CN113877439B

CN113877439B - Polymer filter membrane mixed by coarse and fine fibers and preparation method and application thereof

Info

Publication number: CN113877439B
Application number: CN202010638272.XA
Authority: CN
Inventors: 贾建东
Original assignee: Hangzhou Kebaite Technology Co ltd
Current assignee: Hangzhou Kebaite Technology Co ltd
Priority date: 2020-07-03
Filing date: 2020-07-03
Publication date: 2024-04-16
Anticipated expiration: 2040-07-03
Also published as: CN113877439A

Abstract

The invention provides a polymer filter membrane mixed by coarse and fine fibers, a preparation method and application thereof, wherein the filter membrane comprises a coarse fiber layer and a fine fiber layer; the average diameter of the coarse fibers in the coarse fiber layer is 350-800nm, and the average pore diameter is 400-1500nm; the average diameter of the fine fibers in the fine fiber layer is 20-75nm, and the average pore diameter is 40-140nm. The nanometer holes of the fine fiber layer also have stronger adsorption effect, so that the interception effect of the filter membrane is further improved; the filter membrane has the advantages of larger flow rate, shorter filtering time, higher filtering precision, stronger interception effect on impurity particles with the particle size of 0.8-200nm, larger tensile strength and elongation at break, wide application range and particular suitability for ultra-pure water filtration in the ink field and the semiconductor field; in addition, the invention also provides a preparation method of the filter membrane, which is quick and effective, simple to operate, green and environment-friendly and suitable for large-scale popularization.

Description

Polymer filter membrane mixed by coarse and fine fibers and preparation method and application thereof

Technical Field

The invention relates to the technical field of filtering membrane materials, in particular to a polymer filtering membrane mixed by coarse and fine fibers, and a preparation method and application thereof.

Background

The membrane separation technology is one of the modern high and new technologies developed in recent years, and uses a functional separation membrane as a filter medium to realize the high separation and purification of liquid or gas. As a novel separation method, the membrane separation technology has the advantages of high selectivity, simple operation, low energy consumption, small occupied area, no pollution and the like.

The core of the membrane separation technology is a filter membrane. A filter membrane refers to a barrier layer that limits and transmits components in a specific fashion within one fluid phase or back to two fluid phases, thereby separating the fluid phases into two parts. It has at least two interfaces; through which the fluid separated on both sides by the filter membrane is contacted. The filter membrane has a smaller pore size and a narrower pore size distribution than conventional filter media. The filter membrane can be classified into a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane according to the pore size of the filter membrane. Wherein the aperture of the microfiltration membrane is about 0.01-1 mu m, so that most of impurities such as particles, bacteria and the like in the water can be effectively removed; the aperture of the nanofiltration membrane and the reverse osmosis membrane is very small, about a few angstroms, and ions can be removed from water, so that the purposes of desalting sea water and brackish water are achieved;

The aperture of the ultrafiltration membrane is between the microfiltration membrane and the nanofiltration membrane, generally tens to hundreds of nanometers, so that the fractionation and purification of macromolecules such as proteins can be easily realized, and viruses and thermoplasma in water can be removed; currently, ultrafiltration membranes are widely applied to the fields of purification and concentration of biochemical reagents, industrial wastewater treatment, drinking water preparation, material recovery and the like. However, the aperture of the ultrafiltration membrane is smaller, so that the flow rate of the ultrafiltration membrane is smaller, the filtration time is longer, and the time cost is too high; meanwhile, the mechanical strength of part of the ultrafiltration membrane is poor, which greatly limits the development and application of the ultrafiltration membrane.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide a polymer filter membrane mixed by coarse and fine fibers, a preparation method and application thereof, wherein the filter membrane is an ultrafiltration membrane capable of intercepting impurity particles with the particle size of 0.8-200 nm; meanwhile, the filter has a faster flow rate and shorter filtering time; meanwhile, the filter membrane also has higher tensile strength and elongation at break.

In order to achieve the above purpose, the present invention provides the following technical solutions: a coarse and fine fiber commingled polymeric filter membrane comprising a body having a non-oriented tortuous passageway therein, the body comprising a coarse fiber layer and a fine fiber layer; a side surface area of the coarse fiber layer forms a first porous surface, and a side surface area of the fine fiber layer facing away from the first porous surface forms a second porous surface; the average diameter of the crude fibers in the crude fiber layer is 350-800nm, and the average pore diameter is 400-1500nm; the average diameter of the fine fibers in the fine fiber layer is 20-75nm, and the average pore diameter is 40-140nm.

In the membrane body structure of the filter membrane provided by the invention, the whole filter membrane body can be clearly seen to contain more continuous fibers in the thickness direction, and continuous means that all the fibers are integrally connected with each other without using other adhesives or other bonding materials; the fiber elements cannot be separated from each other without tearing; the fibers are connected with each other, so that a porous network structure is formed, and the porous network structure is convenient for fluid to pass through, so that the purpose of filtration is achieved; although all are fibers, it is apparent that there is a large difference in the diameter of the different fibers; in one of the regions, the diameter of the fibers is mostly large, in the range of 350-800nm (0.35-0.8 μm), so-called coarser fibers, the pores are also large in this region, and the average pore diameter is 400-1500nm (0.4-1.5 μm), so this region is called coarse fiber layer; in the other region, the diameter of the fibers is mostly smaller, namely, the fibers are only 20-75nm, namely, the fibers are thinner, the holes in the region are smaller, and the average hole diameter is 40-140nm, so that the region is called a fine fiber layer; the existence of coarse fiber can greatly improve the mechanical strength of the filter membrane, and the existence of fine fiber can further improve the mechanical strength of the filter membrane, so that the filter membrane has larger tensile strength and elongation at break. When the filter membrane filters fluid, the fluid passes through the coarse fiber layer and then the fine fiber layer; the larger fiber structure is favorable for intercepting particle impurities with larger particle size, the smaller fiber structure is favorable for intercepting particle impurities with smaller particle size, and finally nanoscale impurity particles can be intercepted, so that the effective interception rate of the filter membrane to the impurity particles can be greatly improved, and the filter precision is high; meanwhile, due to the existence of the crude fiber layer, the flow speed of the filter membrane is larger, the filtering time is shorter, the time cost is lower, and the economic benefit is higher; in addition, the nano-scale holes of the fine fiber layer have a strong adsorption effect, can adsorb impurity particles with small particle size, further improve the retention efficiency, and finally enable the filter membrane to be capable of intercepting the impurity particles with the particle size of 0.8-200nm, and is particularly suitable for intercepting the impurity particles with the particle size of 20-200nm, so that the filter membrane is particularly suitable for ultra-pure filtration in the field of printing ink and the semiconductor industry.

