Filter elements for aerosol generators with different porosities

Abstract

The present invention relates to a filter element (10) comprising a filtration material. The filtration material comprises a foam (12). The foam is configured such that the porosity of the foam decreases radially within the filter element.

Description

[Technical Field]

[0001] This invention relates to a filter element for an aerosol generating article. This invention relates to an aerosol generating article. This invention relates to an aerosol generating system. This invention relates to a method for manufacturing a filter element. [Background technology]

[0002] It is known to provide an aerosol generator for producing inhalable vapor. Such a generator may heat the aerosol-forming substrate to a temperature at which one or more components of the aerosol-forming substrate volatilize without burning the aerosol-forming substrate. The aerosol-forming substrate may be provided as part of an aerosol-generating article. The aerosol-generating article may have a rod shape for insertion into a cavity (such as a heating chamber) of the aerosol generator. A heating element may be disposed in or around the heating chamber to heat the aerosol-forming substrate when the aerosol-generating article is inserted into the heating chamber of the aerosol generator. The article may include a filter element. The filter element may include a plastic material such as cellulose acetate tow.

[0003] It is desirable to provide filter elements that offer improved sustainability. It is desirable to provide filter elements with reduced environmental impact. It is desirable to provide filter elements with improved filtration characteristics. It is desirable to provide filter elements with improved filtration efficiency. It is desirable to provide filter elements with tunable filtration characteristics. It is desirable to provide filter elements that can be manufactured cost-effectively. It is desirable to provide filter elements with tunable airflow characteristics. It is desirable to provide filter elements with improved airflow characteristics. It is desirable to provide filter elements with improved airflow management. [Overview of the project]

[0004] According to one embodiment of the present invention, a filter element is provided which may include a filtration material. The filtration material may include a foam. The foam may be configured such that the porosity of the foam decreases radially in the filter element.

[0005] According to one embodiment of the present invention, a filter element is provided which includes a filtration material. The filtration material includes a foam. The foam is configured such that the porosity of the foam decreases radially within the filter element.

[0006] The filter element may offer improved sustainability. The filter element may have reduced environmental impact. The filter element may have improved filtration characteristics. The filter element may have improved filtration efficiency. The filter element may have tunable filtration characteristics. The filter element may be manufactured cost-effectively. The filter element may have tunable airflow characteristics. The filter element may have improved airflow characteristics. The filter element may replace conventional cellulose acetate tow filter elements. The filter element may have filtration performance equivalent to conventional cellulose acetate tow filter elements. The filter element may have improved airflow control.

[0007] The filter element may be for use with aerosol-generating articles.

[0008] The filter material does not need to contain cellulose acetate. The foam does not need to contain cellulose acetate.

[0009] The radial direction may refer to a direction substantially perpendicular to the major axis of the filter element.

[0010] The filter element foam may be obtained by compressing at least a portion of a foam. The filter element foam may be obtained by compressing at least a portion of a foam with a uniform porosity. The filter element foam may be obtained by compressing a rectangular foam with a uniform porosity into a cylindrical foam with a substantially circular cross-section. The filter element foam may be obtained by compressing at least a peripheral portion of a rectangular foam with a uniform porosity so that the foam is compressed into a cylindrical shape with a substantially circular cross-section. The filter element foam may be obtained by compressing at least a portion disposed around the periphery of a rectangular foam with a uniform porosity so that the foam is formed into a cylindrical shape with a substantially circular cross-section.

[0011] The foam may be configured such that its density increases radially with respect to the filter element.

[0012] The foam may be porous. The foam may be open-cell foam. The foam may be dry foam. The foam may be solid foam.

[0013] Dry foam may refer to a material formed from pockets in a solid that is filled with air or other gases. Dry foam may also refer to a material formed from a wet foam by drying the wet foam.

[0014] A wet foam may also refer to a material formed from pockets of air or other gases in a liquid.

[0015] Open-cell foam may refer to a material that has fluidly interconnected pockets of air or other gases within a solid.

[0016] The foam may be produced by preparing a wet foam from a dispersion and then removing the liquid dispersion medium. The dispersion may be a dispersion of cellulosic material in a liquid dispersion medium. The dispersion may be a dispersion of regenerated cellulose. The wet foam may be produced from the dispersion by stirring the dispersion or by introducing air bubbles into the dispersion by other means. The dispersion medium may be removed by evaporation, freeze-drying, or supercritical drying.

[0017] The foam may be biodegradable. The foam may be recyclable.

[0018] The filter material may have a cylindrical shape. The filter material may be a rod. The filter material may be configured as a solid cylindrical rod. The rod may have a substantially circular cross-section. The rod may have a distorted circular cross-section. The filter material may have a substantially circular cross-section. The filter element may have a distorted circular cross-section. The foam may have a cylindrical shape. The foam may be configured as a rod. The foam may be configured as a solid cylindrical rod. The rod may have a substantially circular cross-section. The rod may have a distorted circular cross-section. The foam may have a substantially circular cross-section. The foam may have a distorted circular cross-section. The foam in the filter element may be a partially compressed foam. The peripheral portion of the foam in the filter element may be compressed. The filter element may comprise a core made from the filter material. The filter element may comprise a core made from the foam. The core may have a solid cylindrical shape. The core may be a rod. The rod may have a substantially circular cross-section. The core may have a substantially circular cross-section. The core may have a distorted circular cross-section.

[0019] The filter element may have a proximal end. The filter element may have a distal end. The filtration material may be disposed between the proximal end and the distal end of the filter element. The proximal end and the distal end of the filter element may be fluidly connected via the filtration material. The proximal end and the distal end of the filter element may be fluidly connected via a core of the filtration material. The proximal end and the distal end of the filter element may be fluidly connected via a foam. The filtration material may extend between the proximal end and the distal end of the filter element. The foam may extend between the proximal end and the distal end of the filter element.

[0020] "Porrosion" may refer to the volume fraction of void space within a material or component. "Porrosion" may refer to the volume fraction of void space within a foam. For example, if 60% of the volume of a foam is not filled with solid material, the foam will have a porosity of 0.6. "Porrosion" may refer to the volume fraction of void space within a filter element.

[0021] The decrease in the porosity of the foam may vary between different radial directions. The gradient of the decrease in the porosity of the foam may vary between different radial directions. The difference between the porosity at the periphery of the foam and the porosity at the center of the foam may vary between different radial directions.

[0022] The airflow characteristics may depend on the porosity of the foam. The characteristics of aerosol flow may depend on the porosity of the foam. The flow velocity may increase with increasing porosity. The flow velocity through a region of foam with a higher porosity may increase compared to the flow velocity through a region of foam with a lower porosity. The relative flow velocity may be adjusted by varying the relative porosity of the foam along the radial direction of the foam in the filter element. Because the porosity of the foam decreases radially in the filter element, aerosols may travel slower through the peripheral region of the foam than through the central region of the foam. The foam may be configured so that the flow velocity through the foam decreases radially in the filter element. The flow velocity may also be the flow velocity parallel to the longitudinal axis of the filter element.

