CN114745977A

CN114745977A - Aerosol-generating article filter with novel filter material

Info

Publication number: CN114745977A
Application number: CN202080083997.5A
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: 2020-11-30
Publication date: 2022-07-12
Also published as: EP4069004A1; EP4069004C0; WO2021110596A1; US20230000140A1; EP4069004B1; KR20220110511A; JP2023505461A; BR112022010055A2

Abstract

An aerosol-generating article (10) (100) (310) comprises: an aerosol-generating substrate (12) (114) (312); and a filter (18) (122) (314) axially aligned with the aerosol-generating substrate, the filter (18) (122) (314) comprising at least one filter segment (126) (318) of filtration material comprising a plurality of fibers comprising a polyhydroxyalkanoate compound, wherein the fibers have a denier per filament (dpf) of between 5.0 and 12.0. At least one filter segment comprises at least 20% by weight of the polyhydroxyalkanoate compound.

Description

Aerosol-generating article filter with novel filter material

Technical Field

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

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 filter segments of fibrous filter material, such as cellulose acetate tow, defined by a paper filter segment wrapper. Conventionally, the wrapped tobacco rod and 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 heat transfer 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 comprising a porous filtration 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.

Cellulose acetate and many other commonly used filter materials are not highly biodegradable. However, alternative dispersible or degradable materials often do not provide acceptable filtration efficiency and smoking experience for the consumer. 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.

It would be desirable to provide new and improved aerosol-generating articles having enhanced biodegradation characteristics compared to known articles comprising conventional filter materials, such as cellulose acetate. It would be particularly desirable to provide such new aerosol-generating articles to consumers that provide an improved smoking experience. It is also desirable to provide an aerosol-generating article: 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 aerosol-generating articles for generating an inhalable aerosol upon heating or combustion. The aerosol-generating article may comprise a rod of aerosol-generating substrate, and a filter segment axially aligned with the rod. The filter segment may include a filter material formed from a plurality of fibers containing a Polyhydroxyalkanoate (PHA) compound. The fibers of the PHA compound may have a denier per filament (dpf) of between 5.0 and 12.0.

In addition, the present disclosure relates to a filter for an aerosol-generating article. The filter may comprise at least one filter segment of filter material. The filter segment may include a filter material formed from a plurality of fibers containing a Polyhydroxyalkanoate (PHA) compound. The fiber comprising the PHA compound may have a denier per filament (dpf) of between 5.0 and 12.0.

According to the present invention there is provided an aerosol-generating article comprising an aerosol-generating substrate and a filter in axial alignment with the aerosol-generating substrate, the filter comprising at least one filter segment of filter material comprising a plurality of fibres comprising a Polyhydroxyalkanoate (PHA) compound. The fibers have a denier per filament (dpf) of between about 5.0 and about 12.0.

In accordance with the present invention, there is also provided a filter comprising at least one filter segment of filter material comprising a plurality of fibers comprising a Polyhydroxyalkanoate (PHA) compound. The fibers have a Denier Per Filament (DPF) of between about 5.0 and about 12.0.

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

A conventional cigarette will light 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, the aerosol is 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.

The filter of the invention is particularly useful as a filter for a mouthpiece in a heated aerosol-generating article in which an aerosol-generating substrate is heated to generate an aerosol and the substrate is non-combustible. However, the filters of the invention are also suitable for use as filters for combustible smoking articles in which the aerosol-generating substrate is combusted during use to generate an aerosol.

As used herein, the term "aerosol-generating substrate" describes a substrate that is capable of releasing volatile compounds that can form an aerosol when heated (including combustion). The aerosol generated by the aerosol-generating substrate may be visible or invisible and may comprise vapour (e.g. fine particulate matter in the gaseous state, which is typically a liquid or solid at room temperature) as well as droplets of gas and condensed vapour. As used herein, the term "aerosol" encompasses aerosols produced when a substrate in a heated aerosol-generating article is heated and aerosols produced when a substrate in a combustible smoking article is combusted.

