CN104437138A - Polysulfonate separation membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a polysulfone separation membrane and a preparation method thereof. The casting solution of the polysulfone separation membrane is composed of the following components in mass ratio: the mass ratio of membrane-making raw material, solvent, non-solvent and modification additive is 10-20:50-85:5-25:0 -15. The preparation method of the polysulfone separation membrane comprises the following steps: preparation of casting solution, mold making by non-solvent-induced phase separation, coagulation bath solidification and rinsing and drying. During the preparation process of the polysulfone separation membrane, the temperature of the casting solution, the coagulation bath and the ambient atmosphere, the ambient humidity and the residence time are precisely controlled to realize the sponge-like gradient structure of the membrane pores. The preparation method of the polysulfone separation membrane has a simple process and is convenient for industrial scale production.

Description

A kind of polysulfone separation membrane and preparation method thereof

technical field

The invention relates to the field of separation membranes, in particular to a polyether separation membrane and a preparation method thereof.

Background technique

Membrane separation technology uses pressure as the driving force to selectively separate mixed liquids through membrane pore size and surface affinity. Compared with traditional separation methods, membrane separation has high selectivity, low energy consumption, high separation efficiency and convenience. Achieve automation and other advantages. Thermally induced phase separation (thermal method) and non-solvent induced phase separation (wet method) are two common methods for preparing separation membrane materials. The wet spinning process is simple, the process is flexible and controllable, and the energy consumption is low. more widely applied. The structure of the separation membrane prepared by wet method is often inhomogeneous macroporous structure. This inhomogeneous structure will lead to low mechanical strength of the membrane, and it is difficult to improve the permeability and retention performance at the same time. The separation membrane with a sponge-like structure has a uniform structure, good support strength of the micro-nano network pore structure, small collapse of the membrane pores during the drying process, and large dry flux; the membrane has relatively high mechanical strength, surface wear resistance, permeability and retention The performance can be controlled according to the needs, and can meet the complex treatment medium and treatment process; the polyethersulfone structure of the sponge structure has better blood compatibility. The gradient pore sponge structure is a new type of membrane pore structure with a single separation layer. On the membrane section, the separation pore diameter of the membrane separation skin is the smallest, and the pore diameter increases with the increase of the distance from the separation layer. In the filtration process, after the permeation medium passes through the separation layer, the flow resistance gradually decreases, the separation speed is fast, and the membrane flux is high; particles with a pore size equivalent to the membrane pores can be carried out under the washing of the filter medium after passing through the separation layer. It can effectively avoid the decrease of membrane flux caused by blocking the membrane pores, and has certain anti-fouling properties.

Chinese patent application publication number 103191655A discloses a method for preparing a composite polyvinylidene fluoride hollow fiber membrane, in which maleic anhydride cross-linked polyethylene glycol is coated on the surface of the polyvinylidene fluoride hollow fiber membrane. Since polyethylene glycol is hydrophilic, the surface layer of the composite membrane prepared by curing in water after crosslinking has a sponge-like structure. The Chinese patent application with publication number 102131566A discloses the preparation of polyolefin microporous membranes with asymmetric structure by UV-induced in-situ polymerization. In the process of in-situ synthesis, the membrane-forming polymer material is molded at one time during the synthesis process to form a sponge-like structure. The membrane preparation process of these two methods is simple, but it is difficult to achieve large-scale production.

The Chinese patent application with the publication number 101484234A and the Chinese patent application 103608092A disclose a method for preparing a polyarylamide (polysulfone, polyethersulfone) ultrafiltration membrane with gradient sponge-like pores, which is realized by hydrophilic additives and non-solvents in the casting solution. The membrane pores are transformed from macropores to sponge-like pore structures. Hydrophilic additives are necessary additives for the transformation of the membrane structure and are the key factors leading to the transformation of the membrane structure. Partial macropore structures still appear in the middle region of the prepared membrane cross section.

