CN107837691B - Preparation method of super-hydrophobic polytetrafluoroethylene membrane - Google Patents
Preparation method of super-hydrophobic polytetrafluoroethylene membrane Download PDFInfo
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- CN107837691B CN107837691B CN201710777909.1A CN201710777909A CN107837691B CN 107837691 B CN107837691 B CN 107837691B CN 201710777909 A CN201710777909 A CN 201710777909A CN 107837691 B CN107837691 B CN 107837691B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/36—Polytetrafluoroethene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0004—Organic membrane manufacture by agglomeration of particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/04—Tubular membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/06—Flat membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/39—Electrospinning
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/38—Hydrophobic membranes
Abstract
The invention provides a preparation method of a polytetrafluoroethylene membrane, which comprises the steps of preparing spinning solution, preparing fiber and sintering, and is characterized in that: preparing a fiber-forming carrier and a solvent into a solution, and then adding polytetrafluoroethylene emulsion, wherein the fiber-forming carrier is polyvinyl alcohol, and the solvent is water; the sintering adopts program temperature control segmented continuous sintering, the temperature is kept at 90-120 ℃ for 30-120 min under the flowing atmosphere, the temperature is increased from 90-120 ℃ to 260-300 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 260-300 ℃ for 30-120 min; heating from 260-300 ℃ to 370-390 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 370-390 ℃ for 5-120 min; the thickness of the polytetrafluoroethylene is 156-215 mu m. The invention excellently solves the problem that the fiber is easy to collapse in the sintering of the polytetrafluoroethylene precursor film, and obtains the beaded superfine fiber reticular film, the fibers are changed from disordered stacking to mutual adhesion, the fiber shape is uniform, the surface is intact, the strength and the toughness are also greatly improved, and the beaded superfine fiber reticular film can bear certain vacuum pressure.
Description
The invention relates to a divisional application of application number 201410163139.8, application date 2014, 04-22 and invention name 'a preparation method of a super-hydrophobic polytetrafluoroethylene membrane'.
Technical Field
The invention relates to a preparation method of a separation membrane material in the separation field, in particular to a preparation method of a hydrophobic membrane material.
Technical Field
Hydrophobicity is an important property of Polytetrafluoroethylene (PTFE) materials, and is the primary property of PTFE porous membranes for use in membrane materials. Although polytetrafluoroethylene materials have a low surface energy, the water contact angle of a smooth polytetrafluoroethylene plane is between 98 and 112 °, and the hydrophobic properties are not good.
At present, a biaxial stretching method is mostly adopted for preparing the polytetrafluoroethylene porous membrane. When the method is used for obtaining a film with higher porosity, the film needs to be stretched in a large proportion, the surface structure cannot be controlled, the film thickness is only below ten microns, a supporting material is needed in use, and the supporting material has certain limitation on heat resistance, chemical stability or hydrophobic property, so that the application of the biaxially oriented film is limited. Meanwhile, high-proportion stretching tends to make it difficult to control the shape of the membrane, and therefore flat sheet membranes are mainly used. The patents of Chinese patents CN1775847A, CN102007242A, CN101543734B, CN102151494A and the like all carry out the preparation of the polytetrafluoroethylene porous membrane based on the biaxial stretching process.
