CN114901091A

CN114901091A - Aerosol-generating element comprising a filter with a high content of polyhydroxyalkanoate polymer or copolymer

Info

Publication number: CN114901091A
Application number: CN202080083980.XA
Authority: CN
Inventors: S·帕帕基里罗
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2019-12-03
Filing date: 2020-11-26
Publication date: 2022-08-12
Also published as: BR112022010039A2; JP2023505462A; EP4069002C0; KR20220110533A; US20230014600A1; EP4069002A1; WO2021110540A1; EP4069002B1

Abstract

The present invention provides an aerosol-generating article (10; 100; 310) for generating an inhalable aerosol upon heating, the aerosol-generating article comprising: a rod (12; 114; 312) of aerosol-generating substrate; a filter segment (18; 122; 314) formed of fibrous filter material, the filter segment being arranged in longitudinal alignment with the strip (12; 114; 312); wherein the filter segment (18; 122; 314) comprises at least about 85% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of the fibrous filter material.

Description

Aerosol-generating element comprising a filter with a high content of polyhydroxyalkanoate polymer or copolymer

Technical Field

The present invention relates to a filter for an aerosol-generating article and an aerosol-generating article comprising the filter. The invention also relates to an aerosol-generating system comprising an aerosol-generating device and one such aerosol-generating article.

Background

Conventional aerosol-generating articles such as filter cigarettes typically comprise a cylindrical rod of tobacco cut filler surrounded by a paper wrapper and a cylindrical filter axially aligned with, most often in end-to-end relationship with, the wrapped tobacco rod. Cylindrical filters typically comprise one or more plugs of fibrous filter material, such as cellulose acetate tow, surrounded by plug wrap. Conventionally, the wrapped tobacco rod and the filter are joined by a band of tipping wrapper material, typically made of an opaque paper material which surrounds the entire length of the filter and the adjacent portion of the wrapped tobacco rod.

Aerosol-generating articles in which an aerosol-generating substrate (such as a tobacco-containing substrate) is heated rather than combusted are also known in the art. Typically in such articles, the aerosol is generated by heat transfer from a heat source to a physically separate aerosol generating substrate or material.

By way of example, aerosol-generating articles have been proposed in which an aerosol is generated by electrically heating an aerosol-generating substrate. A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by transferring heat from one or more electric heater elements of the aerosol-generating device to an aerosol-generating substrate of a heated aerosol-generating article. As another example, aerosol-generating articles are also known in which an aerosol is generated by heat transfer from a combustible fuel element or heat source to an aerosol-generating substrate. The combustible fuel element or heat source may be positioned in contact with, within, around or downstream of the aerosol-generating substrate.

During use of one such aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer and entrained in air drawn through the aerosol-generating article. As the released compound cools, the compound condenses to form an aerosol.

Typically, aerosol-generating articles of the type described may comprise a mouthpiece with a filter segment formed from a porous filter material, such as cellulose acetate. In some known aerosol-generating articles, a hollow tubular segment formed of a filter material (such as cellulose acetate) is provided at a location between the aerosol-generating substrate and the mouth end of the article to impart structural strength to the article.

After the aerosol-generating article has been consumed and discarded, it may be desirable for any components of the article comprising the filter material to decompose as quickly as possible. Cellulose acetate and many other commonly used filter materials, however, are not highly biodegradable. However, alternative dispersible or biodegradable materials often do not provide acceptable filtration efficiency and smoking experience for consumers. Furthermore, many known dispersible and degradable materials are not suitable for use in existing manufacturing processes, and would require overly significant modification of existing methods and equipment in order for their use to be commercially viable.

In addition, cellulose acetate has been found to provide relatively high levels of adsorption and capture of water from mainstream smoke when used in conventional smoking articles. Thus, mainstream smoke delivered to a consumer has a significantly reduced moisture content and can be undesirably considered "dry" under certain conditions. This may adversely affect the overall smoking experience.

Accordingly, it would be desirable to provide a new and improved aerosol-generating article having enhanced biodegradation characteristics compared to known articles comprising conventional filter materials, such as cellulose acetate. It would also be desirable to provide a new and improved aerosol-generating article which provides a consumer with an acceptable smoking experience, particularly one which is able to reduce the "dry" smoke effect typically found with articles comprising cellulose acetate as the filter material.

It is desirable to provide an aerosol-generating article that: wherein the Resistance To Draw (RTD) of the length of filter material can be adjusted to achieve an acceptable RTD for the article as a whole. In addition, it is desirable to provide such aerosol-generating articles: which can be efficiently produced in an automated high-speed manufacturing process without requiring major modifications to existing equipment.

Disclosure of Invention

The present disclosure relates to an aerosol-generating article for generating an inhalable aerosol upon heating. The aerosol-generating article may comprise a rod of aerosol-generating substrate material and a filter segment formed from fibrous filter material. The filter segments may be arranged in longitudinal alignment with the strips. The filter segment may comprise at least about 85% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of the fibrous filter material.

In addition, the present disclosure relates to a filter for an aerosol-generating article. The filter may comprise a filter segment formed from fibrous filter material. The filter segment can comprise at least about 85% by weight of fibers comprising polyhydroxyalkanoate PHA polymer or copolymer, based on the total weight of the fibrous filter material.

Additionally, the present disclosure relates to a system comprising an aerosol-generating device and an aerosol-generating article for use with the aerosol-generating device. The aerosol-generating article may comprise a rod of aerosol-generating substrate material and a filter segment formed from fibrous filter material. The filter segments may be arranged in longitudinal alignment with the strips. The filter segment may comprise at least about 85% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of the fibrous filter material.

According to the present invention there is provided an aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising: a rod of aerosol-generating substrate; a filter segment formed of fibrous filter material, the filter segment being arranged in longitudinal alignment with the strip; wherein the filter segment comprises at least about 85% by weight of the total weight of the fibrous filter material based on the PHA polymer or copolymer.

According to the present invention, there is also provided a filter for an aerosol-generating article, the filter comprising a filter segment formed from fibrous filter material, wherein the filter segment comprises at least about 85% by weight of the total weight of fibrous filter material based on PHA polymer or copolymer.

As used herein, the term "longitudinal" refers to a direction corresponding to the major longitudinal axis of an aerosol-generating article, which direction extends between an upstream end and a downstream end of the aerosol-generating article. As used herein, the terms "upstream" and "downstream" describe the relative position of an element or portion of an element of an aerosol-generating article with respect to the direction in which an aerosol is conveyed through the aerosol-generating article during use.

The term "aerosol-generating article" is used herein in connection with the present invention to describe an article in which an aerosol-generating substrate is heated to produce an aerosol and deliver the aerosol to a consumer. As used herein, the term "aerosol-generating substrate" refers to a substrate that is capable of releasing volatile compounds upon heating to generate an aerosol.

A conventional cigarette will ignite when a user applies a flame to one end of the cigarette and draws air through the other end. The localized heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite and the resulting combustion produces inhalable smoke. In contrast, in heated aerosol-generating articles, aerosols are generated by heating a flavour-generating substrate, such as a tobacco-based substrate or a substrate containing an aerosol former and a flavour. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by heat transfer from a combustible fuel element or heat source to a physically separate aerosol-forming material.

