Waterproof and dustproof film for electronic product and preparation method of waterproof and dustproof film

Abstract

The invention relates to the technical field of polytetrafluoroethylene plastic films, and particularly discloses a waterproof and dustproof film for electronic products and a preparation method thereof.Polyether-ether-ketone resin is adopted as a matrix of filler master batches, compatibility and dispersity of silicon dioxide particles are enhanced, then distributed directional stretching and hot-pressing compounding are conducted, and an ePTFE film of a gradient micropore structure is formed; the pore size of the surface layer of the membrane material is minimum, liquid water cannot permeate, the pore size of the middle layer is increased, small molecular gas such as water vapor is allowed to pass through, the pore size of the bottom layer is maximum, the water vapor permeability is remarkably improved, finally, the surface is impregnated and crosslinked to form a hydrophobic coating, and the hydrophobicity, friction resistance and aging resistance of the surface of the membrane material are further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polytetrafluoroethylene plastic film, in particular to a waterproof and dustproof film for electronic products and a preparation method thereof. BACKGROUND

[0002] In today's rapid development of science and technology, portable electronic products such as mobile phones, electronic watches, smart glasses, and wireless earphones have deeply integrated into people's daily life. However, these portable electronic products need to be frequently exposed to sweat, rainwater, dust, and other pollutants due to people's carrying and using, which can easily cause water and dust ingress, thereby affecting the performance of the electronic products and even causing property loss to people. Therefore, the protection of electronic products is becoming increasingly important.

[0003] Traditional protection methods such as rubber sealing or glue sealing have the purpose of waterproofing and dustproofing to some extent, but such structural sealing not only affects the appearance of electronic products, but also brings inconvenience during disassembly and maintenance, and may also cause heat accumulation inside the electronic products, affecting the normal operation of the equipment. The waterproof and dustproof film has become a replacement for structural sealing due to its advantages of being light, thin, transparent, and suitable for most complex shapes. Currently, waterproof and dustproof films are mostly dense films that achieve waterproofing and dustproofing through the hydrophobicity of the film surface. However, such dense structure also blocks the passage of water vapor and other gases, leading to an imbalance between the internal and external air pressure of the electronic product after long-term use, resulting in bulging or edge opening problems. The hydrophobic coating of the film can also be affected by light aging, physical factors such as finger rubbing, and other factors, causing the coating to fall off and other problems. This seriously affects people's experience of using electronic products. SUMMARY

[0004] The purpose of the present application is to provide a waterproof and dustproof film for electronic products and a preparation method thereof, which has good waterproofing and dustproofing performance, good air permeability, and good weather resistance, solving the problem of poor air permeability and weather resistance of waterproof and dustproof films affecting the performance of electronic products.

[0005] To solve the above technical problems, the present application provides the following technical solutions: A preparation method of a waterproof and dustproof film for electronic products, specifically comprising: Step 1: mixing polyether ether ketone resin and functional additives, then extruding and granulating to obtain filler masterbatch; Step 2: mixing polytetrafluoroethylene resin, filler masterbatch, and lubricant white oil, then densifying and extruding and granulating to obtain modified PTFE resin particles; Step 3: extruding the modified PTFE resin particles to form a blank, dividing the blank into three parts, and then obtaining a gradient microporous structure ePTFE film after stretching, stacking, and hot pressing; Step 4: Gradient microporous structure ePTFE film is immersed in a solution of fluorinated polydimethylsiloxane in ethanol and a solution of methyltrimethoxysilane in water after plasma cleaning, dried to obtain a waterproof and dustproof film for electronic products.

[0006] As a limitation of the present application, the functional additives include coupling agent modified nano-silica, maleic anhydride grafted polyether ether ketone, light stabilizer 770 and antioxidant 1076; the filler masterbatch includes 80-100 parts of polyether ether ketone resin, 15-20 parts of coupling agent modified nano-silica, 5-10 parts of maleic anhydride grafted polyether ether ketone, 1.5-2.5 parts of light stabilizer 770 and 0.3-1.0 parts of antioxidant 1076 by mass; the process parameters during extrusion granulation include: die temperature: 350-360℃, screw rotation speed: 150-200rpm.

[0007] The polyether ether ketone is used as the masterbatch matrix, and fillers such as coupling agent modified nano-silica are added to form a functional masterbatch. The polyether ether ketone in the masterbatch serves as the matrix and has a rigid structure (ether bond -O-, ketone group -CO-), excellent high-temperature resistance, and good acid and alkali resistance, which is beneficial to improve the high-temperature resistance and chemical stability of the finished film material. The maleic anhydride grafted polyether ether ketone in the masterbatch acts as a compatibilizer. Its maleic anhydride groups partially hydrolyze to carboxyl groups (-COOH) under high temperature and shear, and react with the hydroxyl groups (-OH) on the surface of PTFE generated by processing or plasma irradiation to form stable covalent bonds. This not only reduces the phase separation tendency of PEEK and PTFE, but also acts as a bridge to enhance the compatibility of PEEK and PTFE, reducing the problem of delamination or fracture of the film material due to interface defects, and improving the stability of the finished film material. The light stabilizer 770 and antioxidant 1076 in the masterbatch synergistically capture and terminate the free radicals generated by the polymer molecular chain during the aging process, inhibit the chain reaction of the degradation process, delay the aging of the polymer, and improve the weather resistance of the finished film material.

