CN117379996A - Reinforced polyvinylidene fluoride hollow fiber membrane and preparation method thereof - Google Patents
Reinforced polyvinylidene fluoride hollow fiber membrane and preparation method thereof Download PDFInfo
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- CN117379996A CN117379996A CN202311246729.2A CN202311246729A CN117379996A CN 117379996 A CN117379996 A CN 117379996A CN 202311246729 A CN202311246729 A CN 202311246729A CN 117379996 A CN117379996 A CN 117379996A
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- 239000012528 membrane Substances 0.000 title claims abstract description 245
- 239000002033 PVDF binder Substances 0.000 title claims abstract description 141
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 141
- 239000012510 hollow fiber Substances 0.000 title claims abstract description 128
- 238000002360 preparation method Methods 0.000 title abstract description 43
- 238000005266 casting Methods 0.000 claims abstract description 112
- 239000002131 composite material Substances 0.000 claims abstract description 79
- 230000007704 transition Effects 0.000 claims abstract description 20
- 238000009945 crocheting Methods 0.000 claims abstract description 15
- 239000011148 porous material Substances 0.000 claims abstract description 12
- 238000009987 spinning Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 55
- 239000003085 diluting agent Substances 0.000 claims description 43
- 239000007788 liquid Substances 0.000 claims description 43
- 238000004804 winding Methods 0.000 claims description 31
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 26
- 230000008569 process Effects 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 17
- 238000009998 heat setting Methods 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 15
- 238000001816 cooling Methods 0.000 claims description 14
- RWCCWEUUXYIKHB-UHFFFAOYSA-N benzophenone Chemical compound C=1C=CC=CC=1C(=O)C1=CC=CC=C1 RWCCWEUUXYIKHB-UHFFFAOYSA-N 0.000 claims description 13
- 238000005191 phase separation Methods 0.000 claims description 10
- FLKPEMZONWLCSK-UHFFFAOYSA-N diethyl phthalate Chemical compound CCOC(=O)C1=CC=CC=C1C(=O)OCC FLKPEMZONWLCSK-UHFFFAOYSA-N 0.000 claims description 6
- MTZQAGJQAFMTAQ-UHFFFAOYSA-N ethyl benzoate Chemical compound CCOC(=O)C1=CC=CC=C1 MTZQAGJQAFMTAQ-UHFFFAOYSA-N 0.000 claims description 6
- QPJVMBTYPHYUOC-UHFFFAOYSA-N methyl benzoate Chemical compound COC(=O)C1=CC=CC=C1 QPJVMBTYPHYUOC-UHFFFAOYSA-N 0.000 claims description 6
- URAYPUMNDPQOKB-UHFFFAOYSA-N triacetin Chemical compound CC(=O)OCC(OC(C)=O)COC(C)=O URAYPUMNDPQOKB-UHFFFAOYSA-N 0.000 claims description 6
- 239000001087 glyceryl triacetate Substances 0.000 claims description 3
- 235000013773 glyceryl triacetate Nutrition 0.000 claims description 3
- 229940095102 methyl benzoate Drugs 0.000 claims description 3
- 229960002622 triacetin Drugs 0.000 claims description 3
- 229920000728 polyester Polymers 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 10
- 230000035515 penetration Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 25
- 238000001000 micrograph Methods 0.000 description 20
- 238000009940 knitting Methods 0.000 description 17
- 238000000926 separation method Methods 0.000 description 17
- 238000003756 stirring Methods 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 239000012965 benzophenone Substances 0.000 description 11
- 230000007547 defect Effects 0.000 description 10
- 239000012466 permeate Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 5
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 4
- 229920003082 Povidone K 90 Polymers 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000004033 plastic Substances 0.000 description 4
- 229920003023 plastic Polymers 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000002145 thermally induced phase separation Methods 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
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- 238000004519 manufacturing process Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000001112 coagulating effect Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000007719 peel strength test Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004695 Polyether sulfone Substances 0.000 description 1
- 206010042674 Swelling Diseases 0.000 description 1
- 229920004933 Terylene® Polymers 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000002313 adhesive film Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001493 electron microscopy Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920006149 polyester-amide block copolymer Polymers 0.000 description 1
- 229920006393 polyether sulfone Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
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- 230000008961 swelling Effects 0.000 description 1
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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
- B01D71/34—Polyvinylidene fluoride
-
- 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
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
-
- 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
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0013—Casting processes
-
- 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
- B01D69/087—Details relating to the spinning process
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04B—KNITTING
- D04B31/00—Crocheting processes for the production of fabrics or articles
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06N—WALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
- D06N3/00—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
- D06N3/0002—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof characterised by the substrate
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06N—WALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
- D06N3/00—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
- D06N3/0056—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof characterised by the compounding ingredients of the macro-molecular coating
- D06N3/0061—Organic fillers or organic fibrous fillers, e.g. ground leather waste, wood bark, cork powder, vegetable flour; Other organic compounding ingredients; Post-treatment with organic compounds
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06N—WALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
- D06N3/00—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
- D06N3/007—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof characterised by mechanical or physical treatments
- D06N3/0077—Embossing; Pressing of the surface; Tumbling and crumbling; Cracking; Cooling; Heating, e.g. mirror finish
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06N—WALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
- D06N3/00—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
- D06N3/04—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof with macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/40—Fibre reinforced membranes
Abstract
The invention provides an enhanced polyvinylidene fluoride hollow fiber membrane and a preparation method thereof, wherein the hollow fiber membrane structure consists of a hollow woven tube and a polyvinylidene fluoride porous membrane layer wrapped outside the woven tube; wherein, the hollow crochet galloon tube and the polyvinylidene fluoride porous membrane are mutually penetrated to form a transition layer; the hollow crochet tube is formed by crocheting single-strand composite yarns, and the single-strand composite yarns are formed by composite spinning of textured yarns and fully drawn yarns FDY, wherein the total number of the textured yarns is 50-100; the thickness of the film layer of the reinforced polyvinylidene fluoride hollow fiber film is 0.1-0.2mm; wherein the thickness of the transition layer is 20-80 μm. The hollow woven tube is formed by woven special fluffy single-strand composite yarns compounded by textured yarns and fully drawn yarns, and the hollow woven tube has certain fluffy feeling and pores due to the selection of special materials, so that yarns on the outer surface are loosened, and protruding yarn ends exist. The bonding strength between the hollow woven tube and the porous membrane layer is enhanced by the mutual penetration of the fluffy yarn, the protruding yarn ends and the high-temperature casting solution.
