CN106310782B - Nanofiber filtering membrane, nanofiber composite filtering membrane and preparation method thereof - Google Patents
Nanofiber filtering membrane, nanofiber composite filtering membrane and preparation method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/08—Filter cloth, i.e. woven, knitted or interlaced material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/0001—Making filtering elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
- B01D46/543—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
- B01D46/546—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using nano- or microfibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/56—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with multiple filtering elements, characterised by their mutual disposition
- B01D46/62—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with multiple filtering elements, characterised by their mutual disposition connected in series
- B01D46/64—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with multiple filtering elements, characterised by their mutual disposition connected in series arranged concentrically or coaxially
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
- B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
- B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/02—Types of fibres, filaments or particles, self-supporting or supported materials
- B01D2239/025—Types of fibres, filaments or particles, self-supporting or supported materials comprising nanofibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
- B01D2239/0604—Arrangement of the fibres in the filtering material
- B01D2239/0631—Electro-spun
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
- B01D2239/065—More than one layer present in the filtering material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
- B01D2239/10—Filtering material manufacturing
Abstract
The invention provides a nanofiber filtering membrane, a nanofiber composite filtering membrane and a preparation method thereof. The nanofiber filtering membrane and the nanofiber filtering composite membrane have the hollow structure with the through holes in the surface layer, so that the service life is longer while the filtering efficiency is improved and the air resistance is reduced. The nanofiber filtering membrane and the preparation method of the nanofiber composite filtering membrane are prepared through coaxial electrostatic spinning. The air filter has wide application value in the field of air filtration, and has great application prospect in products such as air purifiers, automobile filter elements, masks and the like.
Description
Technical Field
The invention belongs to the technical field of preparation of filter materials, and particularly relates to a hollow porous nanofiber filter membrane with high efficiency, low resistance and long service life, a composite filter material (or called as a composite filter membrane) and a preparation method thereof.
Background
Since the innovation of China, the living standard of people is improved day by day, but the living environment is deteriorated day by day, and the influence of the air quality on the health of human bodies becomes an important problem of general social attention. Especially, particulate matter (PM2.5) having a particle size of less than 2.5 μm suspended in the air is not only a significant cause of haze weather but also one of the major factors causing respiratory diseases and cardiovascular diseases, and thus effective filtration thereof has been in the spotlight.
Conventional nonwoven filter materials have been widely used in a variety of filter products, such as: glass fiber, polypropylene fiber, polyester fiber, polytetrafluoroethylene fiber and the like are widely applied to products such as air purifiers, automobile air conditioner filter elements, masks and the like. However, the conventional nonwoven filter material has a large fiber diameter, and a large filtration pore formed by stacking the fibers has poor filtration performance for particles with a small particle size. There is a need for a more efficient air filtration material for filtering fine particulate matter.
The nanofiber prepared by electrostatic spinning has the advantages of small fiber diameter, small pore diameter, high porosity, large specific surface area and the like, and the composite filter material prepared by compounding the nanofiber with a nonwoven filter material base material has better filtering efficiency, wherein the nonwoven filter material base material mainly filters particles with larger particle size, and the electrostatic spinning fiber layer mainly filters particles with smaller particle size. Currently, the nanofiber structure spun by electrospinning has a solid circular cross section (as shown in fig. 1), a bead shape, a flat shape or a ribbon shape, and the like, and although the existing nanofiber has different fiber structures, the filtration membrane of the existing nanofiber still has the problems of low filtration efficiency, large air resistance and short service life. How to prolong the service life of a filtering membrane while improving the filtering efficiency and reducing the air resistance is a technical problem to be solved urgently in the preparation technology of the fiber filtering material at present.
Disclosure of Invention
In view of the problems in the prior art, the present invention is directed to solving at least one of the above-mentioned deficiencies in the prior art. For example, an object of the present invention is to provide a nanofiber filtration membrane/composite filtration membrane having a high filtration rate, a small air resistance and a long service life, and a method for producing the same.
