阅读说明：本技术 一种孔隙均匀的半透膜支撑体制备方法 (Preparation method of semi-permeable membrane support body with uniform pores ) 是由 不公告发明人 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种孔隙均匀的半透膜支撑体制备方法,包括以下步骤：制浆、上网成型、烘干、热压；热压包括第一道硬压、预热和第二道硬压；浆料中,半透膜支撑体包括主体纤维、粘结纤维、固体颗粒,固体颗粒内部还包含有磁性纳米颗粒,本发明在半透膜支撑体制备过程中添加了固体颗粒,固体颗粒会优先占据半透膜支撑体较大孔隙位置,使得由于低密度缺陷引起的大孔径消失,降低了缺陷数量；涂敷半透膜后,仍有一些位置因无纺布缺陷产生的亮斑,可以在平面灯下显现出来,在缺陷位置增加交变磁场,磁性纳米颗粒会产生大量热量,融化颗粒物和粘结纤维,使得颗粒物和粘结纤维融化堵塞缺陷位置孔隙,解决了缺陷位置因半透膜破损造成的脱盐率下降的问题。(The invention discloses a preparation method of a semipermeable membrane support body with uniform pores, which comprises the following steps: pulping, forming on a net, drying and hot pressing; the hot pressing comprises a first hard pressing, preheating and a second hard pressing; in the slurry, the semipermeable membrane support comprises main fibers, bonding fibers and solid particles, and the magnetic nanoparticles are contained in the solid particles; after the semipermeable membrane is coated, bright spots generated by defects of non-woven fabrics at some positions can be displayed under a plane lamp, an alternating magnetic field is added at the defect position, magnetic nanoparticles can generate a large amount of heat to melt particles and bonding fibers, so that the particles and the bonding fibers are melted to block pores at the defect position, and the problem of reduction of desalination rate caused by damage of the semipermeable membrane at the defect position is solved.)

1. The preparation method of the semi-permeable membrane support body with uniform pores is characterized by comprising the following steps of:

pulping: adding the main body fiber, the bonding fiber and the solid particles into a fiber dispersion machine, adding water until the concentration of the slurry is 0.2-0.5%, and stirring to obtain fiber slurry;

and (3) net surfing molding: conveying the fiber pulp into a high-level pulp stabilizing box by using a special chemical fiber pump, regulating the concentration of the fiber pulp to be 0.02-0.05% through processes of pulp flushing, screening and the like for multiple times, conveying the fiber pulp to a central pulp distributor and an inclined net full-flow type pulp box, conveying the fiber pulp to a forming net through the inclined net pulp box, and dehydrating and forming to obtain a wet fiber net;

drying: drying the wet fiber web by using a yankee cylinder, wherein the temperature of the yankee cylinder is 120 ℃, the blanket forms a wrap angle of 90-120 degrees on the wet fiber web, the drying time is 30-40s, and the wet paper is dried in the wrap angle area;

hot pressing: the hot pressing comprises a first hard pressing, preheating and a second hard pressing;

the first hard pressing adopts a mode of pressing two groups of steel rollers oppositely, the temperature of an upper steel roller is 10-30 ℃ higher than the thermal deformation temperature of the main fiber, the temperature of a lower steel roller is 10-20 ℃ higher than the temperature of the main fiber, the linear speed is 5-20m/min, and the linear pressure is 80-120 kN/m;

preheating, wherein the preheating temperature is 0-10 ℃ lower than the thermal deformation temperature of the main fiber;

the second hard pressing adopts a mode of pressing by two groups of steel rollers, and the temperature of the steel rollers is 5-10 ℃ higher than the thermal deformation temperature of the solid particles.

2. The method as claimed in claim 1, wherein the semi-permeable membrane support comprises 50-70 parts of main fiber, 30-40 parts of binding fiber and 5-10 parts of solid particles.

3. The method for preparing a semipermeable membrane support having uniform pores according to claim 1, wherein the main fiber is a fiber spun from synthetic resin such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile, etc.; the diameter of the main body fiber is 6-10 μm, and the length is 3-6 mm.

