CN113564809A - Nonwoven fabric and liquid separation membrane - Google Patents

Nonwoven fabric and liquid separation membrane Download PDF

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Publication number
CN113564809A
CN113564809A CN202111030822.0A CN202111030822A CN113564809A CN 113564809 A CN113564809 A CN 113564809A CN 202111030822 A CN202111030822 A CN 202111030822A CN 113564809 A CN113564809 A CN 113564809A
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Prior art keywords
fiber
fibers
nonwoven fabric
ratio
layer
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CN202111030822.0A
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CN113564809B (en
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陈莉
林陆菁
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Shenzhen Senior Technology Material Co Ltd
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Shenzhen Senior Technology Material Co Ltd
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    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/559—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving the fibres being within layered webs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/04—Glass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/36—Polytetrafluoroethene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/38—Polyalkenylalcohols; Polyalkenylesters; Polyalkenylethers; Polyalkenylaldehydes; Polyalkenylketones; Polyalkenylacetals; Polyalkenylketals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/48—Polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
    • B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
    • B01D71/64—Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/541—Composite fibres, e.g. sheath-core, sea-island or side-by-side; Mixed fibres
    • D04H1/5418—Mixed fibres, e.g. at least two chemically different fibres or fibre blends
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/542—Adhesive fibres
    • D04H1/544—Olefin series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/542—Adhesive fibres
    • D04H1/549—Polyamides
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/542—Adhesive fibres
    • D04H1/55—Polyesters

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Laminated Bodies (AREA)

Abstract

A non-woven fabric and a liquid separation membrane belong to the technical field of non-woven fabrics. The non-woven fabrics includes two at least layers of fibrous layer, the thickness of non-woven fabrics is 50 ~ 110 mu m, fibre in the fibrous layer includes trunk fiber and the bonding fiber who is used for bonding the trunk fiber, the ratio of first trunk fiber in the fibrous layer and first bonding fiber's total weight and second trunk fiber and second bonding fiber's total weight is first ratio, along the thickness direction of non-woven fabrics, the first ratio gradient increase of each layer fibrous layer, and in the one deck fibrous layer that first ratio is the biggest, the total mass fraction of first trunk fiber and first bonding fiber is not less than 50%. The non-woven fabric can reduce the generation of pore defects, reduce the overall thickness of the liquid separation membrane and improve the separation efficiency and water flux of the liquid separation membrane.

Description

Nonwoven fabric and liquid separation membrane
Technical Field
The application relates to the technical field of non-woven fabrics, particularly, relate to a non-woven fabrics and liquid separation membrane.
Background
The liquid separation membrane technology is mainly and widely applied to the fields of sewage treatment, feed water purification, seawater desalination, pure water preparation and the like at present.
Taking a reverse osmosis membrane as an example, a reverse osmosis membrane generally consists of three layers: the membrane comprises a polyamide ultrathin layer, a polysulfone porous layer and a polyester reinforced non-woven fabric, wherein the polyester reinforced non-woven fabric mainly provides the supporting strength of a membrane structure, the polysulfone porous layer has high porosity and rigidity and can resist densification under the membrane operation condition, and the polyamide ultrathin layer has high water flux, desalination rate and chemical stability. The polyamide ultrathin layer is a functional layer which really plays a role in separation in the water treatment process, and the polyamide ultrathin layer cannot bear high hydraulic pressure in the separation process when being used alone due to extremely low mechanical strength and cannot be independently prepared into a film, so that the polyamide ultrathin layer can be compounded on a supporting layer to form the film.
In order to ensure high liquid flux and high filtering performance of the liquid separation membrane, the pore diameter and the distribution of the functional layer are required to be high, and therefore, the non-woven fabric serving as the supporting layer also has to control the pore diameter distribution, wherein the larger pore diameter is beneficial to improving the water flux of the liquid separation membrane, but also increases the risk that a coating layer of the liquid separation membrane has pore defects.
