WO2025088016A1

WO2025088016A1 - Filter element for an aerosol-generating article comprising two porous materials

Info

Publication number: WO2025088016A1
Application number: PCT/EP2024/080036
Authority: WO
Inventors: Rui Nuno Rodrigues Alves BATISTA; Keenan Michael THOMPSON; Yedige ZHUZIMKUL
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-10-26
Filing date: 2024-10-24
Publication date: 2025-05-01
Anticipated expiration: 2026-04-26

Abstract

The invention relates to a filter element (100) for use in an aerosol-generating article. The filter element comprises a filtration material (102). The filtration material comprises a porous foamed material (106) dispersed in a porous fibrous material (104).

Description

FILTER ELEMENT FOR AN AEROSOL-GENERATING ARTICLE COMPRISING TWO POROUS MATERIALS

The present invention relates to a filter element for use in an aerosol-generating article. The present invention relates to an aerosol-generating article comprising the filter element.

It is known to provide an aerosol-generating device for generating an inhalable vapor. Such devices may heat aerosol-forming substrate to a temperature at which one or more components of the aerosol-forming substrate are volatilised without burning the aerosolforming substrate. Aerosol-forming substrate may be provided as part of an aerosol-generating article. The aerosol-generating article may have a rod shape for insertion of the aerosolgenerating article into a cavity, such as a heating chamber, of the aerosol-generating device. A heating element may be arranged in or around the heating chamber for heating the aerosolforming substrate once the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device. The article may comprise a filter element. The filter element may comprise a plastic material, such as cellulose acetate tow.

It would be desirable to provide a filter element offering improved sustainability. It would be desirable to provide a filter element with reduced environmental impact. It would be desirable to provide a filter element of reduced dimensions. It would be desirable to provide a filter element having improved filtration properties. It would be desirable to provide a filter element having improved filtration efficiency. It would be desirable to provide a filter element with tuneable filtration properties. It would be desirable to provide a filter element which can be cost efficiently produced. It would be desirable to provide a filter element with tuneable airflow properties. It would be desirable to provide a filter element with improved airflow properties.

According to an embodiment of the invention there is provided a filter element for use in an aerosol-generating article. The filter element may comprise a filtration material. The filtration material may comprise a porous foamed material dispersed in a porous fibrous material.

According to an embodiment of the invention there is provided a filter element for use in an aerosol-generating article. The filter element comprises a filtration material. The filtration material comprises a porous foamed material dispersed in a porous fibrous material.

The filter element may offer improved sustainability. The filter element may have reduced environmental impact. The filter element may be of reduced dimensions. The filter element may be of compact size. The filter element may have improved filtration properties. The filter element may have improved filtration efficiency. The filter element may provide tuneable filtration properties. The filter element may be cost efficiently produced. The filter element may provide tuneable airflow properties. The filter element may provide improved airflow properties.

The filter element described herein may replace existing non-biodegradable filter elements at a comparable performance. The filter element described herein may replace existing plastic filter elements at a comparable performance. The filter element described herein may replace existing cellulose acetate filter elements at a comparable performance.

The filtration material may be free of cellulose acetate. The porous foamed material may be free of cellulose acetate. The porous fibrous material may be free of cellulose acetate.

The filtration material may consist of the porous foamed material dispersed in the porous fibrous material. The porous fibrous material may be embedded within the porous fibrous material. The porous foamed material may be dispersed throughout the porous fibrous material.

The porous foamed material may be a foam. The porous foamed material may be a dry foam. The porous foamed material may be a solid foam. A dry foam may refer to a material formed from pockets filled with air or other gas in a solid. A dry foam may refer to a material that has been formed from a wet foam by drying the wet foam.

A wet foam may refer to a material formed from pockets of air or other gas in a liquid.

A material having an open-cell structure may refer to a material comprising fluidly interconnected pockets of air or other gas in a solid.

The foam may be produced by preparing a wet foam from a dispersion and removing the liquid dispersion medium. The dispersion may be a dispersion of cellulosic material in a liquid dispersion medium. The wet foam may be produced from the dispersion by agitating the dispersion or otherwise introducing bubbles of air into the dispersion. The dispersion medium may be removed by evaporation, freeze drying or supercritical drying.

“Pore” may refer to a pocket filled with air or other gas which is defined by a wall at least partially surrounding the pocket.

The porous fibrous material may be biodegradable. The porous fibrous material may be recyclable.

The porous fibrous material may be configured as a solid cylindrical rod. The porous foamed material may be dispersed in the solid cylindrical rod of the porous fibrous material. The porous fibrous material may be configured as a solid cube. The porous foamed material may be dispersed in the solid cube of porous fibrous material.

The porous fibrous material may be configured as a matrix for the porous foamed material. The filtration material may comprise a matrix made from porous fibrous material with the porous foamed material dispersed within the matrix of porous fibrous material. The filtration material may consist of the matrix made from porous fibrous material with the porous foamed material dispersed throughout the matrix of porous fibrous material. The porous foamed material may be embedded within the matrix of the porous fibrous material. The matrix of porous fibrous material may be cylindrically-shaped. The matrix of porous fibrous material may be cuboid-shaped. The matrix of porous fibrous material may be a rod. The porous foamed material may be homogeneously dispersed throughout a matrix of porous fibrous material.

The filter element may comprise a core made of the filtration material. The core may be solid cylindrically-shaped. The core may be a rod. The core may be cuboid-shaped.

The filter element may comprise a proximal end. The filter element may comprise a distal end. The filtration material may be arranged between the proximal end of the filter element and the distal end of the filter element. The filtration material may extend between the proximal end of the filter element and the distal end of the filter element. The proximal end of the filter element and the distal end of the filter element may be fluidly connected via the filtration material. The proximal end of the filter element and the distal end of the filter element may be fluidly connected via the core of filtration material.

A porosity of the porous foamed material may be different to a porosity of the porous fibrous material. A density of the porous foamed material may be different to a density of the porous fibrous material.

“Porosity" may refer to the volume fraction of void space in a material or component. “Porosity" may refer to the volume fraction of void space in the porous foamed material. For example, if 60% of a volume of the porous foamed material were unfilled by solid material, the porous foamed material would have a porosity of 0.6. “Porosity" may refer to the volume fraction of void space in the filter element.

The porous fibrous material may be configured to define an aerosol flow directed substantially along a longitudinal axis of the filter element. The porous fibrous material may be configured to define an air flow directed substantially along a longitudinal axis of the filter element. The porous foamed material may be configured to define a turbulent aerosol flow. The porous foamed material may be configured to define a turbulent air flow. The fragments of porous foamed material discussed below may be configured to define a turbulent aerosol flow. The fragments of porous foamed material discussed below may be configured to define a turbulent air flow. The porous foamed material dispersed in the porous fibrous material may be configured to define a turbulent airflow. The turbulent airflow may at least partially be defined by the porosity of the porous foamed material. The turbulent airflow may at least partially be defined by the size and shape of the fragments of porous foamed material discussed below.