Chinese patent application publication number 101623605A discloses a method for preparing a sponge-like polyvinylidene fluoride membrane with high throughput and high rejection rate. It fills the polyvinylidene fluoride casting solution with inorganic nanoparticles, adjusts the solvent-non-solvent exchange rate during the solidification process of the casting solution by controlling the pre-evaporation time and the coagulation bath temperature, and prepares a hollow polyvinylidene fluoride with a fully spongy structure. Fiber membrane.

The Chinese patent application with publication number 101890307A discloses a polyvinylidene fluoride hollow fiber membrane with gradient density and its preparation method. It prepares a polyvinylidene fluoride hollow fiber membrane with a gradient pore structure through a hydrophilic polymer and a diluent propylene glycol or ethylene glycol diacetate through a thermally induced phase separation method to control the residence time of the casting solution in the air A solidified temperature gradient difference is formed to form a target gradient pore structure separation membrane.

Chinese patent application publication number 103816818A discloses a hollow fiber membrane with a superhydrophilic gradient pore structure and a preparation method thereof. In addition to the film-forming polymer material, the casting solution also adds an amphiphilic block polyether modified silicone material. By adjusting the length of the hydrophilic block and hydrophobic block in the amphiphilic block copolymer And the relative ratio to control the size and density distribution of the membrane pores, and water or other non-solvents are used to control the state of the casting solution to realize the transformation of the membrane structure from a perforated structure to a uniform sponge-like structure, and the pore size distribution gradually changes along the radial direction.

It can be seen from the above that in the prior art, it is difficult to control the structure of the wet membrane, and it is difficult to significantly improve the performance of the prepared membrane. Therefore, both the separation membrane and its preparation method need to be further improved.

Contents of the invention

In view of this, it is necessary to provide a polysulfone separation membrane and a preparation method thereof for the above-mentioned problems.

In order to realize the foregoing invention object, the present invention adopts following technical scheme:

A polysulfone separation membrane, the casting solution is composed of the following components in mass ratio: the mass ratio of film-making raw material, film-making solvent, non-solvent, and modifying additive is 10-25:50-85:5- 25:0-15.

Preferably, the mass ratio of film-forming raw materials, film-forming solvents, non-solvents, and modifying additives is 10-20:50-70:10-20:5-12.

Preferably, the membrane-forming raw material is one or a mixture of polysulfone and polyethersulfone.

Preferably, the film-forming solvent is one or a mixture of nitrogen methylpyrrolidone, dimethylformamide and dimethylacetamide.

Preferably, the modifying additive is polyethylene glycol, polymethylpyrrolidone, Span 80 or other amphiphilic block polymers.

Preferably, the non-solvent is LiCl solution, HCl solution, NaOH solution, _H2SO4 solution, ammonia water or sodium dodecylsulfonate aqueous solution with a mass fraction of 0.5-3%, or Span 40, acetic acid _, acetone , tetrahydrofuran, citric acid, ethanol, isopropanol, butyric acid, n-octanol or Tween 20 or a mixture of two in a mass ratio of 1:1-1:3.

A method for preparing a polysulfone separation membrane, comprising the following steps:

1) Mix the film-making raw material, film-making solvent, non-solvent and modifying additive, stir and dissolve at 10-120°C, the weight ratio of the film-making raw material to the film-making solvent, non-solvent, and modifying additive is 10-20:50-85:5-25:0-15;

2) Extrude the above-mentioned mixed solution into a film through a film-making device in a constant air humidity atmosphere of 20%-100% by a non-solvent-induced phase separation method; preferably, at a constant temperature of 60%-85% at 25-50°C Saturated humidity to prepare the above separation membrane;

3) The residence time of the film in the air is 0-600s or the residence distance is 0-50cm, and then enters the coagulation bath to solidify to form a film; preferably, the residence time of the film in the air is 0-100s or the residence distance is 0-30cm;

4) The cured film is treated with a post-treatment solution before or after rinsing, and then dried naturally at room temperature.

