CN116726738A - Polyvinylidene fluoride hollow fiber membrane with easily-cleaned pore structure and preparation method thereof - Google Patents
Polyvinylidene fluoride hollow fiber membrane with easily-cleaned pore structure and preparation method thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 118
- 239000002033 PVDF binder Substances 0.000 title claims abstract description 104
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 104
- 239000011148 porous material Substances 0.000 title claims abstract description 90
- 239000012510 hollow fiber Substances 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000007788 liquid Substances 0.000 claims abstract description 98
- 230000003670 easy-to-clean Effects 0.000 claims abstract description 22
- 238000009987 spinning Methods 0.000 claims abstract description 8
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 96
- 239000004594 Masterbatch (MB) Substances 0.000 claims description 50
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 48
- 238000000034 method Methods 0.000 claims description 34
- 238000002156 mixing Methods 0.000 claims description 29
- 238000003756 stirring Methods 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 21
- 239000011347 resin Substances 0.000 claims description 19
- 229920005989 resin Polymers 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 18
- 239000000654 additive Substances 0.000 claims description 15
- 230000000996 additive effect Effects 0.000 claims description 15
- 230000004048 modification Effects 0.000 claims description 12
- 238000012986 modification Methods 0.000 claims description 12
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 claims description 11
- 239000000022 bacteriostatic agent Substances 0.000 claims description 10
- 229920001661 Chitosan Polymers 0.000 claims description 8
- ABDBNWQRPYOPDF-UHFFFAOYSA-N carbonofluoridic acid Chemical compound OC(F)=O ABDBNWQRPYOPDF-UHFFFAOYSA-N 0.000 claims description 8
- -1 polyhexamethylene guanidine Polymers 0.000 claims description 6
- 239000004094 surface-active agent Substances 0.000 claims description 5
- VAZJLPXFVQHDFB-UHFFFAOYSA-N 1-(diaminomethylidene)-2-hexylguanidine Polymers CCCCCCN=C(N)N=C(N)N VAZJLPXFVQHDFB-UHFFFAOYSA-N 0.000 claims description 4
- 229920002413 Polyhexanide Polymers 0.000 claims description 4
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 claims description 2
- 239000004480 active ingredient Substances 0.000 claims description 2
- 150000001278 adipic acid derivatives Chemical class 0.000 claims description 2
- 238000005054 agglomeration Methods 0.000 claims description 2
- 230000002776 aggregation Effects 0.000 claims description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical class OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 2
- 150000002148 esters Chemical class 0.000 claims description 2
- 238000007667 floating Methods 0.000 claims description 2
- 238000005469 granulation Methods 0.000 claims description 2
- 230000003179 granulation Effects 0.000 claims description 2
- 229920001519 homopolymer Polymers 0.000 claims description 2
- 239000000155 melt Substances 0.000 claims description 2
- 150000004812 organic fluorine compounds Chemical class 0.000 claims description 2
- 235000012424 soybean oil Nutrition 0.000 claims description 2
- 239000003549 soybean oil Substances 0.000 claims description 2
- 238000005507 spraying Methods 0.000 claims description 2
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 2
- 235000013311 vegetables Nutrition 0.000 claims description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims 1
- 229910052731 fluorine Inorganic materials 0.000 claims 1
- 239000011737 fluorine Substances 0.000 claims 1
- 239000002994 raw material Substances 0.000 abstract description 7
- 230000000903 blocking effect Effects 0.000 abstract description 2
- 238000001914 filtration Methods 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 126
- 239000000843 powder Substances 0.000 description 25
- 239000000126 substance Substances 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 10
- DOOTYTYQINUNNV-UHFFFAOYSA-N Triethyl citrate Chemical compound CCOC(=O)CC(O)(C(=O)OCC)CC(=O)OCC DOOTYTYQINUNNV-UHFFFAOYSA-N 0.000 description 10
- 239000001069 triethyl citrate Substances 0.000 description 10
- VMYFZRTXGLUXMZ-UHFFFAOYSA-N triethyl citrate Natural products CCOC(=O)C(O)(C(=O)OCC)C(=O)OCC VMYFZRTXGLUXMZ-UHFFFAOYSA-N 0.000 description 10
- 235000013769 triethyl citrate Nutrition 0.000 description 10
- 238000009835 boiling Methods 0.000 description 8
- 238000002145 thermally induced phase separation Methods 0.000 description 7
- 125000002057 carboxymethyl group Chemical group [H]OC(=O)C([H])([H])[*] 0.000 description 6
- 239000007921 spray Substances 0.000 description 6
- 238000005303 weighing Methods 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- 230000004907 flux Effects 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 238000009775 high-speed stirring Methods 0.000 description 5
- 230000010354 integration Effects 0.000 description 5
- 239000003960 organic solvent Substances 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000005191 phase separation Methods 0.000 description 3
- 239000002356 single layer Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- RGHNJXZEOKUKBD-SQOUGZDYSA-M D-gluconate Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O RGHNJXZEOKUKBD-SQOUGZDYSA-M 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 229940050410 gluconate Drugs 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 239000012567 medical material Substances 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Artificial Filaments (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The application relates to an easy-to-clean porous structure polyvinylidene fluoride hollow fiber membrane which comprises an outer membrane structure and an inner membrane structure, wherein feed liquid is prepared by a thermally induced phase spinning process, and is synchronously and respectively extruded by two double-screw extruders and respectively molded by two layers of dies, the pore structures of the outer membrane structure and the inner membrane structure have different pore diameters, and the pore diameter of the pore structure of the inner membrane structure is larger than that of the pore structure of the outer membrane structure. The application also provides a preparation method of the polyvinylidene fluoride hollow fiber membrane with the easily-cleaned pore structure. The application uses the same thermally induced phase membrane preparation process, ensures the effective combination of the inner layer membrane raw material and the outer layer membrane raw material from the source, avoids the membrane layering problem, and has adjustable aperture; the application changes the structure form of the traditional hollow fiber membrane with a single pore structure, and effectively avoids the problem that the membrane product is difficult to clean after running and blocking by forming two layers of pore structures which are uniform in size and have filtration pore diameters which are changed from outside to inside.
