CN114760867A - Aerosol-generating article filter with novel filter material - Google Patents

Abstract

There is provided an aerosol-generating article (10) (100) (310) comprising: an aerosol-generating substrate (12) (114) (312); and a filter (18) (122) (314) in axial alignment 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 fibres comprising a polyhydroxyalkanoate compound, wherein the fibres provide a total external surface area of from 0.12 m/g to 0.28 m/g. The at least one filter section comprises at least 20% by weight of polyhydroxyalkanoate compound.

Description

Aerosol-generating article filter with novel filter material

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

Conventional aerosol-generating articles, such as filter cigarettes, typically include a cylindrical rod of tobacco cut filler surrounded by a paper wrapper and axially aligned, most often in end-to-end relationship, with the wrapped tobacco rod. Cylindrical filter. Cylindrical filters typically include one or more filter segments of fibrous filter material, such as cellulose acetate tow, defined by a paper filter segment package. Conventionally, the wrapped tobacco rod and filter are joined by a tipping wrapper, typically made of an opaque paper material that defines the entire length of the filter and the wrapped tobacco rod the adjacent part.

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 transferring heat from a heat source to a physically separate aerosol-generating substrate or material.

For example, aerosol-generating articles have been proposed in which an aerosol is generated by electrical heating of an aerosol-generating substrate. Numerous prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by transferring heat from one or more electrical 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 transferring heat 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 the aerosol-generating substrate, within the aerosol-generating substrate, around the aerosol-generating substrate, 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 the air drawn through the aerosol-generating article. When the released compound cools, the compound condenses to form an aerosol.

Typically, an aerosol-generating article of this type 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 at a location between the aerosol-generating substrate and the mouth end of the article to impart structural strength to the article.

The most commonly used filter material, cellulose acetate, provides relatively high filtration efficiencies and cellulose acetate tow filters provide effective filtration of mainstream smoke generated by the aerosol-generating matrix. However, cellulose acetate has also been found to provide relatively high levels of water absorption and capture from mainstream smoke. Mainstream smoke delivered to consumers thus has significantly reduced moisture content and may be considered undesirably "dry" in some circumstances. This can have a detrimental effect on the overall smoking experience.

Cellulose acetate and many other commonly used filter materials are not highly biodegradable. However, alternative dispersible or degradable materials often fail to provide acceptable filtration efficiency and consumer smoking experience. Furthermore, many of the known dispersible and degradable materials are not suitable for existing manufacturing processes and require significant modifications to existing methods and equipment to make their use commercially viable.

It would be desirable to provide a new and improved aerosol-generating article that has enhanced biodegradability compared to known articles comprising conventional filter materials such as cellulose acetate. It is particularly desirable to provide such a novel aerosol-generating article that provides consumers with an improved smoking experience. For example, it would be desirable to provide an aerosol-generating article that reduces the "dry" smoke effect commonly found in articles comprising cellulose acetate as filter material, as described above. It would also be desirable to provide an aerosol-generating article in which the resistance to suction (RTD) of the filter material segment can be adjusted in order to achieve an acceptable RTD for the article as a whole. Furthermore, it would be desirable to provide an aerosol-generating article that can be efficiently produced by an automated high-speed manufacturing process without requiring significant modifications to existing equipment.

The present disclosure relates to an aerosol-generating article for generating a respirable aerosol upon heating or combustion. The aerosol-generating article may include a strip of aerosol-generating substrate and a filter segment axially aligned with the strip. The filter segment may include a filter material formed from a plurality of fibers comprising a polyhydroxyalkanoate (PHA) compound. Fibers comprising the PHA compound can provide a total external surface area within the filter section of 0.12 square meters/gram to about 0.28 square meters/gram.

Furthermore, 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 comprising a polyhydroxyalkanoate (PHA) compound. Fibers comprising the PHA compound can provide a total external surface area within the filter section of 0.12 square meters/gram to about 0.28 square meters/gram.

According to the present invention, there is provided an aerosol-generating article 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 The material includes a plurality of fibers comprising a polyhydroxyalkanoate (PHA) compound. The fibers comprising the polyhydroxyalkanoate compound provide a total external surface area within the filter section of about 0.12 square meters/gram to about 0.28 square meters/gram.

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 comprising the polyhydroxyalkanoate compound provide a total external surface area within the filter section of about 0.12 square meters/gram to about 0.28 square meters/gram.

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

Conventional cigarettes are lit when a user applies a flame to one end of the cigarette and draws air through the other end. The local heat provided by the flame and 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 flavor-generating substrate, such as a tobacco-based substrate or a substrate containing an aerosol former and flavor. 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 present invention can be used as a filter for a mouthpiece in a heated aerosol-generating article in which an aerosol-generating substrate is heated to generate an aerosol without burning the substrate. However, the filters of the present invention are also suitable for use as filters for combustible smoking articles in which the aerosol-generating substrate is combusted during use to generate smoke.

As used herein, the term "aerosol-generating substrate" describes a substrate capable of releasing volatile compounds upon heating (including combustion) that can form an aerosol. Aerosols generated by aerosol-generating substrates may or may not be visible and may include vapors (eg, fine particulate matter in a gaseous state, which are typically liquid or solid at room temperature) as well as liquid droplets of gases and condensed vapors. As used herein, the term "aerosol" encompasses both the aerosol produced upon heating of the substrate in a heated aerosol-generating article and the smoke produced upon combustion of the substrate in a combustible smoking article.

