Air filtration material, device for decontaminating air by filtration and manufacturing method.

Abstract

The invention relates to a filtering material permeable to air and impermeable to oral, nasal and/or ocular human liquid aqueous excretions, comprising at least one bundle, referred to as a hydrophobic bundle, of at least two hydrophobic sheets which are superimposed and each formed by porous paper, having a gsm substance less than 30 g/m.sup.2, each hydrophobic sheet being formed by cellulose fibres, referred to as cross-linked cellulose fibres, which are connected to each other by hydrogen bonds and by covalent bonds which are formed with at least one group of cross-linking atoms, characterised in that at least some of the hydroxyls of the cross-linked cellulose fibres which are not engaged in hydrogen bonds and which are accessible to the gases form a covalent bond with an acyl group with a hydrophobic chain.

Claims

1. A filtering material that is permeable to air and impermeable to human oral, nasal and/or ocular aqueous liquid excretions, comprising: at least one wad, termed a hydrophobic wad, of at least two hydrophobic sheets that are superimposed and each formed by porous paper with a grammage of less than 30 g/m.sup.2, each hydrophobic sheet being formed by cellulose fibers, termed cross-linked cellulose fibers, bonded together by means of hydrogen bonds and by means of covalent bonds formed with at least one group of cross-linking atoms, wherein at least a portion of the hydroxyls of said cross-linked cellulose fibers that are not involved in the hydrogen bonds and that are accessible to gases form a covalent bond with an acyl group containing a hydrophobic chain.

2. The material as claimed in claim 1, wherein said material comprises at least one wad, termed a hydrophilic wad, of at least one sheet formed by porous hydrophilic paper with a grammage of less than 30 g/m.sup.2, said at least one sheet of porous hydrophilic paper being formed by cellulose fibers bonded together at least by means of hydrogen bonds; said at least one hydrophobic wad and said at least one hydrophilic wad being superimposed one upon the other in a manner such as to form a stack of superimposed porous sheets that is suitable for a flow of air that is to be filtered to pass through, by which means the air of the flow of air passing through the filtering material is filtered, and; at least one hydrophilic wad forming a free principal face of the stack of superimposed porous sheets, said free principal face being a free face for receiving a flow of air that is to be filtered.

3. The material as claimed in claim 2, wherein each of the two free faces of the stack of superimposed porous sheets is formed by a hydrophilic wad, at least one hydrophobic wad being interposed between the hydrophilic wads forming the two free faces of the stack of superimposed porous sheets.

4. The material as claimed in one of claim 1, wherein at least two sheets of said hydrophobic wad are assembled by means of at least one material, termed the assembly material, which is a permeable solid comprising at least one thermoplastic polymer.

5. The material as claimed in claim 4, wherein at least one thermoplastic polymer is selected from the group formed by polyethylenes, polypropylenes, polyamides and poly-L-lactic acids.

6. The material as claimed in claim 4, wherein the thermoplastic polymer extends only at the peripheral border of the stack of superimposed porous sheets.

7. The material as claimed in one of claim 1, wherein at least one acyl group containing a hydrophobic chain is selected from the group formed by a palmityl group, a stearyl group and a behenyl group.

8. The material as claimed in claim 1, wherein each sheet of the stack of superimposed porous sheets is formed by a portion of the thickness of a disposable paper tissue.

9. A device for the decontamination of air by filtration, comprising: a filtration means comprising a filtering material as claimed in claim 1, and; means for adjusting these filtration means on an individual.

10. The device as claimed in claim 9, wherein the dimensions of the filtration means are such as to be capable of covering at least the mouth and the nose of an individual wearing the air decontamination device, the air decontamination device being in the form of a mask, a hood, a balaclava, a ski mask, a shirt, a tunic, or a tissue.