4. The method of claim 1, wherein the bonding fiber is one or more of core-shell fiber, side-by-side fiber, sea-island fiber; the diameter of the bonding fiber is 10-12 μm, and the length is 3-6 mm.

5. The method as claimed in claim 1, wherein the solid particles are particles made of synthetic resin such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile, etc., and the thermal deformation temperature of the solid particles is not higher than that of the main fibers and not lower than the melting point of the binder fibers.

6. The method as claimed in claim 1, wherein the solid particles have a particle size of 10-14 μm.

7. The method as claimed in claim 1, wherein the solid particles further contain magnetic nanoparticles, the magnetic nanoparticles may be iron, cobalt, nickel, ferrite, etc., and the magnetic nanoparticles account for 3% -5% of the total mass of the solid particles.

8. The method as claimed in claim 7, wherein the solid particles are prepared by the following steps:

the method comprises the following steps: ultrasonically dispersing magnetic nanoparticles with the average particle size of 200-400nm and a silane coupling agent KH570 in toluene to obtain dispersion liquid, wherein the mass ratio of the magnetic nanoparticles to the silane coupling agent KH570 is 1-3:1, stirring for 4 hours in a nitrogen atmosphere, and dissolving glycerol methacrylate and AlBN in the toluene, wherein the mass ratio of the glycerol methacrylate to the magnetic nanoparticles is 3-5: 5, the mass ratio of AlBN to the glycerol methacrylate is 1: 10-25, adding the mixture into the dispersion, stirring the mixture for 2 hours at the temperature of 80 ℃ in the nitrogen atmosphere, drying the mixture, extracting the dried mixture by using acetone, and removing a coupling agent and a toluene solvent to obtain modified magnetic nanoparticles;

step two: preheating modified magnetic nanoparticles at 90 ℃, adding the modified magnetic nanoparticles into PET polyester preheated and melted at 90 ℃, wherein the modified magnetic nanoparticles account for 3-5% of the total mass, and uniformly stirring for 2h to obtain mixed PET polyester;

step three: and extruding and granulating the mixed PET polyester.

9. The method as claimed in claim 1, wherein the semipermeable membrane support has a grammage of 70-90g/m²The thickness is 90-110 μm, and the air permeability is 0.9-1.3cm³/cm²And s, the concentration of the pore diameter distribution of 9-12 mu m is more than 95 percent.

10. The method for manufacturing a semipermeable membrane support having uniform pores according to claim 1, wherein the semipermeable membrane support is provided with a coating layer, an intermediate layer and a non-coating layer along the thickness direction, the cross-sectional major axis/minor axis of the fiber of the coating layer is 1.3-1.9, the smoothness of the coating surface is 20-30s, the cross-sectional major axis/minor axis of the fiber of the non-coating layer is 1.2-1.5, and the smoothness of the non-coating surface is 15-25 s.

Technical Field

The invention relates to the technical field of preparation of semipermeable membrane supports, in particular to a preparation method of a semipermeable membrane support with uniform pores.

Background

Semipermeable membranes have been widely used in the fields of removal of impurities in beverages/industrial water, desalination of sea water, removal of miscellaneous bacteria in foods, and biochemistry of drainage.

The semipermeable membrane has three layers: polyamide layer, polysulfone layer and support. Various characteristic parameters of the support body such as air permeability, thickness, gram weight, transverse and longitudinal tensile strength and the like can meet the use requirements of the semipermeable membrane, but after the polysulfone layer is coated on the non-woven fabric, local defects such as pinholes and bright spots are usually generated, and in the use of the semipermeable membrane, the pinholes, the bright spots and other places are easily damaged to reduce the desalination rate, so that the use time is reduced.

The pinholes and bright spots are mainly caused by uneven fiber distribution and large pore size distribution range. The support body is prepared by a method of compounding multiple layers of non-woven fabrics, the defects are reduced in a mutually-covered mode, but the working procedures are increased undoubtedly, and the production cost is increased.