As defined above, the present invention provides a filter for an aerosol-generating article, the filter comprising at least one filter segment comprising a filter material formed from a plurality of fibers, the plurality of The root fibers contained the PHA compound and had a total external surface area within the filter section of 0.12 square meters/gram to 0.28 square meters/gram. 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 polyhydroxyesters of 3-, 4-, 5-, and 6-hydroxyalkanoic acids that are produced by various bacterial species under nutrient-limiting conditions with excess carbon and are present in bacterial cells as discrete cytoplasmic inclusions middle. 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-PHA; 3 to 5 carbon atoms), medium chain length PHAs (mcl-PHA; 6 to 14 carbon atoms) or long chain Length PHA (lcl-PHA; 15 or more carbon atoms).

PHA fibers are less hydrophilic than fibers of the same weight as other filter materials such as cellulose acetate. Accordingly, in the aerosol-generating articles of the present invention, it has been found that the filter segment has a significantly reduced tendency to absorb water/vapor from aerosols generated by the aerosol-generating substrate during use. As a result, the water content in the aerosol can advantageously be kept at a high level. This directly addresses the "dry smoke" problem often encountered with conventional smoking articles and provides the consumer with an improved smoking experience.

The articles according to the present invention are overall more biodegradable due to the much higher level of biodegradability of PHA fibers compared to fibers of other filter materials such as cellulose acetate. At the same time, the aerosol-generating article according to the present invention also provides an improved sustainability of the production process since the PHA fibers are obtained by a natural fermentation process.

It has also been found that filters formed with PHA fibers provide good filter stiffness, which can be further enhanced by wrapping the filter segments with rigid filter segments to define filter segments.

According to the present invention, the PHA filter segments are formed from PHA fibers arranged to provide a total external surface area of 0.12 square meters/gram to 0.28 square meters/gram.

The total external surface area of the PHA fibers in the PHA filter section is therefore at least about 0.12 square meters per gram. Preferably, the total external surface area of the PHA fibers in the PHA filter section is at least about 0.13 square meters/gram, more preferably at least about 0.14 square meters/gram, more preferably at least about 0.15 square meters/gram.

Additionally, the total external surface area of the PHA fibers in the PHA filter section is not greater than about 0.28 square meters per gram. Preferably, the total external surface area of the PHA fibers in the PHA filter section is not greater than about 0.27 square meters/gram, more preferably not greater than about 0.26 square meters/gram, and more preferably not greater than about 0.25 square meters/gram.

This limited range of total external surface area has been found to provide the best balance between controlling and reducing the water absorption level of the PHA filter section while maintaining acceptable resistance to draw (RTD) levels for the PHA filter section. The PHA filter segment of the present invention is therefore highly versatile in that it can be adapted for use in both combustible smoking articles and heated aerosol-generating articles. This enables the use of the same manufacturing equipment and techniques for the manufacture of filter segments for various types of aerosol-generating articles, as the same filter material is suitable for use in multiple applications. Thus, the manufacture of filter segments can be carried out in a more efficient manner.

The RTD level provided by the PHA filter stage can be sufficiently low that the PHA filter stage can be used in heated aerosol-generating articles where relatively low RTD levels are preferred. The level of RTD is also low enough that relatively long PHA filter segments can be provided without adversely affecting the overall RTD, for example in combustible smoking articles.

Most of the outer surfaces of the PHA fibers within the PHA filter section are generally exposed and thus will come into contact with aerosols during use as aerosols generated by the aerosol-generating matrix pass through the PHA filter section. Therefore, the total external surface area of the PHA fibers will affect the filtration of the aerosol as it passes through the PHA filter section. In turn, the organoleptic properties of the aerosol can thus be controlled by varying the total external surface area of the PHA fibers.

For example, by increasing the total external surface area within defined limits, it may be possible to control the absorption and retention of certain aerosol components such as water. This can advantageously improve the organoleptic properties of the aerosol delivered from the aerosol-generating substrate to the consumer. As discussed above, selecting the total external surface area of the PHA fibers within a defined range enables the provision of a PHA filter segment that can reduce the water absorption level of the filter segment compared to the corresponding cellulose acetate tow segment. This may be beneficial for combustible smoking articles where it is desired to reduce water absorption from mainstream smoke to reduce the "dry smoke" effect. It may also be beneficial for heated aerosol-generating articles in which the aerosol-generating substrate is heated to generate the aerosol during use. For example, where the aerosol-generating substrate is heated at relatively low temperatures, or where high water content aerosols are desired, it may be advantageous to provide reduced levels of water adsorption by the PHA filter stage.

Advantageously, the level of water absorption provided by the PHA filter segments of the present invention is such that an acceptable smoking experience can be provided for most different types of aerosol-generating articles.

The total external surface area of the PHA fibers within the PHA filter section can be varied within defined ranges by controlling at least one of the cross-sectional size, cross-sectional shape, and number of the PHA fibers.

The PHA fibers can have a substantially circular cross-section. In such embodiments, the total external surface area of the PHA fibers within the filter section is preferably between about 0.12 square meters/gram and about 0.16 square meters/gram.

PHA fibers can have a Y-shaped cross-section. In such embodiments, the total external surface area of the PHA fibers within the filter section is preferably between about 0.21 square meters/gram and about 0.28 square meters/gram.

Preferably, the PHA fibers have a denier per filament (dpf) of from about 3.2 to about 5.0. Denier per filament, which corresponds to the average denier of an individual PHA fiber within a filter, is the weight in grams of a single fiber or filament having a length of 9000 meters. In the present invention, the value of dpf thus 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.

The denier per filament (dpf) of the PHA fibers is therefore preferably at least about 3.2. Preferably, the dpf is at least about 3.3, more preferably at least about 3.4, more preferably at least about 3.5, more preferably at least about 3.6, more preferably at least about 3.7.

