Patent Publication Number: US-2022233982-A1

Title: Air filtering element

Description:
FIELD OF APPLICATION 
     The present invention relates to an air filtering element and an air ventilation system of a vehicle passenger compartment comprising said air filtering element. 
     The context in which the present invention lies is the automotive sector. In particular, the present invention relates specifically to air that is ventilated in the passenger compartment of a vehicle. 
     STATE OF THE ART 
     In the state of the art, solutions are known for passenger compartment air ventilation systems suitable for conveying, typically by suction, air from the external environment into the passenger compartment of a vehicle. Such systems typically comprise at least one air filtering element suitable, by means of suitable filtering media included therein, to filter external air to prevent unwanted elements from entering the passenger compartment. 
     Filtering media solutions suitable for particulate filtration of solid contaminants, such as dust or dirt, in other words, fine dust, pollen and pollutant particles, are known of. 
     Filtering media solutions suitable to prevent microbes or bacteria from reaching the vehicle passenger compartment are also known of. In these filtering media solutions, in fact, the presence of special antibacterial agents is envisaged to prevent the microbes reaching the filtering medium or forming in the filtering medium from reaching the passenger compartment. 
     Filtering media solutions suitable for odour absorption actions are also known of. 
     In the state of the art, filtering media having different properties or filtering media (e.g., multilayer) combining multiple properties are known of. In order to reduce the space occupied in the vehicle, the latter have become particularly widespread. 
     Such multi-layer medium solutions, however, are complex and costly to implement, especially in those embodiments in which maximum efficiency of each layer is sought. In addition, the greater the number of layers, the greater the overall dimensions of the filtering medium and therefore of the air filtering element. 
     Solution According to the Invention 
     The need is therefore strongly felt to have an air filtering element that solves the aforementioned problems encountered in state-of-the-art solutions, i.e. an air filtering element that has strong filtering characteristics with as simple and small a structure as possible. 
     The object of the present invention is, therefore, to provide an air filtering element that meets this need. 
     Such purpose is achieved by an air filtering element as claimed in claim  1  and by a vehicle passenger compartment air ventilation system comprising said air filtering element according to claim  13 . The claims dependent on these show preferred embodiments involving further advantageous aspects. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will, in any case, be evident from the description given below of its preferred embodiments, made by way of a non-limiting example with reference to the appended drawings, wherein: 
         FIGS. 1 and 1   a  show respectively a schematic cross-section view and an enlargement thereof of a portion of a filtering medium comprised in an air filtering element according to a preferred embodiment of the invention; 
         FIGS. 2 and 2   a  respectively show a schematic cross-section view and an enlargement thereof of a portion of a filtering medium comprised in an air filtering element according to a further preferred embodiment of the invention; 
         FIG. 3  is a photo taken by an electron microscope of a portion of a filtering medium included in an air filtering element according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the appended drawings, reference numeral  1  denotes a filtering medium comprised in an air filtering element according to the present invention. 
     The object of the present invention is, in fact, an air filtering element, for example of a ventilation system, preferably of a vehicle air ventilation system. 
     Such air filtering element comprises a filtering medium  1  suitable for performing a particulate filtration action on the air passing through it. In other words, the filtering medium  1  performs a particulate filtration of solid contaminants, such as dust or dirt, i.e. fine dust, pollen and pollutant particles. 
     In addition, such air filtering element comprises a filtering medium  1  suitable to exert an antimicrobial action, i.e. an action to reduce the microbial and/or bacterial load that forms on the filtering medium  1 . In other words, the filtering medium reduces the microbes and/or bacteria that reach the filtering medium or that form on (or in) the filtering medium. 
     In other words, according to the present invention, the filtering medium  1  is suitable for performing said dual function. 
     Accordingly, the filtering medium  1  is such as to have a dirty side Il and a clean side  12 : in the first side the air to be filtered flows, in the second side filtered air flows. 
     According to a preferred embodiment, the filtering medium  1  comprises a main layer  10 . 
     Preferably, the main layer  10  alone is already suitable to perform said dual function of the filtering medium  1 . 
     According to the present invention, the main layer  10  is made of non-woven fabric. 
     According to the present invention, the main layer  10  comprises synthetic base fibres  110  and antimicrobial agents  120 . 
     In other words, according to the present invention, the main layer  10  is in a non-woven fibre fabric. 
     According to the present invention, the main layer  10  is in a non-woven fabric of synthetic base fibres  110  comprising an antimicrobial agent  120 . In other words, according to the present invention, the main layer  10  is made of non-woven fabric of synthetic base fibres  110  with antimicrobial agent  120  integrated therein. 
     According to a preferred embodiment, the synthetic base fibres  110  have an average diameter of between 5 and 15 μm. 
