Aerosol generating article comprising natural fibers and associated manufacturing method

Abstract

The present invention concerns an aerosol generating article (10) comprising: - a filter portion (14) comprising a filter sheet gathered to form a rod and a filter wrapper (22) wrapping the filter sheet, the filter sheet being formed of nonwoven substrate comprising natural fibers; - a substrate portion (12) positioned sequentially with the filter portion (14) along an article axis and comprising an aerosol generating substrate; - an article wrapper (21) arranged for wrapping the substrate portion (12) and the filter portion (14), and defining a filter wrapping part covering the filter portion (14); wherein an overall density of a filtering segment (29) comprising the filter portion (14) and the filter wrapping part of the article wrapper (21) is greater than or equal to 0.165 mg / mm3.

Description

[0001] Aerosol generating article comprising natural fibers and associated manufacturing method

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns an aerosol generating article comprising natural fibers. The present invention also concerns a manufacturing method of such an article.

[0004] Advantageously, the aerosol generating article according to the invention comprises an aerosol generating substrate able to form aerosol when being heated by an aerosol generating device. Thus, such type of aerosol generating devices, also known as heat-not- burn devices, is adapted to heat, rather than burn to generate aerosol for inhalation.

[0005] Alternatively, the aerosol generating article according to the invention is a cigarette comprising an aerosol generating substrate intended to be burnt during a smoking session.

[0006] BACKGROUND OF THE INVENTION

[0007] Smoking articles, such as cigarettes have cellulose acetate filters to filter components from the aerosols inhaled by a consumer. However, when the used article is improperly thrown, it often ends up in the environment. Therefore, to decrease the environmental impact, the filters comprising natural materials are becoming a more and more sought-after aim for manufacturers.

[0008] The prior art discloses filters for aerosol generating articles comprising non-woven material comprising natural fibres such as wood cellulose and the like. However, provided with such type of material, the filter hardness tends to be too low so that there is a serious risk of product jam during the manufacturing of the aerosol generating article. The consumer’s acceptance is also much lower when the hardness of the aerosol generating article does not reach the usual standard of the articles having a cellulose acetate filter. It is possible to remedy this problem by increasing the density of the filter material but the pressure drop increases and consequently, the resistance-to-draw may become too high for the consumer. In either case, it can cause an unpleasant smoking / vaping experience for a consumer. Therefore, there is a real challenge in discovering optimal parameters for an aerosol generating article with a sufficient hardness while ensuring a desired level of pressure drop. SUMMARY OF THE INVENTION

[0009] One of the aims of the invention is to propose an aerosol generating article having an optimal hardness while providing a desired level of pressure drop. Thus, the user experience during a smoking / vaping session can be greatly increased.

[0010] For this purpose, the invention relates to aerosol generating article an aerosol generating article comprising:

[0011] - a filter portion comprising a filter sheet gathered to form a rod and a filter wrapper wrapping the filter sheet, the filter sheet being formed of nonwoven substrate comprising natural fibers;

[0012] - a substrate portion positioned sequentially with the filter portion along an article axis and comprising an aerosol generating substrate;

[0013] - an article wrapper arranged for wrapping the substrate portion and the filter portion, and defining a filter wrapping part covering the filter portion; wherein an overall density of a filtering segment comprising the filter portion and the filter wrapping part of the article wrapper is greater than or equal to 0.165 mg / mm3.

[0014] It was discovered by the inventors that for nonwoven substrate, the overall density of the filtering segment is an important factor to ensure a good hardness at the mouth end of the aerosol generating article while providing a desired level of the pressure drop. The overall density of the filtering segment can be determined from physical parameters of the elements forming this segment. These physical parameters are usually known so as the overall density of the filtering segment can be easily calculated and used to determine whether the filtering segment provides a sufficient hardness without carrying out expensive and time-consuming tests. Particularly, the overall density of the filtering segment can be simply compared with a threshold to determine whether the firmness is sufficient or not.

[0015] Additionally, the inventors discovered that when the overall density of the filtering segment is greater than or equal to 0.165 mg / mm3, the provided hardness is sufficient while a low desired level of pressure drop can still be obtained.

[0016] The overall density of the filtering segment can be calculated from the filter sheet weight, the filter wrapper weight, a part of the article wrapper weight and the volume of the filtering segment. The filter sheet weight, the filter wrapper weight and a part of the article wrapper weight can be determined by calculation using the corresponding basis weights and dimensions or, alternatively, by weighing the components. The volume of the filtering segment can be calculated from the external dimensions of the filtering segment.

[0017] In some embodiments, the filter sheet or nonwoven substrate further comprises a binder.

