Perfluoropolymer hollow fiber composite membrane preparation method

Abstract

A perfluoropolymer hollow fiber composite membrane preparation method includes the steps of (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, (B) preparing a membrane casting solution, which includes obtaining a mixed solution by mixing a perfluoropolymer water dispersion emulsion, a spinning carrier and solvent, and defoaming the mixed solution at vacuum and a constant temperature, (C) preparing a nascent hollow fiber composite membrane, which includes compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a coagulant, solidifying and forming, and (D) drying after putting the nascent hollow fiber composite membrane to a hot air box, cleaning, sintering, and performing heat preservation. The prepared membrane has a thin wall, thermal and chemical resistance and good mechanical performance.

Claims

1. A perfluoropolymer hollow fiber composite membrane preparation method comprising the steps of: (A) preparing a supporting layer of a perfluoropolymer hollow fiber composite membrane; (B) preparing a membrane casting solution, which comprises obtaining a mixed solution by mixing a perfluoropolymer water dispersion emulsion, a spinning carrier and solvent at a temperature in a range of 60−90° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the perfluoropolymer water dispersion emulsion in the mixed solution is in a range of 10-40 wt. %, a proportion of the spinning carrier in the mixed solution is in a range of 5-20 wt. %, and a proportion of the solvent in the mixed solution is in a range of 40-85 wt. %; (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature in a range of 60−90° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a coagulant, solidifying and forming, so that the nascent hollow fiber composite membrane is obtained; and (D) drying for 10-30 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature in a range of 40−80° C., removing residual coagulant by immersing the dried nascent hollow fiber composite membrane into deionized water, putting the dried nascent hollow fiber composite membrane without the residual coagulant into a heat treatment device, heating to 200-400° C. at a heating rate in a range of 5-20° C./min, sintering, and performing heat preservation for 0.5-5 h, so that the perfluoropolymer hollow fiber composite membrane, comprising the supporting layer and a surface separation layer coated on the supporting layer, is obtained, wherein the perfluoropolymer is at least one member selected from a group consisting of thermoplastic polyperfluoroethylene propylene (FEP) and thermoplastic tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA).

2. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein a content of the perfluoropolymer in the perfluoropolymer water dispersion emulsion is in a range of 30-70 wt. %.

3. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein fiber filaments for preparing the supporting layer are acid and alkali resistant glass fiber filaments, basalt fiber filaments, aromatic polyamide fiber filaments or polyimide fiber filaments; the step (A) comprises weaving the fiber filaments into fiber braided tube through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane.

4. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the spinning carrier is a polyvinyl alcohol aqueous solution with a concentration in a range of 4-10 wt. %, a carboxymethyl cellulose aqueous solution with a concentration in a range of 4-10 wt. %, or a mixture of cellulose with a proportion in a range of 4-10 wt. % in the mixture and an N-methylmorpholine-N-oxide aqueous solution with a proportion in a range of 90-96 wt. % in the mixture, wherein the N-methylmorpholine-N-oxide aqueous solution comprises 87 wt. % of N-methylmorpholine-N-oxide and 13 wt. % of water.

5. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the solvent is deionized water or N-methylmorpholine-N-oxide aqueous solution, wherein N-methylmorpholine-N-oxide aqueous solution comprises 87 wt. % of N-methylmorpholine-N-oxide and 13 wt. % of water.

6. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the coagulant is an inorganic salt saturated aqueous solution which is one or two members selected from a group consisting of a sodium sulfate saturated aqueous solution, a potassium sulfate saturated aqueous solution, and an ammonium sulfate saturated aqueous solution; or the coagulant is anhydrous ethanol, anhydrous methanol or deionized water.

7. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the surface separation layer has a thickness in a range of 10-100 μm, and an outer diameter of the supporting layer is in a range of 500-2000 μm.

8. The perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the heat treatment device is an intermittent hot box treatment device, a continuous hot roll treatment device or a continuous hot plate treatment device.

9. A perfluoropolymer hollow fiber composite membrane prepared by the perfluoropolymer hollow fiber composite membrane preparation method according to claim 1, wherein the membrane has an oil flux in a range of 200-1300 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar and an organic solvent flux in a range of 300-1500 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar, the oil is kerosene, diesel, gasoline, benzene or halogenated alkanes; the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or N-methylpyrrolidone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a cross-sectional schematic diagram of a perfluoropolymer hollow fiber composite membrane provided by the present invention.

[0029] FIG. 2 is aouter surface SEM images of the perfluoropolymer hollow fiber composite membrane prepared by the method according to the first embodiment of the present invention.

[0030] FIG. 3 is across-sectional SEM images of the perfluoropolymer hollow fiber composite membrane in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031] The technical solutions of the present invention will be described in detail in combination with embodiments as follows. The specific embodiments are only used to further specify the present invention without limiting the protection scope of the claims of the present application.

[0032] In the following embodiments, a concentration of a polyvinyl alcohol aqueous solution is in a range of 4-10 wt. %.