Disclosure of Invention

The present invention aims to provide a method for preparing a semipermeable membrane support with uniform pores, which overcomes the defects of the prior art.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a method for preparing a semi-permeable membrane support body with uniform pores comprises the following steps:

pulping: adding the main body fiber, the bonding fiber, the solid particles and the dispersing agent into a fiber dispersing machine, adding water until the concentration of the slurry is 0.2-0.5%, and stirring to obtain fiber slurry;

and (3) net surfing molding: conveying the fiber pulp into a high-level pulp stabilizing box by using a special chemical fiber pump, regulating the concentration of the fiber pulp to be 0.02-0.05% through processes of pulp flushing, screening and the like for multiple times, conveying the fiber pulp to a central pulp distributor and an inclined net full-flow type pulp box, conveying the fiber pulp to a forming net through the inclined net pulp box, and dehydrating and forming to obtain a wet fiber net;

drying: drying the wet fiber web by using a yankee cylinder, wherein the temperature of the yankee cylinder is 120 ℃, the blanket forms a wrap angle of 90-120 degrees on the wet fiber web, the drying time is 30-40s, and the wet paper is dried in the wrap angle area;

hot pressing: the hot pressing comprises a first hard pressing, preheating and a second hard pressing;

the first hard pressing adopts a mode of pressing two groups of steel rollers oppositely, the temperature of an upper steel roller is 10-30 ℃ higher than the thermal deformation temperature of the main fiber, the temperature of a lower steel roller is 10-20 ℃ higher than the temperature of the main fiber, the linear speed is 5-20m/min, and the linear pressure is 80-120 kN/m;

preheating, wherein the preheating temperature is 0-10 ℃ lower than the thermal deformation temperature of the main fiber;

the second hard pressing adopts a mode of pressing by two groups of steel rollers, and the temperature of the steel rollers is 5-10 ℃ higher than the thermal deformation temperature of the solid particles.

Furthermore, the semipermeable membrane support comprises 50-70 parts of main fiber, 30-40 parts of bonding fiber, 5-10 parts of solid particles and 0.2-0.8 part of dispersing agent.

Further, the main fiber may be a fiber spun from synthetic resins such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile, and the like; the diameter of the main body fiber is 6-10 μm, and the length is 3-6 mm.

Further, the bonding fiber can be one or more of a core-shell fiber, a side-by-side fiber, an island fiber; the diameter of the bonding fiber is 10-12 μm, and the length is 3-6 mm.

Further, the solid particles may be particles formed by synthetic resins such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile and the like, and the heat distortion temperature of the solid particles is not higher than that of the main fiber and is not lower than the melting point of the bonding fiber.

Further, the particle size of the solid particles is 10-14 μm.

Further, magnetic nanoparticles are contained in the solid particles, the magnetic nanoparticles can be iron, cobalt, nickel, ferrite and other magnetic nanoparticles, and the magnetic nanoparticles account for 3% -5% of the total mass of the solid particles.

Further, the preparation method of the solid particles comprises the following steps:

the method comprises the following steps: ultrasonically dispersing magnetic nanoparticles with the average particle size of 200-400nm and a silane coupling agent KH570 in toluene to obtain dispersion liquid, wherein the mass ratio of the magnetic nanoparticles to the silane coupling agent KH570 is 1-3:1, stirring for 4 hours in a nitrogen atmosphere, and dissolving glycerol methacrylate and AlBN in the toluene, wherein the mass ratio of the glycerol methacrylate to the magnetic nanoparticles is 3-5: 5, the mass ratio of AlBN to the glycerol methacrylate is 1: 10-25, adding the mixture into the dispersion, stirring the mixture for 2 hours at the temperature of 80 ℃ in the nitrogen atmosphere, drying the mixture, extracting the dried mixture by using acetone, and removing a coupling agent and a toluene solvent to obtain modified magnetic nanoparticles;

step two: preheating modified magnetic nanoparticles at 90 ℃, adding the modified magnetic nanoparticles into PET polyester preheated and melted at 90 ℃, wherein the modified magnetic nanoparticles account for 3-5% of the total mass, and uniformly stirring for 2h to obtain mixed PET polyester;

step three: and extruding and granulating the mixed PET polyester.

