CN113929942B - Preparation method of meta-aramid film with high dielectric strength - Google Patents
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- C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
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Abstract
The invention belongs to the field of high-performance film materials, and particularly discloses a preparation method of a meta-aramid film with high dielectric strength, which comprises the following steps: preparing a polymerization solution and preparing a meta-aramid film; the thickness of the meta-aramid film is 5-200um, the dielectric strength can reach 30-50kV/mm, and the meta-aramid film is transparent, compact in structure and free of bubbles or micropores in the film. The preparation method of the meta-aramid film overcomes the limitations of the crystallization behavior, viscosity and solvent of the meta-aramid by controlling the preparation process parameters of the meta-aramid film, solves the problems of difficult formation, complex process, easy breakage and easy curling deformation of the meta-aramid film, has the characteristics of simple equipment, mild process, convenient operation, uniform and controllable thickness and the like, and effectively improves the maturity of the meta-aramid film preparation technology.
Description
Technical Field
The invention belongs to the field of high-performance film materials, and particularly relates to a preparation method of a meta-aramid film with high dielectric strength.
Background
Meta-aramid has the characteristics of excellent high temperature resistance, good dimensional stability, excellent spinnability, fire resistance, corrosion resistance and the like, and is widely applied to the fields of high-temperature filtration, automobile rubber tubes, firefighters, transformer insulating materials, honeycomb structural materials and the like.
The meta-aramid film has the characteristics of flexibility, high temperature resistance, stable size, corrosion resistance and the like, but the meta-aramid film is limited by self viscosity and solvent in the forming process, so that the meta-aramid film has very strict requirements on forming process parameters, and no mature meta-aramid film preparation method exists at present.
The patent CN103908903A is prepared by casting an aramid solution into a film, gelling the film in water to obtain an aramid film, and then dipping the aramid film in fluorine-containing epoxy resin to obtain the aramid film with self-cleaning function, but the self-cleaning aramid film prepared by the method has the advantages of complex preparation process, poor electrical insulation performance, uneven surface and poor uniformity.
Patent US005536408A reports a hydrophilic, asymmetric, chemically stable modified para-aramid film, wherein a modified para-aramid film is synthesized in NMP to form a casting solution, and then the film is formed by adopting an L-S phase inversion method, but the process of the method is complex, and the prepared modified para-aramid film has poor electrical insulation performance.
The patent CN104464973A uses knife coating method to form film from aramid fiber solution, then sprays nano silver wire ethanol dispersion liquid, heats and dries to obtain high-strength aramid fiber transparent conductive film, but the aramid fiber film prepared by the method has no electrical insulation performance, and the ethanol can damage the flatness of the aramid fiber film.
The preparation methods of the polymer film materials commonly used at present include a screen printing method, an ink-jet printing method, a spray pyrolysis method and the like, but meta-aramid is limited by the crystallization behavior, viscosity and solvent properties of the meta-aramid, and the meta-aramid film with uniform performance cannot be obtained by adopting the common film material preparation method. However, the meta-aramid film has excellent flexibility, intrinsic flame retardance, mechanical property and dielectric property, and has great application potential in flexible equipment.
Disclosure of Invention
The invention provides a preparation method of a meta-aramid film with high dielectric strength, which aims to solve the problem that the crystallization behavior, viscosity and solvent of meta-aramid are easily limited, and the meta-aramid film with uniform performance cannot be obtained by adopting a common film material preparation method.
In order to achieve the above purpose, the invention provides a preparation method of a meta-aramid film with high dielectric strength, which comprises the following steps:
step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into a solvent for polymerization reaction at room temperature under a nitrogen drying environment under the stirring condition, adding a neutralizing agent, neutralizing hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution, wherein the mass concentration of the polymer is 5-40%;
step 2: preparing a meta-aramid film: and (3) uniformly mixing the polymerization solution prepared in the step (1) with a release agent after stirring, uniformly coating the mixture on the surface of a smooth substrate by using a film material film-making method, and drying the mixture in a multi-stage manner to completely volatilize the solvent, wherein the film removed from the surface of the smooth substrate is the meta-aramid film.
