Aerosol-generating article filter with novel filter material

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 filter material comprising a plurality of fibers comprising a polyhydroxyalkanoate compound, wherein the fibers have a denier per filament (dpf) between 5.0 and 12.0. The at least one filter segment comprises at least 20% by weight of the polyhydroxyalkanoate compound.

Description

Technical Field

[0001] The present invention relates to a filter for an aerosol-generating article and an aerosol-generating article comprising the filter. Background Art

[0002] 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 the wrapped tobacco rod, most often in an end-to-end relationship. The cylindrical filter typically comprises 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, typically made of an opaque paper material, which surrounds the entire length of the filter and an adjacent portion of the wrapped tobacco rod.

[0003] Aerosol-generating articles in which an aerosol-generating substrate (such as a tobacco-containing substrate) is heated rather than burned are also known in the art. Typically, in such articles, an aerosol is generated by heat transfer from a heat source to a physically separate aerosol-generating substrate or material.

[0004] By way of example, aerosol-generating articles have been proposed in which the aerosol is generated by electrically heating an aerosol-generating substrate. Many prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which the aerosol is generated by heat transfer from one or more electric heater elements of the aerosol-generating device to the aerosol-generating substrate of the heated aerosol-generating article. As another example, aerosol-generating articles in which the aerosol is generated by heat transfer from a combustible fuel element or heat source to the aerosol-generating substrate are also known. The combustible fuel element or heat source can be positioned in contact with the aerosol-generating substrate, within the aerosol-generating substrate, around the aerosol-generating substrate, or downstream of the aerosol-generating substrate.

[0005] During use of such an aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer and become entrained in the air drawn through the aerosol-generating article. When the released compounds cool, they condense to form an aerosol.

[0006] Typically, aerosol-generating articles of the type described may include a mouthpiece comprising 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 between the aerosol-generating substrate and the mouth end of the article to impart structural strength to the article.

[0007] Cellulose acetate and many other commonly used filter materials are not highly biodegradable. However, alternative dispersible or degradable materials often fail to provide consumers with acceptable filtration efficiency and smoking experience. Furthermore, many known dispersible and degradable materials are not suitable for use in existing manufacturing processes, and their use would require significant modifications to existing methods and equipment to be commercially viable.

[0008] It is desirable to provide novel, improved aerosol-generating articles that have enhanced biodegradability compared to known articles comprising conventional filter materials, such as cellulose acetate. It is particularly desirable to provide such novel aerosol-generating articles that provide consumers with an improved smoking experience. It is also desirable to provide an aerosol-generating article in which the resistance to draw (RTD) of a filter material segment can be adjusted to achieve an acceptable RTD for the article as a whole. In addition, it is desirable to provide an aerosol-generating article that can be efficiently produced in an automated, high-speed manufacturing process without requiring major modifications to existing equipment. Summary of the Invention

[0009] The present disclosure relates to an aerosol-generating article for generating an inhalable aerosol when heated or burned. The aerosol-generating article may include a rod of an 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) between 5.0 and 12.0.

[0010] In addition, the present disclosure relates to a filter for an aerosol-generating article. The filter may include 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 fibers containing the PHA compound may have a denier per filament (dpf) between 5.0 and 12.0.

[0011] According to the present invention, an aerosol-generating article is provided, comprising an aerosol-generating substrate and a filter axially aligned with the aerosol-generating substrate, the filter comprising at least one filter segment of filter material, the filter material comprising a plurality of fibers comprising a polyhydroxyalkanoate (PHA) compound, the fibers having a denier per filament (dpf) of between about 5.0 and about 12.0.

[0012] According to 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, wherein the fibers have a denier per filament (DPF) of between about 5.0 and about 12.0.

[0013] 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 generate an aerosol and deliver it to a consumer. As used herein, the term "aerosol-generating substrate" means a substrate that is capable of releasing volatile compounds upon heating or combustion to generate an aerosol.

[0014] A conventional cigarette is ignited when a user applies a flame to one end of the cigarette and draws air through the other end. 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 generates inhalable smoke. In contrast, in heated aerosol-generating articles, an aerosol is generated by heating a flavor-generating substrate, such as a tobacco-based substrate or a substrate containing an aerosol-forming agent and a flavoring agent. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles, as well as aerosol-generating articles in which the aerosol is generated by heat transfer from a combustible fuel element or heat source to a physically separate aerosol-forming material.

[0015] The filters of the present invention are particularly useful as filters for mouthpieces in heated aerosol-generating articles in which an aerosol-generating substrate is heated to generate an aerosol without combusting the substrate. However, the filters of the present invention are also suitable for use as filters for combustible smoking articles in which an aerosol-generating substrate is combusted during use to generate aerosol.

[0016] 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 burned). The aerosol generated by the aerosol-generating substrate may be visible or invisible and may contain vapor (e.g., fine particulate matter in a gaseous state that is typically liquid or solid at room temperature) as well as droplets of gas and condensed vapor. As used herein, the term "aerosol" encompasses aerosols generated when a substrate is heated in heated aerosol-generating articles and aerosols generated when a substrate is burned in combustible smoking articles.

