Protective Vent and Method for Producing a Protective Vent

Abstract

The invention relates to a composite for a protective vent with at least one carrier layer and an electrospinning membrane, which is arranged on the at least one carrier layer, wherein the electrospinning membrane consists of superimposed fibers lying one above the other, forming a porous structure, whereby the porous structure is designed, whereby the carrier layer comprises a monofilament fabric, a plasma coating is applied both to the electrospinning membrane and to the monofilament fabric of the at least one carrier layer and a bonding is provided that connects the carrier layer and the membrane. Furthermore, the invention relates to an according method for producing the inventive protective vent.

Claims

1. Protective vent comprising at least one carrier layer (11, 15) and an electrospinning membrane (12) which is arranged on the at least one carrier layer (11, 15), wherein the electrospinning membrane (12) is formed from fibers lying one above the other, forming a pore structure, whereby the pore structure is designed, characterized in that the carrier layer (11, 15) comprises a monofilament fabric, a plasma coating (14) is applied both to the electrospinning membrane (12) and to the monofilament fabric of the at least one carrier layer (11, 15), and a bonding is provided that connects the carrier layer and the membrane.

2. Protective vent according to claim 1, characterized in that the membrane (10) is provided with the plasma coating (14) according to the PECVD method.

3. Protective vent according to claim 1 or 2, characterized in that the plasma coating (14) is formed from a material with hydrophobic and/or oleophobic properties.

4. Protective vent according to claim 3, characterized in that the material comprises at least saturated, mono- and/or polyunsaturated ethers, ketones, aldehydes, alkenes, alkynes, amides, amines, nitriles, thioethers, carboxylic esters, thioestheses, sulphones, thioketones, thioaldyhydes, sulfenes, sulfenamides, fluoroacrylates, siloxanes, epoxides, urethanes, acrylates, polyamide 6 (PA6), polyamide 6,6 (PA66), aliphatic polyamide, aromatic polyamide polyurethane (PU), poly(urea urethane), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polylactide (PLA), polycarbonate (PC), polybenzimidazole (PBI), polyethylenoxide (PEO), polyethylenterephthalate (PET), poly(butylene terephthalate), polysulfone (PS), polyvinylchloride (PVC), cellulose, cellulose acetate (CA), polyethylene (PE), polypropylene (PP), PVA/silica, PAN/TiO.sub.2, PETFE polyetherimide, polyaniline, poly(ethylene naphthalate), styrenebutadiene rubber, polystyrene, poly(vinyl alcohol), poly(vinylidene fuoride), poly(vinyl butylene), polymethylmethacrylate (PMMA), copolymers, derivative compounds and blends and/or combinations thereof.

5. Protective vent according to one of claims 1 to 4, characterized in that the carrier layer (11, 15) is fixedly connected to the membrane (12).

6. Protective vent according to one of claims 1 to 5, characterized in that the membrane (12) is arranged between two carrier layers (11, 15).

7. Protective vent according to one of claims 1 to 6, characterized in that the membrane (12) is formed with a maximum pore size of about 0.10 m to 1.0 m.

8. Protective vent according to one of the claims 1 to 7, characterized in that the membrane (12) is formed as a barrier against the penetration of microorganisms.

9. Bedding product, characterized in that at least one protective vent according to one of the claims 1 to 8 is provided.

10. Electronic or electrical appliance with a housing, characterized in that at least one protective vent according to one of the claims 1 to 8 is provided.

11. Method for producing a protective vent as claimed in one of the claims 1 to 8, wherein a carrier layer (11, 15) is provided, and a membrane (12) is arranged on the carrier layer (11, 15), the membrane (12) being produced by the electrospinning method from superimposed fibers having a porous structure, wherein the carrier layer and the membrane form a protective vent membrane characterized in that a monofilament fabric is provided as the carrier layer (11, 15), the protective vent membrane (10) is treated by a plasma coating process, wherein a surface coating (14) is applied both to the carrier layer (11, 15) with the monofilament fabric and to the electrospinning membrane (12), and the protective vent membrane is furnished with a bonding connecting the carrier layer and the membrane.

