Electromagnetic shielding film and preparation method thereof

Abstract

The invention discloses an electromagnetic shielding film and a preparation method thereof, and relates to the technical field of electromagnetic shielding, the electromagnetic shielding film is prepared from the following raw materials by weight: 70-80 parts of a functional polymer, 15-20 parts of a conductive filler, 1-3 parts of a coupling agent, 0.8-1 part of an antioxidant, 0.5-0.8 part of a slip agent, and 3-5 parts of 2-acrylamido-2-methylpropanesulfonic acid; the functional polymer is prepared from 3, 7-diamino-5-phenyl phenazine chloride and N-(4H-1, 2, 4-triazole-4-yl) diphenylamine-4, 4 '-dicarboxylic acid through a condensation polymerization reaction, and the functional polymer is a polymer with a molecular weight of 2,000-3,000 and a molecular weight of 2,000-3,000. The electromagnetic shielding film is sufficient in electromagnetic shielding performance, good in bending resistance and excellent in tensile strength, chemical stability and high and low temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding, and in particular to an electromagnetic shielding film and a preparation method thereof. Background Art

[0002] With the development of human electronic communication and electrical control, the mutual interference between electromagnetic signals has increasingly become a key issue threatening the normal operation of electronic equipment. The resulting electromagnetic radiation pollution has become the fourth largest pollution in people's lives after water pollution, air pollution, and noise pollution, and is known as the "invisible killer" of modern society. In the face of these challenges, efficient electromagnetic shielding materials are urgently needed.

[0003] Electromagnetic shielding film is a new type of electromagnetic shielding material that can block electromagnetic wave penetration, prevent electromagnetic radiation, protect electronic information from leakage and resist electromagnetic interference. In recent years, with the continuous development of electronic products, the market demand for electromagnetic shielding films has increased, and the performance requirements have also been continuously improved. However, the existing electromagnetic shielding films still have more or less technical defects such as limited electromagnetic shielding effectiveness, insufficient bending resistance, and tensile strength, chemical stability and high and low temperature resistance still need to be further improved.

[0004] In order to solve the above problems, the Chinese invention patent with the authorization announcement number CN102604194B discloses a polyethylene-based nanocomposite transparent electromagnetic shielding material, which is made by weighing low-density polyethylene and linear low-density polyethylene, conductive filler, silica, lubricant, antioxidant and coupling agent in proportion and mixing them at high speed in a mixer for 10 minutes, and then extruding and granulating them in a twin-screw extruder, with a screw speed of 100-200 rpm and a screw temperature of 170-230°C. After water cooling, the strips are cut into pellets to form a film masterbatch; after the masterbatch is dried at 80°C, it is added to the hopper of a film blowing machine, plasticized and extruded, blown and pulled, and blown into a film. The invention uses general PE plastic as the base material, and the prepared electromagnetic shielding film material has excellent comprehensive properties such as transparency, mechanical properties, and processing properties. However, its bending resistance, chemical stability, and high and low temperature resistance still need to be further improved.

[0005] It can be seen that it is particularly important to develop an electromagnetic shielding film with sufficient electromagnetic shielding performance, good bending resistance, excellent tensile strength, chemical stability and high and low temperature resistance and a preparation method thereof. Summary of the invention

[0006] The main purpose of the present invention is to provide an electromagnetic shielding film with sufficient electromagnetic shielding performance, good bending resistance, excellent tensile strength, chemical stability and high and low temperature resistance, and a preparation method thereof.

[0007] To achieve the above purpose, the present invention provides an electromagnetic shielding film, which is made of the following raw materials in parts by weight: 70-80 parts of functional polymer, 15-20 parts of conductive filler, 1-3 parts of coupling agent, 0.8-1 part of antioxidant, 0.5-0.8 part of slip agent, and 3-5 parts of 2-acrylamide-2-methylpropane sulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0008] Preferably, the preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst to a high boiling point solvent and mixing them evenly to obtain a mixture, then adding the mixture to a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 120-130°C under normal pressure for 3-5 hours, then heating to 240-260°C, and performing a condensation reaction at 300-500 Pa for 18-22 hours, then cooling to room temperature, adjusting to normal pressure, precipitating in water, washing the crude product with ethanol 3-6 times, and then placing it in a vacuum drying oven at 85-95°C to dry to constant weight to obtain a functional polymer.

