Background
The Polytetrafluoroethylene (PTFE) film is a micron-sized film layer, is very light and thin, needs to be compounded with other base materials, and has the functions of filtration, water resistance, ventilation and the like. However, during the circulation, compounding and use processes, the polytetrafluoroethylene film is easy to generate microcracks and even break, so that the material fails. For example, a film on a film-coated filter bag used in a cement plant cracks, holes are formed after the cracks gradually increase, dust rapidly enters a base material to form a compact powder cake layer on the base material, the filtration resistance is increased, the dust cleaning period is shortened, and the filter bag is aged in advance to cause failure of the filter bag. For another example, the waterproof moisture-permeable fabric is composed of a fabric and a PTFE film, and the film is easy to crack due to insufficient toughness in the process of turnover and lamination; after the clothes are made, the film is damaged and the function is invalid due to continuous twisting in the process of cleaning.
The polytetrafluoroethylene film is a fiber-node interweaving structure, the toughness of the film is provided by the connection between fibers and nodes, when the force between the fibers and the nodes is insufficient, microcracks are firstly generated on the fibers, and after the force is gathered, the fibers are broken, and finally the film is damaged. Chinese patent application CN112111075A discloses a polytetrafluoroethylene film and a method for manufacturing the same, which refers to a method for preparing a high-strength polytetrafluoroethylene film, wherein the polytetrafluoroethylene film is rolled after being cut, and the method can improve the mechanical strength of the polytetrafluoroethylene film, but cannot meet the requirements of a high-permeability film and the resistance requirements of the filtration industry. The Chinese patent application CN109627651A discloses a method for functionalizing a polytetrafluoroethylene film, which realizes functionalization by adding graphite, a wear-resisting agent, an antistatic agent and the like, but the product produced by the method is not suitable for the filtration industry and can not meet the requirements on filtration efficiency and resistance.
Disclosure of Invention
The invention aims to provide a preparation method of a polytetrafluoroethylene microporous membrane.
The technical scheme for realizing the purpose of the invention is as follows:
a preparation method of a polytetrafluoroethylene microporous membrane comprises the following steps:
mixing polytetrafluoroethylene resin, an extrusion aid, a toughening agent and a film forming agent in proportion, aging at a low temperature of 30-60 ℃, pressing into a cylindrical blank, extruding and rolling into a sheet, and stretching longitudinally and transversely to prepare the high-toughness polytetrafluoroethylene film.
In the invention, the extrusion aid is an extrusion aid which is conventionally used in the field, such as aviation kerosene, paraffin oil and the like.
In the invention, the film forming agent is selected from silane coupling agent, ethylene glycol butyl ether EB, propylene glycol methyl ether PM, propylene glycol ethyl ether and the like.
In the invention, the toughening agent is selected from silicon dioxide nano particles, cerium dioxide, chromium dioxide, zirconium dioxide and the like.
In the invention, the mass ratio of the polytetrafluoroethylene resin, the extrusion aid, the toughening agent and the film forming agent is 75-80: 11-20: 0.1-5: 0.9 to 5.
In a particular embodiment of the invention, the aging temperature is 45 ℃.
In the invention, the aging time is 12-48 h. In a particular embodiment of the invention, the aging time is 24 h.
In the present invention, the thickness of the sheet is 100 to 320 μm. In a specific embodiment of the present invention, the thickness of the sheet is 160 to 280 μm.
Compared with the prior art, the invention has the following advantages:
(1) the toughening agent is added to improve the connecting force between the fibers and the nodes, so that the mechanical property of the film is improved;
(2) by adding the film forming agent, organic polytetrafluoroethylene and inorganic particles are linked, and a film layer is formed between the fiber-fiber and the fiber-node, so that the PTFE and the inorganic toughening agent can be better combined, the effect of the toughening agent is further promoted, the reinforcing effect is achieved, the toughness of the film is increased in the fiber-node structure, and the mechanical property of the film is fully improved under the condition of not changing the thickness and the air permeability of the film.
Detailed Description
The present invention will be described in more detail with reference to examples.
Example 1
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to the mass ratio of 78:20:0.5:1.5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 9.8cm/s, the stretching strength of 35MPa in the warp direction and 33MPa in the weft direction.