12. The method according to claim 11, characterized in that the membrane (12) is firmly bonded to the carrier layer (11, 15) by means of a hot-melt process, in particular by means of a laser, by ultrasonic, by lamination, by gluing or by a combination thereof.

13. The method according to claim 12, characterized in that the electrospinning membrane (12) is produced directly on the carrier layer (11, 15), the membrane (12) being fixedly connected to the carrier layer (11, 15).

14. The method as claimed in one of claims 10 to 13, characterized in that at least one additional carrier layer is provided, which is also connected to the membrane, wherein the membrane is arranged between the carrier layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] In the drawings:

[0084] FIG. 1 shows a schematic cross-sectional representation of a protective vent according to the invention in its simplest embodiment (single layer),

[0085] FIG. 2 shows a schematic cross-sectional representation of the protective vent according to the invention in the so-called sandwich arrangement,

[0086] FIG. 3 shows a schematic cross-sectional representation of the protective vent according to the invention with a multi-layer construction,

[0087] FIG. 4 shows a schematic cross-sectional representation of the protective vent according to the invention in a hybrid arrangement with two different carrier layers,

[0088] FIGS. 5-8 show SEM-images of the protective vent, and

[0089] FIG. 9 shows a schematic drawing of a preferred method according to the invention.

[0090] FIG. 1 shows a cross-sectional view of the protective vent 10 according to the invention with a carrier layer 11. A membrane 12 is arranged on the carrier layer 11, which is formed according to the electrospinning method and is applied on the carrier layer 11. For an improved adhesion of the membrane layer 12 to the carrier layer 11, the protective vent can be formed with at least one connecting point 13, which connects the two layers to each other. This may be, in particular, a melting or gluing site in the form of points or lines. Due to the small layer thicknesses of the carrier material 11 as well as the membrane 12, the protective vent can be completely penetrated by the connecting point 13 at the connecting area. The protective vent 10, in particular the electrospinning membrane 12, can be formed with a porosity. The surface of the protective vent 10 as well as the fibers of the pores can be coated with a coating material, which is applied in particular by the plasma deposition method. The surface coating of the fibers is schematically illustrated in the figures by the points and lines 14. In accordance with the invention, the protective vent 10 can be completely surface-coated with the plasma polymer, meaning a coating of individual fibers and filaments of the membrane and the carrier layer. This may also comprise fibers of the region lying in the interior of the protective vent or a lower region within the pores of the membrane. Thus, not only the macroscopic outer surface of the protective vent can be coated but also the microscopic inner surface, i.e., for example, inner fibers, non-uniformities, wherein the individual fibers are encapsulated or covered with the coating material.

[0091] FIG. 2 shows the protective vent 10 according to the invention in a so-called sandwich arrangement. In this, the membrane 12 is arranged between two carrier layers 11, as a result of which the membrane layer 12 is protected, such that the resulting vent is capable of withstanding mechanical forces in application. In one embodiment of the sandwich arrangement, for example, an air permeability of 15.6 l/m.sup.2*s can be achieved. In principle, an air permeability of up to 50 l/m.sup.2*s can be achieved in the sandwich, multilayer or hybrid arrangement. In any possible arrangement of layers in a protective vent 10, these layers can be arranged one on top of the other by simple lamination. However, the layers can also be firmly connected to one another via connecting points 13, as a result of which a particularly reliable mechanical resilience of the protective vent 10 can be achieved.

[0092] FIG. 3 shows a multilayer arrangement of the protective vent 10 (multilayer). In this arrangement, alternating carrier layers 11 and membrane layers 12 are provided one above the other.

[0093] According to FIG. 3, two carrier layers 11 and two membrane layers 12 are provided. However, a multilayer arrangement can also have any number of carrier layers 11 and/or membrane layers 12. It is likewise possible to provide two membrane layers 12 directly one above the other between two or more carrier layers 11. Even in the case of a multilayer arrangement, the plasma coating can be provided preferably subsequent to the layer stacking on the microscopic surface of all superimposed membrane layers 12 and carrier layers 11. Accordingly, the plasma coating can also be provided on the inside surfaces of the protective vent 10 in the case of a multilayer construction.

