Preparation method of deep waterproof expanded polytetrafluoroethylene sound transmission membrane

Abstract

The invention relates to the technical field of polytetrafluoroethylene sound transmission membranes, in particular to a preparation method of a deep waterproof expanded polytetrafluoroethylene sound transmission membrane. Through the steps of material mixing, aging, pre-forming, pushing forming, calendaring forming, high-temperature degreasing, longitudinal stretching, transverse stretching, high-temperature shaping, post-covering treatment and the like, on the premise that the ultrahigh water pressure resistance of the ePTFE film is guaranteed, the air permeability of the ePTFE film is improved as much as possible, and the ePTFE film is made as thin as possible, so that the sound transmission effect of the film is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene sound-permeable membranes, in particular to a method for preparing a deeply waterproof expanded polytetrafluoroethylene sound-permeable membrane. Background Art

[0002] Expanded polytetrafluoroethylene (ePTFE) membrane material is made by high-temperature biaxial stretching process, forming a three-dimensional mesh microporous structure during the preparation process. These micropores make the ePTFE membrane have good air permeability; at the same time, the low surface energy of the polytetrafluoroethylene membrane makes the ePTFE membrane have good waterproof performance; Therefore, expanded polytetrafluoroethylene (ePTFE) membrane materials are widely used in waterproof and breathable products for automobiles, smart electronics, small household appliances and other equipment. Among them, smart portable electronics such as mobile phones, children's call watches, and smart bracelets are the most widely used. These products require basic breathability and at least IP68 waterproof performance, while also requiring the ePTFE membrane to have good sound permeability. However, if you want to obtain an ePTFE membrane material with higher waterproof performance, you must reduce the average pore size of the ePTFE membrane material to increase the water pressure resistance, but this will inevitably reduce the air permeability of the ePTFE membrane, thereby affecting the sound transmission effect of the ePTFE membrane; Therefore, how to obtain ePTFE membrane materials that have both high water pressure resistance and excellent sound transmission has become an urgent problem to be solved. Summary of the invention

[0003] 1. Technical issues to be resolved The present invention solves the problem of how to obtain an ePTFE membrane material having both high water pressure resistance and excellent sound transmission effect, which becomes an urgent problem to be solved.