In order to achieve the above object, an aspect of the present invention provides a nanofiber filtration membrane. The nanofiber filtering membrane is a filtering structure formed of nanofibers, the nanofibers comprising: a skin layer; a tubular cavity formed by the skin layer and distributed along the axial direction of the fiber; a plurality of through holes formed in the skin layer and communicating with the tubular cavity through the skin layer.
In one embodiment of the nanofiber filtration membrane of the present invention, the nanofibers have an average outer diameter of 0.1 to 12 μm, the nanofibers have an average inner diameter of 0.05 to 9.5 μm, and the through holes have an average diameter of 0.01 to 5 μm.
In one embodiment of the nanofiber filtering membrane of the present invention, the tubular cavity may be a circular tube, and the through-holes may be circular through-holes.
In one embodiment of the nanofiber filtration membrane of the present invention, the nanofibers may be arranged in a staggered manner to form a staggered nanofiber filtration membrane.
In one embodiment of the nanofiber filtering membrane of the present invention, the thickness of the nanofiber membrane is 0.5 to 5 mm.
Another aspect of the present invention provides a nanofiber composite filtration membrane. The nanofiber composite filtering membrane comprises a substrate layer, a nanofiber filtering layer compounded on the substrate layer and a covering layer covering the nanofiber filtering layer, wherein the substrate layer, the nanofiber filtering layer and the covering layer form a sandwich structure, and the nanofiber filtering layer is the nanofiber filtering membrane.
In one embodiment of the nanofiber composite filtration membrane of the present invention, the substrate layer is a nonwoven material (i.e., a nonwoven filter material) that functions to filter larger particle size particles in air.
In one embodiment of the nanofiber composite filtering membrane of the present invention, the non-woven material may be glass fiber, polypropylene fiber, polyester fiber or polytetrafluoroethylene fiber non-woven fabric.
In one embodiment of the nanofiber composite filtration membrane of the present invention, the cover layer may be a polypropylene honeycomb network, a polyester honeycomb network, a metal honeycomb network, a polypropylene fiber nonwoven fabric or a polyester fiber nonwoven fabric.
In one embodiment of the nanofiber composite filtering membrane, the thickness of the nanofiber filtering layer is 0.5-5 mm.
In still another aspect, the present invention provides a method for preparing a nanofiber filtration membrane. The preparation method of the nanofiber filtering membrane adopts electrostatic spinning equipment to prepare the nanofiber filtering membrane, and comprises the following steps: dissolving a polymer in a first solvent to obtain a polymer dope, wherein the first solvent is composed of at least two solvents, and the first solvent at least comprises a solvent with a boiling point lower than 60 ℃; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofibers were deposited directly on the receiving electrode plate to form a nanofiber filtration membrane as described above.
In another aspect, the invention provides a preparation method of a nanofiber composite filtering membrane. The preparation method of the nanofiber composite filtering membrane adopts electrostatic spinning equipment to prepare the nanofiber composite filtering membrane, and comprises the following steps: dissolving a polymer in a first solvent to obtain a polymer dope, wherein the first solvent is composed of at least two solvents, and the first solvent at least comprises a solvent with a boiling point lower than 60 ℃; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofiber is directly deposited on the substrate layer to form a nanofiber filter layer; and paving a covering layer on the surface of the nanofiber filtering layer to form the nanofiber composite filtering membrane.
In one embodiment of the method for preparing a nanofiber filtration membrane or a nanofiber composite filtration membrane of the present invention, the polymer is polyglycolic acid, polylactic acid, polycaprolactone, polyoxymethylene, polystyrene, polymethyl methacrylate, polyethylene oxide, aliphatic polyester copolymer, polyamide, polycarbonate, polyurethane, polyethylene oxide, polyvinyl alcohol, cellulose acetate, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, or hydroxypropylcellulose.
In one embodiment of the preparation method of the nanofiber filtering membrane or the nanofiber composite filtering membrane, the inner diameter/outer diameter of the inner tube specification of the coaxial spinneret is 0.2-2/0.4-2.6 mm, the outer diameter/inner diameter of the outer tube specification of the coaxial spinneret is 0.5-3/0.7-3.6 mm, the flow rate of gas or a second solvent in the inner tube of the coaxial spinneret is 0.2-1 mL/h, the flow rate of a polymer spinning solution in the outer tube of the coaxial spinneret is 0.5-1.5 mL/h, the voltage is 7-30 kV, the receiving distance is 5-30 cm, the ambient temperature is 10-40 ℃, the relative humidity is 10-90% and the mass percentage concentration of the polymer spinning solution is 4-30% in the coaxial electrostatic spinning process.
