Aromatic polyamide film as well as preparation method and application thereof

Abstract

The invention relates to an aromatic polyamide film as well as a preparation method and application thereof, and the preparation method comprises the following steps: carrying out tape casting, solidification, two-way stretching and heat setting on a film casting solution to obtain the aromatic polyamide film, the membrane casting solution is prepared from polyesteramide, aromatic polyamide and a solvent. The casting film liquid composed of the polyamideester, the aromatic polyamide and the solvent is low in apparent viscosity and good in fluidity, the thickness deviation of the prepared aromatic polyamide film is small, and the composite insulating material prepared by compounding the aromatic polyamide film and aramid paper is small in thickness deviation, high in breakdown voltage, not prone to layering and good in thermal-state cohesiveness.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an aromatic polyamide film, its preparation method, and its application. Background Technology

[0002] In existing technologies, meta-aramid paper is typically composited with polyimide film or polyester film to create meta-aramid paper insulating composites, in order to meet the ever-evolving requirements of electrical equipment. Meta-aramid paper is a special type of paper made from pure meta-aramid fibers. It is often combined with polyimide film, polyester film, etc., to prepare composite insulating materials. However, due to the differences in molecular structure and properties between polyimide film, polyester film, and meta-aramid paper, the interfacial bonding strength between the materials is affected. As a result, the composite insulating materials made from meta-aramid paper have poor consistency, and the overall performance of the composite insulating material cannot be effectively utilized.

[0003] Aromatic polyamide films have the characteristics of high strength, low deformation, high temperature resistance, chemical corrosion resistance, flame retardancy and excellent electrical insulation properties. Moreover, they have small differences in molecular structure and properties with aramid paper, resulting in high interfacial bonding strength between the materials.

[0004] However, the molding process of aromatic polyamide films is limited by its own crystallization behavior, viscosity and solvent, etc., and the requirements for molding process parameters are extremely demanding, making it difficult to prepare aromatic polyamide films with uniform thickness and performance.

[0005] Therefore, it is necessary to develop a method for preparing aromatic polyamide films and a composite insulating material to solve the problems of difficult preparation of aromatic polyamide films and poor interfacial bonding of meta-aramid paper composite insulating materials. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an aromatic polyamide film, its preparation method, and its applications. In the preparation method of the aromatic polyamide film, the casting solution has low apparent viscosity and good fluidity, resulting in a small thickness deviation in the prepared aromatic polyamide film. The composite insulating material prepared by combining the aromatic polyamide film with aramid paper exhibits small thickness deviation, high breakdown voltage, resistance to delamination, and good hot adhesion.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing an aromatic polyamide film, the method comprising the following steps: casting a casting solution by casting, solidification, biaxial stretching and heat setting to obtain the aromatic polyamide film; wherein the raw materials for preparing the casting solution include polyamide ester, aromatic polyamide and solvent.

[0009] In this invention, by using polyamide ester and aromatic polyamide to prepare the casting solution, the problem of high viscosity of aromatic polyamide solution can be improved, the viscosity of the casting solution is reduced, the fluidity is good, and the film-forming properties are good, resulting in small thickness deviation of the aromatic polyamide film.

[0010] Preferably, the polymer content in the casting solution is 15wt% to 25wt% (e.g., 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, or 24wt%), more preferably 18wt% to 20wt%.

[0011] In this invention, the polymer content in the casting solution is preferably 15wt% to 25wt%. If the polymer content in the casting solution is too low, the intermolecular forces are weak, the thickness is low, and the mechanical properties are weak. If the polymer content in the casting solution is too high, the apparent viscosity of the casting solution increases, the fluidity is poor, and the thickness deviation of the aromatic polyamide film is high.

[0012] In this invention, the polymer in the casting solution refers to polyamide ester, aromatic polyamide, and the reaction product of polyamide ester and aromatic polyamide.

[0013] Preferably, the mass ratio of the polyamide to the aromatic polyamide is (0.5 to 2.0):1 (e.g., 0.7:1, 0.9:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1 or 1.9:1, etc.), and more preferably (1.0 to 1.6):1.

[0014] Preferably, the apparent viscosity of the casting solution at 25°C is 2000–4000 poise (e.g., 2200 poise, 2400 poise, 2600 poise, 2800 poise, 3000 poise, 3200 poise, 3400 poise, 3600 poise, or 3800 poise, etc.).

[0015] In this invention, the interaction between the polymer and the solvent in the casting solution determines the rheological properties of the solution. When the concentration (preferably 18wt% to 20wt%) and apparent viscosity (preferably 2000 to 4000 poise) of the casting solution are within an appropriate range, the interaction between the polymer and the solvent can reach a balance, maintaining both the solubility of the polymer and ensuring good flowability of the casting solution. The interaction forces between polymer molecules affect the apparent viscosity of the solution. At a concentration of 18wt% to 20wt%, the attractive and repulsive forces between polymer molecules reach a balance, allowing the casting solution to maintain a low apparent viscosity while having sufficient strength.

[0016] Preferably, the solvent includes any one or a combination of at least two of N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, toluene, chlorobenzene, dichloroethane, xylene, trimethylbenzene, or 2-methylpyridine.

[0017] Preferably, the aromatic polyamide comprises meta-aramid.

[0018] Preferably, the process before casting further includes degassing and filtration steps.

[0019] Preferably, the degassing includes degassing in a degassing tank at a temperature of 80–90°C (e.g., 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, or 89°C) for a time of 0.5–1.5 h (e.g., 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, or 1.4 h).

