Process for synthesizing highly uniform polyamic acid resin, apparatus therefor, and polyamide acid resin and polyimide film prepared thereby

Abstract

The application discloses a synthesis method and device of highly homogenized polyamide acid resin, and polyamide acid resin and polyimide film prepared by the device. In the first-stage reaction device, diamine, dianhydride and reaction solvent are put in to carry out pre-polycondensation reaction, the aforementioned raw materials are fully reacted by adopting internal and external circulation stirring of the reaction kettle to obtain a prepolymer, and the viscosity of the prepolymer is controlled to be not higher than 500 P; after the reaction is completed, the prepolymer is transported to the second-stage reaction device; dianhydride solution is continuously added to carry out macromolecular chain extension reaction, the aforementioned reaction is completely carried out by adopting three-dimensional vortex stirring until the resin viscosity reaches 1500 P or above, and the synthesis is completed. The application also protects a polyamide acid resin with a molecular weight polydispersity coefficient of 1.0-1.6 and a viscosity of 1500 P or above, and a polyimide film prepared by the resin with an electrical strength and / or elongation at break Cv value of 1%-5%. The polyamide acid resin, especially inorganic particle hybrid polyamide acid resin, can be homogenized by the application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyamide acid resin preparation, in particular to a synthesis method of highly uniformized polyamide acid resin, a polyamide acid resin prepared by the method, a polyimide film prepared from the resin and a synthesis device for preparing the highly uniformized polyamide acid resin. BACKGROUND

[0002] Studies have shown that the consistency of polyimide material performance is directly related to the molecular weight distribution of the precursor polyamide acid resin.

[0003] The traditional preparation method of polyamide acid is one-step polycondensation (commonly known as one-pot method). Usually, the diamine raw material is dissolved in one reaction kettle, then input into another reaction kettle through a pipeline, the dianhydride powder and other monomers are added, and the whole polymerization reaction is completed in the kettle. During the reaction, the resin viscosity increases rapidly from less than 1P to several thousand P. The single stirring form cannot meet the uniformization requirements of different viscosity solutions. The final molecular weight distribution of the resin is uneven, the viscosity batch is unstable, the fluctuation is large, which causes poor consistency of product performance and cannot meet the reliability requirements of high-end applications. In the existing polyamide acid preparation reaction system, two reaction devices are also used in series to prepare polyamide acid. The first reaction kettle is used to prepare a prepolymer solution, and the second reaction kettle is used to adjust the viscosity of the prepolymer. However, the first reaction device is usually equipped with a conventional stirring device, which can only form a planar vortex and cannot form a three-dimensional vortex, making it difficult to meet the uniformization requirements of high-viscosity resin.

[0004] Secondly, the solubility of powder raw materials, especially dianhydride, in the solvent is poor. As the viscosity increases, the feeding is more likely to form clumps, sediment and micro-gel in the resin system, which not only affects the stoichiometric ratio, but also forms product defects due to the residual powder or gel. CN115873244 A Chinese patent document proposes a preparation method of polyamide acid solution. The diamine monomer is dissolved in a solvent to form a solution, and the dianhydride monomer, solvent and additive are mixed under high shear to form a slurry and are fed into the diamine solution for polymerization reaction to obtain polyamide acid. This method avoids the direct addition of solid dianhydride monomer into the reaction system, to a certain extent, reduces the generation of micro-gel and clumps. However, as the polymerization reaction proceeds, the resin viscosity increases, the mixing efficiency between raw materials decreases in the later stage of the reaction due to the single stirring form, the polymerization reaction is uneven, and it is difficult to achieve precise control of the batch viscosity. Moreover, the shear dispersion effect is weakened after the viscosity increases, and the residual solid raw materials in the slurry still deposit at the bottom of the kettle, causing clumps and residues.

[0005] In addition, different application environments have different requirements for the functionalization of materials, which need to be realized by introducing inorganic particles into the polyamic acid resin system. How to avoid the sedimentation or secondary agglomeration of inorganic particles in the resin system while ensuring the uniform distribution of molecular weight of the base resin has been a bottleneck problem in the industry.

[0006] However, the existing two-step process is relatively rough, and the viscosity, reaction progress and raw material ratio of each step are not accurately controlled, which is not conducive to the precise control of the polycondensation reaction. It is difficult to meet the needs of different working conditions such as complex formula by relying on the series connection of two reaction kettles, especially it cannot meet the uniformization requirements of inorganic particle hybrid resin. Therefore, there is an urgent need for a synthesis device and method that can precisely control the whole process of polycondensation reaction and realize the uniformization of polyamic acid resin, especially inorganic particle hybrid polyamic acid resin, to meet the requirements of application environment for material consistency. SUMMARY

[0007] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background art, and to provide a synthesis method and device for highly uniformized polyamic acid resin, as well as a polyamic acid resin and a polyimide film prepared therefrom. The present application can precisely control the whole process of polycondensation reaction, realize the uniformization of polyamic acid resin, especially inorganic particle hybrid polyamic acid resin, and meet the requirements of application environment for material consistency.

[0008] To solve the above technical problems, the technical solution proposed by the present application is a synthesis method for highly uniformized polyamic acid resin, comprising the following steps:

[0009] (1) Pre-polycondensation reaction is carried out by adding diamine, dianhydride and reaction solvent into the first-stage reaction device, the aforementioned raw materials are fully reacted by using internal and external circulation stirring of the reaction kettle to obtain a prepolymer, and the viscosity of the prepolymer is controlled to be not higher than 500P; after the reaction is completed, the prepolymer is transported to the second-stage reaction device through the communication pipeline after being filtered by the first-stage filter;

[0010] (2) In the second-stage reaction device, dianhydride solution is continuously added for macromolecular chain extension reaction, the dianhydride powder raw material is added in the form of solution, and the aforementioned reaction is completed by using three-dimensional vortex stirring until the viscosity of the polyamic acid resin after chain extension reaction reaches 1500P or more (generally not more than 6000P, preferably 3000P-4000P), and the synthesis of highly uniformized polyamic acid resin is completed.