[0004] (II) Technical solution To achieve the above, under the premise of ensuring the ultra-high water pressure resistance of the ePTFE membrane, the air permeability of the ePTFE membrane is increased as much as possible, and the ePTFE membrane is made as thin as possible to ensure the sound transmission effect of the membrane. The preparation steps of the present invention include: mixing, aging, preforming, push forming, calendering, high-temperature degreasing, longitudinal stretching, transverse stretching and high-temperature shaping, and post-lamination treatment. The present invention provides the following technical solutions: A method for preparing a deep waterproof expanded polytetrafluoroethylene sound-permeable membrane, comprising the following steps: Step 1, mixing: mix the polytetrafluoroethylene PTFE dispersion resin and the lubricant according to a certain method, add 5 kg of PTFE dispersion resin and 1.1 kg of lubricant into a dry material mixer, the mixing temperature is 13-17 ° C, the speed of the dry material mixer is 20-25 rpm, the mixing time is 20-30 minutes, and the final mixture is visually uniform, the mixture is a loose powder, and there are no obvious large particles; Step 2, aging: placing the uniformly mixed mixture in an oven for aging, the purpose is to fully blend the PTFE dispersion resin and the lubricant; the aging treatment temperature is 50° C., and the aging time is 15 hours; Step 3, preforming: the mixed material aged in step 2 is first sieved with an 8-mesh screen, and then poured into a pelletizing machine through a hopper for pre-pressing; the cylinder pressure is 3.5 MPa, the pelletizing speed is 10 cm / min, the pelletizing time is 12 minutes, and the pellet diameter is 120 mm; Step 4: Pressing and molding: The pre-pressed green body obtained in step 3 is loaded into a press machine, and is pressed into a PTFE rod with a diameter of 23 mm at a pressing speed of 28 cm / min and a pressing force of 8 MPa; the pressed PTFE rod needs to be placed in a 50°C insulation water tank for insulation, and the compression ratio RR of the rod is 28; Step 5, calendering: the PTFE material rod obtained in step 4 is sent to a double-roll calender through a guide plate to be calendered into a PTFE material strip; the temperature of the calendering roller is 50°C, the calendering speed is 9m / min, the material strip thickness is 0.22-0.25mm, and the material strip width is 190-210mm; Step 6, high temperature degreasing: the PTFE tape obtained in step 5 is degreased in a high temperature degreasing oven to remove the lubricant; the temperature of the heating roller is 160-190°C, and the feeding speed is 2m / min; Step 7, longitudinal stretching: longitudinally stretch the degreased PTFE tape along the tape direction in a longitudinal stretching oven; the stretching multiple is 5 times, the stretching roller speed is 2-10 m / min, the stretching roller temperature is 190-220°C, and the PTFE tape after longitudinal stretching has a tape thickness of 0.2-0.23 mm and a tape width of 170-190 mm; Step eight, transverse stretching and high-temperature shaping: fix the two sides of the PTFE tape obtained in step seven by a cloth clip feeding belt, and perform transverse stretching and high-temperature shaping in a transverse stretching oven; the transverse stretching oven is a segmented oven with a total length of 38m, divided into 4 zones: ① preheating zone length 10m, temperature 120~160℃; ② transverse stretching zone 8m, temperature 180~250℃; ③ high-temperature shaping zone 16m, temperature 330~350℃; ④ cooling zone 4m, temperature 40~60℃; transverse stretching multiple is 5 times, and the stretching roller speed is 14m / min; in the transverse stretching zone, the top is equipped with a matrix medium-wave auxiliary heating unit with a temperature of 200~300℃, which is used to control the uniform stretching of the middle and edge of the film; The parameters of the ePTFE membrane after transverse stretching and high-temperature shaping are: membrane thickness 0.05~0.08mm, effective width of the material strip 1000~1100mm, membrane pore size 0.05um~0.1um, air permeability 400~600ml / min / cm2@7Kpa, water pressure resistance 500Kpa for 30min, test pore size 1.6mm; Step nine, post-lamination treatment: trim the ePTFE membrane obtained in step eight by 100 mm on both sides, laminate it with 1-3g silicone protective film, and press it with a double soft rubber roller press to make the ePTFE membrane thinner, thereby obtaining a waterproof ePTFE sound-permeable membrane that is resistant to 50 meters in depth.

[0005] In the step 1, the polytetrafluoroethylene (PTFE) dispersion resin model is Japan Daikin F104, and the lubricant is isododecane (ISOPAR L); the weight ratio is: ISOPAR L: PTFE dispersion resin: 22%.

[0006] The ePTFE membrane parameters are: membrane thickness 0.015~0.025mm, effective width of the material strip 700~800mm, membrane pore size 0.05um~0.1um, air permeability 300~500ml / min / cm2@7Kpa, water pressure resistance 500Kpa for 10min test pore size 1.6mm, sound transmission loss at 1KHz sound frequency is less than 2dB, and less than 2dB in the entire band of 100Hz~10KHz.

