IT202100010604A1 - COMPOSITE FILTER MATERIAL FOR THE CONSTRUCTION OF FABRICS AND THE MANUFACTURING PROCESS OF THE SAME - Google Patents

Description

COMPOSITE FILTER MATERIAL FOR THE CONSTRUCTION OF

FABRICS AND MANUFACTURING PROCESS OF THE SAME

TECHNICAL FIELD

The present invention generally relates to a filtering composite material, preferably an active filtering composite material, for making fabrics and to a manufacturing process of this material. In particular, the present invention relates to a composite material comprising at least one layer added with nanomaterials.

STATE OF ART

State of the art ? it is known to produce filters capable of retaining pathogenic agents - such as viruses, bacteria and spores - dusts or allergens, by applying a layer of nanofibres on a transpiring substrate, thus realizing a composite filtering material. The nanofibers that define the layer are arranged in such a way as to define, between them, interspaces of nanometric dimensions, therefore small enough to retain the particles to be filtered. The filtration efficiency of these materials ? extremely high and the filtration principle ? mechanical. The particles in the air are more? pores in the nanofiber network, but gases and vapors can pass through them with limited pressure losses. In this way, the substrate maintains its properties? breathable.

The nanofibers used consist of filaments of flexible material, typically polymeric, which can be of natural or synthetic origin. Examples of natural polymers include collagen, cellulose, silk fibroin, keratin, gelatin, and polysaccharides such as chitosan and alginate. Examples of synthetic polymers include poly(lactic acid) (PLA), polycaprolactone (PCL), polyurethane (PU), poly(lactic-co-glycolic) acid (PLGA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) ( PHBV) and poly(ethylene-co-vinyl acetate) (PEVA).

Many methods for producing nanofibers are known in the state of the art, among which the most? commonly used ? electrospinning. Among other things, electrospinning makes it possible to generate ultra-thin fibers with controllable diameters, compositions and orientations.

Nanofibers are also extremely flexible with respect to their functionalization. AND? therefore it is known to functionalize the layer of nanofibers with chemical additives, also of nanometric dimensions, such as ceramic or metal nanoparticles? for example copper or silver, to give the composite material properties? germicidal. These particles are in fact capable of oxidatively degrading cell membranes, inactivating them.

Of particular interest? l?application in which, as a chemical additive,? used an oxidative catalyst able to keep its germicidal action unchanged over time. The oxidative catalyst, if suitably activated, on the one hand promotes the oxidation of the pathogen and on the other ? able to regenerate. Among the oxidative catalysts, the use of catalysts that can be activated through the irradiation of light (photocatalysts) is remarkably widespread, including in particular titanium dioxide (TiO2), which is activated by ultraviolet radiation. Of particular interest is also the fact that the photocatalytic action of titanium dioxide nanoparticles allows the decomposition of volatile organic compounds (VOCs), which are mainly responsible for bad odors in closed environments.

The Applicant has observed that the nanofibre filtering layer of the composite material is particularly delicate. This filtering layer generally adheres to the substrate in a precarious manner, being able to detach from the substrate or release the nanofibers in the event of abrasion. This not only leads to the degradation of the filter layer, but generates more? nanopowders which can be particularly harmful if inhaled.

With particular reference to titanium dioxide nanoparticles, the Applicant has also observed that these nanoparticles are fixed to the layers of nanofibres, coating them with a dispersion of resins and nanoparticles. However, this coating offers poor resistance to washing and abrasion, operations which generally cause a removal of the resin from the nanofiber layer, and with it, of the photocatalytic nanoparticles so constrained.

State of the art ? it is known to use such a filtering composite material in combination with breathable fabric layers, for example in oro-nasal protection devices. In particular, oral-nasal protection devices made up of two layers of fabric generally have a pocket through which It is possible to insert the composite material to arrange it between the two layers of fabric. In these devices, the layers of fabric must necessarily be thin enough to allow the passage of air, to guarantee breathability, and possibly of light for the activation of a possible photocatalyst.

In these devices, the pathogen, generally passing through a first layer of transpiring fabric, is blocked by the nanofibres present on the composite material for a time sufficient for inactivation due to the effect of the oxidative action, possibly supported by a photocatalytic effect.

The Applicant has found that due to the delicacy of the nanofibre layer of the filtering composite material described above, already the operations of inserting this composite material between the two layers of fabric generally involve a partial degradation of the filtering effect and/or of the germicidal effect which adds to the deterioration generated by normal use.