The properties of an air flow through the filter element may be determined by the air flow directed substantially along the direction of longitudinal axis of the filter element defined by the porous fibrous material and the turbulent airflow defined by the porous foamed material. The properties of an aerosol flow through the filter element may be determined by the aerosol flow directed substantially along the longitudinal axis of the filter element defined by the porous fibrous material and the turbulent aerosol flow defined by the porous foamed material. The interplay of the airflow directed substantially along the longitudinal axis of filter element and the turbulent airflow may improve the filtering efficiency of filter element. Due to the interplay of the airflow directed substantially along the longitudinal axis of the filter element and the turbulent airflow, the length of the filter element may be reduced. The dimensions of an aerosolgenerating article comprising the filter element may be reduced.

The properties of the air flow or aerosol flow through the filter element may be tuned by varying one or more of the configuration of the porous fibrous material, the porosity of the porous fibrous material, the density of the porous fibrous material, the configuration of the porous foamed material, the porosity of the porous foamed material, the volume fraction of the porous foamed material in the filtration material, the distribution of the porous found material in the porous fibrous material, the size distribution of the fragments of porous foamed material, the size of the fragments of porous foamed material discussed below, and the shape of the fragments of porous foamed material. For example, by increasing the volume fraction of porous foamed material in the filtration material, turbulent airflow may be increased.

The resistance to draw of the filter element may be tuned by varying one or more of the configuration of the porous fibrous material, the porosity of the porous fibrous material, the density of the porous fibrous material, the configuration of the porous foamed material, the porosity of the porous foamed material, the volume fraction of the porous foamed material in the filtration material, the distribution of the porous found material in the porous fibrous material, the size distribution of the fragments of porous foamed material, the size of the fragments of porous foamed material discussed below, and the shape of the fragments of porous foamed material.

A porosity of the filter element may influence the resistance-to-draw of the filter element. A porosity of the filtration material may influence the resistance-to-draw of the filter element. A porosity of the filtration material may be influenced by one or more of a porosity of the porous fibrous material, a porosity of the porous foamed material and a compression force exerted on the filtration material. The compression force may be exerted by a tipping paper or filter element wrapper discussed below circumscribing the filtration material.

The properties of the filter element may be adjusted in dependence on the characteristics of an aerosol-generating article into which filter element is incorporated. The resistance-to-draw of the filter element may be adjusted in dependence of the characteristics of the aerosol-generating article into which filter element is incorporated. The resistance-to-draw may be determined by the porosity of the filter element. The resistance-to-draw may be substantially determined by the porosity of the filtration material. The resistance-to-draw of an aerosol-generating article comprising the filter element as described herein may be determined by the porosity of the filter element.

The filter element may comprise a first region and second region. The first region may comprise a first filtration material. The second region may comprise a second filtration material. The first filtration material may comprise a first porous fibrous material and a first porous foamed material. The first porous foamed material may be dispersed in the first porous fibrous material. The first porous foamed material may be homogeneously dispersed in the first fibrous material. The second filtration material may comprise a second porous fibrous material and a second porous foamed material. The second porous foamed material may be dispersed in the second porous fibrous material. The second porous foamed material may be homogeneously dispersed in the second fibrous material. The first and second filtration material may be a filtration material described herein

A plurality of fragments of the first porous foamed material may be dispersed in the first porous fibrous material. A plurality of fragments of the second porous foamed material may be dispersed in the second porous fibrous material. A plurality of fragments of the first porous foamed material may be homogeneously dispersed in the first porous fibrous material. A plurality of fragments of the second porous foamed material may be homogeneously dispersed in the second porous fibrous material.

The first porous fibrous material may be different to the second porous fibrous material. The first porous fibrous material may be the same as the second porous fibrous material. The first porous foamed material may be different to the second porous foamed material. The first porous foamed material may be the same as the second porous foamed material. The porosity of the first porous fibrous material may be different to the porosity of the second porous fibrous material. The porosity of the first porous foamed material may be different to the porosity of the second porous foamed material.

The first filtration material may be arranged proximal to the second filtration material. The first filtration material in the second filtration material may be configured to have matching shapes. The first filtration material may be configured as a rod. The second filtration material may be configured as a rod.

The filter element may comprise multiple regions. Each region may comprise a filtration material. Each filtration material may comprise a porous fibrous material and a porous foamed material. For each region, the porous foamed material may be dispersed in the porous fibrous material. For each region, a plurality of fragments of the porous foamed material may be dispersed in the porous fibrous material. At least some of the filtration materials of the regions may be configured to be different from each other. All of the filtration materials of the regions may be configured to be different from each other. The porous fibrous material may differ between regions. The porous foamed material may differ between regions. For each region, the porous foamed material may be dispersed in the porous fibrous material. The filtration material for each region may be a filtration material described herein.

By providing two or more filtration materials, the aerosol flow characteristics of the filter element may be tuneable. By providing two or more filtration materials, the air flow characteristics of the filter element may be tuneable. For example, by combining a first filtration material having first aerosol flow characteristics and a second filtration material having second aerosol flow characteristics in the filter element, the aerosol flow or air flow characteristics of the filter element may be adapted.

The porous foamed material may be homogeneously dispersed in the porous fibrous material. The porous foamed material may be substantially homogeneously dispersed in the porous fibrous material.

The porous foamed material may be homogeneously dispersed throughout the porous fibrous material. The filtration material may comprise the porous foamed material homogeneously distributed in the porous fibrous material. The porous foamed material may be homogeneously distributed throughout the porous fibrous material. The porous foamed material may be uniformly dispersed in the porous fibrous material.

The filtration material may be configured to remove or at least reduce undesired components of the aerosol.

The filter element may comprise a filter element wrapper. The filter element wrapper may be configured to at least partially circumscribe the filtration material. The filter element wrapper may be configured to fully circumscribe the filtration material.

The filter element wrapper may be configured to at least partially surround the filtration material. The filter element wrapper may be configured to fully surround the filtration material. The filter element wrapper may be wrapped around the filtration material.

The filter element wrapper may at least partially circumscribe the porous fibrous material. The filter element wrapper may fully circumscribe porous fibrous material. The filter element wrapper may be wrapped around the porous fibrous material. The filter element wrapper may be wrapped around the core of filtration material. The fifth element wrapper may be configured to be wrapped around a rod of the filtration material. The filter element wrapper may be wrapped around a rod of the porous fibrous material. The filter element wrapper may be wrapped around a cube of the porous fibrous material.

The filter element may consist of the filter element wrapper and the filtration material. The filter element may consist of the filtration material wrapped by the filter element wrapper. The porous fibrous material may be configured to be compressible. The filter element wrapper may be configured to compress the filtration material. The filter element wrapper may be configured to compress the porous fibrous material. The filter element wrapper may be configured to compress the porous foamed material. The filter element wrapper may be configured to squeeze the filtration material. The filter element wrapper may be configured to squeeze the fibrous porous material. The filter element wrapper may be configured to squeeze the fibrous foamed material. The filter element wrapper may be configured to compress the porous fibrous material. The filter element wrapper may be tightened around the filtration material. The filter element wrapper may exert a compressing force on the filtration material. The compression may vary the porosity of the filtration material. The compression may be adjusted to tune the porosity of the filtration material. The resistance to draw of the filter element may be adjusted by the compression. The flow characteristics of the filter element may be adjusted by the compression.