The degree of thickness of the fiber cross section can be regarded as the diameter of the fibers thereof, the average diameter of the coarse fibers in the coarse fiber layer being the average value of the diameters of the coarse fibers in the coarse fiber layer, and the average diameter of the fine fibers in the fine fiber layer being the average value of the diameters of the fine fibers in the fine fiber layer; the average diameter of the fiber in the invention can be calculated by using a scanning electron microscope to characterize the morphology of the filter membrane structure and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring the average diameter; it will of course be appreciated that the person skilled in the art can also obtain the above parameters by other measuring means; the average pore size may be measured by a PMI pore size distribution instrument, or by the bubble point method, mercury intrusion method, or other measurement methods.

As a further improvement of the invention, the average diameter of the coarse fibers in the coarse fiber layer is at least 300nm greater than the average diameter of the fine fibers in the fine fiber layer. Preferably, the average diameter of the coarse fibers in the coarse fiber layer is at least 350nm greater than the average diameter of the fine fibers in the fine fiber layer.

The thickness of the fiber in the filter membrane main body can greatly influence the mechanical strength of the filter membrane, and under certain conditions, the coarser the fiber is, the larger the mechanical strength of the filter membrane is; the average diameter of the coarse fibers in the coarse fiber layer is at least 300nm larger than that of the fine fibers in the fine fiber layer, so that the coarse fibers in the coarse fiber layer have larger diameters, a supporting effect can be provided for the whole filter membrane, the filter membrane has larger mechanical strength, and the application range of the filter membrane is further enlarged.

As a further improvement of the invention, the interception efficiency of the filter membrane to particles with the particle diameter of more than 70nm is more than 99%; the time required for 50ml of water to pass through a filter membrane with a diameter of 47mm is 25-300s under the conditions that the pressure is-0.03 MPa and the temperature is 20 ℃.

Through the interception efficiency test of the filter membrane, the filter membrane has high interception efficiency, the interception efficiency of particles with the particle diameter of more than 70nm is more than 99%, the filter membrane can fully intercept undesired substances, the filter precision is high, and the filter quality is ensured. Through the flow rate test of the filter membrane, the filter membrane has higher flow rate, short filtering time, lower time cost and larger economic benefit.

As a further improvement of the invention, the tensile strength of the filter membrane is 3-10MPa; the elongation at break is 30-60%.

Important indexes for evaluating the mechanical strength of the filter membrane are the tensile strength and the elongation at break of the filter membrane; under certain conditions, the greater the tensile strength of the filter membrane, the better the mechanical strength of the filter membrane is; tensile strength refers to the ability of a film to withstand parallel stretching; when the film sample is tested under certain conditions, the tensile load is acted until the film sample is broken, and the tensile strength and the elongation at break of the film can be calculated according to the maximum tensile load corresponding to the breaking of the film sample, the change of the size (length) of the film sample and the like; tensile strength, elongation at break, all of which can be measured by a universal tensile tester, methods of testing tensile strength are well known in the art, for example, the procedure for tensile strength testing is explained in detail in ASTM D790 or ISO 178; the tensile strength of the filter membrane is 3-10MPa; the elongation at break is 30-60%, which indicates that the filter membrane has larger tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand.

As a further improvement of the present invention, the average pore diameter of the coarse fiber layer in the region near the first porous surface is larger than the average pore diameter of the region near the second porous surface, and the average diameter of the coarse fiber in the coarse fiber layer in the region near the first porous surface is larger than the average diameter of the coarse fiber in the region near the second porous surface; and/or the average pore diameter of the area close to the second porous surface in the fine fiber layer is smaller than the average pore diameter of the area close to the first porous surface, and the average diameter of the fine fiber of the area close to the second porous surface in the fine fiber layer is smaller than the average diameter of the fine fiber of the area close to the first porous surface.

The pore diameter of the filter membrane in the thickness direction is asymmetric, wherein the first porous surface is a liquid inlet surface, the second porous surface is a liquid outlet surface, and when the filter membrane is used for filtering, fluid passes through the coarse fiber layer and then passes through the fine fiber layer; because the average pore diameter of the coarse fiber layer is larger, and the average pore diameter of the fine fiber layer is smaller, large particle impurities in the fluid can be trapped in the coarse fiber layer, small particle matters can be trapped in the fine fiber layer, and impurity particles with different particle diameters can be trapped in different areas, so that the filter membrane can effectively filter the fluid, the trapping rate of the impurity particles is high, and the filtering efficiency of the filter membrane is guaranteed.

As a further improvement of the invention, the thickness of the filter membrane is 50-110 mu m, the porosity is 45-80%, and the average pore diameter is 100-800nm.

The thickness of the filter membrane can be calculated and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually after the morphology of the membrane structure is characterized by using a scanning electron microscope; the porosity of the filter membrane refers to the proportion of the volume of membrane pores of the filter membrane to the total volume, and the membrane pores comprise open pores and closed pores; common porosity testing methods include mercury intrusion, density and dry-wet film weighing; the average pore diameter of the filter membrane can be measured by a PMI pore diameter distribution instrument, and also can be measured by a bubble point method, a mercury intrusion method or other measuring methods; of course, the person skilled in the art can also obtain the above parameters by other measuring means, which are only used as reference. When the thickness of the filter membrane is too small, the mechanical strength of the filter membrane is low; meanwhile, as the filtering time is too short, effective filtering cannot be performed; when the thickness of the filter membrane is too large, the filtering time is too long, the time cost is too large, and the economic benefit is low. The thickness of the filter membrane is 50-110 mu m, so that the filter membrane has higher mechanical strength, can effectively filter and has higher filtering efficiency; the filtering time is also shorter and the time cost is lower.

Under certain conditions, the larger the porosity of the filter membrane is, the larger the sewage containing amount is; the porosity of the filter membrane is 50-80%, which indicates that the filter membrane has higher sewage containing amount, can entrap more impurity particles, and has longer service life. The average pore diameter is an important performance of the filter membrane, and the average pore diameter of the filter membrane is 100-800nm, so that the filter membrane has proper filtration precision and larger water flux.

As a further improvement of the invention, the porosity of the coarse fiber layer is 50-85% and the porosity of the fine fiber layer is 25-65%.

