CN107837693B - Preparation method of polytetrafluoroethylene super-hydrophobic membrane - Google Patents
Preparation method of polytetrafluoroethylene super-hydrophobic membrane Download PDFInfo
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- CN107837693B CN107837693B CN201710777931.6A CN201710777931A CN107837693B CN 107837693 B CN107837693 B CN 107837693B CN 201710777931 A CN201710777931 A CN 201710777931A CN 107837693 B CN107837693 B CN 107837693B
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- 229920001343 polytetrafluoroethylene Polymers 0.000 title claims abstract description 87
- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 87
- -1 polytetrafluoroethylene Polymers 0.000 title claims abstract description 84
- 239000012528 membrane Substances 0.000 title claims abstract description 75
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 230000003075 superhydrophobic effect Effects 0.000 title description 9
- 238000005245 sintering Methods 0.000 claims abstract description 56
- 239000000835 fiber Substances 0.000 claims abstract description 47
- 238000001816 cooling Methods 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 39
- 239000002243 precursor Substances 0.000 claims abstract description 22
- 238000009987 spinning Methods 0.000 claims abstract description 19
- 229920002125 Sokalan® Polymers 0.000 claims abstract description 18
- 239000004584 polyacrylic acid Substances 0.000 claims abstract description 18
- 239000012298 atmosphere Substances 0.000 claims abstract description 17
- 230000008569 process Effects 0.000 claims abstract description 16
- 239000000839 emulsion Substances 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000002904 solvent Substances 0.000 claims abstract description 6
- 238000004804 winding Methods 0.000 claims description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 12
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- 239000012510 hollow fiber Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 2
- 239000011259 mixed solution Substances 0.000 claims description 2
- 230000005661 hydrophobic surface Effects 0.000 abstract description 4
- 239000002352 surface water Substances 0.000 abstract description 2
- 239000011148 porous material Substances 0.000 description 12
- 230000002209 hydrophobic effect Effects 0.000 description 10
- 238000010041 electrostatic spinning Methods 0.000 description 9
- 238000004821 distillation Methods 0.000 description 8
- 230000004907 flux Effects 0.000 description 8
- 230000014759 maintenance of location Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 4
- 239000003570 air Substances 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- 238000001523 electrospinning Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000314 lubricant Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229920001410 Microfiber Polymers 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002121 nanofiber Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/364—Membrane distillation
-
- 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
-
- 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
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Water Supply & Treatment (AREA)
- Manufacturing & Machinery (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Artificial Filaments (AREA)
- Compositions Of Macromolecular Compounds (AREA)
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 polyacrylic acid, and the solvent is water; the sintering adopts program temperature control segmented continuous sintering, the temperature is increased from room temperature to 120-200 ℃ at the speed of 3-10 ℃/min under the flowing atmosphere, and the temperature is kept at 120-200 ℃ for 30-120 min; heating from 120-200 ℃ to 360-400 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 360-400 ℃ for 5-120 min; cooling treatment is carried out after sintering, the temperature of the cooling is reduced from 360 ℃ to 400 ℃ to 150 ℃ to 200 ℃ at the speed of 3-15 ℃/min in a flowing atmosphere, the temperature is preserved for 30-120 min at the temperature of 150-200 ℃, and then natural cooling is carried out; the thickness of the polytetrafluoroethylene film is 174 and 222 mu m. The beaded superfine fiber polytetrafluoroethylene membrane is prepared, and a hydrophobic surface with a multistage coarse structure is formed at one step; the surface water contact angle is more than or equal to 150 degrees, and the porosity is as high as more than 80 percent; the problem that the fiber is easy to collapse in the process of sintering the polytetrafluoroethylene precursor film is solved, the fiber is complete in shape and surface, the strength and toughness are greatly improved, and the polytetrafluoroethylene precursor film can bear certain vacuum pressure.
Description
The invention relates to a divisional application of the invention name 'a preparation method of a polytetrafluoroethylene super-hydrophobic membrane' with the application number of 201410163002.2 and the application date of 2014, 04 and 22.
