AEROSOL-GENERATING ARTICLE HAVING DOWNSTREAM ELEMENT COMPRISING NOVEL FILTRATION MATERIAL

Description

The present invention relates to an aerosol-generating article having a downstream element formed of a novel biodegradable filtration material.

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, most often in an abutting end-to-end relationship, with the wrapped tobacco rod. The cylindrical filter typically comprises one or more plug elements of a fibrous filtration material, such as cellulose acetate tow, circumscribed by a paper plug wrap. Conventionally, the wrapped tobacco rod and the filter are joined by a band of tipping wrapper, normally formed of an opaque paper material that circumscribes the entire length of the filter and an adjacent portion of the wrapped tobacco rod. In known filter cigarettes, the filter is typically adapted for the removal of particulate and gaseous components of the mainstream smoke.

A number of aerosol-generating articles in which tobacco is heated rather than combusted have also been proposed in the art. In heated aerosol-generating articles, an aerosol is generated by heating an aerosol-generating substrate, such as tobacco. Known heated aerosol-generating articles include, for example, smoking articles in which an aerosol is generated by electrical heating or by the transfer of heat from a combustible fuel element or heat source to an aerosol-generating substrate. During smoking, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in air drawn through the smoking article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer. Many known heated aerosol-generating articles comprise one or more elements formed of a fibrous filtration material.

After an aerosol-generating article has been smoked and discarded, it would generally be desirable for its components—and particularly for any elements formed of fibrous filtration material—to break down as quickly as possible. However, cellulose acetate, the fibrous filtration material most ordinarily used in aerosol-generating articles, is not biodegradable, and can persist in the environment for years. As a result, used cigarette filters formed from cellulose acetate have a tendency to accumulate in the environment, and are among the most commonly retrieved plastic items in beach clean-up activities. Therefore, it would be desirable to provide a more sustainable alternative to cellulose acetate for producing aerosol-generating article components and in particular, filter or mouthpiece components.

To tackle the environmental impact caused by post-consumption waste of articles containing non-biodegradable plastic, discarded directly into the environment, certain jurisdictions are introducing legislations banning single-use plastic products (SUPs). The term SUPs denotes products made wholly or partly from plastic and that are typically intended to be used just once or for a short period of time before being disposed of. Accordingly, it would be generally desirable to replace single-use plastics in aerosol-generating articles with natural, biodegradable alternatives.

A wide variety of alternative materials have in fact already been proposed for use as filtration materials for aerosol-generating articles. However, in many cases, such alternative filtration materials have been found to be unable to provide an acceptable filtration efficiency and smoking experience for the consumer. In other cases, such alternative filtration materials have been found to be lacking from a firmness and processability viewpoint. Furthermore, in many cases dispersible and degradable materials have been found to be unsuitable for use in the existing manufacturing processes, and would require too significant a modification of the existing methods and equipment to make their use commercially feasible.

Thus, it would be desirable to provide an aerosol-generating article comprising a component that is at least partially formed of a filtration material having increased biodegradability, but which provides a filtration efficiency that is comparable to that of a cellulose acetate tow. In particular, it would be desirable for the component to be formed of a biodegradable filtration material that can still effectively reduce or remove undesirable compounds from the aerosol generated from the substrate (for example, phenols).

Further, it would be desirable to provide such an aerosol-generating article that gives an acceptable sensory experience to the consumer. In particular, it would be desirable for the component to be formed of a biodegradable filtration material that has very little or no impact on the taste perceived by the consumer during use of the aerosol-generating article, and that generally does not adversely impact the smoking experience.

In addition, it would be desirable to provide such an aerosol-generating article that can be readily manufactured using existing high speed techniques and apparatus requiring only minimal modifications.

Furthermore, it would be desirable for the filtration material to be such that it can be effectively formed into components that provide an acceptable appearance and feeling to the consumer. For example, it would be desirable for the filtration material to be such that it can be effectively formed into components for an aerosol-generating article, which provide a desirable density, firmness and resistance to draw (RTD).

