Face mask with filter medium from multicomponent

Abstract

This invention relates to a face shield for preventing the transmission of infectious agents, comprising a filter medium made of a spun nonwoven fabric, the spun nonwoven fabric being composed of multi-component filaments at least partially split into basic filaments, wherein optionally at least one additional layer not being a filter medium is present. The invention also relates to the use of filter masks and face shields.

Description

[Technical Field]

[0001] This invention relates to a face mask having a filter medium made of multi-component filaments and its use therein. [Previous Technology]

[0002] Various types of face shields can be used for respiratory protection. Filtering half-face shields (FFPs) are items of personal protective equipment (PPE) and are intended to protect the wearer from particulate and aerosol damage. The design of filtering half-face shields has evolved. Masks can be used with or without exhalation valves. Masks without valves filter both incoming and outgoing air, thus providing protection for the wearer and others. Masks with valves filter only incoming air and are therefore not designed to protect others. The performance and requirements for filtering half-face shields are defined in the standard DIN EN149:2001-10.

[0003] Medical face shields (nose and mouth protection devices, MNPs, face shields, mouth protection devices, surgical masks) are primarily used to protect others from potential infectious aerosols from people wearing the shield. When tightly fitted, medical face shields can also provide protection for the wearer; however, this is not the primary purpose of a mask. Standard DIN EN 14683:2019 relates to medical half-face shields. Medical half-face shields are used not only in medical applications but also in everyday life. Patients and others can wear medical masks to reduce the risk of spreading infection, especially in the event of an epidemic or pandemic. Medical face shields are crucial for healthcare workers and the public in combating COVID-19, the disease caused by the coronavirus SARS-CoV2.

[0004] In the prior art, medical face masks typically have a three-layer structure. Medical face masks often include a support layer made of spun nonwoven polypropylene, a central electrostatically charged filter layer made of meltblown microfibers, and a cover layer made of spun nonwoven polypropylene. Only the media filter layer, characterized by very fine meltblown microfibers, contributes to aerosol removal. The support layer faces the mouth and provides only mechanical protection. The outer cover layer also provides mechanical protection for the filter layer. It is common practice to charge the filter layer to improve filtration efficiency.

[0005] The filtration efficiency of the filter layer limits the performance level and pressure drop / breathing resistance of the mask.

[0006] DIN EN 14683:2019 defines the following different performance grades:

[0007]

[0008] This standard recommends that Type I medical face shields should be used only by patients and others to reduce the risk of spreading infection, especially in the event of an epidemic or pandemic. Type I masks are not intended for use by medical personnel in operating rooms or other medical facilities with similar requirements.

[0009] Ordinary face shields have various drawbacks. Especially given the COVID-19 pandemic, there remains a great need to provide healthcare workers, those in close contact with others, and the general public with face shields that are highly efficient, comfortable to wear, and inexpensive and readily available. Generally, the contradictory performance of filtration efficiency versus breathability in known masks can still be improved. Another known problem is that highly efficient masks are typically only usable once, as washing reduces their effectiveness. This problem is particularly pronounced for electrically charged filters or those comprising very fine meltblown fibers.

[0010] Nonwoven fabrics spun from split multicomponent filaments are known in the art. They are supplied by Freudenberg, DE, under the trademark Evolon, for a variety of applications, and are described, for example, in EP 3 165 655 B1 or DE 10 2004 036 099 A1.

[0011] US 2018 / 0361295 A1 relates to a filter element including a housing in which a filter medium is inserted and which is attached to and sealed to the housing on multiple sides.

[0012] US 5817584 relates to a face mask fabric in which a first layer consists of thermally bonded multicomponent filaments and a second layer includes additional microfibers, particularly meltblown fibers. [Summary of the Invention]

[0013] The object of the present invention is to provide a face shield for preventing infection, which overcomes the aforementioned disadvantages. In particular, a face shield that can be easily and readily obtained in a simple manner should be provided. The face shield should have high filtration efficiency and provide high comfort to the user, and its breathability should be high so as to reduce breathing resistance. Preferably, the face shield should be reusable and washable without reducing its filtration performance.

[0014] Surprisingly, the fundamental problem of the present invention is solved by the face mask and its use as described in the claim. The subject of the present invention is a face mask for preventing the transmission of infectious agents, having a filter medium made of a spun nonwoven fabric composed of multi-component filaments, said multi-component filaments being at least partially split into basic filaments, wherein the face mask optionally includes at least one additional layer that is not a filter medium.

[0015] A face shield is a mask that covers the mouth and nose to provide a barrier against the direct transmission of infectious agents. Such face shields are also known as medical masks or surgical masks. Typically, these are half-face shields.

[0016] The face mask should protect the wearer and / or others from infectious agents. Infectious agents are usually pathogens, generally bacteria or viruses. Typically, such face masks filter aerosol particles from the breathing air. Aerosols are typically suspensions of liquid particles (droplets) or fine solid particles in air or other gases. Particle diameters are typically in the range of 0.1 μm to 10 μm. Breathed air may include liquid aerosol particles, usually in the form of droplets, which may contain infectious agents. Aerosols can be released from a person's mouth, for example, during speaking, breathing, or sneezing.

[0017] The mask includes a filter medium. The term "filter medium" refers to the portion of the mask that mechanically or physically separates or removes aerosol particles in liquid or solid form from inhaled or exhaled air. The filter medium is a planar layer through which breathing air passes, thereby removing unwanted components from the breathing air.

[0018] The filter medium is composed of a spun nonwoven fabric. The spun nonwoven fabric is composed of multi-component filaments, which are at least partially split into basic filaments. The filter medium may include two or more layers of spun nonwoven fabric. The mask does not include other additional filter media. Optionally, the mask may include an additional flat layer that is not a filter medium but is also traversed by breathing air. Preferably, such a layer is a support layer or a cover layer. Overall, the mask is characterized in that the filter medium is structured in a simple manner and can be obtained in a simple manner because the filter medium consists of only one type of spun nonwoven fabric.

