Synthesis method and device of highly-homogenized polyamic acid resin and polyamic acid resin and polyimide film prepared by synthesis method and device

Abstract

The invention discloses a highly homogenized polyamic acid resin synthesis method and device, and a prepared polyamic acid resin and a polyimide film. Diamine, dianhydride and a reaction solvent are put into a first-stage reaction device for a pre-polycondensation reaction, and the raw materials are fully reacted to obtain a prepolymer through internal and external circulation type stirring of a reaction kettle; the viscosity of the prepolymer is controlled to be not higher than 500P; after the reaction is finished, conveying to a second-stage reaction device; and continuously adding a dianhydride solution to carry out a macromolecular chain extension reaction, and carrying out three-dimensional vortex type stirring to enable the reaction to be complete until the viscosity of the resin reaches 1500P or above, thereby completing synthesis. The invention also protects polyamide acid resin with the molecular weight polydispersity coefficient of 1.0-1.6 and the viscosity of more than 1500P. And a polyimide film prepared from the resin with an electrical strength and / or elongation at break Cv value of 1%-5%. According to the invention, homogenization of polyamide acid resin, especially inorganic particle hybrid polyamide acid resin, can be realized.

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, the product performance consistency is poor, and it 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 uses conventional stirring, which can only form a plane 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 material is more likely to form clumps, sediment and microgel in the resin system during feeding, which not only affects the stoichiometric ratio, but also forms product defects. 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 additives are mixed under high shear to form a slurry and are added to the diamine solution for polymerization reaction to obtain polyamide acid. This method avoids the direct addition of solid dianhydride monomers to the reaction system, to a certain extent, reduces the generation of microgel 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 clumping and residue.

[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, especially the uniformization requirements of inorganic particle hybrid resin, by relying only on two reaction kettles in series. 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 consistency requirements of application environment. 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 and realize the uniformization of polyamic acid resin, especially inorganic particle hybrid polyamic acid resin, to meet the consistency requirements of application environment.

[0008] To solve the above technical problems, the technical solution provided by the present application is a synthesis method for highly uniformized polyamic acid resin, comprising the following steps: (1) Pre-polycondensation reaction is carried out by adding diamine, dianhydride and reaction solvent into the first-stage reaction device. The above-mentioned 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; (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 a solution, and the above-mentioned 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.

[0009] The synthetic method of the 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.

[0010] The synthetic method, preferably, the first-stage reaction device is one reaction kettle or a series or parallel connection of two or more reaction kettles. 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.

[0011] The optimization design of the above first-stage reaction device makes the pre-polymerization 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.

[0012] More preferably, the stirring paddle adopts one or a combination 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.

[0013] 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 tee 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 to form axial internal and external circulation during polymerization, so as to avoid the residual and caking of the powder raw material at the bottom of the kettle.

[0014] 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.

[0015] 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.

[0016] The above synthesis method is preferably that 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 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.

[0017] 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.

[0018] 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.

[0019] The above synthesis method is preferably that the first-stage reaction device is a reaction kettle, and the second-stage reaction device is a reaction kettle. In step (1), the dianhydride raw material is batched into the first-stage reaction device. 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.

[0020] As a general technical concept, the present application also provides a polyamide acid resin prepared by the above synthesis method, the polyamide acid resin has a molecular weight polydispersity coefficient of 1.0 to 1.6 and a viscosity of more than 1500 P. The molecular weight polydispersity coefficient is determined by gel permeation chromatography (GPC), wherein 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.

[0021] Preferably, the polyamic acid resin has a molecular weight polydispersity coefficient of 1.0-1.5, or even 1.0-1.2, by controlling better process conditions.

[0022] Preferably, the polyamic acid resin has a viscosity deviation coefficient Cv of 1%-5% for 30 batches of finished resin. Cv = (average value / standard deviation) x 100%.

[0023] Preferably, the polyamic acid resin has a viscosity deviation coefficient Cv of 1%-5% for 30 batches of finished resin.