Description
Technical Field
The invention relates to the technical field of membrane filtration, in particular to an enhanced polyvinylidene fluoride hollow fiber membrane and a preparation method thereof.
Background
As one of the 21 st century high technology, the membrane separation technology has the advantages of low energy consumption, high single-stage separation efficiency, simple process, small occupied area and the like compared with the conventional separation method. With the continuous development of the world industry, the problem of water resource deterioration is increasingly serious, and the requirements on membrane performance are also increasingly high. At present, due to lower mechanical strength, membrane filaments bear higher and higher risk of filament breakage when facing severe and complex water environment. Therefore, technical development of high-strength hollow fiber membranes has been receiving increasing attention.
The prior high-strength hollow fiber membrane mainly comprises a porous hollow fiber membrane, a fiber reinforced hollow fiber membrane, a lining pipe reinforced hollow fiber membrane and the like, wherein the lining pipe reinforced hollow fiber membrane is a main application research direction at present due to simple preparation process and excellent performance. The lining pipe reinforced hollow fiber membrane mainly comprises a lining pipe and a porous membrane layer. The inner lining tube is used as a supporting layer of the film layer and is mainly woven by polyester and polyamide long fibers, so that tensile strength is provided for the film yarn. As the separation layer, polyvinylidene fluoride, polyethersulfone and the like are commonly used materials. Due to the fact that the material properties of the lining pipe and the material properties of the membrane layer are different, the problem that the bonding strength of the lining pipe and the membrane layer is low is caused, the problem that the membrane layer is peeled off and the like frequently occurs in the application process of the lining pipe reinforced hollow fiber membrane, and the filtering effect is poor.
Furthermore, the quality of the liner is affected by the quality of the yarn (product upstream of the liner), and there are often protruding yarn ends on the liner surface. When the heat treatment process is not performed, protruding yarn ends penetrate through the porous membrane layer to cause macroporous defects, and such problems often occur for lining pipe reinforced hollow fiber membranes prepared by a non-solvent induced phase separation method.
In view of this, developing a reinforced hollow fiber membrane that has both high bonding strength of the backing tube and the membrane layer and is free from defects is a technical problem that is urgently needed to be solved by those skilled in the art.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an enhanced polyvinylidene fluoride hollow fiber membrane and a preparation method thereof, wherein single-strand composite yarns formed by compositing textured yarns and fully drawn yarns FDY are selected, and are crocheted to form a hollow crocheted tube, and the hollow crocheted tube is combined with polyvinylidene fluoride in a high strength manner, so that the formed enhanced hollow fiber membrane has the advantages of good integrity and high peel strength.
The specific invention comprises the following steps:
in a first aspect, the invention provides a reinforced polyvinylidene fluoride hollow fiber membrane, which consists of a hollow woven tube and a polyvinylidene fluoride porous membrane layer wrapped outside the woven tube, wherein the hollow woven tube and the polyvinylidene fluoride porous membrane layer are mutually penetrated to form a transition layer;
The hollow crochet tube is formed by crocheting single-strand composite yarns, and the single-strand composite yarns are formed by composite spinning of textured yarns and fully drawn yarns FDY, wherein the total number of the textured yarns is 50-100;
the thickness of the membrane layer of the reinforced polyvinylidene fluoride hollow fiber membrane is 0.1-0.2mm; wherein the thickness of the transition layer is 20-80 mu m.
Optionally, in the single-strand composite yarn, the textured yarn and the fully drawn yarn FDY are made of terylene;
the ratio of the number of the textured yarns to the number of the fully drawn yarns FDY is (2:8) - (5:5);
the textured yarn is a stretch textured yarn DTY or an air textured yarn ATY.
Optionally, in the single-strand composite yarn, the textured yarn and fully drawn yarn FDY have diameters of 10-20 μm.
Optionally, the hollow woven tube is not heat-set, the outer surface yarns are relaxed, and there are protruding yarn ends;
the number of the crochet needles is 10-14, and the crochet density is 20-26;
the outer diameter of the hollow woven tube is 1.1-1.8mm;
the pore area of the hollow woven tube is 0.02-0.04mm 2 ；
The tensile strength of the hollow woven tube is 80-150N.
Optionally, the tensile strength of the polyvinylidene fluoride porous film layer is more than or equal to 5.0MPa;
the peeling strength of the hollow crochet tube and the polyvinylidene fluoride porous membrane layer is 3.0-4.5MPa.
In a second aspect, the present invention provides a method for preparing the reinforced polyvinylidene fluoride hollow fiber membrane according to the first aspect, the method comprising the following steps:
s1, preparing a composite yarn from 50-100 textured yarns and fully drawn yarns FDY according to the root ratio of (2:8) - (5:5) by a composite winding process;
s2, crocheting the composite yarns into hollow crocheted pipes by means of a crocheting machine, and winding the hollow crocheted pipes into discs without a heat setting device;
s3, uniformly mixing polyvinylidene fluoride and a diluent, and heating to 190-250 ℃ to form a homogeneous phase high Wen Zhu membrane solution;
s4, extruding the hollow woven tube and the homogeneous high-temperature casting film liquid simultaneously, and converging at an outlet of an annular spinneret to form a primary film with an inner layer of the hollow woven tube and an outer layer of the homogeneous high-temperature casting film liquid;
s5, immersing the primary membrane in an air bath of 0.1-0.5S, cooling in a water bath of 40-60 ℃, standing for 2-3S, forming the polyvinylidene fluoride porous membrane layer by the high-temperature membrane casting liquid on the outer layer through a phase separation method, and winding to obtain a solidified hollow fiber membrane;
s6, removing the diluent in the solidified hollow fiber membrane by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Optionally, in step S1, the textured yarn is a stretch textured yarn DTY or an air textured yarn ATY.