[0020] Preferably, the casting temperature is 20–30°C.

[0021] Preferably, the casting speed is 2 to 5 m / min (e.g., 2.3 m / min, 2.6 m / min, 2.9 m / min, 3.2 m / min, 3.5 m / min, 3.8 m / min, 4.1 m / min, 4.4 m / min or 4.7 m / min, etc.).

[0022] Preferably, the casting process further includes cooling and stretching orientation steps.

[0023] Preferably, the cooling and stretching orientation are carried out in an air layer of 5 to 25 mm (e.g., 7 mm, 9 mm, 11 mm, 13 mm, 15 mm, 17 mm, 19 mm, 21 mm or 23 mm, etc.).

[0024] In this invention, the air layer refers to the distance between the die lip and the liquid surface, that is, the distance exposed to the air. It relates to the air gap control between the film and the cooling roller in the casting process. This air gap needs to be adjusted by an air box to ensure uniform film adhesion to the roller and cooling effect.

[0025] Preferably, the solidification includes solidification in a first solidification bath and a second solidification bath.

[0026] Preferably, the first coagulation bath comprises the following components by mass percentage: 10% to 20% N,N-dimethylacetamide (e.g., 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 19%) and 80% to 90% water (e.g., 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 89%).

[0027] Preferably, the second coagulation bath comprises the following components by mass percentage: 20% to 45% N,N-dimethylacetamide (e.g., 23%, 26%, 29%, 32%, 35%, 38%, 41%, or 44%) and 55% to 80% water (e.g., 58%, 61%, 64%, 67%, 70%, 73%, 76%, or 79%).

[0028] Preferably, the temperatures of the first coagulation bath and the second coagulation bath are independently 5 to 20°C, for example 7°C, 9°C, 11°C, 13°C, 15°C, 17°C or 19°C.

[0029] Preferably, the bidirectional stretching includes transverse stretching and longitudinal stretching.

[0030] Preferably, the temperature for the transverse stretching is 150–180°C, such as 155°C, 160°C, 165°C, 170°C, or 175°C.

[0031] Preferably, the stretching ratio of the transverse stretching is 1.1 to 1.3, such as 1.12, 1.14, 1.16, 1.18, 1.20, 1.22, 1.24, 1.26 or 1.28.

[0032] Preferably, the longitudinal stretching temperature is 350-400℃, such as 355℃, 360℃, 365℃, 370℃, 375℃, 380℃, 385℃, 390℃ or 395℃.

[0033] Preferably, the longitudinal stretching ratio is 1.01 to 1.2, such as 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16 or 1.18.

[0034] Preferably, the heat setting temperature is 350–400°C, such as 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, or 395°C.

[0035] Preferably, the casting solution is prepared by mixing a polyamide ester solution, an aromatic polyamide solution, and optionally a solvent, and reacting them to obtain the casting solution.

[0036] Preferably, the polyamide ester solution contains 18wt% to 25wt% of polyamide ester by mass, such as 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, or 24wt%.

[0037] Preferably, the specific logarithmic viscosity of the aromatic polyamide solution at 25°C is between 1.8 and 2.3 dL / g, for example, 1.85 dL / g, 1.90 dL / g, 1.95 dL / g, 2.00 dL / g, 2.05 dL / g, 2.10 dL / g, 2.15 dL / g, 2.20 dL / g, or 2.25 dL / g.

[0038] Preferably, the aromatic polyamide in the aromatic polyamide solution has a mass percentage of 18wt% to 25wt%, such as 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, or 24wt%.

[0039] Preferably, the reaction temperature is 20-30°C, such as 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, or 29°C.

[0040] Preferably, the reaction time is 10 to 15 hours, such as 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours or 14.5 hours.

[0041] Preferably, the polyamide ester solution is prepared by the following method.

[0042] (1) Mix dianhydride monomer, ethanol and tetrahydrofuran and react to obtain dicarboxylic acid ester.

[0043] (2) The dicarboxylic acid ester, diamine monomer, catalyst and N,N-dimethylacetamide obtained in step (1) are mixed and reacted to obtain the polyamide ester solution.

[0044] Preferably, the dianhydride monomer comprises pyromellitic dianhydride (PMDA).

[0045] Preferably, the molar ratio of the dianhydride monomer to ethanol is 1:(1.9 to 2.1), for example, 1:1.92, 1:1.94, 1:1.96, 1:1.98, 1:2.00, 1:2.02, 1:2.04, 1:2.06 or 1:2.08, etc.

[0046] Preferably, the mass ratio of the dianhydride monomer to tetrahydrofuran is 1:(1.5 to 1.8), for example, 1:1.55, 1:1.6, 1:1.65, 1:1.7 or 1:1.75, etc.

[0047] Preferably, the reaction temperature in step (1) is 60-80℃ (e.g., 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃ or 78℃, etc.), and the reaction time is 3-5h (e.g., 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h or 4.8h, etc.).

[0048] Preferably, step (1) further includes precipitation, washing, and drying after the reaction.

[0049] Preferably, the molar ratio of the dicarboxylic acid ester to the diamine monomer is 1:(0.9 to 1.1), for example, 1:0.92, 1:0.94, 1:0.96, 1:0.98, 1:1.00, 1:1.02, 1:1.04, 1:1.06 or 1:1.08, etc.