As mentioned above, in contrast to existing aerosol-generating articles, the article according to the present invention comprises a filter segment formed of fibrous filter material and comprises at least about 85% by weight PHA polymer or copolymer based on the total weight of the fibrous filter material.

Thus, in the filter segment of the aerosol-generating article according to the invention, the PHA polymer or copolymer comprises at least 85% by weight of the fibrous filter material. This means that the remainder of the fibrous filter material may comprise materials other than PHA polymers or copolymers. Furthermore, this means that other components of the filter segment, such as a plug wrap surrounding the fibrous filter material or an insert (such as a flow restrictor or an additive delivery material, e.g., a frangible capsule) that may be provided at a location in the filter segment, may contain materials other than PHA polymers or copolymers.

Since the fibres containing PHA polymers or copolymers (also referred to as "PHA fibres" in the following) have a lower hydrophilicity than the fibres of other filter materials of equal weight, such as cellulose acetate, it has been found that in the aerosol-generating article according to the invention the filter segments have a significantly lower tendency to absorb water/vapour. Thus, the water content in the mainstream smoke can be advantageously maintained at a high level. This directly solves the "dry smoke" problem often encountered with conventional smoking articles and provides the consumer with an improved smoking experience.

The article according to the invention as a whole is more biodegradable, since the PHA fibres have a much higher level of biodegradability than the fibres of other filtering materials, such as cellulose acetate. At the same time, the aerosol-generating article according to the invention also provides improved sustainability for the production process, since the PHA fibers are obtained by a natural fermentation process.

By adjusting parameters such as denier per filament, total denier, cross-sectional shape, etc., it is possible to adjust the RTD of a filter segment to any given filter length or desired range of filter designs.

The term "denier per filament" (DPF) corresponds to the weight (in grams) of an individual fiber or filament having a length of 9000 meters. Thus, in the present invention, the value of the DPF gives an indication of the thickness of each individual PHA fiber within the filter segment. Denier per filament is expressed in denier, where 1 denier corresponds to 1 gram per 9000 meters.

Preferably, the total denier of the filter material comprising PHA fibers is between about 20,000 and about 50,000 or 40,000, more preferably between about 25,000 and about 30,000.

The "total denier" of the filter material defines the total weight (in grams) of 9000 meters of the bonded fibers forming the filter material. Thus, the total denier of a filter segment corresponds to the filament denier multiplied by the total number of fibers in that filter segment.

In addition, the total weight of the filter may be advantageously controlled, and this may also contribute to the biodegradation of the filter segment and the overall aerosol-generating article.

PHA properties also result in good filter stiffness, which can be further enhanced by surrounding the filter segment with a rigid plug wrap.

An aerosol-generating article according to the present invention comprises a rod of aerosol-generating substrate.

Randomly oriented chips, strands or ribbons of tobacco material may be used to produce strips of aerosol-generating substrate. Alternatively, the rod of aerosol-generating substrate may be formed from one or more gathered sheets of tobacco material, as has been proposed, for example, in international patent application WO-A-2012/164009. Alternative rods for aerosol-generating articles are also proposed, formed from a fine rod of homogenized tobacco material, which rod may be formed by casting, rolling, calendering or extruding a mixture comprising particulate tobacco and at least one aerosol former to form a sheet of homogenized tobacco material. Furthermore, the rod of aerosol-generating substrate may be formed from a rod of homogenized tobacco material obtained by extruding a mixture comprising particulate tobacco and at least one aerosol-former to form a continuous length of homogenized tobacco material.

The outer diameter of the rod of aerosol-generating substrate is preferably approximately equal to the outer diameter of the aerosol-generating article.

Preferably, the rod of aerosol-generating substrate has an outer diameter of at least 5 mm. The rod of aerosol-generating substrate may have an outer diameter of between about 5 mm and about 12 mm, for example between about 5 mm and about 10 mm or between about 6 mm and about 8 mm. In a preferred embodiment, the rod of aerosol-generating substrate has an outer diameter within 7.2 mm to 10%.

The rod of aerosol-generating substrate may have a length of between about 5 mm to about 100 mm. Preferably, the rod of aerosol-generating substrate has a length of at least about 5 mm, more preferably at least about 7 mm. In addition, or as an alternative, the rod of aerosol-generating substrate preferably has a length of less than about 80 mm, more preferably less than about 65 mm, even more preferably less than about 50 mm. In a particularly preferred embodiment, the rod of aerosol-generating substrate has a length of less than about 35 mm, more preferably less than 25 mm, even more preferably less than about 20 mm. In one embodiment, the rod of aerosol-generating substrate may have a length of about 10 millimetres. In a preferred embodiment, the rod of aerosol-generating substrate has a length of about 12 mm.

Preferably, the rod of aerosol-generating substrate has a substantially uniform cross-section along the length of the rod. Particularly preferably, the rod of aerosol-generating substrate has a substantially circular cross-section.

In a preferred embodiment, the aerosol-generating substrate comprises one or more gathered sheets of homogenized tobacco material. Preferably, the one or more sheets of homogenized tobacco material are textured. As used herein, the term "textured sheet" means a sheet that has been curled, embossed, gravure, perforated, or otherwise deformed. The textured sheet for homogenized tobacco material of the present invention may comprise a plurality of spaced indentations, protrusions, perforations or a combination thereof. According to a particularly preferred embodiment of the invention, the rod of aerosol-generating substrate comprises a gathered crimped sheet of homogenized tobacco material surrounded by a wrapper.

As used herein, the term "crimped sheet" is intended to be synonymous with the term "corrugated sheet" and refers to a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, the crimped sheet of homogenized tobacco material has a plurality of ridges or corrugations substantially parallel to the cylindrical axis of the rod according to the invention. This advantageously promotes the gathering of the crimped sheet of homogenized tobacco material to form a rod. It will be understood, however, that the crimped sheet of homogenized tobacco material for use in the invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations disposed at acute or obtuse angles to the cylindrical axis of the rod. The sheet of homogenized tobacco material used in the rod of the article of the invention may be textured substantially uniformly over substantially its entire surface. For example, a crimped sheet of homogenized tobacco material for making rods for aerosol-generating articles according to the invention may comprise a plurality of substantially parallel ridges or corrugations that are substantially evenly spaced across the width of the sheet.

The sheet or web of homogenized tobacco material for use in the present invention may have a tobacco content of at least about 40% by weight on a dry weight basis, more preferably at least about 60% by weight on a dry weight basis, more preferably at least about 70% by weight on a dry weight basis, most preferably at least about 90% by weight on a dry weight basis.

The sheet or web of homogenized tobacco material for use in the aerosol-generating substrate may comprise one or more intrinsic binders (i.e. tobacco endogenous binders), one or more extrinsic binders (i.e. tobacco exogenous binders) or a combination thereof to aid in coalescing the particulate tobacco. Alternatively or additionally, the sheet of homogenized tobacco material used in the aerosol-generating substrate may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof.

