CZ306779B6 - Morphologically optimized non-woven fabrics based on nanofibres - Google Patents

Abstract

The prepared spatial nanostructures contain regular structures based on drop-shaped microspheres of polymers, or polymer mixtures, ensuring the emergence of spatial bulky structures, preparable by a suitable combination of variables in the electrospinning process. These spatial bulky structures show, in comparison with planar structures, a greater thickness and basis weight of the filter material, i.e., so desired improvement of mechanical properties and handleability of the filter nanomaterial. However, if we compare planar and spatially arranged nanostructures with the same pressure resistance, then spatial morphology materials have a more effective fibre surface and better filtration properties when eliminating ultrafine particles, i.e. filtration efficiency and the quality factor.

Description

Technical field

The present invention relates to morphologically optimized nanofiber-based nonwovens, obtainable by electrospinning technologies, exhibiting improved filtration efficiency and an increased quality factor of filterable nanofibrous nonwovens.

BACKGROUND OF THE INVENTION

Electrospinning of polymer solutions is currently the most widely used technique for preparing fibers with diameters in tens of nm. The first US patent 1 975 504 relating to this technology dates back to 1934. Increased interest in nanostructures since the early 1990s is associated with the possibilities to reduce dimensions, save materials and achieve new properties, other technologies currently unattainable.

At present, there is an increasing demand for the elimination of ultrafine particles, bacteria and viruses from air and drinking water, which are responsible for the growing number of allergies and respiratory-tract diseases in industrial agglomerations and the spread of various pandemics. It can be assumed that nanofiber structures will find their application mainly in the areas of microfiltration (ie for the removal of particles with sizes from 100 nm to 15 µm) and ultrafiltration (for particles from 5 to 100 nm). However, it is necessary to optimize nanofibrous structures with respect to this application.

Given that diffusion is the dominant mechanism used to capture ultra-fine particles, it can be assumed that due to the longer path of the ultra-fine particle performing Brownian motion, the probability of entrapment on the surface of nanofibers or teardrop formation will increase in spatial structures.

In this regard, the tendency to form droplets or beads in the nanofibrous structure in low viscosity or low viscosity spinning solutions is also of interest in the three-dimensional nanofibrous structures disclosed in U.S. Patent 7,828,539. solutions of low molecular weight polymers.

In general, however, randomly scattered droplet formations in the nanofibrous structure have hitherto been considered rather defects that can be eliminated, for example, by suitable additive solution. By using a modifying additive (Borax and / or citric acid) to improve the conductivity of the polyurethane spinning solution (15 wt% in dimethylformamide), a significant suppression of droplet defect formation can be achieved (see Figures 1, 2). The addition of surfactants such as ionic liquids can also eliminate droplet defects in PU structures very effectively (Figs. 3 and 4). The change was achieved by adding 1 wt. % (based on polymer dry weight) of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide from IoLiTec Ionic Liquids Technologies, Germany.

The solution according to the cited U.S. patent 7,828,539 cannot therefore be regarded as a targeted optimization of nanofibrous structures in order to improve their filtering effect.

At present, the following solutions can be considered as a certain effort to optimize electrospinning nanofibrous structures for filter materials:

Japanese Patent Application 2010/247 035 discloses a nonwoven fabric for filtering purposes comprising a nanofibrous structure with nanofibres physically separated by droplet-like spacers ("rosary" type) and / or nanoparticles dispersed in the nanostructure, and the fibers may be of different diameters.

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Also in Korean patent application 2004/0 024 077 a nonwoven fabric of nanofibres with improved filtration properties is provided, wherein the nanofibrous structure is made of polyurethane and comprises droplet-like spacer formations and / or particles dispersed in the nanostructure. The formation of a nonwoven fabric from a nanofibrous structure comprising droplet-like spacers and / or nanoparticles is also known from European patent application 2 198 944. The fabric disclosed herein is made of polyurethane fibers and contains titanium dioxide particles.