In one embodiment of the method for manufacturing a nanofiber filtration membrane or a nanofiber composite filtration membrane of the present invention, the first solvent is at least two of dichloromethane, chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, acetone, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide, acetone, and water, and the second solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, acetone, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide, acetone, and water.
In an embodiment of the method for preparing the nanofiber filtering membrane or the nanofiber composite filtering membrane, the first solvent is compounded by two of N, N-dimethylacetamide and dichloromethane, or acetone and dichloromethane, or N, N-dimethylformamide and dichloromethane, or N, N-dimethylacetamide and carbon disulfide, or acetone and carbon disulfide.
In one embodiment of the method for producing a nanofiber filtration membrane or a nanofiber composite filtration membrane of the present invention, the first solvent is composed of a low-boiling-point solvent and a high-boiling-point solvent, wherein the boiling point of the low-boiling-point solvent is lower than 60 ℃, the boiling point of the high-boiling-point solvent is higher than that of the low-boiling-point solvent, and the volume ratio of the low-boiling-point solvent to the high-boiling-point solvent is 1:1 to 8: 1.
Compared with the prior art, the beneficial technical effects of the invention comprise:
(1) the invention firstly introduces the nano-fiber which is prepared by electrostatic spinning and has a hollow structure with a through-hole on the surface layer into the filter material, and obtains the nano-fiber with a unique structure by coaxial electrostatic spinning, controlling the temperature and the humidity in the spinning environment, controlling the polymer concentration of the spinning solution on the surface layer, the solvent composition and other process parameters.
(2) The nanofiber in the nanofiber filtering membrane prepared by the invention has a hollow structure with a through hole on the surface layer, the specific surface area of the material is increased, the air flow path is increased, the particulate matter storage space is increased, the filtering efficiency of the filtering membrane is improved, the air resistance is reduced, the service life is prolonged, and the comprehensive filtering performance of the nanofiber filtering membrane is superior to that of the conventional nanofiber filtering material.
(3) The nanofiber composite filter material prepared by the invention has high filtering efficiency, low air resistance and long service life, has wide application value in the field of air filtration, and has great application prospect in products such as air purifiers, automobile filter elements, masks and the like.
Drawings
Fig. 1 shows a prior art nanofiber structure.
FIG. 2 shows a schematic view of a nanofiber filtration membrane according to an exemplary embodiment of the present invention.
Fig. 3a is a front view of the nanofiber of fig. 2.
Fig. 3b is a perspective view of fig. 3 a.
Fig. 4 shows a schematic structural view of a nanofiber composite filtration membrane according to an exemplary embodiment of the present invention.
Description of reference numerals:
1-nanofiber, 2-filter gap, 3-skin, 4-core (or called hollow part, tubular cavity), 5-through hole, 6-base layer (or called receiving substrate, base layer), 7-nanofiber filter layer and 8-cover layer.
Detailed Description
Hereinafter, a nanofiber filtration membrane/nanofiber composite filtration membrane and a method for preparing the same according to the present invention will be described in detail with reference to the exemplary embodiments and the accompanying drawings.
As shown in fig. 1, the applicant found that the short service life of the present composite filter material is caused by the fact that during the use process, the particles block the pores 2 between the fibers, which causes a great reduction in the filtration efficiency, and at this time, the filter material needs to be replaced. Therefore, the invention provides the nanofiber filter membrane with the hollow skin layer having the through-hole structure, the nanofiber composite filter membrane and the preparation method thereof, which have the advantages of high efficiency, low resistance and long service life, so that the filter efficiency is improved, the air resistance is reduced, and the service life is longer.