Suitable external binders for inclusion in sheets or webs of homogenized tobacco material for use in aerosol-generating substrates are known in the art and include, but are not limited to: gums such as guar gum, xanthan gum, gum arabic and locust bean gum; cellulose binders such as hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides, such as starch; organic acids such as alginic acid; conjugate base salts of organic acids, such as sodium alginate, agar, and pectin; and combinations thereof.

Suitable non-tobacco fibres for inclusion in a sheet or web of homogenized tobacco material for use in aerosol-generating substrates are known in the art and include, but are not limited to: cellulose fibers; softwood fibers; hardwood fibers; jute fibers and combinations thereof. Prior to inclusion in the sheet of homogenized tobacco material for use in the aerosol-generating substrate, the non-tobacco fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping, refining, chemical pulping, bleaching, kraft pulping, and combinations thereof.

Substrates for heated aerosol-generating articles typically comprise an "aerosol former", i.e. a compound or mixture of compounds which in use will promote aerosol formation and preferably substantially resist thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-forming agents include: polyhydric alcohols such as propylene glycol, triethylene glycol, 1, 3-butanediol, and glycerin; esters of polyhydric alcohols, such as monoacetin, diacetin, or triacetin; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyols or mixtures thereof such as propylene glycol, triethylene glycol, 1, 3-butanediol and most preferably glycerol.

Preferably, the aerosol-generating substrate comprises at least 10 wt% aerosol former, more preferably at least 12 wt% aerosol former, more preferably at least about 15 wt% aerosol former. Alternatively or in addition, the aerosol-generating substrate preferably comprises no more than 30% by weight of aerosol former, more preferably no more than about 25% by weight of aerosol former, more preferably no more than about 20% by weight of aerosol former. For example, the aerosol-generating substrate may comprise between about 10% and about 30% by weight aerosol former, or between about 12% and about 25% by weight aerosol former, or between about 15% and about 20% by weight aerosol former. In a particularly preferred embodiment, the aerosol-generating substrate comprises about 18% by weight of aerosol former.

In the aerosol-generating article according to the invention, the filter segment is formed by fibrous filter material and comprises at least 85% by weight of PHA polymer or copolymer based on the total weight of the fibrous filter material.

PHAs are the polyhydroxyesters of 3-, 4-, 5-, and 6-hydroxyalkanoic acids, which are produced by various bacterial species under nutrient limiting conditions with excess carbon, and are found in bacterial cells as discrete cytoplasmic contents. Due to their excellent biocompatibility, PHAs have been proposed for use in various biomedical applications, including drug delivery systems and tissue engineering scaffolds.

PHA molecules typically consist of 600 to 35,000 (R) -hydroxy fatty acid monomer units. Depending on the total number of carbon atoms within the PHA monomer, the PHA can be classified as a short-chain length PHA (scl-PHA; 3 to 5 carbon atoms), a medium-chain length PHA (mcl-PHA; 6 to 14 carbon atoms), or a long-chain length PHA (lcl-PHA; 15 or more carbon atoms).

The first and most common PHA is poly (β -hydroxybutyrate) (PHB). The next member of the PHA family (with a pendant ethyl group) is poly (3-hydroxyvalerate) or PHV. PHB with ethyl groups (HV units) instead of methyl groups makes PHV more flexible and less crystalline than PHB.

The PHA-containing fibers provided within the filter segment of the aerosol-generating article according to the present invention may be formed from any suitable PHA compound, including PHA polymers or copolymers. Suitable PHA compounds include, but are not limited to: polyhydroxypropionates, polyhydroxyvalerates, polyhydroxybutyrates, polyhydroxyhexanoates and polyhydroxyoctanoates. In a particularly preferred embodiment, the PHA compound is poly (3-hydroxybutyrate).

Preferably, in the aerosol-generating article according to the invention, the filter segment comprises at least 85% by weight of PHA polymer or copolymer. Without wishing to be bound by theory, it will be appreciated that higher PHA content in the filter segment is generally associated with improved biodegradability of the filter segment and the overall aerosol-generating article.

In a preferred embodiment, the filter segment comprises at least about 90% by weight PHA polymer or copolymer. Without wishing to be bound by theory, it will be appreciated that higher PHA content in the filter segment is generally associated with improved biodegradability of the filter segment and the overall aerosol-generating article.

More preferably, the filter segment comprises at least about 91% or at least about 92% or at least about 93% or at least about 94% by weight PHA polymer or copolymer. In some particularly preferred embodiments, the filter segment comprises at least about 95% by weight PHA polymer or copolymer.

The remainder of the fibers within the PHA filter segment may comprise any suitable material. Suitable fibrous materials will be known to the skilled person and include, but are not limited to, polylactic acid (PLA) and cellulose acetate.

In some embodiments, the filter segment may comprise some cellulose acetate. Without wishing to be bound by theory, it should be understood that the amount of cellulose acetate in the filter segment may impart desired filtration and mechanical properties to the filter segment and facilitate the manufacture of the filter segment.

In certain embodiments, the filter segment comprises at least about 5% by weight cellulose acetate. By way of example, the filter segment may comprise at least about 6% by weight cellulose acetate or at least about 7% by weight cellulose acetate or at least about 8% by weight cellulose acetate or at least about 9% by weight cellulose acetate. In some embodiments, the filter segment comprises at least about 10% by weight cellulose acetate.

In the aerosol-generating article according to the invention, the filter segment preferably comprises less than about 15 wt% cellulose acetate.

In some embodiments, the filter segment comprises less than about 5% by weight cellulose acetate, preferably less than 3% by weight cellulose acetate, more preferably less than 1% by weight cellulose acetate, and even more preferably less than 0.1% by weight cellulose acetate. This may also help to enhance the biodegradability of the filter segment and the overall aerosol-generating article.

Preferably, the aerosol-generating article according to the present invention comprises less than or equal to about 10 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article. More preferably, the aerosol-generating article according to the present invention comprises less than or equal to about 7 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article. Even more preferably, the aerosol-generating article according to the present invention comprises less than or equal to about 5 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article. This advantageously indicates that not only the filter segment has a low or zero content of cellulose acetate, but also that any other component of the article comprising fibrous filter material is substantially free or free of cellulose acetate. Embodiments of aerosol-generating articles according to the present invention having such low levels of cellulose acetate exhibit particularly advantageous biodegradability.

In some preferred embodiments, the aerosol-generating article according to the present invention comprises less than or equal to about 3 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article. More preferably, the aerosol-generating article according to the present invention comprises less than or equal to about 2 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article. Even more preferably, the aerosol-generating article according to the present invention comprises less than or equal to about 1 wt% of cellulose acetate, measured relative to the total weight of the aerosol-generating article.

In some highly preferred embodiments, the aerosol-generating article according to the invention is substantially free of cellulose acetate.