As defined above, the present invention provides a filter for an aerosol-generating article comprising at least one filter segment comprising a filter material formed from a plurality of fibers comprising a PHA compound, the fibers having a denier per filament value in the range of about 5.0 to 12.0. The PHA-containing fibers are hereinafter referred to as "PHA fibers". A filter segment comprising a plurality of PHA-containing fibers is hereinafter referred to as a "PHA filter segment".

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. 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 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.

In accordance with the present invention, the filter segment is formed with PHA fibers having a relatively high denier per filament (dpf) of between about 5.0 and about 12.0. By providing a relatively high fiber weight with a dpf within this range, it has been found that the PHA filter segment provides an improved level of retention of water in the aerosol passing through the filter. In particular, the PHA filter segments can capture and retain a greater proportion of water from an aerosol than equivalent filter segments formed from cellulose acetate tow. Such characteristics of PHA filter segments may be particularly desirable in aerosol-generating articles in which the aerosol-generating substrate is heated rather than combusted to produce an aerosol. For example, aerosols generated from such heated aerosol-generating articles may have a relatively high water content due to the inclusion of additional humectants (such as glycerin or polypropylene glycol) that release additional water.

In addition, it has been advantageously found that the improved level of retention of water by the PHA filter segment improves the sensory experience for the consumer.

It has also been found that providing PHA filter segments having PHA fibers having a relatively high dpf (between 5.0 and 12.0) provides a relatively low Resistance To Draw (RTD), which may be desirable for certain filter designs, for example where low filtration efficiency is preferred. The PHA filter segment preferably provides a filtration efficiency of less than 50% or more preferably less than 30%. Providing a relatively low RTD may be particularly desirable for heated aerosol-generating articles in which the aerosol-generating substrate is heated rather than combusted to produce an aerosol. In such articles, the use of PHA filter segments as defined above advantageously enables optimization of the sensory experience for the consumer due to low filtration efficiency.

Where relatively long filter segments are required, it may furthermore be desirable to provide a relatively low RTD. This may be the case, for example, where the filter is combined with a relatively short aerosol-generating substrate, as in certain heated aerosol-generating articles. Because of the low RTD, relatively long PHA filter segments can be incorporated without increasing the overall RTD of the aerosol-generating article beyond a consumer acceptable level.

Furthermore, providing a relatively low RTD may be beneficial to the consumer in reducing the potential impact on the smoking experience due to clogging of vents provided on the aerosol-generating article. For example, the vent may be blocked due to incorrect insertion of the aerosol-generating article into the aerosol-generating device during use. Similarly, in aerosol-generating articles in which a non-porous outer wrapper is used, it may be desirable to provide a relatively low RTD. In both cases, the RTD will remain low enough to provide an acceptable smoking experience even if ventilation is not provided to the aerosol-generating article.

PHA fibers having a dpf value between 5.0 and 12.0 may have a significantly larger cross-section than conventionally used fibers, such as cellulose acetate fibers. The inclusion of relatively large PHA fibers within a PHA filter segment results in a relatively low exposed surface area within the PHA filter segment because the number of fibers required to form the PHA filter segment will be lower than the number of fibers with a lower dpf. By minimizing the exposed surface area, the extent to which the PHA fibers are exposed to potentially undesirable factors (such as moisture, gases, or bacteria) can also be minimized. This may advantageously improve the stability of the filter under certain storage conditions, thereby providing an improvement in the shelf life of the aerosol-generating article.

It has also been found that filters formed with PHA fibers provide good filter stiffness which can be further enhanced by surrounding the filter segment with a rigid plug wrap.

A denier per filament corresponding to the average denier of the individual PHA fibers within the filter is between about 5.0 and about 12.0. 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 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. The dpf of a filter or filter segment can be readily determined based on measurements of the weight and length of a representative fiber sample from the filter or filter segment.

Thus, the PHA fibers have a denier per filament (dpf) of at least about 5.0. Preferably, the dpf is at least about 5.5, more preferably at least about 6.0, more preferably at least about 6.5, more preferably at least about 7.0.