The filter element wrapper may be configured to stabilise the filtration material. The filter element wrapper may be configured to protect the filtration material.

The filter element wrapper may be configured to at least partially circumscribe the first filtration material and the second filtration material. The filter element wrapper may be configured to fully circumscribe the first filtration material and the second filtration material. The filter element wrapper may be configured to fix the relative positions of the first filtration material and the second filtration material.

The filter element wrapper may be permanently attached to the filtration material. The filter element wrapper may be glued to the filtration material by a starch glue.

By permanently attaching filtration material to the filter element wrapper, the filter element may be stabilized.

The filter element wrapper may have a permeability of between 3500 Coresta Units and 12000 Coresta Units.

The filter element wrapper may have a thickness of between 0.2 micrometers and 0.4 micrometers.

The filter element wrapper may have a basis weight of between 10 g/m and 30 g/m, preferably of between 17 g/m and 21 g/m.

The filter element may comprise a tipping paper. The tipping paper may be configured to at least partially circumscribe the filtration material. The tipping paper may be configured to fully circumscribe the filtration material. The tipping paper may be configured to at least partially circumscribe the filter element wrapper. The tipping paper may be configured to fully circumscribe the filter element wrapper. The tipping paper may at least partially surround the filtration material. The tipping paper may fully surround the filtration material. The tipping paper may at least partially circumscribe the porous fibrous material. The tipping paper may fully circumscribe the porous fibrous material. The tipping paper may at least partially surround the porous fibrous material. The tipping paper may fully surround the porous fibrous material. The tipping paper may be wrapped around the filtration material. The tipping paper may be wrapped around the porous fibrous material. The tipping paper and may be wrapped around the rod of the porous fibrous material.

The tipping paper may have a textured surface. The tipping paper may have a textured outer surface. The tipping paper may have an embossed surface. The tipping paper may have an embossed outer surface. The tipping paper may have a smooth surface. The tipping paper may have a smooth outer surface.

The tipping paper may attach the filter element to other components of an aerosolgenerating article into which the filter element is to be incorporated.

The tipping paper may have a permeability of between 380 Coresta Units and 550 Coresta Units.

The tipping paper may have a thickness of between 0.5 micrometers and 1.1 micrometers.

The tipping paper may have a basis weight of between 25 g/m and 60 g/m, preferably of between 30 g/m and 50 g/m.

The porous fibrous material may comprise a plurality of fibers. The fibers may be arranged substantially parallel to a longitudinal axis of the filtration material. The fibers may be regenerated cellulose fibers. A longitudinal axis of the fibers may be arranged substantially parallel to a longitudinal axis of the filtration material. The fibers may be arranged substantially parallel to a longitudinal axis of the filter element. A longitudinal axis of the fibers may be arranged substantially parallel to a longitudinal axis of the filter element.

An air flow through the porous fibrous material may be directed along the direction of longitudinal axis of the fibers. An aerosol flow through the porous fibrous material may directed along the direction of the longitudinal axis of the fibers.

The porous fibrous material may be a regenerated cellulose material. The porous fibrous material may comprise of the regenerated cellulose material. The regenerated cellulose material may comprise regenerated cellulose fibers.

The regenerated cellulose material may be free of cellulose acetate. The porous fibrous material may comprise regenerated cellulose fibres. The porous fibrous material may be made of regenerated cellulose fibres. The regenerated cellulose fibers may be arranged substantially parallel to a longitudinal axis of the filtration material. A longitudinal axis of the regenerated cellulose fibers may be arranged substantially parallel to a longitudinal axis of the filtration material.

Regenerated cellulose fibers may be derived from tobacco. Regenerated cellulose fibers may be derived from tobacco plants stems. As tobacco plant stems exist largely as waste of processing tobacco plants, regenerated cellulose fibers derived from tobacco plant stems may be a sustainable source of fibers. Regenerated cellulose fibers may be obtained from bamboo. Regenerated cellulose fibers may be obtained from bamboo culms. As sustainable bamboo agriculture exists at large scale, and bamboo may be a sustainable source of fibers. As waste of bamboo processing materials may be used to obtain regenerated cellulosic fibers, bamboo may be a sustainable source of regenerated cellulose fibers. The regenerated cellulose material may be derived from one or more of tobacco plant stems and bamboo culms.

The regenerated cellulose fibers may have a uniform length. A length of the regenerated cellulose fibers may be homogenised. A length of the regenerated cellulose fibers may be homogenised using continuous spinning in the regenerating technology. The cellulosic material from which the regenerated cellulose fibers are derived may be obtained from recycling materials.

Homogenization of the length of the regenerated cellulose fibers may be achieved by preparing and dissolving intermediate compounds, such as sodium xanthate or acetate derivatives, along with the regeneration of the fibers. Derivatization of the cellulose fibers may improve the solubility of the the fibers in a solvent. The solvent may be aqueous or nonaqueous. The cellulose structure may be transformed depending on the type of solvent, treatment conditions and the type of fibers to be obtained.

The porous fibrous material may be regenerated cellulose material tow. The porous fibrous material may be regenerated cellulose fiber tow. The porous fibrous material may comprise a bundles of regenerated cellulose fibers.

The fibers may be regenerated cellulose fibers selected from one or more of viscose fibers, rayon fibers, modal fibers, tencel fibers, and lyocell fibers, and any combination thereof. The fibers may be preferably selected from tencel fibers and lyocell fibers. Tencel fibers and lyocell fibers may be biodegradable.

The regenerated cellulose material may have a crystallinity of between 4.7 cN/dtex and 5.5 cN/dtex.

The regenerated cellulose material may have a tensile strength of between 3.4 percent and 4.1 percent.

The regenerated cellulose material may have a bulk density of between 150 kg/m³ and 750 kg/m³, preferably of between 250 kg/m³ and 500 kg/m³. The regenerated cellulose material may have a glass transition temperature of between 150 °C and 190 °C, preferably of between 160 °C and 180 °C.

The regenerated cellulose material may have a melting point of between 220 °C and 300 °C, preferably of between 230 °C and 280 °C.

The regenerated cellulose material may have a specific gravity (25/4 degrees Celsius) of between 1.2 and 1.5, preferably of between 1.3 and 1.4. The regenerated cellulose material may have an elongation at break of between 45 percent and 55 percent.

The filter element may have a solid cylindrical shape. The filter element may have a rod shape. The filter element may be cuboid-shaped. The shape of the filter element may match a shape of an aerosol-generating article to which the filter element is to be incorporated. The shape of the filter element may match the shape of the porous fibrous material.

The filter element may have a circular cross-section. The filter element may have a rectangular cross-section. The filter element may have a substantially circular cross-section. The filter element may have a skewed circular cross-section.

The porous fibrous material may be configured to be cylindrically-shaped. The porous fibrous material may be configured to have a solid cylindrical shape. The porous fibrous material may be a rod. The porous fibrous material may be cuboid-shaped. The porous fibrous material may have a circular cross-section. The porous fibrous material may have a substantially circular cross-section. The porous fibrous material may have a skewed circular cross-section. The porous fibrous material may have a rectangular cross-section.

The filter element of the present invention may be manufactured using standard filter making equipment. The filament may be produced using Korber Hauni KDF LEAD NWT equipment.