Preferably, the polysulfone separation membrane is a polysulfone separation membrane with a sponge-like gradient pore structure.

Preferably, the post-treatment liquid is NaCl, HCl, NaOH, dimethylformamide, methylpyrrolidone, tetrahydrofuran, ethanol, sodium acetate, Span 40, KAl(SO ₄ ) ₂ ·12H ₂ O, acetic acid, An aqueous solution of one or more mixtures of citric acid, NaClO, HClO, Tween 20, glycerol and sodium dodecylsulfonate.

Preferably, the coagulation bath is ethanol, an aqueous solution of a film-forming solvent or an aqueous solution with a pH of 4-10. The aqueous solution with a pH of 4-10 includes any aqueous solution of chemical substances dissolved in water with a pH of 4-10, such as an aqueous solution of sodium bicarbonate.

Preferably, the polysulfone-based separation membrane may be a flat sheet membrane, a tubular membrane, or a hollow fiber membrane, or any other shape of membrane different from hollow fiber membranes, tubular membranes, flat sheet membranes, and spherical membranes.

More preferably, the polysulfone separation membrane is spherical.

Preferably, the polysulfone separation membrane has a support layer or has no support layer.

Preferably, the polysulfone separation membrane has a thickness of 50-5000 microns. More preferably, the polysulfone separation membrane has a thickness of 100-500 microns.

The section of the sponge-like structure separation membrane is an asymmetric continuous network micro-nanopore structure, and the gradient pores are such that the diameter of the network-shaped micro-nanopore gradually increases or decreases along one side of the membrane. porous structure. A certain amount of non-solvent is added to the membrane-making liquid for the separation membrane. Controlling the dissolution state of the polymer by the solvent in the casting solution or the pH difference between the casting solution and the coagulation bath through acidic non-solvent and modifying additives can precisely control the phase separation speed and phase separation process of the casting solution and avoid the membrane cross-section Form finger-like pores and macropore structure defects, and realize the transformation of the membrane pore structure from the typical discontinuous finger-like pore structure of the non-solvent-induced phase separation method into continuous sponge-like micro-nanopores. Uniform gradient distribution along the radial direction. And because the membrane pore structure changes from a heterogeneous phase to a homogeneous phase structure, the defects on the membrane surface are effectively reduced, the mechanical strength and wear resistance are improved, and the service life is prolonged. Since the membrane pore diameter gradually increases from the intercepting layer, particles with a diameter equivalent to the intercepting pore diameter of the membrane can pass through the intercepting layer and enter the permeate smoothly under the scouring of the water flow during use, effectively reducing the membrane pore size. Reduce the degree of clogging and improve the efficiency of membrane treatment.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The polysulfone separation membrane prepares a separation membrane with a sponge-like gradient pore structure by adjusting the content and type of non-solvent in the casting solution. The non-solvent content in the separation membrane casting liquid is different in different polymers, the addition amount of different solvents and non-solvents is different, and the same polymer of different grades is also different. Precisely fine-tune the membrane formulations of different brands of raw materials through the dissolution index (viscosity, turbidity or pH) of the casting solution, accurately control the membrane parameters, and ensure that the membranes produced in different batches have stable and uniform structures and properties, which can be easily realized Strict control of membrane quality is of great significance to production.

(2) The preparation method of the polysulfone separation membrane is to prepare a polysulfone separation membrane with a sponge-like gradient pore structure by controlling the liquid phase separation process of the cast membrane through non-solvent and spinning process. During the preparation process of the polysulfone separation membrane, the membrane pores have a sponge-like gradient structure by precisely controlling the temperature of the casting solution, the coagulation bath, and the ambient atmosphere, as well as the ambient humidity and residence time. The preparation method has simple process and is convenient for industrial scale production. It provides another alternative, inexpensive and easy-to-implement method for wet-process membrane structure regulation and directional transformation, and solves the problems in the prior art that the wet-process membrane structure is difficult to control and the performance of the prepared membrane is difficult to significantly improve.