FIG. 2 shows a schematic view of a nanofiber filtration membrane according to an exemplary embodiment of the invention; FIG. 3a is a front view of the nanofiber of FIG. 2; fig. 3b is a perspective view of fig. 3 a. As shown in fig. 2, 3a and 3b, the nanofiber filtration membrane according to the exemplary embodiment of the present invention has a filtration structure formed of nanofibers 1, for example, the nanofibers are arranged in a staggered manner to form a staggered nanofiber filtration membrane.
The nanofiber has a hollow sheath-core structure with a skin layer having through holes, and specifically, the nanofiber includes a skin layer 3, tubular cavities (hollow structures) 4 formed by surrounding the skin layer and distributed along the axial direction of the fiber, and a plurality of through holes (also called holes) 5 formed on the skin layer and communicating with the tubular cavities through the skin layer. The skin holes extend through the outer wall of the fiber to the inner wall.
In an exemplary embodiment of the present invention, it is preferable that the nanofibers have an average outer diameter of 0.1 to 12 μm, an average inner diameter of 0.05 to 9.5 μm, and an average diameter of the through holes of 0.01 to 5 μm. More preferably, the average outer diameter of the nanofibers is 5 to 9 μm, the average inner diameter is 3 to 6 μm, and the average diameter of the through holes is 1 to 3 μm.
In an exemplary embodiment of the present invention, preferably, the tubular cavity may be a circular tube shape, and the through hole may be a circular through hole.
The nanofiber composite filtering membrane according to an exemplary embodiment of the present invention includes a substrate layer, a nanofiber filtering layer, and a cover layer. The nano filter layer is compounded on the substrate layer, and the covering layer is covered on the nano fiber filter layer. The core filtering part is a nano fiber filtering layer with a single fiber having a hollow structure and a skin layer having a through-hole structure, namely the nano fiber filtering membrane.
The nano filter layer mainly filters particles with small particle size (for example, the particle size is 0.1-2.5 mu m).
In one embodiment of the nanofiber composite filtering membrane of the present invention, the non-woven material may be glass fiber, polypropylene fiber, polyester fiber or polytetrafluoroethylene fiber non-woven fabric. The material is used for filtering particles with larger particle sizes in air. For example, the particle size is 2.5 to 10 μm.
In one embodiment of the nanofiber composite filtration membrane of the present invention, the cover layer may be a polypropylene honeycomb network, a polyester honeycomb network, a metal honeycomb network, a polypropylene fiber nonwoven fabric or a polyester fiber nonwoven fabric. The covering layer is used for fixing the nanofiber filtering layer and preventing the nanofiber filtering layer from being separated from the substrate layer in the using process.
According to the method for manufacturing a nanofiber filtration membrane according to an exemplary embodiment, a nanofiber composite filtration membrane is manufactured using a (coaxial) electrospinning apparatus, including the steps of: dissolving a polymer in a first solvent to obtain a polymer dope, wherein the first solvent is composed of at least two solvents, and the first solvent at least comprises a solvent with a boiling point lower than 60 ℃; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofibers are deposited directly on the receiving electrode plate to form the nanofiber filtration membrane of the present invention.
The method for manufacturing a nanofiber composite filtering membrane according to an exemplary embodiment manufactures a nanofiber composite filtering membrane using an electrospinning device, including the steps of: dissolving a polymer in a first solvent to obtain a polymer dope, wherein the first solvent is composed of at least two solvents, and the first solvent at least comprises a solvent with a boiling point lower than 60 ℃; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofiber is directly deposited on a substrate layer (also called a base layer or a receiving substrate) arranged on a receiving electrode plate to form a nanofiber filtering membrane (nanofiber filtering layer); and laying a covering layer on the surface of the nanofiber filtering membrane to form the nanofiber composite filtering membrane with a sandwich structure of the base layer, the nanofiber filtering layer and the covering layer.
The rapid volatilization of highly volatile solvents during electrospinning not only causes the concentration of the polymer solution to rise rapidly in a short period of time, but also causes the surface temperature of the fiber to decrease rapidly. The rapid volatilization of the solvent can reduce the surface temperature of the material even below 0 ℃. The concentration rise and the temperature decrease act together to enable the polymer solution to cross a double node line or a rotary node line and enter a metastable state or an unstable state from a stable state so as to cause phase separation, a polymer enrichment area and a solvent enrichment area are formed, the polymer enrichment area forms a fiber framework, and holes are formed in the solvent enrichment area.