[0011] The synthetic method of the present application is to realize the synthesis of polyamide acid by two-step method, based on the unique refluxable first-stage reaction device, and then in the synthesis process, different characteristics of stirring mode and different raw materials of phased addition mode are matched, and then the viscosity gradient precise control of pre-polymerization and final polymerization is realized. The comprehensive effect greatly improves the uniformity of polyamide acid, avoids the problems of uneven molecular weight distribution of resin, unstable viscosity batch, poor product performance consistency and the like, and also provides a basic environment for the addition of subsequent inorganic functional particles.

[0012] The above-mentioned synthetic method, preferably, the first-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles.

[0013] The internal and external circulation stirring in the reaction kettle specifically refers to that a stirring paddle is installed in the reaction cavity of the first-stage reaction device, and a reaction liquid circulation pipeline is arranged outside the first-stage reaction device.

[0014] The optimization design of the above-mentioned first-stage reaction device makes the pre-polycondensation stage have a strong shearing dispersion effect, so that the powder raw material is fully dissolved; and the raw materials required in the later macromolecular chain extension stage are also added in the form of solution, further avoiding the residual powder.

[0015] More preferably, the above-mentioned stirring paddle adopts one or a combination of more than one of paddle type, propelling type, anchor type, frame type and turbine type (which can be single layer or multi-layer), and the rotating speed of the stirring paddle can be 10-300 rpm, preferably controlled at 100-300 rpm.

[0016] More preferably, the lower end of the reaction liquid circulation pipeline is communicated to the kettle bottom of the reaction cavity of the first-stage reaction device (the discharge port at the bottom of the reaction kettle can be provided with a three-way structure), and the upper end is communicated to the top of the reaction cavity of the first-stage reaction device to form internal and external circulation. With the preferred structure, the prepolymer solution is transported to the top of the reaction kettle through the bottom outlet and then injected into the kettle again during the polymerization reaction, thereby forming axial internal and external circulation, and avoiding the residual and caking of the powder raw material at the bottom of the kettle.

[0017] More preferably, the communication port of the reaction liquid circulation pipeline at the top of the reaction cavity of the first-stage reaction device is 0.5-10 cm away from the inner wall of the first-stage reaction device. By controlling the distance from the inner wall of the reaction kettle, the shearing force on the prepolymer can be increased, so that the prepolymer can be better dispersed.

[0018] The above synthesis method is preferably that an inorganic filler is added in the pre-polycondensation reaction of the first-stage reaction device, the inorganic filler is selected from one or more of titanium oxide, silicon oxide, silicon carbide, aluminum nitride, silicon nitride, boron nitride, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, calcium carbonate, calcium bicarbonate, aluminum oxide, carbon nanotube and graphene; the particle size of the inorganic filler is 10 nm to 4 μm; and the addition amount of the inorganic filler can be 0.1% to 30% of the mass of the polyimide film formed later. By adding the inorganic filler in the first-stage reaction device of the low-viscosity prepolymer, uniform dispersion is achieved through high-speed shearing, and the low-viscosity prepolymer can also provide a certain stabilizing effect for the inorganic phase to avoid premature settling and agglomeration; then the viscosity of the oligomer is appropriately increased through the polycondensation reaction, and the polymer molecular chains coated on the surface of the inorganic particles can be further increased. Before the inorganic filler is added, the viscosity of the prepolymer is 10 to 50 P, and after the inorganic filler is added, the viscosity of the intermediate obtained through further reaction in the same reaction kettle is not less than 300 P. By controlling the prepolymer to maintain a relatively low viscosity before the inorganic filler is added, the dispersion of the inorganic filler is not affected, and a certain wrapping effect is formed on the inorganic filler so that agglomeration does not occur in the later chain extension stage.

[0019] The above synthesis method is preferably that the second-stage reaction device is one reaction kettle or a series connection or a parallel connection of two or more reaction kettles.

[0020] The three-dimensional vortex stirring refers to the use of spiral belt stirring or spiral rod stirring, or the use of a composite stirring mode composed of two of paddle stirring, propeller stirring, anchor stirring, frame stirring and turbine stirring, and the rotating speed of the three-dimensional vortex stirring can be 5 to 100 rpm, preferably 40 to 70 rpm.

[0021] Through the optimization of the stirring structure in the second-stage reaction device, the tangential direction and the axial direction can have convection and mixing shearing functions.

[0022] The pore size of the filter core used in the first-stage filtration is 1 to 20 μm, preferably 5 to 10 μm. The pore size of the filter core used in the filtration after the liquid outlet of the second-stage reaction device is 25 to 60 μm, preferably 30 to 50 μm.

[0023] The above synthesis method is preferably that the first-stage reaction device is a reaction kettle or a series connection or a parallel connection of two or more reaction kettles.

[0024] In step (1), the dianhydride raw material is batched into the first-stage reaction device.

[0025] In step (2), the dianhydride powder raw material is in the form of a solution with a mass concentration of 5% to 30% and is batched into the second-stage reaction device.

[0026] As a general technical concept, the present application also provides a polyamic acid resin prepared by the above-mentioned synthesis method, wherein the polydispersity index of the polyamic acid resin is 1.0-1.6, and the viscosity is above 1500 P.

[0027] The polydispersity index is determined by gel permeation chromatography (GPC), wherein DMF is used as the mobile phase solvent for GPC test, and the flow rate of the mobile phase (DMF) pumped into the chromatographic column is 1 mL / min.

[0028] Preferably, by controlling better process conditions, the polydispersity index of the polyamic acid resin can be 1.0-1.5, or even 1.0-1.2.

[0029] Preferably, the viscosity coefficient of variation (Cv) of the 30-pot resin (30 batches of finished resin) is 1%-5%.