[0018] The natural fibers for the nonwoven substrate may be selected from one or more of wood fibers, cotton fibers, leaf fibers, such as abaca or sisal fibers, bast fibers, such as jute, hemp, flax or kenaf fibers, and / or regenerated cellulose such as viscose and / or lyocell fibers.

[0019] In some embodiments, the natural fibers comprise or consist of cellulose pulp, most preferably wood pulp, the cellulose pulp, most preferably wood pulp preferably being obtained by a kraft process.

[0020] In some embodiment, the binder comprises, preferably consists of, at least one binding agent being a water-based polymer emulsion.

[0021] The binder may be selected from one or more of an aqueous copolymer dispersion of Ethylene Vinyl Acetate (EVA) and a Polyvinyl Acetate (PVAc) a cellulose derivative, such as ethyl / methyl cellulose, hydroxyethylAmethyl cellulose and / or carboxymethyl cellulose and / or a polysaccharide (or a derivative of a polysaccharide) such as dextrin or starch.

[0022] In some embodiments, the binder comprises a combination of ethylene-vinyl acetate (EVA) and PolyVinyl Acetate (PVAc), wherein the weight ratio of EVA to PVAc is preferably between 70:30 and 30:70, more preferably between 60:40 and 40:60 and even more preferably between 55:45 and 45:55.

[0023] In some embodiments, the weight content of natural fibers of the non-woven substrate is comprised between 85% and 95%, preferably between 86.9% and 95%, in particular between 90% and 93%, and the weight content of the binder is comprised between 5% and 15%, preferably between 5% and 13.1%, in particular between 7% and 10%. In some embodiments, the overall density D of the filtering segment is strictly greater than 0.165 mg / mm3, advantageously greater than or equal to 0.170 mg / mm3, and preferably greater than or equal to 0.175 mg / mm3.

[0024] In some embodiments, the overall density D of the filtering segment 29 is at most 0.195 mg / mm3, advantageously less than 0.186 mg / mm3. For example, the overall density D of the filtering segment is about 0.184 mg / mm3or is about 0.195 mg / mm3.

[0025] These values can form different ranges of the overall density D according to any possible combination. For example, the overall density D of the filtering segment may be comprised between 0.165 mg / mm3and 0.186 mg / mm3, between 0.165 mg / mm3and 0.195 mg / mm3, between 0.170 mg / mm3and 0.186 mg / mm3, between 0.170 mg / mm3and 0.195 mg / mm3, between 0.175 mg / mm3and 0.186 mg / mm3, and between 0.175 mg / mm3and 0.195 mg / mm3.

[0026] Provided with these values of the overall density of the filtering segment, an optimal hardness of the aerosol generating article at the mouth end can be achieved.

[0027] The hardness of the filtering segment (i.e. hardness of the aerosol generating article at the mouth end) can be measured using the hardness module (DD60A) proposed by Borgwaldt ® GmbH. To determine the hardness of the filtering segment, twenty test samples are placed on the receptacle and the samples are pressed at their mouth ends with a weight of 2KG load weight for 20 seconds.

[0028] The hardness denotes the resistance to deformation of the aerosol generating article in the region of the filtering segment and is expressed as a percentage according to the formula:

[0029] Hardness (%) = Dd / Ds x 100, where Dd is the reduced diameter of the filtering segment under the set load for the set duration and Ds is the initial diameter of the filtering segment before the load application. The test can for example repeated 5 times and the mean value of hardness is calculated.

[0030] In some embodiments, the measured hardness of the filtering segment (i.e., of the aerosol generating article at the mouth end) can be comprised between 80% and 90%, advantageously between 83% and 86%. According to some embodiments, this measured hardness can be above 83%. According to some embodiments, the measured hardness can be below 90%, more preferably below 89%.

[0031] Advantageously, the filtering segment hardness is measured as follows:

[0032] - 20 test sample filtering segments are placed on a receptacle of a densimeter and the test sample filtering segments are pressed at their mouth ends with a 2 kg load weight for 20 seconds;

[0033] - a test sample filtering segment hardness is calculated each time by the formula: Test sample filtering hardness (%) = Dd / Ds x 100, where Dd is the reduced diameter of the test sample filtering segment under the set load for the set duration and Ds is the initial diameter of the test sample filtering segment before the load application;

[0034] - the filtering segment hardness is equal to the mean of the test sample filtering segments hardness.

[0035] These values of hardness are desired to ensure a necessary hardness of the aerosol generating articles during their manufacturing and use.