Disclosure of Invention
The application provides a non-woven fabrics and liquid separation membrane, this non-woven fabrics can reduce the production of hole defect to need not a large amount of coatings and can obtain continuous coating layer at one of them surface of non-woven fabrics, can reduce liquid separation membrane's whole thickness, and improve liquid separation membrane's separation efficiency and water flux.
The embodiment of the application is realized as follows:
in a first aspect, an embodiment of the present application provides a nonwoven fabric, which includes at least two fiber layers, where the thickness of the nonwoven fabric is 50 to 110 μm, fibers in the fiber layers include trunk fibers and bonding fibers for bonding the trunk fibers, and a melting point or a softening point of the trunk fibers is greater than a melting point or a softening point of the bonding fibers;
the trunk fibers comprise first trunk fibers with the diameter less than 5.5 mu m and second trunk fibers with the diameter more than or equal to 5.5 mu m;
the bonding fibers comprise first bonding fibers with the diameter less than 6 mu m and second bonding fibers with the diameter more than or equal to 6 mu m;
the ratio of the total weight of the first main fibers and the first bonding fibers in the fiber layers to the total weight of the second main fibers and the second bonding fibers is a first ratio, the first ratio of each fiber layer is sequentially increased along the thickness direction of the non-woven fabric, and the total mass fraction of the first main fibers and the first bonding fibers in the fiber layer with the largest first ratio is not less than 50%.
In a second aspect, embodiments of the present application provide a liquid separation membrane, where the liquid separation membrane includes the nonwoven fabric of the first aspect, a surface of the one fiber layer with the largest first ratio has a coating layer, and a surface of the one fiber layer with the smallest first ratio is a non-coated surface.
The embodiment of the application at least comprises the following beneficial effects:
the thickness of the non-woven fabric is 50-110 mu m, and the non-woven fabric with the thickness is mainly suitable for a supporting layer of the liquid separation membrane. Along the thickness direction of non-woven fabrics, the ratio of the total weight of first trunk fibre and first bonding fiber in each fibrous layer to the total weight of second trunk fibre and second bonding fiber increases in proper order, then the proportion of the fibre that the diameter is littleer in the fibrous layer that first ratio is great, cover the macropore that fills that the fibrous layer that first ratio is less formed more easily, form relatively smooth transition between each fibrous layer, obtain the multilayer fibrous layer structure that the pore gradient changes, the aperture that the fibrous layer that first ratio is great formed is less, the aperture that the fibrous layer that first ratio is less formed is great. The structure with the pore gradient change is beneficial to reducing the permeation resistance of fluid and improving the transmission capability of the fluid in the non-woven fabric, thereby being beneficial to improving the water flux of the liquid separation membrane.
The surface of the fiber layer with the largest first ratio is a coating surface, the ratio of the first main fiber and the first bonding fiber contained in the fiber layer is the largest, and in the fiber layer, the total mass fraction of the first main fiber and the first bonding fiber is not less than 50%, so that the pore diameter of the fiber layer is small, the effective area of contact and compounding of the coating material and the fiber layer can be remarkably increased, a continuous coating layer can be formed by coating a small amount of the coating material, the overall thickness of the liquid separation membrane can be reduced, and the separation efficiency of the liquid separation membrane can be improved. And the smaller aperture is beneficial to preventing the coating liquid from permeating to the other side of the non-woven fabric through the aperture, thereby reducing the possibility of generating defects such as pinholes and the like due to the leakage of the coating layer.
The surface of the fiber layer with the minimum first ratio is a non-coating surface, and the larger pore diameter of the fiber layer also ensures that air entrained in the non-woven fabric can escape more quickly in the phase separation process, so that the problem that air is remained and enters the coating layer to cause air bubbles to finally form large pore defects on the coating layer can be avoided.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The nonwoven fabric and the liquid separation membrane according to the examples of the present application will be specifically described below:
in a first aspect, the present application provides a nonwoven fabric, which includes at least two fiber layers, the thickness of the nonwoven fabric is 50 to 110 μm, the fibers in the fiber layers include main fibers and bonding fibers for bonding the main fibers, and the melting point or softening point of the main fibers is greater than the melting point or softening point of the bonding fibers.