[0008] The nano-silica is modified with a silane coupling agent to disperse uniformly in the resin. The uniformly dispersed nano-silica acts as a heterogeneous nucleation point, and the hydroxyl groups (-OH) on its surface form hydrogen bonds with the polar groups of the polymer (C-F bond edge δ + ether bond -O- of PEEK), anchoring the polymer on the surface of the silica and inducing the directional arrangement of the polymer molecular chain. The polymer molecular chains aggregate in local areas, forming high-density microzones. During stretching or heat treatment, the high-density microzones break due to stress concentration, forming a microporous structure and giving the finished film material air permeability.

[0009] As a limitation of the present application, the preparation method of the coupling agent modified nano-silica is: The nano-silicon dioxide is added into a mixed solution of ethanol and deionized water, ultrasonic dispersion is carried out for 10-20 min, then the silane coupling agent KH-550 is added, reaction is carried out at 80-90℃ for 1-2 h, after the reaction is completed, cooling is carried out, centrifugal separation is carried out, washing is carried out with ethanol and deionized water, and drying is carried out at 70-80℃ for 2-3 h, so that the coupling agent modified nano-silicon dioxide is obtained.

[0010] The mass ratio of the nano-silicon dioxide and the silane coupling agent KH-550 is (95-100):(3-5).

[0011] As the limitation of the application, the mass ratio of the polytetrafluoroethylene resin and the filler master batch is (6-7):(3-4); the mass of the lubricant white oil accounts for 0.2%-0.5% of the total mass of the modified PTFE resin particles; during the banburying, two stages are divided, the process parameters of the first stage include: rotation speed: 180-200 rpm, banburying temperature: 330-340℃, banburying time: 3-5 min; the process parameters of the second stage include: rotation speed: 80-100 rpm, banburying temperature: 350-360℃, banburying time: 8-10 min; the process parameters during the extrusion granulation include: die temperature: 360-370℃, screw rotation speed: 100-120 rpm.

[0012] The polytetrafluoroethylene resin is used as the main film forming base material of the waterproof and dustproof film, and the surface energy and chemical inertness thereof are the basis of the waterproof and dustproof functions of the finished film material; the lubricant white oil is added to reduce the friction force between the PTFE molecular chains, reduce the PTFE melt viscosity, improve the processing performance of the PTFE, make the PTFE melt more easily flow during processing, reduce the defects such as bubbles and wrinkles of the finished film material caused by high viscosity, and ensure the integrity of the film material.

[0013] As the limitation of the application, the preparation method of the gradient microporous structure ePTFE film is as follows: The modified PTFE resin particles are added into an extruder, the die temperature is set to 360-370℃, the die gap is 0.5-1 mm, the water cooling roller temperature is 20-30℃, the extrusion blank is formed, the blank is divided into three parts, and stretching is carried out on the three parts respectively, the stretching rate is controlled to be 8-10 m / min, the gradient surface layer, the gradient middle layer and the gradient bottom layer are formed, after the stretching is completed, heat pressing is carried out, the gradient surface layer, the gradient middle layer and the gradient bottom layer are stacked in sequence, heat pressing is carried out at 130-140℃ and 0.4-0.5 MPa for 5-8 min, and the gradient microporous structure ePTFE film is obtained.

[0014] As the limitation of the present application, when forming the gradient surface layer, only longitudinal stretching is performed, the stretching temperature is 105-110℃, and the stretching ratio is 2-3 times; when forming the gradient intermediate layer, two-way synchronous stretching is performed, the stretching temperature is 115-120℃, the longitudinal stretching ratio is 4-5 times, and the transverse stretching ratio is 3-4 times; when forming the gradient bottom layer, two-way synchronous stretching is performed, the stretching temperature is 125℃, the longitudinal stretching ratio is 5-6 times, and the transverse stretching ratio is 5-6 times.

[0015] The gradient microporous structure ePTFE membrane is composed of a gradient surface layer, a gradient intermediate layer and a gradient bottom layer, the gradient surface layer is only stretched along the longitudinal direction, the stretching temperature is low, the PTFE molecular chain is highly oriented along the stretching direction, the intermolecular pores are compressed to form a dense amorphous region, in the stretching process, the surface layer PTFE generates transverse shrinkage force due to longitudinal orientation, and micro-cracks are induced at the interface between the amorphous region and the crystalline region, the micro-cracks form a microporous structure (pore size is about 0.1 μm) as a microporous site, which is much smaller than the critical pore size (about 0.2 μm) that can be overcome by the surface tension of liquid water, and liquid water cannot penetrate, so the surface layer can block liquid water.

[0016] The gradient intermediate layer is located between the gradient surface layer and the gradient bottom layer, and is subjected to synchronous stretching force in the longitudinal and transverse directions, the PTFE molecular chain is oriented in two directions, but the longitudinal orientation degree is higher than the transverse orientation degree (the longitudinal stretching ratio is higher than the transverse stretching ratio), an elliptical micropore (pore size is about 0.4 μm) is formed, which allows small molecule gas such as water vapor to pass through, and at the same time, the stress gradient dispersion through the long axis-short axis of the elliptical hole buffers the stress difference between the surface layer and the bottom layer, avoiding the delamination or rupture of the membrane material.