It is apparent from US patent application 2010/206 803 that for filtering purposes a nonwoven fibrous structure comprising nanofibres made of polyurethane or polycarbonate is used. It is a fibrous structure with a bimodal distribution of fiber diameters based on a micro- and nanofiber composition, and also contains spacers and / or nanoparticles. This fabric is also produced by electrostatic spinning. The formation of a non-woven fabric for micro- and nanofiber fibrous filter filters is also evident from U.S. Patent Application 2007/190 319, wherein polyurethane is used as the polymer for production.

In Korean patent application 2007/0 078 177, a nanofibrous structure (nonwoven) of polyurethane fibers containing silver nanoparticles dispersed in the nanostructure is disclosed.

However, it is clear from the principles of the known solutions mentioned above that, due to the considerable heterogeneity of the fabric structure, mainly due to the irregularity of the spacing of the spacers, the optimization of the aforementioned nanofibrous structures still cannot be considered sufficiently effective.

SUMMARY OF THE INVENTION

To overcome the aforementioned drawback of the prior art, the morphologically optimized nonwoven fabrics based on the nanofibres according to the invention, exhibiting a significantly enhanced filter effect, contribute. They contain, as well as known nanofibrous nonwoven fabrics, nanofibres and at the same time teardrop spacers accumulated irregularly into columns and / or microfibre spacers or structures with a bimodal microfibre diameter distribution based on the combination of microfibers and nanofibres, said spacers and structures physically separating nanofibers and mechanically maintain them in spatial arrangements ensuring optimization of filtration efficiency and / or reduction of pressure resistance in comparison with flat, spatially non-enlarged, non-reinforced nonwoven nanofibers.

The essence of the invention is that the droplet-like spacers accumulated in columns are interconnected in a more voluminous regular bee-like arrangement, while the microfibre or bimodal fiber diameter distribution structures based on the combination of microfibers and nanofibres contain fibers of rigid polymers such as polyethersulfone , polymethyl methacrylate, polyvinylidene chloride, styrene-acrylonitrile copolymer and polyurethane having a hard segment content of at least 44% by weight and are stacked with mechanically maintained distances in bulky arrangements.

The regular structures formed by the interconnection of nanofibres with the droplet-like spacers accumulated in columns into spatially larger regular bee-like arrangements can be advantageously structures obtainable by electrospinning technology from a polycarbonate spinning solution in tetrachloroethane containing the addition of chloroform and borax.

Another preferred solution is regular structures formed by the interconnection of nanofibres with teardrop spacers accumulated in columns into spatially larger regular bee-like regular arrangements, obtainable by electrospinning technology from polyurethane spinning solution in dimethylformamide or in a mixture of dimethylformamide and tetrachloroethane.

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It has been found that in the preparation of polycarbonate (PC) nanostructures with a change in the solvent system (addition of chloroform to tetrachloroethane) and addition of borax, it will increase the nanofiber content between droplet defects (see Figs. 5,6) and create a regular structure where droplet defects accumulate in columns connected by nanofibers. Such a honeycomb-like spatial arrangement results in an increase in the thickness of the filter material, an increase in basis weight, an increase in solid volume fraction (SVF), but the free volume fraction (FVF) does not differ significantly from flat nanofibrous structures. Furthermore, this morphology significantly contributes to the increase of the specific surface area and thus positively affects the filtration properties.

The spatial structure with arranged teardrop spacers (Fig. 6) with a basis weight of 3.42 g / m ² had an aerosol permeability of 0.762% at a pressure resistance of 35 Pa, corresponding to qF = 139 (measured on a Lorenz according to EN 143).

(Note: when assessing filter quality, both pressure resistance (Δρ) and filtration efficiency (E) should be taken into account. The relationship between these two characteristics is best described by the quality factor qF = 1η (1 / Ρ) / Δρ, where permeability P = 1-E).