The non-woven fabric with the thickness of 50-110 μm is mainly suitable for the support layer of the liquid separation membrane, and optionally, the thickness of the non-woven fabric is in a range of any one or any two of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm and 110 μm. When the fiber layer is manufactured, the melting point or the softening point of the main fibers is larger than that of the bonding fibers, so that the main fibers are kept in a fiber shape when the bonding fibers are softened or melted under a certain temperature condition, and the main fibers are combined together to form the fiber layer through the action of the bonding fibers.
The preparation of the non-woven fabric can be realized by respectively preparing single-layer fiber layers and then performing hot-pressing compounding on the multiple fiber layers to form the non-woven fabric.
It is understood that the melting or softening point of the primary fibers being greater than the melting or softening point of the binder fibers includes the following: (1) the melting point of the main fiber is greater than that of the bonding fiber; (2) the melting point of the main fiber is larger than the softening point of the bonding fiber; (3) the softening point of the trunk fiber is larger than that of the bonding fiber; (4) the softening point of the trunk fibers is greater than the melting point of the binder fibers.
In some embodiments, the trunk fibers comprise at least one of polyester fibers, polyolefin fibers, Polyamide (PA) fibers, polyimide fibers, Polytetrafluoroethylene (PTFE) fibers, polyvinyl alcohol fibers, polyvinylidene fluoride (PVDF) fibers, polyphenylene sulfide (PPS) fibers, Polyetheretherketone (PEEK) fibers, Polyacrylonitrile (PAN) fibers, polycarbonate fibers, polyacrylonitrile fibers, aramid fibers, glass fibers, ceramic fibers, oxide fibers, boride fibers, and nitride fibers.
Optionally, the polyester fibers comprise at least one of polyethylene terephthalate (PET) fibers and polybutylene terephthalate (PBT) fibers.
Optionally, the polyolefin fibers comprise at least one of Polyethylene (PE) fibers, polypropylene (PP) fibers, polyvinyl chloride (PVC) fibers, and ES fibers. Optionally, the polyamide fiber comprises PA 66.
The main fibers in the respective fiber layers may be the same type of fibers or different types of fibers.
In some embodiments, the binding fibers comprise at least one of polyethylene terephthalate fibers, polybutylene terephthalate fibers, alkali soluble polyester (COPET), polyolefin fibers, copolyester, and copolyamides. Illustratively, the polyethylene terephthalate fiber in the binder fiber is an undrawn polyethylene terephthalate fiber, and the polybutylene terephthalate fiber is an undrawn polybutylene terephthalate fiber. Among them, the non-stretched polyethylene terephthalate fiber has a lower softening point temperature than that of the conventional polyethylene terephthalate fiber, and the non-stretched polybutylene terephthalate fiber has a lower softening point temperature than that of the conventional polybutylene terephthalate fiber.
The bonding fibers in the respective fiber layers may be the same type of fibers or different types of fibers.
The trunk fibers comprise first trunk fibers with the diameter less than 5.5 mu m and second trunk fibers with the diameter more than or equal to 5.5 mu m; the bonding fibers comprise first bonding fibers with the diameter less than 6 mu m and second bonding fibers with the diameter more than or equal to 6 mu m.
Illustratively, the diameter of the first trunk fiber is any one of 5.4 μm, 5.2 μm, 5 μm, 5.2 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm, 1 μm, 0.5 μm, and 0.1 μm or a range between any two.
The ratio of the total weight of the first main fibers and the first bonding fibers in the fiber layers to the total weight of the second main fibers and the second bonding fibers is a first ratio, the first ratio gradient of each fiber layer is increased along the thickness direction of the non-woven fabric, and the total mass fraction of the first main fibers and the first bonding fibers in the fiber layer with the largest first ratio is not less than 50%.
Wherein the nonwoven fabric has a first side and a second side opposite to each other, and in one embodiment, the surface of the fiber layer with the smallest first ratio is the first side of the nonwoven fabric, and the gradient of the first ratio of the fiber layers increases when the surface of the nonwoven fabric is directed from the first side to the second side.