[0017] As defined above, the present invention provides a filter for an aerosol-generating article, the filter comprising at least one filter segment, the filter segment comprising a filter material formed from a plurality of fibers containing 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." The filter segment comprising a plurality of PHA-containing fibers is hereinafter referred to as a "PHA filter segment."

[0018] PHAs are a family of polyhydroxyesters of 3-, 4-, 5-, and 6-hydroxyalkanoic acids that are produced by a variety of bacterial species under nutrient-limited conditions with excess carbon and are found as discrete cytoplasmic inclusions in bacterial cells. 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, PHAs can be classified as short-chain length PHAs (scl-PHAs; 3 to 5 carbon atoms), medium-chain length PHAs (mcl-PHAs; 6 to 14 carbon atoms), or long-chain length PHAs (lcl-PHAs; 15 or more carbon atoms).

[0019] Since PHA fibers have a much higher level of biodegradability than fibers of other filter materials (such as cellulose acetate), the article according to the present invention as a whole has a higher biodegradability. At the same time, since PHA fibers are obtained through a natural fermentation process, the aerosol-generating article according to the present invention also provides improved sustainability for the production process.

[0020] According to the present invention, the filter segment is formed from PHA fibers having a relatively high denier per filament (dpf) between about 5.0 and about 12.0. By providing a relatively high fiber weight having a dpf within this range, it has been found that the PHA filter segment provides an improved level of retention of water in an aerosol passing through the filter. In particular, the PHA filter segment can capture and retain a greater proportion of water from an aerosol than an equivalent filter segment formed from cellulose acetate tow. This characteristic of the PHA filter segment may be particularly desirable in aerosol-generating articles in which the aerosol-generating substrate is heated rather than combusted to produce the aerosol. For example, the aerosol generated from such heated aerosol-generating articles can have a relatively high water content due to the inclusion of an additional humectant (such as glycerol or polypropylene glycol) that releases additional water.

[0021] In addition to this, it has advantageously been found that the improved level of water retention by the PHA filter segment improves the sensory experience for the consumer.

[0022] Furthermore, it has been found that providing a PHA filter segment 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 generate the aerosol. In such articles, the use of a PHA filter segment as defined above can advantageously optimize the sensory experience of the consumer due to the low filtration efficiency.

[0023] Where relatively long filter segments are required, it may also be desirable to provide a relatively low RTD. For example, this may be the case where the filter is combined with a relatively short aerosol-generating substrate, as in certain heated aerosol-generating articles. Due to the low RTD, a relatively long PHA filter segment can be incorporated without increasing the overall RTD of the aerosol-generating article beyond a level acceptable to consumers.

[0024] Furthermore, providing a relatively low RTD can benefit consumers by reducing the potential impact on the smoking experience caused by blockage of ventilation holes provided on the aerosol-generating article. For example, the ventilation holes may become blocked due to improper insertion of the aerosol-generating article into the aerosol-generating device during use. Similarly, providing a relatively low RTD may be desirable in aerosol-generating articles in which a non-porous outer wrapper is used. 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.

[0025] PHA fibers having a dpf value between 5.0 and 12.0 can 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 exposure of the PHA fibers to potentially undesirable factors, such as moisture, gas, or bacteria, can also be minimized. This can advantageously improve the stability of the filter under certain storage conditions, thereby providing an improvement in the shelf life of the aerosol-generating article.

[0026] It has also been found that filters formed with PHA fibers provide good filter hardness, which can be further enhanced by surrounding the filter segment with a rigid plug wrap.

[0027] The denier per filament, which corresponds 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 a single 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 a 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.

[0028] Thus, the PHA fiber has 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, and more preferably at least about 7.0.

[0029] The PHA fibers also 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, and more preferably no greater than about 8.0.

[0030] In certain embodiments, the denier per filament (dpf) can be as high as about 15.0. For example, the denier per filament (dpf) can be between about 5.0 and about 15.0.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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, and 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 combined fibers forming the filter material. Thus, the total denier of a filter segment corresponds to the denier per filament multiplied by the total number of fibers in the filter segment.

[0035] The transverse cross-sectional shape of the PHA fibers can be varied, for example, to control the external surface area of ​​the fibers within the filter. By controlling the external surface area of ​​the PHA fibers, it is also possible to control the total surface area of ​​the PHA fibers exposed to the aerosol as the aerosol passes through the filter segment. This, in turn, can control, to a certain extent, the filtration properties of the PHA fibers, for example, the amount of water adsorbed by these fibers.

[0036] 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, and more preferably between about 0.12 and about 0.15 square meters per gram.

[0037] 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.

[0038] The PHA fibers may 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.

[0039] 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, polyhydroxypropionate, polyhydroxyvalerate, polyhydroxybutyrate, polyhydroxyhexanoate, and polyhydroxyoctanoate. In a particularly preferred embodiment, the PHA compound is poly(3-hydroxybutyrate).