[0036] It was additionally discovered by the inventors that the provided values of the overall density D of the filtering segment ensure a good visual appearance when the filtering segment is seen from one of its ends or in cross-section. Particularly, provided with these values, the cross-sectional surface of the filtering segment has no measurable hole having an average maximum surface area of 0.2 mm2or more, preferably of 0.15 mm2or more. Additionally, the average total hole area is lower than 1.6 mm2, preferably lower than 1.5 mm2.

[0037] In some embodiments, the filter wrapper has a basis weight of at least 27 g / m2, more preferably at least 35 g / m2, most preferably at least 40 g / m2. The filter wrapper has a basis weight of at most 100 g / m2, more preferably at most 80 g / m2, most preferably at most 50 g / m2.

[0038] In some embodiments, the filter sheet has a basis weight of at least 35 g / m2, more preferably at least 40 g / m2. Preferably, the filter sheet has a basis weight of about 45 g / m2. In some examples, the filter sheet may have a basis weight of about 50 g / m2. The filter wrapper and / or the filter sheet having these values of the basis weight can be used to achieve the above-mentioned values of the overall density of the filtering segment with relatively standard dimensions of the aerosol generating article.

[0039] In some embodiments, the article wrapper has a basis weight comprised between 30 g / m2and 55 g / m2and / or a thickness comprised between 35 pm and 60 pm.

[0040] These values of the basis weight of the article wrapper can take into account a printed logo or any other printed symbol thereon.

[0041] In some embodiments, the width of the filter sheet is less than 160 mm, preferably comprised between 100 mm and 150 mm. The lower pressure drop will be achieved with the lower width values (e.g., 100-120 mm) whereas the higher pressure drop will be achieved with the higher width values (e.g. 140-150 mm).

[0042] These values of the filter sheet width can ensure a desired pressure drop of the filter and / or a good visual appearance in the cross-section as explained above. The width of the filter sheet is measured when the sheet is not gathered, i.e. , before its assembling with the filter wrapper. This width is measured in a flattened or non-crimped configuration of the sheet.

[0043] In some embodiments, the circumference of the filtering segment is comprised between 21 mm and 25 mm, preferably substantially equal to 21.6 mm (+ / -0.2 mm) or to 24.5 mm (+ / -0.2mm).

[0044] The invention also relates to a manufacturing method of the aerosol generating article according to any one of the preceding claims, comprising the following steps:

[0045] - manufacturing a filter sheet, gathering the filter sheet to form a filter rod, and cutting the filter rod at a suitable length to form a rod-shaped filter;

[0046] - wrapping the rod-shaped filter into a filter wrapper to form a filter portion;

[0047] - assembling the filter portion with a substrate portion by an article wrapper.

[0048] In some embodiments, the manufacturing of the filter sheet comprises feeding a sheet of filter material between a first crimping roller and a second crimping roller of a crimping apparatus while rotating the first crimping roller and the second crimping roller such that ridges of each roller form troughs in the sheet of filter material. Advantageously, each roller comprises a plurality of ridges interleaved with a plurality of ridges of the other roller so that each ridge of a roller is received between a pair of ridges of the other roller. A crimping depth CD corresponds to the depth of penetration of the ridges of the first and second crimping rollers in their interleaved arrangement. The crimping depth CD can be calculated by the difference between the sum of the radial distance between the first roller axis and the crests of the ridges of the first crimping roller and the distance between the second roller axis and the crests of the ridges of the second crimping roller and the distance between the first roller axis and the second roller axis.

[0049] As used herein, the term “crest” refers to the highest surface or point of the ridge.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention and its advantages will be better understood upon reading the following description, which is given by way of non-limiting examples and which is made with reference to the appended drawings, in which:

[0052] - Figure 1 is a schematic view of an aerosol generating article according to the invention;

[0053] - Figure 2 is a schematic view of a crimping apparatus used to manufacture a filter sheet comprised in the aerosol generating article of Figure 1 ; and

[0054] - Figures 3 to 5 show experimental results relative to the aerosol generating article of Figure 1.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] Before describing the invention, it is to be understood that it is not limited to the details of construction set forth in the following description. It will be apparent to those skilled in the art having the benefit of the present disclosure that the invention is capable of other embodiments and of being practiced or being carried out in various ways.

[0057] The expression “substantially equal to” is understood hereinafter as an equality at plus or minus 10% and preferably at plus or minus 5%. As used herein, the term “aerosol generating device” or “device” may include a vaping device to deliver aerosol from a tobacco article received in the device, for example comprising tobacco. The device may be portable. “Portable” may refer to the device being for use when held by a user. The device may be adapted to generate a variable amount of aerosol, e.g. by activating a heating system for a variable amount of time (as opposed to a metered dose of aerosol) using a trigger. The trigger may be user activated, such as a vaping button and / or inhalation sensor. The inhalation sensor may be sensitive to the strength of inhalation as well as the duration of inhalation to enable a variable amount of vapor to be provided (so as to mimic the effect of smoking a conventional combustible smoking article such as a cigarette, cigar or pipe, etc.).