Further, the nitrogen pressure in the step 1 is 0.03MPa; the solvent is one of N, N-dimethylformamide or N, N-dimethylacetamide.
Further, the neutralizing agent in the step 1 is one of calcium oxide, calcium hydroxide or ammonia gas.
Further, the viscosity of the polymerization solution in the step 1 reaches 10-9000P at 50 ℃.
Furthermore, the release agent in the step 2 is one or more of fatty acid, paraffin, glycerol, vaseline, silicone oil, polyethylene glycol, low molecular weight polyethylene, boron nitride, polytetrafluoroethylene wax and propylene oxide derivatives, and the use amount of the release agent is 0.001-0.01 per mill of the mass concentration of the polymerization solution.
Further, the film forming method in the step 2 is one of a spin coater method, a dip-pull coating method, a bar coating method and a blade coating method.
Further, the smooth substrate in the step 2 is one of a metal plate, toughened glass, a polyimide film, a polyester film, a polyether-ether-ketone film, a polytetrafluoroethylene film and a polyethylene naphthalate film; the surface roughness of the smooth substrate surface in the step 2 is Ra:0.006-0.16.
Further, the multistage drying process in the step 2 is that the drying is firstly carried out for 10-30 minutes at 50-60 ℃, then for 10-30 minutes at 70-80 ℃, and finally for 30-60 minutes at 90-110 ℃.
Further, the average thickness of the intermediate aramid film in the step 2 is 5-200um, the dielectric strength reaches 30-50kV/mm, and the dielectric constant is 3-4 at the frequency of 5 GHz.
Further, the meta-aramid film with high dielectric strength prepared by any one of the preparation methods.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the preparation method of the meta-aramid film overcomes the limitations of the crystallization behavior, viscosity and solvent of the meta-aramid by controlling the preparation process parameters of the meta-aramid film, solves the problems of difficult formation, complex process, easy breakage and easy curling deformation of the meta-aramid film, has the characteristics of simple equipment, mild process, convenient operation, uniform and controllable thickness and the like, and effectively improves the maturity of the meta-aramid film preparation technology.
2. The meta-aramid film provided by the invention is transparent, compact in structure, free of bubbles or micropores in the film, and uniform and controllable in thickness within the range of 5-200 mu m, and has dielectric strength of 30-50kV/mm and dielectric constant of 3-4 (at 5GHz frequency).
3. The preparation method of the meta-aramid film provided by the invention maintains better molecular structural integrity after the film is formed by the aramid polymer liquid, so that the inherent characteristics of high strength and high modulus, intrinsic flame retardance, high temperature resistance, low dielectric property, good flexibility, bending resistance, ageing resistance, long service life, low cost and the like of the aramid are reserved, and the preparation method can be applied to the fields of flexible circuit boards, flexible display screens, wearable electronic equipment, composite materials and the like.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a flow chart of the preparation of the meta-aramid film of the present invention.
FIG. 2 is an optical micrograph at 100 Xmagnification of a meta-aramid film prepared in example 2 of the present invention.
FIG. 3 is an optical micrograph at 100 Xmagnification of a meta-aramid film prepared in example 5 of the present invention.
Detailed Description
The invention will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The following detailed description is exemplary and is intended to provide further details of the invention. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention.
FIG. 1 shows a flow chart of the preparation of the meta-aramid film with high dielectric strength:
example 1
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide to perform polymerization reaction at room temperature under the condition of stirring and nitrogen drying at the pressure of 0.03MPa, then adding a neutralizing agent of calcium oxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 6000P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 30%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is fatty acid, silicone oil and epoxypropane derivative, and the mass ratio of the fatty acid to the silicone oil to the epoxypropane derivative is 1:1:1, the using amount of the release agent is 0.002 per mill of the mass concentration of the polymerization solution; the polymer solution was uniformly coated on the surface roughness Ra with a wire rod coater having a diameter of 500um and a coating speed of 5 m/min: and (3) drying the surface of the toughened glass of 0.16 in a multistage manner, firstly drying at 60 ℃ for 20 minutes, then drying at 80 ℃ for 20 minutes, finally drying at 100 ℃ for 60 minutes to enable the solvent to be completely volatilized, and taking off the film from the smooth substrate surface to obtain the meta-aramid film, wherein the average thickness of the obtained meta-aramid film is 140um.