Under certain conditions, the larger the porosity of the filter membrane is, the larger the sewage containing amount is; the coarse fiber layer has larger porosity, so that the coarse fiber layer has larger pollution receiving amount, can store more impurity particles, and prolongs the service life of the filter membrane; the porosity of the fine fiber layer is smaller, but the fine fiber layer mainly entraps particle impurities with small particle size, so that the fine fiber layer can still store more tiny impurity particles, and the service life of the filter membrane is not influenced; thereby ensuring that the filter membrane has longer service life and high cost performance.

As a further improvement of the invention, the fine fiber layer has a thickness of 10-25 μm and the coarse fiber layer has a thickness at least 30 μm greater than the fine fiber layer thickness.

In the main structure of the filter membrane, the thickness of the coarse fiber layer is far greater than that of the fine fiber layer; the thickness of the crude fiber layer is larger, the aperture is larger, most particulate impurities can be trapped when the fluid passes through the crude fiber layer, the flow speed is high, the filtering time is short, and only few tiny impurity particles are left; when the fluid passes through the fine fiber layer, tiny impurity particles can be trapped, so that the filter membrane is ensured to have higher trapping rate and high filtering precision; the thickness of the fine fiber layer is 10-25 mu m, and under the thickness, on one hand, the fine fiber layer can be ensured to sufficiently filter fluid and effectively intercept fine particle impurities; on the other hand, the thickness of the fine fiber layer is smaller, and the filtering time is still shorter although the flow velocity of the fluid in the fine fiber layer is not large; finally, the time for the fluid to pass through the whole filter membrane is also ensured to be shorter, and the time cost is lower; the filter membrane has higher filtering precision, higher filtering rate and shorter filtering time.

As a further improvement of the present invention, the average pore diameter of the first porous surface is 1000 to 6000nm, and the average pore diameter of the second porous surface is 15 to 65nm.

As a further improvement of the present invention, the first porous surface comprises first pores having a pore diameter of 0.4 to 14 μm and a pore density of 15 to 45 pores/1000 μm ²; the second porous surface comprises second holes with the pore diameter of 10-110nm and the pore density of 25-130/10 ⁶nm².

As a further improvement of the present invention, the first porous surface has a pore area ratio of 10 to 30%; the second porous surface has a pore area ratio of 3-14%.

The method for measuring the pore diameter of the membrane surface can be used for carrying out morphology characterization on the membrane structure by using a scanning electron microscope, then carrying out measurement by using computer software (such as Matlab, NIS-Elements and the like) or manually, and carrying out corresponding calculation so as to obtain corresponding data; in the preparation of the membrane, the performance characteristics such as pore size distribution are substantially uniform and substantially uniform in the direction perpendicular to the membrane thickness (the direction is a planar direction if the membrane is in the form of a flat plate membrane and the direction is perpendicular to the radial direction if the membrane is in the form of a hollow fiber membrane), so that the pore size and distribution of the entire surface on the plane can be reflected by the pore size and distribution of a part of the area on the plane. When the membrane of the present invention is in the form of a flat plate membrane, the pore size and distribution thereof are substantially uniform on the surface of the filter membrane of the present invention; therefore, when actually measuring, the surface of the membrane can be firstly characterized by an electron microscope to obtain a corresponding SEM image, then a certain area, such as 1000 μm ² (40 μm multiplied by 25 μm) or 10000 μm ² (100 μm multiplied by 100 μm), is selected, the specific area size is determined according to the actual situation, the aperture of the holes on the area is measured by corresponding computer software or manually, and then calculation is performed, and corresponding data such as hole density, hole area rate and the like are obtained; of course, the person skilled in the art can also obtain the above parameters by other measuring means, which are only used as reference.

The aperture of the first holes on the first porous surface is relatively larger, and the area ratio of the holes is also larger, so that the filter membrane has larger flow velocity and flux, the fluid can conveniently and rapidly pass through the polymer filter membrane, and the filtering time is shortened; simultaneously, the sewage receiving amount of the filter membrane is increased; the aperture of the second hole on the second porous surface is smaller and is in the nanometer level, so that the filtering precision of the filter membrane is ensured, and the filter membrane has enough interception function on undesired substances; the filter membrane is particularly suitable for ultra-pure filtration in the field of printing ink and the semiconductor industry.

As a further development of the invention, the body further comprises a transition layer between the coarse and fine fiber layers, the fibers in the transition layer having an average diameter of 100-300nm and a porosity of 30-75%.

The main structure of the filter membrane also comprises a transition layer, wherein the transition layer is positioned between the coarse fiber layer and the fine fiber layer; the transition layer contains fibers with various thicknesses; wherein a portion of the fibers have a larger diameter and are substantially the same as the diameter of the coarse fibers in the coarse fiber layer; the fiber diameter of a part of the fibers is smaller and is basically the same as that of the fine fibers in the fine fiber layer; the fiber diameter of a part of fibers is positioned between the two diameters, so that the transition layer is a transition area between the coarse fiber layer and the fine fiber layer, and the fiber diameter and the porosity are changed to a certain extent; the average diameter of the fibers in the transition layer is smaller than the average diameter of the coarse fibers in the coarse fiber layer and larger than the average diameter of the fine fibers in the fine fiber layer; the porosity of the transition layer is smaller than that of the coarse fiber layer and larger than that of the fine fiber layer; it also illustrates that the process from coarse fiber layer to fine fiber layer is not a sudden change process, but a gradual change process; the existence of the filter layer further improves the combination degree between the coarse fiber layer and the fine fiber layer, so that the combination is tighter; even when the fluid is impacted by high pressure, the coarse fiber layer and the fine fiber layer are not separated, so that the excellent filtering effect of the filter membrane is ensured, and the application range of the filter membrane is enlarged.

As a further improvement of the invention, the number of coarse fibers with the diameter of 300-1500nm in the transition layer accounts for 10-30% of the total number of fibers, and the number of fine fibers with the diameter of 25-95nm accounts for 5-30% of the total number of fibers.

The transition layer contains fibers with various diameters, which further explains that the transition layer is a transition region between the coarse fiber layer and the fine fiber layer, thereby being beneficial to improving the peeling strength between the coarse fiber layer and the fine fiber layer and ensuring tighter combination; at the same time, the method is favorable for further improving the tensile strength of the filter membrane, and the longitudinal tensile strength and the transverse tensile strength are both improved to a certain extent

As a further improvement of the invention, the average pore diameter of the transition layer is 200-350nm; the thickness of the transition layer is 10-40% of the thickness of the fine fiber layer.