[0058] As used herein, the term “aerosol generating substrate” or “aerosol substrate” or “tobacco substrate” may refer to a material that is designed to deliver aerosol upon heating in an aerosol generating device and which may for example comprise nicotine or tobacco and an aerosol former. Tobacco may take the form of various materials such as shredded tobacco, tobacco cut filler, granulated tobacco, tobacco leaf and / or reconstituted tobacco. Reconstituted tobacco can be produced in the form of a sheet by any suitable process such as paper making process, cast sheet, extrusion / lamination. The sheet can then be gathered, cut or shredded, optionally mixed with cellulose or other fillers, tobacco lamina, stems, aerosol former, additives, flavour (e.g., menthol), acid (e.g., benzoic acid), and wrapped in a wrapper to form a tobacco portion. The filling density of the tobacco portion is not particularly limited, but is usually 250 mg I cm3 to 900 mg I cm3 from the viewpoint of ensuring the performance of the tobacco portion and imparting a good taste. Suitable aerosol formers include: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, acids such as lactic acid, glycerol derivatives, esters such as triacetin, triethylene glycol diacetate, triethyl citrate, 1 ,3-butanediol, glycerin or vegetable glycerin. Suitable amount of aerosol former may be between e.g., 5 wt. % and 50 wt.% of the substrate. In some embodiments, the aerosol generating agent may be glycerol, propylene glycol, or a mixture of glycerol and propylene glycol. The substrate may also comprise at least one of a gelling agent, a binding agent, a stabilizing agent, and a humectant.

[0059] As used herein, the term “aerosol” may include a suspension of precursor as one or more of: solid particles; liquid droplets; gas. Said suspension may be in a gas including air. Aerosol may be formed by the aerosol generating substrate and may comprise one or several components of it. The aerosol is generally obtained by a temperature increase of the aerosol generating substrate, such as at a temperature less than 400°C, preferably up to 350°C.

[0060] As used herein, the term “vaping session” may refer to a using period of the aerosol generated device starting from the activation of the trigger defined above to the moment in which the aerosol generation device is disabled.

[0061] As used herein, the terms “upstream” and “downstream” refer to a position relative to the direction of the flow in the article towards the mouth end.

[0062] As used herein, the term “longitudinal” refers to the extension direction of the article axis. The term “length” refers to a dimension measured according to the article axis.

[0063] In reference to Figure 1 , the aerosol generating article 10 extends according to an article axis X between a mouth end and substrate end. According to this Figure, the aerosol generating article 10 comprises a substrate portion 12 forming the substrate end, a filter portion 14 (also referred as filter) forming the mouth end and a wrapper 16. According to one embodiment, the aerosol generating article 10 is designed to be used with an aerosol generating device, such as an HNB device where the substrate portion 12 is heated and not burnt. For this purpose, the substrate portion 12 is for example configured to be received in a heating chamber of the aerosol generating device where it is heated using any suitable technique known as such. According to another embodiment, the aerosol generating article 10 is a cigarette so as the substrate portion 12 is designed to be at least partially burnt.

[0064] The aerosol generating article 10 has for example a cylindrical shape with a circular or oval cross-section.

[0065] As it is shown in Figure 1 , the substrate portion 12 and the filter portion 14 are arranged successively according to the article axis X. In some other embodiments, the aerosol generating article 10 further comprises a cooling portion arranged between the substrate portion 12 and the filter portion 14. The cooling portion may for example comprise a tubular hollow element cooling the aerosol before entering into the filter portion 14. In a preferred example, the length of the substrate portion 12 is comprised between 10 and 80 mm, preferably between 15 and 60 mm. The filter portion 14 may have a length comprised between 5 mm and 30 mm. The outer circumference of the aerosol generating article 10 is for example comprised between 15 mm and 28 mm, preferably between about

[0066] 21 mm and 27 mm. In case of a circular cross-sectional shape, its circumference may be comprised between 16 mm and 25 mm. The outer circumference may be substantially constant along the whole length of the aerosol generating article 10.

[0067] The substrate portion 12 contains an aerosol generating substrate as defined above. The substrate portion 12 is wrapped in a substrate wrapper (not-shown) which is advantageously rolled around the whole length of the substrate portion 12 and keeps the ends of the substrate portion unwrapped. This substrate wrapper is for example formed by a known cigarette paper. In some examples, the substrate wrapper comprises aluminum such as a laminate of paper layer(s) and aluminum layer.