Example 2
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide under the condition of stirring at room temperature and under the condition of nitrogen drying at the pressure of 0.03MPa, adding a neutralizing agent of calcium hydroxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 9000P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 40%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is paraffin, glycerol and vaseline, and the mass ratio of the paraffin to the glycerol to the vaseline is 1:1:1, the using amount of the release agent is 0.01 per mill of the mass concentration of the polymerization solution; the polymerization solution is coated on the surface roughness Ra uniformly by a dipping-pulling coating method, wherein the vertical pulling speed is 10 cm/min: and (3) drying the surface of the smooth polyether-ether-ketone film of 0.10 in a multistage manner, firstly drying at 60 ℃ for 30 minutes, then drying at 80 ℃ for 30 minutes, and finally drying at 110 ℃ for 60 minutes to enable the solvent to volatilize completely, wherein the film removed from the surface of the smooth polyether-ether-ketone film is a meta-aramid film, and the average thickness of the obtained meta-aramid film is 200 microns.
Example 3
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylacetamide under the condition of stirring at room temperature and under the condition of 0.03MPa pressure and nitrogen drying, performing polymerization reaction, adding ammonia as a neutralizing agent, neutralizing hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 3000P at 50 ℃, wherein the mass concentration of the polymerization substance is 20%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is polyethylene glycol, low molecular weight polyethylene and boron nitride, and the mass ratio of the polyethylene glycol to the low molecular weight polyethylene to the boron nitride is 1:1:1, the using amount of the release agent is 0.003 per mill of the mass concentration of the polymerization solution; the polymerization solution is coated on the surface roughness Ra uniformly by a dipping-pulling coating method, wherein the vertical pulling speed is 100 cm/min: and (3) drying the surface of the smooth stainless steel plate of 0.05 in a multistage manner, firstly drying at 50 ℃ for 10 minutes, then drying at 70 ℃ for 10 minutes, and finally drying at 90 ℃ for 30 minutes to enable the solvent to volatilize completely, wherein the film removed from the surface of the smooth stainless steel plate is a meta-aramid film, and the average thickness of the obtained meta-aramid film is 100um.
Example 4
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylacetamide under the condition of stirring at room temperature and under the condition of nitrogen drying at the pressure of 0.03MPa, performing polymerization reaction, adding a neutralizing agent calcium oxide, neutralizing hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 1500P at 50 ℃, wherein the mass concentration of the polymerization solution is 15%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is polytetrafluoroethylene wax, and the use amount of the release agent is 0.001 per mill of the mass concentration of the polymerization solution; the polymerization solution was uniformly applied to the surface roughness Ra by a spin coater having a spin speed of 1000 rpm: 0.01 is dried on the smooth polyimide surface in a multistage manner, firstly, the polyimide surface is dried for 20 minutes at 50 ℃, then is dried for 20 minutes at 70 ℃, finally is dried for 40 minutes at 100 ℃ to enable the solvent to be completely volatilized, and the film removed from the smooth polyimide surface is the meta-aramid film, and the average thickness of the obtained meta-aramid film is 50um.
Example 5
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylacetamide under the condition of stirring at room temperature and under the condition of nitrogen drying at the pressure of 0.03MPa, adding a neutralizing agent of calcium hydroxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain the polymerization solution with the viscosity of 800P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymerization solution is 10%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is fatty acid, silicone oil and epoxypropane derivative, and the mass ratio of the fatty acid to the silicone oil to the epoxypropane derivative is 1:1:1, the using amount of the release agent is 0.004 per mill of the mass concentration of the polymer solution; the polymerization solution was uniformly applied to the surface roughness Ra by a spin coater having a spin speed of 2000 rpm: the 0.006 smooth polyester film surface is dried in a multistage manner, firstly dried at 50 ℃ for 10 minutes, then dried at 70 ℃ for 30 minutes, finally dried at 110 ℃ for 50 minutes, so that the solvent is completely volatilized, and the film removed from the smooth polyester film surface is a meta-aramid film, wherein the average thickness of the obtained meta-aramid film is 30um.