[0024] As a general technical concept, the present application also provides a polyimide film prepared from the above polyamic acid resin, wherein the polyimide film has a Cv value of 1%-5% for at least one basic parameter, including but not limited to electrical strength and / or elongation at break. The Cv value is determined for 30 batches of 25 μm polyimide film prepared by the casting method.

[0025] Preferably, the polyimide film has a Cv value of 1%-5% for at least one other functional parameter, including but not limited to water absorption or corona resistance life.

[0026] Preferably, the polyimide film has a Cv value of 1%-5% for at least one other functional parameter, including but not limited to water absorption or corona resistance life.

[0027] As a general technical concept, the present application also provides a synthesis device for preparing highly uniform polyamic acid resin, comprising a first-stage reaction device for performing polyamic acid pre-polycondensation reaction and a second-stage reaction device for performing polyamic acid macromolecular chain extension reaction, wherein the reaction liquid outlet of the first-stage reaction device is connected to the reaction liquid inlet of the second-stage reaction device through a communication pipeline, and a first-stage filter device is arranged on the communication pipeline; and the reaction liquid outlet of the second-stage reaction device is further provided with a second-stage filter device for filtering the 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 series or parallel connection of two or more reaction kettles. The first stage reaction device adopts internal and external circulation type stirring in the reaction kettle. The second stage reaction device adopts three-dimensional vortex type stirring.

[0028] The above synthetic device, preferably, the internal and external circulation type stirring in the reaction kettle is 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 type stirring is that a spiral belt type or a spiral rod type stirring is adopted, or a composite stirring form composed of two of a paddle type, a propelling type, an anchor type, a frame type and a turbine type.

[0029] The above synthetic device, preferably, the filter core aperture of the first stage filter device is 1-20 μm, preferably 5-10 μm; the filter core aperture of the second stage filter device is 25-60 μm, preferably 30-50 μm. The first stage filtration is mainly aimed at the low viscosity oligomer in the application, and mainly filters out residual solid powder and small particle impurities; and the second stage filtration mainly filters out macromolecular gel and other substances, and the combination of different filter devices can better fit the gradient viscosity control process of the application.

[0030] The above synthetic device, 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, 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; 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.

[0031] Compared with the prior art, the application has the following advantages: BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0032] Figure 1 It is a structure schematic diagram of the synthetic device of the polyamide acid resin in the embodiment 1 of the application.

[0033] Figure 2 It is a structure schematic diagram of the synthetic device of the polyamide acid resin in the comparative example 1 of the application.

[0034] Figure 3A structure schematic diagram of a synthesis device of a polyamic acid resin in Example 2 of the present application.

[0035] Figure 4 A structure schematic diagram of a synthesis device of a polyamic acid resin in Example 3 of the present application.

[0036] Figure 5 A structure schematic diagram of a synthesis device of a polyamic acid resin in Comparative Example 2 of the present application.

[0037] Figure 6 A structure schematic diagram of a synthesis device of a polyamic acid resin in Example 4 of the present application.

[0038] Figure 7 A structure schematic diagram of a synthesis device of a polyamic acid resin in Comparative Example 3 of the present application.

[0039] Figure 8 A structure schematic diagram of a reaction kettle without using the stirring form in the precondensation stage of the present application.

[0040] Legend 1, reaction cavity; 2, stirring paddle; 3, reaction liquid circulation 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

[0041] In order to facilitate the understanding of the present application, the present application will be described in more detail and in a more complete and specific manner below in conjunction with the drawings and preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0042] It should be particularly noted that when an element is described as being "fixed to, attached to, connected to or communicated to" another element, it can be directly fixed, attached, connected or communicated to the other element, or indirectly fixed, attached, connected or communicated to the other element through other intermediate connecting elements.

[0043] Unless otherwise defined, all the professional terms used below have the same meaning as commonly understood by those skilled in the art. The professional terms used in this document are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application.

[0044] 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.

[0045] Example 1: A synthesis method of a highly uniformized polyamic acid resin, comprising the following steps: (1) Pre-polycondensation stage: 800 kg of dimethylformamide (DMF) was put into the 1# reaction kettle, then 95.7 kg of oxydianiline (ODA) was put in, after complete dissolution, 96 kg of pyromellitic dianhydride (PMDA) was put in by batches, and the pre-polymer was obtained by using the reaction kettle internal and external circulation stirring reaction for 3 hours at a speed of 200 rpm, and the viscosity of the pre-polymer was controlled to be 218P; 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 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 three-way 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.