In another embodiment, the surface of the layer of fiber layer with the smallest first ratio is the second side of the nonwoven, and the first ratio gradient of the layers of fiber layer increases when the layer of fiber layer is directed from the second side to the first side of the nonwoven.
Along the thickness direction of non-woven fabrics, the ratio (first ratio) gradient increase of the total weight of first trunk fibre and first bonding fiber in each fibrous layer and the total weight of second trunk fibre and second bonding fiber for the bulk density gradient of fibrous layer increases, then the fibre in the fibrous layer that bulk density is great can cover the macropore that the fibrous layer that bulk density is less formed and fill, the pore difference between each fibrous layer forms relatively smooth transition, obtain the multilayer fibrous layer structure of pore gradient change, the aperture that the fibrous layer that bulk density is great formed is less, the aperture that the fibrous layer that bulk density is less formed is great. Compared with the non-woven fabric with randomly distributed pores, the pore gradient structure provided by the embodiment of the application is favorable for reducing the permeation resistance of fluid and improving the transmission capability of the fluid in the non-woven fabric, thereby being favorable for improving the water flux of the liquid separation membrane. In addition, as the gradient of the first ratio decreases, the pore diameter of each fiber layer increases in the thickness direction of the nonwoven fabric, and the strength also increases.
When one fiber layer with the largest first ratio is used for coating the coating material, the ratio of the first main fibers and the first bonding fibers contained in the fiber layer is largest, and the total mass fraction of the first main fibers and the first bonding fibers in the fiber layer is not less than 50%, so that the fiber layer has small aperture and large aperture specific surface area, the effective area of the contact composite of the coating material and the fiber layer can be remarkably increased, and a continuous coating layer can be formed by coating a small amount of the coating material. And the smaller aperture is beneficial to preventing the coating liquid from permeating to the other side of the non-woven fabric through the aperture, thereby reducing the possibility of generating defects such as pinholes and the like due to the leakage of the coating layer.
When the surface of the layer of the fiber layer with the minimum first ratio is not coated with the coating material, the larger aperture of the layer of the fiber layer can also ensure that air entrained in the non-woven fabric can escape more quickly in the phase separation process, so that the defect that air bubbles finally form large holes on the coating layer due to the fact that air residues enter the coating layer can be avoided.
In some embodiments, the second trunk fibers have a diameter of 5.5 to 15 μm and the second binder fibers have a diameter of 6 to 20 μm. Illustratively, the diameter of the second trunk fibers is any one of 5.5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm or a range between any two. Illustratively, the diameter of the second binding fibers is any one of 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, and 20 μm or a range between any two.
Optionally, the length of the trunk fibers and the bonding fibers is 1-10 mm, such as any one or a range between any two of 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, and 10 mm.
In some embodiments, the mass fraction of the trunk fibers is 60 to 80 wt%, and the mass fraction of the binder fibers is 20 to 40 wt%. The main fiber and the bonding fiber are added according to the proportion range, so that the non-woven fabric can have high strength.
Optionally, the mass fraction of the trunk fibers is any one of 60 wt%, 65 wt%, 70 wt%, 75 wt%, and 80 wt%, or a range between any two.
Optionally, the mass fraction of binding fibers is any one of 20 wt%, 25 wt%, 30 wt%, 35 wt%, and 40 wt%, or a range between any two.
In some embodiments, the total mass fraction of the second trunk fibers and the second binder fibers in the first least valued one fiber layer is greater than 50%.
In other embodiments, the total mass fraction of the second main fibers and the second binder fibers in one fiber layer having the smallest first ratio may be not more than 50%.
Optionally, in the single-layer fiber layer, the mass ratio of the first trunk fibers to the second trunk fibers is the same as the mass ratio of the first binder fibers to the second binder fibers. It will be appreciated that the mass ratio of the first and second trunk fibers to the mass ratio of the first and second binder fibers in a single fiber layer may also be different.