The PHA fibers additionally have a denier per filament (dpf) of no greater than 12.0. Preferably, the dpf is no greater than about 11.0, more preferably no greater than about 10.0, more preferably no greater than about 9.0, more preferably no greater than about 8.0.

In certain embodiments, the denier per filament (dpf) may be up to about 15.0. For example, the denier per filament (dpf) may be between about 5.0 and about 15.0.

In some embodiments, the denier per filament may be between about 5.5 and about 11.0, or between about 6.0 and about 10.0, or between about 6.5 and about 9.0, or between about 7.0 and about 8.0.

In other embodiments, the denier per filament may be between about 5.0 and about 7.5, or between about 5.0 and about 7.0, or between about 5.0 and about 6.5, or between about 5.0 and about 6.0, or about 5.5.

In other embodiments, the denier per filament may be between about 7.0 and about 10.0, or between about 7.5 and about 10.0, or between about 8.0 and about 9.5, or between about 8.0 and about 9.0, or about 8.0.

Preferably, the total denier of the filter material comprising PHA fibers is between about 10,000 and about 40,000, more preferably between about 15,000 and about 35,000, more preferably between about 15,000 and about 30,000, more preferably between about 20,000 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.

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 the aerosol as it passes through the filter segment can also be controlled. This, in turn, will control the filtration characteristics of the PHA fibers, e.g., the amount of water adsorbed by these fibers, to some extent.

The total external surface area of the PHA fibers within the filter segment is preferably between about 0.08 and about 0.21 square meters per gram, more preferably between about 0.10 and about 0.18 square meters per gram, more preferably between about 0.12 and about 0.15 square meters per gram.

The PHA fibers may 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 0.08 square meters per gram and about 0.12 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 0.15 square meters per gram and about 0.21 square meters per gram.

The PHA fibers provided within the filter of an 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).

The PHA filter segment preferably comprises at least about 5% PHA fibers by weight, more preferably at least about 10% PHA fibers by weight, more preferably at least about 20% PHA fibers by weight, more preferably at least about 30% PHA fibers by weight, more preferably at least about 40% PHA fibers by weight, more preferably at least about 50% PHA fibers by weight, more preferably at least about 60% PHA fibers by weight, more preferably at least about 70% PHA fibers by weight, more preferably at least about 80% PHA fibers by weight, more preferably at least about 90% PHA fibers by weight, more preferably at least about 95% PHA fibers by weight.

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.

Thus, the PHA filter segments are formed with relatively high levels of PHA fibers. This provides enhanced biodegradability of the filter and the aerosol-generating article as a whole. As noted above, it has previously been found that it is technically challenging to form filter segments with a high proportion of degradable polymers that provide acceptable filtration characteristics. However, the inventors have surprisingly found that filter segments incorporating relatively high levels of PHA fibers can be produced that provide desirable levels of filtration characteristics, such as filtration efficiency and resistance to draw.

The PHA fibers of filters according to the present invention may be prepared using any suitable method. Suitable techniques for manufacturing PHA fibers will be known to the skilled artisan and include, but are not limited to, melt spinning, gel spinning, and electrospinning. Preferably, the PHA fibers 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.

The PHA fibers may optionally be crimped in the same manner as the cellulose acetate fibers in existing filter segments.

The PHA filter segments may be formed of fibrous filter material formed only with PHA fibers. However, in certain preferred embodiments of the present invention, the PHA fibers may be combined with a plurality of fibers of an additional biodegradable polymer to form a filter segment. For example, the filter segment preferably 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 preferred embodiments, the PHA filter segment comprises at least about 10% by weight of one such additional biodegradable polymer. More preferably, the PHA 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 PHA filter segment comprises at least about 15% by weight of one such additional biodegradable polymer.

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 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.

PHA fibers can be formed from PHA compounds alone or in combination with one or more other polymers, such as polylactic acid (PLA). Thus, the PHA fibers are formed from a polymer blend comprising the PHA compound.