[0050] Preferably, the molar ratio of the dicarboxylic acid ester to the catalyst is 1:(0.5 to 1.0), for example, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9 or 1:0.95, etc.

[0051] Preferably, the diamine monomer comprises 4,4-diaminodiphenyl ether (ODA).

[0052] Preferably, the catalyst comprises N,N'-diisopropylcarbodiimide.

[0053] Preferably, the reaction temperature in step (2) is 20-30°C (e.g., 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, or 29°C, etc.), and the reaction time is 10-15h (e.g., 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, or 14.5h, etc.).

[0054] Preferably, the reactions in steps (1) and (2) are carried out under nitrogen protection.

[0055] Preferably, the aromatic polyamide solution is prepared by the following method.

[0056] (I) Mix m-phenylenediamine and the first solvent to obtain an organic solution of m-phenylenediamine.

[0057] (II) Mix isophthaloyl chloride and the second solvent to obtain an organic solution of isophthaloyl chloride.

[0058] (III) Mix m-phenylenediamine organic solution and part of isophthalamide organic solution and react to obtain prepolymer mixture.

[0059] (IV) The prepolymer mixture obtained in step (III) is mixed with the remaining isophthalic acid organic solution and reacted to obtain the aromatic polyamide solution.

[0060] Steps (Ⅰ) and (Ⅱ) can be performed sequentially or simultaneously, regardless of the order in which they are performed.

[0061] Preferably, the molar ratio of m-phenylenediamine to isophthaloyl chloride is (1-1.1):1, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.0, etc.

[0062] Preferably, the first solvent comprises N,N-dimethylacetamide and / or N-methyl-2-pyrrolidone.

[0063] Preferably, the mass ratio of m-phenylenediamine to the first solvent is 1:(9.5-12), for example, 1:9.6, 1:9.8, 1:10.0, 1:10.2, 1:10.4, 1:10.6, 1:10.8, 1:11.0, 1:11.2, 1:11.4, 1:11.6, 1:11.8, or 1:12.

[0064] Preferably, the second solvent comprises any one or a combination of at least two of toluene, chlorobenzene, dichloroethane, xylene, trimethylbenzene, or 2-methylpyridine.

[0065] Preferably, the mass ratio of isophthaloyl chloride to the second solvent is 1:(1-3), for example, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6 or 1:2.8.

[0066] Preferably, based on the total mass of the isophthaloyl chloride organic solution as 100%, the mass of the isophthaloyl organic solution in the portion is 60% to 80%, for example, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, or 78%.

[0067] Preferably, the reaction in step (III) is carried out in a microreactor at a temperature of 4–6°C (e.g., 4.2°C, 4.4°C, 4.6°C, 4.8°C, 5.0°C, 5.2°C, 5.4°C, 5.6°C, or 5.8°C, etc.), and the feed rates of the m-phenylenediamine organic solution and the isophthaloyl organic solution are each independently 0.5–15 g / min (e.g., 2 g / min, 4 g / min, 6 g / min, 8 g / min, 10 g / min, 12 g / min, or 14 g / min, etc.), and the feeding time is 50–70 min (e.g., 52 min, 54 min, 56 min, 58 min, 60 min, 62 min, 64 min, 66 min, or 68 min, etc.).

[0068] Preferably, the reaction in step (IV) is carried out in a microreactor at a temperature of 4–6°C (e.g., 4.2°C, 4.4°C, 4.6°C, 4.8°C, 5.0°C, 5.2°C, 5.4°C, 5.6°C, or 5.8°C, etc.), and the feed rates of the prepolymer mixture and the isophthalic acid organic solution are each independently 0.5–15 g / min (e.g., 2 g / min, 4 g / min, 6 g / min, 8 g / min, 10 g / min, 12 g / min, or 14 g / min, etc.), and the feeding time is 70–80 min (e.g., 71 min, 72 min, 73 min, 74 min, 75 min, 76 min, 77 min, 78 min, or 79 min, etc.).

[0069] In a second aspect, the present invention provides an aromatic polyamide film, which is prepared by the preparation method described in the first aspect.

[0070] Thirdly, the present invention provides a composite insulating material comprising meta-aramid paper and an aromatic polyamide film as described in the second aspect.

[0071] Preferably, the composite insulating material comprises a first meta-aramid paper layer, an aromatic polyamide film layer, and a second meta-aramid paper layer stacked sequentially.

[0072] Preferably, each of the first meta-aramid paper layers independently comprises meta-aramid paper.

[0073] Preferably, the aromatic polyamide film layer comprises the aromatic polyamide film as described in the second aspect.

[0074] Compared with the prior art, the present invention has at least the following beneficial effects:

[0075] In this invention, the casting solution is prepared by adding polyamide ester and aromatic polyamide, resulting in low apparent viscosity and good fluidity. The resulting aromatic polyamide film has a small thickness deviation. The composite insulating material prepared by combining aromatic polyamide film with aramid paper has a small thickness deviation, high breakdown voltage, is not easy to delaminate, and has good hot adhesion. The thickness deviation of the aromatic polyamide film is within ±1.2%. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the structure of the composite insulating material provided in Example 1;

[0077] Wherein, 1-first meta-aramid paper layer; 2-aromatic polyamide film layer; 3-second meta-aramid paper layer. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0079] The sources of some of the raw materials used in the following examples and comparative examples are as follows.

[0080] Organosilicon resin: Model SH-916, manufacturer: Hubei Longsheng Sihai New Material Co., Ltd., solid content (150℃, 2h) = 60% ± 2%, viscosity (25℃) not less than 60000cp.