The carrier method is an important method for preparing polytetrafluoroethylene fibers, and patents such as CN101994161A and CN102282301A report the preparation of polytetrafluoroethylene ultrafine fibers by adopting an electrostatic spinning technology. These reports all involve the step of high temperature sintering to remove the fiberizing carrier, but these sintering processes are focused only on the removal of the fiberizing template. Specifically, the method comprises the following steps: CN101994161A aims to prepare a polytetrafluoroethylene superfine fiber, the preparation method is that polyvinyl alcohol is used as a carrier, a polytetrafluoroethylene fiber precursor is spun by an electrostatic spinning method, and the post-treatment method is that the polytetrafluoroethylene fiber precursor is dried for 5-15 minutes at 100-120 ℃, and then sintered for 30-90 minutes at 280-350 ℃; the purpose of sintering is to decompose and remove the polyvinyl alcohol. CN102282301A mainly provides an improved method for polytetrafluoroethylene mat, which aims to improve the electrospinning process parameters (viscosity of spinning solution) to obtain a uniform-diameter polytetrafluoroethylene fiber mat precursor, and then sintering at 400 ℃ to obtain a polytetrafluoroethylene fiber mat, wherein ash content of the carrier (fiber-forming polymer) is less than 5%. The patents CN101994161A and CN102282301A adopt the electrospinning technology to obtain the polytetrafluoroethylene superfine fiber (mat) only in consideration of how to obtain the polytetrafluoroethylene superfine fiber (mat), so it can be said that only the conventional polytetrafluoroethylene superfine fiber (mat) is obtained.
Disclosure of Invention
The invention aims to provide a preparation method of a polytetrafluoroethylene membrane, which is characterized in that a superfine fiber mesh membrane with a complete fiber shape and a beaded structure is obtained by controlling the post-treatment sintering condition of a polytetrafluoroethylene precursor membrane containing a fiber-forming carrier and precisely controlling the sintering condition by a program temperature control method, and the special structure with the nanoscale and the superfine fiber form a hydrophobic surface with a multistage coarse structure. Thus having superhydrophobic properties.
The purpose of the invention is realized by the following technical measures:
a preparation method of a polytetrafluoroethylene membrane comprises the steps of preparing spinning solution, preparing fiber and sintering, and is characterized in that: preparing a fiber-forming carrier and a solvent into a solution, and then adding polytetrafluoroethylene emulsion, wherein the fiber-forming carrier is polyvinyl alcohol, and the solvent is water; the sintering adopts the step of temperature controlled sequential sintering, the temperature is kept at 90-120 ℃ for 30-120 min under the flowing atmosphere, the temperature is increased from 90-120 ℃ to 260-300 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 260-300 ℃ for 30-120 min; heating the polytetrafluoroethylene to 370-390 ℃ from 260-300 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 370-390 ℃ for 5-120 min, wherein the thickness of the polytetrafluoroethylene is 156 mu m, 165 mu m, 168 mu m, 215 mu m or 209 mu m. By controlling the post-treatment sintering condition of the polytetrafluoroethylene precursor film containing the fiber-forming carrier, under the action of stress and the protection of the carrier, the polytetrafluoroethylene particles begin to be reoriented and arranged, then the carrier is decomposed at a proper time, and the polytetrafluoroethylene particles are further oriented and rearranged to form a beaded superfine fiber net structure. The super-hydrophobic polytetrafluoroethylene fiber membrane with a special structure can be prepared by adopting the program control conditions. If the membrane is not sintered for 30-90 minutes at the temperature of 280-350 ℃ as described in CN101994161A under the program control condition of the invention, the super-hydrophobic polytetrafluoroethylene fiber membrane with multi-level roughness and the water contact angle of more than 150 ℃ cannot be obtained, and the membrane has no flexibility. In addition, if the procedure control is not adopted (for example, CN102282301A is sintered at 400 ℃ to obtain the polytetrafluoroethylene fiber mat, and the ash content of the carrier (fiber-forming polymer) is less than 5 percent), the original shape of the fiber cannot be maintained, so that the fiber collapses to be flat.
Preferably, the sintering adopts program temperature control segmented continuous sintering, the temperature is increased from room temperature to 90-120 ℃ at the speed of 2-15 ℃/min under the flowing atmosphere, the temperature is maintained at 90-120 ℃ for 50-100 min, the temperature is increased from 100-120 ℃ to 280-300 ℃ at the speed of 5-8 ℃/min, and the temperature is maintained at 280-300 ℃ for 60-120 min; heating from 280-300 ℃ to 380-390 ℃ at the speed of 4-7 ℃/min, and preserving the heat for 30-80 min at 380-390 ℃.