[0046] (2) Macromolecular chain extension stage: the pre-polymer prepared above was transferred to the 2# reaction kettle (the form of the stirring paddle is spiral type) through the communication pipeline 6 after being filtered by the first filter 4 (5 μm filter element), then 7.9 kg of pyromellitic dianhydride (PMDA) was put in by batches in the form of 5% DMF solution, and the polyamide acid resin was obtained by using the three-dimensional vortex stirring reaction for 3 hours at a speed of 45 rpm, and then filtered by the second filter 5 (50 μm filter element). The polyamide acid resin has a molecular weight polydispersity coefficient (PDI) of 1.44 and a viscosity of 1900P. The molecular weight polydispersity coefficient 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.

[0047] The above-mentioned polyamide acid resin was made into a 25 μm polyimide film by a chemical flow casting method, and the electrical strength was 325 kV / mm, and the elongation at break was 102%.

[0048] The above-mentioned process was used to prepare 30 batches of resin, and the viscosity Cv value was 3.9%. 30 batches of 25 μm polyimide films were made, and the electrical strength Cv value was 4.1%, and the elongation at break Cv value was 4.0%.

[0049] Cv= (average value / standard deviation) × 100%.

[0050] A kind of as Figure 1The apparatus shown is for preparing highly homogeneous polyamic acid resin, including a No. 1 reactor 11 for prepolymerization of polyamic acid and a No. 2 reactor 12 for chain extension of polyamic acid macromolecules. The reaction liquid outlet of the No. 1 reactor 11 is connected to the reaction liquid inlet of the No. 2 reactor 12 via a connecting pipe 6. A first filter 4 is provided on the connecting pipe 6. The reaction liquid outlet of the No. 2 reactor 12 is also provided with a second filter 5 for filtering the flow to the polyimide film preparation process. In this embodiment, reactor #11 is a single reactor; In this embodiment, reactor #2 (12) is a single reactor. In this embodiment, reactor #11 adopts an internal and external circulation stirring method. Specifically, the internal and external circulation stirring method means that a stirring paddle 2 is installed inside the reaction chamber 1 of reactor #11, and a reaction liquid circulation pipe 3 is configured outside reactor #11. The lower end of the reaction liquid circulation pipe 3 is connected to the bottom of the reaction chamber 1 of reactor #11, and the upper end is connected to the top of the reaction chamber 1 of reactor #11 to form an internal and external circulation. The connection port of the reaction liquid circulation pipe 3 at the top of the reaction chamber 1 of reactor #11 is 5cm away from the inner wall of reactor #11.

[0051] In this embodiment, reactor #2 12 adopts a three-dimensional vortex stirring, which refers to the use of ribbon stirring.

[0052] The above synthesis method firstly significantly improves the homogeneity of the polyamic acid resin by precisely controlling the viscosity range of the two-step process, combined with different stirring methods and the addition of dianhydride solution. In the first-stage reaction apparatus, internal and external circulation stirring is used to ensure thorough mixing and reaction of the raw materials, while controlling the prepolymer viscosity to not exceed 500P, creating favorable conditions for the subsequent chain extension reaction. In the second-stage reaction apparatus, three-dimensional vortex stirring is employed, and dianhydride is added in solution for the chain extension reaction, making the reaction more uniform and complete, ultimately obtaining a highly homogeneous polyamic acid resin.

[0053] Comparative Example 1: One such Figure 2 The method for synthesizing polyamic acid resin shown includes the following steps: (1) Raw material dissolution stage: 800 kg of DMF was added to the No. 1 reactor (stirring paddle type), followed by 95.7 kg of ODA. The mixture was dissolved at 200 rpm and the viscosity was 0.02 P.

[0054] (2) Polycondensation stage: The ODA solution was transferred to the 2# reactor (the form of stirring paddle was screw belt), and then 103.9 kg of PMDA was added in batches, and the reaction was stirred at 45 rpm for 3 hours to obtain polyamide acid resin, which was filtered through a 50 μm filter core.