     According to a preferred embodiment, the synthetic base fibres  110  are made of polypropylene (PP) or polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) or polyamide (PA) and/or a mixture thereof. 
     According to a preferred embodiment, the synthetic base fibres  110  are single-component fibres and/or dual-component fibres. 
     According to the present invention, in addition, said antimicrobial agents  120  are made of metal or a metal compound and/or based on a metal complex and/or based on a metal salt. 
     Preferably, the antimicrobial agents  120  have an average diameter between 1 and 10 μm. 
     Preferably, then, the antimicrobial agents  120  are retained by the synthetic base fibres  110 . 
     Preferably, the antimicrobial agents  120  are embedded (i.e., integrated) within the synthetic base fibres  110 . Preferably, therefore, the antimicrobial agents  120  are embedded in the synthetic base fibres  110 . Preferably, therefore, the antimicrobial agents  120  are at least in part surrounded by the material of which the synthetic base fibres  110  are made. 
     According to a preferred embodiment, the antimicrobial agents  120  are in silver, preferably in the form of silver ions, Ag +. 
     According to the present invention, the main layer  10  in non-woven fabric has a porosity value of between 80% and 95%, preferably between 85% and 95%, preferably between 85% and 93%. Where porosity means the ratio of the total volume of all the pores present in the main layer  10  to the volume of the main layer  10  in its entirety. Preferably, therefore, the main layer  10  is highly permeable. 
     According to the present invention, the main layer  10  has hydrophilic behaviour such as to collect and form aggregates of water, on which the antimicrobial agents act and perform their antimicrobial action. In other words, the main layer  10  has hydrophilic behaviour so as to collect and distribute water on the surface of the non-woven fabric fibres so that the antimicrobial agents  120 , present therein, perform their antimicrobial action. In other words, the main layer  10  has hydrophilic behaviour such that any water/moisture/vapour particles carried in the circulating air stream in the ventilation system are collected by said main layer  10  distributing themselves on the surface of the synthetic base fibres  110  wherein in said collected or intercepted water the antimicrobial agents  120  perform their antimicrobial action. 
     Specifically, in fact, the main layer  10  in non-woven fabric is functionalized to have hydrophilic behaviour. 
     Preferably, the synthetic base fibres  110  are functionalized to have hydrophilic behaviour. In other words, the main layer  10 , in particular, the non-woven fabric, is subject to specific functionalization treatments that thus enable its hydrophilic behaviour. 
     Preferably, the antimicrobial agents  120  are also treated in turn to have hydrophilic behaviour. 
     Preferably, the antimicrobial agents  120  are integrated into the functionalized portions of the synthetic base fibres  110  having hydrophilic behaviour. 
     In other words, the non-woven fabric (comprising the base fibres  110  and the antimicrobial agents  120 ) is treated by functionalizing additives so as to have said hydrophilic behaviour. 
     Preferably, the main layer  10  is suitable for being impregnated with water. Preferably, the main layer  10  is suitable for intercepting water/humidity/vapour particles dispersed in the circulating air in the aeration circuit so as to collect and distribute the water on the surface of the base fibres  110  on which the anti-microbial agents  120  perform their antimicrobial action. 
     Thus, in other words, the main layer  10  exhibits a tendency to wet itself with water and to favour the penetration of water in the porosities present in the non-woven fabric. 
     According to a preferred embodiment, in the production operations of the main layer  10  the polymer granules with which the synthetic fibres are produced, the antimicrobial agents and the functionalizing additives are mixed in the same hopper and with the compound thus obtained the non-woven fabric is produced and thus said main layer  10 . 
     Preferably, the filtering medium  1  is produced by a melt-blown process. 
     According to a preferred embodiment, the elements constituting the main layer  10  are arranged entirely randomly along its length and along its thickness. 
     According to a preferred embodiment, the main layer  10  has a static water contact angle of less than 90°. 
     According to a preferred embodiment, the main layer  10  is between 0.5 and 2 mm thick. 
     In addition, preferably, the main layer  10  has an average pore diameter between 20 and 40 μm, preferably between 25 and 35 μm. 
     According to a preferred embodiment, the main layer  10  is suitable for filtering particles greater than or equal to 2.5 μm without compromising the pressure drop of the system. 
     According to a preferred embodiment, the antimicrobial agent is present in a percentage less than 1% of the total weight of the main layer  10 ; preferably the antimicrobial agent is present in a percentage ranging from 0.005% to 0.025% of the total weight of the main layer  10 . 
     According to a preferred embodiment, the filtering medium  1  of the air filtering element comprises only the main layer  10  described above. 
     According to other embodiments, the filtering medium  1  is a multilayer and comprises in addition to the main layer  10  at least one secondary layer  20 . 
     Preferably, the main layer  10  is positioned upstream of the secondary layer  20  relative to the direction of air circulation. 