[0007] (III) Beneficial effects Compared with the prior art, the present invention provides a method for preparing a deep waterproof expanded polytetrafluoroethylene sound-permeable membrane, which has the following beneficial effects: 1. The present invention realizes that the air permeability of the ePTFE membrane is increased as much as possible while ensuring the ultra-high water pressure resistance of the ePTFE membrane through the steps of mixing, aging, preforming, push-forming, calendering, high-temperature degreasing, longitudinal stretching, transverse stretching and high-temperature shaping, and post-lamination treatment, and the ePTFE membrane is made as thin as possible to ensure the sound transmission effect of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of a workbench for testing the water pressure resistance of the tetrafluoroethylene sound-transmitting membrane in Example 1 of the expanded polytetrafluoroethylene of the present invention; Figure 2 This is a schematic diagram of the initial stage of the water pressure resistance test of the polytetrafluoroethylene sound-permeable membrane in Example 1 of the present invention; Figure 3 This is a schematic diagram of the later stage of the water pressure resistance test of the polytetrafluoroethylene sound-permeable membrane in Example 1 of the present invention; Figure 4 This is a sound transmission loss curve of the polytetrafluoroethylene sound-permeable membrane in Example 1 of the present invention; Figure 5 This is a schematic diagram of a workbench for testing the water pressure resistance of the tetrafluoroethylene sound-transmitting membrane in the second embodiment of the expanded polytetrafluoroethylene of the present invention; Figure 6 This is a schematic diagram of the initial stage of the water pressure resistance test of the polytetrafluoroethylene sound-permeable membrane in the second embodiment of the present invention; Figure 7 This is a schematic diagram of the later stage of the water pressure resistance test of the polytetrafluoroethylene sound-permeable membrane in the second embodiment of the present invention; Figure 8 This is a sound transmission loss curve of the polytetrafluoroethylene sound-permeable membrane in Example 2 of the present invention. DETAILED DESCRIPTION

[0009] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0010] See also Figure 1-Figure 4 , Embodiment 1: A method for preparing an ePTFE sound-permeable membrane that is waterproof to a depth of 50 meters, the detailed steps are as follows: Step 1, mixing: Mix the polytetrafluoroethylene (PTFE) dispersion resin and the lubricant according to a certain method, add 5kg of PTFE dispersion resin and 1.1kg of lubricant into a dry material mixer, the mixing temperature is 13-17℃, the speed of the dry material mixer is 20-25 rpm, the mixing time is 20-30 minutes, and the final mixture is visually uniform, the mixture is a loose powder, and there are no obvious large particles; Note: In this embodiment, the polytetrafluoroethylene (PTFE) dispersion resin model is Japan Daikin F104, and the lubricant is isododecane (ISOPAR L); weight ratio: ISOPAR L: PTFE dispersion resin: 22%.

[0011] Step 2, aging: placing the uniformly mixed mixture in an oven for aging, the purpose is to fully blend the PTFE dispersion resin and the lubricant; the aging treatment temperature is 50° C., and the aging time is 15 hours; Step 3, preforming: the mixed material aged in step 2 is first sieved with an 8-mesh screen, and then poured into a pelletizing machine through a hopper for pre-pressing; the cylinder pressure is 3.5 MPa, the pelletizing speed is 10 cm / min, the pelletizing time is 12 minutes, and the pellet diameter is 120 mm; Step 4, pushing and pressing: the pre-pressed green body obtained in step 3 is loaded into a pushing machine, and is pushed into a PTFE material rod with a diameter of 23 mm at a pushing speed of 28 cm / min and a pushing force of 8 MPa; the pushed PTFE material rod needs to be placed in a 50° C. insulation water tank for insulation; the compression ratio RR of the material rod in this embodiment is 28; Step 5, calendering: the PTFE material rod obtained in step 4 is sent to a double-roll calender through a guide plate to be calendered into a PTFE material strip; the temperature of the calendering roller is 50°C, the calendering speed is 9m / min, the material strip thickness is 0.22-0.25mm, and the material strip width is 190-210mm; Step 6, high temperature degreasing: the PTFE tape obtained in step 5 is degreased in a high temperature degreasing oven to remove the lubricant; the temperature of the heating roller is 160-190°C, and the feeding speed is 2m / min; Step 7, longitudinal stretching: longitudinally stretch the degreased PTFE tape along the tape direction in a longitudinal stretching oven; the stretching multiple is 5 times, the stretching roller speed is 2-10 m / min, the stretching roller temperature is 190-220°C, and the PTFE tape after longitudinal stretching has a tape thickness of 0.2-0.23 mm and a tape width of 170-190 mm; Step eight, transverse stretching and high-temperature shaping: fix the two sides of the PTFE tape obtained in step seven with cloth clip feeding belts, and perform transverse stretching and high-temperature shaping in a transverse stretching oven; the transverse stretching oven is a segmented oven with a total length of 38m, divided into 4 zones: ① preheating zone is 10m long, with a temperature of 120~160℃; ② transverse stretching zone is 8m, with a temperature of 180~250℃; ③ high-temperature shaping zone is 16m, with a temperature of 330~350℃; ④ cooling zone is 4m, with a temperature of 40~60℃. The transverse stretching multiple is 5 times, and the stretching roller speed is 14m / min. The top of the transverse stretching zone is equipped with a matrix medium-wave auxiliary heating unit with a temperature of 200~300℃, which is used to control the uniform stretching of the middle and edges of the film; The parameters of the ePTFE membrane after transverse stretching and high-temperature shaping are as follows: membrane thickness 0.05~0.08mm, effective width of the material strip 1000~1100mm. Membrane pore size 0.05um~0.1um, air permeability 400~600ml / min / cm2@7Kpa, water pressure resistance 500Kpa pressure holding 30min (test pore size 1.6mm); Step nine, post-lamination treatment: trim the ePTFE membrane obtained in step eight on both sides by at least 100 mm, laminate it with a 1-3g silicone protective film, and press it with a double soft rubber roller press to make the ePTFE membrane thinner, thereby obtaining a waterproof ePTFE sound-permeable membrane that is resistant to a depth of 50 meters.