The denier per filament (dpf) of the PHA fibers is preferably no greater than about 5.0. Preferably, the dpf is no greater than about 4.9, more preferably no greater than about 4.8, more preferably no greater than about 4.7, more preferably no greater than about 4.6, more preferably no greater than about 4.5.

In some embodiments, the denier per filament may be between about 3.3 and about 4.9, or between about 3.4 and about 4.8, or between about 3.5 and about 4.7, or between about 3.6 and about 4.6, or between about 3.7 and about 4.5.

In other embodiments, the denier per filament may be between about 3.2 and about 4.2, or between about 3.2 and about 4.0, or between about 3.2 and about 3.8, or between about 3.2 and about 3.6, or about 3.4.

In other embodiments, the denier per filament may be between about 4.0 and about 5.0, or between about 4.2 and about 5.0, or between about 4.4 and about 5.0.

Preferably, the total denier of the filter material comprising PHA fibers is between about 20,000 and about 50,000, more preferably between about 25,000 and about 40,000, and more preferably between about 30,000 and about 40,000. The "total denier" of the filter material defines the 9000 meters of total weight, in grams, of the combined fibers that form the filter material. The total denier of the filter segment thus corresponds to the denier per filament multiplied by the total number of fibers in the filter segment.

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

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 PHA fibers, more preferably at least about 90 wt% PHA fibers, more preferably at least about 95 wt% PHA fibers.

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.

The PHA filter segment is thus formed from a relatively high content of PHA fibers. This provides for enhanced biodegradability of the filter and aerosol-generating article as a whole. As noted above, it has previously been found to be technically challenging to form filter segments with high proportions of degradable polymers that provide acceptable filtration properties. However, the present inventors have surprisingly found that filter segments incorporating relatively high PHA fiber content can be produced that provide desired levels of filtration properties such as filtration efficiency and suction resistance.

The PHA fibers of the filter according to the present invention can be produced using any suitable method. Suitable techniques for making 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 often considered to be the most economical spinning process because no solvent recovery or evaporation is required, in contrast to solution spinning. Furthermore, the spinning rates using melt spinning are generally quite high, which is advantageous in terms of overall productivity and manufacturing efficiency.

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

The PHA filter segment may be formed from fibrous filter material formed from PHA fibers only. However, in certain preferred embodiments of the present invention, the PHA fibers may be combined with a plurality of fibers of additional biodegradable polymers 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 Esters (PBAT), Thermoplastic Starch and Thermoplastic Starch Blends (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 discovered that the inclusion of one or more of these ingredients in the blend of fibrous materials from which the filter segment is formed also helps to enhance the overall biodegradability of the filter segment and aerosol-generating article .

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 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 discovered that the inclusion of one or more of these ingredients in the blend of fibrous materials from which the filter segment is formed also helps to enhance the overall biodegradability of the filter segment and aerosol-generating article .

Additionally, while it has previously been found to be technically challenging to manufacture PHA-containing filaments or fibers using existing technology and equipment, the inventors have surprisingly discovered that when PHA is combined 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 discovered that the use of one or more of these selected biodegradable polymers will help to improve the mechanical, thermal and morphological properties of the polymer mixture. In particular, the combined use of PBAT and PBS has been found to provide particularly well-balanced mechanical properties, especially in terms of tensile strength and elongation.

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

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

The PHA filter section of the aerosol-generating article according to the present invention preferably further comprises additives for reducing certain smoke constituents in the aerosol generated by the aerosol-generating substrate. For example, the PHA filter section preferably also contains additives for reducing phenol and phenol derivatives. Suitable additives will be known to the skilled person and include, but are not limited to, polyethylene glycol (PEG), triacetin, triethyl citrate, cellulose acetate flakes, or combinations thereof.

Preferably, the filter segment comprises from about 3% to about 15% by weight of the additive, more preferably from about 5% to about 9% by weight of the additive.

In certain preferred embodiments of the present invention, the PHA filter segment comprises polyethylene glycol, such as PEG 400. The combination of PHA fibers with additives such as PEG for reducing phenolic compounds from aerosols generated from aerosol-generating matrices has been found to be particularly effective. PHA fibers generally provide good filtration efficiency against undesired flue gas components, but are less effective at removing phenolic compounds. The filtration capacity of filters comprising PHA fibers according to the present invention can be further optimized by introducing compounds that will specifically reduce the level of phenolic compounds in the aerosols generated by the aerosol-generating substrate. This in turn will improve the organoleptic properties of the aerosol delivered to the consumer.

In particularly preferred embodiments, 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 contains no more than 10% by weight polyethylene glycol based on the total weight of the filter material.

In other preferred embodiments of the present invention, the PHA filter section further comprises a mixture of cellulose acetate and triacetin. Preferably, the mixture comprises at least 90% by weight triacetin and at most 10% by weight cellulose acetate. The mixture can 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 section. This combination has been found to advantageously replicate the combined effect of triacetin and cellulose acetate fibers in conventional cigarette filters.

As noted above, it has been found that PHA fibers absorb less water than an equivalent amount of cellulose acetate fibers from an aerosol generated from an aerosol-generating matrix due to their lower affinity for water. As demonstrated in the Examples below, the amount of water absorbed by the PHA filter segment was significantly lower than that of a comparative filter segment formed from an equal weight of cellulose acetate fibers.

For example, when exposed to water in liquid form, the PHA filter segments of the present invention preferably absorb less than half the amount of water that a corresponding filter segment formed of cellulose acetate fibers would absorb under the same conditions.

Compared to cellulose acetate, the reduced water absorption of PHA fibers in the filters of the present invention results in higher water content in the aerosol delivered from the aerosol-generating article during use.