[0030] Cv=(average value / standard deviation)×100%.

[0031] Preferably, by controlling better process conditions, the viscosity coefficient of variation (Cv) of the polyamic acid resin can be even below 2.5%.

[0032] As a general technical concept, the present application also provides a polyimide film prepared from the above-mentioned polyamic acid resin, wherein the polyimide film is subjected to determination of at least one basic parameter Cv value, and the determined value is 1%-5%, wherein the basic parameters include but are not limited to electrical strength and / or elongation at break.

[0033] The Cv value is determined by measuring 30 batches of 25 μm polyimide films prepared by the casting method.

[0034] Preferably, the polyimide film is subjected to determination of at least one other functional parameter Cv value, and the determined value is 1%-5%; the other functional parameters include but are not limited to water absorption or corona resistance life.

[0035] Preferably, by controlling better process conditions, the basic parameter or functional coefficient Cv value of the polyimide film can be even below 2.5%.

[0036] As a general technical concept, the present application also provides a synthesis device for preparing highly homogenized polyamic acid resin, comprising a first-stage reaction device for performing polyamic acid precondensation polymerization and a second-stage reaction device for performing polyamic acid macromolecule chain extension reaction, a reaction liquid outlet of the first-stage reaction device being connected to a reaction liquid inlet of the second-stage reaction device through a connecting pipeline, and a first-stage filter device being arranged on the connecting pipeline; and a second-stage filter device for filtering for a polyimide film preparation process being further arranged at a reaction liquid outlet of the second-stage reaction device.

[0037] The first-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles.

[0038] The second-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles.

[0039] The first-stage reaction device adopts internal and external circulation stirring of a reaction kettle.

[0040] The second-stage reaction device adopts three-dimensional vortex stirring.

[0041] Preferably, the internal and external circulation stirring of a reaction kettle refers to that a stirring paddle is arranged in a reaction cavity of the first-stage reaction device, and a reaction liquid circulation pipeline is arranged outside the first-stage reaction device; and the three-dimensional vortex stirring refers to spiral ribbon stirring or spiral rod stirring, or a composite stirring mode composed of two of paddle stirring, propelling stirring, anchor stirring, frame stirring and turbine stirring.

[0042] Preferably, the first-stage filter device adopts a filter core aperture of 1-20 μm, preferably 5-10 μm; and the second-stage filter device adopts a filter core aperture of 25-60 μm, preferably 30-50 μm. The first-stage filtration mainly aims at low-viscosity oligomers in the present application, and mainly filters out residual solid powders and small-particle impurities; and the second-stage filtration mainly filters out macromolecular gels and other substances. The combination of different filter devices can better match the gradient viscosity control process of the present application.

[0043] Preferably, the lower end of the reaction liquid circulation pipeline is connected to the kettle bottom of the reaction cavity of the first-stage reaction device, and the upper end is connected to the top of the reaction cavity of the first-stage reaction device to form internal and external circulation; and the connecting port of the reaction liquid circulation pipeline at the top of the reaction cavity of the first-stage reaction device is 0.5-10 cm away from the inner wall of the first-stage reaction device.

[0044] Compared with the prior art, the present application has the following advantages: BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0046] Figure 1 The structure schematic diagram of the synthesis device of the polyamide acid resin in the embodiment 1 of the present application.

[0047] Figure 2 The structure schematic diagram of the synthesis device of the polyamide acid resin in the comparative example 1 of the present application.

[0048] Figure 3 The structure schematic diagram of the synthesis device of the polyamide acid resin in the embodiment 2 of the present application.

[0049] Figure 4 The structure schematic diagram of the synthesis device of the polyamide acid resin in the embodiment 3 of the present application.

[0050] Figure 5 The structure schematic diagram of the synthesis device of the polyamide acid resin in the comparative example 2 of the present application.

[0051] Figure 6 The structure schematic diagram of the synthesis device of the polyamide acid resin in the embodiment 4 of the present application.

[0052] Figure 7 The structure schematic diagram of the synthesis device of the polyamide acid resin in the comparative example 3 of the present application.

[0053] Figure 8 The structure schematic diagram of the reaction kettle without using the stirring form in the precondensation stage of the present application.

[0054] Legend

[0055] 1, reaction cavity; 2, stirring paddle; 3, reaction liquid circulating pipeline; 4, first filter; 5, second filter; 6, communication pipeline; 7, third filter; 11, 1# reaction kettle; 12, 2# reaction kettle; 13, 3# reaction kettle. DETAILED DESCRIPTION

[0056] In order to facilitate the understanding of the present application, the following will combine the drawings in the specification and the preferred embodiments to make a more comprehensive and detailed description of the present application, but the protection scope of the present application is not limited to the following specific embodiments.

[0057] It needs to be particularly pointed out that when a certain element is described as "fixed, connected or communicated with" another element, it can be directly fixed, connected or communicated with another element, or indirectly fixed, connected or communicated with another element through other intermediate connecting elements.

[0058] Unless otherwise defined, all the professional terms used in the following are the same as the meanings commonly understood by the skilled in the art. The professional terms used in the present text are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0059] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0060] Example 1:

[0061] A synthesis method of a highly uniformized polyamide acid resin, comprising the following steps:

[0062] (1) Pre-polycondensation stage: 800 kg of dimethylformamide (DMF) is put into 1# reaction kettle, then 95.7 kg of oxydianiline (ODA) is put in, after complete dissolution, 96 kg of pyromellitic dianhydride (PMDA) is put in in batches, and the pre-polymer is obtained by using the reaction kettle internal and external circulation stirring reaction at 200 rpm for 3 hours, and the pre-polymer viscosity is controlled at 218P;

[0063] The above-mentioned internal and external circulation stirring of the reaction kettle refers to that a stirring paddle 2 (the form of the stirring paddle is paddle type) is installed in the reaction cavity 1 of the 1# reaction kettle, and a reaction liquid circulation pipeline 3 is arranged outside the 1# reaction kettle; the lower end of the reaction liquid circulation pipeline 3 is communicated to the kettle bottom of the reaction cavity 1 of the 1# reaction kettle (the discharge port at the bottom of the reaction kettle can be provided with a tee structure), and the upper end is communicated to the top of the reaction cavity of the 1# reaction kettle to form internal and external circulation. The distance between the kettle top feed port and the kettle inner wall is 5 cm.