The present disclosure relates to an aerosol-generating article. The aerosol-generating article may comprise an aerosol-generating substrate. The aerosol-generating article may comprise a downstream element provided downstream of the aerosol-generating substrate. The downstream element may comprise a cellulosic filtration material. The cellulosic filtration material may comprise a fibrous material comprising a plurality of regenerated cellulose fibres. The regenerated cellulose fibres may be one or more of viscose fibres, modal fibres, lyocell fibres and viscose rayon fibres. The cellulosic filtration material may further comprise an additive coating applied to the plurality of regenerated cellulose fibres. The additive coating may comprise at least 5 percent by weight of exogenous lignin on a dry weight basis.

The present disclosure further relates to an aerosol-generating article. The aerosol-generating article may comprise an aerosol-generating substrate. The aerosol-generating article may comprise a downstream element provided downstream of the aerosol-generating substrate. The downstream element may comprise a cellulosic filtration material. The cellulosic filtration material may comprise a fibrous material comprising a plurality of natural fibres. The natural fibres may be one or more of flax fibres, hemp fibres, jute fibres, kenaf fibres, ramie fibres, abaca fibres, phormium fibres, sisal fibres, coir fibres, cotton fibres and kapok fibres. The cellulosic filtration material may further comprise an additive coating applied to the plurality of natural fibres. The additive coating may comprise at least 5 percent by weight of exogenous lignin on a dry weight basis.

The invention is as defined in the claims set out below.

According to a first aspect of the present invention there is provided an aerosol-generating article comprising: an aerosol-generating substrate; a downstream element provided downstream of the aerosol-generating substrate and in axial alignment with the aerosol-generating substrate, the downstream element comprising a cellulosic filtration material comprising: a fibrous material comprising a plurality of regenerated cellulose fibres, wherein the regenerated cellulose fibres are one or more of viscose fibres, modal fibres, lyocell fibres and viscose rayon fibres; and an additive coating applied to the plurality of regenerated cellulose fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis.

According to a second aspect of the present invention there is further provided an aerosol-generating article comprising: an aerosol-generating substrate; a downstream element provided downstream of the aerosol-generating substrate and in axial alignment with the aerosol-generating substrate, the downstream element comprising a cellulosic filtration material comprising: a fibrous material comprising a plurality of natural fibres, wherein the natural fibres are one or more of flax fibres, hemp fibres, jute fibres, kenaf fibres, ramie fibres, abaca fibres, phormium fibres, sisal fibres, coir fibres, cotton fibres and kapok fibres; and an additive coating applied to the plurality of natural fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis.

As used herein with reference to the invention, the term “aerosol-generating article” is used to describe an article comprising an aerosol-generating substrate that is heated to generate an inhalable aerosol for delivery to a user.

As used herein with reference to the invention, the term “aerosol-generating substrate” is used to describe a substrate comprising aerosol-generating material that is capable of releasing upon heating (including combustion) volatile compounds that can generate an aerosol.

As used herein with reference to the invention, the term “aerosol” is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles, or liquid droplets, or a combination of solid particles and liquid droplets. As used herein, the term “aerosol” encompasses the aerosol produced upon heating of a substrate in a heated aerosol-generating article and the smoke produced upon combustion of a substrate in a combustible smoking article.

As used herein with reference to the invention, the term “aerosol-generating device” is used to describe a device that interacts with the aerosol-generating substrate of the aerosol-generating article to generate an aerosol.

Aerosol-generating articles according to the invention have a proximal end through which, in use, an aerosol exits the aerosol-generating article for delivery to a user. The proximal end of the aerosol-generating article may also be referred to as the downstream end or the mouth end of the aerosol-generating article. In use, a user draws directly or indirectly on the proximal end of the aerosol-generating article in order to inhale an aerosol generated by the aerosol-generating article.