[0081] Example 1

[0082] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The preparation method of the aromatic polyamide film includes the following steps:

[0083] (a) Under nitrogen protection, dianhydride monomer (pyromellitic dianhydride), ethanol and tetrahydrofuran were mixed and heated to reflux at 70°C for 4 h. The molar ratio of dianhydride monomer to ethanol was 1:2 and the mass ratio of dianhydride monomer to tetrahydrofuran was 1:1.6. Then, the dicarboxylic acid ester was obtained by precipitation, washing and drying.

[0084] Under nitrogen protection, the above-mentioned dicarboxylic acid ester was dissolved in N,N-dimethylacetamide. After complete dissolution, diamine monomer (4,4-diaminodiphenyl ether) and catalyst (N,N'-diisopropylcarbodiimide) were added to form a reaction solution. The total concentration of dicarboxylic acid ester and diamine monomer in the reaction solution was 20 wt%, the molar ratio of dicarboxylic acid ester to diamine monomer was 1:1, and the molar ratio of dicarboxylic acid ester to catalyst was 1:0.6. The reaction solution was stirred at room temperature (25°C) for 12 h to obtain a polyamide ester solution.

[0085] (b) Dissolve m-phenylenediamine in freshly distilled, dry first solvent (N,N-dimethylacetamide) at a mass ratio of m-phenylenediamine to first solvent of 1:9.6, stir until homogeneous, and obtain m-phenylenediamine organic solution, then cool to 5°C;

[0086] Isophthaloyl chloride was dissolved in freshly distilled, dry second solvent (toluene) at a mass ratio of 1:1. The mixture was stirred until homogeneous to obtain an organic solution of isophthaloyl chloride, which was then cooled to 5°C.

[0087] The microreactor was turned on and cooled to 5°C. The above m-phenylenediamine organic solution and part of the isophthaloyl organic solution were pumped into the microreactor at feed rates of 13.0 g / min and 3.2 g / min, respectively, and the prepolymerization reaction was carried out at 5°C for 60 min to obtain a prepolymerized mixture.

[0088] The above prepolymer mixture and the remaining isophthalic acid organic solution were pumped into the microreactor at feed rates of 12.9 g / min and 1.1 g / min, respectively, and polymerized at 5 °C for 75 min to obtain an aromatic polyamide solution with an aromatic polyamide mass percentage of 20%.

[0089] (c) The polyamide ester solution obtained in step (a) and the aromatic polyamide solution obtained in step (b) are mixed thoroughly by stirring in a mass ratio of 1:1. The mixture is reacted at room temperature (25°C) for 12 hours and then degassed in a degassing tank at 85°C for 1 hour to obtain a casting solution with a polymer content of 20 wt%.

[0090] (d) The casting liquid obtained in step (c) is cast. After being metered, the casting liquid flows vertically downward from the die lip. The casting temperature is 25°C and the casting speed is 2m / min. It is cooled and stretched in an air layer with a distance of 10mm, and then enters the first coagulation bath and the second coagulation bath for coagulation to form a self-supporting film.

[0091] The first coagulation bath comprises the following components by mass percentage: 15% N,N-dimethylacetamide and 85% water; the temperature of the first coagulation bath is 15°C.

[0092] The second coagulation bath comprises the following components by mass percentage: 30% N,N-dimethylacetamide and 70% water; the temperature of the second coagulation bath is 15°C.

[0093] (e) The self-supporting film obtained in step (d) is subjected to transverse stretching and longitudinal stretching. The transverse stretching temperature is 170°C and the stretching ratio is 1.2. The longitudinal stretching temperature is 380°C and the stretching ratio is 1.1. Finally, it is heat-set on a hot roller at 390°C to obtain the aromatic polyamide film.

[0094] The composite insulating material, such as Figure 1 As shown, it includes a first meta-aramid paper layer 1, an aromatic polyamide film layer 2, and a second meta-aramid paper layer 3 stacked sequentially, with an average thickness of 0.13 mm;

[0095] The first meta-aramid paper layer 1 is aramid paper with an average thickness of 0.052 mm;

[0096] The aromatic polyamide film layer 2 is the aforementioned aromatic polyamide film with an average thickness of 25 μm;

[0097] The second meta-aramid paper layer 3 is aramid paper with an average thickness of 0.052 mm;

[0098] The composite insulating material is prepared by the following method: an aromatic polyamide film is immersed in an impregnation tank (the adhesive in the impregnation tank is silicone resin of model SH-916) to impregnate both sides of the aromatic polyamide film, excess adhesive is removed by a scraper, and the film is dried. Then, the upper and lower surfaces of the aromatic polyamide film are hot-rolled and laminated with aramid paper using a hot rolling mill (temperature is 250℃, pressure is 20kg / cm, time is 5min) to obtain the composite insulating material.

[0099] Example 2

[0100] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The preparation method of the aromatic polyamide film includes the following steps:

[0101] (a) Under nitrogen protection, dianhydride monomer (pyromellitic dianhydride), ethanol and tetrahydrofuran were mixed and heated to reflux at 70°C for 4 h. The molar ratio of dianhydride monomer to ethanol was 1:2 and the mass ratio of dianhydride monomer to tetrahydrofuran was 1:1.5. Then, the dicarboxylic acid ester was obtained by precipitation, washing and drying.