[0068] The substrate portion 12 and the filter portion 14 are maintained together with the wrapper 16. The wrapper 16 is composed of at least two elements: an outer wrapper 21 , called hereinafter article wrapper 21 (or usually “tipping paper”), and an inner wrapper 22, called hereinafter filter wrapper 22 (or usually “plug wrap”). Particularly, the filter wrapper

[0069] 22 is rolled around the filter portion 14 and the article wrapper 21 is rolled around the filter wrapper 22 and around a part of the substrate portion 12. In Figure 1 , the thickness of the wrappers 21 , 22 is exaggerated in comparison with the other elements of the article 10.

[0070] The article wrapper 21 is designed to fix the filter portion 14 with the filter wrapper 22 to the substrate portion 12. For this purpose, the article wrapper 21 has an overlapping zone with each of the filter wrapper 22 and the substrate wrapper. In other words, the length of the article wrapper 21 may be greater than the length of the filter wrapper 22 to form the overlapping zone with the substrate wrapper. The part of the article wrapper 21 overlapping the filter wrapper 22 is called hereinafter filter wrapping part. In other words, the filter wrapping part of the article wrapper 21 only covers the filter portion 14. The length of the filter wrapping part of the article wrapper 21 is thus substantially equal to the length of the filter portion 14. The article wrapper 21 can present a monolayer structure formed by a tipping paper known as such. The article wrapper 21 has a basis weight comprised for example between 30 g / m2and 55 g / m2and / or a thickness between 35 pm and 60 pm. According to different embodiments, the basis weight of the article wrapper 21 can be substantially equal to 31 , 34, 36, 40, 42, 45, 48 or 53 g / m2and / or the thickness of the article wrapper 21 can be substantially equal to 36, 37, 39, 40, 42, 48, 50 or 57 pm.

[0071] The filter wrapper 22 is for example a plug wrap designed to wrap the filter portion 14 and extends for example according to the whole length of the filter portion 14. The filter wrapper 22 defines thus a downstream part adjacent to the mouth end and an upstream part opposite to the downstream part and adjacent to the substrate portion 12 or to another segment (such as a tube or cooling portion). The filter wrapper 22 is formed for example from a single sheet rolled around the filter portion 14. The filter wrapper 22 overlaps at a small longitudinal sealed seam. The filter wrapper 22 has a basis weight of at least 27 g / m2, more preferably at least 35 g / m2, most preferably at least 45 g / m2. The basis weight of the filter wrapper 22 can for example be less than 70 g / m2, more preferably less than 60 g / m2, more preferably less than 50 g / m2.

[0072] The filter portion 14, the filter wrapper 22 and the filter wrapping part of the article wrapper 21 form together a filtering segment 29. For example, the filtering segment may have a circumference of about 21.5 to 21.8 mm for a “mid slim” aerosol generating article of “mid slim” and about 24.3 to 24.5 for a “King size” aerosol generating article.

[0073] The filter portion 14 contains a filter sheet 31 preferably crimped and gathered in the wrapper to form a filter rod before cutting. The filter portion 14 may further comprise additives such as a binder. In some examples, the filter portion 14 may further comprise a flavouring element, like a flavouring capsule breakable by the user and / or soluble by heating and / or interaction with saliva.

[0074] In some embodiments, the filter portion 14 can also define venting holes 25 extending through the wrapper 16. The ventilation may be formed to control the dilution of the aerosol and, in particular, the amount of tar, nicotine and CO in the delivered aerosol. For example, the ventilation level may be comprised between 10% and 60%, or between 20% and 50%, or between 30% and 40%.

[0075] The filter sheet 31 forming the filter portion 14 is made of a filter material comprising a non-woven substrate comprising natural fibers and a binder. In some embodiments, the weight content of natural fibers of the non-woven substrate is comprised between 85% and 95%, preferably between 86.9% and 95%, in particular between 90% and 93%, and the weight content of the binder is comprised between 5% and 15%, preferably between 5% and 13.1 %, in particular between 7% and 10%.

[0076] The natural fibers may comprise or consist of wood pulp, the wood pulp preferably being obtained by a kraft process and / or the binder comprises at least one binding agent being a water-based polymer emulsion.

[0077] The binder may be selected from one or more of an aqueous copolymer dispersion of Ethylene Vinyl Acetate (EVA) and a Polyvinyl Acetate (PVAc) a cellulose derivative, such as ethyl / methyl cellulose, hydroxyethylAmethyl cellulose and / or carboxymethyl cellulose and / or a polysaccharide (or a derivative of a polysaccharide) such as dextrin or starch.

