Microfiber Nonwoven Composite

Abstract

A microfiber nonwoven composite includes: at least one layer S that contains a first fiber component; and at least one layer M that contains a second fiber component. The second fiber component is forced at least in part into the layer S. Fibers of the first fiber component comprise melt-spun include filaments deposited as a nonwoven fabric, and which are at least partially split and solidified to form elementary filaments having an average titer of less than 1 dtex. Fibers of the second fiber component include melt-blown fibers.

Description

CROSS-REFERENCE TO PRIOR APPLICATION

[0001] Priority is claimed to German Patent Application No. DE 10 2017 006 289.7, filed on Jul. 4, 2017, the entire disclosure of which is hereby incorporated by reference herein.

FIELD

[0002] The invention relates to a microfiber nonwoven composite. The invention further relates to the production of such a nonwoven composite and to the use thereof.

BACKGROUND

[0003] Nonwoven fabrics are advantageous for many applications. Nonwoven fabrics are fabrics made of fibers of limited length, continuous fibers (filaments), or cut yarns of any type and any origin that have been combined and bonded together in some manner to create a textile fabric, fleece, nonwoven fabric, fiber layer, or fibrous web; this excludes the interlocking or interlooping of yarns as occurs in weaving, machine knitting, knitting, lace manufacture, braiding, and the manufacture of tufted products. Nonwoven fabrics may be produced in a wide variety of ways, for instance by means of mechanical, aerodynamic, and/or hydrodynamic methods.

[0004] One essential parameter of nonwoven fabrics is pore size distribution. Depending on the specific application, nonwoven fabrics having a suitable pore size distribution and suitable air flow resistance may be used, for example, as components of sound insulation layers in the construction field, sound insulation layers in motor vehicles, as barrier layers in home textiles (mite-proof products, anti-allergic bed linens, cleaning media), and packaging materials and filter media.

[0005] In the past, as a rule nonwoven fabrics comprising split microfibers were used for these applications. Although microfiber nonwovens have a suitable pore size distribution for various applications, combined with very good functionalities, their production method is technically comparatively complex, particularly for producing materials having a uniform and homogeneous pore size distribution, and frequently requires high mass per unit area. But as mass per unit area increases, it becomes increasingly difficult to achieve the high degrees of splitting required for the microfiber properties.

[0006] On the other hand, when using alternative materials, such as, for example, films, special papers, or even melt-blown fibers, the profile of the mechanical properties is often not satisfactory.

SUMMARY

[0007] In an embodiment, the present invention provides a microfiber nonwoven composite, comprising: at least one layer S that contains a first fiber component; and at least one layer M that contains a second fiber component, wherein the second fiber component is forced at least in part into the layer S, wherein fibers of the first fiber component comprise melt-spun composite filaments deposited as a nonwoven fabric, and which are at least partially split and solidified to form elementary filaments having an average titer of less than 1 dtex, wherein fibers of the second fiber component comprise melt-blown fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

[0009] FIGS. 1 and 2: Hot tensile strength test of exemplary embodiment 1; modulus of elasticity at 180.degree. C. in direct comparison to individual layers based on conventional microfibers in the weight range of 40 and 60 g/m.sup.2.

[0010] FIG. 3: Sound absorption rating/impedance of exemplary embodiment 1 compared to the individual layers used in exemplary embodiment 1.

[0011] FIG. 4: Sound absorption rating/impedance of exemplary embodiment 1 compared to type S individual layers following hydrofluid treatment (MF=microfibers).

[0012] FIG. 5: Cross-sectional image, produced by raster electron microscope, of an inventive microfiber nonwoven composite, comprising a layer S, a layer M, and a layer C.

DETAILED DESCRIPTION

[0013] According to the invention, the object is attained using a microfiber nonwoven composite comprising at least one layer S that contains a first fiber component and at least one layer M that contains a second fiber component, wherein the second fiber component is forced at least in part into the layer S and wherein [0014] the fibers of the first fiber component are melt-spun composite filaments deposited as a nonwoven fabric which are at least partially split and solidified to form elementary filaments having an average titer of less than 1 dtex; [0015] the fibers of the second fiber component are melt-blown fibers.

[0016] In the following, the composite filaments that are at least partially split to form elementary filaments having an average titer of less than 1 dtex are also called "split fibers," for short.

[0017] The inventive microfiber nonwoven composite is distinguished in that it contains split fibers in synergistic combination with melt-blown fibers.

[0018] According to the invention it was found that a nonwoven fabric having a small average pore diameter of preferably less than 20 .mu.m, for instance 7 .mu.m to 17 .mu.m, more preferably 9 .mu.m to 17 .mu.m, may be obtained using the special combination of the split fibers with the melt-blown fibers. The smallest pore diameter found may preferably be less than 11 .mu.m, for example 5 .mu.m to 10 .mu.m, more preferably 2 .mu.m to 6 .mu.m.

[0019] An inventive microfiber nonwoven composite having the aforesaid small pore diameters has the advantage that it has high fraction filtration efficiency with comparatively low mass per unit area, for instance a mass per unit area of less than 300 g/m.sup.2. This facilitates advantageous use, e.g., as a filter medium or in the field of textiles suitable for allergy sufferers.

[0020] At the same time, excellent mechanical properties were found, especially during loading when hot. Moreover, the special combination of split fibers with the melt-blown fibers proves unexpectedly favorable, especially in the context of sound absorption. In one inventive microfiber nonwoven composite there is a surprising synergistic effect of split fibers and melt-blown fibers in terms of sound absorption. The sound absorption coefficient is significantly above the range that would be expected from simply combining starting materials or evaluating the air flow resistance to be measured. This result was especially surprising because it was actually to be expected that the strong barrier effect normally produced by the melt-blown fibers would lead to disproportionately high air flow resistance, which should have proven disadvantageous for producing a balanced sound absorption profile.