Spatial structures with spacers arranged in honeycomb structures (see Fig. 7) can also be prepared from a polyurethane spinning solution in a mixture of dimethylformamide and tetrachloroethane solvents.

An elegant method of forming structures with polymer spacers is to combine two types of polyurethanes with different mean molar masses, where one (with lower M) forms globulamic microspheres under the given electrospinning conditions and the other nanofibers. One rigid polyurethane with hard segments up to 40% by weight can also be used. The hard segment content of polyurethane is the percentage by weight of diisocyanate and chain extenders in the polyurethane chains.

Table 1 summarizes the filtration properties and dimensional characteristics of planar polyurethane (see Figure 4) and spatial polycarbonate (see Figure 6) nanostructures. In order to compare the influence of the structure on the filtration efficiency, structures with the same pressure resistance of ~ 90 Pa are always compared.

The compared nanostructures (Table 1, Fig. 10), which exhibit the same pressure drop when filtering ultrafine particles, consist of fibers of comparable average diameter and the pore distribution in the nanostructure (D _n , D _w ) varies significantly in basis weight, thickness and effective area of the filter, which is why the filtration efficiency of the spatial nanostructure and hence the factor and quality of the filter are improved.

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Table 1: Characterization and properties of spatial and surface nanostructures

Nanostructures with pressure resistance ~ 90 Pa Sample Spatial nanostructure of PC with distance microspheres PC 88 Plain nanostructure PU PU 90 Basis weight (g / m) 6.80 0.807 Thickness (pm) 30,2 * 9,2 * SVF solid phase volume (m ³ / m ³ ) 0.188 0,080 FVF Free Volume (%) 81.2 92.0 Filtration properties of ultrafine particles Particle size with the highest MPPS nanostructure penetration (nm) 100 ALIGN! 70 Pressure drop (Pa) 81 -95 90 Filtration efficiency in MPPS (%) 98.90 90.35 Quality factor in MPPS (1 / kPa) 51 26 Morphological characteristics of nanostructures obtained by digital image analysis of SEM images Average fiber diameter (nm) 120.2 124.7 Pore size distribution (nm) □ n 202.5 139 D _w 740.0 327 D _z 1 269.0 493 D _z + i 1 721.0 640 Effective filter area (m) 188.9 23.6

* measured from SEM images

Since diffusion, as mentioned above, is the dominant mechanism used to capture ultra-fine particles, it can be assumed that due to the longer path of the ultra-fine particle performing Brownian motion, spatial structures will increase the likelihood of entrapment on the surface of nanofibers or teardrop formation.

To demonstrate the mechanism by which the filtration capability of bulky structures is improved, fiber diameter distributions were determined (see Figure 11) and the pore size and distribution of the structures with microscopic spacers was monitored (see Figure 12). Digital analysis of SEM images of real nanostructures was used for these determinations. A detailed description of the method used is given in W. Sambaer, M. Zatloukal and D. Kimmer, The use of novel digital image analysis techniques and rheological tools to characterize nanofiber nonwovens, Polymer Testing 29, 82-94 (2010).

A comparison of the pore distributions of the prepared nanostructures (Fig. 12) shows that the pore distribution of the spatial arrangement of the droplet-shaped nanostructure is wider, it contains larger pores, but the mean value of the distribution does not differ significantly from the plain nanostructures. However, the spatial nanostructure has approximately 15 times greater basis weight and 11 times greater thickness. Spatial arrangement results in physical separation of nanofibrous layers, increasing of distances between nanofibres and angles under which they are embedded in nanostructures. Such morphology results in improved filtering properties of nanostructures.