11. A method for the production of a filtering material as claimed in claim 1, in which: at least two first sheets are selected, each formed by porous paper with a grammage of less than 30 g/m.sup.2, each first sheet being formed by cellulose fibers, termed cross-linked cellulose fibers, bonded together by means of hydrogen bonds and by means of covalent bonds formed with at least one group of cross-linking atoms; said at least two first porous sheets undergo a reaction for the acylation of the cellulose fibers in a manner such as to form at least two first porous hydrophobic sheets, during which; each first sheet is impregnated with at least one fatty acid chloride; a flow of a gaseous composition that is heated to a temperature that can enable said acylation reaction to take place between the cellulose of each first sheet and at least one fatty acid chloride in the gaseous state is applied to each first sheet, by which means at least two porous hydrophobic sheets formed by cellulose fibers are formed; which are bonded together by means of hydrogen bonds and by means of covalent bonds formed with at least one group of cross-linking atoms; and in which at least a portion—in particular the entirety—of the hydroxyls that are not involved in a hydrogen bond or in a covalent bond with said at least one group of cross-linking atoms form a covalent bond with an acyl group containing a hydrophobic chain; then said at least one hydrophobic wad of filtering material is formed by stacking said at least two first porous hydrophobic sheets.

12. The method as claimed in claim 11, wherein: at least one second hydrophilic sheet is selected, formed by porous paper with a grammage of less than 30 g/m.sup.2, each second sheet being constituted by cellulose fibers bonded together by means of hydrogen bonds and by means of covalent bonds formed with at least one group of cross-linking atoms; said at least one hydrophilic wad is formed by stacking each second hydrophilic sheet; and said at least one hydrophobic wad and said at least one hydrophilic wad are superimposed in a manner such as to form a stack of superimposed porous sheets such that at least one hydrophilic wad forms a free face of the stack of superimposed porous sheets and of filtering material.

13. The method as claimed in claim 11, wherein a step is carried out for assembling at least two porous sheets of the stack of superimposed porous sheets by heat sealing with at least one material, termed the assembly material, which is a permeable solid comprising at least one thermoplastic polymer.

14. The method as claimed in claim 11, wherein each first sheet respectively formed by porous paper with a grammage of less than 30 g/m.sup.2 and each second sheet respectively formed by porous paper with a grammage of less than 30 g/m.sup.2 is formed by a portion of the thickness of a disposable paper tissue.

15. The method as claimed in claim 11, wherein the filtering material is shaped, by which means a device for the decontamination of air by filtration is formed.

Description

[0086] Other aims, features and advantages of the invention will become apparent from the following description, given by way of illustration, of certain embodiments made with reference to the accompanying drawings, in which:

[0087] FIG. 1 is a representation of a first particular embodiment of a device for the decontamination of air in accordance with the invention;

[0088] FIG. 2 is a schematic representation in cross section of a first embodiment of a filtering material in accordance with the invention;

[0089] FIG. 3 is a schematic representation in cross section of a second embodiment of a filtering material in accordance with the invention, and;

[0090] FIG. 4 is a representation of a second particular embodiment of a device for the decontamination of air in accordance with the invention.

[0091] Clearly, the dimensions and the proportions of the filtering materials and of the air decontamination device shown in FIGS. 1, 2 and 3 are not necessarily true to scale, for the purposes of clarity of the representation.

[0092] The device 10 for the decontamination of air shown in FIG. 1 is a respiratory protection mask dimensioned to be capable of covering the mouth and the nose of an individual. It comprises a filtration means 11 forming a filtering material in accordance with the invention, and means 9 for adjusting these filtration means 11 on an individual. The means 9 for adjusting the filtration means 11 are formed by two ties secured to the filtration means 11, enabling the filtration means 11 to be retained when applied to the face of an individual.

[0093] A schematic representation in cross section of a first embodiment of a filtering material of a device 10 in accordance with the invention for the decontamination of a flow of contaminated air 3 is shown in FIG. 2. The filtering material shown in FIG. 2 comprises a stack of a porous hydrophobic sheet 2 and a porous hydrophilic sheet 1. The porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 are assembled by bonding by means of an assembly material 5 extending at the periphery of the stack of superimposed porous sheets. The assembly material 5 is formed by a thermoplastic polymer. Any other ways of assembling the porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 are possible. It is possible to assemble the porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 using staples. Not assembling the porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 using specific means is also a possibility; the porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 may be held in place by the individual wearing the device 10 for the decontamination of air.