Further, the gram weight of the semipermeable membrane support body is 70-90g/m²The thickness is 90-110 μm, and the air permeability is 0.9-1.3cm³/cm²And s, the concentration of the pore diameter distribution of 9-12 mu m is more than 95 percent.

Furthermore, the semipermeable membrane support body is provided with a coating layer, a middle layer and a non-coating layer along the thickness direction, the cross section major axis/minor axis of the fiber of the coating layer is 1.3-1.9, the smoothness of the coating surface is 20-30s, the cross section major axis/minor axis of the fiber of the non-coating layer is 1.2-1.5, and the smoothness of the non-coating surface is 15-25 s.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:

according to the invention, the solid particles are added in the preparation process of the semipermeable membrane support body, and the solid particles can preferentially occupy the larger pore position of the semipermeable membrane support body, so that the large pore diameter caused by the low-density defect disappears, and the number of defects is reduced; after the semipermeable membrane is coated, some positions still have bright spots due to the defects of the non-woven fabric, the bright spots can be displayed under a plane lamp, an alternating magnetic field is added at the defect position, the magnetic nanoparticles can generate a large amount of heat to melt particles and bonding fibers, so that the particles and the bonding fibers are melted to block the pores of the defect position, and the problem of the reduction of the desalination rate of the defect position due to the damage of the semipermeable membrane is solved. Because the heat conductivity of the organic matters is poor, and the melting point of the main body fibers is not lower than that of the solid particles, the framework can still be maintained to be not deformed under the condition that the solid particles are molten.

Detailed Description

The following examples further describe embodiments of the present invention in detail. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The invention discloses a preparation method of a semipermeable membrane support body with uniform pores, which comprises the following steps:

pulping: adding the main body fiber, the bonding fiber, the solid particles and the dispersing agent into a fiber dispersing machine, adding water until the concentration of the slurry is 0.2-0.5%, and stirring to obtain fiber slurry;

and (3) net surfing molding: conveying the fiber slurry into a high-level slurry stabilizing box by using a special chemical fiber pump, controlling the flow of the fiber slurry, stabilizing a pressure head of the fiber slurry, regulating the concentration of the fiber slurry to be 0.02-0.05% through processes of multiple times of slurry flushing, screening and the like, conveying the fiber slurry to a central slurry distributor and an inclined-net full-flow type flow box, conveying the fiber slurry to a forming net through the inclined-net flow box, and dehydrating and forming to obtain a wet fiber net;

drying: drying the wet fiber web by using a yankee cylinder, wherein the temperature of the yankee cylinder is 120 ℃, the blanket forms a wrap angle of 90-120 degrees on the wet fiber web, the drying time is 30-40s, and the wet paper is dried in the wrap angle area; the blanket is cleaned by a high-pressure water gun, dried and dried for recycling;

hot pressing: the hot pressing comprises a first hard pressing, preheating and a second hard pressing;

the first hard pressing adopts a mode of pressing two groups of steel rollers oppositely, the temperature of an upper steel roller is 10-30 ℃ higher than the thermal deformation temperature of the main fiber, the temperature of a lower steel roller is 10-20 ℃ higher than the temperature of the main fiber, the linear speed is 5-20m/min, and the linear pressure is 80-120 kN/m; after the first hot pressing, the fibers on the surface of the coating surface/the surface of the non-coating surface deform, and the leakage of internal particles can be prevented when the next hot pressing is carried out while the target smoothness is achieved. The temperature in the non-woven fabric is low due to the short pressing area and insufficient heating time, the bonding fibers do not start to melt and deform, the particles can still move in the non-woven fabric, and the particles can move to the position with a larger aperture under pressure;

preheating, wherein the preheating temperature is 0-10 ℃ lower than the thermal deformation temperature of the main fiber;

the second hard pressing adopts a mode of pressing by two groups of steel rollers, and the temperature of the steel rollers is 5-10 ℃ higher than the thermal deformation temperature of the solid particles. Through preheating, the internal temperature of the non-woven fabric can reach the melting point of the bonding fibers and the thermal deformation temperature of the particles during the second hot pressing, so that the particles can be locked during the second hot pressing.