[0023] The characteristics of the interaction between the filter element foam and the aerosol flow or airflow may depend on the flow velocity. The characteristics of the interaction between a portion of the foam and the aerosol flow or airflow may depend on the flow velocity through that portion of the foam. The efficiency with which compounds are removed from the aerosol flow or airflow by the foam may depend on the flow velocity. For example, a first compound may be removed more efficiently at slower flow velocities, while a second compound may be removed more efficiently at faster flow velocities. By providing a foam with radially decreasing porosity, compounds may be removed more effectively from the aerosol. By providing a foam with radially decreasing porosity, a wider variety of compounds may be removed from the flow with improved efficiency.

[0024] The filtration performance of the filtration material within the filter element may be tuned by varying one or more of the porosity difference at the periphery and the center of the foam, the gradient of decrease in the porosity of the foam in the radial direction of the filter element, the foam material, the foam structure, and the compressive force acting on the foam. The filtration profile of the filtration material within the filter element may be tuned by varying one or more of the porosity difference at the periphery and the center of the foam, the gradient of decrease in the porosity of the foam in the radial direction of the filter element, the foam material, the foam structure, and the compressive force acting on the foam. Compression of at least a portion of the foam may result in a decrease in the porosity of that portion of the foam. Compression of at least a portion of the foam may result in an increase in the density of that portion of the foam.

[0025] The filtration material may consist of a foam.

[0026] The porosity at the center of the foam may be higher than the porosity at the periphery of the foam.

[0027] "The center of the foam" may refer to the region of the foam disposed on the central longitudinal axis of the filter element. "The center of the foam" may refer to the central longitudinal axis of the foam. "The center of the foam" may refer to the center of the cross-section of the foam. The porosity of the foam at the center of the foam may refer to the porosity at the central longitudinal axis of the filter element. The center of the foam may correspond to the center of the filter element.

[0028] "The periphery of the foam" may refer to the region of the foam disposed on the outer surface of the foam. "The periphery of the foam" may refer to the region of the foam disposed at the boundary of the foam. The porosity of the foam at the periphery of the foam may refer to the porosity at the outer surface of the foam. The porosity of the foam at the periphery of the foam may refer to the porosity at the boundary of the foam.

[0029] The porosity of the foam may be constant along the longitudinal axis of the filter element. The density of the foam may be constant along the longitudinal axis of the filter element.

[0030] The density at the center of the foam may be higher than the density at the periphery of the foam.

[0031] The periphery of the foam may be compressed. The foam may be compressed at its periphery. The center of the foam does not need to be compressed. Differences in porosity between the center and periphery of the foam may result from the compression of the periphery. The foam may be compressed along the radial direction of the filter element.

[0032] The ratio of the porosity at the periphery of the foam to the porosity at the center of the foam may be 1:1.3 to 1:2.67, preferably 1:1.5 to 1:2.1, and more preferably about 1:1.75.

[0033] The porosity around the foam may be 0.3 to 0.5. The porosity in the center of the foam may be 0.6 to 0.8.

[0034] The foam may be a foam made from a cellulose-based material. The foam may be a foam made from a regenerated cellulose material. The foam may be a foam made from regenerated cellulose.

[0035] The foam may be a foamed cellulose-based material. The cellulose-based material may be regenerated cellulose.

[0036] The foam may be a cellulose-based foam. The foam may be a regenerated cellulose foam. The regenerated cellulose material does not have to contain cellulose acetate. The foam may contain regenerated cellulose material. The foam may be made from regenerated cellulose material. The regenerated cellulose material may contain regenerated cellulose fibers. The foam may be equipped with regenerated cellulose fibers. The foam may be made from regenerated cellulose fibers. The foam may be made from foamed regenerated cellulose. The foam may be made from nonwoven regenerated cellulose fibers.

[0037] Regenerated cellulose fibers may be obtained by dissolving pure cellulose from one or both wood pulp and plant fibers. Regenerated cellulose fibers may also be obtained by dissolving derivative cellulose from one or both wood pulp and plant fibers.

[0038] The foam may be a tow of regenerated cellulose material. The foam may be a tow of regenerated cellulose fibers. The foam may comprise bundles of regenerated cellulose fibers.

[0039] The foam material is 15 kg / m³ 3 ~45kg / m 3 Preferably 20 kg / m 3 ~40kg / m 3 It may have a density of . The density of the foam may be determined according to ISO 845.

[0040] The foam may have a paper mass content of 70% to 95% by weight, preferably 75% to 90% by weight.

[0041] The foam may contain a biopolymer in an amount of 10% to 25% by weight, preferably 15% to 20% by weight. The biopolymer may contain polyhydroxyalkanoate (PHA). The polyhydroxyalkanoate may be polyhydroxybutyric acid. The foam may contain polyhydroxyalkanoate in an amount of 10% to 25% by weight, preferably 15% to 20% by weight. The foam may contain polyhydroxybutyric acid in an amount of 10% to 25% by weight, preferably 15% to 20% by weight.

[0042] The foam may contain biodegradable thermoplastics. The foam may be made from biodegradable thermoplastics. Polyhydroxybutyric acid (PHB) may be produced from sugars or from carbon dioxide using cyanobacteria.

[0043] The indentation deflection (IFD) test value of the foam may be determined according to ASTM D 3574. Characterization according to ASTM D 3574 may be performed using a 65% feed. The indentation deflection (IFD) test value of the foam may be 380 to 570 Newtons, preferably 410 to 500 Newtons. The hardness of the foam may be determined according to ISO 2439 Method B. The hardness may be 75 to 105 Newtons, preferably 80 to 100 Newtons. The compression set value of the foam may be determined according to ISO 1856 Method C1. The compression set value of the foam may be determined after 2.5 hours. The compression set value of the foam sheet may be 20 to 40 percent, preferably 25 to 35 percent. The thermal conductivity of the foam may be determined according to ISO 8302. The thermal conductivity of the foam may be 0.025 W / mK to 0.05 W / mK, preferably 0.03 W / mK to 0.04 W / mK. The above tests may be performed using sheets of foam material.

[0044] The foam may be based on one or more of the following: wood pulp, bamboo pulp, pulp obtained from tobacco stalks, and hybrid foams of nanocellulose and kaolin microfiberized cellulose composite materials.

[0045] The foam may be a biocomposite foam. The foam may be a nanocellulose-based foam. The foam may be a hybrid foam. The foam may be a hybrid foam of nanocellulose and kaolin microfiberized cellulose composite material. The foam may be a polyhydroxyalkanoate-based foam. The foam may be a polyhydroxybutyric acid-based foam. The foam may be a dry foam. The foam may be a solid foam.