The porous foamed material may comprise an open cell foam. The porous foamed material may consist of an open cell foam. The porous foamed material may be an open cell foam.

The porous foamed material may be a foamed cellulosic material. The porous foamed material may be a foam of cellulosic material. The porous foamed material may be manufactured according the method of manufacturing a sheet of foamed cellulosic material as described in European patent application 23206185.3, which is herewith incorporated by reference. The porous foamed material may be the filtration material used in the aerosolgenerating article disclosed in European patent application 23206185.3, which is herewith incorporated by reference. The porous foamed material may be the foamed cellulosic material used in the aerosol-generating article disclosed in European patent application 23206185.3, which is herewith incorporated by reference. A sheet of the foamed cellulosic material may be manufactured using a method comprising the following steps: a) preparing a suspension of cellulosic material, wherein the suspension comprises a foaming agent, b) agitating the suspension of cellulosic material and, optionally, adding hydrophobizing agent to the suspension of cellulosic material to obtain a wet foam of cellulosic material, c) preparing a sheet of the wet foam of cellulosic material and dewatering the sheet of wet foam of cellulose material, d) drying the sheet of wet foam of cellulosic material, e) rewetting the sheet of foam f) adjusting a thickness of the sheet of foam, and g) drying of the foam.

The method may yield a sheet of dry foamed cellulosic material. The method may yield a sheet of dry foam of cellulosic material.

The suspension of cellulosic material may be a suspension of pulp. The suspension of cellulosic material may be a suspension of wood pulp. The suspension of cellulosic material may be a suspension of cellulose. The suspension of cellulosic material may be a suspension of refined cellulose. The suspension of cellulosic material may be a suspension of cellulosic fibers. The suspension of cellulosic material may be a suspension of cellulose fibers.

The cellulosic material may be cellulose. The cellulosic material may be cellulosic fibers. The cellulosic material may be cellulose fibers. The cellulosic material may comprise cellulose. The cellulosic material may comprise cellulosic fibers. The cellulosic material may comprise cellulose fibers. The cellulosic material may be free of cellulose acetate.

The cellulosic material may be based on one of bleached softwood pulp, unbleached softwood pulp, bleached eucalyptus pulp and bleached cotton linter pulp, or any combinations thereof. The cellulosic material may be derived from one of bleached softwood pulp, unbleached softwood pulp, bleached eucalyptus pulp and bleached cotton linter pulp, or any combinations thereof.

The foaming agent may comprise one or more surfactants. Preferably, the foaming agent may be a mixture comprising sodium dodecyl sulphate (SDS) in an amount of about 80 mol-% and polyoxyethylene (20) sorbitan monolaurate in an amount of about 20 mol-%.

Preferably, the hydrophobizing agent may be alkyl ketene dimer (AKD). The hydrophobizing agent may be added to the suspension of cellulosic material at an amount of about 1 weight-% of the suspension.

In step a), the cellulosic material may be refined to between 2 percent and 3 percent. In step a), the conductivity of the suspension of cellulosic material may be adjusted to 1000 pS/cm by adding sodium chloride. In step a), the pH of the suspension of cellulosic material may be adjusted to about 8 by adding sodium hydroxide. In step a), a strength additive may be added to the suspension of cellulosic material. The strength additive may be selected from one or more of sodium carboxymethlycellulose (CMC), microfibrillated cellulose and cellulose nanofibrils.

In step c), the wet foam of cellulosic material may be poured on a hand sheet mould. In step c), the sheet of wet foam of cellulosic material may drained by gravity. In step c), the dewatering may not be performed using a vacuum. In step c), a fabric may arrange on top of the foam to stabilize the foam. In step d) the drying may be performed in an oven at 70 degrees Celsius.

In step e), the foam may be rewetted to 50 percent moisture content. In step e), the sheet of foam may be rewetted by exposing the sheet to an atmosphere having 50 % moisture content for 4 hours.

In step g), the foam may be dried in an oven at 70 degrees Celsius. In step g), the foam may be cured at about 80 degrees Celsius for 2 hours to ensure complete reaction of AKD.

The foamed cellulosic material may be a foam of cellulosic material. The foamed cellulosic material may be a dry foam of cellulosic material. The foamed cellulosic material may be a solid foam of cellulosic material. The foamed cellulosic material may be an open-cell foam. The foamed cellulosic material may be free of cellulose acetate. The foamed cellulosic material may be porous. A density of the foam of cellulosic material may be of between 45 kg/m³ and 105 kg/m³.

The porous foamed material may be prepared from plant-based pulps. The porous foamed material may be prepared from one or more of wood pulp, bamboo pulp, tobacco stem pulp, nanocellulose, and kaolin-microfibrillated cellulose composites.

The porous foamed material may be biodegradable.

The porous foamed material may be derived from one or more of wood pulp, bamboo pulp, and pulp of tobacco stems, or any combination thereof.

The porous foamed material may be a biocomposite foam. The porous foamed material may be a nanocellulose-based foam. The porous foamed material may be a hybrid foam. The porous foamed material may be hybrid foam of nanocellulose and kaolin-microfibrillated cellulose composites. The porous foamed material may be a polyhydroxyalkanoate-based foam. The porous foamed material may be a foam based on polyhydroxy butyrate. The porous foamed material may be a dry foam. The porous foamed material may be a solid foam.

The porous foamed material may be produced by preparing a wet foam from a dispersion and removing the dispersion medium. The dispersion may be a dispersion of cellulosic material. The wet foam may be produced from the dispersion by agitating the dispersion or otherwise introducing bubbles of air into the dispersion. The dispersion medium may be removed by evaporation, freeze drying or supercritical drying. The porous foamed material may have a density of between 15 kg/m³ and 45 kg/m³, preferably of between 20 kg/m³ and 40 kg/m³.

The density of the porous foamed material may be measured according to ISO 845.

The porous foamed material may have a paper mass content of between 70 weight-% and 95 weight-%, preferably of between 75 weight-% and 90 weight-%.

The porous foamed material may comprise a biopolymer in an amount of between 10 weight-% and 25 weight %, preferably of between 15 weight-% and 20 weight-%. The biopolymer may comprise a polyhydroxyalkanoate (PHA). The polyhydroxyalkanoate may be polyhydroxy butyrate. The porous foamed material may comprise a polyhydroxyalkanoate in an amount of between 10 weight-% and 25 weight %, preferably of between 15 weight-% and 20 weight-%. The porous foamed material may comprise a polyhydroxy butyrate in an amount of between 10 weight-% and 25 weight %, preferably of between 15 weight-% and 20 weight- %.

The porous foamed material may comprise a biodegradable thermoplastic. The porous foamed material may be made from a biodegradable thermoplastic. Polyhydroxy butyrate (PHB) may be produced from sugar or from carbon dioxide using cyanobacteria.

The filtration material may comprise a plurality of fragments of the porous foamed material dispersed in the porous fibrous material.

The fragments may be granules of the porous foamed material. The fragments may be fragments of a sheet of the porous foamed material. The fragments of the porous foamed material may be derived from a sheet of the porous foamed material. The fragments may be obtained by tearing off fragments from a sheet of the porous foamed material. The fragments of the porous foamed material may be derived by fragmentation of a sheet of the porous foamed material.