The average pore diameter of the transition layer is 200-350nm (0.2-0.35 μm), the average pore diameter is smaller than the average pore diameter of the coarse fiber layer and larger than the average pore diameter of the fine fiber layer, and the transition region between the coarse fiber layer and the fine fiber layer can be seen through the average pore diameter; the thickness of the fine fiber layer is small, and the thickness of the filter layer is only 10-40% of the thickness of the fine fiber layer, which indicates that the thickness of the transition layer is smaller, the peeling strength between the coarse fiber layer and the fine fiber layer is improved, the interception efficiency and the filtration speed of the filter membrane are not influenced, and the filtration quality is ensured.

As a further improvement of the invention, the IPA bubble point pressure of the filter membrane is 200-300KPa; the pure water flux of the filter membrane is 30-100ml/cm ².min under the conditions of 0.1MPa and 25 ℃.

The bubble point is an important performance characteristic of the filter membrane, and the application range of the filter membrane is greatly influenced by the bubble point; bubble point testing methods are well known in the art, and the procedures for these tests are explained in detail, for example, in ASTM F316-70 and ANS/ASTM F316-70 (re-approval 1976), which are incorporated herein by reference. The test liquid used in the invention is IPA (isopropyl alcohol); the IPA bubble point bubble pressure of the filter membrane is 200-300KPa; the bubble point is very large, which also proves that the filter membrane has larger application; the ultra-pure filter is particularly suitable for being applied to the ultra-pure filtration in the fields of printing ink and semiconductors; flux is also an important performance characteristic of a filter membrane, and is the amount of substance passing through a unit membrane area in a unit time under a certain working pressure in the membrane separation process; when the raw material liquid is pure water, the flux is pure water flux; under certain conditions, the larger the flux, i.e. the larger the volume of fluid which can be filtered by the membrane in unit area in unit time; the flux of the filter membrane is 30-100ml/cm ² min, and the flux is larger; in unit time, the volume of fluid which can be filtered by the membrane in unit area is also larger, namely the filtering speed is high, and the economic benefit generated by the filter membrane is higher.

On the other hand, the invention also provides a preparation method of the polymer filter membrane mixed by coarse and fine fibers, which comprises the following steps:

S1: preparing a casting solution with the viscosity of 3000-8000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 6-15 parts of sulfone polymer, 60-85 parts of polar solvent and 5-20 parts of hydrophilic additive; the sulfone polymer is any one of polyether sulfone, bisphenol A polysulfone and polyarylsulfone; the polar solvent is at least one of butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethyl pyrrolidone, dimethylacetamide and N-methyl pyrrolidone;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 10g H ₂O/kg～30g H₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 35-50 ℃ to ensure that the relative speed between the air flow and the liquid film is not more than 3m/min and the duration is not more than 60s, so as to form a semi-finished film;

s3: the semi-finished film is then cured by immersing it in water at a temperature of 0-10 ℃ for a duration of at least 25s, and then cured to form a solid film.

As a further improvement of the invention, after the semi-finished film is formed in S2, the semi-finished film is immersed into water with the temperature of 15-30 ℃ for partial curing, and the curing time is 5-15S; immersing in water at 0-10deg.C for at least 25 seconds to cure and form solid film.

In the method, firstly, preparing a casting solution, wherein the casting solution comprises the following substances in parts by weight: 6-15 parts of organic polymer; 60-85 parts of polar solvent and 5-20 parts of hydrophilic additive; wherein the organic polymer is any one of polyethersulfone, bisphenol A polysulfone and polyarylsulfone, and the finally prepared filter membrane is a sulfone polymer filter membrane which has excellent oxidation resistance, thermal stability, high-temperature melting stability and good mechanical property; the viscosity of the prepared casting solution is 3000-8000 mPa.s, and the viscosity of the casting solution can have a great influence on the structure and performance of the finally formed filter membrane, such as the aperture, thickness, flow rate and the like of the filter membrane; such a viscosity setting ensures that the final filter membrane has a suitable thickness and that the desired pore size is obtained; the viscosity of the casting solution can be directly obtained by a viscometer; casting the casting film on a carrier to form a liquid film; the casting solution of the present invention may be cast manually (e.g., by pouring by hand, casting, or spreading over a casting surface) or automatically (e.g., pouring or otherwise casting over a moving bed); a variety of apparatuses known in the art may be used for casting. Casting equipment includes, for example, mechanical applicators, including knives, doctor blades, or spray/plenum systems. A variety of casting speeds are known in the art as suitable, such as casting speeds of about 2-6 feet per minute (fpm), and the like.

Then placing the liquid film in an environment with the temperature of 35-50 ℃ (higher temperature), blowing air flow with the absolute humidity of 10g H ₂O/kg～30g H₂ O/kg onto the surface of the liquid film for treatment, and inducing the liquid film to split phases; but the relative speed between the air flow and the liquid film is not more than 3m/min, preferably not more than 2m/min, and the duration is not more than 60s; when blowing, the wind direction can be opposite to the direction of the carrier driving the liquid film to move, or can be the same or form a certain included angle, and of course, the carrier driving the liquid film to move to form relative air flow without blowing; the relative speed between the air flow and the liquid film can have a certain influence on the aperture of the finally formed filter film, and particularly has a larger influence on the aperture of the region, close to the air flow, in the filter film; under certain conditions, the larger the relative speed between the air flow and the surface of the liquid film is, the larger the aperture of the finally formed filter film is; the area of the filter membrane towards one side of the air flow finally forms a fine fiber layer of the liquid film, and the aperture of the area is very small and is nano-scale; thus requiring a relatively low velocity between the gas stream and the liquid film; the relative speed between the air flow and the liquid film is not more than 3m/min, so that the pore diameter of the finally formed filter membrane fine fiber layer is ensured to be nanoscale pore diameter, good interception effect can be achieved on impurity particles with the particle diameter of 0.8-200nm, and particularly, the high-efficiency interception effect can be achieved on the impurity particles with the particle diameter of 20-200 nm; but also quickens the phase separation action of the liquid film surface, shortens the phase separation time and is beneficial to forming a fine fiber layer by phase separation of the liquid film surface.