Description
Technical Field
The application belongs to the technical field of high polymer materials, and particularly relates to a polyvinylidene fluoride hollow fiber membrane with an easily-cleaned pore structure and a preparation method thereof.
Background
The membrane separation technology is one of the separation technologies which are rapidly developed in recent 30 years, and meanwhile, the separation precision is high in controllability, the separation effect is good and stable, and the membrane separation technology is widely applied to various aspects such as sewage deep treatment, medical materials and the like.
The polyvinylidene fluoride has the characteristics of outstanding chemical resistance, high temperature resistance and stable property, and provides various choices for the processing mode, so that the polyvinylidene fluoride is a main raw material of the ultra-micro filter membrane. However, the ultra-micro filtration membrane with uniform pore diameter has the problems of microbial pollution and cleaning recovery after pollution in the use process.
The polyvinylidene fluoride hollow fiber membrane mainly comprises two preparation technical systems: a method based on the non-solvent induced phase separation principle is characterized by simple equipment, low processing temperature, convenient addition of various modification aids and easy formation of different pore diameter structures, but the membrane prepared by the method has low strength, thin functional skin layer, easy damage and short service life; the other is a thermally induced phase separation method, which utilizes the characteristics of high-temperature compatibility and low-temperature phase separation of resin and diluent to prepare a homogeneous porous membrane, and the membrane prepared by the method has the characteristics of high strength, good chemical resistance, uniform pore diameter and the like, so that the service life of the membrane is greatly prolonged, and the thermally induced phase separation method is gradually a leading preparation technology of a new generation of PVDF porous membrane.
However, although the thermal phase separation method is used for preparing the hollow fiber membrane product, the physical and chemical properties are excellent, the prior thermal phase membrane preparation process mostly adopts a single-layer membrane pore structure membrane, the pore diameter is uniform, the use process is easy to be blocked, and the membrane is difficult to clean after being blocked, so that the service life of the membrane is finally influenced. Attempts have also been made to remedy the problem of insufficient single pore size by adding non-solvent phase-inducing membrane liquid to the outer side of the thermal phase-inducing membrane pores, but the lamination problem is caused by the unstable adhesion of the two different membrane-making processes, and the quality and the service life of the membrane filaments cannot be ensured in the attempt.
The inventor also tries to make up the problem of single aperture by adopting a thermally induced phase high-temperature melting raw material coating mode on the surface of a single-layer membrane pore structure membrane after forming, but because two layers of feed liquid are formed asynchronously, the problems of original single-layer pore structure blockage and uneven coating caused by the coating feed liquid after forming are generated, and the pore structure size cannot be effectively controlled and the membrane yarn quality is ensured.
Disclosure of Invention
In order to overcome the defects in the prior art, it would be advantageous to provide a polyvinylidene fluoride hollow fiber membrane with an easy-to-clean pore structure and a preparation method thereof.
To this end, according to a first aspect of the present application, there is provided an easy-to-clean pore-structured polyvinylidene fluoride hollow fiber membrane comprising an outer layer membrane structure and an inner layer membrane structure, each of which is prepared by a thermally induced phase spinning process and simultaneously and separately extruded by two twin screw extruders and separately molded by two dies, wherein the pore structures of the outer layer membrane structure and the inner layer membrane structure have different pore diameters, and the pore diameter of the pore structure of the inner layer membrane structure is larger than the pore diameter of the pore structure of the outer layer membrane structure.
Further, the feed liquid composition of the inner layer film structure is as follows: the modified master batch, polyvinylidene fluoride resin and organic liquid are controlled within the weight ratio of 1:1:1-1:1:2, wherein the modified master batch comprises the following components in percentage by weight:
polyvinylidene fluoride: 10-15%;
nano calcium carbonate: 50-60%;
macromolecular bacteriostatic agent: 20-30%;
modification additive: 1-5%;
the feed liquid composition of the outer layer film structure is as follows: the weight ratio of the modified master batch to the polyvinylidene fluoride resin to the organic liquid is controlled within the range of 1:1:1-1:1:3; wherein the modified master batch comprises the following components in percentage by weight:
polyvinylidene fluoride: 15-25%;
nano calcium carbonate: 45-50%;
macromolecular bacteriostatic agent: 20-34%;
modification additive: 1-5%.