Description of drawings

Fig. 1 is a scanning electron micrograph of a polyethersulfone flat-panel membrane prepared in Example 1 of the present invention.

Detailed ways

The formulation and preparation method of the polysulfone separation membrane described in the present invention are also applicable to flat membranes, tubular membranes, hollow fiber membranes and any other membranes with different geometric structures, including membranes with support layers and membranes without support layers. As it is possible to make many possible embodiments without departing from the spirit and scope of the invention, it should be understood that all cases set forth herein are presented by way of illustration and not in limitation of the scope of the invention. The reagents used in the present invention, except that there are special instructions, all are commercially available analytical pure reagents, the cross-sectional structure is tested by scanning electron microscope (JSM-6390, Japan Electronics Co., Ltd.). The rate test device is self-made in the laboratory; the viscosity of the feed liquid is tested by a rotational viscometer (NDJ-8S, Shanghai Pingxuan Scientific Instrument Co., Ltd.); (Shanghai Mapada Instrument Co., Ltd.) quantitative analysis.

Example 1

Mix the mixture of polyethersulfone, dimethylformamide, acetic acid and glycerin (the mass ratio of acetic acid and glycerol is 1:1) and PVPK30 according to the mass ratio of 15:60:12:13, and stir in an oil bath at 85°C for 24 Hours to prepare a clear and transparent solution, reduce the stirring speed and continue to stir for 2 hours to defoam. Control the humidity of the scraping film atmosphere to be stable at 55%, set the gap between the blades of the flat-panel scraping machine to 0.2 microns, spread the prepared casting solution on the side of the glass substrate, start the flat-panel scraping machine, and set the scraper at a speed of 100mm/s Speed operation, after the scraper stops running, stay in the air for 25s, and then transfer to 0.1mol/L sodium bicarbonate aqueous coagulation bath to prepare polyethersulfone flat membrane, rinse in pure water for 48 hours, every 2 -Change the water once every 5 hours, then soak in a mixed solution of NaOH, citric acid and glycerin for 4 hours for post-treatment, and place the prepared polyethersulfone membrane at room temperature for 24 hours to dry in the shade.

Example 2

Mix polysulfone, dimethylacetamide, and PEG6000 at a mass ratio of 18:68:15, stir in an oil bath at 60°C for 24 hours to prepare a clear and transparent solution, reduce the stirring speed and continue stirring for 2 hours to defoam, then add dropwise Hydrochloric acid until the pH of the casting solution is between 4-5, at this time the mass ratio of polysulfone, dimethylacetamide, PEG6000, and hydrochloric acid in the casting solution is 17:66:14:3. Control the humidity of the scraping film atmosphere to be stable at 100%, set the gap between the blades of the flat-panel film-hanging machine to 0.5 microns, spread the prepared casting liquid on the side of the glass substrate, start the flat-panel film-scraping machine, and the scraper at a speed of 100mm/s Speed operation, after the scraper stops running, stay in the air for 1min, then transfer to 0.1mol/L sodium bicarbonate aqueous coagulation bath, prepare polyethersulfone flat membrane, rinse in pure water for 48 hours, rinse every 2 -Change the water once every 5 hours, then soak in a mixed solution of sodium dodecylsulfonate, citric acid and glycerin for 4 hours for post-treatment, and place the prepared polyethersulfone membrane at room temperature for 24 hours to dry in the shade.