[0064] (2) Macromolecular chain extension stage: the prepolymer prepared above is transferred to 2# reaction kettle (the form of stirring paddle is helical ribbon) through the first filter 4 (5 μm filter element) via the communication pipeline 6, then 7.9 kg of pyromellitic dianhydride (PMDA) is added in batches in the form of 5% DMF solution, and polyamic acid resin is obtained by adopting three-dimensional vortex stirring at 45 rpm for 3 hours, and then filtered through the second filter 5 (50 μm filter element). The polydispersity index (PDI) of the polyamic acid resin is 1.44, and the viscosity is 1900 P. The polydispersity index is determined by gel permeation chromatography (GPC), in which DMF is used as the mobile phase solvent for GPC testing, and the flow rate of the mobile phase (DMF) pumped into the chromatographic column is 1 mL / min.

[0065] The above polyamic acid resin is prepared into a 25 μm polyimide film by a chemical casting method, and the electrical strength is 325 kV / mm, and the elongation at break is 102%.

[0066] The 30-kettle resin is prepared by the above process, and the viscosity Cv value is 3.9%. Thirty batches of 25 μm polyimide films are prepared, and the electrical strength Cv value is 4.1%, and the elongation at break Cv value is 4.0%.

[0067] Cv = (average value / standard deviation) × 100%.

[0068] A synthesis device as shown in Figure 1 which can be used for preparing highly uniformized polyamic acid resin, comprising a 1# reaction kettle 11 for performing polyamic acid pre-polycondensation reaction and a 2# reaction kettle 12 for performing macromolecular chain extension reaction of polyamic acid, and the reaction liquid outlet of the 1# reaction kettle 11 is connected to the reaction liquid inlet of the 2# reaction kettle 12 through a communication pipeline 6, and the communication pipeline 6 is provided with a first filter 4; and the reaction liquid outlet of the 2# reaction kettle 12 is further provided with a second filter 5 which can be used for filtering to the polyimide film preparation process;

[0069] The 1# reaction kettle 11 of the embodiment is one reaction kettle;

[0070] The 2# reaction kettle 12 of the embodiment is one reaction kettle;

[0071] The 1# reaction kettle 11 of the embodiment adopts internal and external circulation type stirring; the internal and external circulation type stirring specifically refers to that a stirring paddle 2 is installed in the reaction cavity 1 of the 1# reaction kettle 11, and a reaction liquid circulation pipeline 3 is arranged outside the 1# reaction kettle 11; the lower end of the reaction liquid circulation pipeline 3 is connected to the kettle bottom of the reaction cavity 1 of the 1# reaction kettle 11, and the upper end is connected to the top of the reaction cavity 1 of the 1# reaction kettle 11 to form internal and external circulation; the connection port of the reaction liquid circulation pipeline 3 at the top of the reaction cavity 1 of the 1# reaction kettle 11 is 5 cm away from the inner wall of the 1# reaction kettle 11.

[0072] The 2# reaction kettle 12 of the embodiment adopts three-dimensional vortex stirring, which refers to adopting screw ribbon stirring.

[0073] Through the above synthesis method, firstly, by accurately controlling the viscosity range of the two-step method, combined with different characteristics of the stirring mode and the addition of dianhydride solution, the uniformity of the polyamic acid resin is greatly improved. In the first stage reaction device, the internal and external circulation stirring is adopted to ensure that the raw materials are fully mixed and reacted, and the viscosity of the prepolymer is controlled to be not higher than 500P, which creates good conditions for the subsequent chain extension reaction. In the second stage reaction device, three-dimensional vortex stirring is adopted, and dianhydride is added in the form of a solution for chain extension reaction, so that the reaction is more uniform and complete, and finally a highly uniform polyamic acid resin is obtained.

[0074] Comparative Example 1:

[0075] A synthesis method of a polyamic acid resin as shown in Figure 2 , comprising the following steps:

[0076] (1) Raw material dissolving stage: 800 kg of DMF is put into the 1# reaction kettle (the form of stirring paddle is paddle type), then 95.7 kg of ODA is put in, and the dissolving is completed at a speed of 200 rpm, and the viscosity is 0.02P.

[0077] (2) Polycondensation stage: the ODA solution is transferred to the 2# reaction kettle (the form of stirring paddle is screw ribbon type), then 103.9 kg of PMDA is put in in batches, and the stirring reaction is carried out at a speed of 45 rpm for 3 hours to obtain a polyamic acid resin, which is filtered through a 50μm filter core.

[0078] After detection, the resin PDI value is 1.76, and the viscosity is 1900P. A 25μm polyimide film is prepared by chemical flow casting method, and the electrical strength is 252kV / mm, and the elongation at break is 81%.

[0079] The above process is used to prepare 30 batches of resin, and the viscosity Cv value is 6.7%. 30 batches of 25μm polyimide films are prepared, and the electrical strength Cv value is 7.1%, and the elongation at break Cv value is 7.3%.

[0080] This comparative example adopts one-step polycondensation. By comparison with Example 1, it can be seen that the resin PDI value is obviously improved, and the tensile strength and elongation at break of the finally prepared polyimide film are significantly decreased, and the Cv values representing the uniformity of the resin and the film product performance are greatly increased.

[0081] Example 2:

[0082] As shown in Figure 3As shown, in this embodiment, except that the distance between the communication port of the reaction liquid circulation pipeline 3 on the kettle top and the kettle inner wall is 15 cm, the rest is the same as in Example 1.