Then the semi-finished film is put into water with the temperature of 15-30 ℃ for partial curing, the curing time is 5-15s, the previous phase separation temperature is 35-50 ℃, the current environment temperature is 15-30 ℃, and the environment temperature is changed to a certain extent, so that the curing of the semi-finished film is facilitated; however, as the ambient temperature is not changed greatly and the duration is only 5-15s, the semi-finished film is partially solidified, so that a transition layer with small thickness is formed; then immersing the semi-finished product in water with the temperature of 0-10 ℃ for further curing, wherein the duration is at least 25s; the current environment temperature is 0-10 ℃, and the initial phase separation temperature (35-50 ℃) is greatly changed, so that a coarse fiber layer with a great difference from the previous fine fiber layer structure is formed; the final filter membrane comprises three areas of a coarse fiber layer, a transition layer and a fine fiber layer, wherein the transition layer is positioned between the coarse fiber layer and the fine fiber layer, and the transition layer improves the bonding degree between the coarse fiber layer and the fine fiber layer; if the semi-finished membrane is not put into water with the temperature of 15-30 ℃ for preliminary solidification, the main structure of the final filter membrane does not have a transitional layer area, so that the combination degree between the coarse fiber layer and the fine fiber layer is influenced, separation is easy to occur, the impact of high-pressure fluid cannot be resisted, and the tensile strength of the filter membrane is reduced; after curing, the film is dried in air to form a solid film, i.e., a desired polymer filter film. The air-drying may be natural air-drying or may be performed by a machine such as an electric fan. The preparation method is simple, quick, effective, low in cost, environment-friendly and suitable for industrial application.

As a further improvement of the invention, the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2.

In order to improve the structural morphology and performance of the filter membrane, the invention adds an additive in the formula, wherein the additive selects the mixture of diglyme, tertiary butyl alcohol lithium and polyvinylpyrrolidone, the polyvinylpyrrolidone is a small molecular additive, and the addition of the polyvinylpyrrolidone can adjust the viscosity of the system on one hand, thereby adjusting the thickness and pore size of the filter membrane; the addition of two small molecular substances, namely diglyme and lithium tert-butoxide, is beneficial to improving the film forming speed of the filter film on one hand and the mechanical strength of the filter film on the other hand; in addition, under the synergistic effect of the three substances, the hydrophilicity of the polar solvent can be improved, and the polar solvent is more easily dissolved by water during phase separation, so that the organic polymer is more easily separated out, the phase separation speed is increased, and the phase separation time is shortened; in addition, the pore size and distribution can be regulated to obtain an ideal membrane main body structure.

On the other hand, the invention also provides application of the polymer filter membrane mixed by coarse and fine fibers, wherein the filter membrane is used in the field of printing ink; the ultra-pure filter is used for ultra-pure filtration in the semiconductor industry.

The ink is mixed with impurities such as crust, grinding media (glass beads) and the like after being prepared, so that the ink must be filtered before a final finished product is obtained; the filter membrane can well filter out the impurity particles, and effectively control the particle size of the ink, so that the ink with high quality is obtained; ultrapure water is also called UP water, which has little impurities, bacteria, chlorine-containing dioxin and other substances except water molecules, and naturally has no mineral trace elements required by human bodies, namely water which almost removes all atoms except oxygen and hydrogen. Ultrapure water is mainly used for developing water produced by distillation, deionization, reverse osmosis technology or other appropriate supercritical fine technology of semiconductor original materials; therefore, the filter membrane can remove more particle impurities, which is an essential link for preparing ultrapure water during filtration, and is beneficial to finally obtaining high-quality ultrapure water.

The invention has the beneficial effects that: the polymer filter membrane comprises a coarse fiber layer and a fine fiber layer; the average diameter of the coarse fibers in the coarse fiber layer is 350-800nm, and the average pore diameter is 400-1500nm; the average diameter of the fine fibers in the fine fiber layer is 20-75nm, and the average pore diameter is 40-140nm. The nanometer holes of the fine fiber layer also have stronger adsorption effect, so that the interception effect of the filter membrane is further improved; the filter membrane has the advantages of larger flow rate, shorter filtering time, higher filtering precision, strong interception function on impurity particles with the particle size of 0.8-200nm, larger tensile strength and elongation at break, wide application range and particular suitability for ultra-pure water filtration in the ink field and the semiconductor field; in addition, the invention also provides a preparation method of the filter membrane, which is quick and effective, simple to operate, green and environment-friendly and suitable for large-scale popularization.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a nano-sized polymer filter membrane prepared according to example 2, wherein the magnification is 500;

FIG. 2 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a nano-sized polymer filter membrane prepared according to example 2, in which the magnification is 20000×

FIG. 3 is a Scanning Electron Microscope (SEM) image of a first porous surface of a nano-sized polymer filtration membrane prepared according to example 2, wherein the magnification is 2000;

FIG. 4 is a Scanning Electron Microscope (SEM) image of the second porous surface of the nano-sized polymer filter membrane prepared according to example 2, wherein the magnification is 100000;

FIG. 5 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a nano-sized polymer filter membrane prepared according to example 9, wherein the magnification is 50000;

FIG. 6 is a schematic diagram of an IPA bubble point test apparatus for a nano-scale polymer filtration membrane of the present invention;

FIG. 7 is a schematic diagram of a flow rate testing device for a nano-scale polymer filtration membrane according to the present invention;

FIG. 8 is a schematic diagram of a device for testing the filtration accuracy of a nano-scale polymer filtration membrane according to the present invention;

FIG. 9 is a schematic view showing the structure of the nano-sized polymer filtration membrane of the present invention when used in the ink field, and the ultra-pure water filtration in the semiconductor field;

FIG. 10 is a schematic view showing another structure of the nano-sized polymer filtration membrane of the present invention when it is used for filtration of ultrapure water in the ink field and the semiconductor field.

Detailed Description

In order to more clearly illustrate the general concept of the present application, the following detailed description is given by way of example. Example 1 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 6000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 11 parts of sulfone polymer, 72 parts of polar solvent and 13 parts of hydrophilic additive; the sulfone polymer is polyethersulfone; the polar solvent is dimethylformamide; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 20g H ₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 43 ℃ at the relative speed of 1.5m/min for 35s to form a semi-finished film;

s3: immersing the semi-finished film into water with the temperature of 23 ℃ for partial curing for 10 seconds; then the mixture is immersed in water with the temperature of 5 ℃ for curing again for 50 seconds, and then the solid film is formed by curing.

Example 2 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 8000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 15 parts of sulfone polymer, 80 parts of polar solvent and 18 parts of hydrophilic additive; the sulfone polymer is polyethersulfone; the polar solvent is N-methyl pyrrolidone; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2; s2: inducing the liquid film to perform pre-phase separation, blowing air flow with absolute humidity of 30g H ₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 48 ℃ and the relative speed between the air flow and the liquid film is 3m/min for 20s, so as to form a semi-finished film;

S3: immersing the semi-finished film into water with the temperature of 28 ℃ for partial curing, wherein the curing time is 8s; then the mixture was immersed in water at 8 ℃ for curing again for 65 seconds, and then cured to form a solid film.

