For the preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane of drinking water treatment
Technical field
The present invention relates to a kind of preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane for drinking water treatment, particularly relate to a kind of thermally induced phase separation (being called for short hot method) and prepare Kynoar (PVDF) hollow-fibre membrane blended with polyaryl thioether sulfone (PASS), for municipal drinking water process, belong to UF membrane and technical field of drinking water treatment.
Background technology
The existing water source of China is generally subject to organic pollution, and the combined pollutions such as high organic matter, high concentrtion appear in some areas.Traditional coagulation-precipitation-filtration-sterilization process filtering accuracy is low, disinfectant and coagulant use amount high, large to water quality impact, the water after process can not meet the requirement of new national standard 106 drinking water standards.Membrane separation technique carries out drinking water deep purification now, ensures the important new technology of water quality safety.Be that the water treatment technology of core has developed into third generation drinking water purification process with milipore filter, the group technology of it and other technology, can process micro polluted source, the drinking water of production high-quality effectively.
Traditional non-solvent phase method (abbreviation wet method) produce hollow-fibre membrane, intensity is low, toughness is poor, easy fracture of wire in using, life-span be short, be unsuitable for applying in large-scale drinking water treatment engineering.The hollow fiber ultrafiltration membrane of the large flux of municipal drinking water process, high strength, antipollution, low cost is suitable in the urgent need to exploitation.
Summary of the invention
The object of the invention is the preparation method proposing a kind of polyvinylidene fluoride hollow fiber ultrafiltration membrane for drinking water treatment, to prepare the hollow-fibre membrane of high strength, high tenacity, large flux, and make it have stronger contamination resistance, there is higher cost performance, for municipal drinking water process engineering provides product guarantee.
The preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane for drinking water treatment that the present invention proposes, comprises the following steps:
(1) Kynoar and polyaryl thioether sulfone are carried out drying respectively in dryer, bake out temperature is 80 ~ 90 DEG C, and drying time is 24 ~ 36 hours;
(2) for the preparation of the blended polymer solution of masking:
In blended polymer solution, the mass percent of each component is:
After Kynoar, polyaryl thioether sulfone, tetraethylene glycol, 1-METHYLPYRROLIDONE and polyvinylpyrrolidone are weighed according to the above ratio, be placed in stirred tank, carry out stirring, dissolving at the temperature of 150 ~ 170 DEG C, mixing time is 14 ~ 16 hours, speed of agitator 90 ~ 110 revs/min, obtains uniform blended polymer solution;
(3) the extruding and be shaped of hollow-fibre membrane, detailed process is as follows:
(3-1) the blended polymer solution of step (2) is sent in double screw extruder by spinning pump, the charging rate of raw material is 15 ~ 20Kg/ hour, and the temperature of extruder 6 sections is identical, is 150 ~ 170 DEG C, extrusion temperature is 150 ~ 170 DEG C, and screw speed is 90 ~ 120 revs/min;
(3-2) blended polymer solution is after double screw extruder is extruded, successively after filter and spinning pump, extrude from the annular die of spinning-drawing machine, form hollow as-spun fibre, the external diameter of described annular die is 5 millimeters, internal diameter is 4.2 millimeters, and annular die center passes into nitrogen, and nitrogen pressure is 30 ~ 60 millimeter of water (mmH
2o);
(3-3) above-mentioned hollow as-spun fibre is made to be lower the temperature in the air of 15 ~ 30 DEG C in temperature, the distance that sky is walked is 20 ~ 40 centimetres, then enter in cold extraction liquid bath through cold extraction liquid cooling curing, through winder rolling, make hollow-fibre membrane intermediate, rolling speed is 15 ~ 20 ms/min, the mixed liquor that described cold extraction liquid is both water and tetraethylene glycol, in cold extraction mixed liquor, the mass percent concentration of water is 0 ~ 50wt%, the mass percent concentration of tetraethylene glycol is 50 ~ 100wt%, and the temperature of cold extraction mixed liquor is 20 ~ 40 DEG C;
(4) the hollow-fibre membrane intermediate step (3) prepared immerses in ultra-pure water, removes the mixture of the first diluent in film and the second diluent. and water temperature is 30 ~ 50 DEG C, and leaching time is 12 ~ 15 hours, and ultrapure electrical conductivity of water is 10 μ S/cm;
(5) the hollow-fibre membrane intermediate being stripped of diluent of step (4) is at room temperature dried, after drying, obtain hollow fiber ultrafiltration membrane.
The preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane for drinking water treatment that the present invention proposes, its advantage is:
1, the polyvinylidene fluoride hollow fiber ultrafiltration membrane adopted in preparation method of the present invention prepare material, safety and sanitation, environmental protection, there is higher heat resistance and chemical stability, outstanding weatherability, resistance to ozone, ultraviolet resistance radiation and chemical resistance are the high-end drinking water treatment membrane materials of function admirable.
2, the preparation of polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared of the inventive method, its external diameter is 1.3 ~ 1.6mm, and wall thickness is 270 ~ 379 μm.Its section is co-continuous network, asymmetric pore structure, and hole height is through, be evenly distributed, and outer surface aperture is in 20 ~ 40 nanometers.Be 25 DEG C in temperature, under 0.1MPa pressure, pure water flux is 250 ~ 1020L/m
2h, tensile strength of fiber 5.0 ~ 9.1MPa, elongation at break 80 ~ 110%.The Structure and Properties of film shows after tested, and hot method doughnut alloy ultrafiltration membrane of the present invention is adapted at applying in municipal drinking water process.Film retain height, to produce water water quality good, not fracture of wire in using, stable performance.
3, the polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared of the inventive method, film good hydrophilic property, has excellent antifouling property.Use in Practical Project and prove, film not easily pollutes, and the regular maintenance cleaning frequency is 2 ~ 3 times of other similar film product, and maintenance operation expense is low.
Accompanying drawing explanation
Fig. 1 is the outer surface electromicroscopic photograph of polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared by the inventive method.
Fig. 2 is the section electromicroscopic photograph of polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared by sharp the inventive method.
Fig. 3 is the section outward flange electromicroscopic photograph of polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared by the inventive method.
Detailed description of the invention
The preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane for drinking water treatment that the present invention proposes, comprises the following steps:
(1) Kynoar and polyaryl thioether sulfone are carried out drying respectively in dryer, bake out temperature is 80 ~ 90 DEG C, and drying time is 24 ~ 36 hours;
(2) for the preparation of the blended polymer solution of masking:
In blended polymer solution, the mass percent of each component is:
After Kynoar, polyaryl thioether sulfone, tetraethylene glycol, 1-METHYLPYRROLIDONE and polyvinylpyrrolidone are weighed according to the above ratio, be placed in stirred tank, carry out stirring, dissolving at the temperature of 150 ~ 170 DEG C, mixing time is 14 ~ 16 hours, speed of agitator 90 ~ 110 revs/min, obtains uniform blended polymer solution;
(3) the extruding and be shaped of hollow-fibre membrane, detailed process is as follows:
(3-1) the blended polymer solution of step (2) is sent in double screw extruder by spinning pump, the charging rate of raw material is 15 ~ 20Kg/ hour, and the temperature of extruder 6 sections is identical, is 150 ~ 170 DEG C, extrusion temperature is 150 ~ 170 DEG C, and screw speed is 90 ~ 120 revs/min;
(3-2) blended polymer solution is after double screw extruder is extruded, successively after filter and spinning pump, extrude from the annular die of spinning-drawing machine, form hollow as-spun fibre, the external diameter of described annular die is 5 millimeters, internal diameter is 4.2 millimeters, and annular die center passes into nitrogen, and nitrogen pressure is 30 ~ 60 millimeter of water (mmH
2o);
(3-3) above-mentioned hollow as-spun fibre is made to be lower the temperature in the air of 15 ~ 30 DEG C in temperature, the distance that sky is walked is 20 ~ 40 centimetres, then enter in cold extraction liquid bath through cold extraction liquid cooling curing, through winder rolling, make hollow-fibre membrane intermediate, rolling speed is 15 ~ 20 ms/min, the mixed liquor that described cold extraction liquid is both water and tetraethylene glycol, in cold extraction mixed liquor, the mass percent concentration of water is 0 ~ 50wt%, the mass percent concentration of tetraethylene glycol is 50 ~ 100wt%, and the temperature of cold extraction mixed liquor is 20 ~ 40 DEG C;
(4) the hollow-fibre membrane intermediate step (3) prepared immerses in ultra-pure water, removes the mixture of the first diluent in film and the second diluent. and water temperature is 30 ~ 50 DEG C, and leaching time is 12 ~ 15 hours, and ultrapure electrical conductivity of water is 10 μ S/cm;
(5) the hollow-fibre membrane intermediate being stripped of diluent of step (4) is at room temperature dried, after drying, obtain hollow fiber ultrafiltration membrane.
