CN115105957B - PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and preparation method thereof - Google Patents

PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and preparation method thereof Download PDF

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CN115105957B
CN115105957B CN202210882653.1A CN202210882653A CN115105957B CN 115105957 B CN115105957 B CN 115105957B CN 202210882653 A CN202210882653 A CN 202210882653A CN 115105957 B CN115105957 B CN 115105957B
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pan
pvb
pvdf
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ultrafiltration membrane
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CN115105957A (en
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叶麒
陈俊超
王炎峰
邱晖
丁国良
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Zhejiang Yimo New Material Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • 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
    • B01D67/0016—Coagulation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • 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
    • 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
    • B01D69/10—Supported membranes; Membrane supports
    • 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
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/24—Mechanical properties, e.g. strength
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
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    • Y02A20/131—Reverse-osmosis

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  • Engineering & Computer Science (AREA)
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  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The invention relates to a PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and a preparation method thereof, wherein a casting solution of the hollow fiber ultrafiltration membrane comprises the following preparation raw materials in percentage by mass: 10-20% of PAN, 0.01-5% of PVDF, 0.01-5% of PVB, 50-70% of good solvent, 2-10% of additive and 100% of the sum of the components. The casting solution prepared by the PAN/PVDF/PVB ternary alloy material is coated by a woven tube with a support, the physical tensile strength is increased, the overall tensile strength can be up to 155N, the problem that a hollow fiber ultrafiltration membrane is easy to break is solved, the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane takes PAN as a main material, PVDF and PVB are taken as additives, and the pure water flux of the prepared material can be up to 1900L/(m) 2 H), the PAN/PVDF/PVB ternary mixing also greatly reduces the raw material cost, and in addition, the surface coating of the support woven tube adopts less raw materials than homogenization, so that the production cost is reduced.

Description

PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and preparation method thereof
Technical Field
The invention relates to the technical field of polymer membrane preparation, in particular to a PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and a preparation method thereof.
Background
Polyacrylonitrile (PAN) has excellent hydrophilicity, good solvent resistance, light resistance, weather resistance, mold resistance, thermal stability and chemical stability, and is suitable for dry and wet spinning, however, the mechanical strength of the polyacrylonitrile ultrafiltration membrane is not high; the Chinese patent of application publication No. CN102389721A discloses a polyacrylonitrile membrane with a supporting material and a preparation method thereof, wherein the longitudinal tensile strength of 3-4 monofilament fibers prepared by the method can reach more than 1 kg force, and the water flux of the membrane can reach 280L/(m) 2 H), 0.1MPa, which is 2 times or more of the braided rope structural membrane, and is equivalent to an unsupported hollow fiber membrane. In actual use, the monofilament lining is found, the actual strength is not changed greatly, the tensile strength of the film yarn is small, and the yarn is easy to break; PAN materials are poor in fatigue resistance, easy to bend and damage, small in membrane wire flux of a homogeneous membrane, and membrane materials with higher water flux are required to be sought.
Polyvinylidene fluoride (PVDF) is used as a common material of a separation membrane and is widely applied to the fields of water supply engineering, industrial wastewater, pharmaceutical industry, food industry, energy industry and the like. However, the strong hydrophobicity of PVDF membranes, which results in their susceptibility to contamination, increases the cost of membrane operation, and limits their use. The Chinese patent of application publication No. CN111921384A discloses a casting solution of PVDF hollow fiber ultrafiltration membrane, a spinning mechanism and a production method thereof, wherein the casting solution has high temperature, can dissolve spinning auxiliary agent on a supporting tube, improves the adhesiveness of PVDFF and PET supporting tube, has the strength of composite membrane filaments reaching more than 110N, and has high pure water flux.
Polyvinyl butyral resins (PVB) are excellent thermoplastic polymers obtained by condensation of polyvinyl alcohol and butyraldehyde. The molecular structure of PVB determines that the PVB has higher comprehensive properties such as tensile strength, impact resistance, transparency, elasticity and the like, which are incomparable with other polymers, and PVB is mainly applied to safe glass interlayer materials and is also widely applied to special paint, adhesives, ceramic printing paper and the like.
The ultrafiltration membrane modification method is many, and the blending method is widely used because of the advantages of high efficiency, easy operation, one-step completion in the film forming process, and the like. Therefore, it is very important to find a membrane material with low ternary blending price, good filtering effect, high physical and chemical stability and high flux.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to design and provide a PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane and a production method thereof, wherein advantages of PAN, PVDF, PVB materials are complementary, a layer of ternary alloy membrane material is uniformly coated on the surface of a support tube by utilizing a phase separation principle of dry-wet preparation, and the microstructure and crystal form of the surface and the section of a membrane wire are regulated and controlled by technological parameters to prepare the hollow fiber composite membrane which has high performance and is tightly combined with the support tube.