[0055] It was detected that the PDI value of the resin was 1.76, and the viscosity was 1900 P. A 25 μm polyimide film was prepared by chemical flow casting method, and the electrical strength was 252 kV / mm, and the elongation at break was 81%.

[0056] The 30 reactor resins were prepared by the above process, and the viscosity Cv value was 6.7%. Thirty batches of 25 μm polyimide films were prepared, and the electrical strength Cv value was 7.1%, and the elongation at break Cv value was 7.3%.

[0057] The one-step polycondensation was used in the present comparative example. It can be seen from the comparison with Example 1 that the PDI value of the resin is significantly increased, 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 performance of the resin and the film product are greatly increased.

[0058] Example 2: As Figure 3 shown, in the present example, except that the distance between the communication port of the reaction liquid circulation pipeline 3 at the top of the reactor and the inner wall of the reactor is 15 cm, the rest is the same as Example 1.

[0059] It was detected that the PDI value of the resin was 1.54, and the viscosity was 1920 P. A 25 μm polyimide film was prepared by chemical flow casting method, and the electrical strength was 305 kV / mm, and the elongation at break was 95%.

[0060] The 30 reactor resins were prepared by the above process, and the viscosity Cv value was 4.5%. Thirty batches of 25 μm polyimide films were prepared, and the tensile strength Cv value was 4.8%, and the elongation at break Cv value was 4.9%.

[0061] The operation of the present example is basically the same as that of Example 1, and the distance between the communication port and the inner wall of the reactor is not controlled. It can be seen from the comparison that after the optimization operation in Example 1, the PDI value of the resin can be further reduced, and the uniformity of the performance of the resin and the film can be further improved.

[0062] Example 3: A method for synthesizing a highly uniform polyamide acid resin as Figure 4 shown, comprising the following steps: (1) Pre-polycondensation stage: 248.4 kg of 20% solid content dispersion liquid of nano-alumina with a particle size of 30 nm was prepared for standby use; In the 1# reactor, 800 kg of dimethylformamide (DMF) was put in, then 95.7 kg of oxydianiline (ODA) was put in, after dissolved, 89 kg of pyromellitic dianhydride (PMDA) was put in in batches, and the pre-polymer was obtained by using the reactor internal and external circulation stirring reaction for 3 hours at 160 rpm, and the viscosity of the pre-polymer was controlled to be 38P; The above-mentioned internal and external circulation stirring of the reactor 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# reactor 11, and a reaction liquid circulation pipeline 3 is arranged outside the 1# reactor 11; the lower end of the reaction liquid circulation pipeline 3 is communicated to the bottom of the reaction cavity 1 of the 1# reactor 11 (the discharge port at the bottom of the reactor 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# reactor 11 to form internal and external circulation. The distance between the feed port at the top of the reactor and the inner wall of the reactor is 0.8 cm.

[0063] The pre-polymer was transferred to the 2# reactor (the form of the stirring paddle is push type) after being filtered through the first filter 4 (2 μm filter core), 248.4 kg of nano-alumina dispersion liquid was put in, then 9.5 kg of PMDA was put in in batches, and the nano-hybrid pre-polymer was obtained by circulating stirring reaction for 2.5 hours at 240 rpm, and the viscosity was 325P. The distance between the feed port at the top of the reactor and the inner wall of the reactor is 2 cm.

[0064] (2) Macromolecular chain extension stage: the nano-hybrid pre-polymer prepared above was transferred to the 3# reactor 13 (the form of the stirring paddle is screw type) through the second filter 5 (15 μm filter core) through the communication pipeline 6, then 5.4 kg of pyromellitic dianhydride (PMDA) was put in in the form of 10% DMF solution in batches, and the nano-hybrid polyamic acid resin was obtained by using three-dimensional vortex stirring reaction for 4 hours at 55 rpm, and was filtered through the third filter 7 (30 μm filter core). It is detected that the polydispersity index (PDI) of the polyamic acid resin is 1.18, and the viscosity is 3920P. 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.