The Applicant has in fact pointed out that the device resulting from the whole of the filtering composite material inserted between the two layers of fabric cannot? be subjected to the traditional maintenance operations of a traditional fabric, without suffering deterioration. In fact, the rubbing of the composite material against the two layers of fabric due, for example, to washing or ironing operations leads to a natural detachment of the nanomaterials present in the filtering layer of the composite material, thus making it no longer? effective n? with reference to its filtering action, n? with reference to its possible further germicidal action.

To overcome these problems? been considered to load the composite material with many pi? nanomaterials than those actually needed to have a good filtering and/or germicidal action. In fact, the loss of part of the nanomaterials (nanofibers and nanoparticles) following handling of the device would be compensated by a higher quantity foreseen at the outset.

This solution, however, involves higher costs than those actually necessary. Furthermore, while providing for large quantities of nanomaterials, it is not It is possible to exclude that the degradation will sooner or later lead to definitively compromising the filtering and/or germicidal effects of the material.

Last but not least, a greater quantity? of nanomaterials in the filtering layer of the composite material introduces a greater pressure drop as the air passes through, making, for example, the use of this composite material inside an oral-nasal protection device not very comfortable.

OBJECTS AND SUMMARY OF THE INVENTION

In the light of the above, the problem underlying the present invention? that of devising a filtering composite material which is strong enough not to be substantially subject to degradation in the normal operations of processing, use and maintenance of the same.

Within the scope of this problem, an object of the present invention is that of creating a filtering composite material capable of maintaining its filtering effect substantially unchanged over time regardless of the type of use made of it.

Another purpose of the present invention ? that of producing a filtering composite material that requires a minimum quantity of nanomaterials to exert its filtering and germicidal effects over time.

Another purpose of the present invention? that of obtaining a filtering composite material which substantially does not release nanodust during its use.

In accordance with a first aspect thereof, the invention therefore relates to a composite filtering material comprising at least one intermediate layer of nanomaterials coupled between layers of breathable material and interposed between them, the intermediate layer and the layers of breathable material being mutually bonded through a plurality of micrometric constraints made along an overlapping surface of the layers, where the micrometric constraints have dimensions that can be measured in terms of the diameter of a circumference that inscribes each constraint, with the diameter d of this circumference being less than or equal to 1.0 mm.

Has the Applicant identified that thanks to the creation of micrometric constraints, such as for example microwelding or microgluing dots, with suitable micrometric dimensions, ? it is in fact possible to constrain the layers to each other, maintaining the filtration characteristics of the composite material unaltered and at the same time canceling the mechanical stresses on the intermediate layer, which are discharged from the constraint points.

Furthermore, the presence of the micrometric constraints makes it possible to prevent detachment from the breathable layers, detachment which would lead to a loss of the filtering effect, without however being identifiable by visual inspection of the composite material, since it is concealed by the breathable material itself.

Basically, the presence of micrometric constraints makes it possible to remedy the degradation of the intermediate layer in nanomaterials.

In accordance with a second aspect thereof, the invention relates to a process for manufacturing a composite filter material comprising the steps consisting of:

- create a layer in nanomaterials;

- binding the layer of nanomaterials between two layers of breathable material and interposed between them by creating micrometric constraints distributed along an overlapping surface of the layers, where the micrometric constraints have dimensions that can be measured in terms of the diameter of a circumference that inscribes each constraint, with the diameter d of this circumference less than or equal to 1.0 mm.

Advantageously, the manufacturing process of a filtering composite material so? configured it allows to achieve the same advantages described with reference to the filtering composite material according to the invention.

The present invention can have at least one of the preferred characteristics listed below, the latter in particular being combinable with one another as desired in order to satisfy specific application requirements.

Preferably, the micrometric constraints have the diameter d less than or equal to 0.5 mm, more? preferably less than or equal to 0.2 mm.

Preferably, the micrometric constraints are distributed over at least a portion of the overlapping surface of the layers with a surface distribution of at least 1 constraint/cm<2>, preferably at least 5 constraints/cm<2>, more? preferably at least 25 constraints/cm<2>.

In an alternative embodiment, particularly suitable for areas of the overlapping surface intended to be subjected to more mechanical stresses, intense, the micrometric constraints are distributed on at least a portion of the overlapping surface of the layers with a surface distribution of at least 45 constraints/cm<2>, preferably at least 70 constraints/cm<2>, more? preferably at least 160 constraints/cm<2>.