The preforming is to wind the polytetrafluoroethylene precursor film for 5-6 circles on the supporting die. The supporting die is cylindrical, and the diameter of the supporting die is 0.1cm, 0.5cm or 5 cm. The winding of the fibers superimposes a stress orientation that facilitates the sintering process.
The mass concentration of the polyvinyl alcohol aqueous solution is 0.5-30%, and the dry weight ratio of polyvinyl alcohol to polytetrafluoroethylene is 1: 1-50.
Specifically, the preparation method of the polytetrafluoroethylene membrane comprises the following steps:
(1) preparing a spinning solution; dissolving polyvinyl alcohol in water to prepare a uniform solution with the concentration of 0.5-30% by mass, and then stirring and adding polytetrafluoroethylene emulsion to obtain a uniform mixed solution; the dry weight ratio of the polyvinyl alcohol to the polytetrafluoroethylene is 1: 1-50;
(2) preparing fibers; spinning the spinning solution prepared in the step (1) by adopting a spinning or stretching method to prepare fibers to obtain a polytetrafluoroethylene precursor film;
(3) preforming: winding the polytetrafluoroethylene precursor membrane obtained in the step (2) on a support mould with a corresponding shape according to an expected use specification to form membranes with different shapes and specifications such as a flat plate type, a tubular type, a hollow fiber type or a roll type, and controlling the membrane thickness through the number of winding layers;
(4) sintering; putting the preformed polytetrafluoroethylene precursor film obtained in the step (3) and a supporting mold into a high-temperature furnace for sintering under the condition of continuously introducing atmosphere; the sintering adopts program temperature control segmented continuous sintering, the temperature is kept at 90-120 ℃ for 30-120 min under inert flowing atmosphere, the temperature is raised from 90-120 ℃ to 260-300 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 260-300 ℃ for 30-120 min; heating from 260-300 ℃ to 370-390 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 370-390 ℃ for 5-120 min.
The flowing atmosphere is at least one of nitrogen, air or inert gas.
Advantageous effects
1. The polytetrafluoroethylene membrane with a unique structure is prepared, has a pore three-dimensional communication structure formed by criss-cross beading fiber yarns, and is a hydrophobic surface with a multistage rough structure formed in one step, wherein the beading fiber yarns are formed by bonding mutually points and/or surfaces among polytetrafluoroethylene particles; the pores are of a labyrinth diameter, the maximum pore diameter is 1.0 mu m, the minimum pore diameter is 0.01 mu m, and the average pore diameter is 0.1-0.5 mu m; the fiber filaments are nanofibers with an average diameter of 500 +/-50 nm.
2. The invention excellently solves the problem that the fiber is easy to collapse in the sintering of the polytetrafluoroethylene precursor film, and obtains the beaded superfine fiber reticular film, the disordered stacking of the fibers is changed into mutual adhesion, the fiber shape is uniform, the surface is intact, the strength and the toughness are also greatly improved, and the beaded superfine fiber reticular film can bear certain vacuum pressure (can still stably operate under the vacuum degree of 0.7 kPa).
3. The polytetrafluoroethylene porous membrane prepared by the invention has a special super-hydrophobic structure, a large number of rough surfaces are formed on the surface of the obtained PTFE fiber, the surface water contact angle is more than or equal to 150 degrees, and the porosity is as high as more than 80 percent.
4. Poly (tetra) s prepared by the inventionThe fluoroethylene porous membrane does not need to be supported, has controllable thickness, is applied to the membrane distillation process, and has the flux more than or equal to 26L/m2H, the retention rate is more than 99%.
5. The invention provides a pre-forming of the winding process before sintering, which can control the shape and thickness of the final product film, and provides the thickness and strength required by the film while ensuring high porosity (more than 80%). Compared with a biaxial stretching process for obtaining high porosity and high-proportion stretching, the polytetrafluoroethylene membrane obtained by the method disclosed by the invention does not need to be supported, and has various forms and controllable thickness.