Optionally, in step S2, the number of the crochet needles is 10-14, the crochet density is 20-26, so as to regulate and control the outer diameter of the hollow crochet tube formed by the crochet to be 1.1-1.8mm and the aperture to be 0.02-0.04mm 2 。
Optionally, the content of the diluent in the homogeneous high-temperature casting solution is 70-82wt%;
the diluent is one or more of diphenyl ketone, methyl benzoate, ethyl benzoate, diethyl phthalate and glyceryl triacetate.
Optionally, in step S3, the molecular weight of the polyvinylidene fluoride is 30-50 kilodaltons;
the viscosity of the homogeneous high-temperature casting film liquid is 200-1000 mPa.s.
Compared with the prior art, the invention has the following advantages:
the invention provides an enhanced polyvinylidene fluoride hollow fiber membrane, wherein a hollow woven tube is formed by woven special fluffy single-strand composite yarns compounded by textured yarns (stretch textured yarns DTY or air textured yarns ATY) and fully stretched yarns, and the hollow woven tube has certain fluffy feeling and pores due to the selection of special materials, and the yarns on the outer surface are loosened and protruding yarn ends exist under the observation of an electron microscope. The bonding strength between the hollow woven tube layer and the porous membrane layer is enhanced by the mutual penetration of the fluffy yarns, the protruding yarn ends and the high-temperature casting solution.
The invention also provides a preparation method of the reinforced polyvinylidene fluoride hollow fiber membrane, by means of the thermal process of thermally induced phase separation, the fluffy hollow woven tube is contacted with the polyvinylidene fluoride homogeneous phase high Wen Zhumo liquid, the yarn ends protruding from the surface of the hollow woven tube are rapidly softened after being combined with the casting solution, the casting solution further permeates into the fluffy gaps of the hollow woven tube, and a transition layer with a certain thickness is formed after the mutual permeation, so that the binding force of the hollow woven tube and the porous membrane layer is increased, and the defect of macropores of the porous membrane layer due to penetrability of the protruding yarn ends is avoided, so that the membrane yarn has good integrity.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a scanning electron microscope image of a cross section of an enhanced polyvinylidene fluoride hollow fiber membrane provided by an embodiment of the invention;
FIG. 2 shows a flow chart of a preparation method of the reinforced polyvinylidene fluoride hollow fiber membrane provided by the embodiment of the invention;
FIG. 3 is a scanning electron microscope image of the outer surface of a hollow woven tube according to example 1 of the present invention;
FIG. 4 shows an inner surface scanning electron microscope image of the reinforced polyvinylidene fluoride hollow fiber membrane provided in example 1 of the present invention;
FIG. 5 shows a scanning electron microscope image of the stripping surface of the hollow woven tube and polyvinylidene fluoride film layer provided in embodiment 1 of the present invention;
FIG. 6 shows a partial scanning electron microscope image of the reinforced polyvinylidene fluoride hollow fiber membrane provided in example 1 of the present invention;
FIG. 7 is a scanning electron microscope image of a cross section of a membrane layer of the reinforced polyvinylidene fluoride hollow fiber membrane provided in example 1 of the present invention;
FIG. 8 is a scanning electron microscope image of the outer surface of the hollow woven tube provided in comparative example 1 of the present invention;
FIG. 9 is a scanning electron microscope image of the stripping surface of the hollow woven tube and polyvinylidene fluoride film layer provided in comparative example 1 of the present invention;
fig. 10 shows an inner surface scanning electron microscope image of the reinforced polyvinylidene fluoride hollow fiber membrane provided in comparative example 3 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Any product that is the same as or similar to the present invention, which anyone in the light of the present invention or combines the present invention with other prior art features, falls within the scope of the present invention based on the embodiments of the present invention. And all other embodiments that may be made by those of ordinary skill in the art without undue burden and without departing from the scope of the invention.
Specific experimental steps or conditions are not noted in the examples and may be performed in accordance with the operation or conditions of conventional experimental steps described in the prior art in the field. The reagents used, as well as other instruments, are conventional reagent products available commercially, without the manufacturer's knowledge. Furthermore, the drawings are merely schematic illustrations of embodiments of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities.
Techniques, methods and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the present description where appropriate.
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for defining the components, and are merely for convenience in distinguishing the corresponding components, and the terms are not meant to have any special meaning unless otherwise indicated, so that the scope of the present invention is not to be construed as being limited.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Before explaining a reinforced polyvinylidene fluoride hollow fiber membrane and a preparation method thereof provided by the invention in detail, the following description is necessary for the related art:
in order to improve the bonding effect between the inner liner tube and the membrane layer, patent CN102258947a discloses a method of treating the hollow woven tube with plasma, then coating the membrane separation layer outside the woven tube, and improving the interface strength by improving the wettability and hydrogen bonding force of the surface of the woven tube; the patent CN106040024B uses dimethyl sulfoxide to carry out swelling treatment on the polyester braided tube at 150-170 ℃, thereby improving the bonding strength between the membrane separation layer and the hollow braided tube. The two methods achieve the effect of improving the interfacial bonding force, but both the two methods belong to a two-step preparation method (firstly treating the braided tube and then coating the casting solution), the preparation process adds extra production cost (a plasma machine and dimethyl sulfoxide), and the preparation process is complicated. Patent CN107537325a discloses a method of fastening a fastening sheet structure of a film layer to an inner wall of a hole of a warp knitting tape to improve an interfacial bonding force. However, the tubular warp knitting belts are difficult to prepare, the preparation process is complex, the time cost is high, and the large-scale production is not facilitated.