[0021] Without determining a mechanism, it is presumed that the good performance of the inventive nonwoven fabric for sound absorption and as a filter medium is attained due to the at least partial penetration of the fiber components of layer M into layer S. According to the invention, the melt-blown fibers penetrate, at least in part, into layer S having the split fibers. A further mixing of the layers may occur in that both fiber components penetrate, at least in part, into the other layer and/or there is complete mixing of the fiber components of layers S and M. This effect may be attained, for instance, in that first a combined layer S'M' or even larger combined layers are formed (e.g., S'M'C) and then a hydraulic entanglement step is performed for the entire combined layer, in which hydraulic entanglement step, in addition to the mixing, splitting and solidification usefully occur at the same time. It has been found that, by means of hydraulic entanglement, both layers may be bonded to one another in one step and that no further splitting or subsequent solidification steps are required. Therefore, in the hydraulic entanglement process the composite filaments used for producing the layer S may be split and at the same time the melt-blown fibers may be distributed in the Z direction, i.e., in the direction of the cross section of the nonwoven fabric. Likewise, the split composite filaments used in the layer S may also be distributed in the Z direction, i.e., in the direction of the cross section of the nonwoven fabric. Depending on various parameters, such as, for example, the pressure used during the hydraulic entanglement, the layer thickness, and the tackiness of the melt-blown fibers, this may lead to a more or less uniform distribution of the melt-blown fibers in the layer S all the way to complete mixing of the two layers. This variability may be used to modify the property profile of the composite material in a targeted manner.

[0022] In doing so, e.g., properties that are normally assessed as negative may be compensated by individual layers of the composite. Thus, for example, regardless of parameters, following joint hydraulic entanglement of melt-blown fibers and composite filaments, a significantly higher abrasion resistance of the surface is found than would be expected for a surface solely comprising melt-blown fibers.

[0023] According to the invention, the first fiber component has melt-spun composite filaments deposited as a nonwoven fabric. The term filaments shall be construed to mean fibers according to the invention that, in contrast to staple fibers, have a theoretically unlimited length. Composite filaments comprise at least two elementary filaments and may be split and solidified to create elementary filaments using conventional splitting methods, such as, for example, hydraulic needle punching. According to the invention, the composite filaments of the first fiber component are at least partially split into elementary filaments.

[0024] Likewise, the titer of the composite filaments prior to splitting is preferably 1.5 to 3.5 dtex, more preferably 2.0 dtex to 3.0 dtex, and/or the titer of the elementary filaments is 0.01 dtex to 0.8 dtex, preferably 0.03 dtex to 0.6 dtex, and in particular 0.05 dtex to 0.5 dtex.

[0025] The composite filaments preferably have at least two incompatible polymers. Such composite filaments exhibit good splittability into elementary filaments and are responsible for a favorable ratio of strength to mass per unit area.

[0026] In order to attain a suitable pore size distribution with sufficient mechanical strength, it is advantageous when the portion of the elementary filaments of the first fiber components, relative to the total weight of the nonwoven fabric (as a total of all composite layers) is at least 20 wt. %. Practical experiments have demonstrated that a particularly balanced property profile between porosity and mechanical properties may be produced when the portion of these elementary filaments is 20 wt. % to 60 wt. %, in particular 30 wt. % to 50 wt. %, relative to the total weight of the nonwoven composite.

[0027] With respect to the individual layers of the nonwoven fabric, it is advantageous when the portion of the elementary filaments of the first fiber component in the specific layer S, for example in an outer layer S or in an interiorly disposed layer S, is from 80 wt. % to 100 wt. %, preferably 90 wt. % to 100 wt. %, in particular 100 wt. %, relative to the total weight of the layer S.

[0028] With respect to the abrasion resistance or pilling of the surface, it is advantageous when at least one outer layer of the nonwoven fabric is formed by the layers S.

[0029] With respect to using composite filaments as starting material for producing the elementary filaments, it is advantageous that the titer of the elementary filaments produced from said composite filaments may be easily adjusted by varying the number of elementary filaments contained in the composite filaments. The titer of the composite filaments may remain constant, which is advantageous from the perspective of procedure. It is further advantageous with respect to the use of the composite filaments that, in addition, the ratio of thicker and thinner filaments in the nonwoven fabric may be controlled in a simple manner by varying the degree of splitting for the composite filaments.

[0030] The elementary filaments may be embodied having a cross section that is a segment of a circle, that has n angles, or that has multiple lobes.

[0031] The inventive microfiber nonwoven composite is preferably a microfiber nonwoven composite in which the composite filaments have a cross section having an orange segment-type or "pie-shaped" aforesaid multisegment structure, wherein the segments may contain different, alternating incompatible polymers. Hollow pie structures, which may also have an asymmetrical axial hollow space, are also suitable. Pie structures, in particular hollow pie structures, are particularly easy to split.

[0032] With respect to the first fiber component, the orange segment or slice-of-cake arrangement (pie arrangement) advantageously has 2, 4, 8, 16, 24, 32, or 64 segments, particularly preferably 16, 24, or 32 segments.

[0033] To obtain easy splittability, it is advantageous when the composite filaments comprise filaments that contain at least two thermoplastic polymers. The composite filaments preferably comprise at least two incompatible polymers. Incompatible fibers shall be construed to mean those polymers that, when combined, do not provide any bonded pairings, or provide only marginally or poorly bonded pairings. Such a composite filament has good splittability into elementary filaments and results in a favorable ratio of strength to mass per unit area.

[0034] Preferably polyolefins, polyesters, polyamides, and/or polyurethanes are used as incompatible polymer pairs in such a combination such that adhering pairings do not result or only marginally or poorly bonded pairings result.

[0035] The polymer pairs used are particularly preferably selected from polymer pairs having at least one polyolefin and/or at least one polyamide, preferably with polyethylene, such as polypropylene/polyethylene, polyamide 6/polyethylene, or polyethylene terepthalate/polyethylene, or having polypropylene, such as polypropylene/polyethylene, polyamide 6/polypropylene, or polyethylene terephthalate/polypropylene.