In a preferred embodiment, the micrometric constraints are made in such a way as to define at least two areas included in the overlapping surface having different surface distribution of the micrometric constraints.

In a variant of the invention, the micrometric constraints have a substantially grid distribution with an interspacing pitch p comprised between 0.4 mm and 10 mm.

Pi? preferably, the interspacing step p ? between 0.6 mm and 5 mm.

even more preferably, the interspacing step p ? between 0.8 mm and 2 mm.

In a variant of the invention, the nanomaterial layer has a thickness, measured in density, of of nanomaterials, between 1 g/m2 and 10 g/m2.

Preferably, the nanomaterial layer has a thickness, measured in density, of nanomaterials, between 1.2 g/m2 and 5 g/m2.

Pi? preferably, the nanomaterial layer has a thickness, measured in density? of nanomaterials, between 1.5 g/m2 and 3 g/m2.

In a variant of the invention, the nanomaterials which make up the intermediate layer comprise nanofibres in flexible material, typically polymeric of natural or synthetic origin.

Preferably, the nanomaterials which make up the intermediate layer comprise chemical additives with a germicidal effect in the form of nanoparticles.

Pi? preferably, the nanoparticles of chemical additives with a germicidal effect include nanoparticles of:

- Copper (Cu),

- Silver (Ag)

- Nitrogen-doped titanium dioxide (N-TiO2),

- Zinc Oxide (ZnO), e

- Silica (SiO2).

In a preferred variant of the invention, the nanomaterials which make up the intermediate layer comprise nanoparticles of chemical additives which can be activated by electromagnetic radiation with wavelength ? included in the ultraviolet spectrum or in the visible spectrum.

Preferably, the nanoparticles of chemical additives which can be activated through electromagnetic radiation with a wavelength ? included in the ultraviolet spectrum or in the visible spectrum include nanoparticles of: - nitrogen-doped titanium dioxide (N-TiO2),

- zinc oxide (ZnO), e

- silica (SiO2).

Preferably, the nanomaterial layer has a capacity filtering grade at least equal to the FFP1 grade defined in the UNI EN 149:2009 standard or equivalent.

Pi? preferably, the layer in nanomaterials has a capacity? filtering grade at least equal to the FFP2 grade defined in the UNI EN 149:2009 standard or equivalent.

Preferably, at least one of the two layers in breathable material? made in the form of fabric, non-woven fabric or cloth.

Preferably, at least one of the two layers in breathable material? made of fabric, non-woven fabric or cloth which is light enough to permit the passage of light therethrough, in particular the passage of sunlight.

Preferably, at least one of the two layers in breathable material? made of muslin, jersey or other textile material used in the manufacture of clothing, furnishings and linen.

Preferably, the micrometric constraints are microweldings and the layers of transpiring material are made of thermoplastic materials.

Alternatively, the micrometer constraints are micrometer dots of glue.

In a variant of the invention, the step of realizing a layer in nanomaterials comprises functionalizing the microfibers by means of a chemical germicidal agent, preferably a photocatalytic germicidal chemical agent, more preferably a photocatalytic germicidal chemical agent that can be activated by electromagnetic radiation with a wavelength ? included in the visible spectrum.

In a variant of the invention, the manufacturing process comprises a transformation step of the filtering composite material comprising the creation of cuts, stitching and finishing.

Advantageously, starting from the filtering composite material according to the invention, it is possible to make textile products such as tablecloths, curtains, coverings, clothing or even oro-nasal protection devices capable substantially of sanitizing themselves autonomously within a few seconds of exposure to the light. Furthermore, thanks to the property of decomposition of volatile organic compounds (VOC) of nanoparticles activatable through electromagnetic radiation with wavelength ? in the ultraviolet spectrum or in the visible spectrum? It is possible to create textile products which are able in fact not to absorb the bad smells present in the environments in which they are stationed and to contribute to their elimination from the environment itself.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become clearer from the following detailed description of some of its preferred embodiments, made with reference to the attached drawings.

The different features in the individual configurations can be combined with each other as desired according to the previous description, if one has to make use of the advantages specifically resulting from a particular combination.