The function of spatial barriers in nanofibrous structures can be provided by structures made of rigid, inflexible, high-module fibers instead of regular structures of teardrop formations. Such arrangements ensure an increase in the thickness and volume of the filter material that is formed

Fiber fibers with a wide diameter distribution also show improved filtration properties. The tendency to create such arrangements - see Figures 13 to 15, is mainly due to rigid polymers with high modulus of elasticity, such as polymethyl methacrylate (PMMA), styrene-acrylonitrile (SAN) copolymer, but also polyurethane with a high hard segment content.

These structures, characterized in Table 2 below, have approximately half the pressure drop than the materials in Table 1. Attention is focused on low pressure resistances due to the potential application of nanostructures in face masks and for mask filters.

In Table 2 and Figure 16, the properties of the material with the morphology of Figure 14 are compared with the surface structure (Figure 4). The combination of globular microspheres and nanofibres (Figure 14) leads to an improvement in the filtration properties of the material.

Table 2: Characterization and properties of spatial and surface nanostructures

Nanostructures with pressure resistance ~ 45 Pa Sample Combined spatial nanostructure of PMMA with wide PC 88 fiber distribution Plain nanostructure PU PU 90 Basis weight (g / m ² ) 6.92 0.403 Thickness (pm) 34.7 4.6 SVF solid phase volume (m ³ / m ³ ) 0.169 0,080 FVF Free Volume (%) 83.1 92.0 Filtration properties of ultrafine particles Particle size easily penetrating MPPS nanostructure (nm) 50 100 ALIGN! Pressure drop (Pa) 48 45 Filtration efficiency in MPPS (%) 97.52 78.77 Quality factor in MPPS (1 / kPa) 77 44 Morphological characteristics of nanostructures obtained by digital image analysis of SEM images Average fiber diameter (nm) 758.6 124.7 Pore size distribution (nm) D _n 672 139 D _w 2564 327 D _z 4409 493 D _z + i 6151 640 Effective filter area (m ² ) 30.9 11.8

* measured from SEM images

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The materials to be compared differ in fiber diameter distribution (Figure 17) and pore size distribution (Figure 18). Bulky structures are more effective in capturing ultrafine particles at equal pressure resistances.

Clarification of drawings

The following drawings illustrate the invention in greater detail:

Giant. 1 - polyurethane nanostructure with drop-shaped defects - without additives, magnification 1500x.

Giant. 2 - polyurethane nanostructure droplike with the elimination of defects occurring in the presence of Na ₂ B ₄ O _7th 10 H ₂ O and citric acid, magnification 1500x.

Giant. 3 - Polyurethane nanostructure with drop-shaped defects - without additives, magnification of 5000x.

Giant. 4 - polyurethane nanostructure with elimination of drop-shaped defects, occurring in presence of ionic liquid, magnification 5000x.

Giant. 5 - polycarbonate nanostructure before optimization process, magnification 1500x.

Giant. 6 - polycarbonate nanostructure after optimization with regular structures of teardrop spacers, magnification 1500x.

Giant. 7 - polyurethane nanostructure with regular structures of teardrop spacers, prepared from a solvent mixture of dimethylformamide / tetrachloroethane, magnification 1500x.

Giant. 10 - comparison of flame filtration efficiency and spatial nanostructure according to Table 1; pressure loss of compared nanostructures ~ 90 Pa.

Giant. 11 - comparison of flame fiber diameter and spatial nanostructure distributions according to Table 1; the bars represent the measured values, the link is a function based on the Gaussian approximation.

Giant. 12 - comparison of the pore distributions of the planar and spatial nanostructures according to Table 1; the bars represent the measured values, the link is a function based on the Gaussian approximation.

Giant. 13 - combined spatial nanostructure made of polyethersulfone fibers with wide diameter distribution, magnification 5000x.

Giant. 14- combined spatial structure made of polymatyl methacrylate fibers with wide diameter distribution, magnification 1500x.

Giant. 15 - Combined spatial structure consisting of fibers of styrene-acrylonitrile copolymer with wide diameter distribution, magnification 1500x.