[0040] The PHA filter segment preferably comprises at least about 5 wt% PHA fibers, more preferably at least about 10 wt% PHA fibers, more preferably at least about 20 wt% PHA fibers, more preferably at least about 30 wt% PHA fibers, more preferably at least about 40 wt% PHA fibers, more preferably at least about 50 wt% PHA fibers, more preferably at least about 60 wt% PHA fibers, more preferably at least about 70 wt% PHA fibers, more preferably at least about 80 wt% PHA fibers, more preferably at least about 90 wt% PHA fibers, more preferably at least about 95 wt% PHA fibers.

[0041] The remainder of the fibers within the PHA filter segment may comprise any suitable material. Suitable fiber materials will be known to the skilled person and include, but are not limited to, polylactic acid (PLA) and cellulose acetate.

[0042] 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 described above, it has previously been found that forming filter segments with a high proportion of degradable polymers that provide acceptable filtration characteristics is technically challenging. However, the inventors have surprisingly discovered that filter segments incorporating relatively high levels of PHA fibers can be produced that provide desired levels of filtration characteristics, such as filtration efficiency and resistance to draw.

[0043] The PHA fibers of the filter according to the present invention can be prepared using any suitable method. Suitable techniques for making PHA fibers will be known to those skilled in the art and include, but are not limited to, melt spinning, gel spinning, and electrospinning. Preferably, the PHA fibers are prepared by melt spinning. Melt spinning is generally considered to be the most economical spinning method because no solvent needs to be recovered or evaporated, 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.

[0044] The PHA fibers may optionally be crimped in the same manner as the cellulose acetate fibers in existing filter segments.

[0045] The PHA filter segment can be formed from a fibrous filter material formed solely from PHA fibers. However, in certain preferred embodiments of the present invention, the PHA fibers can be combined with multiple fibers of an additional biodegradable polymer to form the 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 blends (TPS), polycaprolactone (PCL), polyglycolide (PGA), polyvinyl alcohol (PVOH / PVA), viscose, regenerated cellulose, polysaccharides, cellulose acetate having 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 including one or more of these ingredients in the blend of fibrous material forming the filter segment also helps to enhance the biodegradability of the filter segment and the aerosol-generating article as a whole.

[0046] 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% by weight, or at least 12% by weight, or at least 13% by weight, 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.

[0047] The inventors have found that including one or more of these ingredients in the blend of fibrous material forming the filter segment also helps to enhance the biodegradability of the filter segment and the aerosol-generating article as a whole.

[0048] Furthermore, while it has previously been found to be technically challenging to produce filaments or fibers containing PHAs using existing techniques and equipment, the inventors have surprisingly discovered that when PHAs are mixed in a blend as described above, filaments or fibers incorporating high levels of PHAs can be produced because this makes it easier to form filaments by spinning techniques.

[0049] In a particularly preferred embodiment, 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 contributes to improving the mechanical, thermal, and morphological properties of the polymer mixture. In particular, it has been found that the combination of PBAT and PBS provides particularly well-balanced mechanical properties, particularly in terms of tensile strength and elongation.

[0050] PHA fibers can be formed from a PHA compound alone or in combination with one or more other polymers, such as polylactic acid (PLA). Thus, PHA fibers are formed from a polymer blend comprising a PHA compound.

[0051] The PHA filter segment preferably comprises at least about 5% by weight of a PHA compound, more preferably at least about 10% by weight of a PHA compound, more preferably at least about 20% by weight of a PHA compound, more preferably at least about 30% by weight of a PHA compound, more preferably at least about 40% by weight of a PHA compound, more preferably at least about 50% by weight of a PHA compound, more preferably at least about 60% by weight of a PHA compound, more preferably at least about 70% by weight of a PHA compound, more preferably at least about 80% by weight of a PHA compound, more preferably at least about 90% by weight of a PHA compound, more preferably at least about 95% by weight of a PHA compound.

[0052] 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 phenols 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.

[0053] 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.

[0054] In certain preferred embodiments of the present invention, the PHA filter segment comprises polyethylene glycol, such as PEG 400. The combination of PHA fibers and 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 in removing phenolic compounds. The filtration capacity of filters comprising PHA fibers according to the present invention can be further optimized by incorporating compounds that specifically reduce the levels of phenolic compounds in aerosols generated by aerosol-generating substrates. This, in turn, improves the sensory characteristics of the aerosol delivered to the consumer.

[0055] In a particularly preferred embodiment, the PHA filter segment further comprises at least about 5 wt% polyethylene glycol based on the total weight of the filter material. Preferably, the filter segment comprises no more than 10 wt% polyethylene glycol based on the total weight of the filter material.

[0056] In other preferred embodiments of the present invention, the PHA filter segment further comprises a mixture of cellulose acetate and triacetin. Preferably, the mixture comprises at least 90% by weight triacetin and up to 10% by weight cellulose acetate. The mixture can be formed by adding cellulose acetate flakes to triacetin to form a solution. This solution can then be sprayed onto the PHA fibers in the PHA filter segment. This combination has been found to advantageously replicate the combined effects of triacetin and cellulose acetate fibers in the filter of conventional cigarettes.