Example 3

Mix polyethersulfone, methylpyrrolidone, and butyric acid in a mass ratio of 20:75:5, stir in an oil bath at 30°C for 24 hours to prepare a clear and transparent solution, reduce the stirring speed and continue stirring for 2 hours to defoam, and then transfer to the cast film Add isopropanol drop by drop to the solution, and monitor the viscosity change of the casting solution in real time, stop adding until the viscosity of the casting solution reaches a minimum value, at this time, polyethersulfone, methylpyrrolidone, butyric acid and The mass ratio of propanol is 17:66:5:12. Control the humidity of the scraping film atmosphere to be stable at 55%, set the gap between the blades of the flat-panel scraping machine to 0.2 microns, spread the prepared casting solution on the side of the glass substrate, start the flat-panel scraping machine, and set the scraper at a speed of 100mm/s Run at high speed, transfer to 0.1mol/L sodium bicarbonate aqueous coagulation bath immediately after the scraper stops running, prepare polyethersulfone flat membrane, rinse in pure water for 48 hours, change the water every 2-5 hours during the rinsing process , and then soaked in a mixed solution of Span 40, citric acid and glycerin for 4 hours for post-treatment, and the prepared polyethersulfone membrane was placed at room temperature for 24 hours to dry in the shade.

Example 4

Mix polysulfone, dimethylacetamide, and PEG6000 at a mass ratio of 17:68:15, stir at room temperature for 24 hours to prepare a clear and transparent solution, reduce the stirring speed and continue stirring for 2 hours to defoam, then add butyric acid dropwise Until the pH of the casting solution is between 4-5, the mass ratio of polysulfone, dimethylacetamide, PEG6000, and butyric acid in the casting solution is 17:66:14:3. select The hollow fiber membrane spinneret of the hollow fiber membrane is prepared on the hollow fiber spinning machine, the internal liquid of spinning is 0.1mol/L sodium bicarbonate aqueous solution, the coagulation bath is water, the internal liquid and the coagulation bath are both normal temperature, and the spinning The head is 30cm away from the water surface, the humidity of the scraping membrane atmosphere is controlled to be stable at 85%, the spinning machine is started, the silk output speed is 80cm/min, and the prepared polysulfone hollow fiber membrane is rinsed in pure water for 48 hours. During the rinsing process, every 2-5 Change the water every hour, then soak in the mixed solution of hydrochloric acid/hypochlorous acid and glycerin for 4 hours for post-treatment, and place the prepared polyethersulfone membrane at room temperature for 24 hours to dry in the shade.

Example 5

Mix polyethersulfone, dimethylformamide and PEG6000 at a mass ratio of 17:70:13, stir in an oil bath at 85°C for 24 hours to prepare a clear and transparent solution, reduce the stirring speed and continue stirring for 2 hours to defoam. Control the humidity of the scraping film atmosphere to be stable at 55%, set the gap between the blades of the flat-panel film-hanging machine to 0.2 microns, spread the prepared casting solution on the side of the glass substrate, start the flat-panel film-hanging machine, and set the scraper at a speed of 100mm/s Speed operation, after the scraper stops running, stay in the air for 1.5min, then transfer to 0.1mol/L sodium bicarbonate aqueous coagulation bath, prepare polyethersulfone flat membrane, rinse in pure water for 48 hours, rinse every Change the water every 2-5 hours, then soak in the mixed solution of NaOH, citric acid and glycerin for 4 hours for post-treatment, and place the prepared polyethersulfone membrane at room temperature for 24 hours to dry in the shade.

The polyethersulfone membrane obtained in each of the above implementation examples was brittle broken by liquid nitrogen and then sprayed with gold. The cross-sectional structure was observed by SEM, and the pure water flux was tested by a self-made permeation flux tester, using 1000ppm BSA phosphate buffer solution as the permeate Test retention. FIG. 1 is a scanning electron micrograph (SEM) of a section of a polysulfone flat membrane in Example 1. The polysulfone separation membrane of the present invention prepares a separation membrane with a fully sponge-like gradient pore structure by adjusting the content and type of non-solvent in the casting solution or the pH gradient between the casting solution and the coagulation bath. The preparation method is simple in process, Easy to control the structure of the membrane. The cross-sectional pore diameter of the obtained flat membrane gradually decreases from one surface to the opposite surface, showing a gradient distribution. The minimum pore diameter of the dense surface is about 0.1 μm, the surface pore diameter of the loose surface is about 2.5 μm, and the surface aperture ratio is about 25:1. The volume can reach about 3000L/m ² ·h·atm.