The invention aims to solve the problems of weak interface combination of a porous membrane layer and a lining pipe of the traditional lining pipe reinforced hollow fiber membrane and more defects on the surface of membrane wires. The fluffy hollow woven tube is contacted with high-temperature film casting liquid, and the high Wen Zhu film liquid and the hollow woven tube are mutually permeated to form the reinforced polyvinylidene fluoride hollow fiber film with a transition layer with a certain thickness due to the existence of fluffy pores. The transition layer increases the binding force between the hollow woven tube and the porous membrane layer, and simultaneously avoids the defect of macropores of the porous membrane layer caused by penetrability of protruding yarn ends, so that the membrane yarn has good integrity. The specific implementation mode is as follows:
in a first aspect, the present invention provides an enhanced polyvinylidene fluoride hollow fiber membrane, fig. 1 shows a scanning electron microscope image of a cross section of the enhanced polyvinylidene fluoride hollow fiber membrane provided by the embodiment of the present invention, as shown in fig. 1, the enhanced polyvinylidene fluoride hollow fiber membrane is composed of a hollow woven tube and a polyvinylidene fluoride porous membrane layer wrapped outside the woven tube, wherein the hollow woven tube and the polyvinylidene fluoride porous membrane layer are mutually penetrated to form a transition layer; the hollow crochet tube is formed by crocheting single-strand composite yarns, and the single-strand composite yarns are formed by composite spinning of textured yarns and fully drawn yarns FDY, wherein the total number of the textured yarns is 50-100; the thickness of the film layer of the reinforced polyvinylidene fluoride hollow fiber film is 0.1-0.2mm; wherein the thickness of the transition layer is 20-80 μm. In specific implementation, the invention needs to balance the relation among the fluffiness and the tensile strength of the hollow woven tube and the permeability of the casting solution in the hollow woven tube by regulating and controlling the composition of the special fluffy single-strand composite yarn so as to avoid the problem that the casting solution excessively permeates into the hollow woven tube and blocks a water outlet channel due to overlarge fluffiness of the hollow woven tube; and the film casting liquid cannot permeate or permeate too little due to too little fluffiness, so that the thickness of the formed transition layer cannot meet the peeling strength requirement of the hollow woven tube and the polyvinylidene fluoride film layer; and the problem that the tensile strength of the reinforced polyvinylidene fluoride hollow fiber membrane does not reach the standard due to insufficient tensile strength of the hollow woven tube. The invention is determined by a large number of experimental verification, and the textured yarn with the diameter of 10-20 mu m and the fully drawn yarn FDY are selected for compound spinning, so that the formed special fluffy single-strand compound yarn is used for crocheting the hollow crocheting tube.
In specific implementation, in the special fluffy single-strand composite yarn, the ratio of the number of textured yarns to the number of drawn yarns is (2:8) - (5:5), for example, the ratio of textured yarns in the single-strand composite yarn is too large, so that the roundness of a hollow woven tube formed by crocheting can be reduced; if the ratio of the drawn yarn in the single-strand composite yarn is too large, the bulkiness is poor, and the peeling strength between the hollow woven tube and the polyvinylidene fluoride film layer is reduced.
In specific implementation, the total number of textured yarns and fully drawn yarns FDY in the fluffy single-strand composite yarn is 50-100. The textured yarn is drawn textured yarn DTY or air textured yarn ATY. The draw textured yarn DTY is made by drawing and false twisting textured by using a pre-oriented yarn POY as a precursor, and tends to have certain elasticity and contractility. The air textured yarn ATY is formed by interlacing a yarn bundle by using an air jet technology to form an irregularly twisted yarn loop, so that the yarn bundle has a fluffy looped shape.
In specific implementation, the outer diameter of the hollow crochet tube is mainly controlled by the number of crochet needles, and when the number of single-strand composite yarns is the same, the more the number of needles is, the thicker the hollow crochet tube is, and vice versa. The roundness of the hollow crochet tube is regulated and controlled by crochet density, and the greater the crochet density is, the better the roundness is, and vice versa. The invention is proved by a large number of experiments, and the hollow crochet tube with the external diameter of 1.1-1.8mm and good roundness is obtained by controlling the crochet needle number of 10-14 and the crochet density of 20-26. The hollow woven tube formed under the crochet condition has the tensile strength which meets the requirement and is 80-150N, so that the strength of the finally formed reinforced polyvinylidene fluoride hollow fiber membrane is effectively ensured. At the same time, the aperture formed in the hollow woven tube is 0.02-0.04mm 2 . The pore diameter does not cause the problem of the casting solution leaking into the hollow woven tube.
In specific implementation, the thickness of the membrane layer of the reinforced polyvinylidene fluoride hollow fiber membrane is controlled to be 0.1-0.2mm. When the thickness of the membrane layer is less than 0.1mm, the membrane layer is damaged due to the friction of the membrane wires (the friction between the membrane wires and pollutants or between the membrane wires) and loses the effect of filtering pollutants, and when the thickness of the membrane layer is greater than 0.2mm, the membrane layer is too thick, so that the transmembrane pressure difference is too high and the water permeability resistance is increased.
In specific implementation, the thickness of a transition layer formed by the inter-penetration between the hollow woven tube and the polyvinylidene fluoride porous membrane layer is 20-80 mu m, and the existence of the transition layer enables the peeling strength of the hollow woven tube and the polyvinylidene fluoride porous membrane layer to be 3.0-4.5MPa, and the tensile strength of the polyvinylidene fluoride porous membrane layer to be more than or equal to 5.0MPa, so that the peeling requirement is met.
