Summary of the invention
The objective of the invention is to propose a kind of Kynoar porous hollow fiber membrane and method for making thereof that is suitable in membrane biological reactor process, using.
Kynoar porous hollow fiber membrane provided by the invention, its system prescription composition of film and content thereof be by percentage to the quality:
First polymer P
1: Kynoar (PVDF) 25~40%
Second polymer P
2: polymethyl methacrylate (PMMA) 0~5%
The first diluent D
1: diethylene glycol (DEG) acetic acid esters 36~50%
The second diluent D
2: butyl glycol ether 17~24%.
Preferably, wherein said Kynoar (PVDF) weight average molecular weight is 400000, and described polymethyl methacrylate (PMMA) weight average molecular weight is 70000.
Preferably, wherein the mass ratio of each composition is:
P
2/P
1=0~0.2,
D
1/D
2=1.5/1~2.8/1,
P/ (P+D)=(25~40) %, wherein: P=P
1+ P
2, D=D
1+ D
2
Preferred, wherein the mass ratio of each composition is:
Wherein said P
2/ P
1=0.06~0.15,
Wherein said D
1/ D
2=1.8/1~2/1,
Wherein said P/ (P+D)=(30~35) %.
On the other hand, the present invention also provides a kind of preparation method of described hollow-fibre membrane, comprises the following steps:
(1) preliminary treatment of polymeric material
Kynoar, polymethyl methacrylate are carried out drying in dryer, bake out temperature is 50~80 ℃;
(2) preparation of system film blend raw material
With Kynoar P
1With polymethyl methacrylate P
2, diethylene glycol (DEG) acetic acid esters D
1With butyl glycol ether D
2After the weighing, be placed on earlier in the stirred tank in proportion, under 150~180 ℃ temperature, carry out stirring and dissolving, mixing time is 15~25 hours, speed of agitator is 80~120 rev/mins, will dissolve system film Polymer Solution cooling granulation in air uniformly, obtains the blend raw material;
(3) hollow-fibre membrane extrudes, is shaped
(4) diluent leaching
The doughnut intermediate of making is immersed in the reverse osmosis water, remove the diluent mixture in the film, water temperature is 15~40 ℃, and leaching time is 3~6 hours;
(5) dry
The hollow-fibre membrane of making at room temperature dried promptly get the doughnut membrane product.
Preferably, wherein the temperature in the step (1) is 60~70 ℃.
Preferably, wherein the mixing time described in the step (2) is 22~24 hours, and described speed of agitator is 90~100 rev/mins.
Preferably, wherein step (3) may further comprise the steps:
(3-1) will melt extrude in the above-mentioned blend raw material adding double screw extruder;
The melt blended material of (3-2) extruding is extruded from the doughnut annular die through filter and spinning pump, forms the as-spun fibre of hollow;
(3-3) above-mentioned as-spun fibre is lowered the temperature in air, cooling curing in cooling fluid through the winder rolling, is made the doughnut intermediate then.
Preferred, wherein the charging rate of raw material is 8kg/h in the step (3-1), and extruder is divided into 8 sections along the spiro rod length direction and heats, and the temperature range of 8 sections is 125~180 ℃, and screw speed is 120 rev/mins.
Preferred, wherein the external diameter of annular die single hole is 5.5 millimeters (mm) in the step (3-2), and internal diameter is 5.0 millimeters, and temperature is 160~170 ℃, and the annular die centre bore feeds nitrogen, and nitrogen gas pressure is 30~60 millimeter of water (mmH
2O), preferred nitrogen pressure is 30~40 millimeter of water (mmH
2O).
Preferred, wherein in the step (3-3) above-mentioned as-spun fibre in being 5~20 ℃ air, temperature is lowered the temperature, and preferred air themperature is 10~15 ℃, and winder rolling speed is 10~15m/min, and cooling fluid is diethylene glycol (DEG) acetic acid esters C
1, butyl glycol ether C
2, and water C
3Three's mixed liquor, coolant temperature are 5~60 ℃, and the temperature of preferred described cooling fluid is 10~35 ℃.
Preferred, wherein export to the air gap of cooling off liquid level and remain 10~40 centimetres from the mouth mould, preferred the air gap is 15~25 centimetres.
Preferably, wherein the ratio of three's mixing is (mass ratio): (C
1+ C
2)/C
3=1/1~5/1, C
1/ C
2=1.5/1~2.8/1.