[0036] Polymer pairs having at least one polyester and/or at least one polyamide are very particularly preferred.

[0037] Polymer pairs having at least one polyamide or having at least one polyethylene terephthalate are preferred due to their marginal bonding and polymer pairs having at least one polyolefin are particularly preferred due to their poor bonding.

[0038] As particularly preferred components, polyesters, preferably polyethylene terephthalate, polyacetic acid, and/or polybutylene terephthalate, on the one hand, and polyamide, preferably polyamide 6, polyamide 66, polyamide 46, on the other hand, have proved particularly useful, optionally in combination with one or a plurality of the other incompatible polymers identified above, preferably selected from polyolefins. This combination has excellent splittability. The combination of polyethylene terephthalate and polyamide 6 or of polyethylene terephthalate and polyamide 66 are very particularly preferred.

[0039] For embodying an inventive microfiber nonwoven composite it is advantageous when at least one of the components used in the composite filaments of the layer S is also used as a raw material for producing the melt-blown fibers of the layer M.

[0040] In order to obtain a high-strength nonwoven composite, the composite filaments of the layer S may also have a latent or spontaneous crimping that results from an asymmetrical structure of the elementary filaments relative to their longitudinal center axis, wherein this crimping may also be activated or reinforced by an asymmetrical, geometric embodiment of the cross section of the composite filaments. In this way the nonwoven fabric may be provided substantial thickness, a low modulus, and/or a multiaxial elasticity.

[0041] In one variant, the composite filaments of the layer S may have a latent or spontaneous crimping that derives from differentiation of the physical properties of the polymer substances forming the elementary filaments in the spinning, cooling, and/or drafting processes relating to the composite filaments that lead to twists that are caused by internal unsymmetrical loads relative to the longitudinal center axis of the composite filaments, wherein the crimping may optionally be activated or reinforced using an asymmetrical geometric embodiment of the cross section of the composite filaments.

[0042] The composite filaments may have a latent crimping that is activated, prior to formation of the nonwoven composite, by a thermal, mechanical, or chemical treatment.

[0043] According to one preferred embodiment of the invention, the composite filaments are dyed using spin dyeing.

[0044] According to the invention, the second fiber component has melt-blown fibers. The term melt-blown fibers according to the invention shall be construed to mean fibers that are produced by extruding a molten thermoplastic material through a plurality of fine, normally circular, nozzle capillaries as molten fibers into a high velocity gas (air, for example). The diameter of the fibers is reduced using this procedure. Then the melt-blown fibers are carried by the high velocity gas flow and deposited on a collecting surface in order to form a nonwoven fabric from randomly distributed fibers. The melt-blown method is well known and described in various patents and publications, for example NRL Report 4364, "Herstellung von superfeinen organischen Fasern [Production of superfine organic fibers]" by V. A. Wendt, E. L. Boone and C. D. Fluharty; NRL Report 5265, "eine verbesserte Vorrichtung fur die Bildung von superfeinen Thermoplastic Fibers [An Improved Apparatus for Forming Superfine Thermplastic Fibers]" by K. D. Lawrence, R. T. Lukas, and J.A. Junge, and U.S. Pat. No. 3,849,241, issued on Nov. 19, 1974 to Buntin, et al. These publications are hereby included by reference.

[0045] In another preferred embodiment of the invention, the melt-blown fibers are formed from polymers selected from the group comprising: polyesters, polyolefins, polyamides, polyurethanes, copolymers and/or mixtures thereof.

[0046] In one particularly preferred embodiment of the invention, a thermoplastic, spinnable or injection-moldable raw material, especially selected from polyolefins, copolyolefins, polyesters, copolyesters, polyurethanes, 1 polyamides, and/or copolyamides having an MFI (melt flow index) ISO 1133 of 100 to 3000 g/10 awn, is used as the raw material for the melt-blown fibers.

[0047] Due to the low viscosity of the raw material of the melt-blown fibers to be produced, filaments having very low titers may be produced with corresponding processing conditions. This facilitates the mixing of the layers during the splitting process, so that undesired delamination may be prevented between the layers and thus composites having high mechanical strength are created.

[0048] In another preferred embodiment of the invention, the melt-blown fibers have a fiber titer of 0.5 .mu.m to 5 .mu.m, preferably 1.0 .mu.m to 4 .mu.m, in particular 1.8 .mu.m to 3.6 .mu.m. It is an advantage of this embodiment that it is possible to produce a particularly homogenous composite nonwoven, with respect to the pore size distribution, because faults in the layer S may be filled in with melt-blown fibers of a compatible embodiment. When using the microfiber nonwoven composite as filter material this leads to particularly good fraction filtration efficiency of particles in the range of 0.5 .mu.m to 10 .mu.m.

[0049] The portion of the melt-blown fibers in the microfiber nonwoven composite is preferably at least 20 wt. %, more preferably 40 wt. % to 60 wt. %, in particular 45 wt. % to 55 wt. %, relative to the total weight of the microfiber nonwoven composite.

[0050] It is possible for the at least one layer S and/or M to have other components, for example other fibers, in addition to the specific fiber components (split fibers and/or melt-blown fibers). It is also possible for the microfiber nonwoven composite to be constructed from more than two layers, for example with the additional use of another layer S and/or M, staple fiber nonwovens, and/or other non-textile fabrics. Thus, for example, the microfiber nonwoven composite according to the invention may have, in addition to the layers S and M, at least one further layer C that contains, for example, staple fibers and/or continuous fibers (filaments), containing preferably synthetic fibers such as, for example, aramide fibers and/or natural fibers, or even more preferably comprising the aforesaid fibers. In one preferred embodiment of the invention, the fibers and/or filaments of layers S, M, and/or C mutually penetrate one another, at least in part.

[0051] The at least one additional layer C advantageously forms one and/or both outer layers of the microfiber nonwoven composite.