The PHA filter segment preferably comprises at least about 5% by weight PHA compound, more preferably at least about 10% by weight PHA compound, more preferably at least about 20% by weight PHA compound, more preferably at least about 30% by weight PHA compound, more preferably at least about 40% by weight PHA compound, more preferably at least about 50% by weight PHA compound, more preferably at least about 60% by weight PHA compound, more preferably at least about 70% by weight PHA compound, more preferably at least about 80% by weight PHA compound, more preferably at least about 90% by weight PHA compound, more preferably at least about 95% by weight PHA compound.

The PHA filter segment of the aerosol-generating article according to the present invention preferably further comprises an additive for reducing certain smoke constituents in the aerosol generated by the aerosol-generating substrate. For example, the PHA filter segment preferably further comprises an additive for reducing phenolics and phenolic 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 fibers with additives such as PEG has been found to be particularly effective in reducing phenolic compounds in aerosols generated by aerosol-generating substrates. PHA fibers generally provide good filtration efficiency against undesirable smoke constituents, but are less effective at removing phenolic compounds. The filtration capacity of filters comprising PHA fibers according to the present invention may be further optimized by binding compounds that specifically reduce the level of phenolic compounds in the aerosol generated by the aerosol-generating substrate. This in turn improves the sensory characteristics of the aerosol delivered to the consumer.

In a particularly preferred embodiment, the PHA 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.

PHA filter segments of aerosol-generating articles according to the invention may be modified to provide a desired level of Resistance To Draw (RTD). Because of the relatively large size of the PHA fibers, it can be arranged to provide a relatively low RTD to the PHA filter segment. Thus, the PHA filter segments are particularly suitable for use in filters or mouthpieces of heated aerosol-generating articles, where a relatively low RTD is generally desirable. Alternatively or in addition, the PHA filter segments may be particularly suitable for aerosol-generating articles for which a relatively long mouthpiece or filter is preferred, as an acceptable RTD may still be provided.

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 10 mm H₂And O. More preferably, the RTD of the 27 millimeter filter segment of the PHA filter segment is at least about 12 millimeter H₂O, more preferably at least about 15 mm H₂And 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 18 mm H₂O, more preferably at least about 20 mm H₂And (O). The RTD of the 27 mm filter segment of the PHA filter segment preferably does not exceed about 50 mm H₂O, morePreferably not more than 45 mm H₂O, more preferably not more than about 40 mm H₂And O. For example, the RTD of a 27 mm filter segment of the PHA filter segment may be between about 10 mm H₂O and about 50 mm H₂O, or between about 12 mm H₂O and about 50 mm H₂O, or between about 15 mm H₂O and about 45 mm H₂O, or between about 18 mm H₂O and about 45 mm H₂O, or between about 20 mm H₂O and about 40 mm H₂Between O, or about 25 mm H₂O。

In certain preferred embodiments of the invention, the PHA filter segment has at least about 10 mm H₂RTD of O (based on the length of the PHA filter segments in the article). More preferably, the PHA filter segment has an RTD of at least about 15 mm H₂O, more preferably at least about 20 mm H₂And (O). Even more preferably, in the aerosol-generating article according to the invention, the RTD of the PHA filter segment is at least about 25 mm H₂O, more preferably at least about 30 mm H₂And 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 100 mm H₂O, more preferably no more than about 80 mm H₂O, more preferably not more than about 60 mm H₂And O. For example, the RTD of the PHA filter segment may be between about 10 mm H₂O and about 100 mm H₂O, or between about 15 mm H₂O and about 80 mm H₂O, or between about 20 mm H₂O and about 80 mm H₂O, or between about 25 mm H₂O and about 60 mm H₂O, or between about 30 mm H₂O and about 60 mm H₂And O is between. Such ranges may be particularly suitable for combustible smoking articles.