[0012] The parameters of the deep waterproof ePTFE sound-permeable membrane prepared in Example 1 of the present invention are as follows: Film thickness 0.015~0.025mm; The effective width of the material strip is 700~800mm. Membrane pore size 0.05um~0.1um, Air permeability 300~500ml / min / cm2@7Kpa, Figure 1-Figure 3 The test was carried out under the condition of water pressure resistance of 500Kpa for 10min (test aperture 1.6mm).

[0013] Figure 4 The environment is that the sound transmission loss is less than 2dB at 1KHz sound frequency and less than 2dB in the entire band of 100Hz~10KHz.

[0014] See also Figure 5-Figure 8 , Embodiment 2: A method for preparing an ePTFE sound-permeable membrane that is waterproof to a depth of 30 meters, the detailed steps are as follows: Step 1, mixing: Mix the polytetrafluoroethylene (PTFE) dispersion resin and the lubricant according to a certain method. Add 5 kg of PTFE dispersion resin and 1.3 kg of lubricant into a dry material mixer. The mixing temperature is 13-17 ° C, the speed of the dry material mixer is 20-25 rpm, and the mixing time is 30-35 minutes. Finally, the mixture is visually uniform, the mixture is a loose powder, and there are no obvious large particles.

[0015] Note: In this embodiment, the polytetrafluoroethylene (PTFE) dispersion resin model is American Chemours 605XT, and the lubricant is isotridecane (ISOPAR M); weight ratio: ISOPAR M: PTFE dispersion resin: 26%.

[0016] Step 2: Aging: The uniformly mixed mixture is placed in an oven for aging, the purpose of which is to fully blend the PTFE dispersion resin and the lubricant. The aging treatment temperature is 55° C. and the aging time is 18 hours.

[0017] Step 3, preforming: the mixed material after aging in step 2 is first sieved with an 8-mesh screen, and then poured into the pellet press through the hopper for pre-pressing. The cylinder pressure is 4.0 MPa, the pellet pressing speed is 10 cm / min, the pellet pressing time is 10 minutes, and the pellet diameter is 120 mm.

[0018] Step 4: Pressing: Load the pre-pressed green body obtained in step 3 into a press machine, and press it into a PTFE rod with a diameter of 16.8 mm at a pressing speed of 28 cm / min and a pressing force of 8 MPa. The pressed PTFE rod needs to be placed in a 50°C insulated water tank for heat preservation. The compression ratio RR of the rod in this embodiment is 51.