[0052] Due to the integration of additional layers C, other functionalities that permit, e.g., a progressive structure or flame-retardant surfaces may be generated depending on size, type, and raw material used in the fiber components.

[0053] It is also possible for the at least one additional layer C to be embodied as a reinforcing layer, for instance in the form of a scrim, and/or for it to comprise woven fabric, knit fabric, and/or interlaid scrim. It is in principle possible for the at least one additional layer C to form the outer layer(s) of the nonwoven fabric. The at least one additional layer C is advantageously arranged such that a progressive structure, relative to the fiber fineness, is created in the cross section of the microfiber nonwoven composite. Because of this, the different fiber cross sections/thicknesses may gradually transition into one another.

[0054] The polymers used for producing the filaments of the nonwoven composite may contain at least one additive, selected from the group comprising dye pigments, antistatic agents, antimicrobial agents such as copper, silver, or gold, or hydrophilization or hydrophobization additives in a quantity of 150 ppm to 10 wt. %. The use of these aforesaid additives in the polymers used permits adjustment to customer-specific requirements.

[0055] The mass per unit area of the inventive nonwoven composite is adjusted as a function of the desired application purpose. Mass per unit area, measured according to DIN EN 29073, in the range of 40 g/m.sup.2 to 300 g/m.sup.2, preferably 50 g/m.sup.2 to 150 g/m.sup.2, and in particular 70 g/m.sup.2 to 130 g/m.sup.2, have proved useful for many applications. For the layer S, the mass per unit area of 30 g/m.sup.2 to 250 g/m.sup.2, preferably 40 g/m.sup.2 to 100 g/m.sup.2, and/or for layer M the mass per unit area of 10 g/m.sup.2 to 100 g/m.sup.2, preferably 20 g/m.sup.2 to 60 g/m.sup.2, is advantageous.

[0056] The nonwoven composite also preferably has a thickness according to DIN EN ISO 9073-2 of 0.1 mm to 3.0 mm, preferably 0.15 mm to 2.5 mm, in particular 0.2 mm to 2 mm.

[0057] The nonwoven composite also preferably has a sound absorption rating (1000 Hz) of greater than 0.4, for example 0.4 to 0.8 and/or greater than 0.5, for example 0.5 to 0.7, and/or greater than 0.6, for example 0.6 to 0.7, specifically preferably at a mass per unit area of less than 150 g/m.sup.2, more preferably less than 130 g/m.sup.2, in particular less than 100 g/m.sup.2.

[0058] The nonwoven composite likewise preferably has a sound absorption rating (2000 Hz) of greater than 0.8, for example 0.8 to 1.0, and/or of greater than 0.85, for example 0.85 to 1.0, and/or of greater than 0.9, for example 0.9 to 1.0, specifically preferably at a mass per unit area of less than 150 g/m.sup.2, more preferably less than 130 g/m.sup.2, in particular less than 100 g/m.sup.2.

[0059] The nonwoven composite likewise preferably has a sound absorption rating (3000 Hz) of greater than 0.8, for example 0.8 to 1.0, and/or of greater than 0.85, for example 0.85 to 1.0, and/or of greater than 0.9, for example 0.9 to 1.0, specifically preferably at a mass per unit area of less than 150 g/m.sup.2, more preferably less than 130 g/m.sup.2, in particular less than 100 g/m.sup.2.

[0060] The nonwoven composite likewise preferably has a mean flow pore diameter of less than 20 .mu.m, for example 5 .mu.m to 20 .mu.m, more preferably of less than 18 .mu.m, for example 6 .mu.m to 18 .mu.m, and in particular of less than 17 .mu.m, for example 7 .mu.m to 17 .mu.m, specifically preferably at a mass per unit area of less than 200 g/m.sup.2, more preferably less than 150 g/m.sup.2, in particular less than 100 g/m.sup.2.

[0061] The nonwoven composite likewise preferably has a fraction filtration efficiency (particle size 1-4.7 mm) of greater than 60%, for example 60% to 100%, more preferably of greater than 75%, for example 75% to 100%, and in particular of greater than 90%, for example 90% to 100%.

[0062] The nonwoven composite likewise preferably has a fraction filtration efficiency (particle size>5 mm) of greater than 80%, for example 80% to 100%, more preferably of greater than 85%, for example 85% to 100%, and in particular of greater than 90%, for example 90% to 100%.

[0063] The nonwoven composite likewise preferably has a hot tensile elongation longitudinally (180.degree. C.) of greater than 50%, for example 50% to 85%, and/or 50% to 80%, more preferably of greater than 60%, for example 60% to 85% and/or 60% to 80%, and in particular of greater than 65%, for example 65% to 85% and/or 65% to 80%.

[0064] The nonwoven composite likewise preferably has a hot tensile elongation transversely (180.degree. C.) of greater than 55%, for example 55% to 95%, and/or 50% to 90%, more preferably of greater than 65%, for example 65% to 95% and/or 65% to 90%, and in particular of greater than 75%, for example 75% to 95% and/or 75% to 90%.

[0065] The nonwoven composite likewise preferably has three-dimensional deformability when hot (OTI Test, 160.degree. C.), determined as length to damage in cm, of at least 8 cm, for example 8 cm to 12 cm, preferably of at least 9 cm, for example 9 cm to 12 cm, more preferably of at least 10 cm, for example 10 cm to 12 cm.

[0066] Due to its specific properties, the inventive microfiber nonwoven composite is extremely suitable as a sound insulation layer and/or as a component of sound insulation layers, for example in the fields of construction and/or motor vehicles. It is also suitable as a barrier layer in home textiles (mite-proof products, anti-allergic bed linens, cleaning media), packaging materials, and filter medium.

[0067] In the method described in the following, the designators S' and M' refer to the layers that, following hydrofluid treatment, become corresponding layers S and M of the inventive microfiber nonwoven composite.