[0065] The above-mentioned polyamic acid resin was made into a 25 μm corona-resistant polyimide film by chemical flow casting method, the corona-resistant life (2kV, 155℃, 20kHz, 100ns) was 81 min, the tensile strength was 227 MPa, and the elongation at break was 116%.

[0066] 30 reactors were prepared by the above-mentioned process, and the viscosity Cv value was 3.4%. 30 batches of 25 μm corona-resistant polyimide films were made, and the corona-resistant life Cv value was 3.9%, the tensile strength Cv value was 3.8%, and the elongation at break Cv value was 3.7%.

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

[0068] A synthesis device as shown in Figure 4 Fig. 1 can be used to prepare highly homogenized polyamic acid resin, which comprises 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 polyamic acid macromolecular chain extension reaction, 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 a first filter 4 is arranged on the communication pipeline 6; the reaction liquid outlet of the 2# reaction kettle 12 is connected to the reaction liquid inlet of the 3# reaction kettle 13 through a communication pipeline 6, and a second filter 5 is arranged on the communication pipeline 6; the reaction liquid outlet of the 3# reaction kettle 13 is connected to a third filter 7. As shown in Figure 4 Fig. 1, 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 reaction kettles are connected in series. The 1# reaction kettle 11 of the embodiment adopts internal and external circulation stirring of the reaction kettle; the internal and external circulation stirring of the reaction kettle 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 2 cm away from the inner wall of the 1# reaction kettle 11.

[0069] The stirring paddle adopted by the 2# reaction kettle 12 of the embodiment is a propelling type. The 3# reaction kettle 13 of the embodiment adopts three-dimensional vortex stirring, which refers to screw type stirring.

[0070] Comparative Example 2: A synthesis method of a polyamic acid resin as shown in Figure 5 Fig. 1, comprising the following steps: (1) Inorganic particle dispersion liquid: 248.4 kg of 20% solid content dispersion liquid of nano-alumina with a particle size of 30 nm is obtained by treatment and is ready for use.

[0071] Raw material dissolution stage: 800 kg of dimethylformamide (DMF) is put into the 1# reaction kettle (the stirring paddle is in the form of a frame), then 95.7 kg of ODA and 248.4 kg of inorganic particle dispersion liquid are put in, and after being fully stirred and uniformly mixed, 89 kg of PMDA is put in in batches, and the stirring reaction is carried out at a speed of 160 rpm for 3 hours to obtain a prepolymer with a viscosity of 25 P.

[0072] The prepolymer was transferred to a 2# reaction kettle (propeller type stirring paddle) after filtration through a 15 μm filter, then 9.5 kg of PMDA was added in batches, and the reaction was stirred at 240 rpm for 2.5 hr to obtain a nano-hybrid prepolymer with a viscosity of 316 P.

[0073] (2) Macromolecular chain extension stage: The nano-hybrid prepolymer was transferred to a 3# reaction kettle (screw type stirring paddle) after secondary filtration, then 5.4 kg of PMDA was added in the form of a 10% DMF solution in batches, and the reaction was stirred at 55 rpm for 4 hr to obtain a nano-hybrid polyamic acid resin, which was filtered through a 30 μm filter. 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, 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%.

[0074] The above process was used to prepare 30 batches of resin, and the viscosity Cv value was 6.0%. Thirty batches of corona-resistant polyimide films were prepared, and the corona resistance life Cv value was 6.2%, the tensile strength Cv value was 6.3%, and the elongation at break Cv value was 6.3%.

[0075] In this comparative example, compared with Example 3, the main difference is that the 1# reaction kettle does not have internal and external circulation stirring. 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 values representing the uniformity of the performance of the resin and the film product are also significantly increased.

[0076] Example 4: A method for synthesizing a highly uniform polyamic acid resin as shown in Figure 6 , comprising the following steps: (1) Pre-polycondensation stage: In a 1# reaction kettle (anchor type stirring paddle), 600 kg of N-methyl pyrrolidone (NMP) was added, then 17.1 kg of oxydianiline (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'-benzophenonetetracarboxylic dianhydride (BTDA) and 23.2 kg of PMDA were added in batches, and the reaction was stirred at 190 rpm for 2 hr to obtain an amine-terminated flexible prepolymer A, and the prepolymer viscosity was controlled at 110 P.