In some embodiments, the filter segment further comprises at least about 5% by weight of at least one biodegradable polymer selected from the group consisting of: starch, polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), thermoplastic starch and thermoplastic starch blend (TPS), Polycaprolactone (PCL), Polyglycolide (PGA), polyvinyl alcohol (PVOH/PVA), viscose, regenerated cellulose, polysaccharides, cellulose acetate with a Degree of Substitution (DS) of less than 2.1, polyamides, protein-based biopolymers, chitosan-chitin based biopolymers, and combinations thereof. The inventors have found that the inclusion of one or more of these ingredients in the blend of fibrous materials forming the filter segment also helps to enhance the biodegradability of the filter segment and the aerosol-generating article as a whole.

In addition, while it has previously been found that making filaments or fibers comprising PHA using existing techniques and equipment is technically challenging, the inventors have surprisingly found that when PHA is mixed in a blend as described above, filaments or fibers incorporating high levels of PHA can be produced as this makes it easier to form filaments by spinning techniques.

In preferred embodiments, the filter segment comprises at least about 10% by weight of one such additional biodegradable polymer. More preferably, the filter segment comprises at least about 11% or at least 12% or at least 13% or at least 14% by weight of the additional biodegradable polymer. Even more preferably, the filter segment comprises at least about 15% by weight of one such additional biodegradable polymer.

In particularly preferred embodiments, the at least one biodegradable polymer is one or more of PBAT, PCL and PBS. Without wishing to be bound by theory, the inventors have found that the use of one or more of these selected biodegradable polymers helps to improve the mechanical, thermal and morphological properties of the polymer mixture. In particular, it has been found that the combined use of PBAT and PBS provides particularly good balanced mechanical properties, especially in terms of tensile strength and elongation.

In some embodiments, the fibrous filter material comprises at least about 3% by weight of a plasticizer selected from the group consisting of triacetin, triethylene glycol diacetate (TEGDA), ethylene vinyl acetate, polyvinyl alcohol, starch, or combinations thereof.

In some embodiments, the fibrous filter material further comprises a water-based binder. This has the effect of structurally reinforcing the structure of the hollow tube section. By way of example, compounds such as starch binders, methylcellulose or polyvinyl acetate may be used for this purpose.

Preferably, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising the PHA polymer or copolymer and having a denier per filament of at least about 1. More preferably, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising the PHA polymer or copolymer and having a denier per filament of at least about 2. Even more preferably, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising the PHA polymer or copolymer and having a denier per filament of at least about 3.2.

In a preferred embodiment, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising a PHA polymer or copolymer and having a denier per filament of less than or equal to about 10. More preferably, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising the PHA polymer or copolymer and having a denier per filament of less than or equal to about 7.5. Even more preferably, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising the PHA polymer or copolymer and having a denier per filament of less than or equal to about 5.

In some embodiments, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising PHA polymer or copolymer and having a denier per filament of from about 1 to about 10, more preferably from about 2 to about 10, even more preferably from about 3.2 to about 10. In other embodiments, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising PHA polymer or copolymer and having a denier per filament of from about 1 to about 7.5, more preferably from about 2 to about 7.5, even more preferably from about 3.2 to about 7.5. In further embodiments, the fibrous filter material forming the filter segment comprises a plurality of fibers comprising PHA polymer or copolymer and having a denier per filament of from about 1 to about 5, more preferably from about 2 to about 5, more preferably from about 3.2 to about 5.

Without wishing to be bound by theory, the inventors have found that when a filter segment is formed with PHA fibers having a relatively low DPF of between 1.5 and 3.2, the filter segment exhibits a relatively low RTD, which may be desirable for certain filter designs. One such low range DPF also advantageously reduces the total weight of the filter segment, which further improves the biodegradability of the aerosol-generating article.

The transverse cross-sectional shape of the PHA fibers may be varied, for example, to control the outer surface area of the fibers within the filter. By controlling the outer surface area of the PHA fibers, the total surface area of the PHA fibers exposed to mainstream smoke as aerosol passes through the filter segment can also be controlled. This, in turn, will control the filtration characteristics of the PHA fibers to some extent, e.g., the amount of water adsorbed by these fibers.

The total outer surface area of the PHA fibers within the filter segment is preferably between about 0.15 square meters per gram and about 0.55 square meters per gram (please add subranges).

The PHA fibers can have a substantially circular cross-section. In such embodiments, the total external surface area of the PHA fibers within the filter segment is preferably between about 0.15 square meters per gram and about 0.30 square meters per gram.

The PHA fibers can have a Y-shaped cross-section. In such embodiments, the total external surface area of the PHA fibers within the filter segment is preferably between about 0.25 square meters per gram and about 0.55 square meters per gram.

PHA filter segments of aerosol-generating articles according to the invention may be modified to provide a desired level of Resistance To Draw (RTD). Advantageously, the PHA fibers may be arranged to provide a relatively high RTD to the PHA filter segment. Thus, PHA filter segments are particularly suitable for use in filters for combustible smoking articles where a relatively high RTD is generally desired. Alternatively, the PHA filter segments may be particularly suitable for aerosol generating articles for which a relatively short mouthpiece or filter is preferred as an acceptable RTD may still be provided.

Preferably, in the aerosol-generating article according to the invention, 2 of the PHA filter segmentThe RTD of the 7 mm filter segment is at least about 25 mm H ₂ And O. More preferably, the RTD of the 27 mm filter segment of the PHA filter segment is at least about 50 mm H ₂ O, more preferably at least about 100 mm H ₂ And O. Even more preferably, in the aerosol-generating article according to the invention, the RTD of the 27 mm filter segment of the PHA filter segment is at least about 150 mm H ₂ O, more preferably at least about 180 mm H ₂ And O. The RTD of the 27 mm filter segment of the PHA filter segment preferably does not exceed about 300 mm H ₂ O, more preferably not more than 250 mm H ₂ And O. For example, the RTD of a 27 mm filter segment of the PHA filter segment may be between about 25 mm H ₂ O and about 300 mm H ₂ O, or between about 50 mm H ₂ O and about 300 mm H ₂ O, or between about 100 mm H ₂ O and about 250 mm H ₂ O, or between about 150 mm H ₂ O and about 250 mm H ₂ O, or between about 180 mm H ₂ O and about 250 mm H ₂ Between O, or about 200 mm H ₂ O。

Preferably, in aerosol-generating articles according to the invention, the RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) is at least about 25 mm H ₂ And O. More preferably, the RTD of the PHA filter segment is at least about 50 mm H ₂ O, more preferably at least about 100 mm H ₂ And O. Even more preferably, in the aerosol-generating article according to the invention, the RTD of the PHA filter segment is at least about 150 mm H ₂ O, more preferably at least about 180 mm H ₂ And O. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) preferably does not exceed about 300 millimeters H ₂ O, more preferably not more than 250 mm H ₂ And O. For example, the RTD of the PHA filter segment may be between about 25 mm H ₂ O and about 300 mm H ₂ O, or between about 50 mm H ₂ O and about 300 mm H ₂ O, or between about 100 mm H ₂ O and about 250 mm H ₂ O, or between about 150 mm H ₂ O and about 250 mm H ₂ O, or between about 180 mm H ₂ O and about 250 mmRice H ₂ Between O, or about 200 mm H ₂ O。