The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane comprises a casting solution of the hollow fiber ultrafiltration membrane and a supporting tube for supporting the casting solution, wherein the casting solution of the hollow fiber ultrafiltration membrane comprises the following preparation raw materials in percentage by mass:
PAN 10-20％，
PVDF 0.01-5％，
PVB 0.01-5％，
50-70% of good solvent,
2-10% of additive, and the sum of all components is 100%.
Further, the PAN uses binary or ternary copolymer composed of acrylic acid, methyl methacrylate and sodium acrylate sulfonate, and has a molecular weight of 3 ten thousand to 8 ten thousand, preferably a molecular weight of 3 ten thousand; the PVDF has a molecular weight of 30 ten thousand to 110 ten thousand and is a blend of one or more types; the PVB has a molecular weight of 4 ten thousand to 25 ten thousand, preferably a molecular weight of 4 ten thousand.
Further, the good solvent is a water-soluble good solvent, and the water-soluble good solvent is one or a mixture of more of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO).
Further, the additive is one or a mixture of more of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycerin, lithium chloride, lithium nitrate and calcium nitrate.
Further, the polyethylene glycol is preferably 200, 400, 1000, 2000, 6000; the polyvinyl pyrrolidone is preferably K17, K30, K90.
On the other hand, the invention also provides a preparation method of the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, which comprises the following preparation steps:
(1) Preparing a casting film liquid: heating the stirring kettle in advance, adding PAN, PVDF, PVB, a good solvent and an additive into the stirring kettle, stirring and dissolving, introducing nitrogen for protection until the mixture is uniformly dissolved in the stirring kettle to form uniform and transparent viscous liquid, reducing the stirring speed, and defoaming the casting film liquid in a heat preservation state;
(2) Preparing a ternary blending hollow fiber ultrafiltration membrane: and extruding and spinning the film casting solution by adopting a dry-wet spinning machine, preserving the temperature of a spinning nozzle at 40-50 ℃, uniformly coating the film casting solution on the surface of a supporting tube through the spinning nozzle, vertically entering into a coagulating bath, enabling the dry spinning distance to be less than 10cm, enabling film filaments to enter into a rinsing tank through a godet after the coagulating bath, further solidifying and rinsing, winding and collecting the film filaments after rinsing forming through a filament collecting machine, soaking the cut film filaments in purified water, and drying after post treatment to obtain the ternary blending hollow fiber ultrafiltration membrane with the support.
Further, the stirred tank is heated to 30-50 ℃; stirring and dissolving time is 10-12h, and dissolving and stirring speed is 100-150 rpm; the defoaming time is 8-12h, and the stirring speed is 3-6 r/min during defoaming.
Further, the supporting tube is made of PET material, and the outer diameter of the supporting tube is 1.20-1.95mm by adopting a crocheting or braiding process.
Further, the spinning speed of the dry-wet spinning machine is 10-40m/min, the coagulating bath is pure water, and the temperature is 30-50 ℃; pure water is filled in the rinsing tank, the temperature is 20-40 ℃, the soaking time is 23-24h, and the soaking temperature is 20-40 ℃.
Further, the post-treatment drying conditions are: and (3) hot air circulating dehumidifying drying room, wherein the temperature is 45-60 ℃, the drying room is placed for 24-168 hours, and the film yarns are dried.
Compared with the prior art, the invention has the beneficial effects that:
(1) Physical tensile strength increases: the PAN film of the same type has generally low tensile strength and only has a few kilograms of force, and the casting solution prepared by using the PAN/PVDF/PVB ternary alloy material is coated by a woven tube with a support, so that the overall tensile strength can be up to 155N, and the problem that the hollow fiber ultrafiltration membrane is easy to break is solved.
(2) The cost is reduced under the condition of maintaining the performance: PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane is prepared by taking PAN as a main material and PVDF and PVB as additivesThe pure water flux of the obtained material can reach 1900L/(m) 2 H), the tensile breaking strength can reach 155N, the tensile strength is improved under the condition that the water passing performance is kept good, the raw material cost is greatly reduced by ternary mixing of PAN/PVDF/PVB, and in addition, the raw material used for coating the outer surface of the support woven pipe is less than that used for homogenizing, so that the production cost is reduced.