In a second aspect, the present invention provides a method for preparing the reinforced polyvinylidene fluoride hollow fiber membrane of the first aspect, fig. 2 shows a flowchart of a method for preparing the reinforced polyvinylidene fluoride hollow fiber membrane provided in an embodiment of the present invention, and as shown in fig. 2, the method for preparing the reinforced polyvinylidene fluoride hollow fiber membrane includes the following steps:
s1, preparing a composite yarn from 50-100 textured yarns and fully drawn yarns FDY according to the root ratio of (2:8) - (5:5) by a composite winding process;
S2, crocheting the composite yarns into hollow crocheted pipes by means of a crocheting machine, and winding the hollow crocheted pipes into discs without a heat setting device;
s3, uniformly mixing polyvinylidene fluoride and a diluent, and heating to 190-250 ℃ to form a homogeneous phase high Wen Zhu membrane solution;
s4, extruding the hollow woven tube and the homogeneous high-temperature casting solution simultaneously, and converging at the outlet of the annular spinneret to form a primary membrane of which the inner layer is the hollow woven tube and the outer layer is the homogeneous high-temperature casting solution;
s5, immersing the primary membrane in an air bath of 0.1-0.5S, cooling in the water bath of 40-60 ℃, standing for 2-3S, forming a polyvinylidene fluoride porous membrane layer by the high-temperature membrane casting liquid on the outer layer through a phase separation method, and winding to obtain a solidified hollow fiber membrane;
s6, removing the diluent in the solidified hollow fiber membrane by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
In specific implementation, the preparation method provided by the invention is characterized in that by means of a thermally induced phase separation process, polyvinylidene fluoride homogeneous phase high Wen Zhu membrane liquid and the hollow woven tube introduced in the first aspect are extruded together through the annular spinneret, the fluffy hollow woven tube is contacted with polyvinylidene fluoride homogeneous phase high Wen Zhumo liquid, the protruding yarn end on the surface of the hollow woven tube is rapidly softened after being combined with casting membrane liquid, the casting membrane liquid is further permeated into fluffy gaps of the hollow woven tube, a transition layer with a certain thickness is formed after the mutual permeation, the binding force of the hollow woven tube and the porous membrane layer is increased, and meanwhile, the macroporous defect of the porous membrane layer due to penetrability of the protruding yarn end is avoided, so that the membrane wire has good integrity. Finally forming a primary membrane with an inner layer of a hollow woven tube, an outer layer of a homogeneous high-temperature casting solution and a transition layer with a certain thickness in the middle, and further carrying out air bath and water bath cooling treatment and diluent removal treatment on the primary membrane to finally obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
In some embodiments, the fluffy hollow woven tube is crocheted from a specially made fluffy single-strand composite yarn, the single-strand composite yarn is formed by composite spinning of textured yarn and fully drawn yarn FDY with a total of 50-100 textured yarns and a diameter of 10-20 μm, and the preferred textured yarn and fully drawn yarn FDY have a diameter of 10 μm; in the special fluffy single-strand composite yarn, the number ratio of textured yarn to drawn yarn is (2:8) - (5:5), for example, the excessive proportion of textured yarn in the single-strand composite yarn can lead to the reduction of the roundness of a hollow crocheted tube formed by crocheting; if the ratio of the drawn yarn in the single-strand composite yarn is too large, the bulkiness is poor, and the peeling strength between the hollow woven tube and the polyvinylidene fluoride film layer is reduced.
In some embodiments, the present invention may employ a fluffy hollow woven tube without heat treatment as a liner tube for the preparation of the reinforced polyvinylidene fluoride hollow fiber membrane. Namely, the preparation process of the invention does not need to further process the yarn end protruding from the hollow crochet surface, thereby effectively simplifying the preparation process. The quality of existing conventional liners is affected by the quality of the yarn (the product upstream of the liner), and there are often protruding yarn ends on the liner surface. Without heat treatment, the protruding yarn ends would penetrate the porous membrane layer, resulting in macropore defects. Based on the method, the textured yarn and the fully drawn yarn FDY are used as raw materials of single-strand composite yarns, the hollow woven tube is formed by crocheting, after the hollow woven tube is combined with the casting solution, yarn ends protruding from the surface are rapidly softened, the casting solution further permeates into gaps of the hollow woven tube in a fluffy manner, and a transition layer with a certain thickness is formed after the casting solution permeates into each other, so that the binding force between the hollow woven tube and the porous membrane layer is increased, and the defect of macropores of the porous membrane layer due to penetrability of protruding yarn ends is avoided, so that the membrane yarn has good integrity.
In some embodiments, the outer diameter of the hollow crochet is primarily controlled by the number of crochet needles, with the number of needles being greater the number of individual composite yarns, the thicker the hollow crochet tube and vice versa. The roundness of the hollow crochet tube is regulated and controlled by crochet density, and the greater the crochet density is, the better the roundness is, and vice versa. The invention is proved by a large number of experiments, and the hollow crochet tube with the external diameter of 1.1-1.8mm and good roundness is obtained by controlling the crochet needle number of 10-14 and the crochet density of 20-26. The hollow woven tube formed under the crochet condition has the tensile strength which meets the requirement and is 80-150N, so that the strength of the finally formed reinforced polyvinylidene fluoride hollow fiber membrane is effectively ensured. At the same time, the aperture formed in the hollow woven tube is 0.02-0.04mm 2 . The pore diameter does not cause the problem of the casting solution leaking into the hollow woven tube. Meanwhile, the thickness of the formed transition layer is controlled to be 20-80 mu m, so that the peeling strength between the hollow woven tube and the polyvinylidene fluoride porous membrane layer is ensured to be 3.0-4.5MPa, the tensile strength of the polyvinylidene fluoride porous membrane layer is more than or equal to 5.0MPa, and the peeling requirement is met.
In some embodiments, the homogeneous high temperature casting solution has a viscosity of 200 to 1000 mPas, wherein the diluent is present in an amount of 70 to 82wt%; the diluent is one or more selected from benzophenone, methyl benzoate, ethyl benzoate, diethyl phthalate and glyceryl triacetate. The molecular weight of polyvinylidene fluoride is 30-50 ten thousand daltons.
In order to make the present invention more clearly understood by those skilled in the art, the following examples will illustrate a reinforced polyvinylidene fluoride hollow fiber membrane and a method for preparing the same.
Example 1
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined in a ratio of 2:8, and the composite yarn is manufactured by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.4mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
The sectional scanning electron microscope of the reinforced polyvinylidene fluoride hollow fiber membrane provided in the embodiment 1 of the invention is shown in fig. 1, and fig. 3 shows the scanning electron microscope of the outer surface of the hollow woven tube provided in the embodiment 1 of the invention, and as shown in fig. 3, the yarns on the outer surface of the hollow woven tube are loose, and protruding yarn ends exist.
