Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/10—Supported membranes; Membrane supports
  • B01D69/107—Organic support material
  • B01D69/1071—Woven, non-woven or net mesh
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D39/00—Filtering material for liquid or gaseous fluids
  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
  • B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
  • B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
• • 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
  • B01D67/0004—Organic membrane manufacture by agglomeration of particles
  • B01D67/00042—Organic membrane manufacture by agglomeration of particles by deposition of fibres, nanofibres or nanofibrils
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/06—Flat membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
• • 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
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
• • 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
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/10—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
• • 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
  • B32B5/022—Non-woven fabric
• • 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
  • B32B5/22—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 the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/24—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 the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
  • B32B5/26—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 the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it also being fibrous or filamentary
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • 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
  • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
  • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
  • D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning
• • 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
• • 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
  • B01D2239/0668—The layers being joined by heat or melt-bonding
• • 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
  • B01D2239/12—Special parameters characterising the filtering material
  • B01D2239/1291—Other parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2323/00—Details relating to membrane preparation
  • B01D2323/39—Electrospinning
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/02—Details relating to pores or porosity of the membranes
  • B01D2325/0281—Fibril, or microfibril structures
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/147—Microfiltration
• • 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
  • B32B2250/00—Layers arrangement
  • B32B2250/02—2 layers
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0223—Vinyl resin fibres
  • B32B2262/023—Aromatic vinyl resin, e.g. styrenic (co)polymers
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0223—Vinyl resin fibres
  • B32B2262/0238—Vinyl halide, e.g. PVC, PVDC, PVF, PVDF
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0246—Acrylic resin fibres
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0253—Polyolefin fibres
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0276—Polyester fibres
  • B32B2262/0284—Polyethylene terephthalate [PET] or polybutylene terephthalate [PBT]
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0292—Polyurethane fibres
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/04—Cellulosic plastic fibres, e.g. rayon
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/06—Vegetal fibres
  • B32B2262/062—Cellulose fibres, e.g. cotton
• • 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
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/06—Vegetal fibres
  • B32B2262/062—Cellulose fibres, e.g. cotton
  • B32B2262/065—Lignocellulosic fibres, e.g. jute, sisal, hemp, flax, bamboo
• • 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
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/732—Dimensional properties

Definitions

• the invention relates to a process for the production of a filter membrane for filters intended for the efficient microfiltration of liquids and air, particularly in the field of capture ultra-fine particles.
• Nanostructures form structures with a mean pore size of around 300 nm and can therefore also be used for microfiltration of liquids, especially water, which is a process that removes all bacteria with high efficiency.
• the disadvantage of using nanostructures for liquid filtration is their poor mechanical properties. Membranes prepared from them therefore require additional reinforcement by joining (lamination) with suitable support layers.
• Methods for joining layers of very fine fibres into laminated structures of filter materials are the subject of, for example, PCT International Patent Application WO 2011/052865, PCT International Patent Application WO 2012/135679, or U.S. Patent Application 2013118973.
• the subject of the International Patent Application PCT WO 2013/066022 is again a joining method in which a layer of very fine fibres with a lower melting point (50-170°C) is applied to the suppurt material on one or both sides by electro spinning, and a layer of very fine fibres with higher melting point (80-250°C) is applied over it. During the subsequent thermal lamination, the layer with a lower melting point is partially melted and the layers are joined. Similarly, the connection of filter structures is addressed in Patent EP1985349 of German authors.
• a composite comprising at least one layer of nanofibres is known from the prior state- of-the-art; for example, as also represented by document CZ 25797 U1 (NAFIGATE Corporation, a.s.).
• the polymer nanofibre filter layer can be directly applied to the surface of the carrier layer, which serves as a support material for depositing polymer nanofibres, using calendering and/or a binder suitable for sufficiently durable bonding of the carrier layer and the filter layer.
• This binder can be applied in the form of powder and/or paste and/or gels and/or liquids, in the form of a regular or irregular grid and/or separate formations, such as fibres and/or particles and/or stripes and/or other formations.
• the fusible component penetrates into the fine pores of the filter materials and significantly reduces the effective filtration area, i.e., increasing the pressure resistance and decreasing the flow rate.