Above-mentioned preparation method, in described blended polymer solution:
Polyaryl thioether sulfone: Kynoar=1:(0.1 ~ 0.4),
Tetraethylene glycol: 1-METHYLPYRROLIDONE=1:(0.35 ~ 0.6),
(Kynoar+polyaryl thioether sulfone): (Kynoar+polyaryl thioether sulfone+tetraethylene glycol+1-METHYLPYRROLIDONE+polyvinylpyrrolidone)=1:(0.275 ~ 0.435),
Polyvinylpyrrolidone/(Kynoar+polyaryl thioether sulfone)=1:(0.029 ~ 0.09).
Above-mentioned preparation method, the weight average molecular weight of described Kynoar is 370000, and the weight average molecular weight of polyaryl thioether sulfone is 70000, the weight average molecular weight 1100000 of polyvinylpyrrolidone.
In the preparation method of Pvdf Microporous Hollow Fiber Membrane of the present invention, the chemical structural formula of poly arylidene thio-ester is as follows:
Hot method Kynoar (PVDF) hollow fiber ultrafiltration membrane provided by the invention, the formula of its masking and content thereof by percentage to the quality:
First polymer P
1: Kynoar (PVDF) 20 ~ 35wt%
Second polymer P
2: polyaryl thioether sulfone (PASS) 2.5 ~ 10wt%
First diluent D
1: tetraethylene glycol (C8H18O5) 14 ~ 20wt%
Second diluent D2:N-methyl pyrrolidone (NMP) 34 ~ 51wt%
Additive A: polyvinylpyrrolidone (PVPK90) 1 ~ 3wt%
Wherein, the weight average molecular weight of described Kynoar is 370000; The weight average molecular weight of polyaryl thioether sulfone is 70000, the weight average molecular weight 1100000 of polyvinylpyrrolidone.
Meanwhile, wherein the mass ratio of each composition is:
P
2/P
1=0.1~0.4,D
1/D
2=0.35~0.6,(P
1+P
2)/(P
1+P
2+D
1+D
2+A)=(27.5~43.5)wt%,A/(P
1+P
2)=0.029~0.09
The present invention adopt Kynoar (PVDF) good toughness, have good chemical stability, the characteristics such as solvent resistant, acid and alkali-resistance, resistance to oxidation are the preferred material of municipal drinking water treatment process.
The tensile break strength of PVDF material is low, for strengthening the tensile strength of pvdf membrane, adopts polyaryl thioether sulfone (PASS) as the material preparing alloy film in the present invention.Polyaryl thioether sulfone (PASS) is the important kind in poly arylidene thio-ester (PPS) class special engineering plastics, is a kind of modified product of PPS resin.PASS material has high strength, fabulous dimensional stability, excellent decay resistance, and PASS resin has excellent toughness simultaneously, and its vitrification point is up to 220 DEG C, and Heat stability is good is a kind of novel high-performance material of preparing.Adopt that PVDF and PASS is blended prepares alloy film, be convenient to the advantage that performance is respective, obtain the hollow fiber ultrafiltration membrane of function admirable.
The present invention is blended by PVDF and PASS, by the ratio of telomerized polymer, prepares the high strength of the different pore size of three-dimensional interpenetrating polymer network structure, anti-pollution, corrosion resistant hollow fiber alloy film.Blending ratio is determined, at PASS/PVDF blending ratio P by the compatibility studying alloy system
2/ P
1be experimental study display under 10/90,20/80,30/70,40/60,50/50,60/40,70/30 condition, this co-mixing system is partially compatible system, works as P
2/ P
1during >0.5, Miscibility is deteriorated, film forming difficulty, therefore P in the present invention
2/ P
1< 0.5.
The present invention adopts PVPK90 as masking additive, being the hydrophily in order to utilize PVP, improving the contamination resistance of film.