Still further, the feed liquid of the inner layer film structure is melted, mixed and extruded by a double screw extruder at 180-230 ℃;
melting, mixing and extruding the feed liquid with the outer layer film structure through a double-screw extruder at the temperature of 200-230 ℃;
and extruding the feed liquid of the inner layer film structure and the feed liquid of the outer layer film structure through two double-screw extruders, spraying the feed liquid from two layers of mouth molds through metering pumps, cooling, forming and stretching for 1.5-2.5 times, and extracting the organic liquid and nano calcium carbonate in the inner layer film structure and the outer layer film structure to prepare the polyvinylidene fluoride hollow fiber membrane with the easy-cleaning pore structure.
Further, the polyvinylidene fluoride is a high molecular weight polyvinylidene fluoride, preferably a vinylidene fluoride homopolymer, and has a Melt Flow Rate (MFR) of 1 to 4g/10min (230 ℃/21.6 kg).
Still further, the organic liquid is selected from the group consisting of synthetic vegetable esters, citric acid esters, adipic acid esters, and soybean oil.
In addition, the nano calcium carbonate is in a cubic-like shape, and the average particle size is 20-150 nanometers.
Still further, the polymeric bacteriostat is one or a mixture of polyhexamethylene guanidine (PHMG), polyhexamethylene biguanide (PHMB), chitosan and derivatives thereof with a weight average molecular weight of more than 20000.
Still further, the polymeric bacteriostat is preferably a liquid preparation with 25-50% of the active ingredients.
In addition, the modified additive is a high-temperature resistant surfactant, and is mainly used for improving the wetting and adsorbing effects of the nano calcium carbonate and the macromolecular bacteriostatic agent preparation.
Still further, the modifying additive is preferably an organofluorine-based surfactant solution, such as a perfluorosulfonate or perfluorocarboxylic acid.
According to another aspect of the present application, there is provided a method for preparing the polyvinylidene fluoride hollow fiber membrane with easy-to-clean pore structure, comprising the steps of:
(1) Preparing modified master batches in the feed liquid of the inner layer film structure by mixing and extruding, wherein the modified master batches comprise the following components in percentage by weight:
polyvinylidene fluoride: 10-15%;
nano calcium carbonate: 50-60%;
macromolecular bacteriostatic agent: 20-30%;
modification additive: 1-5%;
(2) Preparing modified master batches in the feed liquid of the outer layer film structure by mixing and extruding, wherein the modified master batches comprise the following components in percentage by weight:
polyvinylidene fluoride: 15-25%;
nano calcium carbonate: 45-50%;
macromolecular bacteriostatic agent: 20-34%;
modification additive: 1-5%;
(3) Preparing an inner layer film structure feed liquid and homogenizing, wherein the inner layer film structure feed liquid comprises a modified master batch, polyvinylidene fluoride resin and organic liquid, and the weight ratio of the modified master batch to the polyvinylidene fluoride resin is controlled within the range of 1:1:1-1:1:2;
(4) Preparing an outer layer film structure feed liquid and homogenizing, wherein the outer layer film structure feed liquid comprises a modified master batch, polyvinylidene fluoride resin and organic liquid, and the weight ratio of the modified master batch to the polyvinylidene fluoride resin is controlled within the range of 1:1:1-1:1:3;
(5) The homogenized inner layer film structure feed liquid and outer layer film structure feed liquid are extruded by two twin-screw extruders continuously and simultaneously, and are sprayed out synchronously by two layers of mouth molds after passing through a metering pump, and after cooling forming and stretching for 1.5-2.5 times, organic liquid and nano calcium carbonate are extracted, so that the polyvinylidene fluoride hollow fiber membrane with the easily-cleaned pore structure is prepared;
the feed liquid with the inner layer film structure is melted, mixed and extruded by a double screw extruder at 180-230 ℃; and (3) melting, mixing and extruding the feed liquid with the outer layer film structure through a double-screw extruder at the temperature of 200-230 ℃.
Further, the preparation of the modified master batch comprises the following steps:
1) The nano calcium carbonate passes through a 325-mesh mechanical sieve to eliminate large soft agglomeration;
2) Adding nano calcium carbonate and a modifying additive into a high-speed mixer for surface pretreatment;
3) Adding the pretreated nano calcium carbonate and the high-molecular bacteriostat into a stirring kettle, stirring at a high speed, and simultaneously carrying out ultrasonic dispersion, and treating for 10-50 min;
4) Adding polyvinylidene fluoride, stirring for 30min, mixing by a double-screw extruder, wherein the mixing temperature is 180-200 ℃, simultaneously adopting multi-stage vacuumizing to discharge volatile matters, the vacuum degree is minus 0.2 to minus 0.8bar, extruding the mixture, performing water cooling or air cooling granulation, and removing surface floating water to obtain modified master batch.
Further, during water cooling, the water cooling temperature is controlled to be 15-35 ℃, and the water cooling particles are dried at 80 ℃; when in air cooling, the air is cooled at normal temperature, and the wind speed is matched according to the yield.