[0078] In some embodiments, the binder comprises a combination of ethylene-vinyl acetate (EVA) and PolyVinyl Acetate (PVAc), wherein the weight ratio of EVA to PVAc is preferably between 70:30 and 30:70, more preferably between 60:40 and 40:60 and even more preferably between 55:45 and 45:55.

[0079] Advantageously, the filter sheet 31 is crimped to form a plurality of troughs. The troughs are parallel and oriented in the longitudinal direction of the filter portion 14, i.e. according to the article axis X.

[0080] To manufacture the filter sheet 31 , a sheet of filter material is first fed between a first crimping roller 40 and a second crimping roller 42 of a crimping apparatus (shown in Figure 2) while rotating the first crimping roller 40 and the second crimping roller 42. The first crimping roller has a first rotation axis, and the second crimping roller has a second rotation axis and the two rotation axis are preferably parallel and oriented perpendicularly to the longitudinal direction of the filter sheet. Each roller 40, 42 comprises a plurality of ridges 46 interleaved with the ridges of the other roller 40, 42 so as each intermediate ridge 46 of a roller 40, 42 is received between a pair of ridges 46 of the other roller 40, 42, as it is shown in Figure 2. The ridges 46 form then troughs in the sheet of filter material.

[0081] In the example of Figure 2, the ridges 46 are homogenously distributed and have a same shape and / or dimensions. A crimping depth CD, shown in Figure 2, corresponds to the depth of penetration of the ridges 46 of one of the first crimping roller 40 and the second crimping roller 42 between the ridges 46 of the other among the first crimping roller 40 and the second crimping roller 42. More particularly, the crimping depth CD can be calculated by the difference between the sum of the radial distance between the first rotation axis and the crests of the ridges of the first crimping roller and the distance between the second rotation axis and the crests of the ridges of the second crimping roller and the distance between the first rotation axis and the second rotation axis.

[0082] Advantageously, the crimping depth CD is comprised between 0.2 mm and 1.5 mm, preferably between 0.5 mm and 1.2 mm, more preferably 0.6 mm and 1.0 mm. At the filter sheet, the crimping depth CD substantially corresponds to the depth between two troughs on the surface of the sheet opposite to the crests.

[0083] To manufacture the filter portion 14, the nonwoven filter sheet 31 is first cut to have a width less than 160 mm, preferably comprised between 70 mm and 155 mm or between 120 and 150 mm. The sheet is then crimped. Then, the crimped filter sheet 31 is gathered to form a rod and the rod is cut to form a rod-shaped filter forming the length of the filter portion 14. The width of the nonwoven filter sheet is defined in a flattened configuration or without the troughs.

[0084] The gathering of the crimped filter sheet can be performed in a gathering station, in particular by passing the crimped filter sheet through a guide, optionally together with the filter wrapper 22 such that the gathered filter sheet is wrapped into the filter wrapper 22 which holds the gathered filter sheet in the gathered configuration.

[0085] To manufacture the aerosol generating article 10, the rod-shaped filter is wrapped into the filter wrapper 22 to for the filter portion 14. Then, the filter portion 14 is assembled together with the substrate portion 12 wrapped into the substrate wrapper, by the article wrapper 21.

[0086] To provide a desired hardness of the aerosol generating article 10 at the mouth end while ensuring a desired pressure drop (PD), an overall density D of the filtering segment 29 is adapted based on the weight and volume of the filtering segment 29.

[0087] Particularly, the overall density D of the filtering segment 29 may be defined using the following expression:

[0088] D=FLR weight / FLR volume where:

[0089] FLR weight” designates the weight of the filtering segment 29; FLR volume” designates the volume of the filtering segment 29.

[0090] The weight of the filtering segment 29 can be determined using the following expression:

[0091] FLR weight = FS weight + PW weight + TP weight where:

[0092] “FS weight” designates the weight of the filter sheet 31 ;

[0093] “PW weight” designates the weight of the filter wrapper 22;

[0094] “TP weight” designates the weight of the filter wrapping part of the article wrapper 21.

[0095] The filter sheet weight (FS weight) can be determined as follows:

[0096] FS weight = FS basis weight (mg / mm2) * FS width (mm) * FLR length(mm) where:

[0097] “FS basis weight” designates the basis weight of the filter sheet 31 in mg / mm2;

[0098] “FS width” designates the width of the filter sheet 31 in mm;

[0099] “FLR length” designates the length of the filter portion 14 in mm.