The performance test results of the polysulfone separation membranes obtained in each embodiment of table 1

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. a polysulfones diffusion barrier, is characterized in that, its casting solution is made up of the component of following mass ratio: the mass ratio of masking raw material, casting solution, non-solvent, property-modifying additive is 10-20:50-85:5-25:0-15.

2. polysulfones diffusion barrier according to claim 1, is characterized in that, the mass ratio of described masking raw material, casting solution, non-solvent, property-modifying additive is 10-20:50-70:10-20:5-12.

3. polysulfones diffusion barrier according to claim 1, is characterized in that, described masking raw material are a kind of in polysulfones and polyether sulfone or both mixtures; Described casting solution is one or several the mixture in nitrogen methyl pyrrolidone, dimethyl formamide and dimethylacetylamide; Described property-modifying additive is polyethylene glycol, poly-methyl pyrrole alkane ketone, class 80 of department or other amphipathic block polymers; Described non-solvent is the LiCl solution of mass fraction 0.5-3%, HCl solution, NaOH solution, H2SO4 solution, ammoniacal liquor or sodium dodecyl sulfate aqueous solution, or is a kind of or two kinds of mixtures according to mass ratio 1:1-1:3 in class 40 of department, acetic acid, acetone, oxolane, citric acid, ethanol, isopropyl alcohol, n-butanol, n-octyl alcohol or polysorbas20.

4. a preparation method for polysulfones diffusion barrier, is characterized in that, comprises the following steps:

1) masking raw material, casting solution, non-solvent and property-modifying additive are mixed, stirring and dissolving under 10-120 DEG C of condition, the mass ratio of described masking raw material and casting solution, non-solvent, property-modifying additive is 10-20:50-85:5-25:0-15;

2) by phase separation method, above-mentioned mixed solution is passed through membrane equipment film extrusion in the constant air humidity atmosphere of 20%-100%;

3) time of staying is 0-600s or stops distance for 0-50cm film in atmosphere, then enters film-forming in coagulating bath;

4) film solidified is processed by aftertreatment fluid before rinsing or after rinsing, then naturally dries at ambient temperature.

5. the preparation method of polysulfones diffusion barrier according to claim 4, it is characterized in that, described post-treatment solution is by NaCl, HCl, NaOH, dimethyl formamide, methyl pyrrolidone, oxolane, ethanol, sodium acetate, class of department 40, KAl (SO ₄) ₂12H ₂the aqueous solution of one or several mixtures in O, acetic acid, citric acid, NaClO, HClO, polysorbas20, glycerine and dodecyl sodium sulfate; Described coagulating bath is ethanol, the casting solution aqueous solution or pH are the aqueous solution of 4-10.

6. the preparation method of polysulfones diffusion barrier according to claim 4, is characterized in that, described polysulfones diffusion barrier is spongy graded pore structure polysulfones diffusion barrier.

7. the preparation method of polysulfones diffusion barrier according to claim 4, it is characterized in that, described polysulfones diffusion barrier can be Flat Membrane, tubular membrane or hollow-fibre membrane, or from the film of hollow-fibre membrane, tubular membrane, other shape any that Flat Membrane is different with spherical film.

8. the preparation method of polysulfones diffusion barrier according to claim 7, is characterized in that, described polysulfones diffusion barrier is spherical.

9. the preparation method of polysulfones diffusion barrier according to claim 4, is characterized in that, described polysulfones diffusion barrier has supporting layer or without supporting layer.

10. the preparation method of polysulfones diffusion barrier according to claim 4, is characterized in that, the thickness of described polysulfones diffusion barrier is 50-5000 micron.