The raw material Kynoar, polyaryl thioether sulfone, tetraethylene glycol, 1-METHYLPYRROLIDONE and the polyvinylpyrrolidone that use in the inventive method are all commercial goods, wherein the manufacturer of Kynoar is SOLVAY(Su Wei) company, the manufacturer of polyaryl thioether sulfone is that Inner Mongol Kuching leads to new high-tech material Co., Ltd, and the purchase shop of other raw material is traditional Chinese medicines group chemical reagent Beijing Co., Ltd.
Below introduce embodiments of the invention:
Embodiment 1:
(1) pretreatment of polymeric material:
By Kynoar PVDF(molecular weight 370000), polyaryl thioether sulfone (molecular weight 70000) carries out drying, the temperature of oven dry 85 DEG C respectively in dryer.
(2) preparation of blended polymer solution:
By the Kynoar P of having dried
1, polyaryl thioether sulfone P
2, tetraethylene glycol D
1, 1-METHYLPYRROLIDONE D
2and after additive PVPK90 weighs by mass percentage, be placed in batching kettle, its mass percent (wt%) is respectively P
1: P
2: D
1: D
2: A=30:6:20:42:2.0 carries out stirring and dissolving at the temperature of 165 DEG C, mixing time 15 hours, and speed of agitator is 100 revs/min, is dissolved into uniform blended polymer solution;
(3) the extruding of hollow-fibre membrane, be shaped:
(3-1) the blended polymer solution in step (2) is sent in double screw extruder by spinning pump, the charging rate of raw material is 15 kgs/hour, and the temperature of extruder 6 sections all sets unanimously, and extrusion temperature is 165 DEG C, screw speed is 100 revs/min, and die temperature is 165 DEG C;
(3-2) blended polymer solution is after double screw extruder is extruded, and successively through filter, spinning pump, extrude from annular die, forms the as-spun fibre of hollow.The external diameter 5 millimeters (mm) of described annular die, internal diameter is 4.2 millimeters (mm).The pressure that annular die center passes into nitrogen is 40 millimeter of water (mmH
2o);
(3-3) above-mentioned hollow as-spun fibre is lower the temperature in the air of 25 DEG C in temperature, and the distance that sky is walked is 40 centimetres (cm), to enter in cold extraction liquid bath through cold extraction liquid cooling curing, through winder rolling, makes hollow-fibre membrane intermediate.Rolling speed 15 ms/min; The mixed liquor that described cold extraction liquid is both water and tetraethylene glycol, the temperature of cold extraction mixed liquor is 40 DEG C, and in cold extraction mixed liquor, the mass percent concentration of water is 0, and the mass percent concentration of tetraethylene glycol is 100wt%;
(4) immersed in reverse osmosis water by the hollow-fibre membrane intermediate in (3), remove the diluent mixture in film, water temperature is 50 DEG C, and leaching time is 13 hours;
(5) at room temperature drying removing the doughnut after diluent in (4), obtaining hollow fiber ultrafiltration membrane goods.
The film outer surface average pore size of these goods is 40nm, and fiber outer diameter is 1.6mm, and wall thickness is 370 μm.Through scanning electronic microscope observation, film section is three-dimensional interpenetrating polymer network, asymmetric pore structure, as shown in Figure 1.Figure 2 shows that the section electromicroscopic photograph of polyvinylidene fluoride hollow fiber ultrafiltration membrane.As can be seen from Figure 2, the section structure of PVDF alloy film is continuous, and even aperture distribution, hole height is through.Fig. 3 is outward flange electromicroscopic photograph, can find out that PVDF alloy film outward flange aperture is less than film section hole, and bore diameter gradient distributes, outer little, greatly interior, effectively can remove the colloid in water, microorganism, macromolecular substances.Illustrate, the contamination resistance of film strengthens, and is convenient to cleaning.Temperature be 25 DEG C, under 0.1MPa pressure, pure water flux is 590L/m
2h, tensile strength of fiber is 7.0MPa, elongation at break 95%.
Main preparation process condition and the film properties of embodiment of the present invention 2-6 is provided below in conjunction with table 1, but the content of each composition of the present invention is not limited to listed numerical value in this table, and it should be noted that, although listed file names with some other parameter in table 1, these Parameter Conditions have been described as necessary condition.For the present invention, the content of core is to improve film formula of liquid, and therefore, other parameters listed file names with in table 1 are just in order to provide about technical information of the present invention in more detail, be all preferred condition, described as necessary condition of the present invention.
Table 1: embodiment 2 ?6 formulation ratio, main preparation process condition and film properties