[0057] The PHA filter segment of an aerosol-generating article according to the present invention can be modified so as to provide a desired level of resistance to draw (RTD). Due to the relatively large size of the PHA fibers, they can be arranged to provide a relatively low RTD to the PHA filter segment. Therefore, the PHA filter segment is particularly suitable for use in a filter or cigarette holder of a heated aerosol-generating article, where a relatively low RTD is generally desirable. Alternatively or in addition, the PHA filter segment may be particularly suitable for use in an aerosol-generating article for which a relatively long cigarette holder or filter is preferred because an acceptable RTD can still be provided.

[0058] Preferably, in an aerosol-generating article according to the present invention, the RTD of a 27 mm filter segment of the PHA filter segment is at least about 10 mm HO. More preferably, the RTD of a 27 mm filter segment of the PHA filter segment is at least about 12 mm HO, more preferably at least about 15 mm HO. Even more preferably, in an aerosol-generating article according to the present invention, the RTD of a 27 mm filter segment of the PHA filter segment is at least about 18 mm HO, more preferably at least about 20 mm HO. The RTD of a 27 mm filter segment of the PHA filter segment is preferably no more than about 50 mm HO, more preferably no more than 45 mm HO, more preferably no more than about 40 mm HO. For example, the RTD of a 27 mm filter segment of the PHA filter segment can 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 H2O, or about 25 mm H2O.

[0059] In certain preferred embodiments of the present invention, the PHA filter segment has an RTD of at least about 10 mm HO (based on the length of the PHA filter segment in the article). More preferably, the RTD of the PHA filter segment is at least about 15 mm HO, more preferably at least about 20 mm HO. Even more preferably, in aerosol-generating articles according to the present invention, the RTD of the PHA filter segment is at least about 25 mm HO, more preferably at least about 30 mm HO. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) is preferably no more than about 100 mm HO, more preferably no more than about 80 mm HO, more preferably no more than about 60 mm HO. For example, the RTD of the PHA filter segment can be between about 10 mm H 2 O and about 100 mm H 2 O, or between about 15 mm H 2 O and about 80 mm H 2 O, or between about 20 mm H 2 O and about 80 mm H 2 O, or between about 25 mm H 2 O and about 60 mm H 2 O, or between about 30 mm H 2 O and about 60 mm H 2 O. Such ranges may be particularly suitable for combustible smoking articles.

[0060] In other preferred embodiments of the present invention, the PHA filter segment has an RTD of at least about 10 mm HO (based on the length of the PHA filter segment in the article). More preferably, the RTD of the PHA filter segment is at least about 11 mm HO, more preferably at least about 12 mm HO. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) is preferably no more than about 25 mm HO, more preferably no more than about 20 mm HO, more preferably no more than about 15 mm HO. For example, the RTD of the PHA filter segment can be between about 10 mm HO and about 25 mm HO, or between about 11 mm HO and about 25 mm HO, or between about 12 mm HO and about 20 mm HO, or between about 12 mm HO and about 15 mm HO, or about 13 mm HO. Such ranges may be particularly suitable for heated aerosol-generating articles in which the aerosol-generating substrate is heated rather than combusted to generate the aerosol.

[0061] "Resistance to draw" is the static pressure difference across a sample when air is passed through it under steady-state conditions, where the volumetric flow rate at the outlet is 17.5 milliliters per second. The RTD of a sample can be measured using the method specified in ISO Standard 6565:2002.

[0062] It has also been found that the PHA filter segments of aerosol-generating articles according to the present invention provide good RTD stability, which means that high variability in the RTD can be advantageously avoided. For example, within 20 samples of aerosol-generating articles according to the present invention, there will typically be a standard deviation of between 2% and 10%, more preferably between 2% and 5%, relative to the target RTD.

[0063] Preferably, the PHA filter segment of the aerosol-generating article according to the present invention has an average radial hardness of at least 80%, more preferably at least 85%. Thus, the PHA filter segment is capable of providing a desired level of filter hardness, which is comparable to the hardness provided by conventional cellulose acetate tow filters. If desired, the radial hardness of the PHA filter segment can be further increased by surrounding the PHA filter segment with a rigid filter plug wrap, such as a filter plug wrap having a basis weight of at least about 80 grams per square meter (gsm), or at least about 100 gsm, or at least about 110 gsm.

[0064] As used herein, the term "radial stiffness" refers to the resistance to compression in a direction transverse to the longitudinal axis. The radial stiffness of an aerosol-generating article around a filter can be determined by applying a load to the article at a position across the filter transverse to the longitudinal axis of the article and measuring the average (mean) indentation diameter of the article. The radial stiffness is given by:

[0065]

[0066] Sets the diameter of the indentation after loading. The harder the material, the closer the hardness is to 100%.

[0067] To determine the hardness of a portion of an aerosol 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 is performed using a known DD60A densitometer device (manufactured and commercially available by Heinr. Borgwaldt GmbH, Germany) equipped with a measuring head for an aerosol-generating article, such as a cigarette, and equipped with an aerosol-generating article container.