[0017] The gradient bottom layer is subjected to synchronous stretching force in the longitudinal and transverse directions, the PTFE molecular chain is uniformly oriented in two directions (the longitudinal stretching ratio is equal to the transverse stretching ratio), a circular micropore (pore size is about 0.6 μm) is formed, which significantly improves the water vapor permeability, at the same time, the equiaxed two-way stretching avoids the pore size segregation problem caused by one-way stretching, the PTFE molecular chain is arranged more uniformly, and the local stress concentration caused by uneven pore size is reduced.

[0018] As the limitation of the present application, when the plasma cleaning is performed, argon and oxygen are introduced; the process parameters of the plasma cleaning include: argon flow rate: 70-80 sccm, oxygen flow rate: 20-30 sccm, plasma power: 80-100 W, and cleaning time: 2-5 min.

[0019] As the limitation of the present application, the fluorinated polydimethylsiloxane ethanol solution contains 0.3-0.5 wt% fluorinated polydimethylsiloxane; the methyltrimethoxysilane aqueous solution contains 0.5-1 wt% methyltrimethoxysilane.

[0020] As the limitation of the present application, when the fluorinated polydimethylsiloxane ethanol solution is immersed, the ultrasonic treatment accelerates the immersion, the ultrasonic treatment time is 5-8 min, and after immersion, vacuum drying is carried out at 80-90 DEG C for 1.5-2 h; when the methyltrimethoxysilane aqueous solution is immersed, the ultrasonic treatment accelerates the immersion, the ultrasonic treatment time is 10-15 min, and after immersion, drying is carried out at 60-70 DEG C for 15-30 min.

[0021] The film material is cleaned by adopting the way of plasma cleaning, high-energy particles (Ar + , O + ) in the plasma bombard the film material surface, remove surface impurities, oxidize the film material surface, introduce polar groups (-OH, -COOH), and improve the surface roughness to provide sites for the grafting of fluorinated polydimethylsiloxane.

[0022] The fluorinated polydimethylsiloxane fluorinated alkyl group (-CF2-) has strong hydrophobicity and good compatibility with the C-F bond on the film material surface, forming a uniform hydrophobic coating on the surface; after the silanol group (-Si-OH) of the fluorinated polydimethylsiloxane is crosslinked with the methyltrimethoxysilane, a three-dimensional crosslinked network is formed, further improving the hydrophobicity, abrasion resistance and anti-aging ability of the film material surface.

[0023] A waterproof and dustproof film for electronic products is prepared by the preparation method in any one of the above.

[0024] Compared with the prior art, the present application has the following beneficial effects: The present application adopts polyether ether ketone resin as the matrix of the filler master batch, the polyether ether ketone molecular chain contains ether bonds (-O-) and ketone groups (-CO-), and has moderate polarity; through hydrogen bonding (hydrogen bonds are formed between the ether bonds or ketone groups of the polyether ether ketone and the hydroxyl groups on the surface of the modified nano-silicon dioxide) and dipole-dipole interaction (polar groups such as the ether bonds and ketone groups of the polyether ether ketone interact with the polar surface of the modified nano-silicon dioxide), dipole attraction is generated to enhance the compatibility and dispersibility of the silicon dioxide particles, so that the modified nano-silicon dioxide can be uniformly dispersed in the polyether ether ketone matrix, avoiding the problem that the traditional PTFE matrix has weak polarity, leading to uneven dispersion of the filler; the improvement of compatibility reduces phase separation in the blending process, reducing defects such as delamination and cracking of the film material; the melt viscosity of the polyether ether ketone is lower than that of PTFE, and after the maleic anhydride grafted polyether ether ketone is added, the melt viscosity of the mixture is further reduced, improving the processing performance; the ether bonds and ketone groups of the polyether ether ketone have strong UV resistance, combined with the ultraviolet shielding effect of the nano-silicon dioxide and the ultraviolet absorption effect of the light stabilizer 1076, the weather resistance and ultraviolet resistance of the film material are further improved.

[0025] The present application adopts the way of distributed directional stretching and hot pressing compounding to prepare the ePTFE film with gradient microporous structure, the pore size of the surface layer of the film material is the smallest, far smaller than the critical pore size that can be overcome by the surface tension of liquid water, liquid water cannot penetrate, the pore size of the middle layer becomes larger, allowing small molecule gases such as water vapor to pass through, the pore size of the bottom layer is the largest, small molecule gases such as water vapor can quickly pass through, significantly improving the water vapor permeability; on this basis, a three-dimensionally crosslinked hydrophobic coating is further formed on the surface to increase the contact angle of the film material, further improving the hydrophobicity, abrasion resistance and anti-aging ability of the surface of the film material. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments, the terms used in the embodiments are for describing the specific specific embodiments, not for limiting the protection scope of the present application, the amount used in the embodiments is a laboratory small test, which can be enlarged in proportion. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0027] Polyether ether ketone resin (PEEK resin, molecular weight Mn: 2-10W), polytetrafluoroethylene resin (PTFE resin, molecular weight Mn: 100-500W), nano-silicon dioxide (particle size: 50nm, specific surface area: 500m 2 / g), maleic anhydride grafted polyether ether ketone (grafting rate: 5%, density: 1.35g / cm 3 ), fluorinated polydimethylsiloxane (molecular weight Mn: 2000-5000).