[0019] Surprisingly, it has been found that the face mask of the present invention, having a filter medium made of a spun nonwoven fabric derived from split multicomponent filaments, can combine high filtration efficiency with high breathability. This is advantageous because it is generally difficult to reconcile these opposing parameters. It is generally observed in the art that if the air permeability is relatively high, the filtration efficiency of the fibrous material tends to be relatively low, and vice versa. The advantages of the present invention are achieved although the filter medium does not include a meltblown fiber layer as in conventional products of the prior art. Furthermore, it is not necessary to charge the filter medium with static electricity, which is also common in the art for sufficient filtration efficiency. Overall, it is advantageous that production can be simplified and an effective face mask consisting of only a relatively small number of parts can be provided.

[0020] Another advantage of the present invention is that it eliminates the need for additional layers such as support layers or cover layers. In the case of a multi-layered structure of the filter medium, the outer layer can also function as a cover layer, which greatly simplifies the production of masks.

[0021] Surprisingly, the filter medium of the present invention has been found to have a low pressure drop at high filtration efficiency, and therefore low breathing resistance. As a result, the comfort of the mask is significantly improved without significantly reducing performance. This is especially important in workplaces such as production sites, food or retail industries, during exercise, particularly during physical activity, or in gatherings of people. Therefore, the mask is ideal for non-medical personnel.

[0022] Typically, face shields include securing devices for attaching to the wearer's mouth and chin. For example, devices such as ribbons or clips ensure a tight fit between the mask and the sides of the face. Face shields can have various forms and structures and may include additional features such as face protection against splashes or droplets, anti-fog functionality, or a nose clip for adjusting the mask to the shape of the nose. The filter media may be secured in a frame or by other means.

[0023] The filter medium is a spun nonwoven fabric made of at least partially split multi-component filaments. The filter medium may consist of a single layer of spun nonwoven fabric or multiple layers of spun nonwoven fabric laid flat on each other.

[0024] The spun nonwoven fabric is a nonwoven fabric made of continuous fibers, which are spun from a polymer melt and stretched, placed on a nonwoven precursor (felt), and bonded together to form the nonwoven fabric. Continuous filaments are obtained in the spinning process, which are also referred to as unended filaments (as opposed to short fibers as defined). The fibers used in the filter media of the present invention are preferably continuous filaments rather than short fibers. As used herein, the terms fiber and filament are used synonymously. The spun nonwoven fabric is a nonwoven fabric or sheet. By definition, the fibers in a nonwoven fabric can be bonded by friction, adhesion, and / or cohesion. Typically, nonwoven fibers have a random orientation. Preferably, the nonwoven fabric is a textile as defined in ISO 9092:1988.

[0025] Woven nonwovens are preferred as the filter medium in face masks because woven nonwovens are relatively stable, do not exhibit significant particle loss, and have a relatively smooth surface. In particular, woven nonwovens made from finely split multi-component filaments are relatively soft and elastic, and therefore can provide greater skin comfort for the wearer.

[0026] The spun nonwoven fabric is composed of multicomponent filaments. The multicomponent filaments are splittable. The multicomponent filaments are at least partially split into basic filaments (monofilaments). The splittable multicomponent filaments consist of at least two different basic filaments aligned parallel to each other. The at least two different basic filaments have an alternating phase with each other and are adhered to each other in a splittable manner along the filament length. The adhesion is relatively loose. Preferably, the multicomponent filaments are mechanically split into basic filaments. Fluid jet treatment, typically water jet treatment, is particularly suitable because it simultaneously consolidates the spun nonwoven fabric. The spun nonwoven fabric after such treatment is characterized by a region in which the multicomponent filaments are only partially split or not split at all. The ratio of split filaments can increase with time and / or applied energy. When a sufficiently long and / or high-energy fluid jet treatment is performed, a spun nonwoven fabric consisting almost entirely of basic filaments can be obtained. Preferably, based on the total weight of the filaments, at least 60%, particularly at least 80%, at least 90%, or at least 95% of all filaments in the nonwoven fabric are basic filaments. The proportion of split filaments can be determined by microscopic analysis of multiple randomly selected regions of the nonwoven fabric.

[0027] In contrast, core / sheath type bicomponent filaments are typically non-split. They are usually used to bond bicomponent filaments together by passing them through a molten sheath component.

[0028] In a preferred embodiment, the basic filament has a fineness in the range of 0.01 dtex to 2.0 dtex, preferably between 0.02 dtex and 1 dtex. Particularly preferred is a fineness between 0.03 dtex and 0.6 dtex, and especially between 0.05 dtex and 0.4 dtex, or more preferably between 0.075 and 0.3 dtex. When the fineness is between 0.1 dtex and 0.2 dtex, particularly good filtration and breathability can be obtained. For example, a basic filament with such a low fineness can be obtained from bicomponent filaments of type PIE 16 by known methods. It has been found that such filter media can have particularly high filtration efficiency and breathability. Such monofilaments obtained from split multicomponent filaments are very fine and can also impart high elasticity and softness to the filter media, thereby increasing the comfort of the wearer.

[0029] Preferably, the multicomponent filament comprises two, three, or more different polymer components. A defined basic filament type is obtained from each component through splitting. Thus, the spun nonwoven fabric comprises at least two types of basic filaments that are different from each other. The basic filament types may comprise different types of polymers. The basic filament types may also comprise different finenesses. Preferably, the fineness difference between the components is at least 0.02 dtex. Higher filtration efficiency can be achieved by combining relatively fine and slightly thicker basic filaments in the spun nonwoven fabric. Preferably, the amount of each basic filament type in the multicomponent filament is the same. Preferably, the multicomponent filament comprises two or three different components. Particularly preferred are bicomponent filaments. In this respect, it is advantageous to achieve high splitting capacity, thereby resulting in a relatively simple material structure.