Fig. 4 shows a scanning electron microscope image of the inner surface of the reinforced polyvinylidene fluoride hollow fiber membrane provided in embodiment 1 of the present invention, as shown in fig. 4, the inner surface of the reinforced polyvinylidene fluoride hollow fiber membrane provided in embodiment 1 has no redundant feed liquid penetrating into the hollow woven tube layer, so as to avoid the problems of waste of casting solution and blockage of hollow channels by the casting solution.
Fig. 5 shows a scanning electron microscope image of a stripping surface of a hollow woven tube and a polyvinylidene fluoride film layer provided in embodiment 1 of the present invention, in which (a) shows a scanning electron microscope image of a stripping surface of a hollow woven tube, and (b) shows a scanning electron microscope image of a stripping surface of a polyvinylidene fluoride film layer, as shown in fig. 5, a polyvinylidene fluoride porous film layer material still exists on the stripping surface of the hollow woven tube, and the polyvinylidene fluoride porous film layer material permeates into fluffy pores of the hollow woven tube and is firmly combined with fluffy yarns.
Fig. 6 shows a partial sem image of the reinforced polyvinylidene fluoride hollow fiber membrane provided in embodiment 1 of the present invention, specifically, a sem image of a transition layer formed by permeation of a casting solution into a hollow woven tube, and as shown in fig. 6, the thickness of the transition layer is about 52 μm.
FIG. 7 shows a scanning electron microscope image of a cross section of a membrane layer of the reinforced polyvinylidene fluoride hollow fiber membrane provided in example 1 of the present invention, wherein the thickness of the membrane layer is 0.203mm.
Example 2
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined in a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.04mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution;
s5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence by a phase separation method, and winding to obtain a solidified reinforced hollow fiber membrane;
and S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 3
The specific implementation steps are as follows:
s1, yarn preparation: 100 total draw textured yarns ATY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.04mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution;
s5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence by a phase separation method, and winding to obtain a solidified reinforced hollow fiber membrane;
and S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 4
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.04mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 25%.
S4, preparation of an enhanced hollow fiber membrane: simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution;
s5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence by a phase separation method, and winding to obtain a solidified reinforced hollow fiber membrane;
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 5
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.04mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 30%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence by a phase separation method, and winding to obtain a solidified reinforced hollow fiber membrane;
and S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 6
The specific implementation steps are as follows:
s1, yarn preparation: a total of 50 draw textured yarns DTY having a diameter of 10 μm and fully drawn yarns FDY were blended in a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10 needles with the crochet needle number, 20 knitting density and 0.035mm aperture 2 The hollow woven tube with the outer diameter of 1.1mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 7
The specific implementation steps are as follows:
s1, yarn preparation: the total number of draw textured yarns DTY and fully drawn yarns FDY was 100 and the diameter of the draw textured yarns was 10 μm according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separating plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the crochet needle number is 14 needles formed through the circular motion between the knitting needles and the cams, so that the crochet is hooked Weaving density 20, pore diameter 0.03mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 8
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams is used for forming 14 needles with the crochet needle number, the crochet density 26 and the aperture of 0.025mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Example 9
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 5:5, preparing the composite yarn by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 14-needle crochet needles with the crochet density 26 and the aperture of 0.02mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: and simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution.
S5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Comparative example 1
The specific implementation steps are as follows:
s1, yarn preparation: the total number of 100 fully drawn yarns FDY with the diameter of 10 μm are manufactured into yarns through a winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10 needles with the crochet needle number, 20 knitting density and 0.05mm aperture 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and mixing polyvinylidene fluoride with a diluent, heating to 250 ℃, stirring uniformly, standing and defoaming to obtain uniform casting film liquid, wherein the diluent is benzophenone, and the mass fraction of the polyvinylidene fluoride is 18%.
S4, preparation of an enhanced hollow fiber membrane: simultaneously extruding the hollow woven tube and the high-temperature casting solution, and converging at the outlet of the annular spinneret to form a primary membrane with the inner layer being the hollow woven tube and the outer layer being the homogeneous high-temperature casting solution;
s5, taking the hollow woven tube as an inner layer and taking the primary membrane of the homogeneous high-temperature casting solution as an outer layer, immersing the primary membrane into a water bath at 40 ℃ for cooling after 0.5S of air bath, forming a porous membrane layer by the homogeneous high-temperature casting solution of the outer layer after 2S of residence, and winding to obtain the solidified reinforced hollow fiber membrane.
And S6, removing the diluent in the solidified reinforced hollow fiber membrane obtained in the step S5 by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
Fig. 8 shows a scanning electron microscope image of the outer surface of the hollow woven tube provided in comparative example 1 of the present invention, and as shown in fig. 8, the outer surface of the hollow woven tube provided in comparative example 1 is flat and smooth.
Fig. 9 shows a scanning electron microscope image of a stripping surface of a hollow woven tube and a polyvinylidene fluoride film layer provided in comparative example 1 of the present invention, wherein (a) shows a scanning electron microscope image of a stripping surface of a hollow woven tube, and (b) shows a scanning electron microscope image of a stripping surface of a polyvinylidene fluoride film layer, and as shown in fig. 9, the stripping surface of a hollow woven tube is smoother and has no residual porous film layer material.
Comparative example 2
The specific implementation steps are as follows:
s1, yarn preparation: 100 drawn textured yarns DTY with a diameter of 10 μm and fully drawn yarns FDY were combined according to a ratio of 2:8, and the composite yarn is manufactured by a composite winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10-needle crochet needles with the crochet density of 20 and the aperture of 0.04mm 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and under normal temperature, mixing polyvinylidene fluoride, dimethylacetamide and PVP K90, stirring and dissolving to obtain a uniform solution, and standing and defoaming to obtain a casting film solution, wherein the mass fraction of the polyvinylidene fluoride is 18%, and the mass fraction of the PVP K90 is 5%.
S4, preparation of an enhanced hollow fiber membrane: and (3) extruding the hollow woven tube and the casting film liquid together to obtain the primary film.