     Preferably, the main layer  10  faces the dirty side I 1  so that it is the first layer of the filtering medium  1  that encounters the air. 
     According to a preferred embodiment, the secondary layer  20  is suitable for performing an adsorbent action on gases dispersed in the air through the filtering medium  1 . In particular, the secondary layer  20  comprises adsorbent elements, preferably comprising activated carbons  200 . 
     In other words, the secondary layer  20  is suitable for performing an adsorbent action against gas molecules present in the circulating air stream in the ventilation system. 
     Preferably, the secondary layer  20  in turn has a multi-layer structure comprising two support layers  21 ,  23  and an adsorbent central layer  22 . 
     Preferably, the two support layers  21 ,  23  are made of non-woven fabric composed of synthetic fibres. 
     Preferably, the adsorbent central layer  22  comprises said activated carbon adsorbent elements  200 . 
     According to a preferred embodiment, the filtering medium  1  is in the form of a panel defining the dirty side Il and the clean side  12  on the two opposite faces (being traversable by air in a transverse direction); preferably the filtering medium  1  is of the pleated type. 
     According to a further embodiment, the filtering medium  1  is in tubular form defining the dirty side Il and the clean side  12  on the inside and outside thereof or vice versa (being traversable by air in the radial direction); preferably the filtering medium  1  is of the pleated type, i.e., the filtering medium  1  is of the star type. 
     Furthermore, as mentioned, the invention also relates to a vehicle passenger compartment air ventilation system comprising an air filtering element according to the above description. 
     Innovatively, the air filtering element and the passenger compartment air ventilation system of a vehicle comprising it according to the present invention amply fulfil the above-mentioned purpose by overcoming the problems typical of the prior art. 
     Advantageously, the filtering element has a simplified and inexpensive shape. 
     Advantageously, the filtering element is suitable for performing the desired (multiple) actions on the intake air. Advantageously, the main layer performs both solid filtration and an anti-microbial action. That is, advantageously, the filtering element is suitable for performing particulate filtration while reducing the microbial charge. 
     Advantageously, both particulate filtration and the reduction of microbial/bacterial load are obtained extremely effectively. 
     Advantageously, the highly permeable structure of the main layer formed by the weaving of synthetic fibres functionalized in such a way as to have hydrophilic behaviour and comprising the antimicrobial agent makes it possible to synergistically combine the effect of fine filtration of solid particles with an effective reduction of the bacterial load. 
     Advantageously, the use of an antimicrobial active ingredient incorporated in synthetic fibres makes it possible to avoid the unwanted release of antimicrobial agents into the environment and/or inside the passenger compartment. 
     Advantageously, the incorporation of an antimicrobial agent inside the fibres allows the active ingredient to be kept near the surface of the fibre where the bacteria are located, maximizing the benefit conferred by the presence of a film of water on said fibre and thus the benefit given by the interaction between hydrophilic functionalization and antimicrobial capacity. 
     Advantageously, the integration of the active ingredient inside the fibres allows the duration of the antimicrobial properties to be prolonged up to 10 years, much longer than the solutions in which the antibacterial ingredient is applied as a coating or as a coating on the filtering material that makes up the filtering element. 
     Advantageously, the synergistic effect of the hydrophilic action results in an improvement of the antimicrobial properties. Advantageously, compared to the same main layer without hydrophilic functionalization, the main layer of the present invention entails an increase to the order of 20% in the reduction of the bacterial load in the air. 
     Advantageously, the antibacterial action of the antimicrobial agents included in the main layer is more effective in that the presence of water promotes the migration of bacteria onto the surface of the fibres where they are subsequently effectively attacked by the antimicrobial agents. 
     Advantageously, the hydrophilic functionalization of the synthetic fibres that make up the non-woven fabric allows the antimicrobial treatment to be extended in the main layer practically in its entirety, i.e. in its thickness, and surface extension, maximizing the filtering element&#39;s reduction capacity both on the outer surface and inside the porosities of the filtering medium and in general in the portions of the filtering medium in which the formation of bacteria and microbes is favoured. 
     Advantageously, the filtering medium can be designed as a multi-layer. 
     Advantageously, in the embodiment of a multilayer filtering medium comprising an adsorbent secondary layer combined with the main layer an increase in particle efficiency has been found. 
     It is clear that a person skilled in the art may make modifications to the air filtering element and to the air ventilation system for the passenger compartment of a vehicle described above so as to satisfy contingent requirements, all contained within the scope of protection as defined by the following claims. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Air filtering element 
           10  main body 
           110  synthetic base fibres 
           120  antimicrobial agents 
           20  secondary layer 
           21  support layer 
           22  central adsorbent layer 
           23  support layer 
           200  activated carbon elements 
         I 1  clean side 
         I 2  dirty side