Aerosol-generating articles according to the invention have a distal end. The distal end is opposite the proximal end. The distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

Components of aerosol-generating articles according to the invention may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article.

As used herein with reference to the invention, the term “longitudinal” is used to describe the direction between the upstream end and the downstream end of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in the longitudinal direction.

As used herein with reference to the invention, the term “length” is used to describe the maximum dimension of the aerosol-generating article or a component of the aerosol-generating article in the longitudinal direction.

As used herein with reference to the invention, the term “transverse” is used to describe the direction perpendicular to the longitudinal direction. Unless otherwise stated, references to the “cross-section” of the aerosol-generating article or a component of the aerosol-generating article refer to the transverse cross-section.

As used herein with reference to the invention, the term “width” denotes the maximum dimension of the aerosol-generating article or a component of the aerosol-generating article in a transverse direction. Where the aerosol-generating article has a substantially circular cross-section, the width of the aerosol-generating article corresponds to the diameter of the aerosol-generating article. Where a component of the aerosol-generating article has a substantially circular cross-section, the width of the component of the aerosol-generating article corresponds to the diameter of the component of the aerosol-generating article.

As used herein with reference to the invention, the term “rod” is used to denote a generally cylindrical element having a substantially circular, oval or elliptical cross-section.

As used herein with reference to the invention, the term “hollow tubular element” is used to denote a generally cylindrical element having a lumen along a longitudinal axis thereof. The tubular portion may have a substantially circular, oval or elliptical cross-section. The lumen may have a substantially circular, oval or elliptical cross-section. In particular, the term “hollow tubular element” is used to denote an element defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the hollow tubular element and a downstream end of the tubular element.

Unless otherwise specified, the resistance to draw (RTD) of a component or an aerosol-generating article in accordance with the invention is measured in accordance with ISO 6565-2015. The RTD refers the pressure required to force air through the full length of a component. The terms “pressure drop” or “draw resistance” of a component or article may also refer to the “resistance to draw”. Such terms generally refer to the measurements in accordance with ISO 6565-2015 and are normally carried out at a volumetric flow rate of about 17.5 millilitres per second at the output or downstream end of the measured component, at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr) and a relative humidity of about 60%.

The aerosol stream generated during use of an aerosol-generating article is a complex mixture of chemicals, including semi-solid particles dispersed in a fluid matrix of vapours and permanent gases. As used herein with reference to the invention, the term “filtration efficiency” is used to describe the ability of an element comprising a filtration material to capture particulate matter contained in such aerosol stream. In practice, the term “filtration efficiency” denotes the fraction of the overall dry particulate matter carried in the aerosol stream that is retained within the element comprising filtration material during use.

As used herein, the term “phenols” refers to a class of chemical compounds consisting of a hydroxyl group (—OH) bonded directly to an aromatic hydrocarbon group. The phenol group includes phenol, catechol, m+P cresols, and o-cresol.

The present invention provides an improved aerosol-generating article including at least one downstream element formed of a cellulosic filtration material comprising a combination of regenerated cellulose or natural fibres and an additive coating comprising exogenous lignin. Aerosol-generating articles according to the present invention can therefore advantageously be formed of more sustainable materials, containing a reduced or zero level of single use plastics. In particular, aerosol-generating articles according to the invention use regenerated cellulose or natural fibres in place of cellulose acetate fibres to form elements such as filtration elements, thereby significantly improving the biodegradability of the aerosol-generating article.

The addition of the additive coating to the regenerated cellulose or natural fibres has advantageously been found to significantly improve the filtration properties of the downstream element. In particular, the use of an additive coating including exogenous lignin has been found to significantly improve the reduction of phenols and other undesirable compounds from the mainstream aerosol, compared to the use of the regenerated cellulose or natural fibres alone. The composition of the additive coating can advantageously be modified to optimise the filtration efficiency of the downstream element, such that it can achieve a similar reduction in phenols and other undesirable compounds as a conventional cellulose acetate tow.