6. The preparation method of the polytetrafluoroethylene super-hydrophobic membrane provided by the invention adopts the sintering condition control step to decompose the carrier at a proper time, and the polytetrafluoroethylene particles are subjected to melt orientation rearrangement to obtain the beaded superfine fiber mesh membrane, and the special structure with the nanoscale and the superfine fibers form a hydrophobic surface with a multistage coarse structure. Thus having superhydrophobic properties.
7. The invention avoids the use of lubricant in biaxial tension, has no problem of removing the lubricant, has simple process, does not need extrusion, film pressing and other complex flows, and has little pollution.
Detailed Description
The present invention is described in detail below by way of examples, it should be noted that the examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and those skilled in the art can make modifications and adjustments without essential to the present invention.
Example 1
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 15%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical supporting mold with a diameter of 5cm, winding 5 layers, introducing nitrogen into a tube furnace, controlling the temperature program in the sintering process, heating from room temperature to 110 ℃ at a speed of 10 ℃/min, keeping the temperature at 110 ℃ for 90min, heating from 110 ℃ to 290 ℃ at a heating speed of 7 ℃/min, keeping the temperature at 290 ℃ for 100min, and heating from 290 ℃ to 100minHeating to 380 deg.C at a temperature rise rate of 6 deg.C/min, and maintaining for 60 min. After cooling, taking out the membrane, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 156 mu m, and shearing to obtain the flat plate type porous membrane. The membrane has a hydrophobic contact angle of 173 degrees, a porosity of 88 percent, an average pore diameter of 0.4 mu m, a tensile strength of 495psi and an elongation of 370 percent, and when the membrane is used for membrane distillation operation, the flux is 40L/m2H, retention 99.7%.
Example 2
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 8%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical support die with the diameter of 5cm, winding 5 layers, conveying to a tubular furnace, introducing nitrogen, controlling the temperature by a program in the sintering process, heating from room temperature to 90 ℃ at the speed of 2 ℃/min, keeping the temperature at 90 ℃ for 120min, heating from 90 ℃ to 260 ℃ at the speed of 10 ℃/min, keeping the temperature at 260 ℃ for 120min, heating from 260 ℃ to 375 ℃, heating at the speed of 8 ℃/min, and keeping the temperature for 115 min. And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 165um, and shearing to obtain the flat plate type porous membrane. The membrane has a hydrophobic contact angle of 158 degrees, a porosity of 82 percent, an average pore diameter of 0.45 mu m, a tensile strength of 445psi and an elongation of 310 percent, and has a flux of 26L/m when used for membrane distillation operation2H, retention 99.3%.
Example 3
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 6%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical support die with the diameter of 5cm, winding 5 layers, conveying to a tubular furnace, introducing nitrogen, controlling the temperature program in the sintering process, heating from room temperature to 100 ℃ at the speed of 5 ℃/min, keeping the temperature at 100 ℃ for 110min, heating from 100 ℃ to 275 ℃ at the speed of 10 ℃/min, keeping the temperature at 275 ℃ for 110min, heating from 275 ℃ to 380 ℃ at the speed of 3 ℃/min, and keeping the temperature for 90 min. And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 168um, and shearing to obtain the flat plate type porous membrane. The hydrophobic contact angle of the membrane is 165 degrees, the porosity is 81 percent, the average pore diameter is 0.20 mu m, and the tensile strength is strongDegree 460psi, elongation 320%, flux 29L/m for membrane distillation operation2H, retention 99.5%.