[0094] The porous hydrophobic sheet 2 is formed by a disposable paper tissue modified by a reaction for covalent grafting of a fatty acid chloride. The porous hydrophobic sheet 2 is permeable to atmospheric air and completely impermeable to any aqueous composition, in particular impermeable to any aqueous composition loaded with infectious viral particles. The porous hydrophobic sheet 2 forms one of the two principal faces of the filtering material. The porous hydrophobic sheet 2 forms the downstream face 8 of the device 10 for the decontamination of air, i.e. the face of the device 10 for the decontamination of air via which a flow of decontaminated air 4 which can be breathed by the individual wearing the decontamination device 10 is emitted. It is entirely possible for the porous hydrophobic sheet 2 to be formed by only a portion of the stacked layers forming a disposable paper tissue and modified by a reaction for covalent grafting of a fatty acid chloride.

[0095] In this embodiment, the porous hydrophilic sheet 1 is an unmodified disposable paper tissue. The porous hydrophilic sheet 1 has absorbent properties so that the aqueous composition loaded with infectious viral particles retained by the porous hydrophobic sheet on the upstream principal face 7 of the decontamination device 10 is entirely retained in the porous hydrophilic sheet 1. It is entirely possible for the porous hydrophilic sheet 1 to be formed by only a portion of the stacked layers forming a disposable paper tissue.

[0096] In the first embodiment shown in FIG. 2, the porous hydrophobic sheet 2 forms one of the two principal faces of the filtering material. The porous hydrophobic sheet 2 forms the downstream face 8 of the device 10 for the decontamination of air, i.e. the face of the device 10 for the decontamination of air via which a flow of decontaminated air 4 which can be breathed by the individual wearing the decontamination device 10 is emitted. In this first embodiment shown in FIG. 2, the porous hydrophilic sheet 1 forms the other of the two principal faces of the filtering material. The porous hydrophilic sheet 1 forms the upstream face 7 of the device 10 for the decontamination of air, i.e. the face of the device 10 for the decontamination of air receiving the flow of contaminated air 3 by inhalation by the individual wearing the decontamination device 10.

[0097] The device 10 for the decontamination of air can be used to decontaminate a flow of contaminated air 3 transporting infectious viral particles and to form a flow of substantially decontaminated air 4 that is capable of being breathed by the individual wearing the decontamination device 10, without a risk of infection. However, the device 10 for the decontamination of air also and highly advantageously permits the infectious viral particles to be retained in the porous hydrophilic sheet 1 and/or in the space separating the porous hydrophilic sheet 1 and the porous hydrophobic sheet 2, avoiding contamination of persons moving around the individual wearing the device 10 for the decontamination of air, and because of this decontamination. Advantageously, the device 10 for the decontamination of air is intended to be destroyed and rendered inert after use. Destruction of this type is advantageously carried out by incineration.

[0098] A schematic representation in cross section of a second embodiment of a filtering material of a device 10 in accordance with the invention for the decontamination of a flow of contaminated air 3 is shown in FIG. 3. The filtering material shown in FIG. 3 comprises a stack of a first porous hydrophilic sheet 1 extending at the upstream face 7 of the decontamination device 10, a porous hydrophobic sheet 2 and a second porous hydrophilic sheet 1 extending at the downstream face 8 of the decontamination device 10, the porous hydrophobic sheet 2 being interposed between the first and second porous hydrophilic sheets. The upstream face 7 of the decontamination device 10 is intended to receive a flow of contaminated air 3 and the downstream face 8 is that one of the two principal faces of the device 10 for the decontamination of air from which a flow of decontaminated air 4 which can be breathed by the individual wearing the decontamination device 10 is emitted.