[0030] In a preferred embodiment, the filter medium consists of at least two layers of spun nonwoven fabric. Preferably, the filter medium consists of two to eight layers, particularly two to six layers. Preferably, the spun nonwoven fabric consists of two, three, four, or five layers. Particularly preferred is that the filter medium consists of two, three, or four layers. In one embodiment, two layers are present. In these embodiments, all layers are spun nonwoven fabrics made of at least partially split multi-component filaments. Surprisingly, filter media made of two layers has been found to have significantly better performance compared to comparable filter media of the same total basis weight comprising only a single layer. Filter media made of multiple layers not only have a much higher bacterial filtration efficiency (BFE) but also significantly higher air permeability.

[0031] In a preferred embodiment, the filter medium consists of three layers of spun nonwoven fabric. Preferably, the filter medium consists of three to eight layers, particularly three to six layers. Particularly preferred are three, four, or five layers of spun nonwoven fabric. Particularly preferred are three- or four-layer filter media. In these embodiments, all layers are spun nonwoven fabrics made of at least partially split multi-component filaments. Surprisingly, it has been found that filter media with three or more layers can even have better performance than comparable filter media of the same total basis weight consisting of only one or two layers. Generally, filter media made of three or more layers not only have a higher BFE but also significantly higher air permeability. This effect is particularly pronounced for three or four layers.

[0032] For practical reasons, it is preferable that the number of filter layers in the filter media is not too high. Therefore, it is preferable that the filter media have no more than four, five, or six layers. The reason is that this spun nonwoven fabric should not be too thin to provide good processability and efficient and consistent production. Therefore, an excessive number of layers with high thickness may result in a relatively high total basis weight. Generally, producing filter media from a large number of layers can be relatively cumbersome.

[0033] To provide stability to the face mask, the layers of the filter media can be attached to each other in known ways. Preferably, the layers are only loosely attached to each other, at least in some areas of the layers. This results in air gaps between the layers. Preferably, the layers are attached to each other only in certain areas of the layers. The attachment can be evenly distributed in the area, or it can be distributed only or mainly in the peripheral areas of the layers. Connections in the peripheral areas are preferred because air permeability is not reduced as a result. Alternatively, connections may exist outside the peripheral areas. The layers can be attached to each other using conventional techniques such as stitching or adhesive bonding, particularly by ultrasonic bonding. Labels for traceability or differentiation can be printed directly onto the filter media without further surface treatment.

[0034] Preferably, at least initially, the two, three, four, or more layers of the filter medium are produced separately from each other. The layers can then be bonded together. This ensures that the layers are discrete and provides air gaps between them when forming the laminated structure. Therefore, it is preferable that the layers are not laid out on top of each other in the same spinning process and / or by the same spinning station. However, when the spinning equipment has multiple spinning stations, different layers of the spun nonwoven fabric can be produced individually and discretely, and if desired, these different layers can be further processed in the same equipment and subsequently fully bonded.

[0035] In a preferred embodiment, the filter media may include multiple layers having a total basis weight (basic weight, area weight) of 40 g / m² to 300 g / m², preferably from 50 g / m² to 200 g / m², and particularly from 60 g / m² to 150 g / m². Preferably, the basis weight is at least 40 g / m² or at least 60 g / m² to achieve sufficient mechanical stability and BFE. Preferably, the basis weight is no greater than 200 g / m², or particularly, no greater than 150 g / m², to maintain sufficient breathability. In this respect, if the basic filaments are relatively fine, the basis weight can be adjusted to be relatively low. Surprisingly, this relatively low basis weight is sufficient for filter media that meet the requirements of medical face masks. This relatively lightweight material can provide high wearing comfort, especially when wearing the mask for extended periods and / or during physical exercise.

[0036] In a preferred embodiment, each layer of the spun nonwoven fabric has a basis weight of 10 g / m² to 100 g / m², preferably from 20 g / m² to 60 g / m², and more preferably from 20 g / m² to 40 g / m². The layers may include the same or different basis weights. Preferably, the filter medium comprises two, three, four, or five such layers. It has been found that particularly high BFE and air permeability can be obtained if the filter medium consists of layers having this basis weight.

[0037] In a preferred embodiment, each layer comprises a different basis weight. By selecting a defined basis weight, filtration performance can be improved. Thus, it is conceivable that the outer layer (two or more layers) or two outer layers (three or more layers) have a lower basis weight than the other one or more layers, in order to primarily achieve the protective function (as a cover layer). In another embodiment, the layers are identical, or the layers comprise at least the same basis weight and / or thickness. Identical layers may be advantageous because an effective filter medium can be easily obtained from a relatively small amount of the same components.

[0038] In a preferred embodiment, the filter medium comprises at least two layers, wherein the fiber diameter of the inner layer is smaller than that of at least one outer layer. This may be advantageous because one or more outer layers can impart relatively high stability to the filter medium, while one or more intermediate layers can have relatively high filtration efficiency. In the case of at least three layers, it is preferable that both outer layers have correspondingly larger fiber diameters.

[0039] Woven nonwovens can be obtained through a spinning process in which multicomponent filaments are laid up to form a nonwoven fabric, then the multicomponent filaments are split into basic filaments, and the nonwoven fabric is consolidated. In this process, a typical nonwoven structure is obtained. During the splitting into basic filaments, a tighter entanglement of the individual filaments is typically achieved compared to a corresponding nonwoven fabric made from monofilaments of the same fineness. The structural characteristic of split fiber nonwovens also lies in the following regions where, although the multicomponent filaments have been split, the basic filaments remain more or less parallel aligned. In general, nonwovens obtained from split multicomponent filaments have a defined and unique structure with advantageous properties.

[0040] Preferably, the multicomponent filament is produced by melt spinning. Thereby, the thermoplastic polymer is melted and spun from the melt. This provides a particularly simple and reliable method for producing spun nonwovens made from multicomponent filaments.