In an exemplary embodiment of the present invention, the polymer may be polyglycolic acid, polylactic acid, polycaprolactone, polyoxymethylene, polystyrene, polymethylmethacrylate, polyethylene oxide, aliphatic polyester copolymer, polyamide, polycarbonate, polyurethane, polyethylene oxide, polyvinyl alcohol, cellulose acetate, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, or hydroxypropylcellulose.
In an exemplary embodiment of the invention, the inner/outer diameters of the inner tube of the coaxial spinneret are 0.2-2/0.4-2.6 mm, the inner/outer diameters of the outer tube of the coaxial spinneret are 0.5-3/0.7-3.6 mm, the flow rate of the gas or the second solvent in the inner tube of the coaxial spinneret is 0.2-1 mL/h, the flow rate of the polymer spinning solution in the outer tube of the coaxial spinneret is 0.5-1.5 mL/h, the voltage is 7-30 kV, the receiving distance is 5-30 cm, the ambient temperature is 10-40 ℃, the relative humidity is 10-90%, and the mass percentage concentration of the polymer spinning solution is 4-30% in the coaxial electrostatic spinning process.
In an exemplary embodiment of the present invention, the first solvent is at least two of dichloromethane, chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, acetone, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide, acetone, and water.
In an exemplary embodiment of the present invention, the second solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, acetone, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide, acetone, and water. The second solvent may be the same solvent as the first solvent or may be a different solvent.
In an exemplary embodiment of the invention, the first solvent is composed of a low boiling point solvent and a high boiling point solvent, wherein the boiling point of the low boiling point solvent is lower than 60 ℃, the boiling point of the high boiling point solvent is higher than that of the low boiling point solvent, and the volume ratio of the low boiling point solvent to the high boiling point solvent is 1: 1-8: 1. For example, the first solvent is compounded by two of N, N-dimethylacetamide and dichloromethane, or by two of acetone and dichloromethane, or by two of N, N-dimethylformamide and dichloromethane, or by two of N, N-dimethylacetamide and carbon disulfide, or by two of acetone and carbon disulfide.
In another exemplary embodiment of the present invention, a nanofiber composite material with a hollow structure and a through-hole structure on the skin layer is prepared by a coaxial electrospinning method, which comprises the following steps:
(1) adding a certain amount of polymer into a corresponding solvent, and continuously stirring for 5-30 hours by using a magnetic stirring device to form uniform and stable polymer spinning solution with the concentration of 4-30% as a skin layer spinning solution.
(2) And (2) injecting the solution (polymer spinning solution) prepared in the step (1) into an outer tube of a coaxial spinneret, introducing air or a solvent into an inner tube, and performing coaxial electrostatic spinning under certain temperature and humidity conditions, wherein the spun nano-fibers are directly deposited on the surface of a receiving substrate.
(3) And (3) paving a covering layer on the surface of the nanofiber filtering layer spun in the step (2) to form the nanofiber composite filtering material with a sandwich structure of the base layer, the nanofiber filtering layer and the covering layer (as shown in figure 4).
The nanofiber membrane or nanofiber composite membrane of the present invention has a unique structure, and the nanofiber membrane or nanofiber composite membrane has a hollow structure and a skin layer with a through-hole structure is innovatively prepared by an electrospinning technology, and since air filtration air flows through the wall of the tube in a vertical direction (for example, in fig. 4, air flows through a base layer, a nanofiber filtration layer and a cover layer in sequence in a direction vertical to the membrane), the application of the nanofiber with only the hollow structure in the air filtration material cannot improve any of filtration efficiency, air resistance and service life; the nanofiber with the surface porous structure is applied to the air filter material, the specific surface area of the material is only singly increased, compared with the nanofiber with the smooth surface structure, the porous structure slightly improves the filtering efficiency, but has no improvement effect on air resistance and service life. The invention matches the hollow and skin layer with the structure of the through hole, but can generate unexpected chemical reaction, and obtains the nano fiber with innovative structure and brand new and excellent filtering effect.