(3) The PAN/PVDF/PVB ternary mixing solves the problems of difficult coating, small membrane wire strength, easy breakage and small flux of PAN materials, and expands the water treatment field of PAN material membranes.
(4) The PAN/PVDF/PVB ternary mixing solves the problems of poor flexibility and poor fatigue resistance caused by too strong rigidity of PAN materials, reduces the defects of membrane wires, and prolongs the service life of the membrane wires.
(5) Because PAN is used as the main material of the ternary alloy, the ternary alloy has low molecular weight, good solvent solubility and low solid content, so that raw materials can be well dissolved and uniformly dispersed at low temperature, the mixing temperature in a stirring kettle and the spinning equipment condition are reduced, and the energy is saved.
Drawings
FIG. 1 is a cross-sectional electron microscope view of a ternary alloy hollow fiber ultrafiltration membrane of the invention.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples.
The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane comprises a casting solution of the hollow fiber ultrafiltration membrane and a supporting tube for supporting the casting solution, wherein the hollow fiber ultrafiltration membrane comprises the following preparation raw materials in percentage by mass:
PAN 10-20％，
PVDF 0.01-5％，
PVB 0.01-5％，
50-70% of good solvent,
2-10% of additive, and the sum of all components is 100%.
Wherein PAN uses binary or ternary copolymer composed of acrylic acid, methyl methacrylate and sodium acrylate sulfonate, the molecular weight is 3-8 ten thousand, and the molecular weight is preferably about 3 ten thousand; the PVDF has a molecular weight of 30 ten thousand to 110 ten thousand and is a blend of one or more types; the PVB has a molecular weight of 4 ten thousand to 25 ten thousand, preferably about 4 ten thousand; the good solvent is a water-soluble good solvent, and the water-soluble good solvent is one or a mixture of more of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) and Dimethylsulfoxide (DMSO); the additive is one or more of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycerol, lithium chloride, lithium nitrate and calcium nitrate; polyethylene glycol is preferably 200, 400, 1000, 2000, 6000; the polyvinyl pyrrolidone is preferably K17, K30, K90.
On the other hand, the invention also provides a preparation method of the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, which comprises the following preparation steps:
(1) Preparing a casting film liquid: heating the stirring kettle in advance, adding PAN, PVDF, PVB, a good solvent and an additive into the stirring kettle, stirring and dissolving, introducing nitrogen for protection until the mixture is uniformly dissolved in the stirring kettle to form uniform and transparent viscous liquid, reducing the stirring speed, and defoaming the casting film liquid in a heat preservation state;
(2) Preparing a ternary blending hollow fiber ultrafiltration membrane: and extruding and spinning the film casting solution by adopting a dry-wet spinning machine, preserving the temperature of a spinning nozzle at 40-50 ℃, uniformly coating the film casting solution on the surface of a supporting tube through the spinning nozzle, vertically entering into a coagulating bath, enabling the dry spinning distance to be less than 10cm, enabling film filaments to enter into a rinsing tank through a godet after the coagulating bath, further solidifying and rinsing, winding and collecting the film filaments after rinsing forming through a filament collecting machine, soaking the cut film filaments in purified water, and drying after post treatment to obtain the ternary blending hollow fiber ultrafiltration membrane with the support.
Wherein, the stirred tank is heated to 30-50 ℃; stirring and dissolving time is 10-12h, and dissolving and stirring speed is 100-150 rpm; the defoaming time is 8-12h, and the stirring speed is 3-6 r/min during defoaming; the supporting tube is made of PET material, and the outer diameter of the supporting tube is 1.20-1.95mm by adopting a crocheting or braiding process; the spinning speed of the dry-wet spinning machine is 10-40m/min, the coagulating bath is pure water, and the temperature is 30-50 ℃; pure water is arranged in the rinsing tank, the temperature is 20-40 ℃, the soaking time is 23-24h, and the soaking temperature is 20-40 ℃; the post-treatment drying conditions are as follows: and (3) hot air circulating dehumidifying drying room, wherein the temperature is 45-60 ℃, the drying room is placed for 24-168 hours, and the film yarns are dried.