[0041] Typically, the basic filaments obtained by splitting multicomponent filaments have a non-circular cross-section, but rather an edged and irregular structure. This is advantageous because the irregularly shaped basic filaments have relatively low mobility relative to each other. In a particularly preferred embodiment, the multicomponent filaments, especially the bicomponent filaments, have a so-called pie-shaped structure (PIE structure, orange structure). Pie-shaped structures are advantageous because they can be split relatively easily. Bicomponent filaments with a pie-shaped cross-section are split into basic filaments with pie-shaped or wedge-shaped structures, which increases the internal stability of the nonwoven fabric.

[0042] Preferably, each multicomponent filament is formed from 8 to 64 basic filaments. Using known methods, bicomponent filaments with, for example, 8, 16, 24, 32, 48, or 64 segments can be obtained. Upon splitting, the multicomponent filament decomposes into a corresponding number of basic filaments (monofilaments). Thus, the term "pie-shaped" generally refers to the cross-section of the spinning nozzle, but only roughly describes the cross-sectional shape of the basic filaments. Preferably, the bicomponent filament has the same number of each type of basic filament (e.g., 8 basic filaments of each type in PIE16 bicomponent filament). The bicomponent filament preferably comprises alternating monofilaments. Also preferred is a hollow pie-shaped structure that includes a hollow space in the axial direction.

[0043] Particularly preferred is a spun nonwoven fabric made of bicomponent filaments in the form of 16 segments in a pie-cake shape. The spun nonwoven fabric particularly has a fiber fineness of 0.05 dtex to 4 dtex, wherein the total basis weight of the filter medium is preferably 75 g / m² to 200 g / m². It has been found that filter media made from this spun nonwoven fabric can have particularly high BFE and air permeability.

[0044] Preferably, the polymer forming the fiber is thermoplastic. Preferably, the polymer is selected from polyester, polyamide, polyolefin and / or polyurethane. Particularly preferred are bicomponent filaments having a polyester component and a polyamide component.

[0045] Preferably, the single-component filaments are split as much as possible. This improves the uniformity and fineness of the spun nonwoven fabric, thereby increasing filtration efficiency. To achieve high splitting capacity, it is advantageous that at least two basic filaments comprise different thermoplastic polymers, preferably incompatible. The combination of incompatible polymers results in little or no adhesive bonding between the paired filaments. Polyesters, polyamides, polyolefins, and / or polyurethanes are preferably used as incompatible polymer pairs. Polymer pairs containing polyamide and polyester, particularly polyethylene terephthalate (PET), are particularly preferred because of their low adhesion. Polymer pairs comprising at least one polyolefin are also preferred due to their low adhesion. A particularly preferred combination is a polyester, particularly PET, polylactic acid, and / or polybutylene terephthalate with polyamide (PA), particularly polyamide 6, polyamide 66, or polyamide 46, or, if desired, with one or more of the above components, preferably polyolefins. Particularly preferred are combinations of PET and polyamide 6, and PET and polyamide 66. Further preferred are polymer pairs comprising at least one polyolefin, particularly polymer pairs combined with at least one polyester or polyamide. Thus, polyamide 6 / polyethylene, PET / polyethylene, polypropylene / polyethylene, polyamide 6 / polypropylene, or PET / polypropylene are particularly preferred. These combinations have relatively high splitting capacity. In a preferred embodiment, the volume, length, and / or weight ratio of the first basic filament to the second basic filament is between 90:10 and 10:90, particularly between 80:20 and 20:80.

[0046] The polymer is the fiber raw material (fiber forming component) of the filament. The filament may include conventional additives. The additives are not fiber raw materials and are generally not organic polymers. Additives can be added to the fiber polymer to modify the properties of the fiber polymer or improve its processability. Suitable additives may include, for example, dyes, fillers, antistatic agents, antimicrobial agents such as copper, hydrophilic or hydrophobic modifiers, etc. For example, based on the total weight of the filament, the additives may be present in amounts up to 10 wt.%, preferably up to 5 wt.% or up to 2 wt.%, particularly in amounts between 150 ppm and 10 wt.%.

[0047] Methods for producing suitable multicomponent filaments that can be split into basic filaments are known in the art. For example, the production of such filaments and nonwovens is described in EP 3 165 655 B1, FR 2 749 860 A, and DE 10 2014 002 232 A1. For example, spun nonwovens can be produced using spinning equipment trademarked REICOFIL 4 (Reifenhäuser, DE). Hereinafter, suitable methods for producing filter media and spun nonwovens that can be used in this invention are described. Unless otherwise disclosed, a single layer of spun nonwoven fabric can be processed accordingly, or a filter media consisting of multiple layers of spun nonwoven fabric can be processed.

[0048] The filter media or spun nonwoven fabric can be subjected to mechanical processing in which multi-component filaments are at least partially split into basic filaments. Preferably, the filter media and / or spun nonwoven fabric are thus simultaneously consolidated. Fluid jet processing is preferred, in which a fluid, such as a liquid or gas, is applied to the nonwoven fabric under pressure. Water jet processing (hydroentangling, water jet needle punching) is particularly preferred. Water is inexpensive and readily available, and the nonwoven fabric can be dried rapidly without undesirable residues. The filaments are split and mixed, thereby forming a tight composite material through friction and fiber locking. Thus, a homogeneous spun nonwoven fabric with high softness and elasticity can be obtained. According to the invention, each layer of filter media can be individually consolidated by fluid jet processing, and then the layers can be combined; or the layers can be combined, and then each layer of filter media can be individually consolidated by fluid jet processing. Filter media and / or spun nonwovens can withstand common post-treatments, such as drying and / or shrinkage.

[0049] Additionally, further consolidation treatments, such as mechanical consolidation steps, can be performed. For example, consolidation can be performed by calendering. In one embodiment, pre-consolidation is performed by calendering, followed by water jet treatment. Calendering is preferably carried out at a sufficiently low temperature so that thermal consolidation due to molten fibers does not occur.