In other preferred embodiments of the invention, the PHA filter segment has a H of at least about 10 mm₂RTD of O (based on the length of the PHA filter segments in the article). More preferably, the RTD of the PHA filter segment is at least about 11 mm H₂O, more preferably at least about 12 mm H₂And O. RTD of the PHA filter segment (based on theLength of PHA filter segments in the article) preferably does not exceed about 25 mm H₂O, more preferably not more than about 20 mm H₂O, more preferably not more than about 15 mm H₂And O. For example, the RTD of the PHA filter segment may be between about 10 mm H₂O and about 25 mm H₂O, or between about 11 mm H₂O and about 25 mm H₂O, or between about 12 mm H₂O and about 20 mm H₂O, or between about 12 mm H₂O and about 15 mm H₂Between O, or about 13 mm H₂And (O). Such ranges may be particularly suitable for heated aerosol-generating articles in which the aerosol-generating substrate is heated rather than combusted to produce an aerosol.

"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.

It has further been found that PHA filter segments of aerosol-generating articles according to the invention provide good RTD stability, which means that high variability of RTD can be advantageously 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 PHA filter segment of the aerosol-generating article according to the present invention has a mean radial stiffness of at least 80%, more preferably at least 85%. Thus, the PHA 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 the PHA filter segment may be further increased by surrounding the PHA filter segment with a rigid plug wrap, such as 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 a compressive resistance that is in a direction transverse to the longitudinal axis. 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:

the recess diameter after the load is set. 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, 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. 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 above test 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.

As mentioned above, the use of PHA fibers for the production of a filter segment of an aerosol-generating article according to the invention advantageously provides improved biodegradability compared to conventional cellulose acetate filters.

Preferably, the PHA filter segment has a biodegradability in aqueous medium of at least about 45%, more preferably at least about 50% and most preferably at least about 55%, when measured according to the test Method described in ISO 14851(Determination of the optimal microbiological biodegradability in an aqueous medium-Method by measuring the oxidative degradation in a closed respirometer (2005)).

Under the same test conditions, the cellulose acetate filter segments showed a biodegradability of about 30%. It can thus be seen that the use of PHA fibers instead of cellulose acetate fibers to form the filter segment provides a significant improvement in the biodegradability of the filter segment.

The dimensions of the PHA filter segment may vary depending on the type of aerosol-generating article into which the filter segment is incorporated.

Preferably, the PHA filter segment has a length of at least about 4 millimeters, more preferably at least about 5 millimeters, more preferably at least about 7 millimeters, and most preferably at least about 10 millimeters.

Preferably, the PHA filter segment has a length of less than or equal to about 30 millimeters, a length of less than or equal to about 27 millimeters, more preferably a length of less than or equal to about 25 millimeters, and most preferably a length of less than or equal to about 20 millimeters.

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

For embodiments of the invention in which the aerosol-generating article is in the form of a combustible smoking article, as described in more detail below, the length of the PHA filter segment is preferably between about 20 mm and about 30 mm, more preferably between about 25 mm and about 30 mm, most preferably about 27 mm.

For alternative embodiments of the invention in which the aerosol-generating article is in the form of a heated aerosol-generating article having an aerosol-generating substrate intended to be heated by an electrical heating device or an integral heat source, the PHA filter segment preferably has a length of between about 5 mm and about 15 mm, more preferably between about 5 mm and about 10 mm, most preferably about 7 mm, as described in more detail below.

The PHA filter segment preferably has an outer diameter about equal to the outer diameter of the aerosol-generating article. Preferably, the filter segment has an outer diameter of at least 5 mm. The PHA 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 PHA filter segment has an outer diameter of 7.2 millimeters (less than 10% error).

The shape of the PHA filter segment may also vary depending on the desired configuration of the aerosol-generating article. In certain embodiments, the PHA filter segment may be in the form of a solid cylindrical plug of fibrous filter material including PHA fibers. Such a filter segment will therefore provide a similar construction to a conventional filter rod of cellulose acetate tow.

In an alternative embodiment, the PHA filter segment may be in the form of a hollow tube segment. The hollow tube segments have a greater exposed surface area than a cylindrical filter rod of equivalent diameter, which may further improve biodegradation of the PHA filter segments.