Example 3 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 3000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 6 parts of sulfone polymer, 70 parts of polar solvent and 8 parts of hydrophilic additive; the sulfone polymer is polyethersulfone; the polar solvent is ethyl acetate; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 10g H ₂ O/kg to the surface of the liquid film for treatment in an environment with temperature of 36 ℃ at a relative speed of 0.5m/min for 55s to form a semi-finished film;

S3: immersing the semi-finished film into water with the temperature of 26 ℃ for partial curing, wherein the curing time is 14s; then the mixture was immersed in water at 2 ℃ for curing again for 40 seconds, and then cured to form a solid film.

Example 4 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 6000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 11 parts of sulfone polymer, 72 parts of polar solvent and 13 parts of hydrophilic additive; the sulfone polymer is bisphenol A type polysulfone; the polar solvent is butyl lactate; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 20g H ₂ O/kg to the surface of the liquid film for treatment in an environment with temperature of 42 ℃ to form a semi-finished film, wherein the relative speed between the air flow and the liquid film is not more than 1m/min and the duration time is 50 s;

S3: immersing the semi-finished film into water with the temperature of 22 ℃ for partial curing, wherein the curing time is 10s; then the mixture is immersed into water with the temperature of 5 ℃ for curing again for 55 seconds, and then the solid film is formed by curing.

Example 5 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

s1: preparing a casting solution with the viscosity of 7500 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 14 parts of sulfone polymer, 75 parts of polar solvent and 15 parts of hydrophilic additive; the sulfone polymer is bisphenol A type polysulfone; the polar solvent is methyl acetate; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with the absolute humidity of 28g H ₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 48 ℃ to ensure that the relative speed between the air flow and the liquid film is not more than 2.8m/min and the duration time is 30s, so as to form a semi-finished film;

s3: immersing the semi-finished film into water with the temperature of 27 ℃ for partial curing, wherein the curing time is 14s; then the mixture was immersed in water at a temperature of 10 ℃ for curing again for 70 seconds, and then cured to form a solid film.

Example 6 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps: s1: preparing a casting film solution with the viscosity of 3500 mPas, and casting the casting film solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 7 parts of sulfone polymer, 70 parts of polar solvent and 7 parts of hydrophilic additive; the sulfone polymer is bisphenol A type polysulfone; the polar solvent is a mixture of caprolactam and ethyl acetate, and the mass ratio of the polar solvent to the ethyl acetate is 1:1; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2; s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 12g H ₂ O/kg to the surface of the liquid film for treatment in an environment with the temperature of 35 ℃ at the relative speed of 0.2m/min for 60s to form a semi-finished film;

S3: immersing the semi-finished film into water with the temperature of 16 ℃ for partial curing, wherein the curing time is 8s; then immersing in water with the temperature of 0 ℃ for curing again for at least 30 seconds, and further curing to form a solid film.

Example 7 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps: s1: preparing a casting solution with the viscosity of 6000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 11 parts of sulfone polymer, 70 parts of polar solvent and 13 parts of hydrophilic additive; the sulfone polymer is polyarylsulfone; the polar solvent is dimethylformamide; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2; s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 20g H ₂ O/kg to the surface of the liquid film for treatment in an environment with temperature of 40 ℃ at a relative speed of 2m/min for 47s to form a semi-finished film;

s3: immersing the semi-finished film into water with the temperature of 22 ℃ for partial curing, wherein the curing time is 10s; then the mixture is immersed in water with the temperature of 5 ℃ for curing again for 50 seconds, and then the solid film is formed by curing.

Example 8 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 7000 Pa.s, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 13 parts of sulfone polymer, 80 parts of polar solvent and 18 parts of hydrophilic additive; the sulfone polymer is polyarylsulfone; the polar solvent is N-ethyl pyrrolidone; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with the absolute humidity of 28g H ₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 46 ℃ at the relative speed of 2.8m/min for 30s to form a semi-finished film;

S3: immersing the semi-finished film into water with the temperature of 20 ℃ for partial curing for 12 seconds; then the mixture is immersed into water with the temperature of 8 ℃ for curing again for 60 seconds, and then the solid film is formed by curing.

Example 9 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting film solution with the viscosity of 3500 mPas, and casting the casting film solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 6 parts of sulfone polymer, 60 parts of polar solvent and 10 parts of hydrophilic additive; the sulfone polymer is polyarylsulfone; the polar solvent is a mixture of dimethylformamide and N-methylpyrrolidone, and the mass ratio of the polar solvent to the N-methylpyrrolidone is 2:1; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 11g H ₂ O/kg to the surface of the liquid film for treatment in an environment with the temperature of 35 ℃ at the relative speed of 0.5m/min for 55s to form a semi-finished film;

s3: immersing the semi-finished film into water with the temperature of 16 ℃ for partial curing, wherein the curing time is 6s; then the mixture is immersed into water with the temperature of 1 ℃ to be cured again for 40 seconds, and then the solid film is formed by curing.

Example 10 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 5000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 10 parts of sulfone polymer, 75 parts of polar solvent and 10 parts of hydrophilic additive; the sulfone polymer is polyethersulfone; the polar solvent is N-ethyl pyrrolidone; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2; s2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 20g H ₂ O/kg to the surface of the liquid film for treatment in an environment with temperature of 40 ℃ to form a semi-finished film, wherein the relative speed between the air flow and the liquid film is not more than 1.8m/min, and the duration time is 45 s;

S3: the semi-finished film was immersed in water at 5 ℃ for curing for 60 seconds, and then cured to form a solid film.

Example 11 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

s1: preparing a casting solution with the viscosity of 5500 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 12 parts of sulfone polymer, 65 parts of polar solvent and 17 parts of hydrophilic additive; the sulfone polymer is bisphenol A type polysulfone; the polar solvent is butyl lactate; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2.