[0050] In another embodiment, the filter medium and / or the spun nonwoven fabric is thermally consolidated, particularly in certain regions. Localized consolidation in certain regions, which can be uniformly distributed across the nonwoven area, can improve stability. For example, low consolidation can be provided by ultrasonic treatment and / or calendering in a dot pattern. However, to maintain the advantageous properties of the nonwoven fabric, particularly for multilayer structures, only a small portion of the nonwoven fabric should be consolidated in this manner, typically less than 10% or even less than 5% of the total area. To avoid excessively reducing air permeability, the nonwoven fabric can be thermally consolidated in an oven without applying pressure.

[0051] However, it is preferred that the filter media and / or the spun nonwoven fabric is not thermally bonded, and in particular not thermally bonded over the entire area. This means that the nonwoven fabric is not subjected to temperature treatment over the entire area, in which the fibers or molten adhesive have softened, causing the fibers to adhere to each other. Non-thermally bonded nonwoven fabrics can be advantageous because porosity, softness, and elasticity can be maintained. In contrast, thermal bonding can alter mechanical properties in a way that is detrimental to the wearer's skin. In particular, the nonwoven fabric can become stiffer and less porous, thereby reducing air and moisture permeability.

[0052] However, the filter media may include areas that connect the layers to each other or to other parts of the mask and / or stabilize the mask, particularly the peripheral areas, or other areas; such as sealed seams, adhesive seams, or areas sewn together. This local fixation and connection of the peripheral areas does not affect the filtration performance. It should not be considered as a consolidation of the filter media or spun nonwoven fabric.

[0053] In a preferred embodiment, the filter media and / or the spun nonwoven fabric are not chemically bonded. This means that the fibers are not bonded to each other through a chemical reaction performed after spinning. Therefore, no covalent bonds are formed between the fibers. This has the advantage that the nonwoven fabric remains sufficiently soft and elastic, and there is no risk of the wearer inhaling residual products or byproducts from the chemical reaction. In a preferred embodiment, the filter media and / or the spun nonwoven fabric are not bound with an additional binder. This would be relatively complex and would introduce a risk of binder separation and inhalation by the wearer. Preferably, the filter media and / or the spun nonwoven fabric are not needled, and in particular, needle puncture is not performed. Such needle-punching or needle-piercing processes can be harmful because they may create areas of lower fiber density with higher porosity than desired, potentially reducing the BFE of the filter media. Simultaneously, relatively dense areas that reduce air permeability can be formed.

[0054] In a preferred embodiment, the filter media and / or the spun nonwoven fabric are consolidated solely by fluid jet treatment, particularly by water jet treatment. Therefore, no other consolidation treatments, such as thermal bonding, chemical bonding, or mechanical needle punching, are performed. It has been found that multi-component filaments can be effectively split and adequately consolidated solely by fluid jet treatment.

[0055] A particular advantage of the face mask of the present invention is that the face mask is washable and therefore reusable. Surprisingly, it has been found that the filtration efficiency does not decrease even after repeated washing. Furthermore, it has even been found that the performance of the face mask can be improved by washing, and surprisingly, the filtration efficiency can be improved in particular. Preferably, after 10 household washing cycles at 60°C according to DIN EN ISO 6339 or at 95°C in another embodiment, the BFE does not decrease and / or improves by at least 1%, more preferably by at least 2%, and most preferably by at least 5%.

[0056] Preferably, the face mask is washed at least once, more preferably at least twice, more preferably at least five times, or even at least ten times. In a preferred embodiment, the face mask is washed before it is first provided to and / or worn by the user. Preferably, the face mask is worn, for example, for at least one hour or one day between washing cycles. Preferably, the washing is carried out at elevated temperatures, such as at least 40°C, preferably at at least 60°C or at least 80°C. As used herein, the term "washing" refers to a conventional textile cleaning process, preferably carried out in a washing machine. This involves immersing the face mask in an aqueous washing solution, typically comprising detergent, and subjecting the face mask to mechanical agitation, typically for at least 10 minutes or at least 30 minutes. Preferably, the washing process is as described in DIN EN ISO 6330, which describes a standard washing process for textile fabrics.

[0057] Washing can improve the softness of the material and the comfort of the wearer. This improves the drape of the mask, allowing it to fit more closely and snugly to the shape of the face, thus providing better protection. However, without being bound by theory, it is assumed that the uniformity of the filter medium of the present invention can also be specifically improved by washing, and even by repeated washing. Multicomponent filaments are typically split at least partially into basic filaments by fluid jet processing, in which high mechanical forces act on the nonwoven fabric. This can result in an uneven microstructure due to splitting and / or density changes. For example, the mechanical forces during washing can smooth out such irregularities if areas with internal tension are relaxed. It is also conceivable that some residual multicomponent filaments, still loosely adhered to each other, will eventually split during washing.

[0058] In a preferred embodiment, the filter medium and / or the spun nonwoven fabric are static-free. Conversely, to achieve the desired BFE, the filter medium of prior art masks is typically static-charged. In the art, filter media are typically charged by corona treatment. Surprisingly, the filter medium of the present invention can have at least comparable or even higher filtration efficiency without static electricity. This is advantageous because static-charged filter media and corresponding masks used in the art are typically non-washable, as the static charge decreases and may even be completely lost during washing. Furthermore, static-free masks and filter media can be more easily manufactured with lower energy consumption and no discharge problems during storage or use.

[0059] The face mask of the present invention does not include meltblown fibers and / or meltblown fiber layers. This is advantageous because producing nonwovens and laminates from meltblown fibers is relatively complex. Furthermore, face masks in the art that include meltblown fibers are generally electrostatic. Therefore, the face mask of the present invention can be configured with a simpler filter medium and is not electrostatically charged, and will not deteriorate due to discharge during washing, storage, or use.