[0009] Preferably, the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, catalyst and high boiling point solvent is 1:1:(0.8-1.2):(9-15).

[0010] Preferably, the catalyst is a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of (1-3):1:(0.8-1.2); the high boiling point solvent is dimethyl sulfoxide; and the inert gas is any one of nitrogen, helium, neon, and argon.

[0011] Preferably, the conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of (1-3):2; the model of the graphene is Morsh-P2; and the particle size of the conductive copper powder is 20-100 nm.

[0012] Preferably, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

[0013] Preferably, the antioxidant is at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0014] Preferably, the slip agent is Croda slip agent Crodamide™ 212, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0015] Another object of the present invention is to provide a method for preparing the electromagnetic shielding film, comprising the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, place it in a water bath and heat it to 55-65°C for reaction for 6-8 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol for 3-5 times respectively, then place it in an oven and dry it at 80-90°C to constant weight to obtain an electromagnetic shielding membrane.

[0016] Preferably, the extrusion temperature of the twin-screw extruder in step S1 is 235-255° C., and the screw speed is 180-280 rpm; Preferably, the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 113-123° C., the stretching rate is 120-90 mm / s, the heat setting temperature is 220-240° C., and the stretching ratio is 3:1.

[0017] Preferably, the water-soluble initiator is at least one of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride.

[0018] Preferably, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, water-soluble initiator and water in the aqueous solution is 1:(0.05-0.08):(3-5).

[0019] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The preparation method of the electromagnetic shielding film disclosed in the present invention has simple process, convenient operation and control, low dependence on equipment, high preparation efficiency and finished product qualification rate, is suitable for continuous large-scale production, and has high promotion and application value.

[0020] (2) The electromagnetic shielding film disclosed in the present invention is made of the following raw materials in parts by weight: 70-80 parts of functional polymer, 15-20 parts of conductive filler, 1-3 parts of coupling agent, 0.8-1 part of antioxidant, 0.5-0.8 part of slip agent, and 3-5 parts of 2-acrylamide-2-methylpropane sulfonic acid. Through the mutual coordination and joint action of the raw materials, the electromagnetic shielding film has sufficient electromagnetic shielding performance, good bending resistance, and excellent tensile strength, chemical stability and high and low temperature resistance.

[0021] (3) In the electromagnetic shielding film disclosed in the present invention, the functional polymer is prepared by polycondensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid. Phenazine cations, amides and triazole structures are simultaneously introduced into the polymer molecular structure. Under the effects of electronic effect, steric effect and conjugation effect, these structures make the prepared polymer have better bending resistance, tensile strength, chemical stability and high and low temperature resistance. By soaking in an aqueous solution of 2-acrylamide-2-methylpropane sulfonic acid, ion exchange reaction can occur on the 2-acrylamide-2-methylpropane sulfonic acid and the organic salt structure introduced by 3,7-diamino-5-phenylphenazine chloride, and free radical polymerization reaction can also occur on the unsaturated olefinic bonds on the 2-acrylamide-2-methylpropane sulfonic acid to form an interpenetrating network structure, further improving the above performance. At the same time, conductive fillers are effectively distributed in the interpenetrating network structure to form an effective bridge, and the conductive fillers are a mixture of graphene and conductive copper powder mixed in a mass ratio of (1-3):2. The electromagnetic shielding effect is improved by rationally selecting the composition. DETAILED DESCRIPTION