Example 6
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylacetamide under the condition of stirring at room temperature and under the condition of nitrogen drying at the pressure of 0.03MPa, adding a neutralizing agent of calcium oxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain the polymerization solution with the viscosity reaching 10P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymerization solution is 5%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is paraffin, silicone oil and boron nitride, and the mass ratio of the paraffin to the silicone oil to the boron nitride is 1:1:1, the using amount of the release agent is 0.005 per mill of the mass concentration of the polymerization solution; the polymer liquid is coated on the surface with a doctor blade coating method, the coating speed of the doctor blade is 4m/min, and the surface roughness Ra is uniformly coated: and (3) drying the smooth polytetrafluoroethylene film surface of 0.008 in a multistage manner, firstly drying at 50 ℃ for 10 minutes, then drying at 70 ℃ for 10 minutes, and finally drying at 90 ℃ for 30 minutes to enable the solvent to volatilize completely, wherein the film removed from the smooth polytetrafluoroethylene film surface is a meta-aramid film, and the average thickness of the obtained meta-aramid film is 5um.
Example 7
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylacetamide under the condition of stirring at room temperature and under the condition of nitrogen drying at the pressure of 0.03MPa, adding a neutralizing agent of calcium hydroxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 2100P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 18%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is polyethylene glycol, silicone oil, low molecular weight polyethylene and propylene oxide derivatives, and the mass ratio of the polyethylene glycol, the silicone oil, the low molecular weight polyethylene and the propylene oxide derivatives is 1:1:1:1, the using amount of the release agent is 0.01 per mill of the mass concentration of the polymerization solution; the polymer liquid is coated on the surface with a doctor blade coating method, the doctor blade coating speed is 8m/min, and the polymer liquid is uniformly coated on the surface roughness Ra:0.02, drying the surface of the smooth polyethylene naphthalate film in a multistage manner, firstly drying the film at 50 ℃ for 10 minutes, then drying the film at 70 ℃ for 20 minutes, and finally drying the film at 100 ℃ for 40 minutes to completely volatilize the solvent, wherein the film removed from the surface of the smooth substrate is a meta-aramid film, and the average thickness of the obtained meta-aramid film is 80 microns.
Example 8
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide to perform polymerization reaction at room temperature under the condition of stirring and nitrogen drying at the pressure of 0.03MPa, then adding ammonia as a neutralizing agent to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 4500P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 24%;
step 2: preparing a meta-aramid film: the polymerization solution prepared in the step 1 is stirred and then uniformly mixed with a release agent, wherein the release agent is polyethylene glycol, low molecular weight polyethylene and polytetrafluoroethylene wax (the mass ratio of the polyethylene glycol to the low molecular weight polyethylene to the polytetrafluoroethylene wax is 1:1:1), the release agent is used in an amount of 0.008 per mill of the mass concentration of the polymerization solution, the polymerization solution is uniformly coated on the smooth copper plate surface with the surface roughness Ra of 0.08 by a wire rod coater with the diameter of 500 mu m at the coating speed of 6m/min, the mixture is dried in a multistage manner, the mixture is dried at the temperature of 60 ℃ for 20 minutes and then dried at the temperature of 80 ℃ for 50 minutes, the solvent is completely volatilized, the film removed from the smooth substrate surface is the meta-aramid film, and the average thickness of the obtained meta-aramid film is 120 mu m.
