after the reaction, the viscosity of the material was 30000 cP.

[0062] S2: The material after the reaction in the first polymerization reactor A 26 was transported to the second polymerization reactor A 28 by the first polymer transport pump A 2602. 125.3 kg of PMDA solution (solvent: DMF) with a concentration of 15 wt.% was added dropwise to the second polymerization reactor A 28 at a flow rate of 50.2 kg / h. Then, 30.67 kg of PDA solution (solvent: DMF) with a concentration of 15 wt.% was added dropwise to the second polymerization reactor A 28 at a flow rate of 14.56 kg / h. When the PDA solution reached 95 wt.%, the addition was switched to drop-by-drop addition. When the viscosity of the polymer reached 300 Pa·s, the addition of the PDA solution was stopped. The reaction temperature of the second polymerization reactor A 28 was controlled at 50°C, the stirring speed was 100 rpm, and the reaction time was 5 h.

[0063] S3: After the completion of the second polymerization reaction, the reaction material was transported to the deaerator A 30 by the polyamide acid slurry transport pump A 2801 for deaeration. The deaerator A 30 was connected to the vacuum pump A 3001 for vacuum pumping. The operating pressure of the deaerator A 30 was 500 Pa, and the operating temperature was 0°C.

[0064] S4: 36.4 kg of isoquinoline, 145.6 kg of acetic anhydride, and 546 kg of DMF were added to the hardener preparation tank A 32 to prepare the hardener. Then, the hardener was transported to the impinging stream mixer A 31 by the hardener transport pump A 3201, and was preliminarily mixed with 1822.68 kg of the polyamide acid slurry after deaeration by high-speed collision. Then, the mixture was further mixed in the pin-bar mixer A 35 at a stirring speed of 10 rpm, and the mixing temperature was controlled at 0°C.

[0065] S5: The uniformly mixed material was transported to the die of the casting machine A 36, and was extruded through the film lip of the die to form a liquid film with uniform thickness on the casting steel belt, thereby obtaining a polyamide acid gel film. The polyamide acid gel film was transported to the steel belt dryer A 37, and the solvent was evaporated to complete the dehydration and cyclization of the polyamide acid to form a polyimide film. The steel belt dryer A 37 was divided into three drying sections, i.e., a drying section one with a temperature increasing from 0°C to 60°C, a drying section two with a temperature increasing to 100°C, and a drying section three with a temperature increasing to 150°C. The air inlet temperature of the steel belt air duct was 175°C, and the air inlet temperature of the lower air duct was 170°C. The polyimide film was subjected to longitudinal stretching, transverse stretching, and heat setting in the stretcher A 38 in sequence to complete the residual imidization, thereby obtaining the final polyimide film.

[0066] The polyimide films produced in Examples 1-3 and Comparative Examples 1-4 were tested, wherein the coefficient of thermal expansion was tested in accordance with the standard test method for linear thermal expansion of plastics using quartz dilatometer in the range of -30°C and 30°C (ASTM D696), the tensile strength was tested in accordance with the standard test method for tensile properties of thin plastic sheeting (ASTM D882), and the glass transition temperature was tested in accordance with the test method for determining glass transition temperature of electrical insulating materials (GB / T 22567). The test results are shown in Table 1: Table 1 Test results of properties of polyimide films produced in Examples 1-3 and Comparative Examples 1-4

[0067] As can be seen from Table 1, since the polyamide acid prepared in Comparative Example 1-3 has a wide molecular weight distribution, low molecular weight oligomers and high molecular weight long chains coexist, and defects and non-uniform structures are formed during the imidization process, which leads to weakening of the intermolecular force of the polyimide film, increase of micro defects, and destruction of the structural uniformity, resulting in the decline of the mechanical properties, thermal stability, compactness and other properties of the polyimide film, and the reduction of the product pass rate.

[0068] Since Comparative Example 4 uses a batch process, there are differences in the core physicochemical indexes of the polyamide acid slurry between different batches, and these differences will be transmitted through processing and reaction, directly leading to poor processing stability and performance consistency of the polyimide film, and ultimately reducing the product pass rate, especially having a greater impact on high-end polyimide films.

Claims

1. A continuous production system of polyimide film prepared by chemical imidization method, characterized by, The application relates to a continuous production system for preparing a polyimide film by a chemical imidization method.

2. The continuous production system for the chemical imidization method of producing a polyimide film according to claim 1, wherein The dianhydride solution preparation tank (4), the diamine solution preparation tank (6), the third monomer solution preparation tank (12), the first polymerization reaction kettle (10), the second polymerization reaction kettle (14), the defoaming device (15), the hardener preparation tank (17) and the needle rod mixer (18) are respectively provided with cooling jackets.