The fragments may have varying shapes. The fragments may have varying sizes.

The filtration material may consist of the fragments of the porous foamed material dispersed in the porous fibrous material. The fragments of the porous fibrous material may be embedded within the porous fibrous material. The fragments of the porous foamed material may be dispersed throughout the porous fibrous material. The porous fibrous material may enclose the fragments of porous foamed material.

The fragments of the porous foamed material may be homogeneously dispersed in the porous fibrous material. The fragments of the porous foamed material may be substantially homogeneously dispersed in the porous fibrous material.

The fragments of the porous foamed material may be homogeneously dispersed throughout the porous fibrous material. The filtration material may comprise a plurality of fragments of the porous foamed material homogeneously distributed in the porous fibrous material. The fragments of the porous foamed material may be homogeneously distributed throughout the porous fibrous material. The fragments of the porous foamed material may be uniformly dispersed in the porous fibrous material. The fragments of the porous foamed material may be dispersed in the solid cylindrical rod of the porous fibrous material.

The porous fibrous material may be configured as a matrix for the fragments of porous foamed material. The filtration material may comprise a matrix made from porous fibrous material with the fragments of porous foamed material dispersed within the matrix of porous fibrous material. The filtration material may consist of the matrix made from porous fibrous material with the fragments of porous foamed material dispersed throughout the matrix of porous fibrous material. The fragments of porous foamed material may be embedded within the matrix of the porous fibrous material. The matrix of porous fibrous material may be cylindrically-shaped. The matrix of porous fibrous material may be a rod. The fragments of porous foamed material may be homogeneously dispersed throughout the matrix of porous fibrous material.

The fragment of porous foamed material may have a volume of between 0.1 mm³ and 0.5 mm³, preferably of between 0.15 mm³ and 0.35 mm³. Each of the fragments of porous foamed material may have a volume of between 0.1 mm³ and 0.5 mm³, preferably of between 0.15 mm³ and 0.35 mm³. The fragments may have a median volume of about 0.25 mm³.

A porosity of the filtration material may be of between 0.3 and 0.8, preferably of 0.4 and 0.7, and more preferably of between 0.5 and 0.6. The porosity may be the ratio of the pore volume of the filtration material and the overall volume of the filtration material.

A porosity of the porous fibrous material may be larger than a porosity of the porous foamed material. The ratio of the porosity of the porous foamed material to the porosity of the porous fibrous material may be of between 1 :1.08 and 1 :1.31 , preferably of between 1 :1.12 and 1 :1.23.

The ratio of the volume of the porous fibrous material and the porous foamed material may be of between 1 :0.1 and 1 :0.4, preferably of between 1 :0.15 and 1 :0.25.

The filter element may comprise a plurality of fragments of the porous foamed material dispersed in the porous fibrous material. The filter element may comprise a plurality of discrete fragments of the porous foamed material dispersed in the porous fibrous material. The filter element may comprise a plurality of discrete fragments of the porous foamed material homogenously dispersed in the porous fibrous material

The fragments of porous foamed material may be obtained by fragmentation of the sheet of porous foamed material. An indentation force deflection (IFD) test value may be determined according ASTM D 3574. The characterization according to ASTM D 3574 may be carried out using 65 % feed. The Indentation force deflection (IFD) test value of the sheet of porous foamed material may be of between 380 Newton and 570 Newton, preferably of between 410 Newton and 500 Newton. A hardness may be determined according to ISO 2439 Method B. The hardness of the sheet of porous foamed material may be of between 75 Newton and 105 Newton, preferably of between 80 Newton and 100 Newton. A compression set value may be determined according to ISO 1856 Method C1. The compression set value may be determined after 2.5 hours. The compression set value of the sheet of porous foamed material may be of between 20 percent and 40 percent, preferably of between 25 percent and 35 percent. A thermal conductivity may be determined according to ISO 8302. The thermal conductivity of the sheet of foamed porous material may be of between 0.025 W/mK and 0.05 W/mK, preferably of between 0.03 W/mK and 0.04 W/mK.

The sheet of porous foamed material may be fragmented to obtain a desired granulometry. The sheet of porous found material may be shredded to obtain the fragments of porous foamed material.

The filter element may comprise the porous fibrous material in the shape of a rod. The porous fibrous material may comprise fibers which have a longitudinal axis of the fibers arranged in parallel with a longitudinal axis of the filter element. The rod of porous foamed material may comprise fragments of the porous foamed material. The fragments of a porous foamed material may be homogeneously dispersed in the rod of porous fibrous material. The fragments of porous foamed material may be uniformly arranged in the rod of porous fibrous material. The filter element wrapper may be wrapped around the rod of porous fibrous material. The filter element wrapper may compress the rod of porous fibrous material. The tipping paper may be wrapped around the filter element wrapper. The flow characteristics of the filter element may be adjusted, amongst others, by varying the porosity of the porous fibrous material, the porosity of the porous foamed material, the relative amounts of porous fibrous material and porous foamed material, the arrangement of the porous foamed material in the porous fibrous material and the compression of the porous fibrous material by the filter element wrapper.

The filtration material may comprise a plasticizer. The plasticizer may be triacetin. The filtration material may comprise triacetin in an amount of between 4 weight-% and 7 weight-%.

The filtration material may be free of plasticizer. The porous fibrous material may be free of plasticizer.

The filtration material may comprise triacetin in an amount of between 4 weight-% and 7 weight-% of the total weight of the filtration material in the filter element.

The filter element may have a length of between 5 millimeters and 21 millimeters, preferably of between 7 millimeters and 11 millimeters.

The filter element may have a diameter of between 3 millimeters and 10 millimeters, preferably of between 4 millimeters and 9 millimeters. In a preferred embodiment of the invention, the filtration material may comprise a plurality of discrete fragments of the porous foamed material homogenously dispersed in the porous fibrous material. The porous fibrous material may comprise a plurality of regenerated cellulose fibers. A longitudinal axis of the fibers may be arranged substantially parallel to a longitudinal axis of the filtration material. The filtration material may be free of cellulose acetate.

The invention further relates to an aerosol-generating article comprising the filter element as described herein and an aerosol-forming substrate.

The aerosol-generating article may be a rod. The aerosol-generating article may be cylindrical. The aerosol-generating article may be cuboid-shaped. The aerosol-generating article may have a circular cross-section. The aerosol-generating article may have a substantially circular cross-section. The aerosol-generating article may have a skewed circular cross-section. The aerosol-generating article may have a rectangular cross-section.

The invention further relates to an aerosol-generating system comprising an aerosolgenerating device as described herein and an aerosol-generating article as described herein.

The invention further relates to a method of manufacturing a filtration material of a filter element for an aerosol-generating device comprising the following steps: a) providing a porous foamed material b) dispersing the porous foamed material in a porous fibrous material.

The filtration material may be the filtration material of the filter element described herein.

As used herein, the terms ‘proximal’, ‘distal’, ‘downstream’ and ‘upstream’ may be used to describe the relative positions of components, or portions of components, of the aerosolgenerating device in relation to the direction in which a user draws on the aerosol-generating device during use thereof.