[0022] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations. Example 1

[0023] An electromagnetic shielding film is made of the following raw materials in parts by weight: 70 parts of functional polymer, 15 parts of conductive filler, 1 part of coupling agent, 0.8 parts of antioxidant, 0.5 parts of slip agent, and 3 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0024] The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material; then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 120°C for 3 hours at normal pressure, then heating to 240°C, performing a polycondensation reaction at 300 Pa for 18 hours, then cooling to room temperature, adjusting to normal pressure, precipitating in water, washing the crude product with ethanol, and finally obtaining a functional polymer. The product was dried three times, and then placed in a vacuum drying oven at 85°C to a constant weight to obtain a functional polymer; the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, the catalyst, and the high boiling point solvent was 1:1:0.8:9; the catalyst was a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of 1:1:0.8; the high boiling point solvent was dimethyl sulfoxide; the inert gas was nitrogen; the M of the functional polymer was measured by GPC test. n =15728g / mol,M W / M n =1.319; calculated by elemental analysis and weight change, the molar ratio of the structural units introduced by 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid in the functional polymer is the same as the theoretical value.

[0025] The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of 1:2; the model of the graphene is Morsh-P2; the particle size of the conductive copper powder is 20nm; the coupling agent is silane coupling agent KH550; the antioxidant is antioxidant 1010; the lubricant is Croda's Crodamide™ 212, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0026] A method for preparing the electromagnetic shielding film comprises the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, and then place it in a water bath and heat it to 55°C for reaction for 6 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol three times respectively, then place it in an oven and dry it at 80°C to constant weight to obtain an electromagnetic shielding membrane.

[0027] The extrusion temperature of the twin-screw extruder in step S1 is 235° C., and the screw speed is 180 rpm; the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 113° C., the stretching rate is 120 mm / s, the heat setting temperature is 220° C., and the stretching ratio is 3:1; the water-soluble initiator is azobisisobutylamidine hydrochloride; and the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, the water-soluble initiator, and water in the aqueous solution is 1:0.05:3. Example 2

[0028] An electromagnetic shielding film is made of the following raw materials in parts by weight: 73 parts of functional polymer, 16 parts of conductive filler, 1.5 parts of coupling agent, 0.9 parts of antioxidant, 0.6 parts of slip agent, and 3.5 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0029] The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material; then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 123°C for 3.5 hours at normal pressure, then heating to 245°C, performing a polycondensation reaction at 350 Pa for 19 hours, then cooling to room temperature, adjusting to normal pressure, and precipitating in water. The crude product is washed with ethanol for 4 times, and then placed in a vacuum drying oven at 87° C. to dry to constant weight to obtain a functional polymer; the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, catalyst, and high boiling point solvent is 1:1:0.9:11; the catalyst is a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of 1.5:1:0.9; the high boiling point solvent is dimethyl sulfoxide; and the inert gas is helium.

[0030] The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of 1.5:2; the model of the graphene is Morsh-P2; the particle size of the conductive copper powder is 40nm; the coupling agent is silane coupling agent KH560; the antioxidant is antioxidant 168; the lubricant is Croda's Crodamide™ 212, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0031] A method for preparing the electromagnetic shielding film comprises the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, and after passing nitrogen at room temperature for 20 minutes, place it in a water bath and heat it to 57°C to react for 6.5 hours; after the reaction is completed, take out the primary membrane, wash it with deionized water and methanol four times respectively, then place it in an oven, and dry it at 83°C to constant weight to obtain an electromagnetic shielding membrane.

[0032] The extrusion temperature of the twin-screw extruder in step S1 is 240° C., and the screw speed is 200 rpm; the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 115° C., the stretching rate is 110 mm / s, the heat setting temperature is 225° C., and the stretching ratio is 3:1; the water-soluble initiator is azobisisobutylimidazoline hydrochloride; and the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, the water-soluble initiator, and water in the aqueous solution is 1:0.06:3.5. Example 3

[0033] An electromagnetic shielding film is made of the following raw materials in parts by weight: 75 parts of functional polymer, 17 parts of conductive filler, 2 parts of coupling agent, 0.9 parts of antioxidant, 0.65 parts of slip agent, and 4 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0034] The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material; then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 125°C for 4 hours at normal pressure, then heating to 250°C, performing a polycondensation reaction at 400 Pa for 20 hours, then cooling to room temperature, adjusting to normal pressure, and evaporating in water. The crude product is precipitated out, washed with ethanol for 5 times, and then placed in a vacuum drying oven at 90° C. to dry to constant weight to obtain a functional polymer; the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, catalyst, and high boiling point solvent is 1:1:1:12; the catalyst is a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of 2:1:1; the high boiling point solvent is dimethyl sulfoxide; and the inert gas is neon.