Preferred, wherein said (C
1+ C
2)/C
3=1.5/1~4/1, C
1/ C
2=1.8/1~2/1.
Preferably, wherein the water temperature described in the step (4) is 20~30 ℃, and the time is 4~5 hours.
The Kynoar (PVDF) that the present invention adopts has outstanding anti-solvent, acid and alkali-resistance, resistance to oxidation, characteristic such as weather-proof, excellent hear resistance and toughness are arranged, particularly the fluorine element in the material has stronger negative polarity, makes PVDF be difficult for being adsorbed with organic pollutants, show good anti pollution property, is the preferred material of MBR technology.
Yet because PVDF material hydrophobicity is strong, the surface can be low, and hydrone is had repulsive interaction, and the present invention adopts hydrophilic high molecular material blend with it, thereby improves the hydrophily of pvdf membrane effectively.
On this basis, the present invention also proposes a kind of new mixed diluent system, this system is made up of two component mixed solvents, one of them component is the solvent or the cosolvent of polymer, another component is the non-solvent of polymer, by adjusting the different proportion between the two in the mixed diluent, come interactional power between telomerized polymer and the diluent, and then the phase-separated state of change polymer/diluent system, reach the purpose of regulation and control membrane pore structure, prepare the film of required three-dimensional net structure.
On this basis, the present invention adopts the mixed liquor of diluent and water as cooling fluid, by changing the composition and the temperature of cooling fluid, regulate the aperture on film surface and the size of percent opening, super, the micro-filtration membrane of the PVDF that preparation has the hole density gradient improves film pollutant is held back characteristic and the stifled ability of anti-soil.
On the other hand, preparation method provided by the invention, utilized the principle of " high-temperature digestion, low temperature phase-splitting ", with polymer and diluent at high temperature mixed dissolution become uniform casting film solution, again solution is made tabular, tubulose and hollow fiber after, through cooling, cooling, casting solution system generation liquid-liquid or solid-liquid are separated, after polymeric system solidifies, again the diluent extraction is removed, promptly obtain porous diffusion barrier.This method is extensive to the adaptability of high polymer material, not only is suitable for conventional high polymer, and it is poor even because highly crystalline also to be suitable for dissolved separating property, undissolvable polymer under common normal temperature.Because film-forming temperature is higher relatively, the concentration of corresponding filming polymer is also higher relatively, can avoid occurring non-solvent and cause the big cavity structure of the sort of finger-like that phase separation method is made, it is even to make pore structure, the three-dimensional net structure of Guan Tonging highly, therefore the film strength height can adapt to the requirement of MBR technology.Super, the micro-filtration membrane of the PVDF doughnut that adopts the present invention to prepare has excellent chemical stability, and antipollution, the hollow-fibre membrane that intensity is high can provide high performance film product for MBR technology.
In addition, diluent is non-water-soluble in traditional filming technology, needs to adopt alcohol, ketone, ester class organic solvent as extractant after film is shaped, and this technology is except own expense height with an organic solvent, also to add the cost that reclaims extractant, can't avoid the discharging of organic pollution.Among the present invention since mixed diluent system in two components be water miscible, so just can adopt water as come together diluent (cosolvent) in the membrane of extractant, can avoid the trouble that adopts organic solvent to bring, also can reduce the manufacturing cost of film as extractant.
Hollow-fibre membrane external diameter of the present invention is 1.1~1.3 millimeters, wall thickness is 260~315 nanometers, membrane pore structure is three-dimensional interpenetrating polymer network structure (seeing accompanying drawing 1), the film section is asymmetric, film outmost surface aperture minimum, the densification of outer wall edge hole, the aperture is less, the aperture increases gradually from outside to inside, and inner surface aperture maximum is a kind of super, micro-filtration membrane with density gradient pores section structure.Super, micro-filtration membrane of the present invention has good chemically-resistant cleaning and hydrophily, and intensity height, big, the good toughness of flux have good contamination resistance, are adapted at most using among the MBR.City domestic sewage, industrial wastewater can be carried out advanced treating, water reuse water standard in reaching.Compare with traditional Wastewater Treated by Activated Sludge Process waste water, treatment effeciency improves more than 3 times, and effluent quality is good, and chemical oxygen consumption (COC) in the waste water (COD) clearance is greater than 98%, ammonia-nitrogen removal efficiency height, the treatment facility compactness, take up an area of less, automaticity height, convenient operation and management.