[0068] The invention furthermore comprises a method for producing the inventive microfiber nonwoven composite, comprising the following steps: [0069] Production and provision of at least one first layer S' that contains composite filaments melt-spun and deposited as a nonwoven fabric and/or of a composite nonwoven comprising the layer S' as surface layer; [0070] Application of at least one second layer M' that contains melt-blown fibers to the layer S' and/or to the side of the composite nonwoven that has the layer S' as surface layer, forming a composite nonwoven having the layers S' and M', and/or, [0071] Application of at least one composite nonwoven comprising the layer M' as surface layer to the layer S' and/or to the side of the composite nonwoven that has the layer S' as surface layer, specifically such that M' and S' form adjacent layers while embodying a composite nonwoven having the layers S' and M'; [0072] Hydrofluid treatment of the composite nonwoven having the layers S' and M', so that the composite filaments of the first layer S' are at least partially split and simultaneously solidified as elementary filaments having an average titer of less than 1 dtex and are bonded to the melt-blown fibers of the second layer M' to form a combined layer, and wherein the melt-blown fibers of the layer M' penetrate at least partially into the layer S'.

[0073] For producing the first layer S', the composite filaments may be deposited for instance using mechanical and/or pneumatic deflection, wherein at least two of these types of deflection may be combined, as well as using spin-drying onto a continuous conveyor belt. According to one preferred embodiment of the invention, the composite filaments are dyed using spin dyeing.

[0074] The layer S' may be presolidified, for example using mechanical solidification, such as in particular needle punching and/or thermofusion, such as in particular calendering. In this variant, presolidification of the first layer may occur prior to the targeted separation of the uniform composite filaments into elementary filaments.

[0075] Instead of the first layer S', it is also possible to use a composite nonwoven that comprises at least one other layer and the layer S' as surface layer. The at least one other layer of the composite nonwoven is advantageously the other layer C described in relation to the inventive nonwoven composite. The connection between the first layer S' and the at least one additional layer may occur in a conventional manner, for example by means of sewing, joining, gluing.

[0076] In the next step, a layer M' that contains the melt-blown fibers is applied to the layer S' and/or to the side of the composite nonwoven that has the layer S' as surface layer, forming a composite nonwoven having the layers S' and M'.

[0077] Alternatively, a composite nonwoven comprising the layer M' as surface layer may be applied to the layer S' and or to the side of a composite nonwoven that has at least one other layer and the layer S' as surface layer. The at least one additional layer of the composite nonwoven is advantageously the other layer C, described in relation to the inventive nonwoven composite. The application is conducted such that M' and S' form adjacent layers, while embodying a composite nonwoven having the layers S' and M'.

[0078] The step of applying layers according to the invention shall be construed to mean that the latter are arranged on one another in a prefabricated form and/or that at least one layer is produced directly on another, for instance by melt spinning. The layer M' preferably has a thickness according to DIN EN ISO 9073-2 of 0.1 mm to 0.4 mm, preferably 0.15 mm to 0.30 mm.

[0079] The layer containing the melt-blown fibers may be produced in a conventional manner, for example by extruding a molten thermoplastic material using a plurality of fine, preferably circular nozzle capillaries as molten fibers in a high-speed gas (preferably air). The diameter of the fibers may be reduced using this process. Then the melt-blown fibers may be carried by the high-speed gas flow and deposited on the first layer S' to form the combined layer.

[0080] It is likewise possible to add the at least one other layer C separately to the microfiber nonwoven composite. To this end, prior to the hydrofluid treatment, the at least one layer C is advantageously applied to the layers S', M' and or to a composite nonwoven having the layers S' and M' such that the at least one layer C is one and/or both outer layers of the formed composite nonwoven.

[0081] The composite nonwoven having the layers S' and M' is then subjected to a hydrofluid treatment in which the composite filaments are at least partially split and at the same time solidified to form elementary filaments having an average titer of less than 1 dtex and are bonded to the melt-blown fibers, wherein the fiber components of the layer M' penetrate at least partially into the layer S'.

[0082] The hydrofluid treatment of the combined layer advantageously occurs in that the possibly presolidified combined layer is acted upon, at least once on each side, with high-pressure fluid jets, preferably with high-pressure water jets. This can obtain a nonwoven composite according to the invention having suitable porosity properties and uniformity, and this can also make it possible to adjust the degree of splitting of the composite filaments in a targeted manner.

[0083] In this step, water jet pressures of 150 bar to 250 bar, preferably 200 bar to 220 bar, have proved particularly favorable.

[0084] As explained in the foregoing, to facilitate separation into the elementary filaments, the composite filaments may have a center opening, in particular in the form of a tube-shaped longitudinal hollow space that may be centered relative to the center axis of the composite filaments. This arrangement permits close contact between the elementary filaments, which are formed by the inner angles of the gaps or circular cut-outs prior to separation of the elementary filaments, and reduces or avoids contact in this region of different elementary fibers produced from the same polymer.

[0085] The strength and the mechanical resistance of the nonwoven composite may additionally be significantly increased if it is provided that the elementary filaments are bonded to one another using thermofusion.

[0086] This thermofusion may be conducted with the composite layer after the hydrofluid treatment.

[0087] In one preferred embodiment for producing the inventive microfiber nonwoven composite, the layer S' and/or a composite nonwoven including the layer S' as surface layer is solidified using thermofusion prior to the hydrofluid treatment.

[0088] By prefixing the composite filaments, the pressure to be used during the hydrofluid treatment may thereby be reduced.

[0089] The thermofusion may be conducted in a conventional manner, for example using heat calendering with heated, smooth, or engraved rollers (calendering), by passing through a hot-air tunnel furnace, and or by passing through a drum through which hot air flows.

[0090] Alternatively or in addition to the thermofusion, there may be bonding of the nonwoven composite and/or of the layer S' separately by applying a bonding agent contained in a dispersion or in a solution or by applying a powder bonding agent.

[0091] Furthermore, the combined layer may also be solidified using a chemical treatment (such as is described, for example, in the French patent no. 2 546 536 by the applicant) and/or using a thermal treatment that leads to controlled shrinkage of at least some of the elementary filaments following any separation of the latter. This results in shrinkage in the width and/or length of the substance.