Example 4
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 5%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical support die with the diameter of 5cm, winding 6 layers, sending the cylindrical support die into a tubular furnace, introducing air, controlling the temperature by a program in the sintering process, heating from room temperature to 100 ℃ at 8 ℃/min, keeping the temperature at 100 ℃ for 100min, heating from 100 ℃ to 280 ℃ at the heating speed of 8 ℃/min, keeping the temperature at 280 ℃ for 120min, heating from 280 ℃ to 385 ℃, heating at the heating speed of 4 ℃/min, and keeping the temperature for 80 min. And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 215um, and shearing to obtain the flat plate type porous membrane. The membrane has a hydrophobic contact angle of 168 degrees, a porosity of 85 percent, an average pore diameter of 0.40 mu m, a tensile strength of 475psi and an elongation of 325 percent, and when the membrane is used for membrane distillation operation, the flux is 31L/m2H, retention 99.3%.
Example 5
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 10%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical supporting die with the diameter of 0.5cm, winding 5 layers, conveying to a muffle furnace, introducing nitrogen, controlling the temperature by a program in the sintering process, heating from room temperature to 120 ℃ at a speed of 15 ℃/min, preserving heat at 120 ℃ for 30min, heating from 120 ℃ to 295 ℃ at a heating speed of 3 ℃/min, preserving heat at 295 ℃ for 120min, heating from 295 ℃ to 390 ℃ at a heating speed of 2 ℃/min, and preserving heat for 10 min. And taking out the tube support die after cooling to obtain the tube-type film with the thickness of 165 um. The membrane has a hydrophobic contact angle of 170 degrees, a porosity of 84 percent, an average pore diameter of 0.5 mu m, a tensile strength of 436psi and an elongation of 355 percent, and when the membrane is used for tubular membrane distillation operation, the flux is 35L/m2H, retention 99.6%.
Example 6
Dripping 60 percent of polytetrafluoroethylene emulsion into 6 percent of polyvinyl alcohol aqueous solution by mass percent, and uniformly stirring to prepare spinningAnd (4) liquid. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical supporting die with the diameter of 0.5cm, winding 5 layers, conveying to a tubular furnace, introducing argon, controlling the temperature by a program in the sintering process, heating from room temperature to 115 ℃ at the speed of 12 ℃/min, keeping the temperature at 115 ℃ for 50min, heating from 115 ℃ to 300 ℃ at the speed of 5 ℃/min, keeping the temperature at 300 ℃ for 60min, heating from 300 ℃ to 390 ℃ at the speed of 6 ℃/min, and keeping the temperature for 30 min. And taking out the tube support die after cooling to obtain a tube-type film with the thickness of 168 um. The membrane has a hydrophobic contact angle of 172 degrees, a porosity of 87 percent, an average pore diameter of 0.35 mu m, a tensile strength of 475psi and an elongation of 355 percent, and when the membrane is used for tubular membrane distillation operation, the flux is 37L/m2H, retention 99.6%.
Example 7
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyvinyl alcohol aqueous solution with the mass fraction of 3%, and uniformly stirring to prepare the spinning solution. Then preparing the polytetrafluoroethylene precursor film by adopting an electrostatic spinning method. Winding on a cylindrical supporting die with the diameter of 0.1cm, winding 6 layers, conveying to a tube furnace, introducing air, controlling the temperature by a program in the sintering process, heating from room temperature to 110 ℃ at 9 ℃/min, keeping the temperature at 110 ℃ for 80min, heating from 110 ℃ to 285 ℃ at the heating speed of 6 ℃/min, keeping the temperature at 285 ℃ for 70min, heating from 285 ℃ to 380 ℃ at the heating speed of 5 ℃/min, and keeping the temperature for 60 min. And taking out the hollow fiber membrane after cooling, and drawing out the cylinder supporting mold to obtain the hollow fiber membrane with the thickness of 209 um. The membrane has a hydrophobic contact angle of 174 degrees, a porosity of 86 percent, an average pore diameter of 0.4 mu m, a tensile strength of 490psi and an elongation of 365 percent, and when the membrane is used for the distillation operation of a hollow fiber membrane, the flux is 42L/m2H, retention 99.7%.