[0019] Step 5, calendering: The PTFE material rod obtained in step 4 is sent to a double-roll calender through a guide plate to be calendered into a PTFE material strip. The temperature of the calendering roller is 50°C, the calendering speed is 9m / min, the material strip thickness is 0.22-0.25mm, and the material strip width is 170-190mm.

[0020] Step 6, high temperature degreasing: The PTFE tape obtained in step 5 is degreased in a high temperature degreasing oven to remove the lubricant. The temperature of the heating roller is 160-190°C, and the material feeding speed is 2m / min.

[0021] Step 7, longitudinal stretching: longitudinally stretch the degreased PTFE tape along the tape direction in a longitudinal stretching oven. The stretching multiple is 7 times, the stretching roller speed is 2~10m / min, the stretching roller temperature is 190~220℃, and the PTFE tape after longitudinal stretching has a tape thickness of 0.2~0.23mm and a tape width of 150~170mm.

[0022] Step eight, transverse stretching and high-temperature shaping: Fix the two sides of the PTFE tape obtained in step seven with the cloth clip feeding belt, and perform transverse stretching and high-temperature shaping in the transverse stretching oven. The transverse stretching oven is a segmented oven with a total length of 38m, divided into 4 zones: ① The preheating zone is 10m long and the temperature is 120~160℃; ② The transverse stretching zone is 8m long and the temperature is 180~250℃; ③ The high-temperature shaping zone is 16m long and the temperature is 330~350℃; ④ The cooling zone is 4m and the temperature is 40~60℃. The transverse stretching multiple is 7 times, and the stretching roller speed is 16m / min. In the transverse stretching zone, the top is equipped with a matrix medium-wave auxiliary heating unit with a temperature of 200~300℃, which is used to control the uniform stretching of the middle and edges of the film.

[0023] The parameters of the ePTFE membrane after transverse stretching and high-temperature shaping are as follows: membrane thickness 0.05~0.08mm, material strip width 1100~1200mm, membrane pore size 0.2um~0.3um, air permeability 1100~1300ml / min / cm2@7Kpa, water pressure resistance 300Kpa pressure holding 30min (test pore size 1.6mm).

[0024] Step nine, post-lamination treatment: trim the ePTFE membrane obtained in step eight on both sides by at least 100 mm, laminate it with 1-3g silicone protective film, and press it with a double soft rubber roller press to make the thickness of the ePTFE membrane thinner, thereby obtaining a deeply waterproof ePTFE sound-permeable membrane.

[0025] The parameters of the deep waterproof ePTFE sound-permeable membrane prepared in Example 2 of the present invention are as follows: Film thickness 0.01~0.03mm, Strip width 900~1000mm, Membrane pore size 0.2um~0.3um, Air permeability 1000~1200ml / min / cm2@7Kpa, Figure 5-Figure 7 The test was carried out under the condition of water pressure resistance of 300Kpa for 10min (test aperture 1.6mm).

[0026] Figure 8 The environment is that the sound transmission loss is less than 1.5dB at 1KHz sound frequency and less than 1.5dB in the entire band of 100Hz~10KHz.