[0028] The preparation method of the coupling agent modified nano-silicon dioxide is as follows: 100g of nano-silicon dioxide is added to a mixture of 500mL of ethanol and 100mL of deionized water, ultrasonic dispersion for 10min, then 3g of silane coupling agent KH-550 is added, and the reaction is carried out at 80℃ for 2h, after the reaction is completed, cooling, centrifugal separation, washing with ethanol and deionized water, drying at 80℃ for 2h, to obtain the coupling agent modified nano-silicon dioxide.

[0029] The preparation method of the fluorinated polydimethylsiloxane ethanol solution is as follows: 3.5g of fluorinated polydimethylsiloxane is added to 999.65g of ethanol, 300rpm magnetic stirring for 10min for preliminary dispersion, then ultrasonic dispersion for 15min, after ultrasonic dispersion is completed, standing and defoaming, to obtain the fluorinated polydimethylsiloxane ethanol solution.

[0030] The preparation method of the methyltrimethoxysilane aqueous solution is as follows: 1g methyltrimethoxysilane was added into 9g ethanol, and mixed for 2min at 300rpm to form a mixture, 90g deionized water was slowly added into the mixture while stirring, and ultrasonic treatment was performed for 15min to obtain a methyltrimethoxysilane aqueous solution.

[0031] Example 1: A method for preparing a waterproof and dustproof film for electronic products, specifically: Step 1: 100g PEEK resin, 15g coupling agent modified nano-silica, 5g maleic anhydride grafted polyether ether ketone, 1.5g light stabilizer 770 and 0.3g antioxidant 1076 were mixed and then added into a twin-screw extruder for extrusion and granulation, the die temperature was set to 350℃, and the screw rotation speed was 200rpm to obtain a filler master batch; Step 2: 600g PTFE resin, 400g filler master batch and 2g lubricant white oil were added into an internal mixer, mixed and internally mixed at 200rpm and 340℃ for 5min, then the rotation speed was adjusted to 100rpm and the temperature was adjusted to 360℃, and the internal mixing was continued for 10min, then the internal mixing was completed and transferred to a twin-screw extruder for extrusion and granulation, the die temperature was 360℃ and the screw rotation speed was 100rpm to obtain modified PTFE resin particles; Step 3: 500g modified PTFE resin particles were added into an extruder, the die temperature was set to 370℃, the die gap was 0.5mm, and the water-cooled roller temperature was 20℃, and a 50μm thick die blank was extruded, the die blank was divided into 3 parts and stretched respectively, the stretching rate was controlled at 8m / min, the first part was only stretched longitudinally, the stretching temperature was 110℃, and the stretching ratio was 2.5 times to obtain a gradient surface layer, the second part was synchronously stretched in two directions, the stretching temperature was 115℃, the longitudinal stretching ratio was 4.5 times, and the transverse stretching ratio was 3.5 times to obtain a gradient middle layer, the third part was synchronously stretched in two directions, the stretching temperature was 125℃, the longitudinal stretching ratio was 5.5 times, and the transverse stretching ratio was 5.5 times to obtain a gradient bottom layer, after stretching, heat pressing was performed for composite, the gradient surface layer, the gradient middle layer and the gradient bottom layer were stacked in sequence, and heat pressing was performed at 135℃ and 0.5MPa for 5min to obtain a gradient microporous structure ePTFE film; Step 4: The gradient microporous structure ePTFE film was plasma cleaned, the cleaning gas was argon and oxygen, the argon flow rate was 70sccm, the oxygen flow rate was 30sccm, the plasma power was 80W, and the cleaning time was 2.5min, after cleaning, the film was immersed in a fluorinated polydimethylsiloxane ethanol solution, ultrasonic treatment was performed for 5min, after immersion, the film was vacuum dried at 80℃ for 2h, then immersed in a methyltrimethoxysilane aqueous solution, ultrasonic treatment was performed for 10min, and the film was oven dried at 60℃ for 15min to obtain a waterproof and dustproof film for electronic products.