The hollow tube section preferably has a wall thickness of at least about 0.3 mm. More preferably, the hollow tube segment has a wall thickness of at least about 0.4 millimeters. Even more preferably, the hollow tube segment has a wall thickness of at least about 0.5 millimeters.

Preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.9 millimeters. More preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.5 millimeters. Even more preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.2 millimeters. Particularly preferably, the hollow tube segment has a wall thickness of less than or equal to about 0.9 millimeters.

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

Where the PHA filter segment is in the form of a hollow tube segment, the filter material may include some cellulose acetate in addition to the PHA fibers. For example, the hollow tube segment may comprise between about 5% and about 15% by weight cellulose acetate. Without wishing to be bound by theory, it should be appreciated that the amount of cellulose acetate in the hollow tube segment may impart desirable filtration and mechanical properties to the hollow tube segment and facilitate the manufacture of the hollow tube segment.

The filter of the aerosol-generating article according to the invention may be a single segment filter comprising only PHA filter segments. Alternatively, the filter of the aerosol-generating article according to the invention may further comprise one or more additional filter segments formed from filter material, which may be disposed upstream or downstream of the PHA filter segment as described above. For example, the PHA filter segments may be combined with one or more axially aligned filter rods formed of fibrous filter material, which may or may not include PHA fibers. Alternatively or in addition, the PHA filter segments may be combined with one or more tubular elements, such as hollow acetate or cardboard tubes. For example, in certain embodiments, the filter may include a support element in the form of a hollow acetate tube. Alternatively or in addition, the PHA filter segment may be combined with an aerosol cooling element.

Preferably, the additional filter segment is formed from a material other than cellulose acetate. Particularly preferably, the additional filter segments comprise PHA fibers, which may optionally be held in a desired shape by means of a suitable binder (such as PVA). Preferably, each of the additional filter segments comprises at least about 25% by weight PHA compound, more preferably at least about 50% by weight PHA compound.

The filter 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 can be incorporated in the form of capsules, which can be disposed in the PHA filter segment, or in an additional filter segment.

Preferably, the filter of an aerosol-generating article according to the invention comprises a capsule located within the PHA filter segment, wherein the capsule contains an additive for modifying the aerosol generated by the aerosol-generating substrate during use. Preferably, the additive is a flavoring agent. As discussed above, using PHA fibers having a dpf value in the range of 5.0 to 12.0 means that the PHA fibers have a relatively large cross section. This in turn means that there is an increased amount of available space between individual fibres compared to filters formed from fibres having lower dpf values. Thus, PHA filter segments formed from PHA fibers having a dpf in this range are particularly suitable for incorporation into capsules. Capsules can be easily incorporated into the PHA filter segments during manufacture. In addition, the capsules will be effectively maintained at the desired axial position within the PHA filter segment.

The filter of the aerosol-generating article according to the 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 at least a portion of the tipping wrapper to be removed 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.

As defined above, the aerosol-generating article according to the present invention further comprises an aerosol-generating substrate, preferably in the form of a rod of aerosol-generating substrate. Preferably, the aerosol-generating substrate is a rod of tobacco material.

The aerosol-generating substrate may have a length of between about 5 millimeters and about 100 millimeters. Preferably, the aerosol-generating substrate has a length of at least about 5 mm, more preferably at least about 7 mm. In addition, or alternatively, the aerosol-generating substrate has a length of preferably less than about 80 mm, more preferably less than about 65 mm, even more preferably less than about 50 mm. In particularly preferred embodiments, the 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 aerosol-generating substrate may have a length of about 10 mm. In a preferred embodiment, the aerosol-generating substrate has a length of about 12 mm.

In certain embodiments, the aerosol-generating article according to the invention is a filter cigarette or other combustible smoking article, wherein the aerosol-generating substrate comprises tobacco material which combusts to form an aerosol. In any such embodiment, the aerosol-generating substrate may comprise a tobacco rod. The tobacco rod may include one or more of cut filler and reconstituted tobacco.