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 18g H ₂ O/kg to the surface of the liquid film for treatment in an environment with the temperature of 40 ℃ at the relative speed of 2.3m/min for 45s to form a semi-finished film;

Example 12 provides a polymer filter membrane blended with coarse and fine fibers, prepared by the following method: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 4500 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 8 parts of sulfone polymer, 80 parts of polar solvent and 10 parts of hydrophilic additive; the sulfone polymer is polyarylsulfone; the polar solvent is N-methyl pyrrolidone; the additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 17g H ₂ O/kg to the surface of the liquid film for treatment in an environment with the temperature of 37 ℃ to form a semi-finished film, wherein the relative speed between the air flow and the liquid film is not more than 0.5m/min, and the duration time is 57 s;

And (3) a step of: the structure characterization, namely performing morphology characterization on the membrane main structure of the polymer filter membrane obtained in each embodiment by using a scanning electron microscope, and then obtaining required data; the specific results are shown in the following table: thickness unit: μm;

	Thickness of filter membrane	Thickness of coarse fiber layer	Thickness of fine fiber layer	Thickness of transition layer
					Example 1	81.2	60.1	18.3	2.8
Example 2	102.1	75.0	22.5	4.6
					Example 3	54.5	40.7	12.1	1.7
Example 4	75.6	56.3	16.7	2.6
					Example 5	98.4	71.1	23.1	4.2
Example 6	52.7	39.6	11.6	1.5
					Example 7	86.3	66.0	17.5	2.8
Example 8	107.2	78.5	23.9	4.8
					Example 9	55.8	42.3	11.7	1.8
Example 10	76.3	59.8	16.5	\
					Example 11	78.3	61.0	17.3	\
Example 12	72.3	56.9	15.4	\

As can be seen from the table, the thickness of the fine fiber layer is smaller, so that the whole filter membrane has shorter filtering time and can effectively filter; the thickness of the coarse fiber layer is at least 30 mu m larger than that of the fine fiber layer, so that the whole filter membrane has larger mechanical strength; the thickness of the transition layer is only 10% -40% of the thickness of the fine fiber layer, and the thickness is small, so that the fine fiber layer and the coarse fiber layer are more tightly combined, and the filtering efficiency is not influenced.

Average pore size unit: nm (nm)

As can be seen from the table, the coarse fiber layer has larger average pore diameter and large flow velocity, and is suitable for intercepting impurity particles with larger particle size; the fine fiber layer has small impurity particles and is suitable for intercepting the impurity particles with smaller particle size; thereby ensuring that the whole filter membrane has larger flow velocity and larger interception efficiency for impurity particles.

Porosity unit: %

	Filter membrane	Coarse fiber layer	Fine fiber layer	Transition layer
					Example 1	68.1	72.7	56.4	67.3
Example 2	75.6	80.5	60.3	73.7
					Example 3	70.2	74.2	57.6	68.5
Example 4	67.1	71.6	52.9	63.4
					Example 5	69.5	76.3	57.1	65.7
Example 6	62.4	68.5	48.6	56.2
					Example 7	53.2	58.7	34.8	50.4
Example 8	59,3	63.5	40.2	57.3
					Example 9	51.7	56.1	30.2	48.9
Example 10	62.5	69.6	50.3	\
					Example 11	58.1	64.7	48.1	\
Example 12	50.3	57.3	28.9	\

As shown in the table above, the crude fiber layer has larger porosity, thereby having larger sewage receiving amount and ensuring the longer service life of the filter membrane.

Average fiber diameter unit: nm (nm)

The average pore size of the first porous surface refers to the average of the pore diameters on the first porous surface; the average pore size of the second porous surface refers to the average of the pore diameters on the second porous surface; average pore size unit: nm; the pore density on the first porous surface means the pore density of the first pores having a pore diameter of 0.4 to 14 μm on the first porous surface, in units of: individual/1000 μm ²; the pore density on the second porous surface means the pore density of the second pores having a pore diameter of 10 to 110nm on the second porous surface, in units of: personal/10 ⁶nm²;

Hole area ratio unit: the%;

As can be seen from the table, the average pore diameter of the first porous surface is larger, the pores are mostly micron-sized pores, and under certain conditions, the larger the average pore diameter of the filter membrane is, the larger the flow velocity is, so that the filter membrane has a larger flow velocity; the average pore diameters of the second porous surfaces are very small and are all nanoscale pores, so that the second porous surfaces can effectively intercept nanoscale impurity particles, and the filtering accuracy of the filter membrane is very high; meanwhile, the nano-scale holes have strong adsorption effect, and further can filter the filter precision of the filter membrane, so that the filter membrane can effectively intercept impurity particles with the particle size of 0.8-200 nm.

IPA bubble point test (test apparatus as in fig. 6), experimental procedure: step one: closing the air pressure regulator 2, opening the air pressure regulator 1 to enable the pressure to be higher than the tested pressure, taking out the wetted filter membrane to be tested, and installing the filter membrane on a filter device. Step two: the reservoir was filled with 80% of the test liquid (IPA), the air pressure was increased, and the pressurization was stopped when the air pressure reached about 80% of the bubble point. It is necessary to confirm that the filter membrane in the reservoir has not been bubbled at this time. Step three: slowly boosting, and reading the pressure at the moment when the filter membrane starts to foam, wherein the pressure is used as the IPA bubble point foam pressure; note that: typically the bubbles emerge from near the center of the filter.

Water flow rate test (test device as in fig. 7) experimental procedure: step one: the filter membrane to be tested is arranged on a support for decompression filtration, a valve 2 on the decompression filtration support is closed, a valve 1 is opened, a vacuum pump is started, and after the pressure is regulated to be-0.03 MPa, the valve 1 is closed. Step two: filling 50ml of test liquid (water) into a plastic measuring cylinder of a support for decompression filtration, opening a valve 2, starting timing from one scale to the other scale, and stopping timing; step three: after the test is completed, the value displayed by the stopwatch is recorded, when all the test liquid passes through the filter membrane, the valve 2 on the bracket is closed, and the filter membrane is taken out. And (3) injection: the test temperature is 20 ℃, and the diameter of the filter membrane to be tested is 47mm. The tensile strength and elongation at break were measured by a universal tensile tester (specimen width: 10mm; specimen gauge: 50 mm;)

As shown in the table above, the nano-scale polymer filter membrane of the invention not only has a very high IPA bubble point, but also has a large flow rate and flux, and the filter time is short, thus being particularly suitable for the ink field and the semiconductor field.

And (3) testing the filtering precision: the filtration membranes obtained in each example were tested for interception efficiency.

Experiment preparation: the experimental apparatus was assembled as shown in fig. 8, ensuring the apparatus was clean, and rinsed with ultrapure water. A filter membrane with the diameter of 47mm is taken and is arranged in the butterfly filter, so that the air tightness of the assembled filter is ensured to be good. The experimental steps are as follows: the challenge fluid was poured into a tank, the butterfly filter was carefully vented, pressurized to 10kPa, and the butterfly downstream filtrate was taken using a clean bottle. The number of particles in the filtrate and stock solutions was measured with a particle counter. Interception efficiency: formula (i): η -interception efficiency,%; n ₀ -number of particles in stock solution, average of 5 counts, one; n 1-number of particles in filtrate, average of 5 counts.