Compared with the prior art, the application has the following beneficial effects:
1) Compared with the traditional thermally induced phase separation method, the application changes the structure form of the hollow fiber membrane with the single pore structure in the past by simultaneously forming the outer layer membrane structure and the inner layer membrane structure with different pore structures, namely, the application effectively avoids the problem that the membrane product is difficult to clean after running and blocking by forming two layers of hollow fiber membrane structure forms which are uniform in size and are arranged in the pore structure with the filtration pore diameters from outside to inside;
2) The application uses the same thermally induced phase membrane preparation process, ensures the effective combination of the inner layer membrane raw material and the outer layer membrane raw material from the source, avoids the membrane layering problem, and extracts the organic liquid and the nano calcium carbonate after cooling and molding to prepare the hollow fiber membrane with two layers of different pore diameter membrane structures;
3) According to the application, the two double-screw extruders extrude simultaneously, and the metering pump and the two layers of mouth molds synchronously spray out, so that the operation is convenient, the raw material proportion of each layer of film structure and the corresponding extrusion process (such as mixing temperature) are favorably adjusted, the size of the formed film hole structure is effectively ensured, and the aperture is adjustable according to the requirement;
4) The modified master batch prepared by the application is a high dispersion taking nano calcium carbonate as a carrier, and is used in a manner that the high dispersion is directly and continuously weighted with matrix polyvinylidene fluoride resin, organic liquid and the like according to a proportion, and is added into a double-screw extruder, so that a polyvinylidene fluoride hollow fiber membrane is prepared by a thermally induced phase separation method, and compared with the traditional directly blended thermally induced phase separation method for preparing a porous membrane, the porous membrane has stronger membrane preparation continuity, is more convenient for large-scale amplification, and meanwhile, some substances which cannot be directly added into a blending system can be selected in a final membrane preparation formula, so that the selectivity of formula components is greatly expanded, and meanwhile, the diversity of modification directions of the porous membrane based on the thermally induced phase separation method is expanded;
5) The high molecular weight polyvinylidene fluoride resin selected by the application is used as master batch molding support matrix resin, and when the high molecular weight polyvinylidene fluoride resin is added into the polyvinylidene fluoride resin which is conventionally suitable for preparing films by a thermally induced phase separation method for mixing and preparing films, the modified master batch is well compatible with the polyvinylidene fluoride resin, the strength of the porous film can be improved, and the pore forming performance is not influenced.
These and other aspects of the application will be apparent from and elucidated with reference to the embodiments described hereinafter.
Detailed Description
The present application will be described in detail with reference to examples.
Example 1
First), preparing modified master batch for feed liquid with inner layer membrane structure: grinding nano calcium carbonate, passing through a 325-mesh screen, adding the ground and sieved powder into a high-speed mixer, stirring, adding the perfluorosulfonate solution serving as a modification additive into the nano calcium carbonate in a spray form, and stirring at a high speed for 10min; then transferring the pretreated powder to an ultrasonic processor with high-speed stirring, adding PHMG (PH) (namely polyhexamethylene guanidine phosphate, polyhexamethylene guanidine derivative) aqua, stirring for 20min under the ultrasonic condition of 30KHZ, adding high molecular weight polyvinylidene fluoride powder with MFR of 2.0g/10min (230 ℃,21.6 kg), and stirring uniformly; and then the mixture is led into a double-screw extruder to be mixed at the temperature of 195 ℃, and simultaneously micromolecular volatile matters (namely water vapor and low boiling point substances) are discharged through multistage vacuumizing, wherein the vacuum degree is-0.3 to-0.7 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 10 percent of
Nano calcium carbonate: 60 percent of
PHMG (PH) aqua: 29%
Perfluorosulfonate solution: 1%
And II) preparing the modified master batch for the feed liquid with the outer layer membrane structure by comparing the method for preparing the modified master batch for the feed liquid with the inner layer membrane structure: introducing the mixture into another twin-screw extruder, mixing at 210 ℃, and simultaneously discharging micromolecular volatile matters (namely water vapor and low-boiling point substances) by multi-stage vacuumizing, wherein the vacuum degree is-0.5 to-0.8 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 25 percent of
Nano calcium carbonate: 45%
PHMG (PH) aqua: 25 percent of
Perfluorosulfonate solution: 5%
Thirdly), preparing the polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure: adding the modified master batch of the upper inner layer film structure feed liquid, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder in a weighing feeding mode according to the proportion of 1:1:1.5 by using a system of a double-screw extruder serial metering pump, mixing at 195 ℃, and extruding through one layer of an annular two-layer die (a film wire forming die); simultaneously, a system of a double-screw extruder serial metering pump is used for adding modified master batch in the feed liquid with the outer layer film structure, polyvinylidene fluoride powder and triethyl citrate into the double-screw extruder in a weighing feeding mode according to the proportion of 1:1:2, and extruding the other layer of the feed liquid through the annular two-layer die after mixing at 210 ℃; and synchronously extruding the feed liquid with the inner layer film structure and the feed liquid with the outer layer film structure, synchronously cooling to form a hollow fiber film, stretching for 2 times, and then extracting the organic solvent and nano calcium carbonate from the hollow fiber film by using ethanol and hydrochloric acid, wherein the two layers of feed liquid flow stably in the whole thermally induced phase spinning process (namely, the forming process), and the pore diameter is changed from small to large (namely, the pore diameters of the two layers are different, and the pore diameter of each layer is uniform), so that the polyvinylidene fluoride hollow fiber film with the easily-cleaned pore structure is obtained.
Fourth), performance detection: the prepared polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure has the pure water flux of 900L/(. Square meter) h at 25 ℃ and 0.1Mpa, the tensile breaking strength of 15Mpa, the breaking elongation of 100%, the maximum pore diameter of an inner layer of 0.2um, the maximum pore diameter of an outer layer of 0.1um and the porosity of 79% measured by a bubble pressure method, and the obvious connecting trace of the inner layer and the outer layer can not be seen through an electron microscope structure photo, so that the integration is obvious.