[0094] FIG. 4 shows an embodiment of the protective vent 10 according to the invention in which the membrane layer 12 is arranged between a first carrier layer 11 and a second carrier layer 15. In principle, the first carrier layer 11 can in particular be designed as a fabric, whereas the second carrier layer 15 can differ from the first carrier layer 11 and, in particular, can be provided as a nonwoven material. With such a hybrid arrangement properties of different materials can advantageously be combined in the protective vent 10, whereby filter, protective and anti-biohazardous properties can be realized in an advantageous manner in the protective vent 10.

[0095] According to FIG. 4, a plasma coating can be provided on the entire surface of the protective vent 10, the plasma polymerization also taking place within the protective vent 10 in deeper layers. It is also conceivable to provide for a multilayer construction of the protective vent 10 with different carrier layers 11, 15 and differently designed membrane layers 12 e.g. with different pore size distribution.

[0096] In the following enclosed figures of scanning electron microscope (SEM) images of embodiments of the inventive protective vent are discussed (FIGS. 5 to 9). The terms symmetric and asymmetric refer to equal or different outer layers in a sandwich system.

[0097] In FIGS. 5 to 7 SEM images of embodiments 10-1, 14C and 17-2 of the protective vent are provided. Also in FIG. 8 SEM, pictures of commercial Gore membrane and electrospinning membrane are provided for comparison.

[0098] The SEM images show a top view of the protective vent as well as cross-section (side view). The magnification of the top (face/back) and cross-section views are 100 and 500, respectively.

[0099] In FIG. 5 (example 10-1), the face view is showing the carrier layer and the membrane layer whereby the back view is only showing the membrane layer from the other side. The face side of example 10-1 also shows the textile monofilament structure (plain weave) above the membrane structure. The cross-section view of example 10-1 shows the carrier layer arranged on top of the membrane (also two layers vent).

[0100] Example 14C (FIG. 6) shows a sandwich structure wherein the carrier layer is a woven monofilament textile structure (twill weave) above a membrane. The cross-section view shows a second outer layer below the membrane, the membrane being arranged between the woven carrier layer and the knitted carrier layer. The second outer layer (knitted fabric) differs in its structure from the carrier layer of the inventive protective vent.

[0101] Example 17-2 (FIG. 7) shows a monofilament textile structure (plain weave) above a membrane. The bonding points can also be seen in this example. From a side view (cross-section) it can be seen that the membrane is arranged between two equal outer layers thus, the second layer equals with a carrier layer whereby the membrane is arranged between the two layers (symmetric sandwich structure).

[0102] For comparison, SEM-images of Gore e-PTFE membrane and nanofiber web are provided (FIG. 8). The images show a structure which is different from the electrospinning membrane structure of single fibers lying on top of each other forming a 3D-network of high porosity with discrete fibers. Based on SEM images presented here it is also clear that a relatively large average pores are formed in e-PTFE membrane and these are mostly arranged in one direction and non-uniform.

Comparative ExampleBarrier Against Microorganisms

[0103] The results of the test as shown in Table 2 demonstrate that the inventive vent is an effective microbial barrier to a range of gram-positive and gram-negative motile. The vent maintained 100% patency after 4 and 24 hours. The vent prevented penetration of microorganisms into the agar. The inventive vent provided a 100% effective microbial barrier against Pseudomonas aeruginosa, Staphylococcus aureus (also called MRSA), Bacillus atropheaus and Bacteriophage FX174, as no penetration of the bacteria, viruses were obtained.