[0102] Under nitrogen protection, the above-mentioned dicarboxylic acid ester was dissolved in N,N-dimethylacetamide. After complete dissolution, diamine monomer (4,4-diaminodiphenyl ether) and catalyst (N,N'-diisopropylcarbodiimide) were added to form a reaction solution. The total concentration of dicarboxylic acid ester and diamine monomer in the reaction solution was 18 wt%, the molar ratio of dicarboxylic acid ester to diamine monomer was 1:1, and the molar ratio of dicarboxylic acid ester to catalyst was 1:1. The reaction solution was stirred at room temperature (25°C) for 12 h to obtain a polyamide ester solution.

[0103] (b) Dissolve m-phenylenediamine in freshly distilled, dry first solvent (N,N-dimethylacetamide) at a mass ratio of 1:10, stir until homogeneous, and obtain an organic solution of m-phenylenediamine. Cool to 5°C.

[0104] Isophthaloyl chloride was dissolved in freshly distilled, dry second solvent (toluene) at a mass ratio of 1:1.5. The mixture was stirred until homogeneous to obtain an organic solution of isophthaloyl chloride, which was then cooled to 5°C.

[0105] The microreactor was turned on and cooled to 5°C. The above m-phenylenediamine organic solution and part of the isophthaloyl organic solution were pumped into the microreactor at feed rates of 12.1 g / min and 3.4 g / min, respectively, and the prepolymerization reaction was carried out at 5°C for 60 min to obtain a prepolymerized mixture.

[0106] The above prepolymer mixture and the remaining isophthalic acid organic solution were pumped into the microreactor at feed rates of 12.4 g / min and 1.4 g / min, respectively, and polymerized at 5 °C for 75 min to obtain an aromatic polyamide solution with an aromatic polyamide mass percentage of 18%.

[0107] (c) The polyamide ester solution obtained in step (a) and the aromatic polyamide solution obtained in step (b) are thoroughly stirred and mixed evenly at a mass ratio of 1.4:1. The mixture is reacted at room temperature (25°C) for 12 hours and degassed at 80°C for 1.5 hours in a degassing tank to obtain a casting solution with a polymer content of 18 wt%.

[0108] (d) The casting liquid obtained in step (c) is cast. After being metered, the casting liquid flows vertically downward from the die lip. The casting temperature is 25°C and the casting speed is 5m / min. It is cooled and stretched in an air layer with a distance of 10mm, and then enters the first coagulation bath and the second coagulation bath for coagulation to form a self-supporting film.

[0109] The first coagulation bath comprises the following components by mass percentage: 20% N,N-dimethylacetamide and 80% water; the temperature of the first coagulation bath is 5°C;

[0110] The second coagulation bath comprises the following components by mass percentage: 40% N,N-dimethylacetamide and 20% water; the temperature of the second coagulation bath is 5°C.

[0111] (e) The self-supporting film obtained in step (d) is subjected to transverse stretching and longitudinal stretching. The transverse stretching temperature is 180°C and the stretching ratio is 1.3. The longitudinal stretching temperature is 360°C and the stretching ratio is 1.2. Finally, it is heat-set on a hot roller at 370°C to obtain the aromatic polyamide film.

[0112] The composite insulating material comprises a first meta-aramid paper layer, an aromatic polyamide film layer, and a second meta-aramid paper layer stacked sequentially, with an average thickness of 0.13 mm.

[0113] The first meta-aramid paper layer is aramid paper with an average thickness of 0.052 mm;

[0114] The aromatic polyamide film layer is the aforementioned aromatic polyamide film, with an average thickness of 25 μm;

[0115] The second meta-aramid paper layer is aramid paper with an average thickness of 0.052 mm;

[0116] The composite insulating material is prepared by the following method: an aromatic polyamide film is immersed in an impregnation tank (the adhesive in the impregnation tank is an organosilicon resin of model SH-916) to impregnate both sides of the aromatic polyamide film, excess adhesive is removed by a scraper, and the film is dried. Then, the upper and lower surfaces of the aromatic polyamide film are hot-rolled and laminated with aramid paper using a hot rolling mill (temperature is 220℃, pressure is 50kg / cm, time is 10min) to obtain the composite insulating material.

[0117] Example 3

[0118] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The preparation method of the aromatic polyamide film includes the following steps:

[0119] (a) Under nitrogen protection, dianhydride monomer (pyromellitic dianhydride), ethanol and tetrahydrofuran were mixed and heated to reflux at 70°C for 4 h. The molar ratio of dianhydride monomer to ethanol was 1:2 and the mass ratio of dianhydride monomer to tetrahydrofuran was 1:1.8. Then, the dicarboxylic acid ester was obtained by precipitation, washing and drying.

[0120] Under nitrogen protection, the above-mentioned dicarboxylic acid ester was dissolved in N,N-dimethylacetamide. After complete dissolution, diamine monomer (4,4-diaminodiphenyl ether) and catalyst (N,N'-diisopropylcarbodiimide) were added to form a reaction solution. The total concentration of dicarboxylic acid ester and diamine monomer in the reaction solution was 20 wt%, the molar ratio of dicarboxylic acid ester to diamine monomer was 1:1, and the molar ratio of dicarboxylic acid ester to catalyst was 1:0.5. The reaction solution was stirred at room temperature (25°C) for 12 h to obtain a polyamide ester solution.

[0121] (b) Dissolve m-phenylenediamine in freshly distilled, dry first solvent (N,N-dimethylacetamide) at a mass ratio of 1:10, stir until homogeneous, and obtain an organic solution of m-phenylenediamine. Cool to 5°C.