In some embodiments, the nonwoven fabric has an average pore size of 10 μm or less and a ratio of the largest pore size to the average pore size in the nonwoven fabric is a second ratio, the second ratio being 1 to 12.
When one fiber layer with the largest first ratio is used for coating the coating material, if the average pore diameter is more than 10 μm, the coating liquid is easy to permeate to the other side of the non-woven fabric through pores, and through holes are generated on the coating layer; when the average pore diameter is too small, the coating liquid hardly penetrates deeply into the surface of the nonwoven fabric, and the bonding strength of the coating layer to the nonwoven fabric tends to be insufficient. Optionally, the nonwoven fabric has an average pore size of 1 to 5 μm, for example, in a range of any one or between any two of 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm.
In addition, when the ratio of the maximum aperture to the average aperture of the non-woven fabric is greater than 12, the air that easily causes the pore of the non-woven fabric to carry is not uniform with the rate of water exchange in the phase separation process, will influence the homogeneity that the coating layer solidifies the membrane, in the non-woven fabric of this application embodiment, the ratio of maximum aperture to average aperture is 1 ~ 12, can guarantee that the non-woven fabric has more even aperture distribution, increases the homogeneity that the coating layer solidifies the membrane. Optionally, the ratio of the maximum pore size to the average pore size in the nonwoven fabric is in a range of any one or between any two of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12.
Further, the inventors of the present application found in their studies that when the non-woven fabric had an areal density of less than 60g/m2Then as a liquid separation membraneThe nonwoven fabric of the support layer hardly maintains a sufficient tensile strength, particularly a transverse tensile strength, the liquid separation membrane cannot withstand a high hydraulic pressure, and even breaks, and the coating liquid is relatively easily permeated from one side of the nonwoven fabric to the other side. Under the condition of constant density, when the surface density of the non-woven fabric is more than 100g/m2In the meantime, the thickness of the non-woven fabric is relatively thick, so that a sufficient filtering area cannot be achieved when the liquid separation membrane module of a certain specification is assembled. Thus, in some embodiments of the present application, the non-woven fabric has an areal density of 60 to 100g/m2。
In some embodiments, the nonwoven fabric has a density of 0.50 to 0.95g/m3。
When the fiber layer with the largest ratio of the total weight of the first main fibers and the first bonding fibers to the total weight of the second main fibers and the second bonding fibers is used for coating the coating material, the density of the non-woven fabric is less than 0.50g/m3In the process, the coating liquid is excessively permeated on the surface of the non-woven fabric and is easy to permeate to the other side of the non-woven fabric; when the density is more than 0.95g/m3In this case, the coating liquid does not penetrate deeply into the surface of the nonwoven fabric, and the adhesion of the coating layer to the nonwoven fabric is insufficient.
Illustratively, the density of the nonwoven fabric is 0.50g/m3、0.55g/m3、0.60g/m3、0.65g/m3、0.70g/m3、0.75g/m3、0.80g/m3、0.85g/m3、0.90g/m3And 0.95g/m3Or any range therebetween.
In some embodiments, the nonwoven fabric has a transverse direction tensile strength of >35N/15mm and a ratio of longitudinal tensile strength to transverse direction tensile strength of 1.05 to 4.
The inventor of the present application has found that if the nonwoven fabric has a transverse tensile strength of less than 35N/15mm, the nonwoven fabric is too weak to be coated on a production line, and is likely to tear or break. In addition, if the machine direction tensile strength/cross direction tensile strength ratio is greater than 4, the nonwoven fabric is liable to wrinkle in the machine direction, which may be associated with heat shrinkage in the cross direction during hot calendering.
In some embodiments, the nonwoven fabric has an air permeability value of 0.5 to 7.0cc/cm2/sec。
When the air permeability of the nonwoven fabric is less than 0.5cc/cm2At/sec, a large hydraulic pressure needs to be applied in the liquid separation membrane filtration process, which makes the filtration efficiency low. When the air permeability of the nonwoven fabric is larger than 7.0cc/cm2At/sec, the filtration action is reduced and it is difficult to obtain good filtration performance.