The nanofiber filtering membrane with the hollow structure and the perforated hole on the skin layer has larger specific surface area, and the path of air passing through the nanofiber filtering membrane is more complicated during filtering, so that the interception efficiency of the nanofiber filtering membrane on particles in the air can be greatly improved, and the filtering efficiency of the filtering material can be improved; during filtering, the air passes through the fiber filtering membrane, besides the pores 2 among the fibers, the air resistance of the fiber filtering membrane can be reduced because the air also has the holes 5 through which the single fiber skin layer penetrates; during filtering, the particulate matter enters the fiber hollow part (namely the tubular cavity) 4 from the hole 5 penetrated by the fiber skin layer, collides with the inner wall of the fiber, and finally settles in the fiber hollow part 4, so that the hollow fiber has the functions of intercepting and storing the particulate matter, the saturated adsorption capacity of the filtering material to the particulate matter is improved, and the service life of the filtering material is prolonged. The application of the nanofiber in the air filtering material achieves a brand new technical effect, the filtering efficiency of the nanofiber is obviously improved, the air resistance is reduced, and more importantly, the service life of the nanofiber is prolonged.
The nanofiber filtration membrane/nanofiber composite filtration membrane and the method for producing the same according to the present invention will be further described with reference to specific examples.
Example 1
Polylactic acid (PLLA) was placed in a vacuum oven at 60 ℃ and dried under vacuum for 10 hours. Dissolving the dried polylactic acid particles in a mixed solvent, wherein the solvent comprises the following components: 1-dichloromethane: 7 (volume ratio), and then placing the mixture on a magnetic stirrer to stir for 10 hours to form a uniform solution, wherein the mass fraction of the solution is 8 percent, and the solution is used as a skin layer spinning solution.
And injecting the skin layer spinning solution coaxially, injecting the skin layer spinning solution into an outer pipe of a coaxial spinneret, introducing air into an inner pipe, and performing coaxial electrostatic spinning at the temperature of 23 ℃ and the humidity of 50%. The spinning process parameters are as follows: the inner tube has a gauge of 1.0/1.2mm (inner diameter/outer diameter) and the outer tube has a gauge of 2.0/2.6mm (inner diameter/outer diameter). The flow rate of the air in the inner tube is 0.5mL/h, the flow rate of the solution in the outer tube is 1.0mL/h, the voltage is 20kV, the receiving distance is 20cm, the receiving base material is polypropylene non-woven fabric, after spinning is completed, the polypropylene non-woven fabric is taken down and dried, and a layer of polypropylene non-woven fabric is covered on the surface of the nanofiber filter layer, so that the nanofiber composite filter membrane is obtained.
The obtained nanofiber is hollow and has a skin layer with through holes, wherein the average outer diameter of the fiber is 2.0 μm, the average inner diameter is 1.4 μm, and the average diameter of the skin layer holes is 0.8 μm. The thickness of the prepared nanofiber filter layer is 0.5 mm.
Example 2
Cellulose Acetate (CA) was placed in a vacuum oven at 60 ℃ and dried under vacuum for 10 hours. Dissolving the dried polylactic acid particles in a mixed solvent, wherein the solvent comprises acetone: 1-dichloromethane: 5 (volume ratio), and then placing the mixture on a magnetic stirrer to stir for 10 hours to form a uniform solution, wherein the mass fraction of the solution is 7 percent, and the solution is used as a skin layer spinning solution.
And injecting the skin layer spinning solution coaxially, injecting the skin layer spinning solution into an outer pipe of a coaxial spinneret, introducing air into an inner pipe, and performing coaxial electrostatic spinning at the temperature of 23 ℃ and the humidity of 50%. The spinning process parameters are as follows: the inner tube has a gauge of 1.0/1.2mm (inner diameter/outer diameter) and the outer tube has a gauge of 2.0/2.6mm (inner diameter/outer diameter). The flow rate of the air in the inner tube is 0.5mL/h, the flow rate of the solution in the outer tube is 1.0mL/h, the voltage is 20kV, the receiving distance is 20cm, the receiving base material is polypropylene non-woven fabric, after spinning is completed, the polypropylene non-woven fabric is taken down and dried, and a layer of polypropylene non-woven fabric is covered on the surface of the nanofiber filter layer, so that the nanofiber composite filter membrane is obtained.