The additive coating contains exogenous lignin and optionally, one or more additional compounds which provide functional groups such as acetyl groups within the cellulosic filtration material that can directly act to scavenge phenols and other undesirable compounds from the mainstream aerosol. In addition, it has been found that the lignin and other optional components of the additive coating advantageously improve properties of the regenerated cellulose or natural fibres such that the capture and retention of mainstream aerosol components can be further improved. For example, it has been advantageously found that the inclusion of the additive coating causes a reduction in the glass transition temperature, which can lead to increased speed of adsorption of compounds from the mainstream aerosol.

Furthermore, the application of the additive coating to the regenerated cellulose or natural fibres of the cellulosic filtration material has been found to provide benefits in relation to the physical properties of the fibres, which may facilitate the formation of the downstream element. For example, the application of the additive coating has been found to make the fibres more pliable, which facilitates the processing of the cellulosic filtration material. The additive coating additionally improves the bonding between the fibres so that a downstream element having the desired density and firmness can be more readily produced.

It has further been found that the additive coating increases the hydrophobicity of the regenerated cellulose or natural fibres, which in turn reduces the adsorption and trapping of water from the mainstream aerosol. This is beneficial, since any significant reduction in the moisture content of the mainstream aerosol delivered to the consumer can results in the smoke or aerosol being perceived as undesirably ‘dry’, which may have an adverse effect on the overall smoking experience.

Overall, the combination of the regenerated cellulose or natural fibres and additive coating can produce a downstream element that is significantly more biodegradable than an equivalent element formed of cellulose acetate, whilst retaining a desirable level of filtration and acceptable physical properties such that the inclusion of the downstream element does not adversely impact the consumer's experience.

As defined above, the cellulosic filtration material forming the downstream element of aerosol-generating articles according to the present invention comprises a fibrous material formed of a plurality of regenerated cellulose or natural fibres, to which an additive coating has been applied. The additive coating covers at least part of the external surface of the regenerated cellulose or natural fibres and therefore provides an outer coating layer on the fibres. The additive coating may be applied over a part of the external surface of the regenerated cellulose or natural fibres. Alternatively, the additive coating may be applied over substantially all of the external surface of the regenerated cellulose or natural fibres. The application of the additive coating to the external surface of the regenerated cellulose or natural fibres advantageously maximises the contact between the mainstream aerosol passing through the downstream element during use and the additive coating. This in turn maximises the capability of the additive coating to reduce phenols and other undesirable compounds in the smoke or aerosol.

In the downstream element of aerosol-generating articles of the present invention, the fibrous material forms the main body of the downstream element. According to a first aspect of the present invention, the fibrous material comprises a plurality of regenerated cellulose fibres.

The term “regenerated cellulose fibres” is used herein to mean cellulose fibres which have been formed by processing a naturally occurring cellulose material to provide cellulose fibres having a desired physical property. A typical process for forming regenerated cellulose fibres includes the steps of: pulping a naturally occurring cellulose material, such as wood chips, to form a pulp; subjecting the pulp to one or more treatment steps to alter the physical properties of the cellulose; and forming fibres of regenerated cellulose from the treated pulp, for example by spinning cellulose fibres by passing the pulp through a spinneret.

For the purposes of the invention, the regenerated cellulose fibres are selected from viscose fibres, modal fibres, Lyocell fibres and viscose rayon fibres, or a combination thereof. Particularly preferably, the fibrous material comprises viscose fibres. In some embodiments, the fibrous material consists of viscose fibres.

Regenerated cellulose fibres including acetate groups are specifically excluded from the scope of the present invention.

Preferably, the fibrous material comprises at least 50 percent of regenerated cellulose fibres, more preferably at least 60 percent of regenerated cellulose fibres, more preferably at least 70 percent of regenerated cellulose fibres, more preferably at least 80 percent of regenerated cellulose fibres, more preferably at least 90 percent of regenerated cellulose fibres.