For embodiments in which the aerosol-generating article is in the form of a combustible smoking article, the aerosol-generating substrate will typically be a tobacco rod, preferably having a length of between about 10 mm and about 100 mm, more preferably having a total length of between about 30 mm and about 70 mm. The tobacco rod may include one or more of cut filler and reconstituted tobacco.

As discussed above, the filters of the present invention comprising a PHA segment have particular application in heated aerosol-generating articles in which tobacco material is heated rather than combusted to form an aerosol. This is due, at least in part, to the possibility of providing relatively low levels of RTD for PHA segments having defined dpf ranges as described above. In one type of heated aerosol-generating article, tobacco material is heated by one or more electrical heating elements to produce an aerosol. In another heated aerosol-generating article, the aerosol is generated by heat transfer from a combustible or chemical heat source to a physically separate tobacco material, which may be located within, around or downstream of the heat source. The present invention also encompasses aerosol-generating articles in which a nicotine-containing aerosol is generated from a tobacco material, tobacco extract, or other nicotine source without combustion, and in some cases without heating, such as by a chemical reaction.

For embodiments in which the aerosol-generating article is in the form of a heated aerosol-generating article intended to heat an aerosol-generating substrate to form an aerosol, the aerosol-generating substrate preferably has a length of between about 5 millimetres and about 40 millimetres, more preferably between about 9 millimetres and about 15 millimetres.

For such embodiments in which the aerosol-generating article is in the form of a heated aerosol-generating article, the aerosol-generating substrate is preferably formed from a homogenized tobacco material formed from coalescence of tobacco particles. The aerosol-generating substrate may comprise one or more gathered sheets of homogenised tobacco material. The one or more sheets may be textured. As used herein, the term "textured sheet" means a sheet that has been curled, embossed, gravure, perforated, or otherwise deformed. Alternatively, the aerosol-generating substrate may comprise a plurality of strips or strands of homogenised tobacco material. These ribbons or strands may be substantially aligned with one another in the longitudinal direction, or may be randomly oriented.

The homogenized tobacco material used in the aerosol-generating substrate may have the following tobacco content: by weight on a dry basis, at least about 40 wt%, more preferably at least about 60 wt%, more preferably at least about 70 wt%, and most preferably at least about 90 wt%.

Homogenized tobacco material for use in aerosol-generating substrates 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 the agglomeration of tobacco particles. Alternatively or in addition, the homogenized tobacco material used in the aerosol-generating substrate may contain other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents, and combinations thereof.

Suitable extrinsic binders for inclusion in 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 homogenized tobacco material for use in aerosol-generating substrates are known in the art and include, but are not limited to: cellulosic fibers, softwood fibers, hardwood fibers, jute fibers, and combinations thereof. 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.

Aerosol-generating substrates for heated aerosol-generating articles typically comprise an "aerosol former", that is to say a compound or mixture of compounds which, in use, facilitates formation of an aerosol and is preferably substantially resistant to 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.

The aerosol-generating article according to the present invention may further comprise one or more additional components between the filter and the aerosol-generating substrate. For example, the aerosol-generating article may further comprise one or more of: a support element, an aerosol-cooling element and a transfer element. The construction of such components will be known to the skilled person.

For example, in certain preferred embodiments of the present invention, an aerosol-generating article comprises, in linear order: the aerosol-generating substrate, a support element immediately downstream of the aerosol-generating substrate, an aerosol-cooling element positioned immediately downstream of the support element, and a mouthpiece comprising a PHA filter segment at a downstream end of the filter.

In other preferred embodiments of the invention, the aerosol-generating article comprises, arranged in linear order: an aerosol-generating substrate, a transfer element, an aerosol-cooling element, a spacer element and a mouthpiece filter.