In a second aspect, embodiments of the present application further provide a liquid separation membrane, where the liquid separation membrane includes the nonwoven fabric of the first aspect, a surface of the one fiber layer with the largest first ratio has a coating layer, and a surface of the one fiber layer with the smallest first ratio is a non-coated surface.
The liquid separation membrane of this application embodiment includes above-mentioned non-woven fabrics, and the setting of this non-woven fabrics does benefit to the osmotic resistance who reduces fluid, improves the transmission ability of fluid in the non-woven fabrics is inside, consequently helps improving liquid separation membrane's water flux, and can reduce the possibility that the hole defect produced.
The nonwoven fabric and the liquid separation membrane of the present application will be described in further detail with reference to examples.
Example 1
This embodiment provides a non-woven fabrics, non-woven fabrics include two-layer fibrous layer, and the concrete setting of every layer of fibrous layer is as follows:
Figure BDA0003244190790000091
Figure BDA0003244190790000101
wherein, the PET fiber that trunk fibre adopted is conventional PET fiber, and the PET fiber that bonding fiber adopted is not tensile PET fiber.
The preparation method of the non-woven fabric comprises the following steps:
and (3) papermaking of the non-woven base paper by using an inclined wire paper machine to obtain a fiber layer, and hot-pressing and compounding the fiber layer to obtain the non-woven fabric.
Example 2
This example provides a nonwoven fabric prepared in the same manner as in example 1. The non-woven fabric of this embodiment includes two fibrous layers, and the specific setting of every fibrous layer is as follows:
Figure BDA0003244190790000102
example 3
This example provides a nonwoven fabric prepared in the same manner as in example 1. The non-woven fabric of the embodiment comprises three fiber layers, and the specific arrangement of each fiber layer is as follows:
Figure BDA0003244190790000111
example 4
This example provides a nonwoven fabric prepared in the same manner as in example 1. The non-woven fabric of this embodiment includes four fibrous layers, and the concrete setting of every fibrous layer is as follows:
Figure BDA0003244190790000112
Figure BDA0003244190790000121
example 5
This example provides a nonwoven fabric prepared in the same manner as in example 1. The non-woven fabric of this embodiment includes two fibrous layers, and the specific setting of every fibrous layer is as follows:
Figure BDA0003244190790000122
comparative example 1
This comparative example provides a nonwoven fabric prepared in the same manner as in example 1. The nonwoven fabric of this comparative example comprises three fibrous layers, each fibrous layer being specifically set up as follows:
Figure BDA0003244190790000123
Figure BDA0003244190790000131
comparative example 2
This comparative example provides a nonwoven fabric prepared in the same manner as in example 1. The nonwoven fabric of this comparative example includes four fiber layers, each of which is specifically set as follows:
Figure BDA0003244190790000132
Figure BDA0003244190790000141
comparative example 3
This comparative example provides a non-woven fabric, and this non-woven fabric includes a fibrous layer, and the specific setting of fibrous layer is as follows:
Figure BDA0003244190790000142
wherein, the PET fiber that trunk fibre adopted is conventional PET fiber, and the PET fiber that bonding fiber adopted is not tensile PET fiber.
Comparative example 4
This comparative example provides a nonwoven fabric prepared in the same manner as in example 1. The non-woven fabric of this embodiment includes two fibrous layers, and the specific setting of every fibrous layer is as follows:
Figure BDA0003244190790000143
Figure BDA0003244190790000151
test example 1
The nonwoven fabrics of examples 1 to 5 and comparative examples 1 to 4 were each cut into a size of a4, a polysulfone layer was applied to the outer surface of the first layer of a part of the nonwoven fabric, the coated nonwoven fabric was immersed in water to undergo phase separation, and the resultant was taken out after 10 minutes and dried at room temperature to obtain a composite nonwoven fabric. Wherein the coating liquid had a composition of 7.5 wt% of polysulfone and 92.5 w% of N-methylpyrrolidone.