Preferably, in an aerosol-generating article according to the invention, the RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) is at least about 3020 mm H ₂ And (O). More preferably, the RTD of the PHA filter segment is at least about 22 mm H ₂ O, more preferably at least about 25 mm H ₂ And O. Even more preferably, in the aerosol-generating article according to the invention, the RTD of the PHA filter segment is at least about 28 mm H ₂ O, more preferably at least about 30 mm H ₂ And O. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) preferably does not exceed about 45 millimeters H ₂ O, more preferably not more than 40 mm H ₂ And O. For example, the RTD of the PHA filter segment may be between about 20 millimeters H ₂ O and about 45 mm H ₂ O, or between about 22 mm H ₂ O and about 45 mm H ₂ O, or between about 25 mm H ₂ O and about 40 mm H ₂ O, or between about 28 mm H ₂ O and about 40 mm H ₂ O, or between about 30 mm H ₂ O and about 40 mm H ₂ Between O, or about 37 mm H ₂ O。

"resistance to draw" refers to the static pressure difference between the two ends of the sample as the gas flow traverses the sample under steady conditions where the volumetric flow rate at the output end is 17.5 milliliters per second. The RTD of the sample can be measured using the method specified in ISO standard 6565: 2002.

Filter segments of aerosol-generating articles according to the invention may have a lower RTD than filter segments of cellulose acetate fibers, which may be desirable for certain applications. For example, a relatively low RTD may be advantageous where a relatively low filtration efficiency is desired or a relatively long filter is preferred.

It has further been found that filter segments of aerosol-generating articles according to the invention provide good RTD stability, which means that high variability of RTD can advantageously be avoided. For example, within 20 samples of aerosol-generating articles according to the invention there will typically be a standard deviation of between 2% and 10%, more preferably between 2% and 5% relative to the target RTD.

Preferably, the fibers comprising the PHA polymers or copolymers of the filter segments are crimped.

In some embodiments, the filter segment may include one or more additives for reducing certain constituents in the mainstream smoke. By way of example, the filter segment preferably comprises additives for the reduction of phenol and phenol derivatives. Suitable additives will be known to the skilled person and include, but are not limited to: polyethylene glycol (PEG), triacetin, triethyl citrate, cellulose acetate flakes, or combinations thereof.

Preferably, the filter segment comprises between about 3% and about 15% by weight of additives, more preferably between about 5% and about 9% by weight of additives.

In certain preferred embodiments of the invention, the PHA filter segment comprises polyethylene glycol, such as PEG 400.

The combination of PHA with additives such as PEG has been found to be particularly effective for reducing phenolic compounds in mainstream smoke. PHA fibers generally provide good filtration efficiency against undesirable smoke constituents, but are less effective at removing phenolic compounds. The filtering capacity of the filter segment of the aerosol-generating article according to the invention may be further optimised by incorporating a compound which specifically reduces the level of phenolic compounds in the mainstream smoke. This in turn improves the sensory characteristics of the aerosol delivered to the consumer.

In a particularly preferred embodiment, the filter segment further comprises at least about 5% by weight polyethylene glycol, based on the total weight of the filter material. Preferably, the filter segment comprises no more than 10% by weight of polyethylene glycol, based on the total weight of the filter material.

In other preferred embodiments of the invention, the PHA filter segment further comprises a mixture of cellulose acetate and triacetin. Preferably, the mixture comprises at least 90% by weight of triacetin and at most 10% by weight of cellulose acetate. The mixture may be formed by adding cellulose acetate flakes to triacetin to form a solution. The solution can then be sprayed onto the PHA fibers in the PHA filter segment. This combination has been found to advantageously replicate the combined effect of triacetin and cellulose acetate fibers in the filter of a conventional cigarette.

As noted above, it has been found that PHA fibers absorb less than an equivalent amount of cellulose acetate fibers from the mainstream smoke due to their lower affinity for water. As shown in the examples below, the amount of water absorbed by a PHA filter segment is significantly lower than the amount of water absorbed by a comparative filter segment formed of equal weight cellulose acetate fibers.

For example, the filter segment of the aerosol-generating article of the invention preferably absorbs less than half the amount of water that an equivalent filter segment formed from cellulose acetate fibres would absorb under the same conditions when exposed to water in liquid form.

The reduced absorption of water by PHA fibers in the filter segment of the invention results in a higher water content in the mainstream smoke delivered from the aerosol-generating article during use compared to cellulose acetate.

For example, under ISO conditions, the amount of water in the mainstream smoke collected during smoking of a combustible smoking article consisting of a filter with PHA fibers according to the invention is at least 10% higher, preferably at least 15% higher, than the amount of water in the mainstream smoke collected during smoking of an equivalent combustible smoking article having a filter segment of cellulose acetate tow under the same conditions.

Thus, aerosol-generating articles comprising filters comprising PHA filter segments are capable of delivering mainstream smoke with a higher moisture content, which is more acceptable to consumers on the sensor. In particular, the "dry smoke" effect that may be experienced during smoking of an aerosol-generating article with a conventional cellulose acetate filter may advantageously be reduced.

Fibers of PHA polymers or copolymers comprising filter segments can be made by one of several techniques including melt spinning, gel spinning, and electrospinning. Preferably, the fibers of the PHA polymer or copolymer comprising the filter segment in the aerosol-generating article according to the invention are produced by melt spinning. Melt spinning is generally considered the most economical spinning process because there is no need to recover or evaporate the solvent, as is the case with solution spinning. In addition, the spinning rate of melt spinning is generally quite high, which is advantageous in terms of overall productivity and manufacturing efficiency.

In this process, a viscous melt of a polymer or polymer mixture is extruded through a spinneret containing a plurality of orifices into a chamber, wherein a blast of cold air or gas is directed onto the surface of the filaments emanating from the spinneret. When air impinges on the filaments, the filaments are solidified and collected, such as on a take-up reel. The melt spinning process is advantageously characterized by a defined filament cross-sectional geometry and provides a significant variety of fineness and filament count. By increasing the number of openings in the spinneret, high spinning capacity can be achieved, which is not comparable to other spinning processes.

In some embodiments, the filter segment may generally have a length of at least about 4 millimeters. Preferably, the filter segment has a length of at least about 5 mm. More preferably, the filter segment has a length of at least about 7 millimeters. Even more preferably, the filter segment has a length of at least about 10 millimeters.

In such embodiments, the filter segment may generally have a length of less than or equal to about 30 millimeters. Preferably, the length of the filter segment is less than or equal to about 27 millimeters. More preferably, the length of the filter segment is less than or equal to about 25 millimeters. Even more preferably, the length of the filter segment is less than or equal to about 20 millimeters.

In such embodiments, the length of the filter segment is preferably from about 5 mm to about 30 mm, more preferably from about 10 mm to about 30 mm, even more preferably from about 15 mm to about 30 mm, most preferably from about 20 mm to about 30 mm. Alternatively, in such embodiments, the length of the filter segment may be from about 4 mm to about 27 mm, and preferably from about 5 mm to about 27 mm, more preferably from about 10 mm to about 27 mm, even more preferably from about 15 mm to about 27 mm, and most preferably from about 20 mm to about 27 mm. As another alternative, in such embodiments, the filter segment may have a length of about 4 mm to about 25 mm, and preferably about 5 mm to about 25 mm, more preferably about 10 mm to about 25 mm, even more preferably about 15 mm to about 30 mm, and most preferably about 20 mm to about 25 mm.