In such designs,

- figure 1 ? an enlarged, broken away perspective view of a portion of a composite filter material according to a first embodiment of the present invention;

- figure 2 ? a detailed diagram illustrating the micro-constraints applied to the filtering composite material in accordance with a second embodiment of the present invention;

Figures 3a and 3b are enlarged schematic representations of a filtering composite material according to a third and a fourth embodiment of the present invention, respectively;

- figure 4 ? a block diagram of the manufacturing process of a composite filter material according to the present invention; And

- figure 5 ? an enlarged schematic view of a nanofiber functionalized with chemical additives in the form of nanoparticles.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, for the illustration of the figures, identical reference numbers or symbols are used to indicate construction elements with the same function. Furthermore, for clarity of illustration, some references may not be repeated in all the figures.

While the invention? susceptible to various modifications and alternative constructions, some preferred embodiments are shown in the drawings and will be described in detail below. It must be understood, however, that there is no no intention of limiting the invention to the specific embodiment illustrated, but, on the contrary, the invention intends to cover all modifications, alternative constructions and equivalents which fall within the scope of the invention as defined in the claims.

The use of ?a example?, ?etc?, ?or? indicates non-exclusive alternatives without limitation unless otherwise indicated. The use of ?includes? and ?include? means ?includes or includes, but not limited to? unless otherwise indicated.

Referring to Fig. 1 , ? illustrated a preferred embodiment of a filtering composite material according to the present invention, indicated as a whole with 10.

The filtering composite material 10 comprises at least one intermediate layer 11 of nanofibres sandwiched between two contiguous layers of transpiring material 12,13. As nanofibres, nanofibers in flexible material, typically polymeric, which can be used are preferably used. be of natural or synthetic origin.

The breathable material layers 12,13 are made of any type of fiber and in the form of fabric, non-woven fabric or cloth. Suitable fibers for making the layers in transpiring material 12,13 are, for example, natural fibres, such as cotton, silk, wool and so on. away, artificial fibers, such as viscose, lyocell, modal and so on? via or synthetic fibers, such as polyester (PS), polyethylene (PE), polypropylene (PP) and so on? Street.

At least one of the two layers in breathable material 12.13 ? also made of fabric or cloth light enough to permit the passage of light therethrough, in particular the passage of sunlight. An example of fabric suitable for allowing the passage of light? the muslin; an example of fabric suitable to allow the passage of light? the jersey. An example of non-woven fabric suitable for allowing the passage of light? a sufficiently thin microfiber cloth.

As better illustrated in Fig. 2, the at least one intermediate layer 11 made of nanofibers is bound to the two layers of transpiring material 12,13 by means of micrometric bonds made along an overlapping surface of the layers 11,12,13. Each constraint has dimensions that can be measured in terms of the diameter of a circle that inscribes the constraint, having a diameter d smaller than or at most? equal to 1.0 mm, preferably less or more? equal to 0.5 mm, pi? preferably lower or at the pi? equal to 0.2 mm.

The micrometric constraints are furthermore distributed on the surface of the sandwich 11,12,13 with a surface distribution of at least 1 constraint/cm<2>, preferably at least 5 constraints/cm<2>, more? preferably 25 constraints/cm<2>.

In particular, the micrometric constraints are distributed on the surface of the sandwich 11,12,13 with surface distributions chosen according to the mechanical stresses to which a particular area of the surface can be subjected.

For example, in the case of a composite material 10 intended for use as an oro-nasal protection device, such as the one illustrated in Fig. 3a, ? identifiable a? central area A1 in which ? a higher surface distribution is expected, for example equal to 280 constraints/cm<2>, compared to a surface distribution of a perimeter area A2, for example equal to 10 constraints/cm<2>. In the embodiment of Fig. 3a , the microconstraints are made according to a random distribution.

In the case instead of a composite material 10 intended for use as for example a tablecloth, such as the one illustrated in Fig. 3b, ? identifiable a? central area A1 in which ? a lower surface distribution is expected, for example equal to 5 constraints/cm<2>, compared to a surface distribution of a perimeter area A2, for example equal to 160 constraints/cm<2>. In the embodiment of Fig. 3b, the microconstraints are made according to a regular grid distribution.

In the case of a regular grid distribution, the micrometric constraints are preferably spaced apart by an interspacing pitch p comprised between 0.4 mm and 10 mm, preferably between 0.6 mm and 5 mm, more? preferably between 0.8 mm and 2 mm.

Preferably, the micrometric constraints are microweldings in case the layers of transpiring material 12,13 are made of thermoplastic materials, or, alternatively, micrometric dots of glue.