[0035] The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of 2:2; the model of the graphene is Morsh-P2; the particle size of the conductive copper powder is 60nm; the coupling agent is silane coupling agent KH570; the antioxidant is antioxidant 1076; the lubricant is Croda's Crodamide™ 212, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0036] A method for preparing the electromagnetic shielding film comprises the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, and then place it in a water bath and heat it to 60°C for reaction for 7 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol four times respectively, then place it in an oven and dry it at 85°C to constant weight to obtain an electromagnetic shielding membrane.

[0037] The extrusion temperature of the twin-screw extruder in step S1 is 245° C., and the screw speed is 230 rpm; the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 118° C., the stretching rate is 105 mm / s, the heat setting temperature is 230° C., and the stretching ratio is 3:1; the water-soluble initiator is azobisisobutylamidine hydrochloride; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, water-soluble initiator, and water in the aqueous solution is 1:0.065:4. Example 4

[0038] An electromagnetic shielding film is made of the following raw materials in parts by weight: 78 parts of functional polymer, 19 parts of conductive filler, 2.5 parts of coupling agent, 0.95 parts of antioxidant, 0.75 parts of slip agent, and 4.5 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0039] The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material; then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 128°C for 4.5 hours at normal pressure, then heating to 255°C, performing a polycondensation reaction at 450 Pa for 21 hours, then cooling to room temperature, adjusting to normal pressure, and precipitating in water. The crude product is washed with ethanol for 6 times, and then placed in a vacuum drying oven at 93° C. to dry to constant weight to obtain a functional polymer; the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, the catalyst, and the high boiling point solvent is 1:1:1.1:14; the catalyst is a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of 2.5:1:1.1; the high boiling point solvent is dimethyl sulfoxide; and the inert gas is argon.

[0040] The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of 2.5:2; the model of the graphene is Morsh-P2; the particle size of the conductive copper powder is 90nm; the coupling agent is a mixture of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570 in a mass ratio of 1:2:3; the antioxidant is a mixture of antioxidant 1010, antioxidant 168, and antioxidant 1076 in a mass ratio of 2:1:1; the lubricant is Croda's Crodamide™212 lubricant, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0041] A method for preparing the electromagnetic shielding film comprises the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, and then place it in a water bath and heat it to 63°C for reaction for 7.5 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol for 5 times respectively, then place it in an oven and dry it at 88°C to constant weight to obtain an electromagnetic shielding membrane.

[0042] The extrusion temperature of the twin-screw extruder in step S1 is 250° C., and the screw speed is 270 rpm; the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 121° C., the stretching rate is 100 mm / s, the heat setting temperature is 235° C., and the stretching ratio is 3:1; the water-soluble initiator is a mixture of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride in a mass ratio of 3:5; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, water-soluble initiator, and water in the aqueous solution is 1:0.075:4.5. Example 5

[0043] An electromagnetic shielding film is made of the following raw materials in parts by weight: 80 parts of functional polymer, 20 parts of conductive filler, 3 parts of coupling agent, 1 part of antioxidant, 0.8 parts of slip agent, and 5 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is made by condensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0044] The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material; then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 130°C for 5 hours under normal pressure, then heating to 260°C, performing a polycondensation reaction at 500 Pa for 22 hours, then cooling to room temperature, adjusting to normal pressure, and precipitating in water. The crude product is washed with ethanol for 6 times, and then placed in a vacuum drying oven at 95° C. to dry to constant weight to obtain a functional polymer; the molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, the catalyst, and the high boiling point solvent is 1:1:1.2:15; the catalyst is a mixture of thiophosphonate, phosphorous acid, and thiophosphoramide in a mass ratio of 3:1:1.2; the high boiling point solvent is dimethyl sulfoxide; and the inert gas is argon.