Giant. 16 - comparison of filtration efficiency of surface nanostructure with polymethylmethacrylate structure, consisting of combination of micro- and nanofibres. Pressure drop of compared materials ~ 45 Pa.

Giant. 17 - Comparison of the fiber diameter distribution of the flame filter and the spatial nanostructure according to Table 2.

Giant. 18 - Comparison of the pore distribution of the planar and spatial nanostructures according to Table 2.

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DETAILED DESCRIPTION OF THE INVENTION

Example 1

An example of polycarbonate nanofibrous structure with nanofibres physically separated by teardrop spacers forming regular structures with teardrop spacers accumulated in columns, connected by nanofibres into regular bee-like arrangement can be characterized by the following preparation conditions and utility properties:

a) spinning solution: polycarbonate (Macrolon 2458, Bayer, Leverkusen, Germany, p = 1.2 g.cm -3) solution for electrospinning was prepared in a solvent mixture tetrachloroethane: chloroform 3: 1 and treated with a mixture of ionic liquids 1-ethyl-3- methylimidazolium bis (trifluoromethylsulfonyljimide): 1-ethyl-3-methylimidazolium triflate 2: 1 (loLiTec Ionic Liquids Technologies, Heilbronn, Germany) and 1 wt% borax. The polycarbonate solution had a viscosity of 0.3 Pa and an electrical conductivity of 10.5 μ .Sem ' ¹ .

b) electrospinning conditions: Nanospider fiber forming device (Elmarco, Liberec, Czech Republic), rotating electrode with three cotton cords (according to PCT / CZ2010 / 000042), voltage supplied to the tray with solution U = 25 to 75 kV, electrode distance D = 15 to 25 cm, electrode rotation speed - 7 to 14 rpm, collection rate (antistatic treated PPNT or polyester nonwoven or viscose nonwoven) 16 to 32 cm / min.

c) characterization of prepared nanostructure: in addition to calculations of basis weight, solid phase volume (SVF), free volume (FVF) and effective filter area, a Vega 3 scanning electron microscope (SEM) was used to characterize nanostructures (Tescan, Brno, Czech Republic). SEM images were subsequently used to determine nanofiber layer thickness and fiber diameter / pore size distribution using the digital image analysis technique of W. Sambaer, M. Zatloukal and D. Kimmer, The use of novel digital image analysis techniques and rheological tools to characterize Nanofiber Nonwovens, Polymer Testing 29, 82-94 (2010).

d) filtration efficiency measurement: produced filter materials were tested for aerosol penetration (diethylhexyl sebacate with particle diameter 0.45 pm) at a flow rate of 30 l.min * ¹ (front velocity 5.7 cm.s ¹ ) using the LORENZ filter measuring system (Germany) ) adapted to EN 143. Measurement in the field of ultrafine particles was performed with ammonium sulfate aerosol using a sprayer (AGK, PALAŠ, Germany), an electrostatic classifier (EC 3080, TS1, USA) and a particle condensation counter (UCPC 3025 A, TSI, USA) ) at a front speed of 5.7 cm @ ^-1 . Filtration efficiency and pressure drop were determined for nine fractions of 20, 35, 50, 70, 100, 140, 200, 280 and 400 nm diameters.

The penetration of nanoparticles (450 nm diameter) measured according to EN 143 over the prepared spatial structure for a material with a basis weight of 3.42 gm ^{< 2 >} was 0.762%, at a pressure drop of 45 Pa, corresponding to a quality factor qF = 139 kPa ^-1 . The material having a basis weight of 6.8 gsm ² was for trapping ultrafine particle filtration efficiency of 99.9% MPPS (maximum penetration particle size) of 100 nm and at a pressure drop of 90 Pa, which corresponds to a quality factor of about 51 psi = qF ^'first The filtration properties of materials with such a spatial structure exceed the capabilities of flat nanofibrous materials.