[0046] The foam may be viscose foam. The foam may be made from viscose fibers. The filter material does not have to contain cellulose acetate.

[0047] The foam does not need to contain cellulose acetate. The filter element does not need to contain cellulose acetate.

[0048] The filter element may include a filter element wrapper. The filter element wrapper may be configured to at least partially surround the filter material. The filter element wrapper may be configured to completely surround the filter material.

[0049] The filter element wrapper may at least partially surround the foam. The filter element wrapper may completely surround the foam. The filter element wrapper may surround the foam. The filter element wrapper may be wrapped around the filtration material. The filter element wrapper may be wrapped around the foam. The filter element wrapper may be wrapped around the core of the foam. The filter element wrapper may have substantially the same length as the foam within the filter element. The filter element wrapper may be configured to at least partially enclose the filtration material. The filter element wrapper may be configured to completely enclose the filtration material.

[0050] The filter element may consist of a filter element wrapper and a foam. The filter element may also consist of a filter material wrapped around the filter element wrapper.

[0051] The filter element wrapper may be configured to stabilize the filtration material. The filter element wrapper may be configured to protect the filtration material. The filter element wrapper may be configured to stabilize the foam. The filter element wrapper may be configured to stabilize the shape of the foam. The filter element wrapper may be configured to stabilize the compression of the foam. The filter element wrapper may be configured to hold the foam in a desired arrangement. The filter element wrapper may be configured to stabilize the arrangement of the foam. The filter element wrapper may be configured to compress the foam.

[0052] The filtration material may be arranged around the longitudinal axis of the filter element. The filter element wrapper may be arranged coaxially around the filtration material.

[0053] The filter element wrapper may be permanently attached to the filter material. The filter element wrapper may be glued to the filter material with starch paste.

[0054] The filter element wrapper may have a transparency of 3500 cholesta units to 12000 cholesta units.

[0055] The filter element wrapper may have a thickness of 0.2 micrometers to 0.4 micrometers.

[0056] The filter element wrapper may be made from paper material.

[0057] The filter element wrapper may be biodegradable. The filter element wrapper may be recyclable.

[0058] The filter element wrapper may have a basis weight of 10 g / m to 30 g / m, preferably 17 g / m to 21 g / m.

[0059] The filter element wrapper is 78g / m². 2It may also be paper. The filter element wrapper should be 100g / m². 2 It can also be made of paper.

[0060] The filter element may include a chipping paper. The chipping paper may be configured to at least partially surround the filter element wrapper. The chipping paper may be configured to completely surround the filter element wrapper.

[0061] The chipping paper may be configured to at least partially surround the filter material. The chipping paper may be configured to completely surround the filter material. The chipping paper may be configured to at least partially surround the foam. The chipping paper may be configured to completely surround the foam.

[0062] The chipping paper may be wrapped around the filter material. The chipping paper may be wrapped around the foam. The chipping paper may be arranged coaxially around the filter element wrapper.

[0063] Chipping paper may have a textured surface. Chipping paper may have a textured outer surface. Chipping paper may have an embossed surface. Chipping paper may have an embossed outer surface. Chipping paper may have a smooth surface. Chipping paper may have a smooth outer surface.

[0064] The chipping paper may have a permeability of 380 cholesta units to 550 cholesta units.

[0065] The chipping paper may have a thickness of 0.5 micrometers to 1.1 micrometers.

[0066] The chipping paper may have a basis weight of 25 g / m to 60 g / m, preferably 30 g / m to 50 g / m.

[0067] The filter element wrapper may be configured to compress at least the peripheral portion of the foam, for example, to facilitate the shape of the foam.

[0068] The filter element wrapper may be configured to compress at least the peripheral portion of the foam so that the foam conforms to a cylindrical shape.

[0069] The filter element may be shaped like a cylinder. The filter element may be a rod. The filter element may be a rod having a substantially circular cross-section. The filter element may have a cylindrical shape. The filter element may have a solid cylindrical shape. The filter element may have a substantially circular cross-section. The filter element may have a distorted circular cross-section.

[0070] The filter element wrapper may be configured to compress the foam into a cylindrical rod with a substantially circular cross-section. The filter element foam may originate from a cuboidal foam of uniform density. The filter element wrapper may be configured to compress the foam into a cylindrical rod with a distorted circular cross-section.

[0071] The filter element wrapper may be configured to compress a rectangular foam into a cylindrical rod. The filter element wrapper may also be configured to compress a rectangular foam into a rod having a substantially circular cross-section.

[0072] The foam may have a high porosity region. The foam may have a low porosity region. The high porosity region may be located at the center of the foam. The low porosity region may be located around the periphery of the foam. The low porosity region may have four substantially spindle-shaped round protrusions. The high porosity region may be substantially star-shaped. The high porosity region may be substantially rhombic. The high porosity region may be located around the central longitudinal axis of the filter element. The low porosity region may be located coaxially around the high porosity region. The low porosity region may be a region of foam compressed by the filter element wrapper. The low porosity region may comprise a portion of foam compressed by the filter element wrapper. The low porosity region may consist of a portion of foam compressed by the filter element wrapper. The high porosity region may be in contact with the low porosity region. The high porosity region may comprise a portion of foam not compressed by the filter element wrapper. The high porosity region may consist of portions of the foam that are not compressed by the filter element wrapper. The porosity of the low porosity region may vary across the low porosity region. Variations in the porosity of the low porosity region may result from different portions of the low porosity region being compressed to different degrees.

[0073] The porosity in the low porosity region may be between 0.3 and 0.6. The porosity in the high porosity region may be greater than 0.6 and less than or equal to 0.8.

[0074] The foam may be configured such that its porosity changes around its periphery. Preferably, the porosity changes in a regular manner around its periphery.

[0075] The filter element wrapper may be configured to compress a cuboidal foam with a uniform porosity and square cross-section into a substantially circular cross-section cylindrical rod, thereby reducing the porosity of the foam in the radial direction of the filter element.

[0076] The cross-section of the rectangular foam may extend within a plane that extends perpendicular to the central long axis of the rectangular foam.

[0077] The ratio of the side lengths of the square cross-section of the rectangular foam to the outer diameter of the substantially circular cross-section cylindrical rod may be 1 to 1.5, preferably 1 to 1.3, and more preferably about 1.

[0078] The length of the sides of the square cross-section of the rectangular foam may be 7 to 11 millimeters, preferably 8 to 10 millimeters.

[0079] The foam may be configured such that its porosity changes around its periphery. Preferably, the porosity changes in a regular manner around the periphery of the foam. Preferably, the periphery is the outer circumference of the foam.