Example 1
(1) Preparing a casting film liquid: the stirred tank temperature was heated to 40℃in advance and 1500.0g of DMF, 100.0g of NMP, 280.0g of PAN, 100.0g of PVB, 20.0g of PVDF (Sanafu, FR 904), 40.0g of PEG200, 100.0g of PVP-k17, 60.0g of Ca (NO) were accurately weighed by an electronic scale 3 ) 2 Adding the raw materials into a stirring kettle, stirring for 10 hours, setting the stirring speed to 115 revolutions per minute, and introducing nitrogen for protection until the raw materials are uniformly dissolved in the kettle; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 40 ℃ for standby.
2) Spinning a composite film: extruding and spinning at 20m/min with a dry-wet spinning machine, wherein the inner support tube is a polyester woven tube, and the outer diameter of the support tube is 1.8mm. The spinneret is kept at 40 ℃, the casting solution is uniformly coated on the surface of a supporting tube through the spinneret and vertically enters a coagulating bath, the dry spinning distance is less than 10cm, the coagulating bath is pure water, and the temperature is controlled at 40 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 30 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And cutting membrane filaments, soaking in purified water at 30 ℃ for 24 hours to obtain the hollow fiber ultrafiltration membrane with the outer diameter of 2.0 mm. The prepared hollow fiber composite membrane has the pure water flux of 800L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); the bubble point pressure was 0.15MPa and the tensile breaking strength was 150N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the film yarn has no obvious crease.
Example 2
(1) Preparing a casting film liquid: the temperature of the stirred tank is heated to 45 ℃ in advance, 1200.0g of DMF, 400.0g of NMP, 280.0g of PAN, 50.0g of PVB and 20.0g are accurately weighed by an electronic scale40.0g PEG200, 100.0g PVP-k17, 60.0g Mg (NO) 3 ) 2 Adding the raw materials into a stirring kettle, stirring for 10 hours, setting the stirring speed to 115 revolutions per minute, and introducing nitrogen for protection until the raw materials are uniformly dissolved in the kettle; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 45 ℃ for standby.
2) Spinning a composite film: and adopting a dry-wet spinning machine to extrude and spin at a filament collecting speed of 20m/min, wherein an inner supporting tube is a polyester crochet tube, and the outer diameter of the supporting tube is 1.2mm. The spinneret is kept at 50 ℃, the casting solution is uniformly coated on the surface of a supporting tube through the spinneret and vertically enters a coagulating bath, the dry spinning distance is less than 15cm, the coagulating bath is pure water, and the temperature is controlled at 45 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 30 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And (3) cutting membrane filaments, soaking in purified water at 30 ℃ for 24 hours, and performing post-treatment and drying to obtain the hollow fiber ultrafiltration membrane with the outer diameter of 1.3 mm. The prepared hollow fiber composite membrane has the pure water flux of 800L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); the bubble point pressure was 0.2MPa and the tensile breaking strength was 100N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the film yarn has no obvious crease.
Example 3
(1) Preparing a casting film liquid: the stirred tank temperature was heated to 45℃in advance and 1500.0g of DMAC, 100.0g of NMP, 280.0g of PAN, 100.0g of PVB, 20.0g of PVDF, 60.0g of PEG200, 100.0g of PVP-k90, 40.0g of Na (NO) were accurately weighed by an electronic scale 3 ) 2 Adding the raw materials into a stirring kettle, stirring for 10 hours, setting the stirring speed to 115 revolutions per minute, and introducing nitrogen for protection until the raw materials are uniformly dissolved in the kettle; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 45 ℃ for standby.
2) Spinning a composite film: extruding and spinning at 20m/min with a dry-wet spinning machine, wherein the inner support tube is a polyester woven tube, and the outer diameter of the support tube is 1.8mm. The spinneret is kept at 50 ℃, and the casting solution is uniformly coated on the support through the spinneretThe surface of the support tube vertically enters a coagulating bath, the dry spinning distance is less than 10cm, the coagulating bath is pure water, and the temperature is controlled at 45 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 30 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And (3) cutting membrane filaments, soaking in purified water at 30 ℃ for 24 hours, and drying after sodium hypochlorite treatment to obtain the hollow fiber ultrafiltration membrane with the outer diameter of 2.0 mm. The prepared hollow fiber composite membrane has the pure water flux of 1500L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); the bubble point pressure was 0.1MPa and the tensile breaking strength was 150N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the film yarn has no obvious crease.
Example 4
(1) Preparing a casting film liquid: the stirred tank temperature was heated to 45℃beforehand and 1500.0g of NMP, 80.0g of DMAC, 400.0g of PAN, 40.0g of PVB, 40.0g of PVDF (coating grade), 100.0g of PVP-k90, 40.0g of Ca (NO 3 ) 2 Adding the raw materials into a stirring kettle, stirring for 10 hours, setting the stirring speed to 115 revolutions per minute, and introducing nitrogen for protection until the raw materials are uniformly dissolved in the kettle; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 45 ℃ for standby.