For example, a combustible smoking article comprising a filter with PHA fibers according to the present invention collects an amount of water in the aerosol during smoking under ISO conditions than a corresponding combustible smoking article having a filter segment of cellulose acetate tow under the same conditions The amount of water in the aerosol collected during puffing is at least 10% higher and preferably at least 15% higher.

Aerosol-generating articles comprising filters comprising PHA filter segments are thus able to deliver aerosols with higher moisture levels, which are more sensory acceptable to consumers. In particular, the "dry smoke" effect that may be experienced during smoking of aerosol-generating articles with conventional cellulose acetate filters can be advantageously reduced.

The PHA filter section of the aerosol-generating article according to the present invention can advantageously be adjusted to provide a desired level of resistance to draw (RTD). For some aerosol-generating articles, such as heated aerosol-generating articles having an aerosol-generating substrate that is heated rather than combusted to generate the aerosol, it may be desirable to provide a relatively low RTD for the PHA filter section. This may be the case when it is desired to provide low filtration efficiency. Alternatively, where a relatively long filter or mouthpiece is required, eg, if the aerosol-generating substrate is relatively short, a low RTD may be required. For example, a low RTD can be achieved by using PHA fibers with dpf values within the upper portion of a defined range, which are relatively large in size.

For alternative aerosol-generating articles, such as combustible articles, it may be more preferable to provide the PHA filter segment with a higher RTD to increase filtration efficiency.

Preferably, in an aerosol-generating article according to the present invention, the RTD of the PHA filter segment is at least about 30 mm _H2O column for a 27 mm filter segment. More preferably, for a 27 mm filter segment, the RTD of the PHA filter segment is at least about 35 mm _H2O column, more preferably at least about 40 mm _H2O column. Even more preferably, in an aerosol-generating article according to the present invention, the RTD of the PHA filter segment is at least about 45 mm _H2O column, more preferably at least about 50 mm _H2O for a 27 mm filter segment column. For a 27 mm filter section, the RTD of the PHA filter section is preferably no more than about 150 mm _H2O column, more preferably no more than 125 mm _H2O column, more preferably no more than about 100 mm _H2O column. For example, for a 27 mm filter segment, the RTD of the PHA filter segment can be between about 30 mm _H2O column to about 150 mm _H2O column, or between about 35 mm _H2O column to about 150 mm Between _H2O columns, or between about 40 mm _H2O columns and about 125 mm _H2O columns, or between about 45 mm _H2O columns and about 100 mm _H2O columns, or between about 45 mm H2O columns and about 100 mm H2O columns Between 50 mm _H2O column to about 100 mm _H2O column.

In certain preferred embodiments of the present invention, the PHA filter segment has an RTD (based on the length of the PHA filter segment in the article) of at least about 60 mm of the _H2O column. More preferably, the RTD of the PHA filter segment is at least about 65 mm _H2O column, more preferably at least about 70 mm _H2O column. Even more preferably, in an aerosol-generating article according to the present invention, the RTD of the PHA filter segment is at least about 75 mm _H2O column, more preferably at least about 80 mm _H2O column. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) preferably does not exceed about 120 mm _H2O column, more preferably does not exceed about 110 mm _H2O column, more preferably does not exceed about 100 mm _H2O column column. For example, the RTD of the PHA filter segment can be between about 60 mm _H2O column to about 120 mm _H2O column, or between about 65 mm _H2O column and about 120 mm _H2O column, or at Between about 70 mm _H2O column and about 110 mm _H2O column, or between about 75 mm _H2O column and about 110 mm _H2O column, or between about 80 mm _H2O column and about 100 mm H2O column between millimeters of _H2O columns, or about 90 millimeters of _H2O columns. Such ranges may be particularly suitable for combustible smoking articles.

In other preferred embodiments of the present invention, the PHA filter segment has an RTD (based on the length of the PHA filter segment in the article) of at least about 10 mm of the _H2O column. More preferably, the RTD of the PHA filter segment is at least about 12 mm _H2O column, more preferably at least about 15 mm _H2O column. Even more preferably, in an aerosol-generating article according to the present invention, the RTD of the PHA filter segment is at least about 18 mm _H2O column, more preferably at least about 20 mm _H2O column. The RTD of the PHA filter segment (based on the length of the PHA filter segment in the article) preferably does not exceed about 40 mm _H2O column, more preferably does not exceed about 35 mm _H2O column, more preferably does not exceed about 30 mm _H2O column column. For example, the RTD of the PHA filter segment can be between about 10 mm _H2O column and about 40 mm _H2O column, or between about 12 mm _H2O column and about 40 mm _H2O column, or at Between about 15 mm _H2O column and about 35 mm _H2O column, or between about 20 mm _H2O column and about 30 mm _H2O column, or about 27 mm _H2O column. Such ranges may be particularly suitable for heated aerosol-generating articles in which the aerosol-generating substrate is heated rather than burned to generate the aerosol.

"Suction resistance" refers to the static pressure difference between the two ends of the sample as the airflow traverses the sample under steady conditions with a volume flow rate of 17.5 ml/sec at the output. The RTD of a sample can be measured using the method set forth in ISO Standard 6565:2002.

It has also been found that the PHA filter section of the aerosol-generating article according to the present invention provides good stability in terms of RTD, which means that high variability in RTD can be advantageously avoided. For example, within a sample of 20 aerosol-generating articles according to the present invention, the standard deviation from the target RTD is typically between 2% and 10%, more preferably between 2% and 5%.

Preferably, the PHA filter segment of the aerosol-generating article according to the present invention has an average radial stiffness of at least 80%, more preferably at least 85%. The PHA filter segment is thus able to provide a desired level of filter stiffness that is comparable to that provided by conventional cellulose acetate tow filters. If desired, the radial stiffness of the PHA filter segment can be further increased by defining the PHA filter segment with a rigid filter segment package, eg, having a basis weight of at least about 80 grams per square meter (gsm), or at least about 100 gsm, Or at least about 110gsm filter segment packs.