Example two
First), preparing modified master batch for feed liquid with inner layer membrane structure: grinding nano calcium carbonate, passing through a 325-mesh screen, adding the ground and sieved powder into a high-speed mixer, stirring, adding the perfluorocarboxylic acid solution into the nano calcium carbonate in a spray mode, and stirring at a high speed for 10min; then transferring the pretreated powder to an ultrasonic processor with high-speed stirring, adding a carboxymethyl chitosan water agent, stirring for 20min under the condition of 30KHZ, adding high-molecular weight polyvinylidene fluoride powder with MFR of 2.0g/10min (230 ℃ and 21.6 kg), and uniformly stirring; and then the mixture is led into a double-screw extruder to be mixed at 180 ℃, and simultaneously micromolecular volatile matters (namely water vapor and low boiling point substances) are discharged through multistage vacuumizing, wherein the vacuum degree is-0.4 to-0.7 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 15%
Nano calcium carbonate: 50 percent of
Carboxymethyl chitosan aqua: 30%
Perfluorocarboxylic acid solution: 5%
And II) preparing modified master batches for the feed liquid with the outer layer membrane structure by comparing the modified master batches for the feed liquid with the inner layer membrane structure prepared by the method: introducing the mixture into another twin-screw extruder, mixing at 200deg.C, and vacuumizing for several stages to discharge small molecular volatile components (i.e. water vapor and low boiling point substances), wherein the vacuum degree is-0.5 to-0.8 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 15%
Nano calcium carbonate: 50 percent of
Carboxymethyl chitosan aqua: 34%
Perfluorocarboxylic acid solution: 1%
Thirdly), preparing the polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure: adding the modified master batch of the upper inner layer film structure feed liquid, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder by adopting a metering feeding mode according to the proportion of 1:1:2 by using a system of a double-screw extruder serial metering pump, mixing at 180 ℃, and extruding through one layer of annular two-layer mouth molds; adding modified master batch in the feed liquid with the outer layer film structure, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder in a weighing feeding mode according to the proportion of 1:1:3 by using a system of a double-screw extruder serial metering pump, mixing at 200 ℃, and extruding the other layer through an annular two-layer die; and (3) synchronously extruding the feed liquid of the inner layer film structure and the feed liquid of the outer layer film structure, synchronously cooling to form a hollow fiber film, stretching for 2 times, and then extracting the organic solvent and the nano calcium carbonate from the hollow fiber film by using ethanol and hydrochloric acid, wherein in the whole thermally induced phase spinning forming process, the two layers of feed liquid flow stably, and the aperture is changed from outside to inside from small to large (namely, the apertures of the two layers are different, and the aperture size of each layer is uniform), so that the polyvinylidene fluoride hollow fiber film with the easily-cleaned pore structure is obtained.
Fourth), performance detection: the prepared polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure has pure water flux of 1000L/(. Square meter) h at 25 ℃ and 0.1Mpa, tensile breaking strength of 14Mpa, elongation at break of 120%, maximum pore diameter of an inner layer of 0.25um, maximum pore diameter of an outer layer of 0.15um and porosity of 80% measured by a bubble pressure method, and obvious connecting marks of the inner layer and the outer layer are not visible through an electron microscope structure photo, so that the integration is obvious.
Example III
First), preparing modified master batch for feed liquid with inner layer membrane structure: grinding nano calcium carbonate, passing through a 325-mesh screen, adding the ground and sieved powder into a high-speed mixer, stirring, adding the perfluorocarboxylic acid solution into the nano calcium carbonate in a spray mode, and stirring at a high speed for 10min; then transferring the pretreated powder to an ultrasonic processor with high-speed stirring, adding PHMG (GL) (namely, polyhexamethylene guanidine gluconate, a derivative of polyhexamethylene guanidine) aqua, stirring for 20min at 30KHZ, adding high molecular weight polyvinylidene fluoride powder with MFR of 2.0g/10min (230 ℃,21.6 kg), and uniformly stirring; and then the mixture is led into a double-screw extruder to be mixed at 200 ℃, and simultaneously micromolecular volatile matters (namely water vapor and low boiling point substances) are discharged through multistage vacuumizing, wherein the vacuum degree is-0.5 to-0.8 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 15%
Nano calcium carbonate: 55%
PHMG (GL) aqua: 25 percent of
Perfluorocarboxylic acid solution: 5%
And II) preparing modified master batches for the feed liquid with the outer layer membrane structure by comparing the modified master batches for the feed liquid with the inner layer membrane structure prepared by the method: introducing the mixture into another twin-screw extruder, mixing at 210 ℃, and simultaneously discharging micromolecular volatile matters (namely water vapor and low-boiling point substances) by multi-stage vacuumizing, wherein the vacuum degree is-0.4 to-0.7 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 25 percent of
Nano calcium carbonate: 50 percent of
PHMG (GL) aqua: 20 percent of
Perfluorocarboxylic acid solution: 5%
Thirdly), preparing the polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure: adding the modified master batch of the upper inner layer film structure feed liquid, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder by adopting a metering feeding mode according to the proportion of 1:1:1 by using a system of a double-screw extruder serial metering pump, mixing at 200 ℃, and extruding through one layer of annular two-layer mouth molds; adding modified master batch in the feed liquid with the outer layer film structure, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder in a weighing feeding mode according to the proportion of 1:1:2 by using a system of a double-screw extruder serial metering pump, mixing at 210 ℃, and extruding the other layer through an annular two-layer die; and (3) synchronously extruding the feed liquid of the inner layer film structure and the feed liquid of the outer layer film structure, synchronously cooling to form a hollow fiber film, stretching for 2.5 times, and then extracting the organic solvent and the nano calcium carbonate from the hollow fiber film by using ethanol and hydrochloric acid, wherein in the whole thermally induced phase spinning forming process, the two layers of feed liquid flow stably, and the pore diameters are changed from outside to inside from small to large (namely, the pore diameters of the two layers are different, and the pore diameters of each layer are uniform), so that the polyvinylidene fluoride hollow fiber film with the easily-cleaned pore structure is obtained.