Claims (7)
1. A preparation method of a polytetrafluoroethylene membrane comprises the steps of preparing spinning solution, preparing fiber and sintering, and is characterized in that: preparing a fiber-forming carrier and a solvent into a solution, and then adding polytetrafluoroethylene emulsion, wherein the fiber-forming carrier is polyvinyl alcohol, and the solvent is water; the sintering adopts program temperature control segmented continuous sintering, the temperature is kept at 90-120 ℃ for 30-120 min under the flowing atmosphere, the temperature is increased from 90-120 ℃ to 260-300 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 260-300 ℃ for 30-120 min; heating from 260-300 ℃ to 370-390 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 370-390 ℃ for 5-120 min; the polytetrafluoroethylene has a thickness of 156 μm, 165 μm, 168 μm, 215 μm or 209 μm.
2. The method for preparing a polytetrafluoroethylene membrane according to claim 1, wherein the sintering is a programmed temperature control step-by-step continuous sintering, the temperature is raised from room temperature to 90-120 ℃ at a rate of 2-15 ℃/min under a flowing atmosphere, the temperature is maintained at 90-120 ℃ for 50-100 min, the temperature is raised from 100-120 ℃ to 280-300 ℃ at a rate of 5-8 ℃/min, and the temperature is maintained at 280-300 ℃ for 60-120 min; heating from 280-300 ℃ to 380-390 ℃ at the speed of 4-7 ℃/min, and preserving the heat for 30-80 min at 380-390 ℃.
3. The method for preparing a polytetrafluoroethylene film according to claim 1 or 2, comprising a step of preforming, after the fiber is made, before sintering, by winding a polytetrafluoroethylene precursor film around a support mold.
4. The method of producing a polytetrafluoroethylene membrane according to claim 3 wherein said support mold is cylindrical and has a diameter of 0.1cm, 0.5cm or 5 cm.
5. The method for preparing a polytetrafluoroethylene membrane according to claim 1, wherein the mass concentration of the aqueous solution of polyvinyl alcohol is 0.5-30%, and the dry weight ratio of polyvinyl alcohol to polytetrafluoroethylene is 1: 1-50.
6. The method of preparing a polytetrafluoroethylene membrane according to claim 1 comprising the steps of:
(1) preparing a spinning solution: dissolving polyvinyl alcohol in water to prepare a uniform solution with the concentration of 0.5-30% by mass, and then stirring and adding polytetrafluoroethylene emulsion to obtain a uniform mixed solution; the dry weight ratio of the polyvinyl alcohol to the polytetrafluoroethylene is 1: 1-50;
(2) preparing fibers: spinning the spinning solution prepared in the step (1) by a spinning method to prepare fibers to obtain a polytetrafluoroethylene precursor film;
(3) preforming: winding the polytetrafluoroethylene precursor membrane obtained in the step (2) on a supporting mould with a corresponding shape according to an expected use specification to form a flat plate type, a tubular type, a hollow fiber type or a roll type shape;
(4) and (3) sintering: putting the preformed polytetrafluoroethylene precursor film obtained in the step (3) and a supporting mold into a high-temperature furnace, and sintering under the condition of continuously introducing flowing atmosphere; the sintering adopts program temperature control and sectional continuous sintering, the temperature is kept at 90-120 ℃ for 30-120 min, the temperature is increased from 90-120 ℃ to 260-300 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 260-300 ℃ for 30-120 min; heating from 260-300 ℃ to 370-390 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 370-390 ℃ for 5-120 min.
7. The method of claim 1, wherein the flowing atmosphere is at least one of nitrogen, air, or an inert gas.
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| CN101530750A (en) * | 2009-04-20 | 2009-09-16 | 浙江理工大学 | Preparation method of polytetrafluoroethylene superfine fiber porous membrane |
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| CN101607178A (en) * | 2009-06-16 | 2009-12-23 | 天津工业大学 | A kind of preparation method of doughnut perforated membrane |
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| CN104998558B (en) | 2017-08-08 |
| CN107837691A (en) | 2018-03-27 |
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