[0032] Example 2: A method for preparing a waterproof and dustproof film for electronic products, specifically: Step 1: 90 g of PEEK resin, 20 g of coupling agent modified nano-silica, 10 g of maleic anhydride grafted polyether ether ketone, 2.0 g of light stabilizer 770 and 0.5 g of antioxidant 1076 were mixed and then added to a twin-screw extruder for extrusion granulation. The die temperature was set to 350℃, and the screw speed was 200 rpm. The filler masterbatch was obtained. Step 2: 600 g of PTFE resin, 400 g of filler masterbatch and 4 g of lubricant white oil were added to an internal mixer and mixed at 200 rpm and 340℃ for 5 min. Then the speed was adjusted to 100 rpm and the temperature was adjusted to 360℃. The mixing was continued for another 10 min. After mixing, the mixture was transferred to a twin-screw extruder for extrusion granulation. The die temperature was 360℃, and the screw speed was 100 rpm. The modified PTFE resin particles were obtained. Step 3: 500 g of modified PTFE resin particles were added to an extruder. The die temperature was set to 370℃, the die gap was 0.5 mm, and the water-cooled roller temperature was 20℃. The extruder was used to produce a 50 μm thick die. The die was divided into three parts and stretched separately. The stretching rate was controlled at 8 m / min. The first part was only stretched longitudinally at a temperature of 110℃ with a stretching ratio of 2.5 times to obtain a gradient surface layer. The second part was synchronously stretched in both directions at a temperature of 115℃ with a longitudinal stretching ratio of 5 times and a transverse stretching ratio of 4 times to obtain a gradient middle layer. The third part was synchronously stretched in both directions at a temperature of 125℃ with a longitudinal stretching ratio of 5.5 times and a transverse stretching ratio of 5.5 times to obtain a gradient bottom layer. After stretching, the gradient surface layer, the gradient middle layer and the gradient bottom layer were stacked and hot-pressed at 135℃ and 0.5 MPa for 5 min to obtain a gradient microporous structure ePTFE membrane. Step 4: The gradient microporous structure ePTFE membrane was plasma cleaned. The cleaning gas was argon and oxygen. The argon flow rate was 70 sccm, the oxygen flow rate was 30 sccm, the plasma power was 100 W, and the cleaning time was 2.5 min. After cleaning, the membrane was immersed in a fluorinated polydimethylsiloxane ethanol solution, ultrasonically treated for 5 min, dried at 80℃ for 2 h in vacuum, immersed in a methyltrimethoxysilane aqueous solution, ultrasonically treated for 10 min, and dried at 60℃ for 15 min to obtain a waterproof and dustproof membrane for electronic products.

[0033] Example 3: A method for preparing a waterproof and dustproof membrane for electronic products, specifically: Step 1: 80 g of PEEK resin, 20 g of coupling agent modified nano-silica, 10 g of maleic anhydride grafted polyether ether ketone, 2.0 g of light stabilizer 770 and 0.5 g of antioxidant 1076 were mixed and then added to a twin-screw extruder for extrusion granulation. The die temperature was set to 350℃, and the screw speed was 200 rpm. The filler masterbatch was obtained. Step 2: 600 g of PTFE resin, 400 g of filler masterbatch and 5 g of lubricant white oil were added to the internal mixer, mixed and kneaded at 200 rpm and 340 ℃ for 5 min, then the speed was adjusted to 100 rpm and the temperature was adjusted to 360 ℃, and the kneading was continued for 10 min, and then the kneading was completed and transferred to a twin-screw extruder for extrusion and granulation, the die temperature was 360 ℃, the screw speed was 100 rpm, and the modified PTFE resin particles were obtained; Step 3: 500 g of modified PTFE resin particles were added to the extruder, the die temperature was set to 370 ℃, the die gap was 0.5 mm, the water-cooled roller temperature was 20 ℃, and a 50 μm thick die blank was extruded, the die blank was divided into 3 parts, and each part was stretched, the stretching rate was controlled at 8 m / min, the first part was only stretched longitudinally, the stretching temperature was 110 ℃, and the stretching ratio was 3 times, to obtain a gradient surface layer, the second part was synchronously stretched in two directions, the stretching temperature was 115 ℃, the longitudinal stretching ratio was 5 times, and the transverse stretching ratio was 4 times, to obtain a gradient middle layer, the third part was synchronously stretched in two directions, the stretching temperature was 125 ℃, the longitudinal stretching ratio was 6 times, and the transverse stretching ratio was 6 times, to obtain a gradient bottom layer, after stretching, heat pressing was performed to combine the gradient surface layer, the gradient middle layer and the gradient bottom layer, and the gradient microporous structure ePTFE film was obtained by heat pressing at 135 ℃ and 0.5 MPa for 5 min. Step 4: The gradient microporous structure ePTFE film was plasma cleaned, the cleaning gas was argon and oxygen, the argon flow rate was 70 sccm, the oxygen flow rate was 30 sccm, the plasma power was 100 W, and the cleaning time was 4 min, then the film was immersed in a fluorinated polydimethylsiloxane ethanol solution, ultrasonically treated for 5 min, vacuum dried at 80 ℃ for 2 h, immersed in a methyltrimethoxysilane aqueous solution, ultrasonically treated for 10 min, and oven dried at 60 ℃ for 15 min, to obtain a waterproof and dustproof film for electronic products.