(2) Spinning a composite film: extruding and spinning at 20m/min with a dry-wet spinning machine, wherein the inner support tube is a polyester woven tube, and the outer diameter of the support tube is 1.8mm. The spinneret is kept at 65 ℃, the casting solution is uniformly coated on the surface of a supporting tube through the spinneret and vertically enters a coagulating bath, the dry spinning distance is less than 15cm, the coagulating bath is pure water, and the temperature is controlled at 50 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 45 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And (3) cutting membrane filaments, soaking the membrane filaments in 500ppm sodium hypochlorite aqueous solution at 30 ℃ for 24 hours, and drying to obtain the hollow fiber ultrafiltration composite membrane with the outer diameter of 2.0 mm. The prepared hollow fiber composite membrane has the pure water flux of 1900L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); bubble point pressure of 0.05MPa, and the tensile breaking strength is 155N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the film yarn has no obvious crease.
Comparative example 1
(1) Preparing a casting film liquid: the stirred tank temperature was heated to 45℃in advance and 1500.0g of DMAC, 280.0g of PAN, 20.0g of PVDF, 60.0g of PEG200, 100.0g of PVP-k90, 40.0g of Na (NO) were weighed accurately by an electronic scale 3 ) 2 Adding the raw materials into a stirring kettle, stirring for 10 hours, setting the stirring speed to 115 revolutions per minute, and introducing nitrogen for protection until the raw materials are uniformly dissolved in the kettle; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 65 ℃ for standby.
(2) Spinning a composite film: and adopting a dry-wet spinning machine to extrude and spin at a filament collecting speed of 20m/min, wherein an inner supporting tube is a polyester crochet tube, and the outer diameter of the supporting tube is 1.2mm. The spinneret is kept at 45 ℃, the casting solution is uniformly coated on the surface of a supporting tube through the spinneret and vertically enters a coagulating bath, the dry spinning distance is less than 10cm, the coagulating bath is pure water, and the temperature is controlled at 45 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 30 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And (3) cutting membrane filaments, soaking in water at 30 ℃ for 24 hours, and drying by sodium hypochlorite to obtain the hollow fiber ultrafiltration composite membrane with the outer diameter of 1.3 mm. The prepared hollow fiber composite membrane has the pure water flux of 400L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); the bubble point pressure was 0.20MPa and the tensile breaking strength was 100N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the film yarn has serious cracks at folds.
Comparative example 2
(1) Preparing a casting film liquid: the stirred tank temperature was heated to 45℃in advance and 1500.0g of NMP, 80.0g of DMAC, 400.0g of PAN, 40.0g of PVB, 100.0g of PVP-k90, 40.0g of Ca (NO) were accurately weighed by an electronic scale 3 ) 2 Adding the above materials into a stirring kettle, stirring for 10h at a stirring speed of 115 rpmThe nitrogen is introduced for protection until the inside of the kettle is uniformly dissolved; then the stirring speed is reduced to 3 revolutions per minute, and the stirring is carried out at a low speed for deaeration for 8 hours at 45 ℃ for standby.
(2) Spinning a composite film: extruding and spinning at 20m/min with a dry-wet spinning machine, wherein the inner support tube is a polyester woven tube, and the outer diameter of the support tube is 1.8mm. The spinneret is kept at 65 ℃, the casting solution is uniformly coated on the surface of a supporting tube through the spinneret and vertically enters a coagulating bath, the dry spinning distance is less than 10cm, the coagulating bath is pure water, and the temperature is controlled at 50 ℃; the film yarn enters a rinsing tank through a yarn guiding wheel after coagulation bath for further solidification and rinsing, the rinsing tank is pure water, the temperature is 45 ℃, and the film yarn after rinsing forming is wound and collected through a yarn collecting machine. And (3) cutting membrane filaments, soaking the membrane filaments in 500ppm sodium hypochlorite aqueous solution at 30 ℃ for 24 hours, and drying to obtain the hollow fiber ultrafiltration composite membrane with the outer diameter of 2.0 mm. The prepared hollow fiber composite membrane has the pure water flux of 1300L/(m) under the conditions of the test temperature of 25 ℃ and the pressure of 0.1MPa 2 H); the bubble point pressure was 0.05MPa and the tensile breaking strength was 150N. The bending resistance was evaluated and the cracking degree was examined using a bending machine, and the conditions were examined: bending angle 25 deg., times 100 times, bending speed 100 times/min, result shows: the crease of the film yarn is provided with a crack.