[0068] The load is applied using two load-applying cylindrical rods that extend simultaneously across the diameter of all aerosol-generating articles. According to the standard test method for this instrument, the test should be performed so that twenty points of contact occur between the aerosol-generating articles and the load-applying cylindrical rods. In some cases, the filter to be tested may be long enough that only ten aerosol-generating articles are required to form twenty points of contact, with each smoking article contacting two load-applying rods (because they are long enough to extend between these rods). In other cases, if the filter is too short to achieve this, twenty points of contact should be formed using twenty aerosol-generating articles, with each aerosol-generating article contacting only one of the load-applying rods, as discussed further below.

[0069] Two further fixed cylindrical rods are located beneath the aerosol-generating article to support the aerosol-generating article and to counteract the loads applied by each of the load-applying cylindrical rods.

[0070] For standard operating procedures for such equipment, a total load of 2 kg 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 hardness according to the above formula. The temperature is maintained in the region of 22 degrees Celsius ± 2 degrees. The above test is known as the DD60A test. The standard way to measure the hardness of a filter tip is when the aerosol-generating article has not yet been consumed. Additional information on the measurement of the average radial hardness can be found, for example, in U.S. Published Patent Application Publication No. 2016 / 0128378.

[0071] As described above, the use of PHA fibers to prepare filter segments of aerosol-generating articles according to the present invention advantageously provides improved biodegradability compared to conventional cellulose acetate filters.

[0072] 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 ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by measuring the oxygen demand in a closed respirometer (2005)).

[0073] Under the same testing conditions, cellulose acetate filter segments exhibited a biodegradability of approximately 30%.It can therefore be seen that using PHA fibers instead of cellulose acetate fibers to form filter segments provides a significant improvement in the biodegradability of the filter segments.

[0074] The dimensions of the PHA filter segment may vary depending on the type of aerosol-generating article into which the filter segment is incorporated.

[0075] Preferably, the PHA filter segment has a length of at least about 4 mm, more preferably at least about 5 mm, more preferably at least about 7 mm, most preferably at least about 10 mm.

[0076] Preferably, the PHA filter segment has a length of less than or equal to about 30 mm, less than or equal to about 27 mm, more preferably less than or equal to about 25 mm, most preferably less than or equal to about 20 mm.

[0077] For example, the length of the PHA 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, and most preferably from about 20 mm to about 30 mm. Alternatively, in such embodiments, the length of the PHA 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 length of the PHA filter segment may be from about 4 mm to about 25 mm, and preferably from about 5 mm to about 25 mm, more preferably from about 10 mm to about 25 mm, even more preferably from about 15 mm to about 30 mm, and most preferably from about 20 mm to about 25 mm.

[0078] For embodiments of the present 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, and most preferably about 27 mm.

[0079] For alternative embodiments of the present 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 electric heating device or an integral heat source, as described in more detail below, the length of the PHA filter segment is preferably between about 5 mm and about 15 mm, more preferably between about 5 mm and about 10 mm, and most preferably about 7 mm.

[0080] The PHA 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 PHA filter segment may have an outer diameter 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 PHA filter segment has an outer diameter of 7.2 mm (with a tolerance of less than 10%).

[0081] 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 comprising PHA fibers. Thus, such a filter segment would provide a configuration similar to a conventional filter plug of cellulose acetate tow.

[0082] In an alternative embodiment, the PHA filter segment may be in the form of a hollow tube segment. A hollow tube segment has a larger exposed surface area than a cylindrical filter plug of equivalent diameter, which may further improve the biodegradation of the PHA filter segment.

[0083] The hollow tube segment 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 mm. Even more preferably, the hollow tube segment has a wall thickness of at least about 0.5 mm.

[0084] Preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.9 mm. More preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.5 mm. Even more preferably, the hollow tube segment has a wall thickness of less than or equal to about 1.2 mm. Particularly preferably, the hollow tube segment has a wall thickness of less than or equal to about 0.9 mm.

[0085] In some embodiments, the hollow tube segment can generally have a length of at least about 4 mm. Preferably, the hollow tube segment has a length of at least about 5 mm. More preferably, the hollow tube segment has a length of at least about 7 mm. Even more preferably, the hollow tube segment has a length of at least about 10 mm.

[0086] In the case 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 include between about 5% and about 15% by weight of cellulose acetate. Without wishing to be bound by theory, it is understood that a certain 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.

[0087] The filter of the aerosol generating article according to the present invention may be a single-segment filter comprising only a PHA filter segment. Alternatively, the filter of the aerosol generating article according to the present invention may further comprise one or more additional filter segments formed of a filter material, which may be arranged upstream or downstream of the PHA filter segment as described above. For example, the PHA filter segment may be combined with one or more axially aligned filter plugs formed of a fibrous filter material, which may or may not comprise PHA fibers. Alternatively or in addition, the PHA filter segment may be combined with one or more tubular elements, such as hollow acetate tubes or cardboard tubes. For example, in certain embodiments, the filter may comprise 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.

[0088] Preferably, the additional filter segments are formed from a material other than cellulose acetate. Particularly preferably, the additional filter segments comprise PHA fibers, which may optionally be held in the desired shape with the aid of a suitable binder, such as PVA. Preferably, each of the additional filter segments comprises at least about 25% by weight of a PHA compound, more preferably at least about 50% by weight of a PHA compound.