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 and the cooling condition by a program temperature control method, and the special structure with the nanometer scale 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 polyacrylic acid, and the solvent is water; the sintering adopts program temperature control segmented continuous sintering, the temperature is increased from room temperature to 120-200 ℃ at the speed of 3-10 ℃/min under the flowing atmosphere, and the temperature is kept at 120-200 ℃ for 30-120 min; heating from 120-200 ℃ to 360-400 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 360-400 ℃ for 5-120 min; and cooling after sintering, wherein the cooling is carried out at a speed of 3-15 ℃/min from 360-400 ℃ to 150-200 ℃ in a flowing atmosphere, the temperature is kept at 150-200 ℃ for 30-120 min, and then natural cooling is carried out, wherein the thickness of the polytetrafluoroethylene film is 174 μm, 187 μm, 216 μm, 180 μm, 185 μm, 195 μm or 222 μm. 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 preparation method under the program control condition. 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 multistage 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. By controlling the cooling condition after sintering, micro cracks on the fiber are further reduced, a traceless fiber surface is formed, and the strength and the toughness of the fiber are enhanced.
The fiber manufacturing method comprises a preforming step after fiber manufacturing and before sintering, wherein the preforming step is to wind a polytetrafluoroethylene precursor film for 5-6 circles on a supporting die. The support membrane is cylindrical, and the diameter of the support membrane 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 polyacrylic acid aqueous solution is 0.5-30%, and the dry weight ratio of the polyacrylic acid to the polytetrafluoroethylene is 1: 1-50.
Specifically, the preparation method of the polytetrafluoroethylene membrane comprises the following steps:
(1) preparing a spinning solution; dissolving polyacrylic acid 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 polyacrylic acid 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 obtained 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, and sintering under the condition of continuously introducing flowing atmosphere; the sintering adopts program temperature control segmented continuous sintering, the temperature is increased from room temperature to 120-200 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 120-200 ℃ for 30-120 min; heating from 120-200 ℃ to 360-400 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 360-400 ℃ for 5-120 min;
(5) and (3) cooling: in a flowing atmosphere, the temperature is reduced from 360 ℃ to 400 ℃ to 150 ℃ to 200 ℃ at the speed of 3-15 ℃/min, the temperature is preserved for 30-120 min at the temperature of 150-200 ℃, and then the mixture is naturally cooled.
The flowing atmosphere is at least one of nitrogen, air or inert gas.
Advantageous effects
The polytetrafluoroethylene membrane with a unique structure is prepared by the invention, has a pore three-dimensional communicated structure formed by criss-cross beaded fiber yarns, and is a hydrophobic surface with a multistage rough structure formed in one step, and the beaded fiber yarns are fiber yarns formed by bonding mutual 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.
The invention solves the problem of easy collapse of fiber in the sintering of polytetrafluoroethylene precursor film, and obtains the beaded superfine fiber reticular film, the disordered stacking of the fiber is changed into mutual adhesion, the fiber shape and surface are intact, the strength and toughness are greatly improved, and the beaded superfine fiber reticular film can bear certain vacuum pressure (can be stably operated under the vacuum degree of 0.7 kPa).
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. The polytetrafluoroethylene porous membrane prepared by the invention does not need to be supported, has controllable thickness, is applied to the membrane distillation process, has the flux of more than 20L/m2 h, and has the retention rate of more than 99 percent.
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 polyacrylic acid 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 the mixture on a cylindrical support mold with the diameter of 5cm, winding 5 layers, conveying the mixture into a tubular furnace, introducing nitrogen, controlling the temperature program in the sintering process, raising the temperature from room temperature to 140 ℃ at a speed of 7 ℃/min, keeping the temperature at 140 ℃ for 80min, raising the temperature from 140 ℃ to 373 ℃ at a speed of 8 ℃/min, and keeping the temperature for 100min after the sintering temperature is reached, namely the temperature of a sintering section is 373 ℃.