The obtained nanofiber is hollow and has a skin layer with through holes, wherein the average outer diameter of the fiber is 2.0 μm, the average inner diameter is 1.4 μm, and the average diameter of the skin layer holes is 0.6 μm. The thickness of the prepared nanofiber filter layer is 0.5 mm.
Example 3
Polycaprolactone (PCL) was dried in a vacuum oven at 60 ℃ for 10 hours. Dissolving the dried polylactic acid particles in a mixed solvent, wherein the solvent comprises acetone: 1-dichloromethane: 6 (volume ratio), and then placing the mixture on a magnetic stirrer to stir for 10 hours to form a uniform solution, wherein the mass fraction of the solution is 9 percent, and the solution is used as a skin layer spinning solution.
And injecting the skin layer spinning solution coaxially, injecting the skin layer spinning solution into an outer pipe of a coaxial spinneret, introducing air into an inner pipe, and performing coaxial electrostatic spinning at the temperature of 23 ℃ and the humidity of 50%. The spinning process parameters are as follows: the inner tube has a gauge of 1.0/1.2mm (inner diameter/outer diameter) and the outer tube has a gauge of 2.0/2.6mm (inner diameter/outer diameter). The flow rate of the air in the inner tube is 0.5mL/h, the flow rate of the solution in the outer tube is 1.0mL/h, the voltage is 20kV, the receiving distance is 20cm, the receiving base material is glass fiber non-woven fabric, after spinning is completed, the non-woven fabric is taken down and dried, and a layer of polypropylene non-woven fabric is covered on the surface of the nanofiber filter layer, so that the nanofiber composite filter membrane is obtained.
The obtained nanofiber was hollow and had through-holes in the skin layer, wherein the average outer diameter of the fiber was 1.8 μm, the average inner diameter was 1.3 μm, and the average diameter of the holes in the skin layer was 0.7 μm. The thickness of the prepared nanofiber filter layer is 0.5 mm.
In summary, the nanofiber filtration membrane and the nanofiber filtration composite membrane according to the present invention have nanofibers having a hollow structure with a through-hole structure in the skin layer, which can improve filtration efficiency and reduce air resistance while having a longer service life. According to the preparation method of the nanofiber filtering membrane and the nanofiber composite filtering membrane, the nanofiber which is prepared through coaxial electrostatic spinning and has a hollow structure with the surface layer provided with the through holes is introduced into the nanofiber filtering membrane and the nanofiber filtering composite membrane, so that the filtering efficiency of the filtering membrane is improved, the air resistance is reduced, and meanwhile, the service life is prolonged. The air filter has wide application value in the field of air filtration, and has great application prospect in products such as air purifiers, automobile filter elements, masks and the like.
While the present invention has been described above in connection with the accompanying drawings and exemplary embodiments, it will be apparent to those of ordinary skill in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.