Example 2

All conditions were the same as in Example 1, only in the experimental apparatus instead of the rotating yarn electrode the arrangement with spinning nozzles Spinline 120, SPUR, Zlín, Czech Republic was used.

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Example 3

Ordered spatial nanostructures made up of nanofibres and globular spacers were prepared from highly elastic polyurethanes - a combination of two polyurethanes with different molar mass distribution, one of which under fine electrospinning conditions consists of fine fibers and at least one rather spherical or teardrop formations. Polyurethane solution in dimethylformamide prepared from 4,4'-methylene-bis (phenylisocyanate) (MDI), poly (3-methyl-1,5-pentanediol) -alt- (adipic, isophthalic acid) (PAIM) and 1,4 butanediol ( (BD) was synthesized in a molar ratio of 9: 1: 8 (PU 918) at 90 ° C for 5 hours (per partes synthesis method, in which a prepolymer of MDI and PAIM is prepared in the first step and BD and the remaining amount of MDI are added) . The density of PU 918 p = 1.1 g.cm &^lt; ³ & gt ^; . The solution thus prepared was mixed with a solution of polyurethane in dimethylformamide prepared from MDI: polyester diol: chain extender in a molar ratio of 4: 1: 3 with a density p = 1.05 g.cm &^lt; 3 > density p = 1.04 g.cm &^lt; ³ & gt ^; . Prepared mixtures with solids from 10.5 to 19 wt. % and viscosities of 0.35 to 2.7 Pa.s form the desired ordered spatial structures under the electrospinning conditions of Example 1. The hard segment content of polyurethane is the percentage by weight of diisocyanate and chain extenders in the polyurethane chains. When measuring filtration properties, these materials exhibit significantly lower pressure losses than nanostructures without globular spacers at the same filtration efficiency.

Example 4

The electrospin spatial structure was prepared from PU 918, synthesized according to Example 3, dissolved in a solvent mixture of dimethylformamide: tetrachloroethane in a weight ratio of 98.5: 1.5 under processing conditions: solution concentration = 12.5%, voltage = 55 kV, electrode gap = 21 cm, electrical conductivity = 16.5 pS / cm.

Compared to the planar arrangement, the spatial arrangement at the same pressure resistance of 100 Pa shows an increase in filtration efficiency in the ultra-fine particle region from 90.4% to 97.8% for MPPS 70.

Example 5

Conditions as in Example 4, but instead of the polyurethane solution, a solution of ethylene-vinyl acetate (EVA) in toluene: tetrachloroethane solvent mixture in wt. 3: 1 ratio.

Example 6

An example of a fiber-based nanofibrous structure with a wide diameter distribution of rigid polymers with high modulus of elasticity, folded with mechanically maintained distances in bulky configurations, can be characterized by the following preparation conditions and utility properties:

(a) spinning solution: polymethylmethacrylate (PMMA, Altuglas V 046, Altuglas Intemational, La Garenne-Colombes Cedex, France) with a density p = 1.18 g.cm ^-3 , solution in dimethylformamide / toluene solvent mixture in wt. ratio of 1: 1 with a concentration of 20% by weight, a viscosity of 0.11 Pa · s and a conductivity of 1.3 pS.cm ^-1 .

b) electrospinning conditions and characterization of the prepared nanostructures were similar to Example 1.

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c) the aerosol penetration of nanoparticles (diameter 450 nm), measured according to EN 143 thus prepared through a spatial structure with a broad distribution of fiber diameters for a material having a basis weight of 6.92 gsm ² was 1.095% at a pressure drop of 45 Pa, which corresponds to a quality factor qF = 181 kPa ¹ . This material exhibited a filtration efficiency of 97.52% for MPPS 50 nm and a pressure drop of 48 Pa, corresponding to a quality factor of qF = 77 kPa ¹ , for capturing ultrafine particles. The filtration properties of materials with a spatial structure with a wide distribution of fiber diameters also exceed the capabilities of flat nanofibrous materials.