And (3) cooling: cooling from 373 deg.C to 180 deg.C at a rate of 8 deg.C/min under flowing nitrogen atmosphere, maintaining at 180 deg.C for 80min, and naturally cooling.
After cooling, the membrane was taken out and the cylindrical support mold was removed to obtain a cylindrical polytetrafluoroethylene membrane having a thickness of 187. mu.m, which was then cut to obtain a flat porous membrane. The membrane has a hydrophobic contact angle of 170 degrees, a porosity of 87 percent, an average pore diameter of 0.5 mu m, a tensile strength of 488psi and an elongation of 375 percent, and when the membrane is used for membrane distillation operation, the flux is 26L/m2 & h, and the retention rate is 99.4 percent.
Example 2
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into polyacrylic acid aqueous solution with the mass fraction of 8%, and uniformly stirring to prepare 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 air, controlling the temperature by a program in the sintering process, raising the temperature from room temperature to 150 ℃ at a speed of 6 ℃/min, keeping the temperature at 150 ℃ for 70min, raising the temperature from 150 ℃ to 390 ℃ at a speed of 6 ℃/min, and keeping the temperature for 10min after the sintering temperature is reached, namely the temperature of a sintering section is 392 ℃.
And (3) cooling: cooling from 390 ℃ to 200 ℃ at the speed of 15 ℃/min under the flowing atmosphere of air, preserving the temperature for 30min at 200 ℃, and then naturally cooling.
And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 222um, and shearing to obtain the flat plate type porous membrane. The membrane had a hydrophobic contact angle of 165 °, a porosity of 84%, an average pore diameter of 0.4 μm, a tensile strength of 476psi, an elongation of 3150%, a flux of 22L/m2 · h and a rejection of 99.6% when used in membrane distillation operations.
Example 3
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyacrylic acid 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 the mixture on a cylindrical support die with the diameter of 5cm, winding 5 layers, conveying the mixture into a tubular furnace, introducing nitrogen, controlling the temperature by a program in the sintering process, raising the temperature from room temperature to 180 ℃ at a speed of 4 ℃/min, keeping the temperature at 180 ℃ for 40min, raising the temperature from 180 ℃ to 376 ℃, raising the temperature at a speed of 3 ℃/min, and keeping the temperature for 80min after reaching the sintering temperature, namely the sintering section temperature of 376 ℃.
And (3) cooling: cooling from 376 ℃ to 190 ℃ at the speed of 5 ℃/min under the flowing atmosphere of nitrogen, preserving the temperature for 40min at 190 ℃, and then naturally cooling.
And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 185um, and shearing to obtain the flat plate type porous membrane. The membrane has a hydrophobic contact angle of 164 degrees, a porosity of 84 percent, an average pore diameter of 0.30 mu m, a tensile strength of 470psi and an elongation of 325 percent, and when the membrane is used for membrane distillation operation, the flux is 25L/m2 & h, and the retention rate is 99.5 percent.
Example 4
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyacrylic acid 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 supporting die with the diameter of 5cm, winding 6 layers, conveying to a tube furnace, introducing argon, controlling the temperature by a program in the sintering process, raising the temperature from room temperature to 120 ℃ at a speed of 10 ℃/min, keeping the temperature at 120 ℃ for 120min, raising the temperature from 120 ℃ to 388 ℃ at a speed of 4 ℃/min, and keeping the temperature for 26min after reaching the sintering temperature, namely the sintering section temperature of 388 ℃.
And (3) cooling: cooling from 388 ℃ to 150 ℃ at the speed of 15 ℃/min under the flowing atmosphere of argon, preserving the temperature for 120min at 150 ℃, and then naturally cooling.
And taking out the membrane after cooling, drawing out the cylinder supporting die to obtain a cylindrical polytetrafluoroethylene membrane with the thickness of 216um, and shearing to obtain the flat plate type porous membrane. The membrane has a hydrophobic contact angle of 157 degrees, a porosity of 85 percent, an average pore diameter of 0.45 mu m, a tensile strength of 487psi and an elongation of 330 percent, and when the membrane is used for membrane distillation operation, the flux is 29L/m2 & h, and the retention rate is 99.2 percent.