[0077] Into 2# reaction kettle (the form of stirring paddle is push type), 297 kg of NMP was put, then 23 kg of p-phenylenediamine (PDA) was put, after complete dissolution, 51.1 kg of PMDA was put in batches, and the anhydride-terminated rigid prepolymer B was obtained by using reaction kettle internal and external circulation stirring reaction for 1.5 hr at a rotation speed of 220 rpm, and the viscosity was 225 P.

[0078] The internal and external circulation stirring of the above 1# and 2# reaction kettles specifically refers 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 kettle top feed port and the kettle inner wall is 8 cm.

[0079] (2) Macromolecular chain extension stage: the above prepared prepolymer A and B were transferred to 3# reaction kettle 13 (the form of stirring paddle is screw belt type and frame type composite) through the communication pipeline 6, the first filter 4 (10 μm filter element) and the second filter 5 (10 μm filter element) after filtration, and the polyamide acid resin was obtained by using three-dimensional vortex stirring reaction for 5 hr at a rotation speed of 65 rpm, and then filtered through the third filter 7 (45 μm filter element). The polyamide 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), 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.

[0080] The above polyamide acid resin was made into a 25 μm low water absorption type polyimide film by chemical casting method, and the tensile strength was 290 MPa, the elongation at break was 86%, and the water absorption rate was 0.96%.

[0081] The 30-kettle resin was prepared by the above process, and the viscosity Cv value was 4.7%. Thirty batches of 25 μm low water absorption type polyimide films were made, and the tensile strength Cv value was 4.8%, the elongation at break Cv value was 4.7%, and the water absorption rate Cv value was 4.7%.

[0082] Cv = (average value / standard deviation) x 100%.

[0083] A kind of as Figure 6The apparatus shown is for preparing highly homogeneous polyamic acid resin, including reactor 11 and reactor 22 for polyamic acid prepolymerization reaction and reactor 33 for polyamic acid macromolecular chain extension reaction. The reaction liquid outlets of reactors 11 and 22 are connected to the reaction liquid inlet of reactor 33 via connecting pipes 6. The connecting pipes 6 are equipped with a first filter 4 and a second filter 5. The reaction liquid outlet of reactor 33 is connected to a third filter 7. In this embodiment, reactor #11 is a reactor; reactor #212 is a reactor; reactor #313 is a reactor; and reactors #1 and #2 are connected in parallel and then connected to reactor #313. 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.

[0084] 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.

[0085] Comparative Example 3: 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%.

[0086] 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%.

[0087] 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.

[0088] Example 5: In the embodiment, except that the distance between the communicating port of the reaction liquid circulating pipeline 3 on the kettle top and the kettle inner wall is 0.7 cm, the rotating speed in the pre-polycondensation stage is 295 rpm, and the rotating speed in the macromolecular chain extension stage is 70 rpm, the rest is the same as in Example 1.

[0089] It is detected that the resin PDI is 1.12, and the viscosity is 1880 P. The 25 μm polyimide film is prepared by the chemical flow casting method, the electrical strength is 326 kV / mm, and the elongation at break is 105%.

[0090] The 30-kettle resin is prepared by the above process, the viscosity Cv value is 1.9%. The 30 batches of 25 μm polyimide films are prepared, the electrical strength Cv value is 2.2%, and the elongation at break Cv value is 2.3%.

[0091] Compared with Example 1, the embodiment mainly reduces the distance between the communicating port and the kettle inner wall and increases the stirring rotating speed, and the rest parameters are unchanged. It can be seen from the comparison that the resin PDI value can be further reduced, and the uniformity of the resin and the film performance can be further improved after the optimization operation in Example 5.

[0092] Comparative Example 4: In the comparative example, except that the filtration is cancelled, the rest is the same as in Example 1.