The nonwoven fabrics of examples 1 to 5 and comparative examples 1 to 4 were tested for the area density, thickness, density, air permeability, pore diameter and tensile strength, wherein the density is the area density/thickness, and the composite nonwoven fabrics of examples 1 to 5 and comparative examples 1 to 4 were tested for the number of pinholes, penetration of coating liquid and coating thickness, and the results are reported in table 1.
Wherein, the surface density is detected according to the method of GB/T451.2-2002; the thickness is detected according to the method of GB/T451.3-2002; the air permeability is detected according to the method of GB/T24218.15-2018; the aperture is detected according to the method of GB/T32361-2015; the intensity was measured according to the method of GB/T12914-2008.
TABLE 1 test results for nonwoven and composite nonwoven fabrics
Figure BDA0003244190790000152
Figure BDA0003244190790000161
As can be seen from the results in table 1, the composite nonwoven fabrics according to examples 1 to 5 of the present application have a small number of pin holes, and the coating liquid does not penetrate into the back surface of the nonwoven fabric.
In the nonwoven fabric of comparative example 3 and comparative example 1, along the direction from the first layer to the third layer, the ratio of the total content of the first main fibers and the first binder fibers of example 3 to the total content of the second main fibers and the second binder fibers is sequentially decreased, while the ratio of the total content of the first main fibers and the first binder fibers of comparative example 1 to the total content of the second main fibers and the second binder fibers is increased and then decreased, and it can be found from the results of experiments that the nonwoven fabric corresponding to example 3 has higher strength, and the composite nonwoven fabric corresponding to example 3 has no pinholes and has no occurrence of the situation that the coating solution penetrates to the back surface of the nonwoven fabric during the coating process, and the thickness of the coating layer is thinner.
In the nonwoven fabric of comparative example 4 and the nonwoven fabric of comparative example 2, along the direction from the first layer to the third layer, the ratio of the total content of the first main fibers and the first binder fibers in example 4 to the total content of the second main fibers and the second binder fibers is sequentially decreased, while the ratio of the total content of the first main fibers and the first binder fibers in comparative example 2 to the total content of the second main fibers and the second binder fibers is decreased and then increased, and the results of experiments show that the nonwoven fabric corresponding to example 4 has smaller pore size and higher strength, and the composite nonwoven fabric corresponding to example 4 has no pinholes and has no coating liquid permeating into the back surface of the nonwoven fabric, and the thickness of the coating layer is thinner than the composite nonwoven fabric corresponding to comparative example 2.
Through example 2 and comparative example 4, it is found that in comparative example 4, the total content of the first main fibers and the first binder fibers of the first fibrous layer and the second fibrous layer is less than 50 wt%, in example 2, the total content of the first main fibers and the first binder fibers of the first fibrous layer is less than 50%, and the total content of the first main fibers and the first binder fibers of the second fibrous layer is equal to 50%, and it can be found from the combination experiment result that the composite nonwoven fabric corresponding to example 2 has no pinholes, no coating liquid penetrates to the back surface of the nonwoven fabric, and the thickness of the coating layer is thinner, compared with the composite nonwoven fabric corresponding to comparative example 4.
The non-woven fabric of the embodiment of the application is described, and the requirements that the first ratio is increased in sequence along the thickness direction of the non-woven fabric, and the first ratio is the largest in one fiber layer, when the total mass fraction of the first main fibers and the first bonding fibers is not less than 50%, a continuous coating layer can be formed even if the thin coating layer is coated, the coating liquid can be prevented from permeating the back surface of the non-woven fabric, and the generation of hole defects can be reduced.
Comparing the nonwoven fabrics of example 1 and comparative example 3, it can be seen from the results of table 1 that comparative example 3 has only one fiber layer, which can be regarded as a multi-layered fiber layer having the same fiber composition, and the composite nonwoven fabric corresponding to comparative example 3 has pinholes.