[0100] Similarly, the filter wrapper weight (PW weight) can be determined as follows:

[0101] PW weight = PW basis weight (mg / mm2) * PW width (mm) * FLR length(mm) where:

[0102] “PW basis weight” designates the basis weight of the filter wrapper 22 in mg / mm2;

[0103] “PW width” designates the width of the filter wrapper 22 in mm;

[0104] “FLR length” designates the length of the filter portion 14 in mm.

[0105] Similarly, the weight of the filter wrapping part of the article wrapper 21 (TP weight) can be determined as follows:

[0106] TP weight = TP basis weight (mg / mm2) * TP width (mm) * FLR length(mm) where:

[0107] “TP basis weight” designates the basis weight of the article wrapper 21 in mg / mm2;

[0108] “TP width” designates the width of the article wrapper 21 in mm;

[0109] “FLR length” designates the length of the filter portion 14 in mm.

[0110] In an alternative method, the weight of the filtering segment 29 is determined by weighing the filtering segment 29 after its separation, e.g., by separating (by cutting) the segment from the substrate portion 12 of the aerosol generating article. In some embodiments, the basis weight of the article wrapper 21 can also take into account a printed logo or any other printed symbol.

[0111] Finally, the volume of the filtering segment 29 (FLR volume) can be determined as follows:

[0112] FLR volume = TT * r * r * FLR length where r is the filtering segment radius including the filter wrapper and the article wrapper thicknesses.

[0113] Particularly, the overall density D of the filtering segment 29 is adapted to be greater than or equal to 0.165 mg / mm3. For example, the overall density D of the filtering segment 29 is strictly greater than 0.165 mg / mm3, advantageously greater than or equal to 0.170 mg / mm3, and preferably greater than or equal to 0.175 mg / mm3. Moreover, the overall density D of the filtering segment 29 is for example less than 0.190 mg / mm3, advantageously less than 0.186 mg / mm3.

[0114] Several tests have been carried out to show that these values of the combination density D are considered as optimal. Results of these tests are summarized in the table of Figures 3 and 4 where the basis weight of the article wrapper 21 takes into account the printed logo.

[0115] In all of these tests, the hardness of the filtering segment 29 was measured using the hardness module (DD60A) proposed by Borgwaldt® GmbH. To determine the hardness of the filtering segment 29, twenty test samples are placed on the receptacle and the samples are pressed at their mouth ends with a weight of 2KG load weight for 20 seconds.

[0116] The hardness denotes the resistance to deformation of the aerosol generating article in the region of the filtering segment and is expressed as a percentage according to the formula:

[0117] Hardness (%) = Dd / Ds x 100, where Dd is the reduced diameter of the filtering segment 29 under the set load for the set duration and Ds is the initial diameter of the filtering segment 29 before the load application.

[0118] The test is repeated 5 times and the mean value of hardness is calculated. The hardness is considered as advantageous when the measured hardness is between 80% and 90%, preferably between 83% and 87%. As it is shown in Figure 5, the hardness of all of the samples is greater than 83%. Therefore, the hardness is advantageous for all of the samples.

[0119] The pressure drop (PD) of the filter rods was measured (before cutting into filter portions and assembling to form the filtering segments, see the line “filter rod length” in the table of Figures 3 and 4) by the pressure drop module (SODIM-PDV Module) of the Sodiline ® measurement device according to ISO6565:2015. A sample falls through the top insertion guide, filter end first. The sample is stopped at a certain point of the end by a pneumatic cylinder and filter is sealed by latex sleeves, then PD is measured. As it can be seen from the table of Figures 3 and 4, the pressure drop PD of all of the filtering segments is comprised between 38 and 73 mmWC or between 1.83 and 2.69 mmWC / mm. In other words, the pressure drop PD values for each filtering segment are obtained by dividing the corresponding pressure drop PD values for the rod by the number of segments (see line “# of seg” in the table of Figures 3 and 4). It should be noted that the PD of the filtering segment of the aerosol generating article may increase by 0 to 15% compared to the PD of the filter rod. Therefore, the preferred PD values for the filter of the aerosol generating article should be considered between 0 to 15 % higher.

[0120] It was also discovered that the provided values of the overall density D of the filtering segment 29 ensure a good visual appearance when the filtering segment 29 is seen from one of its ends (for example from a substrate end of an aerosol generating article 10) or in cross-section. Particularly, provided with these values of the overall density D, the cross- sectional surface of the filtering segment 29 has no measurable hole having an average maximum surface area of 0.2 mm2or more, preferably of 0.15 mm2or more. Additionally, the average total hole area is lower than 1.6 mm2, preferably lower than 1.5 mm2.