Fourth), performance detection: the prepared polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure has the pure water flux of 1300L/(. Square meter) h at 25 ℃ and 0.1Mpa, the tensile breaking strength of 16Mpa, the breaking elongation of 110%, the maximum pore diameter of an inner layer of 0.15um, the maximum pore diameter of an outer layer of 0.10um and the porosity of 78% measured by a bubble pressure method, and the obvious connecting trace of the inner layer and the outer layer can not be seen through an electron microscope structure photo, so that the integration is obvious.
Example IV
First), preparing modified master batch for feed liquid with inner layer membrane structure: grinding nano calcium carbonate, passing through a 325-mesh screen, adding the ground and sieved powder into a high-speed mixer, stirring, adding the perfluorosulfonate solution into the nano calcium carbonate in a spray form, and stirring at a high speed for 10min; then transferring the pretreated powder to an ultrasonic processor with high-speed stirring, adding a carboxymethyl chitosan water agent, stirring for 20min under the condition of 30KHZ, adding high-molecular weight polyvinylidene fluoride powder with MFR of 2.0g/10min (230 ℃ and 21.6 kg), and uniformly stirring; and then the mixture is led into a double-screw extruder, mixed at 220 ℃, and simultaneously the small molecular volatile matters are discharged through multistage vacuumizing, wherein the vacuum degree is-0.4 to-0.7 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 15%
Nano calcium carbonate: 60 percent of
Carboxymethyl chitosan aqua: 20 percent of
Perfluorosulfonate solution: 5%
And II) preparing modified master batches for the feed liquid with the outer layer membrane structure by comparing the modified master batches for the feed liquid with the inner layer membrane structure prepared by the method: introducing the mixture into another twin-screw extruder, mixing at 230 ℃, and simultaneously discharging micromolecular volatile matters (namely water vapor and low boiling point substances) by multi-stage vacuumizing, wherein the vacuum degree is-0.5 to-0.9 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 20 percent of
Nano calcium carbonate: 50 percent of
Carboxymethyl chitosan aqua: 28%
Perfluorosulfonate solution: 2%
Thirdly), preparing the polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure: adding the modified master batch of the upper inner layer film structure feed liquid, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder by adopting a metering feeding mode according to the proportion of 1:1:1.5 by using a system of a double-screw extruder serial metering pump, mixing at 220 ℃, and extruding through one layer of annular two-layer mouth molds; adding modified master batch in the feed liquid with the outer layer film structure, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder in a weighing feeding mode according to the proportion of 1:1:2 by using a system of a double-screw extruder serial metering pump, mixing at 230 ℃, and extruding the other layer through an annular two-layer die; and (3) synchronously extruding the feed liquid with the inner layer film structure and the feed liquid with the outer layer film structure, synchronously cooling to form a hollow fiber film, stretching for 1.5 times, and then extracting the organic solvent and the nano calcium carbonate from the hollow fiber film by using ethanol and hydrochloric acid, wherein in the whole thermally induced phase spinning forming process, the two layers of feed liquid flow stably, and the pore diameters are changed from outside to inside from small to large (namely, the pore diameters of the two layers are different, and the pore diameters of each layer are uniform), so that the polyvinylidene fluoride hollow fiber film with the easily-cleaned pore structure is obtained.
Fourth), performance detection: the prepared polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure has pure water flux of 980L/(. Square meter) h at 25 ℃ and 0.1Mpa, tensile breaking strength of 15Mpa, elongation at break of 100%, maximum pore diameter of 0.18um in an inner layer, maximum pore diameter of 0.10um in an outer layer and porosity of 73% measured by using a bubble pressure method, and obvious connecting marks of the inner layer and the outer layer are not visible through an electron microscope structure photo, so that the integration is obvious.
Example five
First), preparing modified master batch for feed liquid with inner layer membrane structure: grinding nano calcium carbonate, passing through a 325-mesh screen, adding the ground and sieved powder into a high-speed mixer, stirring, adding the perfluorosulfonate solution into the nano calcium carbonate in a spray form, and stirring at a high speed for 10min; then transferring the pretreated powder into an ultrasonic processor with high-speed stirring, adding PHMG (GL) water aqua, stirring for 20min under the condition of 30KHZ, adding high molecular weight polyvinylidene fluoride powder with MFR of 2.0g/10min (230 ℃ and 21.6 kg), and uniformly stirring; and then the mixture is led into a double-screw extruder, mixed at 230 ℃, and simultaneously the small molecular volatile matters are discharged through multistage vacuumizing, wherein the vacuum degree is-0.4 to-0.7 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 12.5%
Nano calcium carbonate: 60 percent of
PHMG (GL) aqua: 24.5%
Perfluorosulfonate solution: 3%
And II) preparing modified master batches for the feed liquid with the outer layer membrane structure by comparing the modified master batches for the feed liquid with the inner layer membrane structure prepared by the method: introducing the mixture into another twin-screw extruder, mixing at 230 ℃, and simultaneously discharging micromolecular volatile matters (namely water vapor and low boiling point substances) by multi-stage vacuumizing, wherein the vacuum degree is-0.5 to-0.9 bar.