Example 5
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyacrylic acid 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 the mixture on a cylindrical support die with the diameter of 0.5cm, winding 5 layers, conveying the mixture into a muffle furnace, introducing nitrogen, controlling the temperature by a program in the sintering process, heating the mixture from room temperature to 130 ℃ at a speed of 8 ℃/min, keeping the temperature at 130 ℃ for 100min, heating the mixture from 130 ℃ to 385 ℃ at a speed of 7 ℃/min, keeping the temperature for 35min after the sintering temperature is reached, namely the temperature of the sintering section is 385 ℃.
And (3) cooling: cooling from 385 ℃ to 160 ℃ at the speed of 12 ℃/min under the flowing atmosphere of nitrogen, preserving the temperature for 100min at 160 ℃, and then naturally cooling.
And taking out the tube support die after cooling to obtain the tube-type film with the thickness of 180 um. The membrane has a hydrophobic contact angle of 172 degrees, a porosity of 85 percent, an average pore diameter of 0.12 mu m, a tensile strength of 449psi and an elongation of 344 percent, and when the membrane is used for the distillation operation of a tubular membrane, the flux is 34L/m2 & h, and the retention rate is 99.6 percent.
Example 6
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into a polyacrylic acid 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 the mixture on a cylindrical support die with the diameter of 0.5cm, winding 5 layers, conveying the mixture into a tubular furnace, introducing argon, controlling the temperature by a program in the sintering process, raising the temperature from room temperature to 160 ℃ at a speed of 5 ℃/min, keeping the temperature at 160 ℃ for 100min, raising the temperature from 160 ℃ to 380 ℃ at a speed of 5 ℃/min, and keeping the temperature for 60min after the sintering temperature is reached, namely the temperature of a sintering section is 380 ℃.
And (3) cooling: cooling from 380 deg.C to 170 deg.C at a rate of 10 deg.C/min under flowing argon atmosphere, maintaining at 170 deg.C for 90min, and naturally cooling.
After cooling, the tube support mold is drawn out to obtain a tube film with a thickness of 195 um. The membrane has a hydrophobic contact angle of 165 degrees, a porosity of 85 percent, an average pore diameter of 0.35 mu m, a tensile strength of 470psi and an elongation of 325 percent, and when the membrane is used for the distillation operation of a tubular membrane, the flux is 38L/m2 & h, and the retention rate is 99.6 percent.
Example 7
And (3) dripping the polytetrafluoroethylene emulsion with the solid content of 60% into polyacrylic acid aqueous solution with the mass fraction of 3%, and uniformly stirring to prepare 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 tubular furnace, introducing nitrogen, controlling the temperature by a program in the sintering process, heating from room temperature to 200 ℃ at a heating speed of 3 ℃/min, keeping the temperature at 200 ℃ for 30min, heating from 200 ℃ to 385 ℃ at a heating speed of 2 ℃/min, and keeping the temperature for 120min after the sintering temperature is reached, namely the temperature of a sintering section is below 370 ℃.
And (3) cooling: cooling from 370 deg.C to 185 deg.C at a rate of 9 deg.C/min under flowing atmosphere of nitrogen, maintaining at 185 deg.C for 70min, and naturally cooling.
After cooling, the hollow fiber membrane is taken out and the cylinder supporting mold is drawn out, and the hollow fiber membrane with the thickness of 174um is obtained. The membrane has a hydrophobic contact angle of 175 degrees, a porosity of 85 percent, an average pore diameter of 0.45 mu m, a tensile strength of 465psi and an elongation of 365 percent, and when the membrane is used for the distillation operation of a hollow fiber membrane, the flux is 40L/m2 & h, and the retention rate is 99.9 percent.