[0034] Based on Example 1, the following comparative experiments were performed, specifically Comparative Example 1, Comparative Example 2 and Comparative Example 3, as follows: Comparative Example 1: This comparative example relates to a method for preparing a high-temperature-resistant stainless steel for ovens, which is different from Example 1 in that no PEEK resin is added, specifically: Step 1: 100 g of PTFE resin, 15 g of coupling agent modified nano-silicon dioxide, 5 g of maleic anhydride grafted polyether ether ketone, 1.5 g of light stabilizer 770 and 0.3 g of antioxidant 1076 were mixed and then added to a twin-screw extruder for extrusion and granulation, the die temperature was set to 350 ℃, and the screw speed was 200 rpm, to obtain a filler masterbatch; Step 2: 600 g of PTFE resin, 400 g of filler masterbatch and 2 g of lubricant white oil were added into the internal mixer, mixed and kneaded at 200 rpm and 340 ℃ for 5 min, then the speed was adjusted to 100 rpm and the temperature was adjusted to 360 ℃, and the kneading was continued for 10 min, and then the kneading was completed and transferred to a twin-screw extruder for extrusion and granulation, the die temperature was 360 ℃, the screw speed was 100 rpm, and the modified PTFE resin particles were obtained; Step 3: 500 g of modified PTFE resin particles were added into the extruder, the die temperature was set to 370 ℃, the die gap was 0.5 mm, the water-cooled roller temperature was 20 ℃, and a 50 μm thick die blank was extruded, the die blank was divided into three parts, and each part was stretched at a stretching rate of 8 m / min, the first part was only stretched longitudinally, the stretching temperature was 110 ℃, and the stretching ratio was 2.5 times, to obtain a gradient surface layer, the second part was synchronously stretched in two directions, the stretching temperature was 115 ℃, the longitudinal stretching ratio was 4.5 times, and the transverse stretching ratio was 3.5 times, to obtain a gradient intermediate layer, the third part was synchronously stretched in two directions, the stretching temperature was 125 ℃, the longitudinal stretching ratio was 5.5 times, and the transverse stretching ratio was 5.5 times, to obtain a gradient bottom layer, and after stretching, heat pressing was performed to combine the gradient surface layer, the gradient intermediate layer and the gradient bottom layer, and the combined product was obtained by heat pressing at 135 ℃ and 0.5 MPa for 5 min, to obtain a gradient microporous structure ePTFE film; Step 4: The gradient microporous structure ePTFE film was plasma cleaned, the cleaning gas was argon and oxygen, the argon flow rate was 70 sccm, the oxygen flow rate was 30 sccm, the plasma power was 80 W, the cleaning time was 2.5 min, and after cleaning, the film was immersed in a fluorinated polydimethylsiloxane ethanol solution, ultrasonically treated for 5 min, dried at 80 ℃ for 2 h in a vacuum, immersed in a methyltrimethoxysilane aqueous solution, ultrasonically treated for 10 min, and dried at 60 ℃ for 15 min, to obtain a waterproof and dustproof film for electronic products.

[0035] Comparative Example 2: This comparative example relates to a method for preparing a high-temperature-resistant stainless steel for an oven, which is different from Example 1 in that only longitudinal stretching is performed, specifically: Step 1: 100 g of PEEK resin, 15 g of coupling agent modified nano-silicon dioxide, 5 g of maleic anhydride grafted polyether ether ketone, 1.5 g of light stabilizer 770 and 0.3 g of antioxidant 1076 were mixed and then added into a twin-screw extruder for extrusion and granulation, the die temperature was set to 350 ℃, and the screw speed was 200 rpm, to obtain a filler masterbatch; Step 2: 600 g of PTFE resin, 400 g of filler masterbatch and 2 g of lubricant white oil were added into the internal mixer, mixed and kneaded at 200 rpm and 340 ℃ for 5 min, then the speed was adjusted to 100 rpm and the temperature was adjusted to 360 ℃, and the kneading was continued for 10 min, and then the kneading was completed and transferred to a twin-screw extruder for extrusion and granulation, the die temperature was 360 ℃, the screw speed was 100 rpm, and the modified PTFE resin particles were obtained; Step 3: 500 g of modified PTFE resin particles were added into the extruder, the die temperature was set to 370 ℃, the die gap was 0.5 mm, the water-cooled roller temperature was 20 ℃, and the 50 μm thick die blank was extruded, the die blank was longitudinally stretched, the stretching rate was controlled at 8 m / min, the stretching temperature was 110 ℃, and the stretching ratio was 2.5 times, and the microporous structure ePTFE film was obtained; Step 4: The microporous structure ePTFE film was plasma cleaned, the cleaning gas was argon and oxygen, the argon flow was 70 sccm, the oxygen flow was 30 sccm, the plasma power was 80 W, the cleaning time was 2.5 min, then it was immersed in a fluorinated polydimethylsiloxane ethanol solution, ultrasonic treated for 5 min, then vacuum dried at 80 ℃ for 2 h, immersed in a methyltrimethoxysilane aqueous solution, ultrasonic treated for 10 min, and oven dried at 60 ℃ for 15 min, to obtain a waterproof and dustproof film for electronic products.