[0045] The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of 3:2; the model of the graphene is Morsh-P2; the particle size of the conductive copper powder is 100nm; the coupling agent is silane coupling agent KH550; the antioxidant is antioxidant 1010; the lubricant is Croda's Crodamide™ 212, provided by Shanghai Kaiyin Chemical Co., Ltd.

[0046] A method for preparing the electromagnetic shielding film comprises the following steps: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, and then place it in a water bath and heat it to 65°C for reaction for 8 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol for 5 times respectively, then place it in an oven and dry it at 90°C to constant weight to obtain an electromagnetic shielding membrane.

[0047] The extrusion temperature of the twin-screw extruder in step S1 is 255° C., and the screw speed is 280 rpm; the biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 123° C., the stretching rate is 90 mm / s, the heat setting temperature is 240° C., and the stretching ratio is 3:1; the water-soluble initiator is azobisisobutylamidine hydrochloride; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, water-soluble initiator, and water in the aqueous solution is 1:0.08:5.

[0048] Comparative Example 1 An electromagnetic shielding film and a preparation method thereof are basically the same as those in Example 1, except that an equal amount of ethylenediamine is used instead of 3,7-diamino-5-phenylphenazine chloride.

[0049] Comparative Example 2 An electromagnetic shielding film and a preparation method thereof are basically the same as those in Example 1, except that an equal amount of terephthalic acid is used instead of N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

[0050] Comparative Example 3 An electromagnetic shielding film and a preparation method thereof, which are substantially the same as those of Example 1, except that 2-acrylamide-2-methylpropanesulfonic acid is not added.

[0051] In order to further illustrate the beneficial technical effects of the electromagnetic shielding films involved in each embodiment of the present invention, relevant performance tests were performed on the electromagnetic shielding films involved in Examples 1-5 and Comparative Examples 1-2. During the test, the film thickness of each electromagnetic shielding film was controlled to be 40 μm. The test results are shown in Table 1. The test method is as follows: (1) Electromagnetic shielding effectiveness: Tested in accordance with GB / T30142-2013 standard; (2) Tensile strength: Tested in accordance with GB / T1040.3-2006 standard, specimen type 1B; test speed 50 mm / min; (3) Dynamic bending resistance: It is evaluated by a U-shaped dynamic bending test. The film is repeatedly folded and stretched with a fixed folding radius of 0.5 mm, and the number of folding times at which creases appear is observed. If no creases appear after 250,000 bends, the bending resistance passes, otherwise it fails.

[0052] (4) Chemical resistance: The electromagnetic shielding film is attached to the mold for testing and is in direct contact with the solvent. The solvents selected are 30% sodium hydroxide solution, acetone, isopropyl alcohol and dimethyl sulfoxide. The test time is 24 hours, and the surface is observed for changes. If there is no change on the film surface under contact with various test solvents, the chemical resistance is qualified, otherwise it fails.

[0053] (5) High and low temperature resistance: high temperature is 80℃, 12h; low temperature is -55℃, 12h. After ten cycles, the electromagnetic shielding test is carried out, and the electromagnetic shielding effectiveness retention rate is counted and calculated. The larger the value, the better the high and low temperature resistance.

[0054] As can be seen from Table 1, the electromagnetic shielding film disclosed in the embodiment of the present invention has better electromagnetic shielding performance, chemical stability, high and low temperature resistance, bending resistance and mechanical properties than the comparative example product. The addition of 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and 2-acrylamido-2-methylpropanesulfonic acid is beneficial to improving the above-mentioned properties.