[0092] Furthermore, after the hydrofluid treatment, the combined layer may be subjected to chemical bonding or conditioning, such as, for example, an anti-pilling treatment, hydrophilization or hydrophobization, an anti-static treatment, treatment for enhancing fire resistance, and/or to modification of tactile properties or sheen, mechanical treatment such as roughening, sanforizing, emerizing, or treatment in the tumbler, and/or treatment for altering appearance, such as dyeing or printing.

[0093] To increase its abrasion resistance, the combined layer is advantageously subjected to further calendering after the hydrofluid treatment. In addition, the split and solidified nonwoven composite is guided through heated rollers, of which at least one roller may also have elevations that can lead to point-like fusing of the filaments to one another.

[0094] The following measuring methods were used for determining the parameters found in this invention: [0095] I. Mass per unit area (g/m.sup.2): EN 29073 [0096] II. Thickness (mm): DIN EN ISO 9073-2, weight 12.5 cN/cm, surface area 10 cm.sup.2 [0097] III. Air flow LD (1/m.sup.2sec): DIN EN ISO 9237, characteristic acoustic impedance afr calculated from LD according to (pressure [mbar]*1000/LD) in rayls [0098] IV. Tensile strength and elongation: EN 29073 T3 [0099] V. Hot tensile strength and elongation: EN 29073 T3, T=180.degree. C. [0100] VI. OTI test: [0101] In order to evaluate the deformation properties while hot (deep drawability), fixed specimens of the substrate are deformed in a simple test (OTI test) by means of a round stamp heated to 160.degree. C. (9 cm spherical diameter, absolute specimen size 24 cm diameter, freely deformable specimen size 20 cm). The distance covered to damage in cm, the force occurring at deformation of 5% and 9% in N, and the maximum force to be applied for deformation in N are used as measurement values for evaluating the material properties. A long distance covered at 160.degree. C. with corresponding (low) force consequently means positive deformation properties when heated (deep drawability). [0102] VII. Mean flow pore diameter (.mu.m): ASTM E 1294 (1989), specimen size 21 mm, test liquid Galden HT230, measurement at room temperature [0103] VIII. Fraction filtration efficiency: EN 1822-3 (2011), test dust according to ISO 12103-1 A2 [0104] Temperature 23.degree. C..+-.3.degree. C., rel. humidity 50%.+-.5%; flow rates 5 cm/sec and 50 cm/sec; specimen unwashed [0105] IX. Sound absorption rating: DIN EN ISO 10534-1: 2001-10; air space 30 mm [0106] MD=machine direction [0107] CD=cross direction [0108] SB=spunbond [0109] MF=microfiber

[0110] The invention shall be explained in greater detail in the following using several of examples.

EXAMPLE 1

Production of Inventive Microfiber Nonwoven Composites

[0111] Seven inventive microfiber nonwoven composites, as described in the following table, are produced.

TABLE-US-00001 TABLE 1 Microfiber nonwoven composites 1-7 (S' = layer, composite filaments; M' = layer, melt-blown filaments; C = layer, carded staple fibers; CK = layer, carded, thermally bonded staple fibers); x = number of layers used. Individual layer Weight [g/m.sup.2] 40 60 100 28 80 80 Polymer PET/PA PET/PA PET/PA PBT Aramide Aramide Fiber 16 PIE SB 16 PIE SB 16 PIE SB Melt-blown Card Card/Cal. MF MF layer composite composite S' S' S' M' C CK Type 1 x x SM 2 xx x SMS 3 xx xx SMMS 4 x x xx SMMS 5 x xx x SMMC 6 x xx x x CMMSCK 7 x xx xx CMMSC

[0112] As may be seen from the table above, microfiber nonwoven composites according to the invention may be produced starting from individual layers S', M', C and CK, as well as starting from composite nonwovens having the layers S', M', C and CK.

[0113] A wide variety of microfiber nonwoven composites having a wide variety of properties may be obtained by varying the type, number, and arrangement of the individual layers used.

EXAMPLE 2

Determination of Physical Textile Parameters of Microfiber Nonwoven Composites 1-7

[0114] Physical textile data of the 7 inventive microfiber nonwoven composites were determined and are listed in the table below.

TABLE-US-00002 TABLE 2 Physical textile description of exemplary embodiments 1-7; MF composite HZD HZD LD LD HZK HZK MD CD Weight 100 Pa/5 cm.sup.2 200 Pa/20 cm.sup.2 Thickness MD CD [%] [%] [g/m.sup.2] [l/m.sup.2sec] [l/m.sup.2sec] afr [mm] [N/50 mm] [N/50 mm] EN EN EN 29073 DIN EN ISO DIN EN ISO 200 Pa DIN EN ISO EN 29073 EN 29073 29073 29073 angel. 9237 9237 [rayls] 9073-2 T3 T3 T3 T3 1 70 289 454 440 0.39 127 85 51 60 2 111 86 195 1025 0.46 202 205 47 73 3 138 52 105 1904 0.55 273 185 52 67 4 207 29 61 3278 0.81 430 398 61 77 5 286 38 79 2531 1.16 742 460 52 65 6 256 39 76 2631 1.19 697 373 48 72 7 258 38 78 2564 1.23 678 361 49 68

[0115] Characteristic acoustic impedance of 1 rayl corresponds in SI units to 1 N s/m.sup.3.