[0121] The “total hole area” of the end cross-sectional surface of a filtering segment is the sum of the area of the holes detectable in the end cross-sectional surface of the filtering segment. The “maximum hole area” or “largest hole area” of the end cross-sectional surface of a filter is the area of the hole having the maximal area among the holes of the end cross-sectional surface of the filtering segment, i.e. the area of the largest hole of the end cross-sectional surface of the filtering segment. The term ’’average” represents the arithmetic mean calculated on the results obtained from 20 samples.

Claims

CLAIMS1. An aerosol generating article (10) comprising:- a filter portion (14) comprising a filter sheet (31) gathered to form a rod and a filter wrapper (22) wrapping the filter sheet (31), the filter sheet being formed of nonwoven substrate comprising natural fibers;- a substrate portion (12) positioned sequentially with the filter portion (14) along an article axis (X) and comprising an aerosol generating substrate;- an article wrapper (21) arranged for wrapping the substrate portion (12) and the filter portion (14), and defining a filter wrapping part covering the filter portion (14); wherein an overall density (D) of a filtering segment (29) comprising the filter portion (14) and the filter wrapping part of the article wrapper (21) is greater than or equal to 0.165 mg / mm3.

2. The aerosol generating article (10) according to claim 1 , wherein the filter sheet (31) further comprises a binder.

3. The aerosol generating article (10) according to claim 1 or 2, wherein the natural fibers are selected from one or more of: wood fibers, cotton fibers, leaf fibers, such as abaca or sisal fibers, bast fibers, such as jute, hemp, flax or kenaf fibers, and / or regenerated cellulose such as viscose and / or lyocell fibers.

4. The aerosol generating article (10) according to claim 1 or 2, wherein the natural fibers comprise or consist of cellulose pulp, the cellulose pulp preferably being obtained by a kraft process, and / or the binder comprises at least one binding agent being a water-based polymer emulsion.

5. The aerosol generating article (10) according to any one of the preceding claims when combined with claim 2, wherein the weight content of natural fibers of the non-woven substrate is comprised between 85% and 95%, preferably between 86.9% and 95%, in particular between 90% and 93%, and the weight content of the binder is comprised between 5% and 15%, preferably between 5% and 13.1%, in particular between 7% and 10%.

6. The aerosol generating article (10) according to any one of the preceding claims, wherein the overall density (D) of the filtering segment (29) is strictly greater than 0.165mg / mm3, advantageously greater than or equal to 0.170 mg / mm3, and preferably greater than or equal to 0.175 mg / mm3.

7. The aerosol generating article (10) according to any one of the preceding claims, wherein the overall density (D) of the filtering segment (29) is at most 0.195 mg / mm3, advantageously less than 0.186 mg / mm3.

8. The aerosol generating article (10) according to any one of the preceding claims, wherein the filter wrapper (22) has a basis weight of at least 27 g / m2, more preferably at least 35 g / m2, most preferably at least 45 g / m2.

9. The aerosol generating article (10) according to any one of the preceding claims, wherein, the article wrapper (21) has a basis weight comprised between 30 g / m2and 55 g / m2and / or a thickness comprised between 35 pm and 60 pm.

10. The aerosol generating article (10) according to any one of the preceding claims, wherein the filter sheet (31) has a basis weight of at least 35 g / m2, more preferably at least 40 g / m2.

11. The aerosol generating article (10) according to any one of the preceding claims, wherein the width of the filter sheet (31) is less than 160 mm, preferably comprised between 100 mm and 150 mm.

12. The aerosol generating article (10) according to any one of the preceding claims, wherein the circumference of the filtering segment (29) is comprised between 21 mm and 25 mm, preferably substantially equal to 21.6 mm (+ / -0.2 mm) or to 24.5 mm (+ / -0.2mm).

13. The aerosol generating article (10) according to any one of the preceding claims, wherein a measured hardness of the filtering segment (29) is above 83%, preferably at least 85%.

14. The aerosol generating article (10) according to any one of the preceding claims, wherein the average total hole area in a cross-sectional surface of the filtering segment is lower than 1.6 mm2, preferably lower than 1.5 mm2.

15. A manufacturing method of the aerosol generating article (10) according to any one of the preceding claims, comprising the following steps:- manufacturing a filter sheet (31), gathering the filter sheet (31) to form a filter rod, and cutting the filter rod at a suitable length to form a rod-shaped filter; - wrapping the rod-shaped filter into a filter wrapper (22) to form a filter portion (14);- assembling the filter portion (14) with a substrate portion (12) by an article wrapper (21).

16. A manufacturing method of the aerosol generating article (10) according to claim15, wherein the filter sheet (31) is crimped before gathering to form the filter rod, preferably wherein the crimping depth (CD) is comprised between 0.2 mm and 1.5 mm.

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