Furthermore, in the process from forming to hot pressing, the base paper is wrapped and clamped by the blanket, so that particles on the surface of the non-woven fabric are taken away while paper breaking is prevented.

Furthermore, when the semipermeable membrane support is produced, bright spots are detected on line, the mark is made, the treatment is carried out after off-line, and the acting area of the hand-held alternating magnetic field generator is about 10-20 microns in diameter, the magnetic field intensity is 5-10kA/m, and the magnetic field frequency is 10-15 kHz.

Furthermore, the semipermeable membrane support comprises 50-70 parts of main fiber, 30-40 parts of bonding fiber, 5-10 parts of solid particles and 0.2-0.8 part of dispersing agent. Solid particles are added in the preparation process of the semipermeable membrane support body. The solid particles will preferentially occupy larger pore positions on the semipermeable membrane support, so that large pore diameters caused by low-density defects disappear, and the number of defects is reduced.

Further, the main fiber may be a fiber spun from synthetic resins such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile, and the like; the diameter of the main body fiber is 6-10 μm, and the length is 3-6 mm; the melting point of the main fiber is 250-260 ℃, and the thermal deformation temperature is 190-200 ℃.

Further, the bonding fiber can be one or more of core-shell fiber, side-by-side fiber and sea-island fiber, and is preferably a one-component low-melting-point polyester fiber; the diameter of the bonding fiber is 10-12 μm, the length is 3-6mm, and the melting point of the bonding fiber is 170-190 ℃.

Further, the solid particles may be particles formed by synthetic resins such as polypropylene, polyacrylate, polyurethane, polyester, polyamide, polyimide, polyacrylonitrile and the like, and the heat distortion temperature of the solid particles is not higher than that of the main fiber and is not lower than the melting point of the bonding fiber.

Further, the dispersing agent is one or a combination of PEO type polyoxyethylene ether and PAM type polyacrylamide.

Further, the particle size of the solid particles is 10-14 μm.

Further, magnetic nanoparticles are contained in the solid particles, the magnetic nanoparticles can be iron, cobalt, nickel, ferrite and other magnetic nanoparticles, and the magnetic nanoparticles account for 3% -5% of the total mass of the solid particles. Ferrite particles are preferred in this embodiment. The content of the magnetic nano-particles can affect the suspension condition of solid particles in the slurry, and too high content can cause the particles to precipitate too fast, so that the finished paper is not uniform.

Further, the preparation method of the solid particles comprises the following steps:

the method comprises the following steps: ultrasonically dispersing magnetic nanoparticles with the average particle size of 200-400nm and a silane coupling agent KH570 in toluene to obtain dispersion liquid, wherein the mass ratio of the magnetic nanoparticles to the silane coupling agent KH570 is 1-3:1, stirring for 4 hours in a nitrogen atmosphere, and dissolving glycerol methacrylate and AlBN in the toluene, wherein the mass ratio of the glycerol methacrylate to the magnetic nanoparticles is 3-5: 5, the mass ratio of AlBN to the glycerol methacrylate is 1: 10-25, adding the mixture into the dispersion, stirring the mixture for 2 hours at the temperature of 80 ℃ in the nitrogen atmosphere, drying the mixture, extracting the dried mixture by using acetone, and removing a coupling agent and a toluene solvent to obtain modified magnetic nanoparticles;

step two: preheating modified magnetic nanoparticles at 90 ℃, adding the modified magnetic nanoparticles into PET polyester preheated and melted at 90 ℃, wherein the modified magnetic nanoparticles account for 3-5% of the total mass, and uniformly stirring for 2h to obtain mixed PET polyester;

step three: and extruding and granulating the mixed PET polyester.