[0083] It is detected that the resin PDI is 1.54, and the viscosity is 1920P. A 25μm polyimide film is made by chemical flow casting method, the electrical strength is 305kV / mm, and the elongation at break is 95%.

[0084] The above process is used to prepare 30 kettle resins, and the viscosity Cv value is 4.5%. Thirty batches of 25μm polyimide films are made, the tensile strength Cv value is 4.8%, and the elongation at break Cv value is 4.9%.

[0085] The operation of this embodiment is basically the same as that of Example 1, and the distance between the communication port and the kettle inner wall is not controlled. It can be seen by comparison that after the optimization operation in Example 1, the resin PDI value can be further reduced, and the uniformity of the resin and film performance can be further improved.

[0086] Example 3:

[0087] A method for synthesizing a highly uniform polyamide acid resin, comprising the following steps: Figure 4

[0088] (1) Pre-polycondensation stage: 248.4kg of 20% solid content dispersion liquid of nano-alumina with a particle size of 30nm is obtained by treatment, and is ready for use;

[0089] In the 1# reaction kettle, 800kg of dimethylformamide (DMF) is put in, then 95.7kg of oxydianiline (ODA) is put in, after complete dissolution, 89kg of pyromellitic dianhydride (PMDA) is put in in batches, and the pre-polymer is obtained by using the reaction kettle internal and external circulation stirring reaction at 160rpm for 3hr, and the pre-polymer viscosity is controlled to be 38P;

[0090] The above-mentioned internal and external circulation stirring of the reaction kettle specifically refers to that a stirring paddle 2 (the form of the stirring paddle is frame type) is installed in the reaction cavity 1 of the 1# reaction kettle 11, and a reaction liquid circulation pipeline 3 is arranged outside the 1# reaction kettle 11; the lower end of the reaction liquid circulation pipeline 3 is communicated to the kettle bottom of the reaction cavity 1 of the 1# reaction kettle 11 (the discharge port at the bottom of the reaction kettle can be provided with a three-way structure), and the upper end is communicated to the top of the reaction cavity 1 of the 1# reaction kettle 11 to form internal and external circulation. The distance between the feed port on the kettle top and the kettle inner wall is 0.8cm.

[0091] ​The prepolymer is transferred to the 2# reactor (the form of stirring paddle is propeller type) through the first filter 4 (2 μm filter core) after filtration, 248.4 kg of nano-alumina dispersion liquid is put into the 2# reactor, then 9.5 kg of PMDA is put into the 2# reactor in batches, and the reaction is carried out under the condition of 240 rpm rotation speed and 2.5 hr to obtain the nano-hybrid prepolymer, and the viscosity is 325 P. The distance between the top feeding port of the reactor and the inner wall of the reactor is 2 cm.

[0092] (2) Macromolecular chain extension stage: the nano-hybrid prepolymer prepared above is transferred to the 3# reactor 13 (the form of stirring paddle is screw type) through the second filter 5 (15 μm filter core) after filtration through the connecting pipeline 6, then 5.4 kg of pyromellitic dianhydride (PMDA) is put into the 3# reactor in the form of 10% DMF solution, and the reaction is carried out under the condition of 55 rpm rotation speed and 4 hr to obtain the nano-hybrid polyamic acid resin, which is filtered through the third filter 7 (30 μm filter core). The polydispersity index (PDI) of the polyamic acid resin is 1.18, and the viscosity is 3920 P. The polydispersity index is determined by gel permeation chromatography (GPC), and DMF is used as the mobile phase solvent for GPC test, and the flow rate of the mobile phase (DMF) pumped into the chromatographic column is 1 mL / min.

[0093] The above polyamic acid resin is prepared into a 25 μm corona-resistant polyimide film by chemical casting method, and the corona-resistant life (2 kV, 155 ℃, 20 kHz, 100 ns) is 81 min, the tensile strength is 227 MPa, and the elongation at break is 116%.

[0094] The 30 reactors are prepared by the above process, and the viscosity Cv value is 3.4%. Thirty batches of 25 μm corona-resistant polyimide films are prepared, and the corona-resistant life Cv value is 3.9%, the tensile strength Cv value is 3.8%, and the elongation at break Cv value is 3.7%.

[0095] Cv = (average value / standard deviation) × 100%.

[0096] A synthesis device for preparing highly uniformized polyamic acid resin as shown in Figure 4 The synthesis device for preparing highly uniformized polyamic acid resin as shown in

[0097] The synthesis device for preparing highly uniformized polyamic acid resin as shown in Figure 4As shown, the 1# reaction kettle 11 of the embodiment is one reaction kettle; the 2# reaction kettle 12 is one reaction kettle; the 3# reaction kettle 13 is one reaction kettle; and the three-stage reaction kettle is connected in series.

[0098] The 1# reaction kettle 11 of the embodiment adopts reaction kettle internal-external circulation stirring; the reaction kettle internal-external circulation stirring specifically refers to that a stirring paddle 2 is installed in the reaction cavity 1 of the 1# reaction kettle 11, and a reaction liquid circulation pipeline 3 is arranged outside the 1# reaction kettle 11; the lower end of the reaction liquid circulation pipeline 3 is communicated to the kettle bottom of the reaction cavity 1 of the 1# reaction kettle 11, and the upper end is communicated to the top of the reaction cavity 1 of the 1# reaction kettle 11 to form internal-external circulation; the communication port of the reaction liquid circulation pipeline 3 at the top of the reaction cavity 1 of the 1# reaction kettle 11 is 2 cm away from the inner wall of the 1# reaction kettle 11.

[0099] The stirring paddle form adopted by the 2# reaction kettle 12 of the embodiment is a propelling type.

[0100] The 3# reaction kettle 13 of the embodiment adopts three-dimensional vortex stirring, which refers to screw type stirring.