The specific embodiment
For a more detailed description below in conjunction with embodiment to the present invention, but described embodiment is not construed as limiting the invention.
Embodiment 1
The quality percentage is that 35% PVDF oven dry resin and mass percent are the polymer blend that 2.1% polymethyl methacrylate oven dry resin is formed, join in the mixed solvent of diethylene glycol (DEG) acetic acid esters and butyl glycol ether composition, wherein the quality percentage of diethylene glycol (DEG) acetic acid esters is 40.4%, and the quality percentage of butyl glycol ether is 22.5%.Said mixture is joined in the stirred tank, is to carry out stirring and dissolving after 24 hours under 120 rev/mins of kind conditions at 180 ℃ temperature, rotating speed, and cooling granulation in air obtains blended material.Charging rate with 8kg/h joins preprepared blend composition in the double screw extruder.The temperature in extruder 1-8 district is respectively 125 ℃, 140 ℃, 155 ℃, 170 ℃, 180 ℃, 180 ℃, 180 ℃, 170 ℃, and screw speed is 120 rev/mins.After mixed material melt extrudes in dual-screw-stem machine, enter four hole annular dies by filter and spinning pump and extrude, make the hollow as-spun fibre, a mouthful mould single hole external diameter is 5.5mm, and internal diameter is 5mm, and temperature is 170 ℃, and it is 30mmH that a mouthful mould centre bore feeds pressure
2The N of O
2Gas.As-spun fibre is in temperature is 10 ℃ air, and idling stopping distance (the air gap) is 25cm, enters into the cooling fluid cooling curing, with the speed rolling of 15m/min.Wherein contain 20% water in the cooling fluid, 28.6% butyl glycol ether, 51.4% diethylene glycol (DEG) acetic acid esters, the temperature of cooling fluid is 35 ℃.Preformed hollow-fibre membrane leaches and at room temperature dries after 5 hours in 30 ℃ reverse osmosis water, makes doughnut membrane product of the present invention.By scanning electronic microscope observation, the inierpeneirating network structure of the section of film, asymmetric milipore filter, film surface average pore size is 48 nanometers (nm), and the fiber external diameter is 1.3 millimeters (mm), and wall thickness is 315 microns (μ m).Under temperature was 25 ℃, 0.1MPa pressure, pure water flux was 750L/m
2H, tensile strength of fiber are 8.5MPa, elongation at break 90%.
Provide main preparation process condition and the film properties of embodiment of the invention 2-5 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, for a person skilled in the art, fully can be in table rationally summarize and reasoning on the basis of listed number range, and of particular note, although listed file names with some other parameter in the table 1, this this parameter condition is described as necessary condition.For the present invention, the content of core is to improve the film formula of liquid, and therefore, other parameters that list file names with in the table 1 are just in order to provide in more detail about technical information of the present invention, all be preferred condition, described as necessary condition of the present invention.
Table 1: the formulation ratio of embodiment 2-5, main preparation process condition and film properties
Wherein, film properties data relevant in the table 1 are hollow-fibre membrane is cooled off brittle failure in liquid nitrogen after, and the use stereomicroscope is taken a picture to the section of described film and measured, and method is as follows:
(1) Micro-Structure Analysis of film
Sample is made in film brittle failure in liquid nitrogen, sample is fixed on the sample platform, under the voltage of 30KV, adopt SEM (QuanTa 200FEG) observation film section and surface texture.
(2) film-strength test
Film is made the sample silk, and two ends reinforce with medical proof fabric.On universal testing machine, stretch in (GT-TS-2000, GOTECHCO, Taiwan) hot strength of test membrane silk and elongation at break.
(3) pure water flux of film test
Testing arrangement is by external-compression type ultrafilter, N
2Gas cylinder, vacuum tank are formed, and hollow-fibre membrane is packaged into specimen with epoxide-resin glue, and the employing temperature is 25 ℃ a deionized water, tests under the pressure of 0.1MPa.
Pure water flux is defined as the pure water quality that sees through at following unit interval of above-mentioned test condition, elementary membrane area.
That is: J=W/AT
Wherein, J is pure water flux (kg/m
2H), A is the external surface area (m of film
2), W is the permeable amount (kg) of film, T is testing time (h).
(4) mensuration of the external diameter of hollow-fibre membrane, internal diameter and wall thickness
Any corresponding improvement of carrying out on basis of the present invention does not all break away from thought of the present invention, all falls into the scope of protection of the invention.