[0122] Isophthaloyl chloride was dissolved in freshly distilled, dry second solvent (toluene) at a mass ratio of 1:1.5. The mixture was stirred until homogeneous to obtain an organic solution of isophthaloyl chloride, which was then cooled to 5°C.

[0123] The microreactor was turned on and cooled to 5°C. The above m-phenylenediamine organic solution and part of the isophthaloyl organic solution were pumped into the microreactor at feed rates of 12.1 g / min and 3.4 g / min, respectively, and the prepolymerization reaction was carried out at 5°C for 60 min to obtain a prepolymerized mixture.

[0124] The above prepolymer mixture and the remaining isophthalic acid organic solution were pumped into the microreactor at feed rates of 12.4 g / min and 1.4 g / min, respectively, and polymerized at 5 °C for 75 min to obtain an aromatic polyamide solution with an aromatic polyamide mass percentage of 18%.

[0125] (c) The polyamide ester solution obtained in step (a) and the aromatic polyamide solution obtained in step (b) are thoroughly stirred and mixed evenly at a mass ratio of 1.5:1. The mixture is reacted at room temperature (25°C) for 12 hours and degassed at 90°C for 0.5 hours in a degassing tank to obtain a casting solution with a polymer content of 19 wt%.

[0126] (d) The casting liquid obtained in step (c) is cast. After being metered, the casting liquid flows vertically downward from the die lip. The casting temperature is 25°C and the casting speed is 4m / min. It is cooled and stretched in an air layer with a distance of 10mm, and then enters the first coagulation bath and the second coagulation bath for coagulation to form a self-supporting film.

[0127] The first coagulation bath comprises the following components by mass percentage: 10% N,N-dimethylacetamide and 90% water; the temperature of the first coagulation bath is 10°C.

[0128] The second coagulation bath comprises the following components by mass percentage: 25% N,N-dimethylacetamide and 75% water; the temperature of the second coagulation bath is 10°C.

[0129] (e) The self-supporting film obtained in step (d) is subjected to transverse stretching and longitudinal stretching. The transverse stretching temperature is 160°C and the stretching ratio is 1.1. The longitudinal stretching temperature is 390°C and the stretching ratio is 1.1. Finally, it is heat-set on a hot roller at 400°C to obtain the aromatic polyamide film.

[0130] The composite insulating material comprises a first meta-aramid paper layer, an aromatic polyamide film layer, and a second meta-aramid paper layer stacked sequentially, with an average thickness of 0.13 mm.

[0131] The first meta-aramid paper layer is aramid paper with an average thickness of 0.052 mm;

[0132] The aromatic polyamide film layer is the aforementioned aromatic polyamide film, with an average thickness of 25 μm;

[0133] The second meta-aramid paper layer is aramid paper with an average thickness of 0.052 mm;

[0134] The composite insulating material is prepared by the following method: an aromatic polyamide film is immersed in an impregnation tank (the adhesive in the impregnation tank is silicone resin of model SH-916) to impregnate both sides of the aromatic polyamide film, excess adhesive is removed by a scraper, and the film is dried. Then, the upper and lower surfaces of the aromatic polyamide film are hot-rolled and laminated with aramid paper using a hot rolling mill (temperature is 235℃, pressure is 40kg / cm, time is 8min) to obtain the composite insulating material.

[0135] Example 4

[0136] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The difference between this embodiment and Embodiment 1 is that the mass ratio of the polyamide ester solution and the aromatic polyamide solution in step (c) is adjusted to 0.5:1, while other conditions are the same as in Embodiment 1.

[0137] Example 5

[0138] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The difference between this embodiment and Embodiment 1 is that the mass ratio of the polyamide ester solution and the aromatic polyamide solution in step (c) is adjusted to 2:1, while other conditions are the same as in Embodiment 1.

[0139] Example 6

[0140] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The difference between this embodiment and Example 1 is that the concentration of dicarboxylic acid ester and diamine monomer in the reaction solution in step (a) is 25 wt%, and the mass ratio of intermediate phenylenediamine to the first solvent in step (b) is 1:7.5, and the mass ratio of isophthaloyl chloride to the second solvent is 1:0.6, so that the polymer content in the casting solution is 25 wt%. The aromatic polyamide film obtained has an average thickness of 28 μm. Other conditions are the same as in Example 1.

[0141] Example 7

[0142] This embodiment provides an aromatic polyamide film, its preparation method, and a composite insulating material. The difference between this embodiment and Embodiment 1 is that the stretching ratio of the transverse stretching of the aromatic polyamide film is reduced, the thickness of the aromatic polyamide film is increased, the average thickness of the aromatic polyamide film is adjusted to 75 μm, and the average thickness of the composite insulating material is adjusted to 0.18 mm. Other conditions are the same as in Embodiment 1.

[0143] Comparative Example 1

[0144] This comparative example provides an aromatic polyamide film, its preparation method, and a composite insulating material. The difference between this example and Example 1 is that step (a) is not included, and polyamide ester solution is not added in step (c). Other conditions are the same as in Example 1.

[0145] Comparative Example 2

[0146] This comparative example provides a composite insulating material, which differs from Example 1 in that the aromatic polyamide film layer is replaced with a polyimide film layer in the composite insulating material; the polyimide film layer is a polyimide film with an average thickness of 25 μm, and other conditions are the same as in Example 1.