[0116] The results of tests V-VI are provided in the table below:

TABLE-US-00003 TABLE 3 Hot tensile strength test of exemplary embodiments 1-4; modulus of elasticity at 180.degree. C. in direct comparison to individual layers based on conventional microfibers in the weight range of 40-100 g/m.sup.2. Deformation [%] at 180.degree. C. 3 5 10 15 20 30 3 5 10 15 20 30 Test EN 29 073 T3 Orientation MD CD Unit [N/50 mm] [N/50 mm] 1 5.0 6.9 11.2 16.2 21.4 32.5 3.0 3.6 6.1 8.4 11.7 19.7 2 10.2 13.8 22.2 30.7 39.8 60.0 4.2 5.7 9.8 14.5 20.5 34.3 3 12.8 16.8 26.8 37.2 47.7 70.5 4.4 5.9 10.9 15.6 21.8 36.8 4 21.6 30.7 50.8 71.6 93.4 141.6 8.9 12.4 21.3 31.7 43.3 141.6 MF 40 4.7 6.3 9.8 13.5 17.4 25.8 2.6 3.0 4.2 5.6 7.5 12.1 MF 60 7.1 9.8 15.4 21.0 27.1 40.1 3.8 4.7 7.1 9.9 13.3 22.0 MF 80 9.2 12.7 19.4 26.3 33.8 50.2 4.4 5.7 8.7 12.2 16.5 27.7 MF 100 15.4 20.7 30.4 40.0 50.6 73.6 6.1 8.0 12.4 17.2 23.0 38.0

[0117] The materials MF (microfibers) listed for comparison in Tables 3, 4 and 5 are the individual layer S made of melt-spun composite filaments deposited to a nonwoven described with respect to the inventive microfiber nonwoven composite. The data provided are for this individual layer S following hydrofluid treatment.

TABLE-US-00004 TABLE 4 Hot tensile strength test/maximum tensile force and maximum tensile elongation of exemplary embodiments 1-4 at 180.degree. C. in direct comparison to individual layers based on conventional microfibers in the weight range of 40-100 g/m.sup.2. Hot tensile strength test @ 180.degree. C. Test HZK/HZD Orientation MD CD Unit [N/50 mm] [%] [N/50 mm] [%] 1 73.4 63.7 52.7 64.2 2 140.4 71.4 121.2 80.8 3 152.5 66.8 129.3 83.8 4 313.4 69.1 239.3 84.4 MF 40 42.8 50.5 29.5 61.9 MF 60 67.2 50.8 56.1 62.7 MF 80 94.8 56.8 82.4 68.6 MF 100 139.3 59.2 113.7 72.0

TABLE-US-00005 TABLE 5 OTI/Deformation test of exemplary embodiments 1-4 at 160.degree. C. in direct comparison to individual layers based on conventional microfibers in the weight range of 40-100 g/m.sup.2. Measurement variable OTI Test 160.degree. C. Orientation max. Force Path M 5 cm M 9 cm Unit [N] [cm] [N] [N] 1 570.4 10.2 76.7 429.8 2 975.5 10.0 99.2 742.6 3 1049.8 10.5 84.9 694.0 4 1840.7 10.3 154.3 1281.3 MF40 255.8 7.9 61.5 104.2 MF60 440.3 8.3 97.3 243.9 MF80 600.0 8.6 98.6 486.9 MF100 805.2 8.7 122.6 688.6

[0118] The results of tests VII-VIII are provided in the following tables:

TABLE-US-00006 TABLE 6 Determination of porosity properties of exemplary embodiments 1-4. Smallest Bubble Mean flow pore pore Largest pore Weight afr point diameter diameter diameter Number Composite [g/m.sup.2] [rayls] [.mu.m] [.mu.m] [.mu.m] [.mu.m] 1 SM 70 440 121 16.8 10.94 141.3 2 SMS 111 1025 47 9.3 6.55 50.5 3 SMMS 138 1904 36.8 7.3 5.26 41.6 4 SMMS 207 3278 22.9 7.3 2.65 24.4

TABLE-US-00007 TABLE 7 Pressure loss and fraction filter efficiency of exemplary embodiments 1-4 with particle sizes of 0.5, 1, 3, 5 and 10 .mu.m. Fraction filtration efficiency, new condition [%] .quadrature.p with particle size [.mu.m] Number [Pa] 0.5 1 3 5 10 1 21 67 72 86 91 94 2 60 94 96 99 >99.5 >99.5 3 90 97 98 >99.5 >99.5 >99.9 4 139 >99.5 >99.9 >99.9 >99.9 >99.9

TABLE-US-00008 TABLE 8 Filtration efficiency of exemplary embodiments 1-4 with particle sizes of 1 .mu.m-4.7 .mu.m and >5 .mu.m. Number 1 2 3 4 Efficiency 1-4.7 .mu.m [%] 72 96 98 >99.9 Efficiency >5 .mu.m [%] 91 99 99 >99.9

[0119] The results determined for fraction filtration efficiency indicate that the TUV Rheinland limits are maintained and the exemplary embodiments 1-4 in the unwashed state are suitable for producing anti-allergic bed linens.

[0120] FIGS. 1 and 2 provide the results of the hot tensile strength test for exemplary embodiment 1 in the longitudinal and transverse direction, as well as the determined modulus values at 180.degree. C. in direct comparison to individual layers based on conventional microfibers in the weight range of 40 and 60 g/m.sup.2.

[0121] FIG. 3 provides the sound absorption rating/impedance of exemplary embodiment 1 compared to the individual layers used in exemplary embodiment 1. It may be seen that the special combination of the split fibers with the melt-blown fibers is unexpectedly favorable, especially also in the context of sound absorption. In one inventive microfiber nonwoven composite SM, effect of split fibers and melt-blown fibers with respect to sound absorption is surprisingly synergistic. The sound absorption coefficient of the combined layer SM produced using hydrofluid treatment across the frequency range is significantly greater than the level expected from simply combining the starting materials or evaluating the air flow resistance to be measured (440 rayls for exemplary embodiment 1). This result is particularly surprising, since it was to be expected that the strong barrier effect generally produced by the melt-blown fibers would lead to a disproportionately high air flow resistance and thus would prove disadvantageous for producing a balanced sound absorption profile.