As used herein, the terms ‘proximal’, ‘distal’, ‘downstream’ and ‘upstream’ may be used to describe the relative positions of components, or portions of components, of the aerosolgenerating article in relation to the direction in which a user draws on the aerosol-generating article during use thereof.

The aerosol-generating device may comprise a mouth end through which in use an aerosol exits the aerosol-generating device and is delivered to a user. The mouth end may also be referred to as the proximal end. In use, a user may draw on the proximal or mouth end of the aerosol-generating device in order to inhale an aerosol generated by the aerosolgenerating device. Alternatively, a user may directly draw on an aerosol-generating article inserted into an opening at the proximal end of the aerosol-generating device. The opening at the proximal end may be an opening of the cavity. The cavity may be configured to receive the aerosol-generating article. The aerosol-generating device may comprise a distal end opposed to the proximal or mouth end. The proximal or mouth end of the aerosol-generating device may also be referred to as the downstream end and the distal end of the aerosol-generating device may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions between the proximal, downstream or mouth end and the distal or upstream end of the aerosol-generating device.

The aerosol-generating article may comprise a mouth end through which in use an aerosol exits the aerosol-generating article and is delivered to a user. The mouth end may also be referred to as the proximal end. The filter element as described herein may be arranged at the mouth end of the article. The aerosol-generating article may comprise a distal end opposed to the proximal or mouth end. The proximal or mouth end of the aerosol-generating article may also be referred to as the downstream end and the distal end of the aerosol-generating article may also be referred to as the upstream end. The filter element is described herein may be arranged proximal to the aerosol-forming substrate.

A longitudinal axis of a component may extend between a proximal end of the component and a distal end of the component. A longitudinal axis of the filter element may extend between a proximal end of the filter element and a distal end of the filter element. A longitudinal axis of the aerosol-generating article may extend between a proximal end of the article and a distal end of the article. A longitudinal axis of the aerosol-generating device may extend between the proximal end of the device and a distal end of the device.

As used herein, an ‘aerosol-generating device’ may relate to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate may be part of the aerosol-generating article. An aerosol-generating device may be a smoking device that interacts with an aerosol-forming substrate of the aerosol-generating article to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth. An aerosol-generating device may be a holder. The device may be an electrically heated smoking device. The aerosol-generating device may comprise a housing, electric circuitry, a power supply, a heating chamber and a heating element.

The aerosol-generating device may comprise electric circuitry. The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor. The microprocessor may be part of a controller. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the heating element. Power may be supplied to the heating element continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff- by-puff basis. The power may be supplied to the heating element in the form of pulses of electrical current. The electric circuitry may be configured to monitor the electrical resistance of the heating element, and preferably to control the supply of power to the heating element dependent on the electrical resistance of the heating element.

The aerosol-generating device may comprise a power supply, typically a battery, within a main body of the aerosol-generating device. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium- Iron-Phosphate, Lithium Titanate or a Lithium-Polymer battery. As an alternative, the power supply may be another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that enables to store enough energy for one or more usage experiences; for example, the power supply may have sufficient capacity to continuously generate aerosol for a period of around six minutes or for a period of a multiple of six minutes. In another example, the power supply may have sufficient capacity to provide a predetermined number of puffs or discrete activations of the heating element.

The cavity of the aerosol-generating device may have an open end into which the aerosol-generating article is inserted. The open end may be a proximal end. The cavity may have a closed end opposite the open end. The closed end may be the base of the cavity. The closed end may be closed except for the provision of air apertures arranged in the base. The base of the cavity may be flat. The base of the cavity may be circular. The base of the cavity may be arranged upstream of the cavity. The open end may be arranged downstream of the cavity. The cavity may have an elongate extension. The cavity may have a longitudinal central axis. A longitudinal direction may be the direction extending between the open and closed ends along the longitudinal central axis. The longitudinal central axis of the cavity may be parallel to the longitudinal axis of the aerosol-generating device.

The cavity may be configured as a heating chamber. The cavity may have a cylindrical shape. The cavity may have a hollow cylindrical shape. The cavity may have a shape corresponding to the shape of the aerosol-generating article to be received in the cavity. The cavity may have a circular cross-section. The cavity may have an elliptical or rectangular crosssection. The cavity may have an inner diameter corresponding to the outer diameter of the aerosol-generating article.

An airflow channel may run through the cavity. Ambient air may be drawn into the aerosol-generating device, into the cavity and towards the user through the airflow channel. Downstream of the cavity, a mouthpiece may be arranged or a user may directly draw on the aerosol-generating article. The airflow channel may extend through the mouthpiece.

In any of the aspects of the disclosure, the heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

As described, in any of the aspects of the disclosure, the heating element may be part of an aerosol-generating device. The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where "internal" and "external" refer to the aerosol-forming substrate. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the center of the aerosol-forming substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

An external heating element may take any suitable form. For example, an external heating element may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the substrate receiving cavity. Alternatively, an external heating element may take the form of a metallic grid or grids, a flexible printed circuit board, a molded interconnect device (MID), ceramic heater, flexible carbon fiber heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heating element may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heating element formed in this manner may be used to both heat and monitor the temperature of the external heating element during operation.

As an alternative to an electrically resistive heating element, the heating element may be configured as an induction heating element. The induction heating element may comprise an induction coil and a susceptor. In general, a susceptor is a material that is capable of generating heat, when penetrated by an alternating magnetic field. When located in an alternating magnetic field. If the susceptor is conductive, then typically eddy currents are induced by the alternating magnetic field. If the susceptor is magnetic, then typically another effect that contributes to the heating is commonly referred to hysteresis losses. Hysteresis losses occur mainly due to the movement of the magnetic domain blocks within the susceptor, because the magnetic orientation of these will align with the magnetic induction field, which alternates. Another effect contributing to the hysteresis loss is when the magnetic domains will grow or shrink within the susceptor. Commonly all these changes in the susceptor that happen on a nano-scale or below are referred to as “hysteresis losses”, because they produce heat in the susceptor. Hence, if the susceptor is both magnetic and electrically conductive, both hysteresis losses and the generation of eddy currents will contribute to the heating of the susceptor. If the susceptor is magnetic, but not conductive, then hysteresis losses will be the only means by which the susceptor will heat, when penetrated by an alternating magnetic field. According to the invention, the susceptor may be electrically conductive or magnetic or both electrically conductive and magnetic. An alternating magnetic field generated by one or several induction coils heat the susceptor, which then transfers the heat to the aerosol-forming substrate, such that an aerosol is formed. The heat transfer may be mainly by conduction of heat. Such a transfer of heat is best, if the susceptor is in close thermal contact with the aerosol-forming substrate.

As used herein, the term ‘aerosol-generating article’ may refer to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be a smoking article that generates an aerosol that is directly inhalable into a user’s lungs through the user's mouth. An aerosolgenerating article may be disposable.

The aerosol-generating article may be a combustible cigarette. The aerosol-generating article may comprise a rod of tobacco and the filter element described herein. The tobacco may be burnt. A user may light the cigarette to burn the tobacco.

As used herein, the term ‘aerosol-forming substrate’ may relate to a substrate capable of releasing one or more volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article. In a combustible cigarette, the substrate may be burnt. The substrate may comprise tobacco.