The weight percentages of the components of the prepared modified master batch are as follows:
high molecular weight polyvinylidene fluoride: 25 percent of
Nano calcium carbonate: 45%
PHMG (GL) aqua: 28%
Perfluorosulfonate solution: 2%
Thirdly), preparing the polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure: adding the modified master batch of the upper inner layer film structure feed liquid, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder by adopting a metering feeding mode according to the proportion of 1:1:1.5 by using a system of a double-screw extruder serial metering pump, mixing at 230 ℃, and extruding through one layer of an annular two-layer die; adding modified master batch in the feed liquid with the outer layer film structure, polyvinylidene fluoride powder and triethyl citrate into a double-screw extruder in a weighing feeding mode according to the proportion of 1:1:1 by using a system of a double-screw extruder serial metering pump, mixing at 230 ℃, and extruding the other layer through an annular two-layer die; and (3) synchronously extruding the feed liquid of the inner layer film structure and the feed liquid of the outer layer film structure, synchronously cooling to form a hollow fiber film, stretching for 2 times, and then extracting the organic solvent and the nano calcium carbonate from the hollow fiber film by using ethanol and hydrochloric acid, wherein in the whole thermally induced phase spinning forming process, the two layers of feed liquid flow stably, and the aperture is changed from outside to inside from small to large (namely, the apertures of the two layers are different, and the aperture size of each layer is uniform), so that the polyvinylidene fluoride hollow fiber film with the easily-cleaned pore structure is obtained.
Fourth), performance detection: the prepared polyvinylidene fluoride hollow fiber membrane with the easy-to-clean pore structure has the pure water flux of 880L/(. Square meter) h at 25 ℃ and 0.1Mpa, the tensile breaking strength of 13Mpa, the breaking elongation of 120%, the maximum pore diameter of an inner layer of 0.16um, the maximum pore diameter of an outer layer of 0.11um and the porosity of 75% measured by a bubble pressure method, and the obvious connecting trace of the inner layer and the outer layer can not be seen through an electron microscope structure photo, so that the integration is obvious.
While the present disclosure and features have been described above, it will be understood that variations and modifications in the above-described components and steps, including combinations of features individually disclosed or claimed herein, as well as other combinations of features that are apparent to persons skilled in the art, may be made under the inventive concepts of the present disclosure. Such variations and/or combinations fall within the technical field to which the application relates and fall within the scope of the claims of the application.
Claims (15)
1. The polyvinylidene fluoride hollow fiber membrane with the easily-cleaned pore structure is characterized by comprising an outer layer membrane structure and an inner layer membrane structure, wherein feed liquid is prepared by a thermally induced phase spinning process, and is synchronously and respectively extruded by two double-screw extruders, and the outer layer membrane structure and the inner layer membrane structure are respectively molded by two layers of dies, the pore structures of the outer layer membrane structure and the inner layer membrane structure have different pore diameters, and the pore diameter of the pore structure of the inner layer membrane structure is larger than that of the pore structure of the outer layer membrane structure.
2. The easy-to-clean porous structure polyvinylidene fluoride hollow fiber membrane according to claim 1, wherein the feed liquid composition of the inner membrane structure is: the modified master batch, polyvinylidene fluoride resin and organic liquid are controlled within the weight ratio of 1:1:1-1:1:2, wherein the modified master batch comprises the following components in percentage by weight:
polyvinylidene fluoride: 10-15%;
nano calcium carbonate: 50-60%;
macromolecular bacteriostatic agent: 20-30%;
modification additive: 1-5%;
and the feed liquid composition of the outer layer film structure is as follows: the weight ratio of the modified master batch to the polyvinylidene fluoride resin to the organic liquid is controlled within the range of 1:1:1-1:1:3; wherein the modified master batch comprises the following components in percentage by weight:
polyvinylidene fluoride: 15-25%;
nano calcium carbonate: 45-50%;
macromolecular bacteriostatic agent: 20-34%;
modification additive: 1-5%.
3. The easily cleaned porous structure polyvinylidene fluoride hollow fiber membrane according to claim 2, wherein,
the feed liquid of the inner layer film structure is melted, mixed and extruded by a double screw extruder at 180-230 ℃;
the feed liquid of the outer layer film structure is melted, mixed and extruded by a double screw extruder at the temperature of 200-230 ℃;
and extruding the feed liquid of the inner layer film structure and the feed liquid of the outer layer film structure through two double-screw extruders, spraying the feed liquid from two layers of mouth molds through metering pumps, cooling, forming and stretching for 1.5-2.5 times, and extracting the organic liquid and nano calcium carbonate in the inner layer film structure and the outer layer film structure to prepare the polyvinylidene fluoride hollow fiber membrane with the easy-cleaning pore structure.