[0099] The porous hydrophobic sheet 2 and the porous hydrophilic sheets 1 are assembled by bonding by means of an assembly material 5 extending at the periphery of the stack of superimposed porous sheets and between the porous hydrophobic sheet 2 and each of the porous hydrophilic sheets 1. The assembly material 5 is formed by a thermoplastic polymer. Any other ways of assembling the porous hydrophobic sheet 2 and the porous hydrophilic sheet 1 are possible.

[0100] The porous hydrophobic sheet 2 is formed by a disposable paper tissue modified by a reaction for covalent grafting of a fatty acid chloride. The porous hydrophobic sheet 2 is permeable to atmospheric air and completely impermeable to any aqueous composition, in particular impermeable to any aqueous composition loaded with infectious viral particles.

[0101] In this embodiment, each porous hydrophilic sheet 1 is formed by an unmodified disposable paper tissue or by at least a portion of the thickness of a disposable paper tissue. Each porous hydrophilic sheet 1 has absorbent properties so that the aqueous composition loaded with infectious viral particles retained by the porous hydrophobic sheet 2 on one or the other of the two principal faces 7,8 of the decontamination device 10 is entirely absorbed by one or the other of the porous hydrophilic sheets 1 situated at the upstream face 7 or downstream face 8 of the decontamination device 10.

[0102] The device 10 for the decontamination of air can be used to decontaminate a flow of contaminated air 3 transporting infectious viral particles and to form a flow of substantially decontaminated air 4 that is capable of being breathed by a healthy individual wearing the decontamination device 10, without a risk of infection. The device 10 for the decontamination of air can also be used to decontaminate a flow of contaminated air that is transporting infectious viral particles emitted by an infected individual and who might contaminate their environment and to form a flow of substantially decontaminated air that can be inhaled by any healthy individual not wearing a decontamination device 10, without a risk of infecting that healthy individual.

[0103] However, the device 10 for the decontamination of air also and highly advantageously enables the infectious viral particles to be retained in one or the other of the first and second porous hydrophilic sheets 1 and/or in the space separating the porous hydrophobic sheet 2 and one or the other of the first and second porous hydrophilic sheets 1, preventing contamination of persons moving around the individual wearing the device 10 for the decontamination of air, and because of this decontamination.

[0104] The device 10 for the decontamination of air shown in FIG. 4 is a respiratory protection mask dimensioned to be able to cover the mouth, the nose and the chin of an individual. It comprises a filtration means 11 formed by a filtering material in accordance with the invention, and means 9 for adjusting these filtration means 11 on that individual. The means 9 for adjusting the filtration means 11 are formed by two ties attached securely to the filtration means 11, enabling the filtration means 11 to be retained when applied to the face of an individual.

[0105] Example 1—Impermeability to water of filtering material in accordance with the invention—Preparation of a porous hydrophobic sheet in accordance with the invention. The four secondary layers forming a disposable paper tissue (Kleenex®, Kimberly-Clark Corporation) were separated into two groups of two secondary layers with dimensions of 21 cm×21 cm square. Each group of two secondary layers formed a porous hydrophilic sheet in accordance with the invention. Each porous hydrophilic sheet formed by a disposable paper tissue had a respective mass of 1 g (22 g/m.sup.2). One of the porous hydrophilic sheets was immersed in a solution of stearic acid chloride in petroleum ether 100-150. The ratio of the mass of stearic acid chloride to the mass of petroleum ether 100-150 was 0.5%. The quantity of solution retained by the porous hydrophilic sheet was 1.5 g and the quantity of stearic acid chloride retained was 0.015 g, corresponding to 1.5% of the mass of the porous hydrophilic sheet. The major proportion of the solvent was allowed to evaporate spontaneously under an extractor hood and then the porous hydrophilic sheet was placed in a ventilated oven heated to 150° C. The reaction was allowed to continue for 2 minutes, by which means a porous hydrophobic sheet was formed by the disposable tissue. In the absence of a ventilated oven, it would have been entirely possible to use a. hair dryer to produce the hydrochloric acid formed during the reaction (by displacing the acylation reaction equilibrium), to heat the porous hydrophilic sheet, to form stearic acid chloride in the gaseous state and to enable the formation of the porous hydrophobic sheet by the reaction of stearic acid chloride in the gaseous state on the porous hydrophilic sheet.