As used herein, the term "radial stiffness" refers to 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 location across the filter transverse to the longitudinal axis of the article, and measuring the average (mean) value of the article. ) indentation diameter. The radial hardness is given by:

where D _S is the original (non-recessed) diameter and D _d is the recessed diameter after applying the set load for the set duration. The harder the material, the closer the hardness is to 100%.

In order to determine the hardness of a portion of an aerosol-generating article, such as a filter, the aerosol-generating articles should be aligned in parallel in a plane, and the same portion of each aerosol-generating article to be tested should be subjected to setting for a set duration load. This test is performed using the known DD60A densitometer device (manufactured by Heinr. Borgwaldt GmbH, Germany and commercially available), which is equipped for aerosol generation A measuring head for an article, such as a cigarette, and equipped with an aerosol-generating article container.

The load was applied using two load-applying cylindrical rods extending simultaneously across the diameter of all aerosol-generating articles. According to the standard test method for this instrument, the test should be performed such that twenty points of contact 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 points of contact, where each smoking article is in contact with two load-applying rods (because they are long enough to 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 only contacts one of the load-applying rods, such as discussed further below.

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

As is standard operating procedure for such equipment, a total load of 2 kg is applied for a duration of 20 seconds. After 20 seconds have elapsed (and while still applying the load 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 called the DD60A test. The standard way to measure filter hardness is when the aerosol-generating article has not been consumed. Additional information on the measurement of average radial stiffness can be found, for example, in US Published Patent Application Publication No. 2016/0128378.

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

Preferably, the PHA filter segment when measured according to the test method described in ISO 14851 "Determination of the ultimate aerobic biodegradability of plastic materials in aqueous media - Method for measuring oxygen demand in a closed respirometer (2005)" Biodegradability in aqueous media is at least about 45%, more preferably at least about 50%, and most preferably at least about 55%.

Under the same test conditions, the cellulose acetate filter segment exhibited approximately 30% biodegradability. Thus, it can be seen that the use of PHA fibers instead of cellulose acetate fibers to form filter segments can significantly improve the biodegradability of the filter segments.

The size of the PHA filter segment can vary depending on the type of aerosol-generating article into which it is introduced.

Preferably, the PHA filter segment has a length of at least about 4 millimeters, more preferably a length of at least about 5 millimeters, more preferably a length of at least about 7 millimeters, and most preferably a length of 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 between about 5 mm and about 30 mm, more preferably between about 10 mm and about 30 mm, even more preferably between about 15 mm and about 30 mm, and most preferably at Between about 20mm and about 30mm. Alternatively, in such embodiments, the length of the PHA filter segment may be about 4 mm to about 27 mm, preferably about 5 mm to about 27 mm, more preferably about 10 mm to about 27 mm, even more preferably about 15 mm mm to about 27 mm, most preferably about 20 mm to about 27 mm. Still alternatively, in such embodiments, the length of the PHA filter segment may be from about 4 millimeters to about 25 millimeters, preferably from about 5 millimeters to about 25 millimeters, more preferably from about 10 millimeters to about 25 millimeters, even more preferably about 15 mm to about 30 mm, most preferably about 20 mm to about 25 mm.

For embodiments of the invention wherein 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. Between about 30 mm, most preferably about 27 mm.

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

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 of about 5 millimeters to about 12 millimeters, such as about 5 millimeters to about 10 millimeters, or about 6 millimeters to about 8 millimeters. In a preferred embodiment, the PHA filter segment has an outer diameter of within 7.2 mm to 10%.

The shape of the PHA filter segment can 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 filter segment of fibrous filter material comprising PHA fibers. Such a filter segment would thus provide a similar construction to a conventional cellulose acetate tow filter segment.

In alternative embodiments, the PHA filter section may be in the form of a hollow tube section. The hollow tube segment has a larger exposed surface area than the equivalent diameter cylindrical filter segment, which further improves the biodegradation of the PHA filter segment.

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

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

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

Where the PHA filter segment is in the form of a hollow tube segment, the filter material may contain some cellulose acetate in addition to the PHA fibers. For example, the hollow tubular section may comprise from about 5% to 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 section can impart desired filtration and mechanical properties to the hollow tube section, as well as facilitate the manufacture of the hollow tube section.

The filter of the aerosol-generating article according to the present invention may be a single-stage filter consisting of only PHA filter sections. Alternatively, the filter of the aerosol-generating article according to the present invention may further comprise one or more additional filter segments formed of filter material which may be provided upstream of the PHA filter segment as described above or downstream. For example, a PHA filter segment may be combined with one or more axially aligned filter filter segments formed from fibrous filter material, which may or may not include PHA fibers. Alternatively or additionally, the PHA filter section 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 include a support element in the form of a hollow acetate tube. Alternatively or additionally, the PHA filter segment may be combined with an aerosol cooling element.

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

The filter of the aerosol-generating article according to the present invention may optionally contain a flavoring agent. Flavoring agents can be introduced using a variety of different means, which will be known to the skilled person. For example, the flavoring agent can be introduced in the form of a capsule, which can be provided in the PHA filter section or in a further filter section.

Preferably, the filter of the aerosol-generating article according to the present invention comprises a capsule within the PHA filter section, 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. The use of PHA fibers with a dpf value in the range of 3.2 to 5.0 means that the PHA fibers can have a relatively large cross-section. This in turn means an increase in the amount of space available between individual fibers compared to filters formed from fibers with lower dpf values. PHA filter segments formed from PHA fibers with dpf in this range are therefore particularly suitable for introduction into capsules. Capsules can be easily introduced into the PHA filter segment during manufacture. Furthermore, the capsule will be effectively held in the desired axial position within the PHA filter segment.