Further, the gram weight of the semipermeable membrane support body is 70-90g/m²The thickness is 90-110 μm, and the air permeability is 0.9-1.3cm³/cm²And s, the concentration of the pore diameter distribution of 9-12 mu m is more than 95 percent.

Furthermore, the semipermeable membrane support body is provided with a coating layer, a middle layer and a non-coating layer along the thickness direction, the cross section major axis/minor axis of the fiber of the coating layer is 1.3-1.9, the smoothness of the coating surface is 20-30s, the cross section major axis/minor axis of the fiber of the non-coating layer is 1.2-1.5, and the smoothness of the non-coating surface is 15-25 s.

Example 1

A semipermeable membrane support comprising: 65 parts of main fiber (PET fiber, diameter 7.3 μm, length 5mm, melting point 250 ℃, heat distortion temperature 190 ℃), 30 parts of bonding fiber (low-melting PET fiber, diameter 10 μm, length 5mm, melting point 180 ℃), and 5 parts of solid particles (PET particles, magnetic nanoparticles are Fe₃O₄Particles accounting for 3 percent of the total mass, the diameter of the particles is 12 mu m, the melting point is 250 ℃, the heat distortion temperature is 190 ℃) and 0.5 part of dispersing agent.

The preparation method comprises the following steps:

pulping and forming: adding the components into a fiber dispersion machine, adding water to prepare suspension slurry with the concentration of 0.2%, and carrying out net-feeding molding at the concentration of 0.02%;

squeezing and drying: the squeezing pressure is 40kN/m, the drying temperature is 120 ℃, and the corner wrapping drying time is 30 s;

hot-pressing vehicle speed: 20 m/min; first-pass hard pressing: the two groups of steel rollers are pressed oppositely, the temperature of an upper steel roller is 210 ℃, the temperature of a lower steel roller is 200 ℃, and the linear pressure is 100 kN/m; preheating: the preheating temperature is 185 ℃; second hard pressing: the two groups of steel rollers are in a counter-pressing mode, the temperature of the steel rollers is 195 ℃, and the linear pressure is 100 kN/m.

After the support was prepared in the above manner, a polysulfone film (semipermeable membrane) was formed on the coated surface of the semipermeable membrane support by coating a polysulfone resin (Udel P-3500LCD MB3 manufactured by SOLVAY Co., Ltd., molecular weight 78000 to 84000g/mol) in N, N-Dimethylformamide (DMF) solution (concentration 22%) on the coated surface of the semipermeable membrane support, washing with water, and drying to obtain a filtration membrane. And (3) placing a 20 m-1 m semi-permeable membrane on a flat lamp, and marking when an abnormally bright spot appears, namely a bright spot or a pinhole.

The needle points are adopted to puncture the defects (2 of the defects are punctured) at the marked positions, a handheld alternating magnetic field generator is adopted to apply a magnetic field at the punctured defect positions to carry out pore sealing treatment, the acting area is 20 micrometers in diameter, the magnetic field intensity is 10kA/m, and the magnetic field frequency is 12 kHz.

Example 2

Other parameters were kept consistent with example 1, and the magnetic nanoparticles Fe in the solid particles were adjusted₃O₄To 5%.

Example 3

Other parameters were kept consistent with example 1, and the magnetic nanoparticles Fe in the solid particles were adjusted₃O₄To 4%.

Comparative example 1

Other parameters were kept consistent with example 1, adjusting the semipermeable membrane support composition to: 65 parts of a main fiber (PET fiber, diameter 7.3 μm, length 5mm, melting point 250 ℃ C., heat distortion temperature 190 ℃ C.), and 35 parts of a binder fiber (low-melting PET fiber, diameter 10 μm, length 5mm, melting point 180 ℃ C.).