Claims (6)
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 polyacrylic acid, and the solvent is water; the sintering adopts program temperature control segmented continuous sintering, the temperature is increased from room temperature to 120-200 ℃ at the speed of 3-10 ℃/min under the flowing atmosphere, and the temperature is kept at 120-200 ℃ for 30-120 min; heating from 120-200 ℃ to 360-400 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 360-400 ℃ for 5-120 min; cooling treatment is carried out after sintering, the temperature of the cooling is reduced from 360 ℃ to 400 ℃ to 150 ℃ to 200 ℃ at the speed of 3-15 ℃/min in a flowing atmosphere, the temperature is preserved for 30-120 min at the temperature of 150-200 ℃, and then natural cooling is carried out; the polytetrafluoroethylene film has a thickness of 174 μm, 187 μm, 216 μm, 180 μm, 185 μm, 195 μm or 222 μm.
2. The method of claim 1, further comprising a step of pre-forming the polytetrafluoroethylene membrane by winding the polytetrafluoroethylene membrane 5-6 times around a support mold after the fiber is formed and before sintering.
3. The process for producing a polytetrafluoroethylene membrane according to claim 2, wherein said support mold is cylindrical and has a diameter of 0.1cm, 0.5cm or 5 cm.
4. The method for producing a polytetrafluoroethylene membrane according to any one of claims 1 to 3, wherein the mass concentration of the aqueous solution of polyacrylic acid is 0.5% to 30%, and the dry weight ratio of polyacrylic acid to polytetrafluoroethylene is 1:1 to 50.
5. The method of preparing a polytetrafluoroethylene membrane according to claim 1 comprising the steps of:
(1) preparing a spinning solution: dissolving polyacrylic acid 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 polyacrylic acid 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 obtained polytetrafluoroethylene precursor membrane obtained in the step (2) on a supporting mould with a corresponding shape according to the 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 segmented continuous sintering, the temperature is increased from room temperature to 120-200 ℃ at the speed of 3-10 ℃/min, and the temperature is kept at 120-200 ℃ for 30-120 min; heating from 120-200 ℃ to 360-400 ℃ at the speed of 2-8 ℃/min, and preserving the heat at 360-400 ℃ for 5-120 min;
(5) and (3) cooling: in a flowing atmosphere, the temperature is reduced from 360 ℃ to 400 ℃ to 150 ℃ to 200 ℃ at the speed of 3-15 ℃/min, the temperature is preserved for 30-120 min at the temperature of 150-200 ℃, and then the mixture is naturally cooled.
6. 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 |
| CN102908911A (en) * | 2012-10-31 | 2013-02-06 | 辽宁省电力有限公司电力科学研究院 | Processing method of polytetrafluoroethylene microporous filtering material |
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| DE69017197T2 (en) * | 1990-05-18 | 1995-09-14 | Japan Gore Tex Inc | Hydrophilic porous membrane made of fluoropolymer. |
| CN101994161A (en) * | 2009-08-25 | 2011-03-30 | 东丽纤维研究所（中国）有限公司 | Method for preparing polytetrafluoroethylene superfine fiber |
| CN102205651B (en) * | 2010-12-24 | 2015-11-25 | 广东新志密封技术有限公司 | A kind of method of sintering polytetrafluoroethylene |
| JP5966282B2 (en) * | 2011-08-31 | 2016-08-10 | ダイキン工業株式会社 | Air filter media and air filter unit |
| CN103386256B (en) * | 2013-06-21 | 2015-03-25 | 浙江理工大学 | Method for preparing hollow fiber membranes and tubular membranes with microporous PTFE hybrid flat membrane wrapping method |
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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 |
| CN102908911A (en) * | 2012-10-31 | 2013-02-06 | 辽宁省电力有限公司电力科学研究院 | Processing method of polytetrafluoroethylene microporous filtering material |
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| 热处理对PTFE牵伸性能的影响;郭占军等;《纺织学报》;20100630;第31卷(第6期);21-24 * |
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| CN105013347B (en) | 2017-08-08 |
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