[0106] By way of comparison, a porous hydrophilic sheet formed by two secondary layers of toilet paper with dimensions of 12 cm×10 cm and with a grammage of 41 g/m.sup.2 was prepared. The mass of the porous hydrophilic sheet was 0.5 g. The porous hydrophilic sheet was immersed in a solution of stearic acid chloride in petroleum ether 100-150. The ratio of the mass of stearic acid chloride to the mass of petroleum ether 100-150 was 1%. The quantity of solution retained by the porous hydrophilic sheet was 0.8 g and the quantity of stearic acid chloride retained was 0.008 g, corresponding to 1.6% of the mass of the porous hydrophilic sheet. The major proportion of the solvent was allowed to evaporate spontaneously under an extractor hood and then the porous hydrophilic sheet was placed in a ventilated oven heated to 150° C. The reaction was allowed to continue for 2 minutes, by which means a porous hydrophobic sheet was formed by the toilet paper.

[0107] A first pouch, termed the tissue pouch, was prepared by suspending the porous hydrophobic sheet prepared from the tissue by its four corners. A second pouch, termed the toilet paper pouch, was prepared by suspending the porous hydrophobic sheet prepared from toilet paper by its four corners. The same quantity of water was poured into said tissue pouch and into said toilet paper pouch. Water did not leak instantaneously from either of the two pouches. Said tissue pouch appeared to be completely watertight over a period of more than 4 days. Said toilet paper pouch lost all of its water after 24 hours.

[0108] Example 2—Contact angle. A porous hydrophilic sheet formed by two of the four secondary layers forming a disposable paper tissue (Kleenex®, Kimberly-Clark Corporation) with dimensions of 21 cm×21 cm square was treated as described in Example 1. The porous hydrophilic sheet was treated with a solution of behenic acid chloride in petroleum ether 100-150. The ratio of the mass of behenic acid chloride to the mass of petroleum ether 100-150 was 0.75%. The temperature of the oven was raised to 160° C. A porous hydrophobic sheet was formed by a disposable paper tissue. A 200 μL droplet of distilled water was disposed on the surface of the porous hydrophobic sheet. The droplet remained in shape on the surface of the porous hydrophobic sheet without spreading. Thus, the contact angle was close to 180°.

[0109] Example 3—Mask for the decontamination of air by filtration. A porous hydrophobic sheet was prepared as described in Example 1. A porous hydrophilic sheet comprising a single secondary layer was also prepared from four secondary layers forming a disposable paper tissue (Kleenex®, Kimberly-Clark Corporation) with dimensions of 21 cm×21 cm square. The porous hydrophobic sheet and the porous hydrophilic sheet formed thereby were superimposed and a gauze of heat fusible polymer of the type used for making hems was interposed between the borders of the porous hydrophobic sheet and the porous hydrophilic sheet. The porous hydrophobic and hydrophilic sheets were assembled by heat sealing using a hot electric iron, The filtering material formed comprised a porous hydrophobic sheet formed by two secondary layers of a disposable paper tissue and one porous hydrophilic sheet formed by a single secondary layer of a disposable paper tissue. The filtering material in accordance with the invention was folded then stapled to the elastic elements at two of its opposed ends in order to form a mask for the decontamination of air by filtration in accordance with the invention. The decontamination mask was ready for use. It is possible to use it with the porous hydrophilic sheet directed towards the individual wearing the decontamination mask or with the porous hydrophobic sheet directed towards the individual wearing the decontamination mask, depending on whether protection of the individual from the environment is desired (porous hydrophilic sheet oriented towards the outside) or whether protection of the environment from the individual is desired (porous hydrophilic sheet oriented towards the individual).