The middle layer 11 ? configured so as not to be an obstacle to heat-sealing or gluing and therefore sufficiently thin to allow the interpenetration of the layers of transpiring material 12,13 at the melting points or the passage of the adhesive.

At the same time, the intermediate layer 11 comprises a thickness and a degree of uniformity sufficient to guarantee a capacity? filtering at least grade FFP1 with the capacity? filtering measured according to the UNI EN 149:2009 standard or equivalent.

The Applicant has identified that to allow the micro-constraints described above to be achieved, the thickness - measured in density? of nanofibres - must be less than or at most equal to 10 g/m2. On the other hand, in order to guarantee a capacity? filter grade FFP1 measured according to the UNI EN 149:2009 standard ? which implies a high degree of uniformity? of the intermediate layer 11 substantially free of aggregates (clusters) or bundles of fibers - the thickness of the intermediate layer 11 must be equal to at least 1 g/m². Preferably, the thickness of the intermediate layer is between 1.2 g/m2 and 5 g/m2, more? preferably the thickness of the intermediate layer ? between 1.5 g/m2 and 3 g/m2.

According to a preferred embodiment, the intermediate layer comprises, in addition to the microfibres, at least one germicidal chemical additive in the form of nanoparticles. Specifically in the illustrated embodiment, the germicidal material ? a photocatalytic chemical additive. Alternatively, non-photocatalytic chemical additives such as Copper (Cu) or Silver (Ag) can be used.

Among the photocatalytic chemical additives, the chemical additives that can be activated by electromagnetic radiation with wavelength ? comprised in the visible spectrum (that is, substantially 400 nm ? ? 740 nm) or in the ultraviolet spectrum (that is, substantially 100 nm ? ? 400 nm). By way of example, known catalysts that can be activated by electromagnetic radiation with a wavelength ? Included in the visible or ultraviolet spectrum are nitrogen-doped titanium dioxide (N-TiO2), zinc oxide (ZnO), and silica (SiO2).

Advantageously, the chemical additives that can be activated through electromagnetic radiation with wavelength ? included in the visible spectrum or in the ultraviolet spectrum, they are very energetic catalysts that require less energy from the outside, as they can also be activated only by the radiation generated by the sun or even by indoor lamps.

The manufacturing process of a filtering composite material 10 according to the present invention ? schematically illustrated in Fig.4.

Is obtained (step 110) a layer of nanofibers 11 having thickness - measured in density? of nanofibres - between 1 g/m2 and 10 g/m2, preferably between 1.2 g/m2 and 5 g/m2, plus? preferably between 1.5 g/m2 and 3 g/m2.

The nanofiber layer 11 ? preferably functionalized (step 115) by means of a germicidal chemical agent, in particular a photocatalytic germicidal chemical agent in the form of nanoparticles dispersed in the matrix of the nanofibers themselves. In this way the reactivity values are kept high? chemistry and low probability release of the nanoparticles following stress. The nanoparticles 20 are in fact incorporated within the nanofiber 21 as schematically illustrated in Fig.5.

Preferably, the nanofiber layer 11 is functionalized by means of a germicidal chemical agent that can be activated through electromagnetic radiation with a wavelength ? included in the visible spectrum.

The nanofiber layer 11 ? therefore bound (step 120) between two layers of transpiring material 12,13 through the creation of micrometric bonds distributed on the surface of the sandwich created by the three layers 11,12,13. Each constraint? made of measurable dimensions in terms of the diameter of a circumference that inscribes the constraint, having a diameter d less than or at most? equal to 1.0 mm, preferably less or more? equal to 0.5 mm, pi? preferably lower or at the pi? equal to 0.2 mm

The micrometric constraints are made on the surface of the sandwich 11,12,13 with a surface distribution of at least 1 constraint/cm<2>, preferably at least 5 constraints/cm<2>, more? preferably 25 constraints/cm<2>.

Preferably, the micrometric constraints are made in such a way as to define at least two areas A1,A2 with different surface distribution.

According to a preferred embodiment, the micrometric constraints are made according to a grid arrangement, preferably having an interspacing pitch p in the order of a millimetre. In particular, the step p ? between 0.4 mm and 10 mm, preferably between 0.6 mm and 5 mm, more? preferably between 0.8 mm and 2 mm.

In particular, the micrometric constraints are created by applying micrometric spots of adhesive material. This technique is particularly suitable if the layers of transpiring material 12,13 are made with natural or artificial fibres, even if they are different from each other.