Claims (4)
1. A preparation method of a nano fiber filtering membrane or a nano fiber composite filtering membrane is characterized in that the preparation method of the nano fiber filtering membrane or the nano fiber composite filtering membrane adopts electrostatic spinning equipment to prepare the nano fiber filtering membrane or the nano fiber composite filtering membrane,
the preparation method of the nanofiber filtering membrane comprises the following steps: dissolving a polymer in a first solvent to obtain a polymer spinning solution, wherein the first solvent is two of chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide and water, and consists of a low-boiling-point solvent and a high-boiling-point solvent, the boiling point of the low-boiling-point solvent is lower than 60 ℃, the boiling point of the high-boiling-point solvent is higher than that of the low-boiling-point solvent, and the volume ratio of the low-boiling-point solvent to the high-boiling-point solvent is 1: 1-8: 1; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofiber is directly deposited on a receiving electrode plate to form a nanofiber filtering membrane, wherein the nanofiber filtering membrane is a filtering structure formed by nanofiber, and the nanofiber comprises: a skin layer; a tubular cavity formed by the skin layer and distributed along the axial direction of the fiber; and a plurality of through holes formed on the cortex and communicated with the tubular cavity through the cortex, wherein the average outer diameter of the nanofibers is 0.1-9 μm, the average inner diameter of the nanofibers is 0.05-3 μm, the average diameter of the through holes is 0.01-1 μm, and the thickness of the nanofiber membrane is 0.5-5 mm;
the preparation method of the nanofiber composite filtering membrane comprises the following steps: dissolving a polymer in a first solvent to obtain a polymer spinning solution, wherein the first solvent is two of chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide and water, and consists of a low-boiling-point solvent and a high-boiling-point solvent, the boiling point of the low-boiling-point solvent is lower than 60 ℃, the boiling point of the high-boiling-point solvent is higher than that of the low-boiling-point solvent, and the volume ratio of the low-boiling-point solvent to the high-boiling-point solvent is 1: 1-8: 1; injecting the polymer spinning solution into an outer tube of a coaxial spinneret, and feeding gas or a second solvent into an inner tube of the coaxial spinneret to carry out coaxial electrostatic spinning; the spun nanofiber is directly deposited on the substrate layer to form a nanofiber filter layer; the nanofiber filter layer surface is spread one deck overburden, forms nanofiber composite filtration membrane, nanofiber composite filtration membrane includes the stratum basale, compounds and is in nanofiber filter layer and the cover on the stratum basale are in overburden on the nanofiber filter layer, stratum basale, nanofiber filter layer, overburden form sandwich structure, the nanofiber filter layer is nanofiber filter membrane, nanofiber filter membrane is the filtration by nanofiber formation, nanofiber includes: a skin layer; a tubular cavity formed by the skin layer and distributed along the axial direction of the fiber; and a plurality of through holes formed on the skin layer and communicated with the tubular cavity through the skin layer, wherein the average outer diameter of the nanofibers is 0.1-9 μm, the average inner diameter of the nanofibers is 0.05-3 μm, the average diameter of the through holes is 0.01-1 μm, and the thickness of the nanofiber membrane is 0.5-5 mm,
the inner diameter of an inner tube of the coaxial spinneret is 0.2-2 mm, the outer diameter of the inner tube of the coaxial spinneret is 0.4-2.6 mm, the inner diameter of an outer tube of the coaxial spinneret is 0.5-3 mm, the flow rate of gas or a second solvent in the inner tube of the coaxial spinneret is 0.2-1 mL/h, the flow rate of a polymer spinning solution in the outer tube of the coaxial spinneret is 0.5-1.5 mL/h, the voltage is 7-30 kV, the receiving distance is 5-30 cm, the environment temperature is 10-40 ℃, the relative humidity is 10-90% and the mass percentage concentration of the polymer spinning solution is 4-30% in the coaxial electrostatic spinning process.
2. The method of preparing a nanofiber filtration membrane or a nanofiber composite filtration membrane according to claim 1, wherein the polymer is polyglycolic acid, polylactic acid, polycaprolactone, polyoxymethylene, polystyrene, polymethylmethacrylate, polyethylene oxide, aliphatic polyester copolymer, polyamide, polycarbonate, polyurethane, polyethylene oxide, polyvinyl alcohol, cellulose acetate, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, or hydroxypropylcellulose.
3. The nanofiber filtration membrane or nanofiber composite filtration membrane manufacturing method according to claim 1, wherein the second solvent is at least one of dichloromethane, chloroform, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, acetone, isopropanol, formic acid, acetic acid, methanol, ethanol, butanol, carbon disulfide, acetone, and water.
4. The method of claim 1, wherein the first solvent is formulated from N, N-dimethylacetamide and carbon disulfide.
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| CN112755800B (en) * | 2020-12-03 | 2022-01-07 | 华中科技大学 | Nanofiber membrane and preparation method thereof, nanofiber filtering membrane and preparation method thereof |
| TWI800080B (en) * | 2021-11-05 | 2023-04-21 | 亞格生技股份有限公司 | Method for making nanofiber film |
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