The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A non-woven fabric is characterized by comprising at least two fiber layers, wherein the thickness of the non-woven fabric is 50-110 microns, fibers in the fiber layers comprise main fibers and bonding fibers for bonding the main fibers, and the melting point or the softening point of the main fibers is larger than that of the bonding fibers;
the trunk fibers comprise first trunk fibers with the diameter less than 5.5 mu m and second trunk fibers with the diameter more than or equal to 5.5 mu m;
the bonding fibers comprise first bonding fibers with the diameter less than 6 mu m and second bonding fibers with the diameter more than or equal to 6 mu m;
the ratio of the total weight of the first trunk fibers and the first bonding fibers to the total weight of the second trunk fibers and the second bonding fibers in the fiber layer is a first ratio; along the thickness direction of non-woven fabrics, the first ratio gradient of each layer of fibrous layer increases, and in the one layer of fibrous layer that first ratio is the biggest, the total mass fraction of first trunk fibre with first bonding fiber is not less than 50%.
2. The nonwoven fabric of claim 1, wherein the diameter of the second main fibers is 5.5 to 15 μm, and the diameter of the second binder fibers is 6 to 20 μm.
3. The nonwoven fabric according to claim 1, wherein the mass fraction of the main fibers is 60 to 80 wt%, and the mass fraction of the binder fibers is 20 to 40 wt%.
4. The nonwoven fabric of any of claims 1 to 3, wherein the nonwoven fabric has an average pore size of 10 μm or less, and the ratio of the maximum pore size to the average pore size in the nonwoven fabric is a second ratio, the second ratio being 1 to 12.
5. The nonwoven fabric according to any of claims 1 to 3, wherein the nonwoven fabric has an areal density of 60 to 100g/m2(ii) a Optionally, the density of the non-woven fabric is 0.50-0.95 g/m3。
6. The nonwoven fabric according to any one of claims 1 to 3, wherein the nonwoven fabric has an air permeability value of 0.5 to 7.0cc/cm2/sec。
7. The nonwoven fabric of any of claims 1 to 3, wherein the nonwoven fabric has a transverse tensile strength >35N/15mm and a ratio of longitudinal tensile strength to transverse tensile strength of 1.05 to 4.
8. The nonwoven fabric according to any of claims 1 to 3, wherein the total mass fraction of the second main fibers and the second binder fibers in the one fiber layer with the smallest first ratio is more than 50%;
optionally, in the fiber layer, a mass ratio of the first trunk fiber to the second trunk fiber is the same as a mass ratio of the first binder fiber to the second binder fiber.
9. The nonwoven fabric according to any one of claims 1 to 3, wherein the main fiber comprises at least one of polyester fiber, polyolefin fiber, polyamide fiber, polyimide fiber, polytetrafluoroethylene fiber, polyvinyl alcohol fiber, polyvinylidene fluoride fiber, polyphenylene sulfide fiber, polyether ether ketone fiber, polyacrylonitrile fiber, polycarbonate fiber, polyacrylonitrile fiber, aramid fiber, glass fiber, ceramic fiber, oxide fiber, boride fiber, and nitride fiber;
optionally, the bonding fibers comprise at least one of polyethylene terephthalate fibers, polybutylene terephthalate fibers, alkali soluble polyester (COPET), polyolefin fibers, copolyester, and copolyamide.
10. A liquid separation membrane comprising the nonwoven fabric according to any one of claims 1 to 9, wherein the surface of the fiber layer having the largest first ratio has a coating layer, and the surface of the fiber layer having the smallest first ratio is a non-coated surface.
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CN111816824A (en) * 2020-06-11 2020-10-23 深圳市星源材质科技股份有限公司 Non-woven fabric used as lithium ion battery diaphragm base film, diaphragm and lithium ion battery
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CN103816818A (en) * 2014-03-07 2014-05-28 浙江大学 Super-hydrophilic and gradient hole structured hollow fiber membrane
CN105999852A (en) * 2016-06-02 2016-10-12 河北科技大学 Microbead/nano-fiber composite air filtration material with gradient structure and preparation method thereof
CN109666172A (en) * 2018-12-25 2019-04-23 清华大学 A kind of gradient-structure polymer nanocomposites and the preparation method and application thereof
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