The filter segment preferably has an outer diameter approximately equal to the outer diameter of the aerosol-generating article. Preferably, the filter segment has an outer diameter of at least 5 mm. The filter segment may have an outer diameter of between about 5 millimeters and about 12 millimeters, for example, an outer diameter of between about 5 millimeters and about 10 millimeters or between about 6 millimeters and about 8 millimeters. In a preferred embodiment, the filter segment has an outer diameter of 7.2 mm (error less than 10%).

Preferably, in the aerosol-generating article according to the invention, the filter segment has an average radial hardness of at least 80%, more preferably at least 85%. Thus, the filter segment is capable of providing a desired level of filter stiffness, which is comparable to that provided by conventional cellulose acetate tow filters. If desired, the radial stiffness of a filter segment of an aerosol-generating article according to the invention may be further increased by surrounding the PHA filter segment with a rigid plug wrap, e.g., a plug wrap having a basis weight of at least about 80 grams per square meter (gsm), or at least about 100gsm, or at least about 110 gsm.

As used herein, the term "radial stiffness" refers to the resistance to compression in a direction transverse to the longitudinal axis of the filter segment. The radial stiffness of the aerosol-generating article around the filter may be determined by: a load is applied across the article at a location of the filter transverse to the longitudinal axis of the article, and the average (mean) recess diameter of the article is measured. The radial hardness is given by:

wherein D _S Is the original (un-recessed) diameter, and D _d Is the recess diameter after the set load is applied for the set duration. The harder the material, the closer to 100% the hardness.

To determine the stiffness of a portion of an aerosol-generating article, such as a filter segment, the aerosol-generating articles should be aligned parallel in a plane and the same portion of each aerosol-generating article to be tested should be subjected to a set load for a set duration of time. This test was performed using a known DD60A densitometer device (manufactured and commercially available from heinr bougovor GmbH) equipped with a measuring head for an aerosol-generating article, such as a cigarette, and with an aerosol-generating article container.

The load is applied using two load applying cylindrical rods that extend across the diameter of all aerosol-generating articles simultaneously. According to the standard test method of this instrument, the test should be performed such that twenty contact points occur between the aerosol-generating article and the load-applying cylindrical rod. In some cases, the filter to be tested may be long enough that only ten aerosol-generating articles are required to form twenty contact points, with each smoking article contacting two load applying rods (as they are long enough to extend between the rods). In other cases, if the filter is too short to achieve this, twenty aerosol-generating articles should be used to form twenty contact points, where each aerosol-generating article contacts only one of the load applying bars, as discussed further below.

Two further fixed cylindrical rods are located beneath the aerosol-generating article to support the aerosol-generating article and to counteract the load applied by each of these load-applying cylindrical rods.

For a standard operating procedure for such a device, a total load of 2kg is applied for a duration of 20 seconds. After 20 seconds have elapsed (and while the load is still being applied to the smoking article), the depression in the load applying cylindrical rod is determined and then used to calculate the stiffness according to the above equation. The temperature was maintained in the region of 22 degrees celsius ± 2 degrees. The test described above is referred to as the DD60A test. The standard way of measuring the hardness of a filter is when the aerosol-generating article has not been consumed. Additional information regarding the measurement of average radial stiffness can be found, for example, in U.S. published patent application No. 2016/0128378.

In some embodiments, the filter segment described above is the only segment formed from the filtration material forming the mouth end filter of the aerosol-generating article. In other embodiments, the aerosol-generating article may comprise one or more additional filter segments formed from filter material, which may be disposed upstream or downstream of a filter segment comprising a PHA polymer or copolymer as described above. For example, a filter segment comprising a PHA polymer or copolymer may be combined with one or more axially aligned filter plugs formed of fibrous filter material, which may or may not include PHA-containing fibers. Alternatively or additionally, filter segments comprising PHA polymers or copolymers may be combined with one or more tubular elements, such as tubular elements formed of fibrous filter material or paperboard tubes. Alternatively or in addition, the PHA filter segment may be combined with an aerosol cooling element.

The filter segment of the aerosol-generating article according to the invention may optionally comprise a flavour. The flavoring agents can be incorporated using a variety of different means that will be known to the skilled artisan. For example, the flavor may be incorporated in the form of capsules, which may be disposed in a filter segment comprising a PHA polymer or copolymer, or in an additional filter segment of an aerosol-generating article.

The filter segment of the aerosol-generating article according to the present invention is preferably surrounded by an outer wrapper, for example a tipping wrapper which surrounds the filter segment, the downstream end of the aerosol-generating substrate and any additional components which may be disposed therebetween. The tipping wrapper may comprise A removable tipping wrapper portion, as described in WO-A-2017/162838. This enables removal of at least a portion of the tipping wrapper before the aerosol-generating article is discarded. Removal of the tipping wrapper exposes the underlying filter segment and can therefore advantageously accelerate the rate of biodegradation of the filter material.

In some embodiments, aerosol-generating articles according to the present invention may further comprise one or more additional elements, typically assembled in the same packaging material as the rod of aerosol-generating substrate. Examples of such additional elements include support elements adapted to enhance the structural strength of the aerosol-generating article, cooling elements adapted to cool the aerosol before it reaches the filter segment, and the like.

For example, in a preferred embodiment, an aerosol-generating article comprises a rod of aerosol-generating substrates arranged in linear order, a support element located immediately downstream of the support element, an aerosol-cooling element located downstream of the support element, and an outer wrapper surrounding the rod, the support element and the aerosol-cooling element. As mentioned above, the strips, support elements and aerosol-cooling elements are arranged in a linear arrangement and upstream of the filter segments. In a particularly preferred embodiment, the strips, the support element and the aerosol-cooling element are arranged in a linear arrangement and immediately upstream of the filter segment, as described above.

For example, the support element may be provided in the form of a tubular element of fibrous filter material. The fibrous filter material may comprise cellulose acetate. In a preferred embodiment, the fiber filtration comprises a Polyhydroxyalkanoate (PHA) polymer or copolymer.

In another preferred embodiment of the invention, an aerosol-generating article arranged in linear order comprises: an aerosol-generating substrate, a transfer element, an aerosol-cooling element, a spacer element and a filter segment as described above.

In certain preferred embodiments of the present invention, the aerosol-generating article further comprises a combustible heat source at an upstream end of the aerosol-generating article, which is in contact with the upstream end of the aerosol-generating substrate. For example, the aerosol-generating article may comprise a carbonaceous heat source at the upstream end for heating the aerosol-generating substrate to generate an aerosol during use. Suitable sources of carbon-containing heat will be known to the skilled person.

Drawings

The invention will now be further described with reference to the accompanying drawings, in which:

figure 1 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a first embodiment of the present invention, for use with an aerosol-generating device comprising a heater element;

figure 2 shows a schematic longitudinal cross-sectional view of an aerosol-generating article comprising an integral heat source according to a second embodiment of the present invention; and is provided with

Figure 3 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a third embodiment of the present invention;

figure 4 shows a schematic longitudinal cross-sectional view of an aerosol-generating system comprising an electrically operated aerosol-generating device and the aerosol-generating article shown in figure 1.