[0080] The periphery may comprise multiple points with maximum porosity. These points may be equidistant along the periphery. The periphery may comprise multiple points with minimum porosity. These points may be equidistant along the periphery. Preferably, the porosity of the points with maximum porosity is the same. Preferably, the porosity of the points with minimum porosity is the same.

[0081] The surrounding area may have four points of maximum porosity. The surrounding area may have four points of minimum porosity. The foam of the filter element may be derived from a rectangular foam with a square cross-section by compressing a rectangular foam radially inward. The rectangular foam may have a uniform density.

[0082] The periphery of the foam may include three points of maximum porosity. The periphery of the foam may also include three points of minimum porosity. The foam of the filter element may be derived from a rod-shaped foam with a triangular cross-section by compressing a rectangular foam radially inward. The rod-shaped foam may have a uniform density.

[0083] The filter element may consist of a filter element wrapper and foam. The filter element may consist of a filter element wrapper, foam, and chipping paper.

[0084] The foam may be configured so that its porosity gradually decreases in the radial direction of the filter element. The foam may be configured so that its porosity continuously decreases in the radial direction of the filter element. The foam may be configured so that its porosity smoothly decreases in the radial direction of the filter element.

[0085] The filter element may have a length of 5 mm to 21 mm, preferably 7 mm to 11 mm.

[0086] The filter element may have an outer diameter of 3 mm to 10 mm, preferably 4 mm to 9 mm. The filter element may have a diameter of about 8 mm. The filter element may have a diameter of about 10 mm.

[0087] The filter element wrapper may be configured to compress the foam into a cylindrical rod with a substantially circular cross-section. The filter element foam may originate from a cuboidal foam of uniform density. The filtration material foam may be a cuboidal foam of uniform density that has been compressed into a cylindrical rod with a substantially circular cross-section. The cuboidal foam of uniform density may be compressed into a cylindrical rod with a substantially circular cross-section by the filter element wrapper. The cross-section of the cuboidal foam may be square. The square may have sides with a length of 7 to 11 millimeters, preferably 8 to 10 millimeters.

[0088] In one embodiment of the present invention, the filter element may comprise a regenerated cellulose foam and a filter element wrapper. In the filter element, the filter element wrapper may be tightened around the foam to compress at least the peripheral portion of the foam. Compression of the foam may result in a foam having a porosity that decreases radially in the filter element. Preferably, the filter element foam may be obtained by compressing a rectangular foam having a uniform porosity into a cylindrical foam having a substantially circular cross-section and a porosity that decreases radially in the filter element. The foam may be compressed to the maximum extent along the edge of the rectangular foam obtained therefrom, with the filter element foam extending parallel to the longitudinal axis of the filter element.

[0089] The foam may contain a softening agent. The foam has a viscosity of 0.8 daN / cm³. 2 It may have a tear resistance exceeding [a certain value]. The absorption of the foam may be about 20 times its dry weight. The foam may contain one or more pigments. The foam does not need to contain a binder.

[0090] Viscose foam may be manufactured in several steps. In the first step, a cellulosic material may be provided. In the second step, the cellulosic material may be pulverized. In the third step, the cellulosic material may be chemically transferred to a viscose lump mixture. In the fourth step, one or more of fibers, salts, and pigments may be added to the mixture. In the fifth step, the viscose may be solidified and curdled using heat. In the sixth step, the cellulosic material may be recycled. In the seventh step, sodium sulfate crystals may be dissolved. In the eighth step, the resulting material may be centrifuged and dried to obtain viscose foam.

[0091] The regenerated cellulose fibers may be dispersed in a liquid medium. The regenerated cellulose fibers may be extruded. The regenerated cellulose fibers may be solidified to form a rectangular foam.

[0092] The foam may be a foamed cellulose material. The foam may be a foam of a cellulose material. The foam may be manufactured according to a method for manufacturing a sheet of a foamed cellulose material as described in European Patent Application No. 23206185.3, which is incorporated herein by reference. The foam may be a filter material used in an aerosol generating article disclosed in European Patent Application No. 23206185.3, which is incorporated herein by reference. The foam may be a foamed cellulose material used in an aerosol generating article disclosed in European Patent Application No. 23206185.3, which is incorporated herein by reference. A sheet of foamed cellulose material is manufactured by the following steps: a) A step of preparing a suspension of a cellulosic material, wherein the suspension contains a foaming agent; b) A step of stirring a suspension of cellulosic material and optionally adding a hydrophobic agent to the suspension of cellulosic material to obtain a wet foam of the cellulosic material, c) A step of preparing a wet foam sheet of a cellulose-based material, and then dewatering the wet foam sheet of the cellulose material, d) A step of drying a wet foam sheet of cellulose-based material, e) A step of re-wetting the foam sheet, f) A process for adjusting the thickness of the foam sheet, g) The foam may be manufactured using a method that includes a step of drying the foam.

[0093] The method may result in a sheet of dried foamed cellulose-based material.

[0094] A suspension of cellulosic material may be a suspension of pulp. A suspension of cellulosic material may be a suspension of wood pulp. A suspension of cellulosic material may be a suspension of cellulose. A suspension of cellulosic material may be a suspension of purified cellulose. A suspension of cellulosic material may be a suspension of cellulosic fibers. A suspension of cellulosic material may be a suspension of cellulose fibers.

[0095] Cellulose-based materials may be cellulose. Cellulose-based materials may be cellulose fibers. Cellulose-based materials may contain cellulose. Cellulose-based materials may contain cellulose fibers. Cellulose-based materials may contain cellulose fibers. Cellulose-based materials do not have to contain cellulose acetate.

[0096] Cellulosic materials may be based on bleached softwood pulp, unbleached softwood pulp, bleached eucalyptus pulp, and bleached cotton linter pulp, or any combination thereof.

[0097] The foaming agent may contain one or more surfactants. Preferably, the foaming agent may be a mixture containing about 80 mol% sodium dodecyl sulfate (SDS) and about 20 mol% polyoxyethylene (20) sorbitan monolaurate.

[0098] Preferably, the hydrophobic agent may be an alkylketene dimer (AKD). The hydrophobic agent may be added to the suspension of the cellulosic material in an amount of about 1% by weight of the suspension.

[0099] In step a), the cellulosic material may be purified to 2 percent to 3 percent. In step a), the conductivity of the suspension of the cellulosic material may be adjusted to 1000 μS / cm by adding sodium chloride. In step a), the pH of the suspension of the cellulosic material may be adjusted to about 8 by adding sodium hydroxide. In step a), a strengthening additive may be added to the suspension of the cellulosic material. The strengthening additive may be selected from one or more of carboxymethylcellulose sodium (CMC), microfiberized cellulose, and cellulose nanofibrils.