Example 9
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide to perform polymerization reaction at room temperature under the condition of stirring and nitrogen drying at the pressure of 0.03MPa, then adding a neutralizing agent of calcium oxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity of 7500P at 50 ℃, wherein the mass concentration of the polymer is 35%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, wherein the release agent is glycerin, vaseline, silicone oil and polyethylene glycol, and the mass ratio of the glycerin to the Vaseline to the silicone oil to the polyethylene glycol is 1:1:1:1, the using amount of the release agent is 0.001 per mill of the mass concentration of the polymerization solution; the polymer solution was uniformly coated on the surface roughness Ra with a bar coater having a diameter of 550um and a coating speed of 1 m/min: and (3) drying the smooth silver plate surface of 0.10 in a multistage manner, namely drying the silver plate surface at 60 ℃ for 30 minutes, drying the silver plate surface at 80 ℃ for 30 minutes, and drying the silver plate surface at 110 ℃ for 60 minutes to completely volatilize the solvent, wherein the film removed from the smooth substrate surface is a meta-aramid film, and the average thickness of the obtained meta-aramid film is 180 microns.
Example 10
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide to perform polymerization reaction at room temperature under the condition of nitrogen drying at the pressure of 0.03MPa and stirring, then adding a neutralizing agent of calcium hydroxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 400P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 8%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1) with a release agent after stirring, wherein the release agent uses fatty acid, vaseline, silicone oil and epoxypropane derivative, and the mass ratio of the fatty acid to the Vaseline to the silicone oil to the epoxypropane derivative is 1:1:1:1, the using amount of the release agent is 0.009 per mill of the mass concentration of the polymer solution; the polymer solution was uniformly coated on the surface roughness Ra with a wire bar coater having a diameter of 180 μm and a coating speed of 10 m/min: and (3) drying the surface of the smooth iron plate of 0.16 in a multistage manner, firstly drying at 50 ℃ for 10 minutes, then drying at 70 ℃ for 10 minutes, finally drying at 90 ℃ for 30 minutes to enable the solvent to be completely volatilized, and taking off the film from the surface of the smooth base material to obtain the meta-aramid film, wherein the average thickness of the obtained meta-aramid film is 15um.
Comparative example 1
Step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into N, N-dimethylformamide to perform polymerization reaction at room temperature under the condition of nitrogen drying at the pressure of 0.03MPa and stirring, then adding a neutralizing agent of calcium hydroxide to neutralize hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution with the viscosity reaching 400P and the specific viscosity at 50 ℃, wherein the mass concentration of the polymer is 8%;
step 2: preparing a meta-aramid film: the polymer solution prepared in the step 1 is uniformly coated on the surface roughness Ra by a wire rod coater with the diameter of 180um, wherein the coating speed is 10 m/min: 0.16, immersing the iron plate and the coated film into deionized water for 3 days, taking out, and completely drying at 130 ℃ until the film is completely dried to obtain the meta-aramid film.
TABLE 1 Performance index of meta-aramid films prepared in examples 1-10
From the data in table 1, it can be seen that: compared with the film prepared by the L-S method in comparative example 1, the meta-aramid film prepared by the method has the advantages of thinner and more uniform thickness, transparent appearance, compact structure and no bubbles or micropores in the film. The meta-aramid film prepared by the method maintains good molecular structural integrity after being formed, and has high tensile strength, elongation and modulus; the meta-aramid film prepared by the method has the compressive strength of 30-50kV/mm and the volume resistivity of 10 15 The composite material has the characteristics of high strength, high modulus, intrinsic flame retardance, high temperature resistance, low dielectric property, good flexibility, bending resistance, ageing resistance, long service life, low cost, simplicity in operation, mild process and the like, and can be used in the fields of flexible circuit boards, flexible display screens, wearable electronic equipment, insulating materials and the like.
In the invention, the viscosity and concentration of the meta-aramid polymer liquid, the film forming method, the temperature and time of multi-stage drying and the roughness of the smooth surface play a decisive role in the uniformity and performance of the meta-aramid film. The viscosity and the concentration of the meta-aramid polymer solution are too high, so that the fluidity in the film forming process is poor, and the uniformity of the film is poor; the meta-aramid polymer solution has too low viscosity and concentration to produce high thickness products. The film forming process must be compatible with the crystallization behavior, viscosity and solvent of the aramid solution itself. The temperature for drying is high and the time is long, so that the aramid film is easy to curl and deform and air bubbles or micropores are generated inside; the drying temperature is low, the time is short, the solvent is not completely volatilized, and a multistage drying process is required to thoroughly volatilize the solvent and ensure the flatness and compactness of the film. The roughness of the smooth surface directly influences the surface roughness of the meta-aramid film, the roughness Gao Jianwei aramid film has high roughness, precision devices such as a display screen and the like cannot be prepared, and the equipment cost is increased if the roughness is low. In summary, the invention provides a method for preparing the meta-aramid film with low cost, simple operation and mild process.