[0147] Comparative Example 3

[0148] This comparative example provides a composite insulating material, which differs from Example 8 in that the aromatic polyamide film layer is replaced with a polyimide film layer; the polyimide film layer is a polyimide film with an average thickness of 75 μm, and other conditions are the same as in Example 8.

[0149] The casting solutions, aromatic polyamide films, and composite insulating materials provided in Examples 1-7 and Comparative Examples 1-3 were subjected to the following performance tests.

[0150] (1) Apparent viscosity of casting solution: The apparent viscosity of casting solution at 25℃ was tested using a rotational viscometer. (2) Average thickness and thickness deviation of aromatic polyamide film: The test was conducted in accordance with GB / T 6672-2001. The resolution of the thickness gauge should not be greater than 0.1 μm. The thickness measurement points should be measured at equal intervals of at least 3 points in the transverse direction as a group, and at 200 mm intervals in the longitudinal direction as a group, for a total of 5 groups. The average thickness and thickness deviation were then calculated.

[0151] (3) Average thickness and thickness deviation rate of composite insulation material: Refer to the provisions of GB / T 6672-2001. The resolution of the thickness gauge should not be greater than 0.1μm. The thickness measurement points should be tested at equal intervals along the transverse direction, with no less than 3 points as a group, and a group of 200mm intervals along the longitudinal direction, for a total of 5 groups of tests. The average thickness and thickness deviation are then calculated.

[0152] (4) Breakdown voltage of composite insulation material: Cut 100mm×100mm composite insulation material to ensure no creases or contamination. Equilibrate for 24 hours under the conditions of temperature 23±2℃ and humidity 50±5%RH. Then lay it flat between the electrodes and apply appropriate pressure to ensure tight contact and avoid air gaps. Increase the voltage at a rate of 2000V / s until breakdown. Record the instantaneous voltage value. Hold for 1 minute after each stage of voltage increase to evaluate the withstand voltage stability of the material. Monitor the voltage and leakage current in real time. The breakdown judgment threshold is a sudden current increase ≥1mA or a sudden voltage drop ≥10%. Each group should be tested at least 5 times. After removing abnormal values ​​with a deviation >15%, take the average value as the breakdown voltage.

[0153] (5) Hot adhesion of composite insulating materials: [The following is a sample of an area of ​​approximately 100 cm²] 2 The composite insulating material was subjected to heat treatment at a temperature of 200℃ for 10 minutes, and the presence of bubbles, delamination or other adverse effects was observed.

[0154] The test results are shown in Table 1 below.

[0155] Table 1

[0156]

[0157]

[0158] In Table 1, " / " indicates that the test was not performed.

[0159] As shown in Table 1, the casting solution prepared by the aromatic polyamide film preparation methods provided in Examples 1 to 7 has a low apparent viscosity, and the thickness deviation of the prepared aromatic polyamide film is small. The composite insulating material prepared by combining aromatic polyamide film with aramid paper has a small thickness deviation, high breakdown voltage, is not easy to delaminate, and has good hot adhesion.

[0160] Compared with Example 1, if the mass ratio of polyamide ester to aromatic polyamide is lower (Example 4), the apparent viscosity of the casting solution is higher and the fluidity of the casting solution is poor, resulting in a large thickness deviation of the aromatic polyamide film; if the mass ratio of polyamide ester to aromatic polyamide is higher (Example 5), the apparent viscosity is lower and the flow is stronger and difficult to control.

[0161] Compared to Example 1, if the solid content of the casting solution is too high (Example 6), the apparent viscosity of the casting solution increases and the fluidity is poor.

[0162] Compared to Example 1, if no polyamide ester solution (Comparative Example 1) is added, the apparent viscosity of the casting solution increases, resulting in poor fluidity and a large thickness deviation in the aromatic polyamide film.

[0163] Compared with Comparative Example 2, Example 1, and Comparative Example 3, showed that if the aromatic polyamide film layer was replaced with a polyimide film layer, the breakdown voltage of the prepared composite insulating material was reduced and the hot adhesion was poor.

[0164] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an aromatic polyamide film, characterized in that, The preparation method includes the following steps: casting liquid is subjected to casting, solidification, biaxial stretching and heat setting to obtain the aromatic polyamide film; The raw materials for preparing the casting solution include polyamide ester, aromatic polyamide, and solvent.

2. The preparation method according to claim 1, characterized in that, The polymer content in the casting solution is 15wt% to 25wt%, more preferably 18wt% to 20wt%; Preferably, the mass ratio of the polyamide ester to the aromatic polyamide is (0.5-2.0):1, more preferably (1.0-1.6):1; Preferably, the apparent viscosity of the casting solution at 25°C is 2000–4000 poise; Preferably, the solvent comprises any one or a combination of at least two of N,N-dimethylacetamide, N-methyl-2-pyrrolidone, toluene, chlorobenzene, dichloroethane, xylene, trimethylbenzene, or 2-methylpyridine; Preferably, the aromatic polyamide comprises meta-aramid.