[0060] Preferably, the filter medium does not include other non-fibrous filter agents, such as adsorbents like activated carbon. It is advantageous to provide a filter medium consisting only of spun nonwoven fabric, as this filter medium is more convenient and economical, enabling the rapid production of large quantities of face masks.

[0061] Another advantage of the face mask of the present invention is that it can be sterilized in an autoclave, especially when it is made of polyester and polyamide filaments. Due to the composition of the materials, the filter media can be sterilized in a standard autoclave at a temperature above 120°C (sterilized at 134°C for at least three minutes according to DIN EN 285). In contrast, conventional filter media comprising a meltblown layer made of polypropylene cannot be sterilized under the conditions defined in DIN EN 285 because they require a significantly longer residence time in the autoclave.

[0062] In a preferred embodiment, the face shield and / or filter medium has a bacterial filtration efficiency (BFE) of at least 95%, at least 98%, or preferably at least 99% or 100% according to DIN EN 14683:2019. It has been found that the filter medium can have such a high BFE that the face shield can meet the requirements for Type I, Type II, or even Type IIR medical face shields. Therefore, the face shield of the present invention can also be very suitable for medical personnel. However, even face shields with lower performance may be practically relevant. For example, to prevent the spread of diseases such as COVID-19, it may be reasonable to provide face shields to the public that are inexpensive and readily available, and that offer high wearer comfort, but have a BFE below 95%. When faced with the problem of supplying large quantities of face shields, providing relatively simple masks rather than more complex but more effective masks may be more effective in achieving desired epidemiological goals. Empirically, when wearer comfort is high and breathing is only slightly impaired, wearer discipline, especially public discipline, is likely to increase. Therefore, in one embodiment, the mask may have a BFE of 80% to 95%, or in another embodiment, it may have a BFE of at least 85% or at least 90%.

[0063] In a preferred embodiment, the face shield and / or filter media have a breathability of at least 100 l / m²s, preferably greater than 133 l / m²s, and particularly preferably greater than 175 l / m²s, as determined according to EN ISO 9237:1995 at 100 Pa. Such breathability is relatively high for face shields with high BFE. Standard DIN EN 14683:2019 requires Type I and Type II face shields to have a pressure differential of <40 Pa / cm², which corresponds to a breathability of >133 l / m²s at 100 Pa according to DIN EN ISO 9237. Low pressure differential or high breathability means low breathing resistance, thus allowing the wearer to wear the mask for extended periods and perform strenuous tasks. Preferably, the mask has a pressure differential of <40 Pa / cm2, preferably less than 35 Pa / cm2, more preferably less than 30 Pa / cm2, or even less than 20 Pa / cm2 or <10 Pa / cm2, according to DIN EN 14683:2019.

[0064] In a preferred embodiment, the face mask and / or filter media meet the performance requirements for medical face masks of type I, II, or IIR according to DIN EN 14683:2019, particularly DIN EN 14683:2019, preferably meeting the performance requirements regarding bacterial filtration efficiency (BFE) and / or differential pressure, and even more preferably meeting the performance requirements regarding splash resistance and / or microbial purity. With respect to the standard DIN EN 14683:2019 referenced herein, it is preferably DIN EN 14683:2019:6.

[0065] Anti-splash properties can be adjusted by known methods, for example, by making the filter media hydrophobic. As is known in the art, microbial purity can be adjusted by preventing contamination during production, processing, and storage.

[0066] Preferably, the air permeability of the mask and / or filter media, determined according to EN ISO 9237:1995-12A using a test surface of 20 cm2 and a pressure difference of 200 Pa, is at least 20 mm / s, more preferably at least 30 mm / s, and is preferably the average of 100 or 50 individual values.

[0067] In a preferred embodiment, according to the manufacturer and / or ASTM E1294-89 and ASTM F-216-03, when the basis weight is 80 g / m2 or 100 g / m2, the spun nonwoven fabric has an average pore size of 10 μm to 50 μm and / or a maximum pore size of 30 μm to 120 μm as determined by using the pore size measuring device PSM 165 from TOPAS, DE.

[0068] In a preferred embodiment, the filter medium has a thickness of 0.1 mm to 1 mm, particularly between 0.2 mm and 0.6 mm, as defined in DIN ISO 9073-2:1995, Part 2, for ordinary nonwoven fabrics. Preferably, the filter medium and / or the spun nonwoven fabric have a maximum tensile strength (maximum tensile force) of at least 200 N / 5 cm, particularly at least 250 N / 5 cm, as defined in EN 13934-1, in all directions. Preferably, the maximum elongation in all directions is 20% to 60%, as defined in DIN EN 13934-1.

[0069] In an embodiment, the mask includes at least one additional layer that is not a filter medium. The additional layer is attached to the filter medium over the entire flat area and is traversed by breathing air in the same manner as the filter medium. The connection between the layers is generally loose, resulting in air gaps between the layers. The additional layer may be, for example, a support layer or a cover layer. The support layer improves the mechanical stability of the filter medium attached to the support layer. The cover layer protects the filter medium from environmental influences, such as mechanical damage or moisture. The additional layer is not a filter medium because it cannot effectively remove infectious agents from breathing air. Preferably, the additional layer is composed of fibers and / or preferably a textile layer, more preferably a nonwoven or woven fabric. The fiber diameter of such an additional layer may, for example, be greater than 0.1 mm or greater than 0.25 mm. Typically, the support layer has fibers that are significantly stronger (thicker) than the filter medium and does not significantly or not at all increase the pressure differential of the filter medium. For example, the at least one additional layer may reduce the air permeability of the filter medium by less than 10%, particularly less than 5% or even less than 2%. Most importantly, the supplementary layer is not a filter medium for removing droplets and / or infectious agents. The supplementary layer may have a BFE of <5%, specifically <2% or even about 0%. This supplementary layer can be attached to the filter medium by conventional methods such as sewing or bonding, particularly by ultrasonic bonding, especially in the peripheral region of the layer.