• the factor that contributes to eliminating the above- mentioned shortcomings is a method for producing a filter membrane, which in its multilayer structure comprises at least one support layer of polymeric textile with a basis weight of 15 to 200 g/m 2 , and at least one associated layer of electrospun nonwoven nanotextile with a basis weight of 0.05 to 8 g/m 2 , with a distribution of nanofibre diameters in the range of 40 to 400 nm and mean pore size of 200 to 1,800 nm.
• the object of the invention is to compress the said layer of polymeric textile with the said layer of electrospun nonwoven nanotextile at a temperature of 50 to 200°C, preferably at a temperature of 130 to 150°C, and a pressure of 0.5 to 10 bar.
• a polymeric textile with a wide molecular weight distribution is used as the support layer, the low molecular weight fractions of which have a melting point in the pressing temperature range, and, in the molten state during compression cause bonding to the electrospun nonwoven nanotextile of polymeric material with a melting point above the upper limit of the pressing temperature range.
• a polymeric support textile with a wide molecular weight distribution a polymeric textile made of partially degraded polyethylene terephthalate is preferably used, the low molecular weight fractions of which have a melting point of 145 to 170°C, and, when compressing the support layer of the polymeric textile with a layer of electrospun nonwoven nanotextile at a temperature of 50 to 200°C and pressure of 0.5 to 10 bar, it additionally causes reinforcing of the support layer when connecting the two layers.
• a layer of submicron fibres supportd on a polymer from the group consisting of polyvinylidene fluoride, polyurethane, polylactic acid, polyamide, polyacrylonitrile, cellulose acetate, polystyrene, polysulfone, and poly ether- sulfone is preferably used as the nonwoven nanofibre textile layer.
• the prepared structure of the support textile formed of a polymer with a wide molecular weight distribution, connected to the nanofibre layer, can then be provided with a cover layer consisting of polypropylene, polyethylene, polyamide or polyester melt blown, spun bond or spun lace nonwoven textiles or nets, or woven fabrics of synthetic fibres particularly supportd on polypropylene, polyethylene terephthalate and polyamide, or natural fibres such as flax, hemp, cotton or mixtures thereof.
• Membranes reinforced with woven or nonwoven polymeric textiles prepared by the process according to the invention already have sufficient mechanical properties necessary for liquid-microfiltration membranes and can also be used for pleating into air filters.
• the most important variables in the preparation of membranes are pressing pressure and temperature.
• Nanostructured surface of the filter material formed at 130°C Figure 5. Comparison of distilled water flow through a washed and unwashed microfiltration membrane
• the water microfiltration membrane was produced by compressing a 70 g/m 2 nonwoven support layer made of partially degraded polyethylene terephthalate with a wide molecular weight distribution (see Figure 1), prepared from recycled polymer, and a layer of 2.4 g/m 2 electrospun nonwoven nanotextile made of polyvinylidene fluoride nanofibres with a mean nanofibre diameter of around 160 nm.
• the pressing took place at a pressure of 4 bar and a temperature of 150°C. At this pressing temperature, the low molecular weight fractions in the polyethylene terephthalate support layer were optimally melted, and thus the desired reinforcing of the filtration material took place while the filter nanostructure remained intact (see structure in Figure 2).
• the water microfiltration membrane was produced by compressing 2.4 g/m 2 polyvinylidene fluoride nanofibres with a mean nanofibre diameter of about 160 nm and a nonwoven textile having a basis weight of 70 g/m 2 made of partially degraded polyethylene terephthalate with a wide molecular weight distribution like Example 1.
• the pressing took place at a pressure of 4 bar and a temperature of 130°C.
• the flow of distilled water at a pressure of 1 bar through the membrane dropped from 140000 l/m 2 h to 30000 l/m 2 h in one hour. The reason of this decrease is the biofilm formation shown in Figure 3.
• the filter membrane prepared by pressing with 4 bar at 130°C had a smooth surface, and the structure shown in Figure 4 can be cleaned by repeated washing (with the effect shown in the graph in Figure 5) and by backwashing.
• the composition of the two-layer filter material was the same as in Examples 1 and 2, but a fabric with a basis weight of 100 g/m 2 , woven from polyethylene terephthalate yarns formed of two fibres plied from 3 yarns with a fineness of 20 tex was used as the support fabric.