[0100] In step c), the wet foam of the cellulose material may be poured onto a hand sheet mold. In step c), the sheet of wet foam of the cellulose material may be discharged by gravity. In step c), dewatering may not be carried out using a vacuum. In step c), a fabric may be placed on top of the foam to stabilize it. In step d), drying may be carried out in an oven at 70 degrees Celsius.

[0101] In step e), the foam may be re-moistened to a 50 percent moisture content. In step e), the foam sheet may be re-moistened by exposing the sheet to an atmosphere having a 50% moisture content for 4 hours.

[0102] In step g), the foam may be dried in an oven at 70 degrees Celsius. In step g), the foam may be cured at approximately 80 degrees Celsius for 2 hours to ensure a complete reaction of AKD.

[0103] The foamed cellulose material may be a foam of a cellulose material. The foamed cellulose material may be a dry foam of a cellulose material. The foamed cellulose material may be a solid foam of a cellulose material. The foamed cellulose material may be an open-cell foam. The foamed cellulose material does not have to contain cellulose acetate. The foamed cellulose material may be porous. The density of the cellulose material foam is 45 kg / m³3 ~105kg / m 3 may be.

[0104] The present invention further relates to an aerosol-generating article comprising a filter element and an aerosol-forming substrate as described herein.

[0105] The filter element may be disposed downstream of the aerosol-forming substrate. The filter element may be disposed upstream of the aerosol-forming substrate. The filter element may be a front plug. The filter element may be a mouth plug. The filter element may be disposed at the distal end of the article. The filter element may be disposed at the proximal end of the article.

[0106] The present invention further relates to an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device as described herein.

[0107] The present invention further relates to a method for manufacturing a filter element for an aerosol-generating article. The method comprises the following steps: a) providing a foam of substantially uniform porosity, b) compressing at least a portion of the foam by winding a filter element wrapper around the foam such that the porosity of the foam decreases in the radial direction of the filter element.

[0108] The present invention further relates to a method for manufacturing a filter element for an aerosol-generating article. The method comprises the following steps: a) providing a foam of substantially uniform porosity, b) compressing at least a portion of the foam by winding a filter element wrapper around the foam such that the porosity of the foam decreases in the radial direction of the filter element.

[0109] The foam in step a) may have a rectangular parallelepiped shape. In step b), the rectangular parallelepiped foam may be compressed into a rod by tightening a filter element wrapper around the rectangular parallelepiped foam. The rectangular parallelepiped foam may have a rectangular cross-section. The rectangular parallelepiped foam may have a square cross-section. The cross-section may be a square with a rim about 8 millimeters long. The cross-section may be a square with a rim about 10 millimeters long.

[0110] The foam may be a foam made from regenerated cellulose. The rod may have a substantially circular cross-section. The filter material may consist of a foam.

[0111] The foam in step a) may have a uniform porosity.

[0112] The foam in step a) may be rectangular in shape, or it may have a square cross-section.

[0113] In step b), the rectangular foam with a square cross-section may be compressed into a substantially circular rod such that the ratio of the side length of the square cross-section of the rectangular foam in step a) to the outer diameter of the circular rod is 1 to 1.5, preferably 1 to 1.3, and more preferably about 1.

[0114] The length of the sides of the square cross-section of the rectangular foam in step a) may be 7 mm to 11 mm, preferably 8 mm to 10 mm.

[0115] In step b), the foam from step a) may be compressed such that the porosity changes around the periphery of the foam. Preferably, the porosity changes in a regular manner around the periphery of the foam. Preferably, the periphery is the outer circumference of the foam.

[0116] The periphery may comprise multiple points with maximum porosity. These points may be equidistant along the periphery. The periphery may comprise multiple points with minimum porosity. These points may be equidistant along the periphery. Preferably, the porosity of the points with maximum porosity is the same. Preferably, the porosity of the points with minimum porosity is the same.

[0117] The surrounding area may have four points of maximum porosity. The surrounding area may also have four points of minimum porosity.

[0118] After step b), the rolled foam may be cut to the desired length of the filter element.

[0119] The present invention further relates to a filter element for an aerosol-generating article manufactured by a method for manufacturing a filter element for an aerosol-generating article as described herein.

[0120] As used herein, the terms “proximal,” “distal,” “downstream,” and “upstream” may be used to describe the relative position of a component or part of a component of an aerosol generator with respect to the direction in which the user inhales the aerosol generator during use.

[0121] As used herein, the terms “proximal,” “distal,” “downstream,” and “upstream” may be used to describe the relative position of a component or part of a component of an aerosol-generating article with respect to the direction in which the user inhales the aerosol-generating article during its use.

[0122] The aerosol generator may have an oral end through which, during use, aerosol exits the aerosol generator and is delivered to the user. The oral end may also be called the proximal end. During use, the user may inhale the proximal or oral end of the aerosol generator to inhale the aerosol generated by the aerosol generator. The oral end may be provided with a mouthpiece. Alternatively, the user may directly inhale an aerosol generating article inserted into an opening at the proximal end of the aerosol generator. The opening at the proximal end may be a cavity opening. The cavity may be configured to receive an aerosol generating article. The aerosol generator may have a distal end opposite to the proximal or oral end. The proximal or oral end of the aerosol generator may also be called the downstream end, and the distal end of the aerosol generator may also be called the upstream end.

[0123] The aerosol-generating article may have a mouth end through which, during use, the aerosol exits the article and is delivered to the user. The mouth end may also be called the proximal end. Filter elements, as described herein, may be located at the mouth end of the article. The aerosol-generating article may have a distal end opposite to the proximal end or mouth end. The proximal end or mouth end of the aerosol-generating article may also be called the downstream end, and the distal end of the aerosol-generating article may also be called the upstream end. Filter elements, as described herein, may be located proximal to the aerosol-forming substrate.

[0124] The long axis of a component may extend between its proximal end and its distal end. The long axis of a filter element may extend between its proximal end and its distal end. The long axis of an aerosol generating article may extend between its proximal end and its distal end. The long axis of an aerosol generating device may extend between its distal end and its proximal end.

[0125] As used herein, “aerosol generator” may also refer to a device that generates an aerosol by interacting with an aerosol-forming substrate. The aerosol-generating article may include a mouthpiece. The aerosol-forming substrate may be part of the aerosol-generating article. The aerosol generator may also be a smoking device that generates an aerosol that can be directly inhaled into the user's lungs through the user's mouth by interacting with the aerosol-forming substrate of the aerosol-generating article. The aerosol generator may also be a holder. The device may also be an electrically heated smoking device. The aerosol generator may include a housing, an electrical circuit, a power supply, a heating chamber, and a heating element.