4. The easy-to-clean porous structure polyvinylidene fluoride hollow fiber membrane according to claim 2, wherein the polyvinylidene fluoride is high molecular weight polyvinylidene fluoride, and the Melt Flow Rate (MFR) is 1-4 g/10min (230 ℃/21.6 kg).
5. The easy-to-clean pore structure polyvinylidene fluoride hollow fiber membrane of claim 4, wherein said high molecular weight polyvinylidene fluoride is a vinylidene fluoride homopolymer.
6. The easy-to-clean pore structure polyvinylidene fluoride hollow fiber membrane according to claim 2, wherein the organic liquid is selected from the group consisting of synthetic vegetable esters, citric acid esters, adipic acid esters, soybean oil.
7. The polyvinylidene fluoride hollow fiber membrane with the easily cleaned pore structure according to claim 2, wherein the nano calcium carbonate is cube-shaped and has an average particle size of 20-150 nanometers.
8. The easily cleaned porous polyvinylidene fluoride hollow fiber membrane according to claim 2, wherein the polymeric bacteriostatic agent is one or a mixture of polyhexamethylene guanidine (PHMG), polyhexamethylene biguanide (PHMB), chitosan and derivatives thereof with a weight average molecular weight greater than 20000.
9. The polyvinylidene fluoride hollow fiber membrane with the easily cleaned pore structure according to claim 8, wherein the high molecular bacteriostat is a liquid preparation with an active ingredient of 25-50%.
10. The easy-to-clean pore structure polyvinylidene fluoride hollow fiber membrane according to claim 2, wherein the modifying additive is a high temperature resistant surfactant.
11. The easy-to-clean pore structure polyvinylidene fluoride hollow fiber membrane of claim 10, wherein said modifying additive is an organofluorine surfactant solution.
12. The easy-to-clean pore structure polyvinylidene fluoride hollow fiber membrane according to claim 11, wherein the organic fluorine-based surfactant solution is perfluorosulfonate or perfluorocarboxylic acid.
13. The method for preparing a polyvinylidene fluoride hollow fiber membrane with an easy-to-clean pore structure according to any one of claims 2 to 12, characterized by comprising the steps of:
(1) Preparing modified master batches in the feed liquid of the inner layer film structure by mixing and extruding, wherein the modified master batches comprise the following components in percentage by weight:
polyvinylidene fluoride: 10-15%;
nano calcium carbonate: 50-60%;
macromolecular bacteriostatic agent: 20-30%;
modification additive: 1-5%;
(2) Preparing modified master batches in the feed liquid of the outer layer film structure by mixing and extruding, wherein the modified master batches comprise the following components in percentage by weight:
polyvinylidene fluoride: 15-25%;
nano calcium carbonate: 45-50%;
macromolecular bacteriostatic agent: 20-34%;
modification additive: 1-5%;
(3) Preparing an inner layer film structure feed liquid and homogenizing, wherein the inner layer film structure feed liquid comprises a modified master batch, polyvinylidene fluoride resin and organic liquid, and the weight ratio of the modified master batch to the polyvinylidene fluoride resin is controlled within the range of 1:1:1-1:1:2;
(4) Preparing an outer layer film structure feed liquid and homogenizing, wherein the outer layer film structure feed liquid comprises a modified master batch, polyvinylidene fluoride resin and organic liquid, and the weight ratio of the modified master batch to the polyvinylidene fluoride resin is controlled within the range of 1:1:1-1:1:3;
(5) The homogenized inner layer film structure feed liquid and outer layer film structure feed liquid are extruded by two twin-screw extruders continuously and simultaneously, and are sprayed out synchronously by two layers of mouth molds after passing through a metering pump, and after cooling forming and stretching for 1.5-2.5 times, organic liquid and nano calcium carbonate are extracted, so that the polyvinylidene fluoride hollow fiber membrane with the easily-cleaned pore structure is prepared;
the feed liquid with the inner layer film structure is melted, mixed and extruded by a double screw extruder at 180-230 ℃; and (3) melting, mixing and extruding the feed liquid with the outer layer film structure through a double-screw extruder at the temperature of 200-230 ℃.
14. The method for preparing the polyvinylidene fluoride hollow fiber membrane with the easily cleaned pore structure according to claim 13, wherein the preparation of the modified master batch comprises the following steps:
1) The nano calcium carbonate passes through a 325-mesh mechanical sieve to eliminate large soft agglomeration;
2) Adding nano calcium carbonate and a modifying additive into a high-speed mixer for surface pretreatment;
3) Adding the pretreated nano calcium carbonate and the high-molecular bacteriostat into a stirring kettle, stirring at a high speed, and simultaneously carrying out ultrasonic dispersion, and treating for 10-50 min;
4) Adding polyvinylidene fluoride, stirring for 30min, mixing by a double-screw extruder, wherein the mixing temperature is 180-200 ℃, simultaneously adopting multistage vacuumizing to discharge volatile matters, the vacuum degree is minus 0.2 to minus 0.8bar, extruding the mixture, performing water cooling or air cooling granulation, and removing surface floating water to obtain the modified master batch.
15. The method for preparing the polyvinylidene fluoride hollow fiber membrane with the easily cleaned pore structure according to claim 14, wherein the water cooling temperature is controlled to be 15-35 ℃, and the water cooling particles are dried at 80 ℃; and (5) air cooling at normal temperature, and matching the wind speed according to the yield.
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