[0036] Comparative Example 3: This comparative example relates to a method for preparing a high-temperature-resistant stainless steel for ovens, which is different from Example 1 in that no solution immersion treatment is performed, specifically: Step 1: 100 g of PEEK resin, 15 g of coupling agent modified nano-silica, 5 g of maleic anhydride grafted polyether ether ketone, 1.5 g of light stabilizer 770, and 0.3 g of antioxidant 1076 were mixed and then added into a twin-screw extruder for extrusion and granulation, the die temperature was set to 350 ℃, and the screw speed was 200 rpm, to obtain a filler masterbatch; Step 2: 600 g of PTFE resin, 400 g of filler masterbatch and 2 g of lubricant white oil were added into the internal mixer, mixed and kneaded at 200 rpm and 340 ℃ for 5 min, then the speed was adjusted to 100 rpm and the temperature was adjusted to 360 ℃, and the kneading was continued for 10 min, and then the kneading was completed and transferred to a twin-screw extruder for extrusion and granulation, the die temperature was 360 ℃, the screw speed was 100 rpm, and the modified PTFE resin particles were obtained; Step 3: 500 g of modified PTFE resin particles were added to an extruder, the die temperature was set to 370℃, the die gap was 0.5 mm, the water-cooled roller temperature was 20℃, and an extrusion 50 μm thick was obtained. The extrusion was divided into three parts, and each part was stretched at a stretching rate of 8 m / min. The first part was only stretched longitudinally at a stretching temperature of 110℃ and a stretching ratio of 2.5 times to obtain a gradient surface layer. The second part was synchronously stretched in two directions at a stretching temperature of 115℃, a longitudinal stretching ratio of 4.5 times, and a transverse stretching ratio of 3.5 times to obtain a gradient intermediate layer. The third part was synchronously stretched in two directions at a stretching temperature of 125℃, a longitudinal stretching ratio of 5.5 times, and a transverse stretching ratio of 5.5 times to obtain a gradient bottom layer. After stretching, the gradient surface layer, the gradient intermediate layer, and the gradient bottom layer were stacked in order and hot-pressed at 135℃ and 0.5 MPa for 5 min to obtain a waterproof and dustproof film for electronic products.

[0037] Detection experiment: A waterproof and dustproof film for electronic products was prepared according to each embodiment and the comparative example, respectively, as a test sample for contact angle test, waterproof and dustproof test, air permeability test, and weather resistance test.

[0038] Contact angle test: The test was performed according to the reference “Measurement of the contact angle between a plastic film and water” (GB / T 30693-2014). The test sample was cut into a size of 100 mm x 100 mm, the surface was cleaned with deionized water by ultrasonic, and then dried at 30℃ with cold air. The contact angle measuring instrument was preheated for 30 min, 10 μL of deionized water was added to the surface of the test sample using a microsyringe, and the droplet was ensured to drop vertically on the test sample without sliding or splashing. The contact angle of the test sample was calculated by taking a picture of the droplet using the contact angle measuring instrument. The measurement was performed 5 times, and the average value was taken as the result.

[0039] Waterproof and dustproof test: The waterproof and dustproof test of the sample was performed according to the international standard “Protection provided by enclosures (IP code)” (IEC 60259). The test sample for electronic products was completely wrapped to ensure that the edges were sealed, and then waterproof and dustproof tests were performed according to different test methods to determine the waterproof and dustproof levels. Waterproof level: IPX1 level - protection against vertically falling water droplets; IPX2 - protection against straight water spray at an angle of 15° to the vertical direction; IPX3 - protection against straight water spray at an angle of 60° to the vertical direction; IPX4 - protection against water spray in all directions; IPX5 - protection against water jets in all directions; IPX6 - protection against strong water spray in all directions; IPX7 - immersion in water with a depth of 15 cm to 1 m for not more than 30 min; IPX8 - immersion in water with a depth of 1.5 m for not more than 30 min; Dustproof level: IP1X - prevent solids with a diameter of more than 50 mm from entering; IP2X - prevent solids with a diameter of more than 12 mm from entering; IP3X - prevent solids with a diameter of more than 2.5 mm from entering; IP4X - prevent solids with a diameter of more than 1 mm from entering; IP5X - allow limited dust to enter; IP6X - do not allow dust to enter.

[0040] Air permeability test: The test refers to "Determination of water vapor transmission rate of plastics films and sheets - Electrolytic sensor method" (GB / T 21529-2008). After cutting the test sample into a circle with a diameter of 70 mm, it is clamped between the dry chamber and the wet chamber of the water vapor transmission rate tester. The chamber is sealed, the vacuum system is started to exhaust the air in the chamber, the water vapor generator in the wet chamber is started, the relative humidity is maintained at 90%, dry nitrogen is introduced into the dry chamber at a flow rate of 50 mL / min for purging, the relative humidity is maintained at 10%, the electrolytic sensor of the tester is started, and the electrolytic current is recorded after it is stable. The water vapor transmission rate of the test sample is calculated according to the electrolytic current.

[0041] Weather resistance test: The test refers to "Methods of exposure to laboratory light sources - Part 1: General" (GB / T 16422.1-2019). The test sample is divided into 6 pieces of 50 mm x 100 mm size, 3 of which are randomly selected and measured for tensile strength using a universal mechanical testing machine, and the average value is taken. The remaining 3 are placed in an ultraviolet aging test chamber and aged using a 360 nm UV light source. The temperature in the aging chamber is 60°C, the irradiation intensity is 0.89 W / m 2 , and the tensile strength after aging is measured after aging for 500 h. The average value is taken and the tensile strength retention rate of the test sample is calculated.

[0042] Conclusion: From the test data, it can be seen that the contact angle, water vapor transmission rate and tensile strength retention rate of the waterproof and dustproof film for electronic products provided by the examples are better than those of the waterproof and dustproof film for electronic organ products provided by the comparative examples, and the waterproof and dustproof level is also very high. The waterproof and dustproof film for electronic products provided by the present application has excellent hydrophobicity, waterproof and dustproof performance, and good air permeability and weather resistance.