The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosolforming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise an aerosol former that facilitates the formation of a dense and stable aerosol. Examples of suitable aerosol formers are glycerine and propylene glycol.

The aerosol-generating substrate may comprise homogenised tobacco material, an aerosol-former and water. Providing homogenised tobacco material may improve aerosol generation, the nicotine content and the flavour profile of the aerosol generated during heating of the aerosol-generating article. Specifically, the process of making homogenised tobacco involves grinding tobacco leaf, which more effectively enables the release of nicotine and flavours upon heating.

Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein

Example 1 : A filter element for use in an aerosol-generating article, wherein the filter element comprises a filtration material, wherein the filtration material comprises a porous foamed material dispersed in a porous fibrous material.

Example 2: The filter element according to example 1 , wherein the porous foamed material is homogeneously dispersed in the porous fibrous material.

Example 3: The filter element according to example 1 or example 2, wherein the filter element comprises a filter element wrapper, wherein the filter element wrapper is configured to at least partially, preferably fully circumscribe the filtration material.

Example 4: The filter element according to example 3, wherein the filter element wrapper is permanently attached to the filtration material, preferably wherein the filter element wrapper is glued to the filtration material by a starch glue.

Example 5: The filter element according to example 3 or example 4, wherein the filter element wrapper has a permeability of between 3500 Coresta Units and 12000 Coresta Units.

Example 6: The filter element according to any of examples 3 to 5, wherein the filter element wrapper has a thickness of between 0.2 micrometers and 0.4 micrometers. Example 7: The filter element according to any of examples 3 to 6, wherein the filter element wrapper has a basis weight of between 10 g/m and 30 g/m, preferably of between 17 g/m and 21 g/m.

Example 8: The filter element according to any of the preceding examples, wherein the filter element comprises a tipping paper, wherein the tipping paper is configured to at least partially, preferably fully circumscribe the filtration material, preferably wherein the tipping paper is configured to at least partially circumscribe the filter element wrapper according to any of examples 3 to 7.

Example 9: The filter element according to example 8, wherein the tipping paper has a permeability of between 380 Coresta Units and 550 Coresta Units.

Example 10: The filter element according to example 8 or example 9, wherein the tipping paper has a thickness of between 0.5 micrometers and 1.1 micrometers.

Example 11 : The filter element according to any of examples 8 to 10, wherein the tipping paper has a basis weight of between 25 g/m and 60 g/m, preferably of between 30 g/m and 50 g/m.

Example 12: The filter element according to any of the preceding examples, wherein the porous fibrous material comprises a plurality of fibers, wherein a longitudinal axis of the fibers is arranged substantially parallel to a longitudinal axis of the filtration material, preferably wherein the fibers are regenerated cellulose fibers.

Example 13: The filter element according to example 12, wherein the porous fibrous material is a regenerated cellulose material preferably comprising the regenerated cellulose fibers.

Example 14: The filter element according to example 13, wherein the regenerated cellulose material is derived from one or more of tobacco plant stems and bamboo culms.

Example 15: The filter element according to any of examples 12 to example 14, wherein the fibers are regenerated cellulose fibers selected from one or more of viscose fibers, rayon fibers, modal fibers, tencel fibers, and lyocell fibers, and any combination thereof.

Example 16: The filter element according to any of examples 13 to 15, wherein the regenerated cellulose material has a crystallinity of between 4.7 cN/dtex and 5.5 cN/dtex.

Example 17: The filter element according to any of examples 13 to 16, wherein the regenerated cellulose material has a tensile strength of between 3.4 percent and 4.1 percent.

Example 18: The filter element according to any examples 13 to 17, wherein the regenerated cellulose material has a bulk density of between 150 kg/m³ and 750 kg/m³, preferably of between 250 kg/m³ and 500 kg/m³. Example 19: The filter element according to any examples 13 to 18, wherein the regenerated cellulose material has a glass transition temperature of between 150 °C and 190 °C, preferably of between 160 °C and 180 °C.

Example 20: The filter element according to any examples 13 to 19, wherein the regenerated cellulose material has a melting point of between 220 °C and 300 °C, preferably of between 230 °C and 280 °C.

Example 21 : The filter element according to any of the preceding examples, wherein the filter element has a solid cylindrical shape, preferably wherein the filter element has a rod shape.

Example 22: The filter element according to any of the preceding examples, wherein the porous foamed material comprises, preferably consists of an open cell foam.

Example 23: The filter element according to any of the preceding examples, wherein the porous foamed material is derived from one or more of wood pulp, bamboo pulp, and pulp of tobacco stems, or any combination thereof.

Example 24: The filter element according to any of the preceding examples wherein the porous foamed material has a density of between 15 kg/m³ and 45 kg/m³, preferably of between 20 kg/m³ and 40 kg/m³.

Example 25: The filter element according to any of the preceding examples, wherein the porous foamed material has a paper mass content of between 70 weight-% and 95 weight- %, preferably of between 75 weight-% and 90 weight-%.

Example 26: The filter element according to any of the preceding examples, wherein the porous foamed material comprises a biopolymer in a amount of between 10 weight-% and 25 weight-%, preferably of between 15 weight-% and 20 weight-%, preferably wherein the biopolymer comprises a polyhydroxyalkanoate (PHA), preferably polyhydroxy butyrate.

Example 27: The filter element according to any of the preceding examples, wherein the filtration material comprises a plurality of fragments of the porous foamed material dispersed in the porous fibrous material.

Example 28: The filter element according to example 27, wherein the fragment of porous foamed material has a volume of between 0.1 mm³ and 0.5 mm³, preferably of between 0.15 mm³and 0.35 mm³.

Example 29: The filter element according to any of the preceding examples, wherein a porosity of the filtration material is of between 0.3 and 0.8, preferably of 0.4 and 0.7, and more preferably of between 0.5 and 0.6, wherein the porosity is the ratio of the pore volume of the filtration material and the overall volume of the filtration material.

Example 30: The filter element according to any of the preceding examples, wherein a porosity of the porous fibrous material is larger than a porosity of the porous foamed material, preferably wherein the ratio of the porosity of the porous foamed material to the porosity of the porous fibrous material is of between 1 :1.08 and 1 :1.31 , preferably of between 1 :1.12 and 1 :1.23.

Example 31 : The filter element according to any of the preceding examples, wherein the ratio of the volume of the porous fibrous material and the porous foamed material is of between 1 :0.1 and 1 :0.4, preferably of between 1 :0.15 and 1 :0.25.

Example 32: The filter element according to any of the preceding examples, wherein the filtration material comprises a plasticizer, preferably wherein the plasticizer is triacetin, preferably wherein the filtration material comprises triacetin in an amount of between 4 weight- % and 7 weight-%.

Example 33: The filter element according to any of the preceding examples, wherein the filter element has a length of between 5 millimeters and 21 millimeters, preferably of between 7 millimeters and 11 millimeters.

Example 34: The filter element according to any of the preceding examples, wherein the filter element has a diameter of between 3 millimeters and 10 millimeters, preferably of between 4 millimeters and 9 millimeters.

Example 36: The filter element according to any of the preceding examples, wherein the filtration material is free of cellulose acetate.