[0089] The filter of the aerosol-generating article according to the present invention may optionally contain a flavoring agent. The flavoring agent may be incorporated using a variety of different means known to the skilled person. For example, the flavoring agent may be incorporated in the form of a capsule that may be provided in the PHA filter segment or in an additional filter segment.

[0090] Preferably, the filter of the aerosol-generating article according to the present invention comprises a capsule located within a 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. As discussed above, the use of 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 space available between individual fibers compared to filters formed from fibers with lower dpf values. Therefore, PHA filter segments formed from PHA fibers having a dpf in this range are particularly suitable for incorporation of capsules. The capsule can be easily incorporated into the PHA filter segment during manufacturing. In addition, the capsule will be effectively maintained in the desired axial position within the PHA filter segment.

[0091] The filter of an aerosol-generating article according to the present invention is preferably surrounded by an outer wrapping material, such as a tipping wrapper that surrounds the filter segment, the downstream end of the aerosol-generating substrate, and any additional components that may be provided therebetween. As described in WO-A-2017 / 162838, the tipping wrapper may include a removable tipping wrapper portion. This enables at least a portion of the tipping wrapper to be removed before discarding the aerosol-generating article. Removal of the tipping wrapper exposes the underlying filter segment and may therefore advantageously accelerate the biodegradation rate of the filter material.

[0092] As defined above, aerosol-generating articles according to the invention further comprise 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.

[0093] The aerosol-generating substrate may have a length between about 5 mm and about 100 mm. Preferably, the aerosol-generating substrate has a length of at least about 5 mm, more preferably at least about 7 mm. In addition to or as an alternative, 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 a particularly preferred embodiment, 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.

[0094] In certain embodiments, an aerosol-generating article according to the present invention is a filter cigarette or other combustible smoking article, wherein the aerosol-generating substrate comprises a tobacco material that is combusted to form an aerosol. In any such embodiment, the aerosol-generating substrate may comprise a tobacco rod. The tobacco rod may comprise one or more of cut filler and reconstituted tobacco.

[0095] 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 between about 10 mm and about 100 mm, more preferably having a total length between about 30 mm and about 70 mm. The tobacco rod may comprise one or more of cut filler and reconstituted tobacco.

[0096] As discussed above, filters of the present invention comprising PHA segments have specific applications in heated aerosol generating articles, in which tobacco material is heated rather than burned to form an aerosol. This is at least in part due to the possibility of providing a relatively low level of RTD for PHA segments with a limited dpf range as described above. In one type of heated aerosol generating article, the tobacco material is heated by one or more electric heating elements to produce an aerosol. In another type of heated aerosol generating article, an aerosol is generated by transferring heat from a combustible or chemical heat source to a physically independent tobacco material, which may be located in, around or downstream of the heat source. The present invention also encompasses aerosol generating articles in which a nicotine-containing aerosol is generated by a tobacco material, a tobacco extract or other nicotine source without burning, and in some cases without heating, such as by heating by a chemical reaction.

[0097] For embodiments in which the aerosol-generating article is in the form of a heated aerosol-generating article in which an aerosol-generating substrate is intended to be heated to form an aerosol, the aerosol-generating substrate preferably has a length between about 5 mm and about 40 mm, more preferably between about 9 mm and about 15 mm.

[0098] For such embodiments in which the aerosol generating article is a form of heated aerosol generating article, the aerosol generating substrate is preferably formed by a homogenized tobacco material, which is formed by the agglomeration of tobacco particles. The aerosol generating substrate can comprise one or more aggregated sheets of homogenized tobacco material. The one or more sheets can be textured. As used herein, the term "textured sheet" represents a sheet that is curled, embossed, gravure, perforated or otherwise deformed. Alternatively, the aerosol generating substrate can comprise a plurality of strips or strands of homogenized tobacco material. These strips or strands can be aligned substantially with each other in the longitudinal direction, or can be randomly oriented.

[0099] The homogenized tobacco material used in the aerosol-generating substrate may have a tobacco content of at least about 40 weight percent on a dry weight basis, more preferably at least about 60 weight percent on a dry weight basis, more preferably at least about 70 weight percent on a dry weight basis, and most preferably at least about 90 weight percent on a dry weight basis.

[0100] The homogenized tobacco material used in the aerosol-generating substrate can contain one or more intrinsic binders (i.e., tobacco endogenous binders), one or more non-intrinsic binders (i.e., tobacco exogenous binders), or combinations thereof to help tobacco particles coalesce. Alternatively or in addition, the homogenized tobacco material used in the aerosol-generating substrate can contain other additives, including but not limited to tobacco fibers and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavoring agents, fillers, aqueous solvents and non-aqueous solvents, and combinations thereof.

[0101] Suitable non-inherent binders for inclusion in the homogenized tobacco material for use in an aerosol-generating substrate 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; cellulosic 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.

[0102] Suitable non-tobacco fibers for inclusion in the homogenized tobacco material for use in an aerosol-generating substrate 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 homogenized tobacco material for use in an aerosol-generating substrate, the non-tobacco fibers may be treated by suitable processes known in the art, including, but not limited to, mechanical pulping, refining, chemical pulping, bleaching, sulfate pulping, and combinations thereof.