[0110] Example 4—Variation of a mask for the decontamination of air by filtration in the form of a “duckbill”. A paper filtration device of the “coffee filter No. 4” type was selected. A large number of small holes was made in the paper in order to make the coffee filter porous while preserving its mechanical stiffness. The two outer faces of the coffee filter were covered with pieces of filtering material with appropriate dimensions as described in Example 1, by interposing a strip of heat fusible polymer gauze on the borders of the coffee filter between the coffee filter paper and the border of each piece of filtering material. Assembly was carried out by heat sealing with the aid of a hot electric iron, Next, elastic elements were stapled onto either side of the filter. The air decontamination mask was ready for use.

[0111] Example 5—Production of a filtering, watertight and absorbent tissue. A porous hydrophobic sheet was produced which comprised two secondary layers of a disposable tissue (Kleenex®, Kimberly-Clark Corporation) comprising four secondary layers, as described in Example 1. The porous hydrophobic sheet formed in this way was superimposed with a porous hydrophilic sheet formed by two secondary layers of a disposable paper tissue comprising four secondary layers. A strip of fusible gauze was interposed between the borders of the two porous hydrophobic and hydrophilic sheets and assembly was carried out by heat sealing, by application of a hot electric iron. The tissue was ready for use.

[0112] Example 6—Production of a second variation of a watertight and absorbent high filtration capacity tissue. The hydrophobic treatment as described in Example 1 was carried out on a complete tissue comprising four secondary layers in order to form a porous hydrophobic sheet comprising four secondary layers. The hydrophobic sheet formed was superimposed with a porous hydrophilic sheet formed by four secondary layers of paper from a disposable paper tissue. A strip of fusible gauze was interposed between the borders of the two porous hydrophobic and hydrophilic sheets and assembly was carried out by heat sealing by the application of a hot electric iron. A high filtration capacity tissue was ready for use.

[0113] Example 7—Production of a watertight and absorbent glove. Two pieces of filtering material as described in Examples 1, 3, 5 or 6 were prepared. Two hand shapes that were mirror images of each other were cut out with a die. A strip of heat fusible material gauze was interposed at the border of the cut pieces. Assembly was carried out by heat bonding by the application of a hot electric iron. As an alternative, it is entirely possible to use a 3D printer in order to deposit a strip of a heat fusible material completely around the shape.

[0114] Example 8—Manual production of a protective mask as illustrated in FIG. 4.

[0115] A piece of filtering material in accordance with the invention was prepared in the form of a disposable paper tissue forming an air filtration means 11. In a first step, one of the borders of the tissue was folded over in order to form a hem for receiving a section of a solid deformable material with low elasticity and a cord for adjustment of this filtration means on an individual. The low elasticity deformable solid section of material could be a copper wire, in particular a copper wire provided with a protective sheath. The diameter of the copper wire in cross section was preferably comprised between 1 mm and 1.5 mm in order to enable the protective mask to be retained on the nose of an individual. The adjustment cord may or may not be a textile elastic cord. The hem was sealed by heat sealing by means of a strip of heat fusible gauze. Any other means for sealing may be used, for example staples. Next, one of the two corners of the piece of filtering material opposite to the hemmed border was folded back onto the other by superimposing one of the two portions of the borders formed because of this folding onto the other. This superimposition was secured by longitudinal folding and locking the secured fold formed by means of staples or an assembly means of the paperclip type. It is entirely possible to secure this superimposition by bonding. The protective device was a mask in the form of a cone which fitted the face perfectly. The electrical cable allowed the mask to be adjusted and held on the nose. It was possible to adapt the depth of the mask by adjusting the longitudinal fold. A protective device was obtained that had a high efficiency in the filtration of human oral, nasal and/or ocular aqueous liquid excretions which could be obtained at low cost starting from a disposable paper tissue.

[0116] A number of variations and applications other than those described above may form the subject matter of a number of variations. In particular, it is clear that unless indicated otherwise, the various structural and functional features of each of the embodiments described above must riot be considered to be combined and/or closely and/or inextricably linked one to the other but, in contrast, should be considered to be simple juxtapositions. Furthermore, the structural and/or functional features of the various embodiments described above may form the subject matter as a whole or in part of any different juxtaposition or any different combination.