Comparative example 2

Other parameters were kept in accordance with example 1, and Fe in the solid particles was adjusted₃O₄To 1%.

Comparative example 3

Other parameters were kept in accordance with example 1, and Fe in the solid particles was adjusted₃O₄To 7%.

Comparative example 4

The other parameters were kept in accordance with example 1, the first pass was adjusted: the two groups of steel rollers are pressed oppositely, the temperature of the upper steel roller is 195 ℃, the temperature of the lower steel roller is 195 ℃, and the linear pressure is 100 kN/m.

The following measurements and evaluations were performed on the semipermeable membrane supports obtained in the above examples and comparative examples, and the reference standards of the relevant technical indexes were as follows, and the results are shown in table 1.

1) Gram weight test method: the "gram weight" of the semipermeable membrane support material is determined according to the method of GB/T451.2-2002.

2) The thickness test method comprises the following steps: the "thickness" of the semipermeable membrane support material is determined according to the method of GB/T451.3-2002.

3) Smoothness test method: the measurement was carried out according to JIS P8119 using a Beck smoothness tester.

4) Air permeability test method: "air permeability" of semipermeable membrane support material was measured in cm using a Frazier-type testing machine in accordance with JIS L1096-2010³/cm²/s。

5) Fiber diameter test method: when the fiber section major axis of the semipermeable membrane supporting material is measured, the width of the main body fiber (namely data vertical to the fiber length direction) on the coating surface and the non-coating surface of the semipermeable membrane supporting material can be observed by directly adopting a scanning electron microscope, the section of the semipermeable membrane supporting material can also be observed after the semipermeable membrane supporting material is brittle at low temperature, the fiber section is generally in an oval shape or is close to an oval shape, the dimension of the fiber section major axis along the pressure vertical direction is the fiber section major axis, and the dimension parallel to the pressure direction is the fiber section minor axis. The cross-sectional major axes of the following examples and comparative examples were observed by directly observing the widths of the bulk fibers on the coated and uncoated sides thereof using a scanning electron microscope.

6) The bright spot pinhole testing method comprises the following steps: a filtration membrane was obtained by coating a N, N-Dimethylformamide (DMF) solution (concentration: 22%) of polysulfone resin (Udel P-3500LCD MB3, manufactured by SOLVAY Co., Ltd., molecular weight: 78000 to 84000g/mol) on the coating surface of a semipermeable membrane support using a missing-corner wheel coater having a constant gap, washing with water, and drying to form a polysulfone membrane (semipermeable membrane) on the coating surface of the semipermeable membrane support. And (3) placing a 20 m-by-1 m semi-permeable membrane on a flat lamp, wherein bright spots or pinholes are formed when abnormally bright spots occur, the size of the pinholes is smaller, the brightness is higher, marks are marked on the abnormally bright spots, and the number of the marks is counted.

7) Semi-permeable membrane defect closure test method: using a missing corner wheel coater with a constant gap, on the coated face of a semi-permeable membrane supportA polysulfone membrane (semipermeable membrane) was formed on the coated surface of a semipermeable membrane support by washing with water and drying an N, N-Dimethylformamide (DMF) solution (concentration: 22%) coated with polysulfone resin (Udel P-3500LCD MB3, manufactured by SOLVAY Co., Ltd., molecular weight: 78000-84000 g/mol) to obtain a filtration membrane. And (3) placing 20m by 1m of semi-permeable membrane on a flat lamp, and obtaining bright spots or pinholes when abnormal bright spots appear. And (3) puncturing the defects (2 of the defects) at the bright spot positions of the pinholes by using needle points, arranging a local magnetic field at the positions of the defects, and testing the desalination rate of the defects after the defects are subjected to sealing treatment. At 150psi, water temperature 20-28 deg.C, effective area of membrane 42.40cm²The membrane salt rejection was tested using 1500ppm NaCl solution as feed solution. The salt rejection of more than 98% is marked by "√", otherwise by "×".

TABLE 1

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.