Alternatively, in the case of layers in transpiring material 12,13 in synthetic fibers, the micrometric constraints are made by welding, for example by ultrasound, thermal or laser.

The composite material 10 cos? made can? therefore be transformed (step 130) by making cuts, seams and finishes without involving the degradation of the nanomaterial layer 11. Starting from this filtering composite material 10, it is therefore possible to make textile products such as tablecloths, curtains, coverings, clothing or even devices oral-nasal protection essentially able to sanitize itself within a few seconds of exposure to light, as well as possibly reducing the volatile organic compounds (VOCs) present on the fabric and causing bad odours.

Furthermore, composite fabrics and fabrics are so? obtained can be treated, for example by subjecting them to washing and / or ironing always in the absence of degradation of the capacity? filters and possibly the capacity? germicidal and odor reduction of the nanomaterial layer 11.

Claims (10)

1. Filtering composite material (10) comprising at least one intermediate layer in nanomaterials (11) coupled to two layers in transpiring material (12,13) and interposed between them (12,13), the intermediate layer (11) and the layers of transpiring material (12,13) being mutually constrained by means of a plurality? of micrometric constraints created along an overlapping surface of the layers (11,12,13), where the micrometric constraints have dimensions that can be measured in terms of the diameter of a circumference that inscribes each constraint, with the diameter (d) of this circumference smaller or equal to 1.0mm. 2. Composite filter material (10) according to claim 1, wherein the micrometric constraints are distributed over at least a portion of the overlapping surface of the layers (11,12,13) with a surface distribution of at least 1 constraint/cm<2> , preferably at least 5 constraints/cm<2>, pi? preferably at least 25 constraints/cm<2>. 3. Filtering composite material (10) according to claim 1 or 2, wherein the micrometric constraints have a substantially grid-like distribution with an interspacing pitch (p) in the order of a millimetre, preferably with an interspacing pitch (p) between between 0.4 mm and 10 mm, more? preferably with an interspacing pitch (p) between 0.6 mm and 5 mm, even more? preferably with an interspacing pitch (p) between 0.8 mm and 2 mm. 4. Composite filtering material (10) according to any one of the preceding claims, wherein the intermediate layer made of nanomaterials (11) has a thickness, measured in density? of nanomaterials, between 1 g/m2 and 10 g/m2, preferably between 1.2 g/m2 and 8 g/m2, plus? preferably between 1.5 g/m2 and 3 g/m2. 5. Filtering composite material (10) according to any one of the preceding claims, wherein the nanomaterials which make up the intermediate layer (11) comprise nanofibres in flexible material, typically polymeric, of natural or synthetic origin. 6. Composite filter material (10) according to claim 5, wherein the nanomaterials that make up the intermediate layer (11) comprise photocatalytic chemical additives in the form of nanoparticles, preferably nanoparticles of chemical additives activatable through electromagnetic radiation with wavelength (?) included in the visible spectrum or in the ultraviolet spectrum. 7. Composite filter material (10) according to claim 6, wherein the nanoparticles of chemical additives activatable by electromagnetic radiation with a wavelength (?) included in the visible spectrum or in the ultraviolet spectrum comprise nanoparticles of: - nitrogen-doped titanium dioxide (N-TiO2), - zinc oxide (ZnO), - silica (SiO2), 8. Manufacturing process (100) of a filtering composite material (10) comprising the steps consisting of: - forming (step 110) a layer of nanomaterials (11); - constrain the nanomaterial layer (11) to two layers of transpiring material (12,13) and interposed between them (12,13) by creating micrometric constraints distributed along an overlapping surface of the layers (11,12, 13), where the micrometric constraints have dimensions that can be measured in terms of the diameter of a circumference that inscribes each constraint, with the diameter (d) of this circumference less than or equal to 1.0 mm. 9. Manufacturing process (100) according to claim 8, wherein the constraint step (120) comprises making micrometric constraints distributed over at least a portion of the overlapping surface of the layers (11,12,13) with a surface distribution of at least 1 constraint/cm<2>, preferably at least 5 constraints/cm<2>, more? preferably at least 25 constraints/cm<2>. The manufacturing process (100) according to claim 9, wherein the step of making (110) a layer of nanomaterials (11) comprises functionalizing (115) the nanofibers by means of a chemical germicidal agent, preferably a photocatalytic germicidal chemical agent, more preferably a photocatalytic germicidal chemical agent which can be activated by electromagnetic radiation with a wavelength (?) included in the visible spectrum.