First Embodiment

[0033] A perfluoropolymer hollow fiber composite membrane preparation method comprises the steps of: [0034] (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, which comprises weaving polyparaphenylene terephthalamide fiber filaments into fiber braided tube with an outer diameter of 800 μm through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube at 300° C. for 5 min to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane; [0035] (B) preparing a membrane casting solution as a functional layer, which comprises obtaining a mixed solution by mixing a polyperfluoroethylene propylene water dispersion emulsion with a concentration of 40 wt. %, a polyvinyl alcohol aqueous solution and a first amount of deionized water at 80° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the polyperfluoroethylene propylene water dispersion emulsion in the mixed solution is 18 wt. %, a proportion of the polyvinyl alcohol aqueous solution in the mixed solution is 7 wt. %, and a proportion of the first amount of deionized water in the mixed solution is 75 wt. %; [0036] (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature of 60° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a saturated sodium sulfate aqueous solution with a concentration of 49 wt. % and a temperature of 40° C. as coagulating bath, and forming, so that the nascent hollow fiber composite membrane is obtained; and [0037] (D) drying for 10 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature of 70° C., removing residual sodium sulfate by immersing the dried nascent hollow fiber composite membrane into a second amount of deionized water, putting the dried nascent hollow fiber composite membrane without the residual sodium sulfate into a multi-roll heat treatment device, heating to 230° C. at a heating rate of 5° C./min, sintering, and performing heat preservation for 5 h, so that the perfluoropolymer hollow fiber composite membrane is obtained.

[0038] The perfluoropolymer hollow fiber composite membrane prepared by the aforementioned method has a surface separation layer with a thickness of 90 μm. After being continuously tested for 1 h under an operating pressure of 0.02 MPa, the perfluoropolymer hollow fiber composite membrane has a kerosene flux of 300 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar and an N,N-dimethylacetamide flux of 550 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar.

Second Embodiment

[0039] A perfluoropolymer hollow fiber composite membrane preparation method comprises the steps of: [0040] (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, which comprises weaving glass fiber filaments into fiber braided tube with an outer diameter of 1000 μm through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube at 250° C. for 5 min to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane; [0041] (B) preparing a membrane casting solution as a functional layer, which comprises obtaining a mixed solution by mixing a polyperfluoroethylene propylene water dispersion emulsion with a concentration of 60 wt. %, a polyvinyl alcohol aqueous solution and a first amount of deionized water at 90° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the polyperfluoroethylene propylene water dispersion emulsion in the mixed solution is 23 wt. %, a proportion of the polyvinyl alcohol aqueous solution in the mixed solution is 3 wt. %, and a proportion of the first amount of deionized water in the mixed solution is 74%; [0042] (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature of 70° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into an absolute ethanol with a temperature of 25° C., solidifying and forming, so that the nascent hollow fiber composite membrane is obtained; and [0043] (D) drying for 10 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature of 60° C., removing residual ethanol by immersing the dried nascent hollow fiber composite membrane into a second amount of deionized water, putting the dried nascent hollow fiber composite membrane without the residual ethanol into a multi-roll heat treatment device, heating to 250° C. at a heating rate of 10° C./min, sintering, and performing heat preservation for 3 h, so that the perfluoropolymer hollow fiber composite membrane is obtained.

[0044] The perfluoropolymer hollow fiber composite membrane prepared by the above method has a surface separation layer with a thickness of 70 After being continuously tested for 1 h under an operating pressure of 0.02 MPa, the perfluoropolymer hollow fiber composite membrane has a kerosene flux of 600 L.Math.m.sup.−2.Math..sup.−1.Math.bar and an N-methylpyrrolidine flux of 900 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar.

Third Embodiment

[0045] A perfluoropolymer hollow fiber composite membrane preparation method comprises the steps of: [0046] (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, which comprises weaving polyparaphenylene terephthalamide fiber filaments into fiber braided tube with an outer diameter of 1200 μm through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube at 300° C. for 5 min to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane; [0047] (B) preparing a membrane casting solution as a functional layer, which comprises obtaining a mixed solution by mixing a polyperfluoroethylene propylene water dispersion emulsion with a concentration of 50 wt. %, a polyvinyl alcohol aqueous solution and a first amount of deionized water at 80° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the polyperfluoroethylene propylene water dispersion emulsion in the mixed solution is 25 wt. %, a proportion of the polyvinyl alcohol aqueous solution in the mixed solution is 5 wt. %, and a proportion of the first amount of deionized water in the mixed solution is 70%; [0048] (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature of 70° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a saturated potassium sulfate aqueous solution with a concentration of 9 wt. % and a temperature of 35° C. as coagulating bath, and forming, so that the nascent hollow fiber composite membrane is obtained; and [0049] (D) drying for 10 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature of 75° C., removing residual potassium sulfate by immersing the dried nascent hollow fiber composite membrane into a second amount of deionized water, putting the dried nascent hollow fiber composite membrane without the residual potassium sulfate into a multi-roll heat treatment device, heating to 270° C. at a heating rate of 15° C./min, sintering, and performing heat preservation for 1.5 h, so that the perfluoropolymer hollow fiber composite membrane is obtained.