[0103] Aerosol-generating substrates for heated aerosol-generating articles typically include an "aerosol-forming agent," that is, a compound or mixture of compounds that promotes the formation of an aerosol during use and preferably substantially resists thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-forming agents include: polyols, such as propylene glycol, triethylene glycol, 1,3-butylene glycol, and glycerol; esters of polyols, such as glycerol monoacetate, glycerol diacetate, or glycerol triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol-forming agents are polyols or mixtures thereof, such as propylene glycol, triethylene glycol, 1,3-butylene glycol, and most preferably glycerol.

[0104] Preferably, the aerosol-generating substrate comprises at least 10% by weight of an aerosol-forming agent, more preferably at least 12% by weight of an aerosol-forming agent, more preferably at least about 15% by weight of an aerosol-forming agent. Alternatively or in addition, the aerosol-generating substrate preferably comprises no more than 30% by weight of an aerosol-forming agent, more preferably no more than about 25% by weight of an aerosol-forming agent, more preferably no more than about 20% by weight of an aerosol-forming agent. For example, the aerosol-generating substrate may comprise between about 10% and about 30% by weight of an aerosol-forming agent, or between about 12% and about 25% by weight of an aerosol-forming agent, or between about 15% and about 20% by weight of an aerosol-forming agent. In a particularly preferred embodiment, the aerosol-generating substrate comprises about 18% by weight of an aerosol-forming agent.

[0105] Aerosol-generating articles according to the present invention may further comprise one or more additional components interposed between the filter and the aerosol-generating substrate. For example, the aerosol-generating article may further comprise one or more of the following: a support element, an aerosol-cooling element, and a transfer element. The construction of such components will be known to the skilled person.

[0106] For example, in certain preferred embodiments of the present invention, the aerosol-generating article is arranged in a linear order to include: an 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 the downstream end of the filter.

[0107] In other preferred embodiments of the present invention, the aerosol-generating article comprises, arranged in a linear order, an aerosol-generating substrate, a transfer element, an aerosol-cooling element, a spacing element, and a mouthpiece filter.

[0108] In certain preferred embodiments of the present invention, the aerosol-generating article further comprises a combustible heat source at the 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 include a carbon-containing heat source at the upstream end for heating the aerosol-generating substrate to generate an aerosol during use. Suitable carbon-containing heat sources will be known to the skilled person. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] The present invention will now be further described with reference to the accompanying drawings, in which:

[0110] Figure 1 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a first embodiment of the invention for use with an aerosol-generating device comprising a heater element;

[0111] Figure 2shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a second embodiment of the invention, the aerosol-generating article comprising an integral heat source; and

[0112] Figure 3 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a third embodiment of the invention; and

[0113] Figure 4 shows a schematic longitudinal cross-sectional view of an aerosol generating system comprising an electrically operated aerosol generating device and Figure 1 The aerosol-generating article shown. DETAILED DESCRIPTION

[0114] Figure 1 The illustrated aerosol-generating article 10 comprises a rod of an 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 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 at the end of the article opposite the mouth end 22. Figure 1 The aerosol-generating article 10 shown in is particularly suitable for use with an electrically operated aerosol-generating device that includes a heater for heating a strip of aerosol-generating substrate.

[0115] In use, air is drawn by a user through the aerosol-generating article from the distal end 24 to the mouth end 22. 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. 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.

[0116] The aerosol-generating substrate 12 is located at the extreme distal or upstream end of the aerosol-generating article 10. Figure 1 In the illustrated embodiment, the aerosol-generating substrate 12 comprises a gathered sheet of crimped homogenised tobacco material surrounded by a wrapper. The crimped sheet of homogenised tobacco material comprises a glyceride as an aerosol-forming agent.

[0117] The support element 14 is located immediately downstream of the aerosol-generating substrate 12 and is adjacent to the aerosol-generating substrate 12. Figure 1In the illustrated embodiment, 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 so that it can be penetrated by the heating element of the aerosol-generating device. In practice, when the heating element of the aerosol-generating device is inserted into the aerosol-generating substrate 12, the support element 14 serves to prevent the aerosol-generating substrate 16 from being pushed downstream within the aerosol-generating article 10 toward the aerosol-cooling element 16. The support element 14 also serves as a spacer to separate the aerosol-cooling element 16 of the aerosol-generating article 10 from the aerosol-generating substrate 12.

[0118] The aerosol-cooling element 16 is positioned immediately downstream of the support element 14 and abuts the support element 16. In use, volatile material released from the aerosol-generating substrate 12 passes along the aerosol-cooling element 16 towards the mouth end 22 of the aerosol-generating article 10. The volatile material may cool within the aerosol-cooling element 16 to form an aerosol that is inhaled by the user. Figure 1 In the illustrated embodiment, the aerosol-cooling element comprises a tubular element 20. The rolled and gathered polylactic acid sheet defines a plurality of longitudinal channels extending along the length of the aerosol-cooling element 40.