The filter of the aerosol-generating article according to the present invention is preferably defined by an outer wrapper, eg a tipping wrapper defining the filter section, the downstream end of the aerosol-generating substrate and any further components that may be provided therebetween. As described in WO-A-2017/162838, the tipping wrapper may comprise a removable tipping wrapper portion. This enables removal of at least a portion of the tipping wrapper prior to disposal of the aerosol-generating article. Removal of the tipping wrapper will expose the underlying filter segment and thus advantageously accelerate the rate of biodegradation of the filter material.

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

The aerosol-generating substrate may have a length of from about 5 millimeters to about 100 millimeters. Preferably, the aerosol-generating substrate has a length of at least about 5 millimeters, more preferably at least about 7 millimeters. Additionally, or alternatively, the aerosol-generating substrate preferably has a length of less than about 80 millimeters, more preferably less than about 65 millimeters, even more preferably less than about 50 millimeters. In particularly preferred embodiments, the aerosol-generating substrate has a length of less than about 35 millimeters, more preferably less than 25 millimeters, even more preferably less than about 20 millimeters. In one embodiment, the aerosol-generating substrate may have a length of about 10 millimeters. In a preferred embodiment, the aerosol-generating substrate has a length of about 12 millimeters.

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 tobacco material that is combusted to form smoke. 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 wherein the aerosol-generating article is in the form of a combustible smoking article, the aerosol-generating substrate, typically a tobacco rod, preferably has an overall length of from about 10 millimeters to about 100 millimeters, more preferably from about 30 millimeters to about 70 millimeters. The tobacco rod may include one or more of cut filler and reconstituted tobacco.

As discussed above, filters of the present invention that include PHA segments may also find application in heated aerosol-generating articles in which tobacco material is heated rather than burned to form an aerosol. In one type of heated aerosol-generating article, tobacco material is heated by one or more electrical heating elements to generate an aerosol. In another type of heated aerosol-generating article, the aerosol is generated by transferring heat 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 tobacco material, tobacco extract, or other nicotine source without combustion and in some cases without heating, such as by chemical reaction.

For embodiments in which the aerosol-generating article is in the form of a heated aerosol-generating article in which it is desired to heat the aerosol-generating substrate to form the aerosol, the aerosol-generating substrate preferably has a diameter of from about 5 millimeters to about 40 millimeters, more preferably about 9 millimeters to a length of about 15 mm.

For such embodiments wherein 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 by agglomeration of tobacco particles. The aerosol-generating substrate may comprise one or more sheets of homogenized tobacco material. The one or more sheets may be textured. As used herein, the term "textured sheet" refers to a sheet that has been curled, embossed, debossed, perforated, or otherwise deformed. Alternatively, the aerosol-generating substrate may comprise a plurality of rods or strands of homogenized tobacco material. The strips or strips can be substantially aligned with each other in the longitudinal direction, or can be randomly oriented.

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

The homogenized tobacco material used in the aerosol-generating matrix may comprise one or more intrinsic binders which are tobacco endogenous binders, one or more extrinsic binders which are tobacco exogenous binders or a combination thereof to help agglomerate particulate tobacco. Alternatively or additionally, the homogenized tobacco material used in the aerosol-generating matrix may contain other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavors, fillers , aqueous and non-aqueous solvents, and combinations thereof.

Extrinsic binders suitable for inclusion in homogenized tobacco material for use in aerosol-generating matrices are known in the art and include, but are not limited to, gums such as guar, xanthan, acacia, and locust soy 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.

Non-tobacco fibers suitable for inclusion in homogenized tobacco materials for use in aerosol-generating matrices are known in the art and include, but are not limited to: cellulose fibers; softwood fibers; hardwood fibers; jute fibers and combinations thereof. The non-tobacco fibers may be processed by suitable methods known in the art, including but not limited to: mechanical pulping; refining; chemical pulping; bleaching, prior to inclusion in the homogenized tobacco material for use in the aerosol-generating matrix ; Kraft pulping; and combinations thereof.

Aerosol-generating substrates for heated aerosol-generating articles typically include "aerosol formers", ie compounds that, in use, will promote aerosol formation and preferably substantially resist thermal degradation at the operating temperature of the aerosol-generating article or a mixture of compounds. Examples of suitable aerosol formers include: polyols such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerol; esters of polyols such as monoacetin, diacetin or triglyceride Acetate esters; 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, most preferably glycerol.

Preferably, the aerosol-generating substrate comprises at least 10% by weight aerosol former, more preferably at least 12% by weight aerosol former, more preferably at least about 15% by weight aerosol former. Alternatively or additionally, the aerosol-generating substrate preferably comprises no more than 30% by weight of aerosol-forming agent, more preferably no more than about 25% by weight of aerosol-forming agent, more preferably no more than about 20% by weight of aerosol-forming agent. % aerosol former. For example, the aerosol-generating substrate can comprise from about 10% to about 30% by weight of the aerosol former, or from about 12% to about 25% by weight of the aerosol former, or from about 15% to about 15% by weight 20% aerosol former. In a particularly preferred embodiment, the aerosol-generating substrate comprises about 18% by weight of the aerosol-forming agent.

Aerosol-generating articles according to the present invention may also include one or more additional components between the filter and the aerosol-generating substrate. For example, the aerosol-generating article may also include one or more of the following: support elements, aerosol cooling elements, and transfer elements. The configuration of such components will be known to the skilled person.