[0050] The perfluoropolymer hollow fiber composite membrane prepared by the above method has a surface separation layer with a thickness of 50 After being continuously tested for 1 h under an operating pressure of 0.02 MPa, the perfluoropolymer hollow fiber composite membrane has a kerosene flux of 900 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar and an N,N-dimethylformamide flux of 1100 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar.

Fourth Embodiment

[0051] A perfluoropolymer hollow fiber composite membrane preparation method comprises the steps of: [0052] (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, which comprises weaving polymetaphenylene isophthalamide fiber filaments into fiber braided tube with an outer diameter of 1300 μm through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube at 200° C. for 5 min to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane; [0053] (B) preparing a membrane casting solution as a functional layer, which comprises obtaining a mixed solution by mixing a water dispersion emulsion of tetrafluoroethylene-perfluoropropyl vinyl ether copolymer with a concentration of 60 wt. %, acarboxymethyl cellulose aqueous solution and a first amount of deionized water at 75° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the water dispersion emulsion of tetrafluoroethylene-perfluoropropyl vinyl ether copolymer in the mixed solution is 22 wt. %, a proportion of the carboxymethyl cellulose aqueous solution in the mixed solution is 6 wt. %, and a proportion of the first amount of deionized water in the mixed solution is 72 wt. %; [0054] (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature of 70° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a saturated ammonium sulfate aqueous solution with a concentration of 44 wt. % and a temperature of 30° C. as coagulating bath, and forming, so that the nascent hollow fiber composite membrane is obtained; and [0055] (D) drying for 10 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature of 70° C., removing residual ammonium sulfate by immersing the dried nascent hollow fiber composite membrane into a second amount of deionized water, putting the dried nascent hollow fiber composite membrane without the residual ammonium sulfate into a multi-roll heat treatment device, heating to 290° C. at a heating rate of 8° C./min, sintering, and performing heat preservation for 2 h, so that the perfluoropolymer hollow fiber composite membrane is obtained.

[0056] The perfluoropolymer hollow fiber composite membrane prepared by the above method has a surface separation layer with a thickness of 30 μm. After being continuously tested for 1 h under an operating pressure of 0.02 MPa, the perfluoropolymer hollow fiber composite membrane has a kerosene flux of 1000 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar and a dimethyl sulfoxide flux of 1300 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar.

Fifth Embodiment

[0057] A perfluoropolymer hollow fiber composite membrane preparation method comprises the steps of: [0058] (A) preparing a supporting layer of the perfluoropolymer hollow fiber composite membrane, which comprises weaving basalt fiber filaments into fiber braided tube with an outer diameter of 1800 μm through two-dimensional weaving technology, and performing heat treatment on the fiber braided tube at 350° C. for 5 min to eliminate an internal stress and fix a net structure thereof, thereby obtaining the supporting layer of the perfluoropolymer hollow fiber composite membrane; [0059] (B) preparing a membrane casting solution as a functional layer, which comprises obtaining a mixed solution by mixing a polyperfluoroethylene propylene aqueous dispersion with a concentration of 50 wt. %, a mixture of cellulose with a proportion of 6 wt. % in the mixture and an N-methylmorpholine-N-oxide aqueous solution with a proportion of 94 wt. % in the mixture, and an N-methylmorpholine-N-oxide aqueous solution at 90° C., and defoaming the mixed solution at a constant temperature, so that the membrane casting solution is obtained, wherein a proportion of the polyperfluoroethylene propylene aqueous dispersion in the mixed solution is 25 wt. %, a proportion of the mixture in the mixed solution is 4 wt. %, and a proportion of the N-methylmorpholine-N-oxide aqueous solution in the mixed solution is 71 wt. %; [0060] (C) preparing a nascent hollow fiber composite membrane, which comprises compositing by uniformly coating the membrane casting solution on an outer surface of the supporting layer through an annular spinneret with a temperature of 90° C. using chemical fiber concentric circle composite spinning technology, putting the supporting layer after compositing into a first amount of deionized water with a temperature of 25° C., solidifying and forming, so that the nascent hollow fiber composite membrane is obtained; and [0061] (D) drying for 10 min after putting the nascent hollow fiber composite membrane to a hot air box with a temperature of 75° C., removing residual N-methylmorpholine-N-oxide by immersing the dried nascent hollow fiber composite membrane into a second amount of deionized water, putting the dried nascent hollow fiber composite membrane without the residual N-methylmorpholine-N-oxide into a multi-roll heat treatment device, heating to 310° C. at a heating rate of 15° C./min, sintering, and performing heat preservation for 1 h, so that the perfluoropolymer hollow fiber composite membrane is obtained.

[0062] The perfluoropolymer hollow fiber composite membrane prepared by the above method has a surface separation layer with a thickness of 50 After being continuously tested for 1 h under an operating pressure of 0.02 MPa, the perfluoropolymer hollow fiber composite membrane has a kerosene flux of 580 L.Math.m.sup.−2.Math.h.sup.−1.Math.bar and an N,N-dimethylformamide flux of 650 L.Math.m.sup.−2.Math.h.sup.−1 bar.