Detailed Description

The aerosol-generating article 10 shown in figure 1 comprises a rod 12 of aerosol-generating substrate, a support element provided as a hollow tubular element 14, a cooling element 16, and a mouth end filter segment 18. The four elements are arranged sequentially and coaxially aligned and surrounded by a substrate wrapper 20 to form the aerosol-generating article 10. The aerosol-generating article 10 has a mouth end 22 and a distal end 24 located at the end of the article opposite the mouth end 22. The aerosol-generating article 10 shown in figure 1 is particularly suitable for use with an electrically operated aerosol-generating device comprising a heater for heating a rod of aerosol-generating substrate.

In use, air is drawn through the aerosol-generating article from the distal end 24 to the mouth segment 22 by a user. The distal end 24 of the aerosol-generating article may also be described as the upstream end of the aerosol-generating article 10, and the mouth segment 22 of the aerosol-generating article 10 may also be described as the downstream end of the aerosol-generating article 10. Elements of the aerosol-generating article 10 positioned between the mouth segment 22 and the distal end 24 may be described as being upstream of the mouth segment 22, or alternatively downstream of the distal end 24.

The aerosol-generating substrate 24 is located at the very distal or upstream end of the aerosol-generating article 10. In the embodiment illustrated in figure 1, the aerosol-generating substrate 12 comprises an aggregated sheet of crimped homogenized tobacco material surrounded by a wrapper. The crimped sheet of homogenized tobacco material comprises glycerides as aerosol former.

The support element 14 is located immediately downstream of the aerosol-generating substrate 12 and abuts the aerosol-generating substrate 12. In the embodiment shown in fig. 1, the support element is a hollow tube formed of a fibrous filter material. The support element 14 positions the aerosol-generating substrate 12 at the extreme distal end 24 of the aerosol-generating article 10 such that it is penetrable by a heating element of the aerosol-generating device. Indeed, the support element 14 serves to prevent the aerosol-generating substrate 16 from being pushed downstream within the aerosol-generating article 10 towards the aerosol-cooling element 16 when a heating element of an aerosol-generating device is inserted into the aerosol-generating substrate 12. The support element 14 also acts as a spacer to separate the aerosol-cooling element 16 of the aerosol-generating article 10 from the aerosol-generating substrate 12.

The aerosol-cooling element 16 is located immediately downstream of the support element 14 and abuts the support element 14. In use, volatile materials released from the aerosol-generating substrate 12 pass along the aerosol-cooling element 16 towards the mouth segment 22 of the aerosol-generating article 10. The volatile material can be cooled within the aerosol-cooling element 16 to form an aerosol for inhalation by a user. In the embodiment shown in fig. 1, the aerosol-cooling element comprises a tubular element 20. The crimped and gathered polylactic acid sheet defines a plurality of longitudinal channels extending along the length of the aerosol-cooling element 40.

The filter segment 18 is positioned immediately downstream of the aerosol-cooling element 16 and abuts the aerosol-cooling element 16. In the embodiment illustrated in fig. 1, the filter segment 18 comprises a single cylindrical plug of fibrous filter material formed of a plurality of PHA fibers having a denier per filament of about 3 and a total denier of about 27,000. The PHA fibers have a circular cross-sectional shape and are substantially longitudinally aligned with one another along the length of the filter segment. The exposed surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed by melt spinning and are crimped. In more detail, the fibers comprise about 85% by weight PHA polymer or copolymer and 15% by weight PBAT/PBS mixture, wherein the ratio of PBAT to PBS is 1: 1. The plug of fibrous filter material is surrounded by a plug wrap (not shown).

The aerosol-generating article 100 shown in figure 2 comprises a combustible heat source 112, a rod 114 of aerosol-generating substrate, a transfer element 116, an aerosol cooling element 118, a spacer element 120 and a mouthpiece filter segment 122. These elements are arranged in sequence and coaxial alignment and are surrounded by a substrate wrapper to form the aerosol-generating article 100.

The combustible heat sources 112 comprise substantially circular cylindrical bodies of carbonaceous material of about 10 millimetres in length. The combustible heat sources 112 are plug-type heat sources. In other words, the combustible heat sources 112 do not include any air channels extending therethrough.

A rod 114 of aerosol-generating substrate is arranged at the proximal end of the combustible heat source 112. The aerosol-generating substrate 114 comprises a substantially circular cylindrical plug of tobacco material 124 surrounded by a plug wrap 126 of filter plug.

A non-combustible, substantially air impermeable first barrier 128 is arranged between the proximal end of the combustible heat source 112 and the distal end of the aerosol-generating substrate 114. The first barrier 128 comprises a disk of aluminum foil. The first barrier 128 also forms a heat-conducting member between the combustible heat source 112 and the aerosol-generating substrate 114 to conduct heat from the proximal face of the combustible heat source 112 to the distal face of the aerosol-generating substrate 114.

The heat conducting element 130 surrounds a proximal portion of the combustible heat source 112 and a distal portion of the aerosol-forming substrate 114. The heat conducting element 130 comprises an aluminum foil tube. The heat conducting element 130 is in direct contact with the proximal portion of the combustible heat source 112 and the filter plug wrap 126 of the aerosol-generating substrate 114.

The mouthpiece filter 122 comprises a single cylindrical plug 126 of fibrous filter material formed of a plurality of PHA fibers having a denier per filament of about 3 and a total denier of about 27,000. The PHA fibers have a circular cross-sectional shape and are substantially longitudinally aligned with one another along the length of the filter segment. The exposed surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed by melt spinning and are crimped. The plug of fibrous filter material is surrounded by a plug wrap (not shown).

The aerosol-generating article 310 shown in figure 3 is a combustible smoking article comprising an aerosol-generating substrate 312 and a filter 314 arranged in coaxial alignment with one another. The aerosol-generating substrate 312 comprises a tobacco rod surrounded by an outer wrapper (not shown). A tipping wrapper 316 surrounds both the filter 314 and the end of the aerosol-generating substrate 312, and attaches the filter 314 to the aerosol-generating substrate 312.

The filter 314 comprises a single cylindrical plug 318 of fibrous filter material formed of PHA fibers having a denier per filament of about 3 and a total denier of about 27,000. The PHA fibers have a circular cross-sectional shape and are substantially longitudinally aligned with one another along the length of the filter segment. The exposed surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed by melt spinning and are crimped. The plug of fibrous filter material is surrounded by a plug wrap (not shown).

Figure 4 shows a portion of an electrically operated aerosol-generating system 200 which utilises a heater blade 210 to heat a rod 12 of aerosol-generating substrate of the aerosol-generating article 10 shown in figure 1. The heater blade 210 is mounted within an aerosol-generating article chamber within the housing of an electrically operated aerosol-generating device 212. The aerosol-generating device 212 defines a plurality of air holes 214 for allowing air to flow to the aerosol-generating article 10, as indicated by the arrows in figure 4. The aerosol-generating device 212 comprises a power supply and electronics not shown in figure 4.