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

In other preferred embodiments of the present invention, the aerosol-generating article comprises in a linear sequence: an aerosol-generating substrate, a delivery 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 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 carbonaceous heat source at the upstream end for heating the aerosol-generating substrate during use to generate the aerosol. Suitable carbonaceous heat sources will be known to the skilled person.

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

Figure 1 shows a schematic longitudinal sectional view of an aerosol-generating article according to a first embodiment of the present invention to be used with an aerosol-generating device comprising a heater element;

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

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

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

The aerosol-generating article 10 shown in FIG. 1 includes a strip 12 of aerosol-generating substrate, a support element 14 provided as a hollow tubular element, a cooling element 16 and a port filter segment 18 . These four elements are arranged in sequence and axially aligned and defined by the matrix 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 an end of the article opposite the mouth end 22 . The aerosol-generating article 10 shown in FIG. 1 is particularly suitable for use with an electrically-operated aerosol-generating device that includes a heater for heating the strip of the aerosol-generating substrate.

In use, air is drawn from the distal end 24 to the mouth end 22 by the user through the aerosol-generating article. The distal end 24 of the aerosol-generating article can also be described as the upstream end of the aerosol-generating article 10 , and the mouth end 22 of the aerosol-generating article 10 can also be described as the downstream end of the aerosol-generating article 10 . Elements of the aerosol-generating article 10 located between the mouth end 22 and the distal end 24 may be described as being upstream of the mouth end 22 , or alternatively described as being 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 a gathered sheet of crimped homogenized tobacco material defined by a wrapper. The crimped sheet of homogenized tobacco material contains glycerol as an aerosol former.

The support element 14 is located immediately downstream of the aerosol-generating substrate 12 and adjoins the aerosol-generating substrate 12 . In the embodiment shown in Figure 1, the support element is a hollow tube formed of 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 effect, the support element 14 serves to prevent the aerosol-generating substrate 16 from being forced within the aerosol-generating article 10 towards the aerosol cooling element 16 when the heating element of the aerosol-generating device is inserted into the aerosol-generating substrate 12 . The support elements 14 also serve as spacers to separate the aerosol cooling elements 16 of the aerosol-generating article 10 from the aerosol-generating substrate 12 .

The aerosol cooling element 16 is located immediately downstream of the support element 14 and adjoins the support element 16 . In use, volatile substances released from the aerosol-generating substrate 12 travel along the aerosol cooling element 16 towards the mouth end 22 of the aerosol-generating article 10 . The volatile material may be cooled within the aerosol cooling element 16 to form an aerosol that is inhaled by the user. In the embodiment illustrated 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 .

Filter section 18 is located immediately downstream of and adjacent to aerosol cooling element 16 . In the embodiment illustrated in Figure 1, filter segment 18 comprises a single cylindrical filter segment of fibrous filter material formed from a plurality of PHA fibers having a denier per filament of about 3.4 and a 34,000 total denier. 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 external surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed and crimped by a melt spinning process. Filter segments of fibrous filter material are defined by filter segment packages (not shown).

The aerosol-generating article 100 shown in FIG. 2 includes a combustible heat source 112 , a strip of aerosol-generating substrate 114 , a delivery element 116 , an aerosol cooling element 118 , a spacer element 120 and a mouthpiece filter segment 122 . These elements are sequentially arranged and axially aligned and defined by the matrix wrapper to form the aerosol-generating article 100 .

The combustible heat source 112 comprises a substantially cylindrical carbonaceous material having a length of about 10 millimeters. The combustible heat source 112 is a blind heat source. In other words, the combustible heat source 112 does not include any air passages extending therethrough.

A strip 114 of aerosol-generating substrate is disposed at the proximal end of the combustible heat source 112 . Aerosol-generating substrate 114 includes a substantially cylindrical rod of tobacco material 124 defined by filter segment package 126 .

A non-combustible, substantially gas 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 includes a disc 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 .

Thermally conductive element 130 defines a proximal portion of combustible heat source 112 and a distal portion of aerosol-forming substrate 114 . The thermally conductive element 130 includes an aluminum foil tube. The thermally conductive element 130 is in direct contact with the proximal portion of the combustible heat source 112 and the filter filter segment package 126 of the aerosol-generating substrate 114 .

The mouthpiece filter 122 includes a single cylindrical filter segment 126 of fibrous filter material formed from a plurality of PHA fibers having a denier per filament of about 3.4 and a total denier of about 34,000. 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 exposed surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed and crimped by a melt spinning process. Filter segments of fibrous filter material are defined by filter segment packages (not shown).

The aerosol-generating article 310 shown in FIG. 3 is a combustible smoking article that includes an aerosol-generating matrix 312 and a filter 314 arranged in coaxial alignment with each other. Aerosol-generating substrate 312 includes a tobacco rod defined by an outer wrapper (not shown). The tipping wrapper 316 defines both the filter 314 and the end of the aerosol-generating substrate 312 and attaches the filter 314 to the aerosol-generating substrate 312 .

Filter 314 includes a single cylindrical filter segment 318 of fibrous filter material formed from PHA fibers having a denier per filament of about 3.4 and a total denier of about 34,000. 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 external surface area of the PHA fibers corresponds to about 0.16 square meters per gram. PHA fibers have been formed and crimped by a melt spinning process. Filter segments of fibrous filter material are defined by filter segment packages (not shown).

FIG. 4 shows a portion of an electrically operated aerosol-generating system 200 utilizing heater blades 210 to heat strips 12 of aerosol-generating substrates of aerosol-generating article 10 shown in FIG. 1 . The heater blade 210 is mounted within the aerosol-generating article chamber within the housing of the electrically-operated aerosol-generating device 212 . Aerosol-generating device 212 defines a plurality of air holes 214 to allow air to flow to aerosol-generating article 10 , as indicated by the arrows in FIG. 4 . Aerosol generating device 212 includes power and electronics not shown in FIG. 4 .