Comparative ExampleWater Column and Air Permeability

[0104] Table 3 illustrates the water tightness and air permeability of a mesh (woven monofilament) alone, a mesh layered with a membrane and a membrane layered mesh with a coating (inventive protective vent) as explained above. The material of the inventive protective vent (mesh+nanofiber web+PECVD) shows the best water tightness with a water column of 1609 cmwc, whereas uncoated vent shows very low water column of 8 cmwc. Nanofiber layer has strong influence on air permeability. Air permeability of face or backing materials has less influence on the air permeability of the whole composite but still material having very low air permeability causes low air permeability of the composite. The shape and size of the pores in nanofiber layer are not affected by the ultrathin coatings yielded by plasma polymerization. In contrast, many conventional wet-chemical coatings close up the open structure of the membrane and thus hinder any transport of air.

Comparative ExampleWater and Oil Repellency

[0105] Table 4 shows the table of the results of the water contact angle measurement according to DIN 55660-2:2011-12, oil repellency test according to DIN EN ISO 14419:2010, Federal German test according to ISO 9865:1991 and the (water) spray test according to DIN EN ISO 4920. A water contact angle greater than 130 is obtained on plasma-coated vent, whereas untreated samples show a water contact of less than 100. In the oil droplet tests, the oleophobicity of a surface is determined by means of the form of an oil droplet on the surface to be tested, using standardized oils (1 to 8, Table 4). Particularly oleophobic surfaces show a strong repellent behavior not only with the oils 1 to 5 but also with the oils 6, 7 and 8. The best result is shown in this test by the grade 8 (highest repellency effect). All the embodiments according to the invention have good (grade 6) to very good (grade 8) oleophobic properties. The examples according to the invention show an excellent water-repellent effect: the so-called lotus effect with best score (5 of 5) in the Bundesmann test and also the best grade (5 of 5) in the spray test.

Comparative ExampleProtection of Nanofibers and Composite Arrangement

[0106] Nanofibers, in particular PA6 nanofibers produced through electrospinning are very sensitive and they are mechanically weak. Therefore, it is important to protect nanofibers from destructive and harsh conditions during application. Abrasive force is an example can ablate nanofibers. Therefore, abrasion resistance is one of the limiting factors in determining the lifetime of a product. The applicant has long lasting experience in producing high strength monofilament fibers. Meshes made from those high strength monofilaments are the optimal candidates to make nanofibers composite for industrial applications and protect them from aggressive atmospheres.

[0107] It was found that while having similar filament strength if the fabric rigidity changes, the breaking force changes drastically. In case of plain weave, the floats are evenly distributed within the total fabric area, breaks occur in a localized manner. Elongation at break of densely woven mesh is generally greater than less dense mesh and in the same manner, as the rigidity of mesh increases, composite's elongation at break increases (data not shown).

Comparative ExampleAir Permeability and Calendering

[0108] Depending on the application the physical properties of nanofibers membrane such thickness, density, pore size and shape can be adjusted further by a calendering process, where the important parameters such as roller temperature, nip pressure, residence time (i.e. line speed) are to be considered to obtain required properties with a defined solidity. Furthermore, the properties of the carrier substrate may have affected by the calendering conditions used. For example, the air permeability is reduced by about 50% (example 10-1) by the calendering process i.e. high density nanofibers layer can be obtained through calendering of the final product.

Comparative ExampleFiltration Efficiency

[0109] The protective vent containing PA6 based nanofibers is proven to be very efficient up to 99.998% effective according to EN 149 in capturing and preventing particles as small as 0.30 microns (nom.). So far, no filter of this type has been invented. The best commercial HEPA filter (PTFE) has maximum efficiency of 99.97%. It is also shown that particles smaller (and larger) than 0.30 microns are trapped and captured by newly developed composite media (data are not shown). The applicant has made a notable advancement in reducing pressure drop and in operating at 100% efficiency on target contaminants. Depending on the application a good compromise on pressure drop and barrier against particle penetration can be obtained. The resistance to air flow for the product over the time in service is to be considered to extend the lifetime of the filter media. There are several key factors to optimize filter function with extended filter life: among others specific surface, symmetric and/asymmetric arrangement, gradient layer-structures etc.