3. The continuous production system for the chemical imidization method of preparing a polyimide film according to claim 1, wherein The polyimide film prepared by the chemical imidization method is produced by the continuous production system, and the production comprises the following steps:

4. A continuous production process for polyimide films prepared by chemical imidization, characterized in that, ​ S1: The solid raw materials dianhydride and diamine are weighed and then put into a dianhydride solution preparation tank (4) and a diamine solution preparation tank (6) respectively together with solvents to prepare dianhydride solution and diamine solution; S2: The dianhydride solution and the diamine solution are cooled to -10-0℃ and then delivered to an impinging stream mixer I (9) for mixing, and after mixing, delivered to a first polymerization reactor (10) for polymerization at -10-50℃ for 1-3 hours; S3: The material after the reaction in the first polymerization reactor (10) is delivered to an impinging stream mixer II (11) for mixing with the third monomer solution in a third monomer solution preparation tank (12) in the impinging stream mixer II (11), and after mixing, delivered to a second polymerization reactor (14) for polymerization at 0-40℃ for 2-5 hours to obtain polyamic acid slurry; S4: The polyamic acid slurry is delivered to a deaerator (15) for deaeration; S5: The catalyst, dehydrating agent and solvent are prepared into a hardener in a hardener preparation tank (17), and then added to an impinging stream mixer III (16) together with the deaerated polyamic acid slurry for premixing, and then delivered to a pin-bar mixer (18) for further mixing; S6: After uniform mixing, the mixture is delivered to a die head of a casting machine (19), extruded through a film lip of the die head to form a liquid film on a casting steel belt to obtain a polyamic acid gel film; the polyamic acid gel film is delivered to a steel belt dryer (20) for solvent evaporation, and the polyamic acid is dehydrated and cyclized to complete partial chemical imidization to form a polyimide film; the polyimide film is delivered to a stretching machine (21) for longitudinal stretching, transverse stretching and heat setting in sequence to complete residual imidization, thereby obtaining the final polyimide film.

5. The continuous production process for the chemical imidization method of polyimide film according to claim 4, characterized in that, In step S1, the dianhydride is pyromellitic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride or hexafluoroisopropyl phthalic anhydride; the diamine is 4,4'-diamino diphenyl ether, 2,2'-bis(4-aminophenoxyphenyl)propane or 4,4'-diamino-2,2'-bistrifluoromethyl biphenyl; the concentration of the dianhydride solution and the diamine solution is 10-30 wt.%; the solvent used in step S1, the solvent used in the third monomer solution in step S3 and the solvent used in step S5 are dimethylacetamide, N,N-dimethylformamide or azomethyl pyrrolidone.

6. The continuous production process for the chemical imidization method of polyimide film according to claim 4, wherein the polyamic acid solution is prepared by dissolving the polyamic acid in the solvent, and the polyamic acid solution is applied to the surface of the glass substrate by a spin coating method. In step S2, the molar ratio of the diamine to the dianhydride is (0.4-0.9):1; after the reaction in the first polymerization reactor (10), the viscosity of the material is 5000-30000 cP.

7. The continuous production process for the chemical imidization method of polyimide film according to claim 4, wherein the polyamic acid solution is prepared by dissolving the polyamic acid in the solvent, and the polyamic acid solution is applied to the surface of the glass substrate by a spin coating method. In step S3, the third monomer is p-phenylenediamine, m-phenylenediamine or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane; the concentration of the third monomer solution is 10-15 wt.%; the molar ratio of the third monomer to the dianhydride is (0.1-0.6):1; after the reaction in the second polymerization reactor (14), the viscosity of the material is 100-1000 Pa·s; in step S4, the deaeration temperature is -15-10℃, and the deaeration pressure is 10-1000 Pa.

8. The continuous production process for the chemical imidization method of preparing a polyimide film according to claim 4, characterized in that, In step S5, the catalyst is isoquinoline, pyridine or triethylamine, the dehydrating agent is acetic anhydride, propionic anhydride or butyric anhydride; in the hardening agent, the concentration of the catalyst is 5-10 wt.%, the concentration of the dehydrating agent is 30-50 wt.%; the mass ratio of the polyamide acid slurry to the hardening agent is (2.5-3.5):

1.

9. The continuous production process for the chemical imidization method of preparing a polyimide film according to claim 4, characterized in that, In step S6, the steel belt dryer (20) is divided into three drying sections, which are drying section one for heating from 0℃ to 50-80℃, drying section two for continuously heating to 80-120℃ and drying section three for continuously heating to 120-200℃; the air inlet temperature of the steel belt air duct is 120-195℃, and the air inlet temperature of the lower air duct is 150-220℃.

10. A polyimide film prepared by a chemical imidization method, characterized in that, The polyimide film is prepared by the continuous production process of any one of claims 4-9.

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