Comparative ratio

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

Table 1: Parameters of PHA Filter Section and Cellulose Acetate Filter Section

parameter PHA filter segment CA filter segment Denier per filament 3.2 3 total denier 27000 27000 Filter segment weight (mg) 406.76 409.76 External surface area (m²/g) 0.161 0.329

In a first test, the water absorption of exposing a PHA filter segment according to the present invention to a CA filter segment to water was compared. For each filter segment, the filter segment packaging was removed and the filter segment was attached to the probe of a force tensiometer (KRUSS force tensiometer, model K100). The filter segment is moved down by the probe towards the container of water and automatically stops when the filter segment comes into contact with the water. The filter segment was held in contact with water for 300 seconds so that the filter material could absorb the water, and then the filter segment was weighed to determine the amount of water absorbed during the test procedure. For each of the PHA filter segment and the CA filter segment, the test was repeated three times and the average value of water absorption was calculated, as shown in Table 2 below:

Table 2: Water uptake by PHA filter segment and CA filter segment after exposure to water

The amount of water absorbed by the PHA filter segment according to the present invention during the test process is therefore less than 40% of the amount of water absorbed by the CA filter segment. The test thus confirms that the water affinity of the PHA filter segment according to the invention is significantly reduced compared to the conventional CA filter segment.

In a second test, the water uptake of a PHA filter segment according to the invention and a CA filter segment exposed to moisture were compared. For each filter segment, the filter segment packaging was removed, and the fibers forming the filter segment were placed in a petri dish and exposed to air at 22 degrees Celsius and 50% relative humidity for 70 hours. This was performed in a vapor sorption analyzer (ProUmidSPSx-1μ). For each filter segment, the weight of the fibers was measured at the beginning of the test and the change in weight over time due to the absorption of water vapor by the fibers was measured. For each of the PHA filter section and the CA filter section, a percent difference in mass (%dm) value for the sample was calculated, which represents the increase in sample weight as a percentage of the initial weight. The %dm values for each sample at the end of the 70 hour test are shown in Table 3 below:

Table 3: Water uptake by PHA filter segment and CA filter segment after exposure to moisture

The results confirmed that the amount of water vapor absorbed by the cellulose acetate fibers during the 70 hour test was more than 50 times greater than the amount of water vapor absorbed by the PHA fibers. During testing, the PHA fibers absorbed very little water vapor. This further confirms that the water affinity of the PHA filter segment according to the present invention is significantly reduced compared to the conventional CA filter segment.

In a third test, the water absorption from mainstream flue gas was compared between a PHA filter segment according to the present invention and a conventional CA filter segment. For each filter segment, conventional smoking articles were prepared as described above in connection with FIG. 3 using a combustible tobacco rod and a single segment of filter material forming the filter. Each smoking article was then smoked in a smoking machine under ISO conditions as set forth in ISO 3308:2000 (puff volume 35ml; puff duration of 2 seconds every 60 seconds) and analysis of the resulting smoke was performed. For each filter segment, measure the amount of water in mainstream smoke collected during the smoking test, as shown in Table 4:

Table 4: Water in mainstream smoke generated during smoking tests under ISO conditions

PHA filter segment CA filter segment Water (mg/pcs of smoking product) 0.82 0.68

This demonstrates that mainstream smoke produced by smoking articles incorporating a PHA filter segment has approximately 20% higher water content than mainstream smoke from smoking articles including CA filter segments when smoked under the same conditions. This confirms that the PHA filter section absorbs less water from the mainstream flue gas than the CA filter section, thereby reducing the potential problems of drying the flue gas as described above.

Claims (14)

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 filter material formed from a plurality of fibres comprising a polyhydroxyalkanoate compound, wherein the fibres provide a total external surface area within the filter segment of from 0.12 to 0.28 m/g 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 comprising the polyhydroxyalkanoate compound have a circular cross-sectional shape and provide a total external surface area within the filter section of from 0.12 to 0.16 square meters per gram.

3. An aerosol-generating article according to claim 1, wherein the plurality of fibers comprising the polyhydroxyalkanoate compound have a Y-shaped cross-sectional shape and provide a total external surface area within the filter section of from 0.21 to 0.28 square meters per gram.

4. An aerosol-generating article according to any preceding claim, wherein the fibre comprising the polyhydroxyalkanoate compound has a denier per filament (dpf) of from 3.2 to 5.0.

5. An aerosol-generating article according to any preceding claim, wherein the total denier of the fiber comprising the polyhydroxyalkanoate compound is between 25,000 and 40,000.

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

7. 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 at 10 millimeter H₂O column to about 40 mm H₂Between the O columns.

8. An aerosol-generating article according to any preceding claim, wherein the filter segment comprising the plurality of fibres comprising the polyhydroxyalkanoate compound has a biodegradability in aqueous medium of at least 50% when tested according to ISO 14851.

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

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

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

12. 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.

13. An aerosol-generating article according to any preceding claim, wherein the aerosol-generating substrate is a tobacco rod having a length of about 5 to 15 millimetres.

14. A filter for an aerosol-generating article, the filter comprising at least one filter segment of filter material, the filter material being formed from a plurality of fibers, the plurality of fibers comprising a polyhydroxyalkanoate compound, wherein the fibers provide a total external surface area within the filter segment of from 0.12 m/g to about 0.28 m/g and wherein the at least one filter segment comprises at least about 20% by weight of the polyhydroxyalkanoate compound.

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