As is clear from the above table, the filtration membrane of the present invention has a retention efficiency of more than 99% for impurity particles with a particle size of 70nm or more, and has high filtration precision and filtration efficiency

When the filter membrane is applied to the field of ink, larger particles in the ink can be filtered, the particle size of the ink can be effectively controlled, the ink can meet the requirement of on-machine spray printing, and the ink can be smoothly sprayed out of a nozzle without blocking a spray head. When the filter membrane is applied to ultra-pure filtration in the semiconductor industry, not only large particle impurities in water but also substances such as viruses, bacteria and algae in the water can be removed, and macromolecules and colloid in the water can be removed, so that the ultra-pure water with high quality can be finally obtained. As can be seen from fig. 9 and 10, the filter membrane of the present invention can be formed into a folded membrane shape or a wound shape for ultra-pure filtration in the ink field and the semiconductor industry.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.

Claims

1. The utility model provides a polymer filter membrane that thick and thin fibre was thoughtlessly taken, includes the main part, have non-directional tortuous passageway in the main part, its characterized in that: the body comprises a coarse fiber layer and a fine fiber layer;

A side surface area of the coarse fiber layer forms a first porous surface, and a side surface area of the fine fiber layer facing away from the first porous surface forms a second porous surface;

The average diameter of the crude fibers in the crude fiber layer is 350-800nm, and the average pore diameter is 400-1500nm;

the average diameter of the fine fibers in the fine fiber layer is 20-75nm, and the average pore diameter is 40-140nm;

The body further comprises a transition layer between the coarse and fine fiber layers, the fibers in the transition layer having an average diameter of 100-300nm.

2. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the average diameter of the coarse fibers in the coarse fiber layer is at least 300nm greater than the average diameter of the fine fibers in the fine fiber layer.

3. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the interception efficiency of the filter membrane to particles with the particle diameter of more than 70nm is more than 99%;

The time required for 50ml of water to pass through a filter membrane with a diameter of 47mm is 25-300s under the conditions that the pressure is-0.03 MPa and the temperature is 20 ℃.

4. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the tensile strength of the filter membrane is 3-10MPa; the elongation at break is 30-60%.

5. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the average pore diameter of the coarse fiber layer in the area close to the first porous surface is larger than that of the area close to the second porous surface, and the average diameter of the coarse fiber in the coarse fiber layer in the area close to the first porous surface is larger than that of the coarse fiber in the area close to the second porous surface; and/or the average pore diameter of the area close to the second porous surface in the fine fiber layer is smaller than the average pore diameter of the area close to the first porous surface, and the average diameter of the fine fiber of the area close to the second porous surface in the fine fiber layer is smaller than the average diameter of the fine fiber of the area close to the first porous surface.

6. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the thickness of the filter membrane is 50-110 mu m, the porosity is 45-80%, and the average pore diameter is 100-800nm.

7. The coarse and fine fiber-blended polymeric filter membrane of claim 6, wherein: the porosity of the coarse fiber layer is 50-85%, and the porosity of the fine fiber layer is 25-65%.

8. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the fine fiber layer has a thickness of 10-25 μm and the coarse fiber layer has a thickness at least 30 μm greater than the fine fiber layer thickness.

9. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the average pore diameter of the first porous surface is 1000-6000nm, and the average pore diameter of the second porous surface is 15-65nm.

10. The coarse and fine fiber commingled polymeric filter membrane of claim 9, wherein: the first porous surface comprises first holes with the pore diameter of 0.4-14 mu m and the pore density of 15-45/1000 mu m ²; the second porous surface comprises second holes with the pore diameter of 10-110nm and the pore density of 25-130/10 ⁶nm².

11. The coarse and fine fiber commingled polymeric filter membrane of claim 10, wherein: the first porous surface has a pore area ratio of 10-30%; the second porous surface has a pore area ratio of 3-14%.

12. A coarse and fine fiber commingled polymeric filter membrane of claim 1, wherein: the porosity of the transition layer is 30-75%.

13. The coarse and fine fiber commingled polymeric filter membrane of claim 12, wherein: the number of coarse fibers with the diameter of 300-1500nm in the transition layer accounts for 10-30% of the total number of fibers, and the number of fine fibers with the diameter of 25-95nm accounts for 5-30% of the total number of fibers.

14. The coarse and fine fiber commingled polymeric filter membrane of claim 12, wherein: the average pore diameter of the transition layer is 200-350nm; the thickness of the transition layer is 10-40% of the thickness of the fine fiber layer.

15. A coarse and fine fiber-blended polymeric filter membrane according to claim 1, wherein: the IPA bubble point bubble pressure of the filter membrane is 200-300KPa;

The pure water flux of the filter membrane is 30-100ml/cm ².min under the conditions of 0.1MPa and 25 ℃.

16. A method of preparing a coarse and fine fiber-blended polymeric filter membrane according to any one of claims 1 to 15, wherein: the method comprises the following steps:

S1: preparing a casting solution with the viscosity of 3000-8000 mPas, and casting the casting solution on a carrier to form a liquid film; wherein the casting film liquid comprises the following substances in parts by weight: 6-15 parts of sulfone polymer, 60-85 parts of polar solvent and 5-20 parts of hydrophilic additive;

the sulfone polymer is any one of polyether sulfone, bisphenol A polysulfone and polyarylsulfone;

the polar solvent is at least one of butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethyl pyrrolidone, dimethylacetamide and N-methyl pyrrolidone;

The additive is a mixture of diglyme, lithium tert-butoxide and polyvinylpyrrolidone, and the mass ratio of the additive to the mixture is 3:1:2;

S2: inducing the liquid film to perform pre-phase separation, and blowing air flow with absolute humidity of 10g H ₂O/kg~30g H₂ O/kg to the surface of the liquid film for treatment in the environment with the temperature of 35-50 ℃ to ensure that the relative speed between the air flow and the liquid film is not more than 3m/min and the duration is not more than 60s, so as to form a semi-finished film;

S3: then immersing the semi-finished film into water with the temperature of 0-10 ℃ for solidification, wherein the duration is at least 25s, and further solidifying to form a solid film;

S2, after a semi-finished film is formed, immersing the semi-finished film into water with the temperature of 15-30 ℃ for partial curing, wherein the curing time is 5-15S; immersing in water at 0-10deg.C for at least 25 seconds to cure and form solid film.

17. Use of a coarse and fine fiber-blended polymeric filter membrane according to any one of claims 1 to 15, wherein: the filter membrane is used in the field of printing ink; the ultra-pure filter is used for ultra-pure filtration in the semiconductor industry.