Example 36: An aerosol-generating article comprising the filter element according to any of examples 1 to 35 and an aerosol-forming substrate.

Example 37: An aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article according to example 36.

Example 38: A method of manufacturing a filtration material of a filter element for an aerosol-generating device comprising the following steps: a) providing a porous foamed material b) dispersing the porous foamed material in a porous fibrous material.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows a three-dimensional view of a filter element of the present invention;

Fig. 2 shows another three-dimensional view of the filter element of the present invention; and

Fig. 3 shows a longitudinal cross-section of the filter element of the present invention. Fig. 1 shows a three-dimensional view of a filter element 100 of the present invention. The filter element comprises a filtration material 102. The filtration material comprises a porous fibrous material 104. The filtration material comprises a porous foamed material 106. The porous foamed material 106 is homogeneously dispersed throughout the porous fibrous material 104. The porous fibrous material 104 is configured as a solid cylindrical rod. The porous fibrous material 104 is configured as a matrix in which fragments of the porous foamed material 106 are dispersed. The filtration material 102 comprises a filter element wrapper 108. The porous fibrous material 104 is surrounded by the filter element wrapper 108. The filter element wrapper 108 abuts the porous fibrous material 104. The filter element wrapper 108 is in contact with the porous fibrous material 104. The filter element wrapper 108 is arranged radially outward of the porous fibrous material 104 in a direction orthogonal to a longitudinal axis of the filter element. For better visibility of the porous fibrous material 104 and porous foamed material 106 for the reader, the filter element wrapper 108 is shown to be partially removed from the filtration material 102. The filter element wrapper 108 is surrounded by a tipping paper 110. The tipping paper 110 abuts the filter element wrapper 108. The tipping paper 110 is arranged radially outward of the filter element wrapper 108 in a direction orthogonal to the longitudinal axis of the filter element. For better visibility of the porous fibrous material 104, the porous foamed material 106, and the filter element wrapper 108 to the reader, the tipping paper 110 is shown to be partially removed from the filtration material 102.

The porous fibrous material 104 is made of regenerated cellulose fibers. The are arranged substantially parallel to the longitudinal axis of the filtration material (see below Fig. 2).

The filter element 100 may be part of an aerosol-generating article comprising an aerosol-forming substrate. Aerosol may be generated from the aerosol-forming substrate. The aerosol may be pulled through the filter element by the draw of a consumer on the article.

The flow characteristics of the article may be tuned by varying the properties of the porous fibrous material 104, the porous foamed material 106 and a radial compression force on the porous fibrous material 104 exerted by one or both of the filter element wrapper 108 and the tipping paper 110.

The porous fibrous material 104 is configured to facilitate a flow directed substantially parallel to the longitudinal axis of the filter element (longitudinal flow). Fibers constituting the porous fibrous material 104 are be arranged with the longitudinal axes of the fibers being arranged substantially parallel to the longitudinal axis of the filter element 100. The porous foamed material 106 is configured to facilitate a turbulent flow. The longitudinal flow facilitated by the porous fibrous material 104 may be diverted by the fragments of the porous foamed material 106. The longitudinal flow facilitated by the porous fibrous material 104 may enter the porous foamed material 106 and may be diverted due to the porous structure of the porous foamed material. The longitudinal flow facilitated by the porous fibrous material 104 may be diverted around the fragments of the porous foamed material 106.

The compressing force of one both of the filter element wrapper 18 and the tipping paper 110 may be adjusted to tune the porosity of the filtration material.

Fig. 2 shows another three-dimensional view of the filter element 100 of the present invention. The remarks relating to Fig. 1 apply correspondingly to the filter element 100 of Fig. 2. The filter element wrapper 108 and the tipping paper 110 as shown to fully circumscribe the filtration material 102. Fig. 2 further shows a longitudinal axis 112 of the filter element 100. Fig. 3 shows a longitudinal cross-section of the filter element 100 of the present invention. The remarks relating to Figs. 1 and 2 apply correspondingly to the filter element of Fig. 3. In addition, Fig. 3 indicates a length 114 of the filter element 100 and a width 116 of the filter element 100. The fragments of porous foamed material 106 are arranged homogeneously along the length of the filter element 100. The fragments of porous foamed material 106 are arranged homogeneously along the width of the filter element 100.

Claims

1. A filter element for use in an aerosol-generating article, wherein the filter element comprises a filtration material, wherein the filtration material comprises a porous foamed material dispersed in a porous fibrous material, wherein the ratio of the volume of the porous fibrous material and the porous foamed material is of between 1 :0.1 and 1 :0.4.

2. The filter element according to claim 1 , wherein the porous foamed material is homogeneously dispersed in the porous fibrous material.

3. The filter element according to claim 1 or claim 2, wherein the filter element comprises a filter element wrapper, wherein the filter element wrapper is configured to at least partially, preferably fully circumscribe the filtration material.

4. The filter element according to any of the preceding claims, wherein the filter element comprises a tipping paper, wherein the tipping paper is configured to at least partially, preferably fully circumscribe the filtration material, preferably wherein the tipping paper is configured to at least partially circumscribe the filter element wrapper according to claim 3.

5. The filter element according to any of the preceding claims, wherein the porous fibrous material comprises a plurality of fibers, wherein a longitudinal axis of the fibers is arranged substantially parallel to a longitudinal axis of the filtration material, preferably wherein the fibers are regenerated cellulose fibers.

6. The filter element according to claim 5, wherein the porous fibrous material is a regenerated cellulose material preferably comprising the regenerated cellulose fibers.

7. The filter element according to any of the preceding claims, wherein the filter element has a solid cylindrical shape, preferably wherein the filter element has a rod shape.

8. The filter element according to any of the preceding claims, wherein the filtration material comprises a plurality of fragments of the porous foamed material dispersed in the porous fibrous material.

9. The filter element according to claim 8, wherein the fragment of porous foamed material has a volume of between 0.1 mm³ and 0.5 mm³, preferably of between 0.15 mm³ and 0.35 mm³.

10. The filter element according to any of the preceding claims, wherein a porosity of the filtration material is of between 0.3 and 0.8, preferably of 0.4 and 0.7, and more preferably of between 0.5 and 0.6, wherein the porosity is the ratio of the pore volume of the filtration material and the overall volume of the filtration material.

11 . The filter element according to any of the preceding claims, wherein a porosity of the porous fibrous material is larger than a porosity of the porous foamed material, preferably wherein the ratio of the porosity of the porous foamed material to the porosity of the porous fibrous material is of between 1 :1.08 and 1 :1.31 , preferably of between 1 :1.12 and 1 :1.23.

12. The filter element according to any of the preceding claims, wherein the ratio of the volume of the porous fibrous material and the porous foamed material is of between 1 :0.15 and 1 :0.25.

13. The filter element according to any of the preceding claims, wherein the filter element has a length of between 5 millimeters and 21 millimeters, preferably of between 7 millimeters and 11 millimeters.

14. The filter element according to any of the preceding claims, wherein the filter element has a diameter of between 3 millimeters and 10 millimeters, preferably of between 4 millimeters and 9 millimeters.

15. An aerosol-generating article comprising the filter element according to any of claims 1 to 14 and an aerosol-forming substrate.