[0027] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a deep waterproof expanded polytetrafluoroethylene sound-permeable membrane, characterized in that: The following steps are involved: Step 1, mixing: mix the polytetrafluoroethylene PTFE dispersion resin and the lubricant according to a certain method, add 5 kg of PTFE dispersion resin and 1.1 kg of lubricant into a dry material mixer, the mixing temperature is 13-17 ° C, the speed of the dry material mixer is 20-25 rpm, the mixing time is 20-30 minutes, and the final mixture is visually uniform, the mixture is a loose powder, and there are no obvious large particles; Step 2, aging: placing the uniformly mixed mixture in an oven for aging, the purpose is to fully blend the PTFE dispersion resin and the lubricant; the aging treatment temperature is 50° C., and the aging time is 15 hours; Step 3, preforming: the mixed material aged in step 2 is first sieved with an 8-mesh screen, and then poured into a pelletizing machine through a hopper for pre-pressing; the cylinder pressure is 3.5 MPa, the pelletizing speed is 10 cm / min, the pelletizing time is 12 minutes, and the pellet diameter is 120 mm; Step 4: Pressing and molding: The pre-pressed green body obtained in step 3 is loaded into a press machine, and is pressed into a PTFE rod with a diameter of 23 mm at a pressing speed of 28 cm / min and a pressing force of 8 MPa; the pressed PTFE rod needs to be placed in a 50°C insulation water tank for insulation, and the compression ratio RR of the rod is 28; Step 5, calendering: the PTFE material rod obtained in step 4 is sent to a double-roll calender through a guide plate to be calendered into a PTFE material strip; the temperature of the calendering roller is 50°C, the calendering speed is 9m / min, the material strip thickness is 0.22-0.25mm, and the material strip width is 190-210mm; Step 6, high temperature degreasing: the PTFE tape obtained in step 5 is degreased in a high temperature degreasing oven to remove the lubricant; the temperature of the heating roller is 160-190°C, and the feeding speed is 2m / min; Step 7, longitudinal stretching: longitudinally stretching the degreased PTFE strip along the strip direction in a longitudinal stretching oven; The stretching ratio is 5 times, the stretching roller speed is 2~10m / min, the stretching roller temperature is 190~220℃, and the PTFE tape after longitudinal stretching: the tape thickness is 0.2~0.23mm, and the tape width is 170~190mm; Step eight, transverse stretching and high-temperature shaping: fix the two sides of the PTFE tape obtained in step seven by a cloth clip feeding belt, and perform transverse stretching and high-temperature shaping in a transverse stretching oven; the transverse stretching oven is a segmented oven with a total length of 38m, divided into 4 zones: ① preheating zone length 10m, temperature 120~160℃; ② transverse stretching zone 8m, temperature 180~250℃; ③ high-temperature shaping zone 16m, temperature 330~350℃; ④ cooling zone 4m, temperature 40~60℃; transverse stretching multiple is 5 times, and the stretching roller speed is 14m / min; in the transverse stretching zone, the top is equipped with a matrix medium-wave auxiliary heating unit with a temperature of 200~300℃, which is used to control the uniform stretching of the middle and edge of the film; The parameters of the ePTFE membrane after transverse stretching and high-temperature shaping are: membrane thickness 0.05~0.08mm, effective width of the material strip 1000~1100mm, membrane pore size 0.05um~0.1um, air permeability 400~600ml / min / cm2@7Kpa, water pressure resistance 500Kpa for 30min, test pore size 1.6mm; Step nine, post-lamination treatment: trim the ePTFE membrane obtained in step eight by 100 mm on both sides, laminate it with 1-3g silicone protective film, and press it with a double soft rubber roller press to make the ePTFE membrane thinner, thereby obtaining a waterproof ePTFE sound-permeable membrane that is resistant to 50 meters in depth.

2. The method for preparing a deep waterproof expanded polytetrafluoroethylene sound-permeable membrane according to claim 1, characterized in that: In the step 1, the polytetrafluoroethylene (PTFE) dispersion resin model is Japan Daikin F104, and the lubricant is isododecane (ISOPAR L); the weight ratio is: ISOPAR L: PTFE dispersion resin: 22%.

3. The method for preparing a deep waterproof expanded polytetrafluoroethylene sound-permeable membrane according to claim 1, characterized in that: The ePTFE membrane parameters are: membrane thickness 0.015~0.025mm, effective width of the material strip 700~800mm, membrane pore size 0.05um~0.1um, air permeability 300~500ml / min / cm2@7Kpa, water pressure resistance 500Kpa for 10min test pore size 1.6mm, sound transmission loss less than 2dB at 1KHz sound frequency, and less than 2dB in the entire band of 100Hz~10KHz.

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