Comparative example

[ contains a discussion of tests 1 and 2 from IDR? ]

PHA filter segments according to the present invention were produced from PHA fibers, the parameters of which are shown in table 1 below. PHA fibers are formed using a melt spinning process and then crimped and formed into filter segments using standard filter manufacturing equipment. For comparison purposes, conventional Cellulose Acetate (CA) tow filter segments were prepared with similar values for denier per filament (dpf) and total denier.

Table 1: parameters of PHA filter segments and cellulose acetate filter segments

In a first test, the water absorption by exposure to water of PHA filter segments according to the invention and CA filter segments was compared. For each filter segment, the plug wrap was removed and the filter segment was connected to the probe of a tensiometer (KRUSS tensiometer, model K100). The filter segment is moved by the probe downwardly towards the water reservoir and automatically stops when the filter segment comes into contact with the water. The filter segment was kept in contact with water for 300 seconds to enable the filter material to absorb water, and then the filter segment was weighed to determine the amount of water absorbed during the test. This test was repeated three times for each of the PHA filter segments and CA filter segments, and the average water absorption was calculated as shown in table 2 below:

table 2: water absorption of PHA and CA filter segments after Water Exposure

Thus, the amount of water absorbed by the PHA filter segment according to the invention during the test was less than 40% of the amount of water absorbed by the CA filter segment. Thus, this test demonstrates that the affinity of water is significantly reduced for PHA filter segments according to the invention compared to conventional CA filter segments.

In a second test, the water absorption by exposure to moisture of PHA filter segments and CA filter segments according to the invention was compared. For each filter segment, the plug wrap was removed and the fibers forming the filter segment were placed in a petri dish and exposed to air at 22 degrees celsius and 50% relative humidity for 70 hours. This was done in a vapor sorption analyzer (ProUmid SPSx-1. mu.). For each filter segment, the weight of the fibers was measured at the beginning of the test, and the change in weight over time due to the absorption of water vapor by the fibers was measured. For each of the PHA filter segments and the CA filter segments, a value for the sample mass percent difference (% dm) was calculated, which expresses the increase in sample weight as a percentage of the original weight. The% dm values for each of the samples at the end of the 70 hour test are shown in table 3 below:

table 3: water absorption of PHA and CA filter segments after exposure to moisture

The results demonstrate that the amount of water vapor absorbed by the cellulose acetate fibers during the 70 hour test is more than 50 times the amount of water vapor absorbed by the PHA fibers. During the test, the PHA fibers absorbed little water vapor. This further demonstrates that the PHA filter segments according to the present invention have a significantly reduced affinity for water compared to conventional CA filter segments.

In a third test, the absorption of water in mainstream smoke by PHA filter segments according to the invention and conventional CA filter segments was compared. For each of the filter segments, a conventional smoking article is prepared utilizing a combustible tobacco rod and a single segment of filter material forming a filter, as described above with reference to fig. 3. Each of the smoking articles was then smoked on a smoking machine under ISO conditions specified in ISO 3308:2000 (puff volume 35 ml; 2 second puff duration per 60 seconds) and the resulting smoke was analysed. For each of the filter segments, the amount of water in the mainstream smoke collected during the smoking test was measured, as shown in table 4:

table 4: water in mainstream smoke generated during smoking testing under ISO conditions

	PHA filter segment	CA filter tip segment
			Water (mg/smoking article)	0.82	0.68

This demonstrates that, when smoked under equivalent conditions, a smoking article comprising a PHA filter segment produces a mainstream smoke with a water content that is about 20% higher than the water content of mainstream smoke from a smoking article comprising a CA filter segment. This demonstrates that PHA filter segments absorb less water from the mainstream smoke than CA filter segments, thereby reducing the potential problems of dry smoke as described above.

Claims

1. An aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising:

a rod of aerosol-generating substrate, wherein the aerosol-generating substrate comprises at least 10 wt% of aerosol former;

a filter segment formed of fibrous filter material, the filter segment being arranged in longitudinal alignment with the strip;

wherein the filter segment comprises at least about 85% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of the fibrous filter material.

2. An aerosol-generating article according to claim 1, wherein the filter segment comprises at least about 90% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of fibrous filter material.

3. An aerosol-generating article according to claim 1 or 2, wherein the filter segment comprises at least about 95% by weight of Polyhydroxyalkanoate (PHA) polymer or copolymer based on the total weight of fibrous filter material.

4. An aerosol-generating article according to any preceding claim, wherein the filter segment further comprises at least about 5 wt% of at least one biodegradable polymer based on the total weight of fibrous filter material, the biodegradable polymer being selected from the group consisting of: starch, polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), thermoplastic starch and thermoplastic starch blend (TPS), Polycaprolactone (PCL), Polyglycolide (PGA), polyvinyl alcohol (PVOH/PVA), viscose, regenerated cellulose, polysaccharides, cellulose acetate with a Degree of Substitution (DS) of less than 2.1, polyamides, protein-based biopolymers, chitosan-chitin based biopolymers, and combinations thereof.

5. An aerosol-generating article according to claim 4, wherein the filter segment comprises at least about 10 wt% of the at least one biodegradable polymer based on the total weight of fibrous filter material.

6. An aerosol-generating article according to claim 4 or 5, wherein the filter segment comprises less than or equal to about 15 wt% of the at least one biodegradable polymer based on the total weight of fibrous filter material.

7. An aerosol-generating article according to any one of claims 4 to 6, wherein the at least one biodegradable polymer is one or more of PBAT, PCL and PBS.

8. An aerosol-generating article according to any preceding claim, wherein the fibrous filter material comprises a plurality of fibers comprising a Polyhydroxyalkanoate (PHA) polymer or copolymer and having a denier per filament of from about 1 to about 10.

9. An aerosol-generating article according to any preceding claim, wherein the fibrous filter material comprises a plurality of fibers comprising a Polyhydroxyalkanoate (PHA) polymer or copolymer and having a denier per filament of from about 3.2 to about 5.

10. An aerosol-generating article according to any preceding claim, wherein the RTD of the filter segment is between about 35 mm H ₂ O and about 55 mm H ₂ And O is between.

11. An aerosol-generating article according to any preceding claim, wherein the RTD of the filter segment is between about 40 mm H ₂ O and about 50 mm H ₂ And O is between.

12. An aerosol-generating article according to any preceding claim, wherein the fibrous filter material comprises crimped fibres comprising Polyhydroxyalkanoate (PHA) polymers or copolymers.

13. An aerosol-generating article according to any preceding claim, wherein the filter segment has a length of from about 4 mm to about 27 mm.

14. An aerosol-generating article according to any preceding claim, wherein the filter segment has a diameter of from about 5 mm to about 12 mm.

15. A filter for an aerosol-generating article, the filter comprising a filter segment formed from fibrous filter material, wherein the filter segment comprises at least about 85% by weight, based on the total weight of fibrous filter material, of fibers comprising a Polyhydroxyalkanoate (PHA) polymer or copolymer.