[0070] In a preferred embodiment, the mask does not include any additional layers besides the filter media itself. This is advantageous because a simple mask can be provided with only a few components. It has been found that such a simple mask not only has high filtration efficiency but also high mechanical stability. In cases where the filter media has three or more layers, the outer layer can function as both a support layer and a cover layer. The outer layer may include fewer filaments, which imparts greater mechanical stability to the filter media. Such masks, where the filter media is not bonded to other layers, can be mass-produced simply, quickly, and cost-effectively, which is crucial in the event of an epidemic or pandemic.

[0071] In a preferred embodiment, the mask has the following properties:

[0072] - The filter medium comprises at least two layers of spun nonwoven fabric, preferably at least three layers of spun nonwoven fabric.

[0073] - The filter media has a basis weight of 60 g / m2 to 200 g / m2.

[0074] - The mask does not include additional layers, and

[0075] - The face mask has a bacterial filtration efficiency (BFE) of at least 95%, preferably at least 98%, as determined according to DTN EN 14683:2019.

[0076] Preferably, the face shield is a medical product, particularly a mouth / nose protection device (MNP), also known as a surgical mask, clinical mask, or OP face shield. This refers to a half-face shield with a filter medium attached to a fastening device, such as an elastic band or elastic strip, to the back of the head or behind the ears. If desired, an integrated flexible metal frame can align the upper part of the half-face shield to the bridge of the nose to maintain freedom of vision and prevent upward exhalation. After a single use, the MNP can be discarded. However, it is preferred that the MNP be washable and reusable. MNPs can also be used to prevent the spread of infectious agents through the public. In preferred embodiments, the face shield is a medical face shield, mouth / nose protection device, folding mask, mask basket, filtering half-face shield, or equivalent mouth / nose protection device.

[0077] The subject matter of the present invention also relates to the use of spun nonwoven fabrics made of at least partially split multi-component filaments as a filter medium in face shields, particularly surgical masks, for the prevention of infectious agents. The spun nonwoven fabric, which can be composed of multiple layers as described above, is the sole filter medium in the face shield.

Implementation Method

[0078] The subject matter of this invention also relates to the use of face shields for filtering air and / or removing airborne pathogens during wear. Users may be medical personnel, individuals in close contact with others such as caregivers, or non-medical professionals from the general public.

[0079] The subject matter of this invention also relates to the use or provision of face shields for filtering air and / or removing infectious agents during wear by non-medical professionals from the general public, wherein, for example, BFE can be in the range of >80% to <95%. This use is particularly suitable for preventing the spread of infectious agents in the public in a simple and cost-effective manner, especially in the event of an epidemic or pandemic.

[0080] The face mask and its uses of the present invention solve the fundamental problems of the present invention. The face mask has a simple structure and can therefore be mass-produced easily, quickly and conveniently. The face mask can have a high filtration efficiency (BFE) while providing high comfort to the wearer. Therefore, breathability can be high, resulting in low breathing resistance. The face mask is reusable and washable, and its advantageous performance can even be significantly improved during washing.

[0081] An alternative embodiment is a face mask for preventing infection of pathogens, having a first filter medium made of a spun nonwoven fabric composed of multi-component filaments, which are at least partially split into basic filaments, wherein optionally there is at least one additional layer that is not a filter medium, and optionally there is at least one additional layer that is another filter medium different from the first filter medium. Such an additional filter medium may be practically unnecessary to achieve excellent filtration performance. However, it is conceivable that in some embodiments, filtration efficiency can be further optimized by combining it with another filter medium. Thus, the filter medium made of multi-component filaments can be combined with a second filter medium such as a meltblown fiber layer, particularly a meltblown fiber layer made of polypropylene, or a spun nonwoven fabric made of single-component filaments, particularly polypropylene, which can be charged.

[0082] Work Example

[0083] Materials

[0084] The filter media in Examples 1 to 8 are spun nonwoven fabrics trademarked as Evolon (Freudenberg, DE), consisting of at least partially split bicomponent filaments having 16 pie-shaped segments (PIE16). The bicomponent filaments consist of 16 alternating basic filaments comprising polyester (PET) and polyamide 6. The fineness of the monofilaments is between 0.1 dtex and 0.2 dtex. The spun nonwoven fabric is produced similarly to that described in Example 1 of EP 3 165 655 B1. The bicomponent filaments are split and the nonwoven fabric is consolidated by water jet treatment. The spun nonwoven fabric is not consolidated by needle punching. These properties are summarized in Table 2 below. The PET to polyamide ratio and basis weight are selected as shown in the examples.

[0085] Examples 1 to 4

[0086] In Examples 1 to 4, the filtration efficiency was checked using a test method required for testing medical masks containing aerosol particles (solid particles, 3 μm in diameter). The mask or material was formed into a disc with a diameter of 48 mm. The sample was placed in a tube containing aerosol. The aerosol concentration was measured in the tube and in the flow through the sample from the inside out. The result is the percentage of particles blocked by the material. The air permeability of the filter media was determined according to DIN EN ISO 9237 at 100 Pa.

[0087] Examples 1 to 3: Filtration performance and air permeability of filter media

[0088] In the first series of tests, the filtration performance of filter media consisting of one, two, or three layers with a comparable total basis weight was examined. The results are summarized in Table 2. The results demonstrate that the filter media is well-suited for removing aerosol particles from breathing air. The results indicate that the filter media meets the requirements for medical masks according to DIN EN 14683:2019. Furthermore, it has been surprisingly demonstrated that performance is significantly improved when using multi-layer structures with the same total basis weight. For multi-layer structures, while breathability is also significantly improved, higher filtration efficiency is achieved. Three-layer filter media can even achieve 100% filtration efficiency with a high breathability of 195 l / m²s at 100 Pa. This indicates performance in accordance with Standard Class II, where breathability is significantly higher than the required minimum level of 133 l / m²s. Breathing resistance is low, and the user experiences high wearer comfort and high protection. For filter media comprising two layers, the filtration efficiency is also very high at 98%, however, the breathability is slightly lower than the standard level. However, it can be safely assumed that a corresponding two-layer filter media with a reduced thickness will meet the standard requirements. A comparable filter media made of a single layer with a basis weight of 100 g / m² achieves a filtration efficiency of 97%, but its air permeability is 60 l / m²s. Therefore, the breathing resistance is below the minimum level required by the standard.