[0119] The filter segment 18 is positioned immediately downstream of the aerosol-cooling element 16 and abuts the aerosol-cooling element 16. Figure 1 In the embodiment shown, the filter segment 18 comprises a single cylindrical filter rod of fibrous filter material, which is formed by a plurality of PHA fibers having a single filament denier 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 each other along the length of the filter segment. The surface area of ​​the PHA fibers corresponds to about 0.1 square meters per gram. The PHA fibers have been formed by a melt spinning process and are curled. The filter rod of the fibrous filter material is surrounded by a filter rod wrapper (not shown).

[0120] Figure 2 The aerosol-generating article 100 shown comprises a combustible heat source 112, a rod of aerosol-generating substrate 114, a transfer element 116, an aerosol-cooling element 118, a spacing element 120, and a mouthpiece filter segment 122. These elements are arranged in sequence and coaxially aligned, and are surrounded by a substrate wrap to form the aerosol-generating article 100.

[0121] The combustible heat source 112 comprises a substantially circular cylindrical body of carbonaceous material having a length of approximately 10 mm. The combustible heat source 112 is a plugged heat source. In other words, the combustible heat source 112 does not include any air passages extending therethrough.

[0122] 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.

[0123] A non-combustible, substantially air-impermeable first barrier 128 is disposed 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 an aluminum foil disk. 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 side of the combustible heat source 112 to the distal side of the aerosol-generating substrate 114.

[0124] The heat-conductive element 130 surrounds the proximal portion of the combustible heat source 112 and the distal portion of the aerosol-forming substrate 114. The heat-conductive element 130 comprises an aluminum foil tube. The heat-conductive 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-forming substrate 114.

[0125] The cigarette holder filter 122 comprises a single cylindrical filter plug 126 of fibrous filter material, which is formed by a plurality of PHA fibers having a single filament denier 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 each other along the length of the filter segment. The total surface area of ​​the PHA fibers corresponds to about 0.1 square meters per gram. The PHA fibers have been formed by a melt spinning process and are curled. The filter plug of fibrous filter material is surrounded by a filter plug wrap (not shown).

[0126] Figure 3 The illustrated aerosol-generating article 310 is a combustible smoking article comprising an aerosol-generating substrate 312 and a filter 314 arranged coaxially aligned with each other. 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.

[0127] Filter 314 comprises a single cylindrical filter plug 318 of fibrous filter material, and this fibrous filter material is formed by the PHA fiber of about 8.0 and total denier of about 15,000 of monofilament denier.The PHA fiber has a circular cross-sectional shape and is substantially longitudinally aligned with each other along the length of the filter segment.The total surface area of ​​the PHA fiber corresponds to about 0.1 square meter every gram.The PHA fiber has been formed by melt spinning and is curled.The filter plug of fibrous filter material is surrounded by filter plug wrapper (not shown).

[0128] Figure 4A portion of an electrically operated aerosol generating system 200 is shown, which utilizes heater blades 210 to heat Figure 1 The aerosol-generating article 10 is shown with a stem 12 of an aerosol-generating substrate. A heater blade 210 is mounted within the 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 shown. Figure 4 As shown by the arrow in FIG. The aerosol generating device 212 includes Figure 4 The power supply and electronics are shown in FIG.

Claims

1. A heated aerosol-generating article comprising: aerosol-generating substrate; A filter axially aligned with the aerosol-generating substrate, the filter comprising a filter segment of filter material formed from a plurality of fibers comprising a polyhydroxyalkanoate compound, wherein the fibers have a denier per filament (dpf) between 5.0 and 12.0, wherein the filter segment comprises at least 20% by weight of the polyhydroxyalkanoate compound, and wherein the filter segment has a resistance to draw (RTD) between 10 mm H2O and 25 mm H2O.

2. A heated 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 m2 / g and 0.12 m2 / g.

3. A heated 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 segment of between 0.15 m2 / g and 0.21 m2 / g.

4. The heated aerosol-generating article of claim 1 or 2, wherein the total denier of the fibers comprising the polyhydroxyalkanoate compound is between 15,000 and 30,000.

5. The heated aerosol-generating article according to claim 1 or 2, wherein the filter material further comprises a plurality of fibers of at least one additional biodegradable polymer.

6. The heated aerosol-generating article of claim 1 or 2, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound further comprises at least 5 wt% polyethylene glycol.

7. The heated aerosol-generating article of claim 1 or 2, wherein a filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound has an average radial hardness of at least 80%.

8. The heated aerosol-generating article of claim 1 or 2, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound is surrounded by a wrapping material having a basis weight of at least 100 grams per square meter (gsm).

9. A heated aerosol-generating article according to claim 1 or 2, wherein the filter segment comprising the plurality of fibers comprising the polyhydroxyalkanoate compound is in the form of a hollow tubular element.

10. The heated aerosol-generating article according to claim 1 or 2, wherein the aerosol-generating substrate has a length of between 5 mm and 15 mm.

11. The heated aerosol-generating article of claim 1 or 2, wherein the filter segment further comprises capsules within the plurality of fibers comprising the polyhydroxyalkanoate compound.

Images