S5, immersing the nascent film into a coagulating bath at 40 ℃ after passing through an air bath for 0.5S, and after staying for 10S, rinsing the film in a rinsing tank and then rolling.
Comparative example 3
The specific implementation steps are as follows:
s1, yarn preparation: the total number of 100 fully drawn yarns FDY with the diameter of 10 μm are manufactured into yarns through a winding process.
S2, preparing a hollow crochet tube: the composite yarn sequentially passes through a thread separation plate, a tension controller, a yarn feeding rod and other structures of the crochet machine, and the circular motion between the knitting needles and the cams forms 10 needles with the crochet needle number, 20 knitting density and 0.05mm aperture 2 The hollow woven tube with the outer diameter of 1.8mm is wound into a disc without a heat setting device.
S3, preparing polyvinylidene fluoride casting film liquid: and under normal temperature, mixing polyvinylidene fluoride, dimethylacetamide and PVP K90, stirring and dissolving to obtain a uniform solution, and standing and defoaming to obtain a casting film solution, wherein the mass fraction of polyvinylidene fluoride is 18%, and the mass fraction of PVP K90 is 5%.
S4, preparation of an enhanced hollow fiber membrane: and (3) extruding the hollow crochet tube and the casting film liquid together to obtain a primary film.
S5, immersing the nascent film into a coagulating bath at 40 ℃ after passing through an air bath for 0.5S, and after staying for 2S, rinsing the film in a rinsing tank and then rolling.
Fig. 10 shows a scanning electron microscope image of the inner surface of the reinforced polyvinylidene fluoride hollow fiber membrane provided in comparative example 3 of the present invention, and as shown in fig. 10, the inner surface has a problem that the casting solution permeates into the hollow woven tube, and the production process has a problem that the casting solution blocks the inner pore canal of the hollow woven tube.
The hollow fiber membranes prepared in examples 1 to 9 and comparative examples 1 to 3 were subjected to performance test by the following experimental tests:
1. pure water flux test:
intercepting a hollow fiber membrane with the length of 30cm, measuring the pure water permeation quantity in unit time and unit membrane area at the temperature of 25+/-1 ℃ and the pressure of 0.1MPa, and calculating the pure water flux by the following formula from the outside to the inside of the membrane wires.
Wherein J is w For pure water flux, L/(m) 2 H); v is the water production per unit timeAn amount, L; a is the effective filtration area, m 2 The method comprises the steps of carrying out a first treatment on the surface of the Delta T is the test time, h.
2. Peel strength test:
peel strength test sample preparation: a film sheet ranging from 3mm by 1cm was taken from the hollow fiber film, and a plastic plate with an adhesive was bonded to the film sheet to form a test sample of plastic plate-adhesive-film layer-hollow woven tube-adhesive-plastic plate structure. The plastic plate in the test sample was held by a jig of a universal tensile machine, the test height was set to 1cm, the stretching speed was 1mm/min, and 5 or more tests were performed, and the average value was taken as the peel strength (MPa) of the film wire.
3. Film thickness test: the film thickness was measured using an electron microscope at 200 times.
4. And (3) testing the viscosity of the casting solution: the melting temperature was 200℃and the rotor No. 2, 30rpm, using a rotational viscometer with a hot stage.
5. Bubble point test: the gas pressure at which the first series of bubbles appeared in the water was recorded as bubble point (MPa) by pumping air into the fully wetted hollow fiber membranes and slowly increasing the gas pressure under full immersion in pure water.
6. Hollow woven tube surface void area test: the hollow woven tube surface pore area was tested by electron microscopy at 50-fold.
Table 1 shows the performance indexes obtained by the above experimental tests of the hollow fiber membranes shown in examples 1 to 9 and comparative examples 1 to 3.
TABLE 1 hollow fiber membrane Performance index shown in examples 1-9, comparative examples 1-3
As shown in table 1, from the comparison results of the performance indexes of example 1 and comparative example 1, it can be seen that, under the condition that other conditions are not changed, the hollow woven tube woven by the fully drawn yarn FDY yarn is adopted in comparative example 1, the hollow woven tube woven by the draw textured yarn DTY and the fully drawn yarn FDY composite yarn is adopted in example 1, and the two reinforced polyvinylidene fluoride hollow fiber membranes formed by combining the polyvinylidene fluoride high-temperature homogeneous phase casting solution have obvious differences in peel strength, and the peel strength of example 1 is significantly better than that of comparative example 1.
As shown in table 1, from the comparison results of the performance indexes of example 1 and comparative example 2, it can be seen that, under the condition that other conditions are not changed, in comparative example 2, a hollow woven tube woven by a drawn textured yarn DTY and a fully drawn yarn FDY composite yarn is co-extruded with a casting solution at normal temperature, and the casting solution is converged at the outlet of the annular spinneret to form a reinforced hollow fiber membrane, wherein the casting solution forms a porous membrane layer through a non-solvent induced phase separation process. The reinforced hollow fiber membrane in example 1 is formed by simultaneously extruding a hollow woven tube woven by a draw textured yarn DTY and a fully drawn yarn FDY composite yarn and a high-temperature casting solution at 190-250 ℃ and converging the casting solution at the outlet of an annular spinneret, wherein the casting solution forms a porous membrane layer through a thermally induced phase separation process. Compared with the embodiment 1, the bubble point of the reinforced hollow fiber membrane in the comparative example 2 is obviously reduced mainly because the raised yarn ends exist on the surface of the hollow woven tube woven by the draw textured yarn DTY and the fully drawn yarn FDY composite yarn, and defects can be caused on the surface of the reinforced hollow fiber membrane when no surface heat treatment process exists, so that the bubble point is reduced, and the filtering effect is reduced. Example 1 does not have such problems.