[0055] Table 1 project Electromagnetic shielding effectiveness Tensile Strength Dynamic bending resistance Chemical stability High and low temperature resistance unit dB MPa — — % Example 1 82 256 pass qualified 98.7 Example 2 84 260 pass qualified 99.2 Example 3 87 267 pass qualified 99.5 Example 4 88 270 pass qualified 99.6 Example 5 92 275 pass qualified 99.8 Comparative Example 1 79 240 Not passed Not passed 94.5 Comparative Example 2 81 245 Not passed Not passed 95.1 Comparative Example 3 78 232 Not passed Not passed 94.0 The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. An electromagnetic shielding film, characterized in that: The invention comprises the following raw materials in parts by weight: 70-80 parts of functional polymer, 15-20 parts of conductive filler, 1-3 parts of coupling agent, 0.8-1 parts of antioxidant, 0.5-0.8 parts of slip agent and 3-5 parts of 2-acrylamide-2-methylpropanesulfonic acid; the functional polymer is prepared by polycondensation reaction of 3,7-diamino-5-phenylphenazine chloride and N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid.

2. The electromagnetic shielding film according to claim 1, characterized in that The preparation method of the functional polymer comprises the following steps: adding 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazole-4-yl)diphenylamine-4,4'-dicarboxylic acid and a catalyst into a high boiling point solvent and mixing them evenly to obtain a mixed material, then adding the mixed material into a reaction kettle, replacing the air in the kettle with an inert gas, reacting at 120-130° C. under normal pressure for 3-5 hours, then heating to 240-260° C., carrying out a polycondensation reaction at 300-500 Pa for 18-22 hours, then cooling to room temperature, adjusting to normal pressure, precipitating in water, washing the crude product with ethanol for 3-6 times, and then drying it in a vacuum drying oven at 85-95° C. to constant weight to obtain the functional polymer.

3. The electromagnetic shielding film according to claim 2, characterized in that The molar ratio of the 3,7-diamino-5-phenylphenazine chloride, N-(4H-1,2,4-triazol-4-yl)diphenylamine-4,4'-dicarboxylic acid, catalyst and high boiling point solvent is 1:1:(0.8-1.2):(9-15).

4. The electromagnetic shielding film according to claim 2, characterized in that The catalyst is a mixture of thiophosphonate, phosphorous acid and thiophosphoramide in a mass ratio of (1-3):1:(0.8-1.2); the high boiling point solvent is dimethyl sulfoxide; and the inert gas is any one of nitrogen, helium, neon and argon.

5. The electromagnetic shielding film according to claim 1, characterized in that The conductive filler is a mixture of graphene and conductive copper powder in a mass ratio of (1-3):2; the model of the graphene is Morsh-P2; and the particle size of the conductive copper powder is 20-100 nm.

6. The electromagnetic shielding film according to claim 1, characterized in that The coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570; the antioxidant is at least one of antioxidant 1010, antioxidant 168, and antioxidant 1076; and the slip agent is Croda slip agent Crodamide™ 212.

7. A method for preparing an electromagnetic shielding film according to any one of claims 1 to 6, characterized in that: The steps include: Step S1: after the functional polymer, conductive filler, coupling agent, antioxidant and lubricant are uniformly mixed according to weight parts, a composite material is obtained, and the composite material is sequentially extruded, cast and cast through a twin-screw extruder to form a sheet; and then stretched through a biaxial stretching process to form a primary film; Step S2: Soak the primary membrane in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid and a water-soluble initiator, pass nitrogen at room temperature for 20 minutes, place it in a water bath and heat it to 55-65°C for reaction for 6-8 hours; after the reaction is completed, take out the primary membrane and wash it with deionized water and methanol for 3-5 times respectively, then place it in an oven and dry it at 80-90°C to constant weight to obtain an electromagnetic shielding membrane.

8. The method for preparing the electromagnetic shielding film according to claim 7, characterized in that: The extrusion temperature of the twin-screw extruder in step S1 is 235-255° C., and the screw speed is 180-280 rpm.

9. The method for preparing an electromagnetic shielding film according to claim 7, characterized in that: The biaxial stretching process in step S1 is specifically as follows: the stretching temperature is 113-123° C., the stretching rate is 120-90 mm / s, the heat setting temperature is 220-240° C., and the stretching ratio is 3:

1.

10. The method for preparing an electromagnetic shielding film according to claim 7, characterized in that: The water-soluble initiator is at least one of azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride; the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, water-soluble initiator and water in the aqueous solution is 1:(0.05-0.08):(3-5).