Example 7

Another fiber-based spatial structure with a wide diameter distribution of rigid polymers with high modulus was prepared from a 20% solution of polyethersulfone in dimethylformamide (Ultrason, BASF, Germany) with a viscosity of 0.84 Pa.s, and an electrical conductivity of 159 pS.cm -1. ¹ on an SPUR jet electrostatic spinner.

Electrospinning conditions: Voltage U = 75 kV, electrode distance D = 21 cm, electrode rotation speed = 7 rpm, relative humidity = 25%, temperature = 28 ° C, collection rate (viscose nonwoven) = 14 cm / min.

Example 8

All conditions were the same as in Example 6 except that polyvinylidene fluoride (PVDF, Kynar451, Arkema, PA, USA) was used instead of polymethyl methacrylate.

Example 9

All conditions were the same as in Example 6, but a styrene-acrylonitrile copolymer (SAN, Luran HH-120 Natural, BASF, Germany) dissolved in dimethylformamide was used to prepare a spatial structure with a wide fiber diameter distribution.

Example 10

The spatial structure with a wide fiber diameter distribution was prepared from a bicomponent fiber prepared from styrene-acrylonitrile (SAN) -Luran and PU 312 copolymers in a dimethylformamide / toluene solvent system. In addition to the required filtration properties, the prepared nanostructure has significantly better mechanical properties due to the use of elastic polyurethane.

Example 11

A solution of polyamide 11 (PA11, Rilsan D, Arkema, UK) and PU 918 (2 to 5 wt% on dry weight of PA11) in a mixture of trifluoroacetic acid / dimethylformamide in a ratio of 92- While PA11 alone forms surface nanostructures under the electrospinning conditions of Example 1, a spatial structure is formed in the presence of a small amount of polyurethane, which exhibits more than a two-fold improvement in the quality factor compared to the surface structure.

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Example 12

All conditions were the same as in Example 6, but instead of polymethyl methacrylate, a polyurethane with a high content of hard segments was used to form a microfiber electrospinning under the given conditions.

Example 13

All conditions were the same as in Examples 6-8, but the process was carried out on an SPUR electrostatic device where the solutions were fed to individual nozzles arranged in four rows.

Claims (3)

PATENT CLAIMS Morphologically optimized non-woven fabrics with enhanced filtering effect, comprising nanofibres and at the same time droplet-like spacers accumulated irregularly into columns and / or microfibre spacing or bimodal diameter distribution structures based on a combination of microfibers and nanofibres, said spacers and structures physically separate nanofibres and mechanically maintain them in spatial arrangements to optimize filtration efficiency and / or reduce pressure resistance compared to flat, spatially non-enlarged, non-reinforced nonwoven nanofibrous fabrics, characterized in that the teardrop spacers accumulated in columns are interconnected into spatial bulky regular bee-like arrangements, while microfibre spacers or bimodal fiber diameter distribution combinations The microfibers and nanofibres comprise fibers of rigid polymers such as polyethersulfone, polymethyl methacrylate, polyvinylidene fluoride, styrene-acrylonitrile copolymer and polyurethane having a hard segment content of at least 44% by weight, and are stacked with mechanically maintained distances in bulky arrangements. Morphologically optimized nonwoven fabrics according to claim 1, characterized in that the regular structures formed by the interconnection of nanofibres with teardrop spacers accumulated in columns into more spatially regular bee-like regular arrangements are structures obtainable by electrospinning technology from a polycarbonate spinning solution in tetrachloroethane containing an additive and borax. Morphologically optimized nonwovens according to claim 1, characterized in that the regular structures formed by the interconnection of nanofibres with teardrop-like spacers accumulated in columns into spatially larger regular bee-like regular arrangements are structures obtainable by electrospinning technology from polyurethane spinning solution in dimethylformamide or a mixture of dimethylformamide. and tetrachloroethane.