• the polyethylene terephthalate used was formed from macromolecules with a wide molecular weight distribution as in Example 1.
• the reinforcing of the membrane at a pressing temperature of 130°C was less than in Example 1, but the other microfiltration capabilities of the membrane were maintained.
• the nanofibre layer used was the same as in Examples 1, 2 and 3, but a nonwoven textile prepared from a mixture of polypropylene and polyethylene terephthalate staple was used as a substrate, where the staple was prepared in a fibre weight ratio of 65:35, with a total basis weight of 30 g/m 2 .
• the polyethylene terephthalate fibres used were made of a polymer with a wide molecular weight distribution.
• the reinforcing of the filter material was less than in Example 1, however, by pressing at a temperature of 140°C and a pressure of 4 bar, a material with good compatibility with the nanostructure and pleatable with commercial equipment was prepared.
• the used support nonwoven textile was the same as in Example 1, but the nanofibre layer was alternatively made of polymer- supportd nanofibres from the group consisting of polyurethanes, polylactic acid, polyamide 6, polyacrylonitrile, cellulose acetate, polystyrene, polysulfone and polyether-sulfone.
• the filtration membrane was prepared by layering polyvinylidene fluoride nanofibres with a basis weight of 2.3 g/m 2 on a polypropylene spun bond textile with a basis weight of 50 g/m 2 and a molar weight distribution corresponding to the DSC record in Figure 8.
• the double layer material was pressed down and subsequently smoothed at a temperature of 80°C and a pressure of 1 bar.
• a filter material has a multilayer structure, which is formed as a sandwich with a layer composition of a polyethylene terephthalate fibre nonwoven textile with a wide molecular weight distribution as in Example 1 and a basis weight of 50 g/m 2 - polyvinylidene fluoride nanofibre nonwoven nanotextile - nonwoven textile of polyethylene terephthalate fibres with a wide molar weight distribution as in Example 1 and a basis weight of 50 g/m 2 .
• Such significantly reinforced material can be used for liquid microfiltration at elevated pressure.
• the eighth example of technical evaluation describes a filter material for air filtration with a multilayer structure, which is formed as a sandwich with a composition of nonwoven textile of polyethylene terephthalate fibres, with a wide molecular weight distribution as in Example 1 and a basis weight of 50 g/m 2 - nonwoven nanotextile of polyvinylidene fluoride nanofibres - viscose nonwoven textile with a basis weight of 30 g/m 2 .
• This material can be used for pleating (Figure 9) into air filters with increased efficiency of capturing ultra-fine particles.
• the starting filter material described in this example with 2.5 g/m 2 of polyvinylidene fluoride nanofibres has, in the planar state, a filtration efficiency according to EN143 higher than 99.999% and a pressure drop at a flow rate of 301/min lower than 300 Pa.
• Example 8 The same composition of sandwich material as in Example 8, but instead of viscose nonwoven textile, polypropylene spun bond and melt blown textiles with basis weights from 15 to 70 g/m 2 were used. Compared to brittle borosilicate materials, the polymer filters, due to their elasticity, have better resistance to damage during pleating.
• a window net for capturing a high proportion of ultra-fine particles and bacteria from the air was prepared in a sandwich arrangement of two polyester nets with a middle layer of polyvinylidene fluoride nanofibres with a basis weight of 0.06 g/m 2 , corresponding to a pressure loss of 8 Pa at an air flow of 30 l/m 2 h.
• the lower polyethylene terephthalate net was characterised by a basis weight of 24 g/m 2 , an open area of 69%, a thickness of 110 pm, a square mesh size of 240 pm and a yarn diameter in the warp and weft of 55 pm.
• the upper polyethylene terephthalate net had a square mesh size of 1,000 pm and a yarn diameter in the warp and weft of 200 pm. Both nets were made of polyethylene terephthalate with a wide molecular weight distribution.
• the three-layer window net was prepared by pressing between two heated rollers at a temperature of 140°C and a pressure of 4 bar.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Nanotechnology (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Textile Engineering (AREA)
• Composite Materials (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Fluid Mechanics (AREA)
• Filtering Materials (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

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