The meta-aramid film provided by the invention is transparent, compact in structure, free of bubbles or micropores in the film, uniform and controllable in thickness, good in mechanical property, and the prepared meta-aramid film has the thickness of 5-200 mu m, uniform and controllable in thickness, and maintains good molecular structural integrity after the aramid polymer solution is formed into the film, the compressive strength of the meta-aramid film prepared by the method can reach 30-50kV/mm, and the volume resistivity can reach 10 15 The composite material has the characteristics of high strength, high modulus, intrinsic flame retardance, high temperature resistance, low dielectric property, good flexibility, bending resistance, ageing resistance, long service life, low cost, simplicity in operation, mild process and the like, and can be used in the fields of flexible circuit boards, flexible display screens, wearable electronic equipment, insulating materials and the like.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (6)
1. The preparation method of the meta-aramid film with high dielectric strength is characterized by comprising the following steps of:
step 1: preparation of a polymerization solution: adding isophthaloyl dichloride and m-phenylenediamine into a solvent for polymerization reaction at room temperature under a nitrogen drying environment under the stirring condition, adding a neutralizing agent, neutralizing hydrogen chloride dissolved in the polymerization solution, and filtering to remove salt generated by the neutralization reaction to obtain a polymerization solution, wherein the mass concentration of the polymer is 5-40%;
step 2: preparing a meta-aramid film: uniformly mixing the polymerization solution prepared in the step 1 with a release agent after stirring, uniformly coating the mixture on the surface of a smooth substrate by using a film material film-making method, and drying the mixture in a multi-stage manner to completely volatilize the solvent, wherein the film removed from the surface of the smooth substrate is the meta-aramid film;
the nitrogen pressure in the step 1 is 0.03MPa; the solvent is one of N, N-dimethylformamide or N, N-dimethylacetamide;
the film material film forming method in the step 2 is one of a spin coater method, a dip-pull coating method, a wire rod coating method and a blade coating method;
the multistage drying process in the step 2 is that firstly, the drying is carried out for 10-30 minutes at 50-60 ℃, then the drying is carried out for 10-30 minutes at 70-80 ℃, and finally the drying is carried out for 30-60 minutes at 90-110 ℃;
the release agent in the step 2 is one or more of fatty acid, paraffin, glycerol, vaseline, silicone oil, polyethylene glycol, low molecular weight polyethylene, boron nitride, polytetrafluoroethylene wax and epoxypropane derivatives, and the use amount of the release agent is 0.001-0.01 per mill of the mass concentration of the polymer solution.
2. The method for preparing a meta-aramid film with high dielectric strength according to claim 1, wherein the neutralizing agent in the step 1 is one of calcium oxide, calcium hydroxide or ammonia gas.
3. The method for preparing a meta-aramid film with high dielectric strength according to claim 1, wherein the viscosity of the polymerization solution in the step 1 reaches 10-9000P at 50 ℃.
4. The method for preparing a meta-aramid film with high dielectric strength according to claim 1, wherein the smooth substrate in the step 2 is one of a metal plate, a toughened glass, a polyimide film, a polyester film, a polyether ether ketone film, a polytetrafluoroethylene film, and a polyethylene naphthalate film; the surface roughness of the smooth substrate surface in the step 2 is Ra:0.006-0.16.
5. The method for preparing the meta-position aramid film with high dielectric strength according to claim 1, wherein the average thickness of the intermediate-position aramid film in the step 2 is 5-200 micrometers, the dielectric strength is 30-50kV/mm, and the dielectric constant is 3-4 at a frequency of 5 GHz.
6. The high dielectric strength meta-aramid film prepared by the method of any one of claims 1 to 5.
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