As can be seen from the above examples and comparative examples, the membrane wire prepared from PAN, PVDF, PVB ternary alloy has a high water flux up to 1900L/(m) 2 H), the tensile breaking strength is good, the tensile breaking strength can reach 155N, the flexibility and fatigue resistance of the film yarn are improved, and the film yarn has long service life proved by practice; meanwhile, because PAN is adopted as a main alloy material, the molecular weight is low, the solvent solubility is good, the solid content is low, the solvent can be well dissolved and uniformly dispersed at low temperature, the condition of spinning equipment is reduced, the heating temperature of a stirring kettle is 30-50 ℃, the temperature of a spinneret is 40-50 ℃, and the energy is saved.
The foregoing has shown and described the basic principles, main features and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane comprises a casting solution of the hollow fiber ultrafiltration membrane and a supporting tube for supporting the casting solution, and is characterized in that the casting solution of the hollow fiber ultrafiltration membrane comprises the following preparation raw materials in percentage by mass:
PAN 10-20%，
PVDF 0.01-5%，
PVB 0.01-5%，
50-70% of good solvent,
2-10% of additive, and the sum of all components is 100%.
2. The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane according to claim 1, wherein the PAN is a binary or ternary copolymer composed of acrylic acid, methyl methacrylate and sodium acrylate, and has a molecular weight of 3-8 ten thousand; the PVDF has a molecular weight of 30 ten thousand to 110 ten thousand and is a blend of one or more types; the PVB has a molecular weight of 4-25 ten thousand.
3. The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane of claim 1, wherein the good solvent is a water-soluble good solvent which is a mixture of one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide.
4. The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane of claim 1, wherein: the additive is one or a mixture of more of polyethylene glycol, polyvinylpyrrolidone, glycerin, lithium chloride, lithium nitrate and calcium nitrate.
5. The PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane of claim 4, wherein: the polyethylene glycol is 200, 400, 1000, 2000, 6000; the polyvinyl pyrrolidone is K17, K30 and K90.
6. A method for preparing a PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane according to any of claims 1 to 4, comprising the following steps:
preparing a casting film liquid: heating the stirring kettle in advance, adding PAN, PVDF, PVB, a good solvent and an additive into the stirring kettle, stirring and dissolving, introducing nitrogen for protection until the mixture is uniformly dissolved in the stirring kettle to form uniform and transparent viscous liquid, reducing the stirring speed, and defoaming the casting film liquid in a heat preservation state;
preparing a ternary blending hollow fiber ultrafiltration membrane: and extruding and spinning the film casting solution by adopting a dry-wet spinning machine, preserving the temperature of a spinning nozzle at 40-50 ℃, uniformly coating the film casting solution on the surface of a supporting tube through the spinning nozzle, vertically entering into a coagulating bath, enabling the dry spinning distance to be less than 10cm, enabling film filaments to enter into a rinsing tank through a godet after the coagulating bath, further solidifying and rinsing, winding and collecting the film filaments after rinsing forming through a filament collecting machine, soaking the cut film filaments in purified water, and drying after post treatment to obtain the ternary blending hollow fiber ultrafiltration membrane with the support.
7. The method for preparing the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, which is characterized in that: heating the stirred tank to 30-50 ℃; stirring and dissolving time is 10-12h, and dissolving and stirring speed is 100-150 rpm; the defoaming time is 8-12h, and the stirring speed is 3-6 r/min during defoaming.
8. The method for preparing the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, which is characterized in that: the supporting tube is made of PET material, and is made of a crochet or braiding technology, and the outer diameter of the supporting tube is 1.20-1.95mm.
9. The preparation method of the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, according to claim 6, wherein the spinning speed of the dry-wet spinning machine is 10-40m/min, the coagulating bath is pure water, and the temperature is 30-50 ℃; pure water is filled in the rinsing tank, the temperature is 20-40 ℃, the soaking time is 23-24h, and the soaking temperature is 20-40 ℃.
10. The method for preparing the PAN/PVDF/PVB ternary alloy hollow fiber ultrafiltration membrane, which is characterized in that: the post-treatment drying conditions are as follows: and (3) hot air circulating dehumidifying drying room, wherein the temperature is 45-60 ℃, the drying room is placed for 24-168 hours, and the film yarns are dried.
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