[0101] Comparative Example 2:

[0102] A synthesis method of a polyamide acid resin as shown in Figure 5 comprises the following steps:

[0103] (1) Inorganic particle dispersion liquid: 248.4 kg of 20% solid content dispersion liquid of nano-alumina with a particle size of 30 nm was obtained by treatment and was prepared for use.

[0104] Raw material dissolution stage: 800 kg of dimethylformamide (DMF) was put into the 1# reaction kettle (the stirring paddle form was a frame type), then 95.7 kg of ODA and 248.4 kg of inorganic particle dispersion liquid were put in, and after being fully stirred and uniformly mixed, 89 kg of PMDA was put in in batches, and the stirring reaction was carried out at a speed of 160 rpm for 3 hours to obtain a prepolymer with a viscosity of 25 P.

[0105] The prepolymer was filtered through a 15 μm filter core and transferred to the 2# reaction kettle (the stirring paddle form was a propelling type), then 9.5 kg of PMDA was put in in batches, and the stirring reaction was carried out at a speed of 240 rpm for 2.5 hours to obtain a nano-hybrid prepolymer with a viscosity of 316 P.

[0106] (2) Macromolecular chain extension stage: the nano-hybrid prepolymer was transferred to a 3# reaction kettle (the form of stirring paddle was screw type) after secondary filtration, then 5.4 kg of PMDA was added in batches in the form of 10% DMF solution, and the stirring reaction was carried out at 55 rpm for 4 hours to obtain a nano-hybrid polyamic acid resin, which was filtered through a 30 μm filter core. The resin PDI value was 1.61, and the viscosity was 3880 P. A 25 μm corona-resistant polyimide film was prepared by chemical flow casting method, and the corona resistance life (2 kV, 155°C, 20 kHz, 100 ns) was 75 min, the tensile strength was 201 MPa, and the elongation at break was 95%.

[0107] The 30 kettle resins were prepared by the above process, and the Cv value of the viscosity was 6.0%. Thirty batches of corona-resistant polyimide films were prepared, and the Cv value of the corona resistance life was 6.2%, the Cv value of the tensile strength was 6.3%, and the Cv value of the elongation at break was 6.3%.

[0108] In this comparative example, compared with example 3, the main difference is that there is no internal and external circulation stirring in the 1# reaction kettle. In this case, the PDI value of the prepared resin is significantly increased, and the tensile strength and elongation at break of the finally prepared polyimide film are significantly decreased, and the Cv value representing the uniformity of the performance of the resin and the film product is also greatly increased.

[0109] Example 4:

[0110] A method for synthesizing a highly uniform polyamic acid resin as shown in Figure 6 , comprising the following steps:

[0111] (1) Pre-polycondensation stage:

[0112] In the 1# reaction kettle (the form of stirring paddle was anchor type), 600 kg of N-methyl pyrrolidone (NMP) was added, then 17.1 kg of diamino diphenyl ether (ODA) and 52.5 kg of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) were added, after complete dissolution, 27.5 kg of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and 23.2 kg of PMDA were added in batches, and the stirring reaction was carried out at 190 rpm for 2 hours in the internal and external circulation type of the reaction kettle to obtain an amine-terminated flexible prepolymer A, and the viscosity of the prepolymer was controlled at 110 P.

[0113] In the 2# reaction kettle (the form of stirring paddle was propeller type), 297 kg of NMP was added, then 23 kg of p-phenylenediamine (PDA) was added, after complete dissolution, 51.1 kg of PMDA was added in batches, and the stirring reaction was carried out at 220 rpm for 1.5 hours in the internal and external circulation type of the reaction kettle to obtain an anhydride-terminated rigid prepolymer B, and the viscosity was 225 P.

[0114] The above-mentioned 1# and 2# reaction kettles with internal and external circulation stirring specifically refer to that a stirring paddle 2 is installed in the reaction cavity 1, and a reaction liquid circulation pipeline 3 is arranged outside the reaction kettle; the lower end of the reaction liquid circulation pipeline 3 is communicated to the kettle bottom of the reaction cavity 1 (the discharge port at the bottom of the reaction kettle can be provided with a tee structure), and the upper end is communicated to the top of the reaction cavity 1 to form internal and external circulation. The distance between the feed inlet at the top of the kettle and the inner wall of the kettle is 8 cm.

[0115] (2) Macromolecular chain extension stage: the prepared prepolymer A and B are respectively transferred to the 3# reaction kettle 13 (the stirring paddle is in the form of a spiral belt combined with a frame) through the communication pipeline 6, the first filter 4 (10 μm filter element) and the second filter 5 (10 μm filter element), and then subjected to three-dimensional vortex stirring reaction at a speed of 65 rpm for 5 hours to obtain a polyamic acid resin, which is filtered through the third filter 7 (45 μm filter element). The polyamic acid resin has a molecular weight polydispersity coefficient (PDI) of 1.47 and a viscosity of 3150 P. The molecular weight polydispersity coefficient is determined by gel permeation chromatography (GPC), in which DMF is used as the mobile phase solvent for GPC testing, and the flow rate of the mobile phase (DMF) pumped into the chromatographic column is 1 mL / min.

[0116] The above-mentioned polyamic acid resin is prepared into a 25 μm low-water-absorption polyimide film by a chemical casting method, which has a tensile strength of 290 MPa, an elongation at break of 86%, and a water absorption of 0.96%.

[0117] The 30-kettle resin prepared by the above process has a viscosity Cv value of 4.7%. Thirty batches of 25 μm low-water-absorption polyimide films are respectively prepared, which have a tensile strength Cv value of 4.8%, an elongation at break Cv value of 4.7%, and a water absorption Cv value of 4.7%.

[0118] Cv = (average value / standard deviation) × 100%.