3. The preparation method according to claim 1 or 2, characterized in that, The process before casting also includes defoaming and filtration steps; Preferably, the degassing includes degassing in a degassing tank at a temperature of 80–90°C for a time of 0.5–1.5 hours. Preferably, the casting temperature is 20–30°C; Preferably, the casting speed is 2-5 m / min; Preferably, the casting process further includes cooling and stretching / orientation steps; Preferably, the cooling and stretching orientation are carried out in an air layer of 5–25 mm. Preferably, the solidification includes solidification in a first solidification bath and a second solidification bath; Preferably, the first coagulation bath comprises the following components by mass percentage: 10%–20% N,N-dimethylacetamide and 80%–90% water; Preferably, the second coagulation bath comprises the following components by mass percentage: 20%–45% N,N-dimethylacetamide and 55%–80% water; Preferably, the temperatures of the first coagulation bath and the second coagulation bath are independently 2–20°C. Preferably, the bidirectional tension includes transverse tension and longitudinal tension; Preferably, the temperature for the transverse stretching is 150–180°C; Preferably, the stretching ratio of the transverse stretching is 1.1 to 1.3; Preferably, the temperature of the longitudinal stretching is 350–400°C; Preferably, the longitudinal stretching ratio is 1.01 to 1.2; Preferably, the heat setting temperature is 350–400°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The casting solution is prepared by the following method: mixing a polyamide ester solution, an aromatic polyamide solution and an optional solvent, and reacting to obtain the casting solution; Preferably, the polyamide oil solution contains 18 wt% to 25 wt% of polyamide oil by mass. Preferably, the specific logarithmic viscosity of the aromatic polyamide solution at 25°C is 1.8–2.3 dL / g; Preferably, the aromatic polyamide solution contains 18 wt% to 25 wt% aromatic polyamide by mass. Preferably, the reaction temperature is 20–30°C; Preferably, the reaction time is 10 to 15 hours.

5. The preparation method according to claim 4, characterized in that, The polyamide ester solution was prepared using the following method: (1) Mix dianhydride monomer, ethanol and tetrahydrofuran, and react to obtain dicarboxylic acid ester; (2) The dicarboxylic acid ester, diamine monomer, catalyst and N,N-dimethylacetamide obtained in step (1) are mixed and reacted to obtain the polyamide ester solution; Preferably, the dianhydride monomer comprises pyromellitic dianhydride; Preferably, the molar ratio of the dianhydride monomer to ethanol is 1:(1.9-2.1); Preferably, the mass ratio of the dianhydride monomer to tetrahydrofuran is 1:(1.5-1.8); Preferably, the reaction temperature in step (1) is 60-80°C, and the reaction time is 3-5 hours. Preferably, step (1) further includes precipitation, washing, and drying after the reaction; Preferably, the molar ratio of the dicarboxylic acid ester to the diamine monomer is 1:(0.9-1.1); Preferably, the molar ratio of the dicarboxylic acid ester to the catalyst is 1:(0.5-1.0); Preferably, the diamine monomer comprises 4,4-diaminodiphenyl ether; Preferably, the catalyst comprises N,N'-diisopropylcarbodiimide; Preferably, the reaction temperature in step (2) is 20-30°C, and the reaction time is 10-15 hours. Preferably, the reactions in steps (1) and (2) are carried out under nitrogen protection.

6. The preparation method according to claim 4 or 5, characterized in that, The aromatic polyamide solution was prepared by the following method: (I) Mix m-phenylenediamine and the first solvent to obtain an organic solution of m-phenylenediamine; (II) Mix isophthaloyl chloride and the second solvent to obtain an organic solution of isophthaloyl chloride; (III) Mix m-phenylenediamine organic solution and part of isophthalamide organic solution, react, and obtain prepolymer mixture; (IV) The prepolymer mixture obtained in step (III) is mixed with the remaining isophthalic acid organic solution and reacted to obtain the aromatic polyamide solution; Steps (Ⅰ) and (Ⅱ) can be performed sequentially or simultaneously, regardless of the order in which they are performed.

7. The preparation method according to claim 6, characterized in that, The molar ratio of m-phenylenediamine to isophthaloyl chloride is (1-1.1):1; Preferably, the first solvent comprises N,N-dimethylacetamide and / or N-methyl-2-pyrrolidone; Preferably, the mass ratio of m-phenylenediamine to the first solvent is 1:(9.5-12); Preferably, the second solvent comprises any one or a combination of at least two of toluene, chlorobenzene, dichloroethane, xylene, trimethylbenzene, or 2-methylpyridine; Preferably, the mass ratio of isophthaloyl chloride to the second solvent is 1:(1-3); Preferably, based on the total mass of the isophthaloyl chloride organic solution being 100%, the mass of the isophthaloyl organic solution in the said portion is 60% to 80%. Preferably, the reaction in step (III) is carried out in a microreactor at a temperature of 4–6 °C, and the feed rates of the m-phenylenediamine organic solution and the isophthaloyl organic solution are each 0.5–15 g / min independently, with a feeding time of 50–70 min. Preferably, the reaction in step (IV) is carried out in a microreactor at a temperature of 4–6 °C, and the feed rates of the prepolymer mixture and the isophthalic acid organic solution are each 0.5–15 g / min independently, with a feeding time of 70–80 min.

8. An aromatic polyamide film, characterized in that, The aromatic polyamide film is prepared by the preparation method according to any one of claims 1 to 7.

9. A composite insulating material, characterized in that, The composite insulating material includes meta-aramid paper and the aromatic polyamide film as described in claim 8.

10. The composite insulating material according to claim 9, characterized in that, The composite insulating material comprises a first meta-aramid paper layer, an aromatic polyamide film layer, and a second meta-aramid paper layer, which are sequentially stacked. Each of the first meta-aramid paper layers independently comprises meta-aramid paper; The aromatic polyamide film layer includes the aromatic polyamide film as described in claim 8.

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