[0043] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A method for preparing a waterproof and dustproof film for electronic products, characterized by: Specifically: Step 1: After mixing the polyether ether ketone resin and functional additives, extrusion granulation is performed to obtain a filler master batch; Step 2: The polytetrafluoroethylene resin, the filler master batch and the lubricant white oil are mixed and milled to obtain modified PTFE resin particles; Step 3: The modified PTFE resin particles are extruded to form a blank, the blank is divided into three parts, and after stretching, stacking and hot pressing, a gradient microporous structure ePTFE film is obtained; Step 4: After the gradient microporous structure ePTFE film is plasma cleaned, it is immersed in a solution of fluorinated polydimethylsiloxane in ethanol and a solution of methyltrimethoxysilane in water, and dried to obtain a waterproof and dustproof film for electronic products.

2. The method for preparing a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The functional additives include coupling agent modified nano silicon dioxide, maleic anhydride grafted polyether ether ketone, light stabilizer 770 and antioxidant 1076; the filler master batch includes, by mass fraction: 80-100 parts of polyether ether ketone resin, 15-20 parts of coupling agent modified nano silicon dioxide, 5-10 parts of maleic anhydride grafted polyether ether ketone, 1.5-2.5 parts of light stabilizer 770 and 0.3-1.0 parts of antioxidant 1076; the process parameters during extrusion granulation include: die temperature: 350-360℃, screw rotation speed: 150-200rpm.

3. The method of claim 2, wherein the method is characterized by: The preparation method of the coupling agent modified nano silicon dioxide is as follows: The nano silicon dioxide is added to a mixed solution of ethanol and deionized water, ultrasonically dispersed for 10-20min, then the silane coupling agent KH-550 is added, and the reaction is carried out at 80-90℃ for 1-2h. After the reaction is completed, cooling, centrifugal separation, washing with ethanol and deionized water, and drying at 70-80℃ for 2-3h, the coupling agent modified nano silicon dioxide is obtained.

4. The preparation method of a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The mass ratio of the polytetrafluoroethylene resin to the filler master batch is (6-7):(3-4); the mass of the lubricant white oil accounts for 0.2%-0.5% of the total mass of the modified PTFE resin particles; the milling is divided into two stages, the process parameters of the first stage include: rotation speed: 180-200rpm, milling temperature: 330-340℃, and milling time: 3-5min; the process parameters of the second stage include: rotation speed: 80-100rpm, milling temperature: 350-360℃, and milling time: 8-10min; the process parameters during extrusion granulation include: die temperature: 360-370℃, and screw rotation speed: 100-120rpm.

5. The method for preparing a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The preparation method of the gradient microporous structure ePTFE film is as follows: The modified PTFE resin particles are added to an extruder, the die temperature is set to 360-370℃, the die gap is 0.5-1mm, and the water-cooled roller temperature is 20-30℃, the blank is extruded, the blank is divided into three parts, stretching is performed on each part, the stretching rate is controlled to be 8-10m / min, the gradient surface layer, the gradient middle layer and the gradient bottom layer are formed, after the stretching is completed, hot pressing is performed, the gradient surface layer, the gradient middle layer and the gradient bottom layer are stacked in turn, hot pressing is performed at 130-140℃ and 0.4-0.5MPa for 5-8min to obtain the gradient microporous structure ePTFE film.

6. The method of claim 5, wherein the method is characterized by: For forming the gradient surface layer, only longitudinal stretching is performed at a stretching temperature of 105-110 DEG C and a stretching ratio of 2-3 times; for forming the gradient intermediate layer, two-way synchronous stretching is performed at a stretching temperature of 115-120 DEG C, a longitudinal stretching ratio of 4-5 times and a transverse stretching ratio of 3-4 times; and for forming the gradient bottom layer, two-way synchronous stretching is performed at a stretching temperature of 125 DEG C, a longitudinal stretching ratio of 5-6 times and a transverse stretching ratio of 5-6 times.

7. The method for preparing a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The argon and oxygen are introduced during the plasma cleaning; and the process parameters of the plasma cleaning include: argon flow rate: 70-80 sccm, oxygen flow rate: 20-30 sccm, plasma power: 80-100 W, and cleaning time: 2-5 min.

8. The method for preparing a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The fluorinated polydimethylsiloxane ethanol solution contains 0.3-0.5 wt% fluorinated polydimethylsiloxane; and the methyltrimethoxysilane aqueous solution contains 0.5-1 wt% methyltrimethoxysilane.

9. The method for preparing a waterproof and dustproof film for electronic products according to claim 1, characterized in that: The fluorinated polydimethylsiloxane ethanol solution is impregnated under ultrasonic treatment for 5-8 min, and then vacuum dried at 80-90 DEG C for 1.5-2 h; and the methyltrimethoxysilane aqueous solution is impregnated under ultrasonic treatment for 10-15 min, and then baked at 60-70 DEG C for 15-30 min.

10. A waterproof and dustproof film for electronic products, characterized by: The preparation method is prepared by any one of claims 1-9.

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