[0119] A synthesis device as shown in Figure 6 which can be used for preparing highly uniformized polyamic acid resin, comprising a 1# reaction kettle 11 for performing polyamic acid pre-polycondensation reaction, a 2# reaction kettle 12, and a 3# reaction kettle 13 for performing macromolecular chain extension reaction of polyamic acid, the reaction liquid outlets of the 1# reaction kettle 11 and the 2# reaction kettle 12 are respectively communicated to the reaction liquid inlet of the 3# reaction kettle 13 through a communication pipeline 6, and the communication pipeline 6 is provided with a first filter 4 and a second filter 5; the reaction liquid outlet of the 3# reaction kettle 13 is communicated to a third filter 7;

[0120] The 1# reaction kettle 11 of the present embodiment is one reaction kettle; the 2# reaction kettle 12 is one reaction kettle; the 3# reaction kettle 13 is one reaction kettle; and the 1# reaction kettle and the 2# reaction kettle are connected in parallel to the 3# reaction kettle 13;

[0121] In this embodiment, both reactor #1 (11) and reactor #2 (12) employ internal and external circulation stirring. Specifically, internal and external circulation stirring means that a stirring paddle 2 is installed inside the reaction chamber 1, and a reaction liquid circulation pipe 3 is configured outside the reactor. The lower end of the reaction liquid circulation pipe 3 is connected to the bottom of the reaction chamber 1, and the upper end is connected to the top of the reaction chamber 1 to form internal and external circulation. The connection port of the reaction liquid circulation pipe 3 at the top of the reaction chamber 1 is 8 cm away from the inner wall of the reactor.

[0122] In this embodiment, the stirring paddle used in reactor #11 is of the anchor type; the stirring paddle used in reactor #22 is of the propeller type; and the stirring paddle used in reactor #31 in this embodiment is of the three-dimensional vortex type, which refers to the combination of ribbon and frame type.

[0123] Comparative Example 3:

[0124] like Figure 7 As shown, there was no internal or external circulation stirring in the reactor during the pre-polymerization stage. The resins used in both the pre-polymerization and macromolecular chain extension stages were unfiltered; the rest was the same as in Example 4. The resin's PDI value was 1.72, and its viscosity was 3220P. A 25μm low-water-absorption polyimide film was prepared by chemical casting, exhibiting a tensile strength of 271MPa, an elongation at break of 77%, and a water absorption rate of 0.98%.

[0125] Thirty batches of resin were prepared using the above process, with a viscosity (Cv) of 6.5%. Thirty batches of low-absorption polyimide films were then produced, with tensile strength (Cv) of 6.9%, elongation at break (Cv) of 6.8%, and water absorption (Cv) of 6.6%.

[0126] Compared to Example 4, the PDI value of the resin prepared in this comparative example is significantly improved, the tensile strength and elongation at break of the final polyimide film are significantly reduced, and the Cv value, which characterizes the uniformity of the resin and film product performance, is significantly increased.

[0127] Example 5:

[0128] In this embodiment, except that the distance between the connection port of the reaction liquid circulation pipe 3 at the top of the vessel and the inner wall of the vessel is 0.7 cm, the rotation speed is 295 rpm during the pre-condensation stage and 70 rpm during the macromolecular chain extension stage, the rest is the same as in Example 1.

[0129] Testing revealed that the resin had a PDI of 1.12 and a viscosity of 1880P. A 25μm polyimide film was produced using a chemical casting method, exhibiting an electrical strength of 326kV / mm and an elongation at break of 105%.

[0130] The 30-kettle resin prepared by the above process has a viscosity Cv value of 1.9%. Thirty batches of 25-μm polyimide films are prepared, and the electrical strength Cv value is 2.2% and the elongation at break Cv value is 2.3%.

[0131] Compared with Example 1, the main difference of this example is that the distance between the communication port and the kettle inner wall is reduced and the stirring speed is increased, and the other parameters remain unchanged. It can be seen from the comparison that, after the optimization operation in Example 5, the resin PDI value can be further reduced, and the uniformity of the resin and film performance can be further improved.

[0132] Comparative Example 4:

[0133] In this comparative example, the rest is the same as Example 1 except that the filtration is cancelled.

[0134] After detection, the resin PDI is 1.56, and the viscosity is 1960 P. The 25-μm polyimide film prepared by the chemical flow casting method has an electrical strength of 272 kV / mm and an elongation at break of 92%.

[0135] The 30-kettle resin prepared by the above process has a viscosity Cv value of 5.1%. Thirty batches of 25-μm polyimide films are prepared, and the electrical strength Cv value is 5.5% and the elongation at break Cv value is 5.5%.

[0136] This comparative example is basically the same as the operation of Example 1, and the main difference is that the filtration is cancelled. It can be seen from the comparison that, after the operation of Example 1 with different particle size filtration devices, the resin PDI value can be further reduced, and the uniformity of the resin and film performance can be further improved.

[0137] As can be seen from the above comparative examples, the importance of the comprehensive optimization of the stirring mode, viscosity control and parameter condition control of the technical scheme of the present application is shown. If the embodiment of the present application is not used, the powder material residue or non-uniformity as shown in the pre-polycondensation stage will often occur, thereby affecting the quality stability of the product. Figure 8