Example 2
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to the mass ratio of 75:20:0.5:4.5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 9.6cm/s, the stretching strength of 34MPa in the warp direction and 32MPa in the weft direction.
Example 3
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to a mass ratio of 80:14:1:5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and biaxially stretching under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 10.2cm/s, the stretching strength is 36MPa in the warp direction and 32MPa in the weft direction.
Example 4
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to the mass ratio of 80:19:0.1:0.9, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 9.7cm/s, the stretching strength of 35MPa in the warp direction and 34MPa in the weft direction.
Example 5
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to a mass ratio of 79:11:5:5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and biaxially stretching under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 10.4cm/s, the stretching strength is 34MPa in the warp direction and 31MPa in the weft direction.
Example 6
Selecting a Dajin F104 polytetrafluoroethylene dispersion resin, mixing the dispersion resin with aviation kerosene, a silane coupling agent 151 and nano zirconium dioxide according to a mass ratio of 77:20:0.5:2.5, aging at 45 ℃ for 24 hours to prepare a cylindrical blank, extruding and rolling the cylindrical blank into a sheet with the thickness of 220 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 10 times, the temperature is 250 ℃ and the stretching linear speed is 18m/min to prepare a PTFE film with the air permeability of 10.2cm/s, the stretching strength of 36MPa in the warp direction and 37MPa in the weft direction.
Example 7
Selecting Dongyue DF204 polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, propylene glycol methyl ether PM and nano cerium dioxide according to a mass ratio of 76:20:0.8:3.2, aging at 45 ℃ for 24 hours to prepare a cylindrical blank, extruding and rolling the cylindrical blank into a sheet with the thickness of 160 mu m, deoiling the cylindrical blank, and stretching the cylindrical blank in two directions under the conditions that the stretching ratio is 7 times, the temperature is 240 ℃ and the stretching linear speed is 15m/min to prepare the PTFE film with the air permeability of 11.5cm/s, the stretching strength of 36MPa in the warp direction and 34MPa in the weft direction.
Example 8
Selecting giant JF-4D polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, propylene glycol ether and chromium dioxide according to the mass ratio of 76:20:0.8:3.2, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 280 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 11 times, the temperature is 280 ℃ and the stretching linear speed is 20m/min, so that the prepared PTFE film has the air permeability of 10.9cm/s, the stretching strength of 36MPa in the warp direction and 34MPa in the weft direction.
Comparative example 1
Selecting giant JF-4D polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, propylene glycol methyl ether PM and zinc oxide according to the mass ratio of 76:20:0.8:3.2, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 280 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 11 times, the temperature is 280 ℃ and the stretching linear speed is 20m/min, so that the prepared PTFE film has the air permeability of 3.2cm/s, the stretching strength of 12MPa in the warp direction and the stretching strength of 5MPa in the weft direction.
Comparative example 2
Selecting giant JF-4D polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, epoxy resin and nano silicon dioxide according to the mass ratio of 76:20:0.8:3.2, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 280 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 11 times, the temperature is 280 ℃ and the stretching linear speed is 20m/min, so that the prepared PTFE film has the air permeability of 2.1cm/s, the stretching strength of 6MPa in the warp direction and 5MPa in the weft direction.
Comparative example 3
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to a mass ratio of 60:30:5:5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling into a sheet with the thickness of 180 mu m, deoiling, and biaxially stretching under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 2.7cm/s, the stretching strength is 11MPa in the warp direction and 4MPa in the weft direction.
Comparative example 4
Selecting DuPont 605XTX polytetrafluoroethylene dispersion resin, mixing with aviation kerosene, ethylene glycol monobutyl ether EB and nano silicon dioxide according to the mass ratio of 85:9.5:5:0.5, aging at 45 ℃ for 24 hours, preparing a cylindrical blank, extruding and rolling the cylindrical blank into a sheet with the thickness of 180 mu m, deoiling, and stretching in two directions under the conditions that the stretching ratio is 8 times, the temperature is 240 ℃ and the stretching linear speed is 16m/min, so that the prepared PTFE film has the air permeability of 4cm/s, the stretching strength of 6MPa in the warp direction and 7MPa in the weft direction.