Comparative ExampleWater Vapor Permeability

[0110] The RET (resistance-evaporation-transmission) value, measured according to ISO 11092, in Table 5 indicates the water vapor resistance of a composite, i.e. the lower the resistance, more breathable the composite vent. For example, RET<6=highly breathable and RET>20=non-breathable. Commercial ePTFE membrane has a RET value of between 3-6 is also shown in Table 5 for comparison. RET value also depends on many factors such as composite type, face and backing materials, nanofibers mat construction, porosity, air permeability, thickness of the composite, surface properties etc. An excellent vapor transfer rate up to RET value of 0.22 is obtained with PA6 based nanofibers vent.

TABLE-US-00001 TABLE 1 Tests for assessment of the properties of the inventive protective vent. Property Standard/Method Property Standard/Method Resistance to water ISO 811: 1981 Pore distribution & ASTM F316-03 penetration bubble point Air permeability ISO 9237: 1995-12 Breaking force max DIN EN ISO 13934 Microbial barrier test - Centexbel method Elongation at Break DIN EN ISO ambient pressure test 13934 Water contact angle DIN 55660-2: 2011- Mesh opening ASTM E11 12 warp/weft Water repellency DIN EN ISO Filament diameter ASTM E11 (Spray test) 4920: 2012 Water repellency ISO 9865: 1991 Open area ASTM E11 (Bundesmann test) Oil repellency DIN EN ISO Thickness ISO 5084 14419: 2010 Water vapor ISO 11092 Filtration efficiency EN 149 permeability

TABLE-US-00002 TABLE 2 Microbial penetration results towards Pseudomonas aeruginosa, MRSA, and Bacillus atrophaeus and viral penetration results towards Bateriophage X174 with 2 different contact times (4 hours and 24 hours) and (each). Controls results are not shown here: growth was observed for positive controls and no growth (no plaques of lysis for Bacteriophage X174) was observed for negative controls for each stain. Medium Sample Contact Replicate Growth growth promotion reference time no. observation ability check Example 14C 4 hours 1 No growth (both face 2 No growth and back 3 No growth sides) 4 No growth 5 No growth 24 hours 1 No growth 2 No growth 3 No growth 4 No growth 5 No growth = growth observed when nutritive agar medium (for which no strike-through has been observed) is inoculated with the tested microorganism. The concentrations of the Pseudomonas aeruginosa, MRSA, Bacillus atrophaeus spores and Bacteriophage suspension are 1.6 10.sup.7 CFU/ml, 9.8 10.sup.6 CFU/ml, 5.1 10.sup.6 spores/ml and 1.2 10.sup.6 CFU/ml, respectively.

TABLE-US-00003 TABLE 3 Water tightness and air permeability of the protective vent (mesh + nanofiber web + PECVD) as well as comparable material without coating and without coating and without mesh (monofilament fabric). Water column Sample (cmwc) Air permeability (l .Math. m.sup.2/s) Mesh (3A07-0005-115-12) 0 67 Mesh + nanofiber web 8 12 Mesh + nanofiber web + 1609 12 PECVD

TABLE-US-00004 TABLE 4 Water and oil repellency of the protective vent. Lotus Protective vent Contact angle () Oil grade effect Spray grade Example 1 face 131.9 1.7 7 5 5 back n/a 7 5 5 Example 2 face 130.5 1.0 6 5 5 back n/a 6 5 5 Example 3 face 135.7 2.1 7 5 5 back n/a 7 5 5 Example 4 face 139.4 1.6 8 5 5 back n/a 7 5 5 Example 5 face 133.4 3.0 7 5 5 back n/a 7 5 5 Example 6 face 132.8 1.6 7 5 5 back n/a 7 5 5

TABLE-US-00005 TABLE 5 Water vapor permeability of the protective vent. Water vapor permeability, Example RET [Pa * m.sup.2 * W.sup.1] Commercial membrane 3-6 e.g. ePTFE 10A 3.18 10C 2.60 14C 1.30 9 0.40 17-2 0.78 10-1 0.22 17-2 CA 0.80 10-1 CA 0.32