As shown in table 1, from the comparison results of the performance indexes of example 1 and comparative example 3, it can be seen that the comparative example 3 uses a hollow woven tube woven by fully drawn yarn FDY yarn under the condition that other conditions are not changed, and the reinforced hollow fiber membrane is obtained by a non-solvent induced phase separation process under the condition of normal temperature. Example 1 a hollow woven tube was crocheted with draw textured yarn DTY and fully drawn yarn FDY composite yarn and was subjected to a thermally induced phase separation process at 190-250 ℃ to obtain a reinforced hollow fiber membrane. The reinforced hollow fiber membrane of comparative example 3 has a problem of poor peel strength and low bubble point compared with example 1. Example 1 is significantly better than comparative example 3.
Performance of the reinforced polyvinylidene fluoride hollow fiber membranes from comparative examples 1 to 3
It can be seen that the film wire has the disadvantages of low peel strength, poor integrity and the like.
Compared with the comparative examples, the reinforced polyvinylidene fluoride hollow fiber membranes provided in examples 1 to 8 of the present invention have the following advantages:
(1) Because the surface of the hollow woven tube layer is provided with fluffy yarns and protruding yarn ends, the special structure can be mutually penetrated with high-temperature casting film liquid to obtain the reinforced hollow fiber membrane with high peel strength.
(2) The high-temperature casting solution can enable the protruding yarn ends on the surface of the hollow woven tube to be softened rapidly, so that the defect of macropores of the porous membrane layer due to penetrability of the protruding yarn ends is avoided, and the reinforced hollow fiber membrane with good integrity is obtained.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, one skilled in the art can combine and combine the different embodiments or examples described in this specification.
For the purposes of simplicity of explanation, the methodologies are shown as a series of acts, but one of ordinary skill in the art will recognize that the present invention is not limited by the order of acts described, as some acts may, in accordance with the present invention, occur in other orders and concurrently. Further, those skilled in the art will recognize that the embodiments described in the specification are all of the preferred embodiments, and that the acts and components referred to are not necessarily required by the present invention.
The reinforced polyvinylidene fluoride hollow fiber membrane and the preparation method thereof provided by the invention are described in detail, and specific examples are applied to illustrate the principle and the implementation mode of the invention, and the description of the examples is only used for helping to understand the method and the core idea of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (10)
1. The reinforced polyvinylidene fluoride hollow fiber membrane is characterized by comprising a hollow woven tube and a polyvinylidene fluoride porous membrane layer wrapped outside the woven tube; wherein,
the hollow woven tube and the polyvinylidene fluoride porous membrane are mutually penetrated to form a transition layer;
the hollow crochet tube is formed by crocheting single-strand composite yarns, and the single-strand composite yarns are formed by composite spinning of textured yarns and fully drawn yarns FDY, wherein the total number of the textured yarns is 50-100;
the thickness of the membrane layer of the reinforced polyvinylidene fluoride hollow fiber membrane is 0.1-0.2mm; wherein the thickness of the transition layer is 20-80 mu m.
2. The reinforced polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein in the single-strand composite yarn, the textured yarn and the fully drawn yarn FDY are made of polyester;
the ratio of the number of the textured yarns to the number of the fully drawn yarns FDY is (2:8) - (5:5);
the textured yarn is a stretch textured yarn DTY or an air textured yarn ATY.
3. The hollow woven tube of claim 1, wherein the textured yarn and fully drawn yarn FDY in the single ply composite yarn have a diameter of 10-20 μm.
4. The reinforced polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the hollow woven tube is not heat-set, and the yarn on the outer surface thereof is relaxed and there are protruding yarn ends;
the number of the crochet needles is 10-14, and the crochet density is 20-26;
the outer diameter of the hollow woven tube is 1.1-1.8mm;
the pore area of the hollow woven tube is 0.02-0.04mm 2 ；
The tensile strength of the hollow woven tube is 80-150N.
5. The reinforced polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the tensile strength of the polyvinylidene fluoride porous membrane layer is not less than 5.0MPa, and the peel strength of the hollow woven tube and the polyvinylidene fluoride porous membrane layer is 3.0-4.5MPa.
6. A method for preparing the reinforced polyvinylidene fluoride hollow fiber membrane according to any one of claims 1 to 5, comprising the steps of:
s1, preparing a composite yarn from 50-100 textured yarns and fully drawn yarns FDY according to the root ratio of (2:8) - (5:5) by a composite winding process;
s2, crocheting the composite yarns into hollow crocheted pipes by means of a crocheting machine, and winding the hollow crocheted pipes into discs without a heat setting device;
s3, uniformly mixing polyvinylidene fluoride and a diluent, and heating to 190-250 ℃ to form a homogeneous phase high Wen Zhu membrane solution;
s4, extruding the hollow woven tube and the homogeneous high-temperature casting film liquid simultaneously, and converging at an outlet of an annular spinneret to form a primary film with an inner layer of the hollow woven tube and an outer layer of the homogeneous high-temperature casting film liquid;
s5, immersing the primary membrane in an air bath of 0.1-0.5S, cooling in a water bath of 40-60 ℃, standing for 2-3S, forming the polyvinylidene fluoride porous membrane layer by the high-temperature membrane casting liquid on the outer layer through a phase separation method, and winding to obtain a solidified hollow fiber membrane;
s6, removing the diluent in the solidified hollow fiber membrane by using ethanol to obtain the reinforced polyvinylidene fluoride hollow fiber membrane.
7. The method according to claim 6, wherein in step S1, the textured yarn is a textured stretch yarn DTY or an air textured yarn ATY.
8. The method according to claim 6, wherein in step S2, the number of the crocheted needles is 10-14, the crocheted density is 20-26, so as to regulate the outer diameter of the hollow crocheted tube formed by the crocheted to be 1.1-1.8mm and the pore area to be 0.02-0.04mm 2 。
9. The method according to claim 6, wherein the content of the diluent in the homogeneous high temperature casting solution is 70-82wt%;
the diluent is one or more of diphenyl ketone, methyl benzoate, ethyl benzoate, diethyl phthalate and glyceryl triacetate.
10. The method according to claim 6, wherein in step S3, the polyvinylidene fluoride has a molecular weight of 30 to 50 kilodaltons;
the viscosity of the homogeneous high-temperature casting film liquid is 200-1000 mPa.s.
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