[0093] It is detected that the resin PDI is 1.56, and the viscosity is 1960 P. The 25 μm polyimide film is prepared by the chemical flow casting method, the electrical strength is 272 kV / mm, and the elongation at break is 92%.

[0094] The 30-kettle resin is prepared by the above process, the viscosity Cv value is 5.1%. The 30 batches of 25 μm polyimide films are prepared, the electrical strength Cv value is 5.5%, and the elongation at break Cv value is 5.5%.

[0095] The operation of the comparative example is basically the same as that of Example 1, and the filtration is mainly cancelled. It can be seen from the comparison that the resin PDI value can be further reduced, and the uniformity of the resin and the film performance can be further improved after the operation of the filtration device with different particle sizes in Example 1.

[0096] It can be seen from the above comparative examples that the importance of the comprehensive optimization of the stirring mode, the viscosity control and the parameter condition control of the technical scheme of the application. If the embodiment of the application is not used, the powder material residues or non-uniformity as shown in the pre-polycondensation stage will be caused, and then the product quality stability is affected. Figure 8

[0097] ​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 will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle 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 performing sufficient reaction by adopting internal and external circulation stirring of the reaction kettle to obtain a prepolymer, and controlling the viscosity of the prepolymer to be not higher than 500P; 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 filter; (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, and the aforementioned macromolecular chain extension reaction is completely performed by adopting three-dimensional vortex stirring until the viscosity of the polyamide acid resin after the chain extension reaction reaches 1500P or above, and the synthesis of the highly uniform polyamide acid resin is completed.

2. The method of synthesis of claim 1, wherein, 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 the reaction cavity of the first-stage reaction device, and a reaction liquid circulation pipeline is arranged outside the first-stage reaction device.

3. The method of synthesis of claim 2, wherein, The stirring paddle adopts one or a combination of multiple modes of paddle type, propelling type, anchor type, frame type and turbine type, and the rotating speed of the stirring paddle is controlled in the range of 100-300 rpm.

4. The method of synthesis of claim 2, wherein, 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.

5. The method of synthesis of claim 4, 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.

6. The method of synthesis according to any one of claims 1 to 5, wherein, In the pre-polycondensation reaction of the first-stage reaction device, inorganic fillers are added, the inorganic fillers are selected from one or several 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, the viscosity of the prepolymer before the inorganic fillers are added is 10-50P, and the viscosity of the intermediate obtained after the inorganic fillers are added and further reacted in the same reaction kettle is not lower than 300P.

7. The method of synthesis of claim 6, 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.

8. The method of synthesis according to any one of claims 1 to 5, wherein, 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 adopting screw belt stirring or screw rod stirring, or adopting a composite stirring mode composed of two of paddle type, propelling type, anchor type, frame type and turbine type, and the rotating speed of the three-dimensional vortex stirring is in the range of 40-70 rpm.

9. The synthesis method according to any one of claims 1-5, 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.

10. A polyamic acid resin prepared by the synthetic method according to any one of claims 1 to 9, characterized in that, The polyamide acid resin has a molecular weight polydispersity coefficient of 1.0-1.6 and a viscosity of 1500P or above. The molecular weight polydispersity coefficient is determined by gel permeation chromatography (GPC), wherein 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.

11. The polyamic acid resin according to claim 10, characterized by The viscosity deviation coefficient Cv of the 30-kettle resin is 1% to 5% as determined; Cv = average value / standard deviation × 100%.

12. A polyimide film prepared from the polyamic acid resin according to claim 10 or 11, 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 but are not limited to electrical strength and / or elongation at break; The Cv value is determined for 30 batches of 25 μm polyimide film prepared by the casting method.

13. The polyimide film according to claim 12, 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.

14. 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.

15. The synthesis device of claim 14, wherein, 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 a composite stirring form composed of two of a screw belt type or a screw rod type, or a paddle type, a propelling type, an anchor type, a frame type, and a turbine type; the first-stage filtration device adopts a filter core aperture of 1 to 20 μm, preferably 5 to 10 μm; and the second-stage filtration device adopts a filter core aperture of 25 to 60 μm, preferably 30 to 50 μm.

16. The synthesis device of claim 15, wherein, 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; the connection 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.

Images