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

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

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 fig. 1 comprises a rod of aerosol-generating substrate 12, a support element provided as a hollow tubular element 14, a cooling element 16, and a mouth end filter segment 18. These four elements are arranged sequentially and coaxially aligned and are wrapped 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 end 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 end 22 of the aerosol-generating article 10 may also be described as the downstream end of the aerosol-generating article 10. The elements of the aerosol-generating article 10 positioned between the mouth end 22 and the distal end 24 may be described as being upstream of the mouth end 22, or alternatively downstream of the distal end 24.

The aerosol-generating substrate 12 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 from 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 positioned immediately downstream of the support element 14 and abuts the support element 16. In use, volatile materials released from the aerosol-generating substrate 12 pass along the aerosol-cooling element 16 towards the mouth end 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 filter rod of fibrous filter material formed from a plurality of PHA fibers having a denier per filament of about 8.0 and a total denier of about 15,000. 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 outer surface area of the PHA fibers corresponds to about 0.1 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 100 shown in figure 2 comprises a combustible heat source 112, a rod of aerosol-generating substrate 114, 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 wrap 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 of aerosol-generating substrate 114 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 filter plug wrap 126.

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 thermally conductive 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 filter rod 126 of fibrous filter material formed of a plurality of PHA fibers having a denier per filament of about 8.0 and a total denier of about 15,000. 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 total external surface area of the PHA fibers corresponds to about 0.1 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 8.0 and a total denier of about 15,000. 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 total external surface area of the PHA fibers corresponds to about 0.1 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 an 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 fig. 4. The aerosol-generating device 212 comprises a power supply and electronics not shown in fig. 4.

Claims

1. An aerosol-generating article, comprising:

an aerosol-generating substrate;

a filter in axial alignment with the aerosol-generating substrate, the filter comprising at least one filter segment of filtration material formed from a plurality of fibers comprising a polyhydroxyalkanoate compound, wherein the fibers have a denier per filament (dpf) of between 5.0 and 12.0, and wherein the at least one filter segment comprises at least 20% by weight of the polyhydroxyalkanoate compound.

2. An aerosol-generating article according to claim 1, wherein the plurality of fibers of the polyhydroxyalkanoate compound have a circular cross-sectional shape and provide a total external surface area within the filter segment of between 0.08 and 0.12 square meters per gram.

3. An aerosol-generating article according to claim 1, wherein the plurality of fibers of the polyhydroxyalkanoate compound have a Y-shaped cross-sectional shape and provide a total external surface area within the filter section of between 0.15 and 0.21 square meters per gram.

4. An aerosol-generating article according to any preceding claim, wherein the total denier of the fiber comprising the polyhydroxyalkanoate compound is between 15,000 and 30,000.

5. An aerosol-generating article according to any preceding claim, wherein the filter material further comprises a plurality of fibres of at least one additional biodegradable polymer.

6. An aerosol-generating article according to any preceding claim, wherein the Resistance To Draw (RTD) of the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound is between 10 millimetres H₂O and 25 mm H₂And O is between.

7. An aerosol-generating article according to any preceding claim, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound further comprises at least 5% by weight of polyethylene glycol.

8. An aerosol-generating article according to any preceding claim, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound has an average radial hardness of at least 80%.

9. An aerosol-generating article according to any preceding claim, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound is surrounded by a wrapper having a basis weight of at least 100 grams per square meter (gsm).

10. An aerosol-generating article according to any preceding claim, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound is in the form of a hollow tubular element.

11. An aerosol-generating article according to any preceding claim, wherein the aerosol-generating substrate has a length of between 5 millimetres and 15 millimetres.

12. An aerosol-generating article according to any preceding claim, wherein the filter segment further comprises a capsule within the plurality of fibers comprising the polyhydroxyalkanoate compound.

13. A filter for an aerosol-generating article, the filter comprising at least one filter segment of filter material comprising a plurality of fibres comprising a polyhydroxyalkanoate compound, wherein the fibres have a denier per filament (dpf) of between 5.0 and 12.0 denier, and wherein the at least one filter segment comprises at least 20% by weight of the polyhydroxyalkanoate compound.