[0126] The aerosol generator may include an electrical circuit. The electrical circuit may include a microprocessor, which may be a programmable microprocessor. The microprocessor may be part of a controller. The electrical circuit may include further electronic components. The electrical circuit may be configured to regulate the supply of power to a heating element. Power may be supplied to the heating element continuously following the startup of the aerosol generator, or intermittently, such as with each smoke extraction. Power may be supplied to the heating element in the form of current pulses. The electrical circuit may be configured to monitor the electrical resistance of the heating element and, preferably, control the supply of power to the heating element in accordance with the electrical resistance of the heating element.

[0127] An aerosol generator may have a power source, typically a battery, within the main body of the aerosol generator. In one embodiment, the power source is a lithium-ion battery. Alternatively, the power source may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery (e.g., a lithium-cobalt battery, lithium iron phosphate, lithium titanate, or lithium polymer battery). Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may have a capacity that allows for the storage of sufficient energy for one or more use experiences. For example, the power source may have sufficient capacity to continuously generate aerosols for a period of approximately 6 minutes, or a period of multiples of 6 minutes. In another embodiment, the power source may have sufficient capacity to provide a predetermined number of fume extractions or discontinuous activation of the heating element.

[0128] The cavity of the aerosol generator may have an open end into which an aerosol generating article is inserted. The open end may be the 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 providing an air opening located within 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 located upstream of the cavity. The open end may be located downstream of the cavity. The cavity may have an elongated extension. The cavity may have a longitudinal axis. The longitudinal axis may be a direction extending between the open end and the closed end along the longitudinal axis. The longitudinal axis of the cavity may be parallel to the longitudinal axis of the aerosol generator.

[0129] 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 received inside the cavity. The cavity may have a circular cross-section. The cavity may have an elliptical or rectangular cross-section. The cavity may have an inner diameter corresponding to the outer diameter of the aerosol-generating article.

[0130] The airflow channel may extend through the cavity. Ambient air may be drawn through the airflow channel into the aerosol generator, into the cavity, and toward the user. Downstream of the cavity, a mouthpiece may be provided, or the user may inhale the aerosol generating article directly. The airflow channel may extend through the mouthpiece.

[0131] In any aspect of this disclosure, the heating element may include an electrical resistive material. Suitable electrical resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilide), carbon, graphite, metals, alloys, and composite materials made of ceramic and metallic materials. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold, and silver. Examples of suitable metallic alloys include stainless steel, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, gold-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal®, and iron-manganese-aluminum alloys. In composite materials, the electrical resistive material may be embedded in, sealed in, or coated with an insulating material, depending on the required energy transfer dynamics and external physicochemical properties, or vice versa.

[0132] As described, in any aspect of the present disclosure, the heating element may be part of an aerosol generator. The aerosol generator may comprise an internal heating element, an external heating element, or both an internal and an external heating element, where "internal" and "external" refer to the aerosol-forming substrate. The internal heating element may take any suitable form. For example, the 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 conductive or electrically resistive metal tubes. Alternatively, the internal heating element may be one or more heating needles or rods passing through the center of the aerosol-forming substrate. Other alternatives include heating wires or filaments, such as Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wires or heating plates. Optionally, the internal heating element may be placed in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a clear relationship between temperature and resistivity. In such exemplary devices, the metal may be formed as a track on a suitable insulating material such as ceramic, and then sandwiched between other insulating materials such as glass. The heater thus formed may be used for both heating the heating element in operation and monitoring its temperature.

[0133] The external heating element may take any suitable form. For example, the 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 fit around the periphery of the substrate receiving cavity. Alternatively, the external heating element may take the form of a metal grid, a flexible printed circuit board, a molded circuit component (MID), a ceramic heater, a flexible carbon fiber heater, or may be formed on a substrate of suitable shape using a coating technique such as plasma deposition. The external heating element may also be formed using a metal having a clear relationship between temperature and resistivity. In such exemplary devices, the metal may be formed as a track between two layers of suitable insulating material. The external heating element thus formed may be used both for heating the external heating element and for monitoring its temperature during operation.

[0134] As an alternative to electrically resistive heating elements, heating elements may be configured as inductive heating elements. Inductive heating elements may comprise an induction coil and a susceptor. Generally, a susceptor is a material that has the ability to generate heat when penetrated by an alternating magnetic field. When located within an alternating magnetic field, if the susceptor is conductive, typically, eddy currents are induced by the alternating magnetic field. If the susceptor is magnetic, typically, another effect that contributes to heating is generally called hysteresis loss. Hysteresis loss arises primarily from the movement of magnetic domain blocks within the susceptor, because their magnetic orientations align with the alternating induced magnetic fields. Another effect that contributes to hysteresis loss is when magnetic domains expand or contract within the susceptor. Generally, all these changes occurring at or below the nanoscale within the susceptor are called "hysteresis loss" because they generate heat within the susceptor. Therefore, if the susceptor is both magnetic and conductive, both hysteresis loss and eddy current generation will contribute to the heating of the susceptor. If the susceptor is magnetic but not conductive, hysteresis loss will be the only means by which the susceptor will be heated when penetrated by an alternating magnetic field. According to the present invention, the susceptor may be conductive or magnetic, or both conductive and magnetic. An alternating magnetic field generated by one or more induction coils heats the susceptor, which then transfers heat to the aerosol-forming substrate, thereby forming an aerosol. Heat transfer may be mainly by conduction. Such heat transfer is best when the susceptor is in close thermal contact with the aerosol-forming substrate.

[0135] As used herein, the term “aerosol-generating article” may refer to an article comprising an aerosol-forming substrate having the ability to release volatile compounds capable of forming aerosols. For example, an aerosol-generating article may be a smoking article that generates an aerosol that can be directly inhaled into the user's lungs through the user’s mouth. An aerosol-generating article may be disposable.

[0136] The aerosol generating article may be a flammable cigarette. The aerosol generating article may comprise a cigarette rod and a filter element as described herein. The cigarette may be combusted. The user may light the cigarette and cause it to burn.

[0137] As used herein, the term “aerosol-forming substrate” may also refer to a substrate having the ability to release one or more volatile compounds that can form aerosols. Such volatile compounds may be released by heating the aerosol-forming substrate. Conveniently, the aerosol-forming substrate may be part of an aerosol-generating article or a smoking article. In a combustible cigarette, the substrate may be burned. The substrate may contain tobacco.

[0138] The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate may contain both solid and liquid components. The aerosol-forming substrate may contain a tobacco-containing material that contains volatile tobacco-flavored compounds released from the substrate upon heating. The aerosol-forming substrate may contain non-tobacco materials. The aerosol-forming substrate may contain an aerosol-forming agent that facilitates the formation of a high-density and stable aerosol. Examples of suitable aerosol-forming agents include glycerin and propylene glycol.

[0139] The aerosol generating substrate may include homogenized tobacco material, an aerosol forming agent, and water. Providing homogenized tobacco material may improve aerosol generation and the nicotine content and flavor profile of the aerosol generated during heating of the aerosol generating article. Specifically, the process of producing homogenized tobacco involves a process of crushing tobacco leaves, which allows for more effective release of nicotine and flavor during heating.