[0089]

[0090] Example 4: Washability of face masks

[0091] The washability of a foldable face mask comprising a partially split bicomponent filament filter medium was examined. To examine potential variations in filtration efficiency in both directions, a filter medium consisting of two layers, each with a basis weight of 40 g / m², was used, exhibiting relatively low filtration efficiency. The performance of this filter medium is summarized in Table 3 below.

[0092]

[0093] The filtration efficiency of the three face masks was determined before and after washing. The face masks underwent ten washing cycles at 90°C. The results are summarized in Table 4. The results demonstrate that the filtration efficiency not only did not decrease but was significantly improved. This is highly advantageous because the filter media is reusable, and washing even imparts higher performance to the filter media; in contrast to products in the art that must be discarded after use.

[0094]

[0095] Examples 5 to 8

[0096] In Examples 5 to 8, the performance of the filter media and face mask was determined using a liquid aerosol containing Staphylococcus aureus according to DIN EN 14683:2019. Generally, achieving high bacterial filtration efficiency using a liquid aerosol containing bacteria is more challenging than using solid particles of a corresponding size.

[0097] Example 5

[0098] A three-layer filter media (trademarked Evolon Evo30PK, Freudenberg, DE) consisting of three layers with a basis weight of 30 g / m² was examined. According to DIN EN 14683:2019, the bacterial filtration efficiency (BFE) of the three test specimens was 92.8%, 91.2%, and 91.6% when the average particle size of the bacterial aerosol was 3.1 μm. The average differential pressure of the five test specimens was determined according to Annex C of DIN EN 14683:2019 and found to be 23.3 Pa / cm², 25.4 Pa / cm², 22.8 Pa / cm², 28.2 Pa / cm², and 21.9 Pa / cm². Overall, the differential pressure meets the standard, while the BFE is slightly below the minimum level of 95% for Type I face masks.

[0099] Example 6

[0100] The filter media as in Example 5 was washed at 60°C, and then the BFE and pressure differential were determined. The BFE was 99.86% (average of 5 test samples), and the pressure differential was 38.5 Pa / cm² (±3.0 Pa / cm², average of 5 test samples), both determined according to DIN EN 14683:2019. Therefore, the filter media of Example 5 after washing meets the requirements of Type I and Type II standards. This demonstrates that washing can significantly improve the performance of the filter media of the present invention.

[0101] Example 7

[0102] A filter media consisting of three layers, each with a basis weight of 30 g / m² (trademark: Evolon Evo30PK, Freudenberg, DE) underwent a single washing step. The average BEF according to Annex B of DIN EN 14683:2019 was 97.84%. The average differential pressure according to Annex C of DIN EN 14683:2019 was 31.2 Pa / cm². The difference from Example 6 is likely due to the lower initial degree of splitting of the bicomponent fibers. The results indicate that BEF and differential pressure can be adjusted by conventional measures such as changing the basis weight and degree of splitting, and thus regulating respiratory comfort.

[0103] Example 8

Claims

1. A face mask for preventing the transmission of infectious agents and having a filter medium made of a spun nonwoven fabric, said spun nonwoven fabric being composed of multi-component filaments, said multi-component filaments being at least partially split into basic filaments, wherein, The mask optionally includes at least one additional layer that is not a filter medium, wherein the basic filament has a fineness from 0.05 dtex to 0.4 dtex.

2. The face mask according to claim 1, wherein, The filter medium comprises at least two layers, preferably at least three layers, of spun nonwoven fabric.

3. The face mask according to claim 1 or 2, wherein, Each layer of the spun nonwoven fabric has a basis weight of 10 g / m2 to 100 g / m2, preferably from 20 g / m2 to 60 g / m2.

4. The face mask according to claim 1 or 2, wherein, The filter medium has a total basis weight of 40 g / m2 to 300 g / m2, preferably from 60 g / m2 to 200 g / m2.

5. The face mask according to claim 1 or 2, wherein, The multi-component filaments are split by fluid jet treatment.

6. The face mask according to claim 1 or 2, wherein, The multicomponent filament is a bicomponent filament with a pie-shaped structure (PIE-structure).

7. The face mask according to claim 1 or 2, wherein the face mask has been washed at least once, preferably at a temperature of at least 40°C.

8. The face mask according to claim 1 or 2, wherein, The filter medium is non-static.

9. The face mask according to claim 1 or 2, wherein the face mask has a bacterial filtration efficiency (BFE) of at least 95%, preferably at least 98%, as determined according to DIN EN 14683:2019.

10. The face mask according to claim 1 or 2, wherein the face mask has a differential pressure of less than 40 Pa / cm2, preferably less than 30 Pa / cm2, as determined according to DIN EN 14683:2019, and / or the face mask has a breathability of at least 100 l / m2s at 100 Pa, as determined according to EN ISO 9237:1995.

11. The face mask according to claim 1 or 2, having the following characteristics: - the filter medium comprises at least two layers of spun nonwoven fabric, - the filter medium has a basis weight of 60 g / m2 to 200 g / m2, - the face mask does not include additional layers, and - the face mask has a bacterial filtration efficiency (BFE) of at least 98% as determined according to DIN EN 14683:2019.

12. The face shield according to claim 1 or 2, wherein the face shield is a medical face shield, a mouth and nose protection device, a folding mask, a mask basket, a filtering half-face shield, or an equivalent mouth and nose protection device.

13. The face shield according to claim 1 or 2, wherein the face shield is intended for use in filtering air and / or removing infectious agents from the air during wear.