[0122] FIG. 4 illustrates the sound absorption rating/impedance of exemplary embodiment 1 compared to type S individual layers following hydrofluid treatment (MF=microfibers). As is clear from FIG. 4, the special combination of the split fibers with the melt-blown fibers proves unexpectedly favorable in terms of sound absorption. In one inventive microfiber nonwoven composite SM (base weight 70 g/m.sup.2), the effect of split fibers and melt-blown fibers in the base weights of 40 and 80 g/m.sup.2 with respect to sound absorption is surprisingly synergistic compared to nonwoven layers based purely on microfibers. The sound absorption coefficient of the combined layer SM produced using hydrofluid treatment at 70 g/m.sup.2 base weight is clearly greater than the level of the sound absorption coefficient of the nonwoven layer S based on the microfibers in the base weight of 80 g/m.sup.2.

[0123] The results determined with respect to sound absorption properties, especially taking into account material properties when loaded while hot, indicate that inventive microfiber nonwoven composites may be used very advantageously to produce acoustically effective components.

[0124] Without establishing a mechanism, it is presumed that the good performance of the inventive nonwoven fabric is attained by thorough mixing of the individual components.

[0125] FIG. 5 depicts a cross-sectional image, produced by raster electron microscope, of an inventive microfiber nonwoven composite comprising a layer S, a layer M, and a layer C (staple fibers). Thorough mixing of all three layers is clearly evident.

[0126] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.

[0127] The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article "a" or "the" in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of "or" should be interpreted as being inclusive, such that the recitation of "A or B" is not exclusive of "A and B," unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of "at least one of A, B and C" should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of "A, B and/or C" or "at least one of A, B or C" should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

Claims

1. A microfiber nonwoven composite, comprising: at least one layer S that contains a first fiber component; and at least one layer M that contains a second fiber component, wherein the second fiber component is forced at least in part into the layer S, wherein fibers of the first fiber component comprise melt-spun composite filaments deposited as a nonwoven fabric, and which are at least partially split and solidified to form elementary filaments having an average titer of less than 1 dtex, wherein fibers of the second fiber component comprise melt-blown fibers.

2. The microfiber nonwoven composite according to claim 1, wherein the microfiber nonwoven composite has an average pore diameter of less than 20 .mu.m and/or a smallest pore diameter of less than 11 .mu.m.

3. The microfiber nonwoven composite according to claim 1, wherein the first fiber component is at least partially penetrated into the layer M.

4. The microfiber nonwoven composite according to claim 2, wherein the at least partial penetration of the second fiber component into the layer S and/or of the first fiber component into the layer M is by hydrofluid treatment.

5. The microfiber nonwoven composite according to claim 1, wherein a titer of the elementary filaments is from 0.01 dtex to 0.8 dtex.

6. The microfiber nonwoven composite according to claim 1, wherein a portion of the elementary filaments of the first fiber component is at least 20 wt. % relative to a total weight of the nonwoven fabric.

7. The microfiber nonwoven composite according to claim 1, wherein the melt-blown fibers are formed from polymers having an MFI according to ISO 1133 of 100 to 3000 g/10 min.

8. The microfiber nonwoven composite according claim 1, wherein the melt-blown fibers have a fiber titer of 0.5 .mu.m to 5 .mu.m.

9. The microfiber nonwoven composite according to claim 1, wherein a portion of melt-blown fibers in the microfiber nonwoven composite is at least 20 wt. % relative to a total weight of the microfiber nonwoven composite.

10. The microfiber nonwoven composite according to claim 1, further comprising at least one other layer C that contains staple fibers and/or filaments, wherein the fibers and/or filaments of the layers S, M, and/or C at least partially penetrate one another.

11. The microfiber nonwoven composite according to claim 1, wherein the microfiber nonwoven composite has a sound absorption rating (1000 Hz) of greater than 0.4 and/or a sound absorption rating (2000 Hz) of greater than 0.8 and/or a sound absorption rating (2000 Hz) of greater than 0.8, with a mass per unit area of less than 150 g/m.sup.2.

12. The microfiber nonwoven composite according to claim 1, wherein the microfiber nonwoven composite has a mean flow pore diameter of less than 20 .mu.m with a mass per unit area of less than 200 g/m.sup.2.

13. The microfiber nonwoven composite according to claim 1, wherein the microfiber nonwoven composite has a fraction filtration efficiency (particle size 1-4.7 mm) of greater than 60% and/or a fraction filtration efficiency (particle size>5 mm) of greater than 80.

14. A method for producing the microfiber nonwoven composite according to claim 1, comprising the following steps: providing at least one first layer S' that contains composite filaments melt-spun and deposited as a nonwoven fabric and/or providing a composite nonwoven comprising the layer S' as surface layer; applying at least one second layer M' that contains melt-blown fibers to the layer S' and/or to a side of the composite nonwoven that has the layer S' as surface layer so as to form a composite nonwoven having the layers S' and M'; and/or applying at least one composite nonwoven comprising the layer M' as surface layer to the layer S' and/or to a side of the composite nonwoven that has the layer S' as surface layer such that M' and S' form adjacent layers while embodying a composite nonwoven having the layers S' and M'; performing a hydrofluid treatment of the composite nonwoven having the layers S' and M' such that the composite filaments of the first layer S' are at least partially split and simultaneously solidified as elementary filaments having an average titer of less than 1 dtex and are bonded to the melt-blown fibers of the second layer M' to form a combined layer, wherein the melt-blown fibers of the layer M' penetrate at least partially into the layer S'.

15. Use of the microfiber nonwoven composite according to claim 1 as a sound insulation layer and/or as a component of sound insulation layers, as a barrier layer in home textiles, as packaging materials, and/or as filter medium.

16. The microfiber nonwoven composite according to claim 4, wherein the hydrofluid treatment comprises hydraulic entanglement.

17. The microfiber nonwoven composite according claim 8 wherein the fiber titer is 1.0 .mu.m to 4 .mu.m.

18. The microfiber nonwoven composite according claim 17 wherein the fiber titer is 1.8 .mu.m to 3.6 .mu.m.

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