[0140] A non-exclusive list of non-limiting embodiments is provided below. One or more features of these embodiments may be combined with one or more features of any of the features described above, for example, one or more features of other embodiments, forms, or aspects described herein. [Examples]

[0141] Example 1: A filter element for an aerosol generator, wherein the filter element comprises a filter material, the filter material includes a foam, and the foam is configured such that the porosity of the foam decreases in the radial direction of the filter element.

[0142] Example 1A: A filter element for an aerosol generating article, wherein the filter element comprises a filter material, the filter material includes a foam, and the foam is configured such that the porosity of the foam decreases in the radial direction of the filter element.

[0143] Example 2: A filter element according to Example 1 or Example 1A, wherein the filtration material consists of foam.

[0144] Example 3: A filter element according to any of Example 1, Example 1A, and Example 2, wherein the porosity at the center of the foam is higher than the porosity at the periphery of the foam.

[0145] Example 4: A filter element according to Example 3, wherein the ratio of the porosity at the periphery of the foam to the porosity at the center of the foam is 1:1.3 to 1:2.67, preferably 1:1.5 to 1:2.1, and more preferably about 1:1.75.

[0146] Example 5: A filter element according to Example 3 or Example 4, wherein the porosity around the foam is 0.3 to 0.5 and the porosity in the center of the foam is 0.6 to 0.8.

[0147] Example 6: A filter element according to any of the preceding examples, wherein the foam is a foam made of a cellulose-based material, preferably a foam made of a regenerated cellulose material.

[0148] Example 7: A filter element according to Example 6, wherein the foam is viscose foam.

[0149] Example 8: A filter element according to any of the preceding examples, wherein the filter material does not contain cellulose acetate.

[0150] Example 9: A filter element according to any of the preceding embodiments, wherein the filter element comprises a filter element wrapper, the filter element wrapper is configured to at least partially, preferably completely, surround a filtration material.

[0151] Example 10: A filter element according to Example 9, wherein the filter element wrapper is made from paper material.

[0152] Example 11: A filter element according to Example 9 or Example 10, wherein the filter element wrapper is configured to compress at least the peripheral portion of the foam, such as by facilitating the shape of the foam.

[0153] Example 12: A filter element according to any of the preceding examples, wherein the filter element is formed in a cylindrical shape, preferably the filter element is a rod.

[0154] Example 13: A filter element according to any of Examples 9 to 12, wherein the filter element wrapper is configured to compress the foam into a cylindrical rod with a substantially circular cross-section, and preferably the foam of the filter element is derived from a cuboidal foam of uniform density.

[0155] Example 14: A filter element according to any of Examples 9 to 13, wherein the filter element consists of a filter element wrapper and a foam.

[0156] Example 15: A filter element according to any of the preceding examples, wherein the foam is configured such that the porosity of the foam gradually decreases in the radial direction of the filter element.

[0157] Example 16: A filter element according to any of Examples 9-15, wherein the filter element wrapper is configured to compress a cuboidal foam with uniform porosity and a square cross-section into a substantially circular cross-section cylindrical rod, such that the porosity of the foam decreases radially in the filter element.

[0158] Example 17: A filter element according to Example 16, wherein the ratio of the side length of the square cross-section of the rectangular foam to the outer diameter of the cylindrical rod with a substantially circular cross-section is 1 to 1.5, preferably 1 to 1.3, and more preferably about 1.

[0159] Example 18: A filter element according to Example 17, wherein the side length of the square cross-section of the rectangular foam is 7 mm to 11 mm, preferably 8 mm to 10 mm.

[0160] Example 19: A filter element according to any of the preceding examples, wherein the foam is configured such that the porosity changes around the periphery of the foam, preferably in a regular manner, and preferably the periphery is the outer circumference of the foam.

[0161] Example 20: A filter element according to Example 19, wherein the periphery comprises a plurality of points with maximum porosity, the points with maximum porosity being equidistant along the periphery, and the periphery comprises a plurality of points with minimum porosity, the points with minimum porosity being equidistant along the periphery, preferably the porosity of the points with maximum porosity being the same, and preferably the porosity of the points with minimum porosity being the same.

[0162] Example 21: A filter element according to Example 20, wherein the periphery comprises four points of maximum porosity and four points of minimum porosity.

[0163] Example 22: An aerosol generating article comprising a filter element according to any of the preceding examples and an aerosol-forming substrate.

[0164] Example 23: An aerosol generating system comprising an aerosol generating article according to Example 22 and an aerosol generating device.

[0165] Example 24: A method for manufacturing a filter element for an aerosol-generating article, comprising the following steps: a) A process of providing a foam with substantially uniform porosity, b) A method comprising the step of compressing at least a portion of a foam by wrapping a filter element wrapper around the foam such that the porosity of the foam decreases radially of the filter element.

[0166] Example 25: The method according to Example 24, wherein the foam in step a) has a rectangular parallelepiped shape, and in step b) the rectangular parallelepiped foam is compressed into a rod by tightening a filter element wrapper around the rectangular parallelepiped foam.

[0167] Example 26: The method according to Example 24 or Example 25, wherein the foam from step a) has a uniform porosity.

[0168] Example 27: A method according to any of Examples 24 to 26, wherein the foam in step a) is rectangular in shape and has a square cross-section.

[0169] Example 28: The method according to Example 26 or Example 27, wherein in step b), a rectangular foam with a square cross-section is compressed into a substantially circular rod such that the ratio of the side length of the square cross-section of the rectangular foam in step a) to the outer diameter of the circular rod is 1 to 1.5, preferably 1 to 1.3, and more preferably about 1.

[0170] Example 29: The method according to Example 28, wherein the side length of the square cross-section of the rectangular foam in step a) is 7 mm to 11 mm, preferably 8 mm to 10 mm.

[0171] Example 30: A method according to any one of Examples 24 to 29, wherein in step b), the foam from step a) is compressed such that the porosity changes around the periphery of the foam, preferably in a regular manner, and preferably the periphery is the outer circumference of the foam.

[0172] Example 31: The method according to Example 30, wherein the periphery comprises a plurality of points with maximum porosity, the points with maximum porosity being equidistant along the periphery, and the periphery comprises a plurality of points with minimum porosity, the points with minimum porosity being equidistant along the periphery, preferably the porosity of the points with maximum porosity being the same, and preferably the porosity of the points with minimum porosity being the same.

[0173] Example 32: A filter element according to Example 31, wherein the periphery has four points of maximum porosity and the periphery has four points of minimum porosity.

[0174] Example 33: A filter element for an aerosol-generating article produced by a method for manufacturing a filter element for an aerosol-generating article according to any of Examples 24 to 32.