[0138] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for synthesizing a highly uniform polyamic acid resin, characterized by, The method comprises the following steps: (1) feeding diamine, dianhydride and reaction solvent into a first-stage reaction device to perform pre-polycondensation reaction, and obtaining a prepolymer by using internal and external circulation stirring of a reaction kettle to make the prepolymer fully react, and controlling the viscosity of the prepolymer to be not higher than 500 P; after the reaction is completed, the prepolymer is transported to a second-stage reaction device through a communication pipeline after being filtered by the first-stage reaction device; the first-stage reaction device is one reaction kettle or a series connection or parallel connection of two or more reaction kettles; the internal and external circulation stirring of the reaction kettle specifically means that a stirring paddle is installed in a reaction cavity of the first-stage reaction device, and a reaction liquid circulation pipeline is arranged outside the first-stage reaction device; the lower end of the reaction liquid circulation pipeline is communicated to the kettle bottom of the reaction cavity of the first-stage reaction device, and the upper end is communicated to the top of the reaction cavity of the first-stage reaction device to form internal and external circulation; (2) continuously feeding dianhydride into the second-stage reaction device to perform macromolecular chain extension reaction, the dianhydride is added in the form of a solution, the macromolecular chain extension reaction is completely performed by using three-dimensional vortex stirring until the viscosity of the polyamide acid resin after the chain extension reaction reaches 1500 P or more, and the synthesis of the highly uniform polyamide acid resin is completed; the second-stage reaction device is one reaction kettle or a series connection or parallel connection of two or more reaction kettles; the three-dimensional vortex stirring means that screw belt stirring or screw rod stirring is used, or composite stirring formed by two of paddle stirring, propelling stirring, anchor stirring, frame stirring and turbine stirring is used.

2. The method of synthesis of claim 1, wherein, The stirring paddle is a combination of one or more of paddle stirring, propelling stirring, anchor stirring, frame stirring and turbine stirring, and the rotating speed of the stirring paddle is controlled to be in the range of 100-300 rpm.

3. The method of synthesis of claim 1, wherein, The communication port of the reaction liquid circulation pipeline at the top of the reaction cavity of the first-stage reaction device is 0.5-10 cm away from the inner wall of the first-stage reaction device.

4. The synthesis method according to any one of claims 1 to 3, characterized in that, In the pre-polycondensation reaction of the first-stage reaction device, inorganic fillers are added, the inorganic fillers are selected from one or more of titanium oxide, silicon oxide, silicon carbide, aluminum nitride, silicon nitride, boron nitride, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, calcium carbonate, calcium bicarbonate, aluminum oxide, carbon nanotube and graphene; the particle size of the inorganic fillers is 10 nm-4 μm; before the inorganic fillers are added, the viscosity of the prepolymer is 10-50 P, and after the inorganic fillers are added, the viscosity of the intermediate obtained by further reaction in the same reaction kettle is not less than 300 P.

5. The method of synthesis of claim 4, wherein, The first-stage reaction device is a series connection of two or more reaction kettles, and the inorganic fillers are added in other subsequent reaction kettles after the stirring reaction in the first reaction kettle.

6. The method of synthesis according to any one of claims 1 to 3, wherein, The rotating speed of the three-dimensional vortex stirring is in the range of 40-70 rpm.

7. The synthesis method according to any one of claims 1-3, characterized in that, in step (1), the dianhydride is fed into the first-stage reaction device in batches; in step (2), the dianhydride is fed into the second-stage reaction device in the form of a solution with a mass concentration of 5-30% in batches.

8. A polyamic acid resin prepared by the synthetic method according to any one of claims 1 to 7, characterized in that, The polyamide acid resin has a molecular weight polydispersity coefficient of 1.0-1.6 and a viscosity of 1500 P or more. The molecular weight polydispersity coefficient is determined by gel permeation chromatography, wherein DMF is used as the mobile phase solvent for the gel permeation chromatography test, and the flow rate of the mobile phase pumped into the chromatographic column is 1 mL / min.

9. The polyamic acid resin according to claim 8, characterized by The viscosity deviation coefficient Cv of the 30-kettle resin is determined to be 1% to 5%; Cv = average value / standard deviation × 100%.

10. A polyimide film prepared from the polyamic acid resin according to claim 8 or 9, characterized in that, The polyimide film is determined for at least one basic parameter Cv value, and the determined value is 1% to 5%; the basic parameters include electrical strength and / or elongation at break; The Cv value is determined for 30 batches of 25 μm polyimide films prepared by the casting method.

11. The polyimide film according to claim 10, wherein The determined value of at least one other functional parameter Cv value of the polyimide film is 1% to 5%; the other functional parameters include water absorption or corona resistance life.

12. A synthesis device that can be used to prepare highly uniformized polyamic acid resin, comprising a first-stage reaction device for performing a polyamic acid pre-polycondensation reaction and a second-stage reaction device for performing a polyamic acid macromolecular chain extension reaction, a reaction liquid outlet of the first-stage reaction device being connected to a reaction liquid inlet of the second-stage reaction device through a communication pipeline, and a first-stage filtration device being arranged on the communication pipeline; a reaction liquid outlet of the second-stage reaction device being further provided with a second-stage filtration device that can be used for filtration to a polyimide film preparation process; The first-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles; The second-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles; characterized in that, The first-stage reaction device adopts internal and external circulation stirring of the reaction kettle; The second-stage reaction device adopts three-dimensional vortex stirring; The internal and external circulation stirring of the reaction kettle specifically refers to that a stirring paddle is installed in the reaction cavity of the first-stage reaction device, and a reaction liquid circulation pipeline is arranged outside the first-stage reaction device; the three-dimensional vortex stirring refers to spiral ribbon stirring or spiral rod stirring, or a composite stirring form composed of two of paddle type, propelling type, anchor type, frame type, and turbine type; the lower end of the reaction liquid circulation pipeline is connected to the kettle bottom of the reaction cavity of the first-stage reaction device, and the upper end is connected to the top of the reaction cavity of the first-stage reaction device to form internal and external circulation.

13. The synthesis device of claim 12, wherein, The filter core pore size of the first-stage filtration device is 1 to 20 μm; and the filter core pore size of the second-stage filtration device is 25 to 60 μm.

14. The synthesis device of claim 13, wherein, The filter core pore size of the first-stage filtration device is 5 to 10 μm; and the filter core pore size of the second-stage filtration device is 30 to 50 μm.

15. The synthesis device of claim 13, wherein, The communication port of the reaction liquid circulation pipeline at the top of the reaction cavity of the first-stage reaction device is 0.5 to 10 cm away from the inner wall of the first-stage reaction device.

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