[0175] Features described in relation to one embodiment may be equally applicable to other embodiments of the present invention.

[0176] The present invention will be further described with reference to the attached drawings, for illustrative purposes only. [Brief explanation of the drawing]

[0177] [Figure 1] Figure 1 illustrates the manufacturing process of the filter element of the present invention. [Figure 2] Figure 2 shows different perspective views of the filter element of the present invention. [Figure 3] Figure 3 shows a comparison of the filtration performance of the filter element of the present invention with that of a conventional filter element. [Modes for carrying out the invention]

[0178] Figure 1 illustrates the manufacturing of the filter element 10 of the present invention. Figures 1A and 1B show a rectangular foam 12. The foam 12 is made from regenerated cellulose. Figure 1A shows a side view of the rectangular foam. Figure 1B shows a cross-section of the rectangular foam. The rectangular foam may have a uniform porosity. The rectangular foam is wrapped around a filter element wrapper 14 to form the filter element 10 of the present invention shown in Figures 1C and 1D. Figure 1C shows a side view of the filter element. Figure 1D shows a cross-section 16 of the filter element along its long axis. The rectangular foam 12 is compressed into a solid cylindrical foam 12 having a substantially circular cross-section. The filter element wrapper 14 may be tightened around the foam 12. The porosity of the solid cylindrical foam 12 decreases in the radial direction of the filter element 10. The porosity of the solid cylindrical foam 12 decreases radially around the filter element 10 due to compression of the peripheral portion of the foam by the filter element wrapper 14. One or more of the radial porosity gradient and the absolute value of the porosity of the peripheral portion of the foam 12 may be tuned by adjusting the compression. For example, the filter element wrapper 14 may be wrapped more tightly around the foam 12 to reduce the porosity of the peripheral portion of the foam 12.

[0179] The foam 12 includes a high porosity region 18. The high porosity region 18 is arranged around the center of the foam 12. The high porosity region 18 is substantially not compressed by the filter element wrapper. The high porosity region 18 is substantially star-shaped. The foam also includes a low porosity region 20. The low porosity region 20 is arranged around the periphery of the foam 12. The low porosity region 20 includes four spindle-shaped round protrusions 22.

[0180] During use, the filter element 10 may be part of the aerosol generating article. The aerosol generating article may include an aerosol generating substrate. The filter element may be located at the proximal end of the article. The user may suck on the filter element to draw the aerosol formed from the aerosol generating substrate through the filter element into the user's mouth. Due to the lower porosity of the low porosity region 20 compared to the porosity of the high porosity region 18, the aerosol may flow faster through the high porosity region 18 and then through the low porosity region 20. Due to the difference in aerosol velocity between the high porosity region 18 and the low porosity region 20, the filtration efficiency of the filter element may be improved. Components of the aerosol that are more efficiently removed in slow flow may be more efficiently removed in the low porosity region. Components of the aerosol that are more efficiently removed in high flow may be more efficiently removed in the high porosity region. The sustainability of the filter element is improved by the use of foam made from regenerated cellulose.

[0181] Figure 2 shows different perspective views of the filter element of the present invention. Findings relating to Figure 1 apply correspondingly to Figure 2. Figure 2A shows an oblique view of the filter element. Figure 2B shows a front view of the filter element. Figure 2C shows the filter element more clearly for the reader, with a portion of the filter element wrapper 14 removed, showing the rectangular foam before the filter element wrapper 14 is wrapped around the foam 12.

[0182] Figure 3 shows a comparison of the filtration performance of the filter element of the present invention with that of a conventional filter element. Figure 3A shows a comparison of the carbon monoxide yield of the filter element of the present invention with that of a conventional cellulose acetate tow filter element. Figure 3B shows a comparison of the glycerol yield of the filter element of the present invention with that of a conventional cellulose acetate tow filter element. Figure 3C shows a comparison of the nicotine yield of the filter element of the present invention with that of a conventional cellulose acetate tow filter element. The yields obtained by the filter element of the present invention and the conventional cellulose acetate tow filter element are equivalent for each compound. As a result, the filter element of the present invention may be used to replace a conventional cellulose acetate tow filter element. The filter element of the present invention provides filtration performance equivalent to that of a conventional cellulose acetate tow filter element, while providing improved sustainability compared to a conventional cellulose acetate tow filter element.

Claims

1. A filter element for an aerosol generating article, wherein the filter element comprises a filter material, the filter material includes a foam, and the foam is configured such that the porosity of the foam decreases in the radial direction of the filter element.

2. The filter element according to claim 1, wherein the porosity at the center of the foam is higher than the porosity at the periphery of the foam.

3. The filter element according to claim 2, wherein the ratio of the void ratio at the periphery of the foam to the void ratio at the center of the foam is 1:1.3 to 1:2.67, preferably 1:1.5 to 1:2.1, and more preferably about 1:1.

75.

4. The filter element according to claim 2 or 3, wherein the porosity in the periphery of the foam is 0.3 to 0.5, and the porosity in the center of the foam is 0.6 to 0.

8.

5. The filter element according to any one of claims 1 to 4, wherein the foam is a foam made of a cellulose-based material, preferably a foam made of a regenerated cellulose material.

6. The filter element according to claim 5, wherein the foam is viscose foam.

7. The filter element according to any one of claims 1 to 6, wherein the filtration material does not contain cellulose acetate.

8. The filter element according to any one of claims 1 to 7, wherein the filter element comprises a filter element wrapper, and the filter element wrapper is configured to at least partially, preferably completely, surround the filtration material.

9. The filter element according to claim 8, wherein the filter element wrapper is configured to compress at least a peripheral portion of the foam, such as by facilitating the shape of the foam.

10. The filter element according to any one of claims 1 to 9, wherein the filter element has a cylindrical shape, and preferably the filter element is a rod.

11. The filter element according to any one of claims 8 to 10, wherein the filter element wrapper is configured to compress the foam into a cylindrical rod having a substantially circular cross-section, and preferably the foam of the filter element is derived from a cuboidal foam of uniform density.

12. An aerosol generating article comprising a filter element according to any one of claims 1 to 11 and an aerosol-forming substrate.

13. An aerosol generating system comprising the aerosol generating article described in claim 12 and an aerosol generating device.

14. A method for manufacturing a filter element for an aerosol-generating article, comprising the following steps: a) A step of providing a foam with substantially uniform porosity, b) A method comprising the step of compressing at least a portion of the foam by wrapping a filter element wrapper around the foam such that the porosity of the foam decreases radially of the filter element.

15. The method according to claim 14, wherein the foam in step a) has a rectangular parallelepiped shape, and in step b) the rectangular parallelepiped foam is compressed into a rod by tightening the filter element wrapper around the rectangular parallelepiped foam.

Images