Preferably, the fibrous material comprises at least 50 percent of viscose fibres, more preferably at least 60 percent of viscose fibres, more preferably at least 70 percent of viscose fibres, more preferably at least 80 percent of viscose fibres, more preferably at least 90 percent of viscose fibres.

The fibrous material preferably consists of the regenerated cellulose fibres, so that the regenerated cellulose fibres account for 100 percent of the fibrous material and the regenerated cellulose fibres are not combined with any other type of fibre. Alternatively, the fibrous material may include other fibres in addition to the regenerated cellulose fibres. Such additional fibres can be incorporated into the cellulosic filtration material by mixing the additional fibres with the regenerated cellulose fibres during manufacture of the cellulosic filtration material. Preferably, the additional fibres are formed of biodegradable materials. Suitable additional types of fibres include but are not limited to natural cellulosic fibres, such as flax fibres, hemp fibres, jute fibres, kenaf fibres, ramie fibres, abaca fibres, phormium fibres, sisal fibres, coir fibres, cotton fibres, or kapok fibres.

According to a second aspect of the invention, the fibrous material comprises a plurality of natural fibres.

The term “natural fibres” is used herein to mean plant-based fibres that have been derived directly from a plant source and which are therefore not manmade. The natural fibres may be untreated. Alternatively and preferably, the natural fibres may be treated in order to improve their properties, for example, the natural fibres may undergo mercerisation prior to the application of the additive coating, as discussed in more detail below.

For the purposes of the invention, the natural fibres are selected from flax fibres, hemp fibres, jute fibres, kenaf fibres, ramie fibres, abaca fibres, phormium fibres, sisal fibres, coir fibres, cotton fibres, kapok fibres, or a combination thereof. Particularly preferably, the fibrous material comprises cotton fibres or a combination or cotton fibres and kapok fibres. In certain embodiments of the invention, the natural fibres comprise mercerised fibres.

Preferably, the fibrous material comprises at least 50 percent of natural fibres, more preferably at least 60 percent of natural fibres, more preferably at least 70 percent of natural fibres, more preferably at least 80 percent of natural fibres, more preferably at least 90 percent of natural fibres.

Preferably, the fibrous material comprises at least 50 percent of cotton fibres, more preferably at least 60 percent of cotton fibres, more preferably at least 70 percent of cotton fibres, more preferably at least 80 percent of cotton fibres, more preferably at least 90 percent of cotton fibres.

The fibrous material preferably consists of the natural fibres, so that the natural fibres account for 100 percent of the fibrous material and the natural fibres are not combined with any other type of fibre. Alternatively, the fibrous material may include other fibres in addition to the natural fibres. Such additional fibres can be incorporated into the cellulosic filtration material by mixing the additional fibres with the natural fibres during manufacture of the cellulosic filtration material. Preferably, the additional fibres are formed of biodegradable materials. Suitable additional types of fibres include but are not limited to regenerated cellulose fibres, such as viscose.

The following discussion of the ‘fibrous material’ refers to both aspects of the invention unless stated otherwise.

Preferably, the fibrous material does not include cellulose acetate fibres or any other fibres formed of non-biodegradable polymers.

Preferably, the fibrous material is a non-woven material. Preferably, the regenerated cellulose or natural fibres are formed into a fibrous tow material, similar to that provided in conventional cellulose acetate filters.

Preferably, the fibrous material comprises randomly oriented regenerated cellulose or natural fibres.

Advantageously, using a filtration material that comprises randomly oriented fibres improves the degradation of the filtration material. This is because the randomly oriented fibres can more easily disperse after the filter has been discarded, particularly when compared with the substantially continuous filaments of traditional cellulose acetate tow filters. Increased dispersion of the fibres increases the exposure of the individual fibres to the environment, thus increasing the rate at which the filtration material degrades.

The random orientation of the fibres advantageously provides the required resistance of the filtration material to mechanical deformation, such that the downstream element can withstand being grasped by the consumer during smoking of the aerosol-generating article. The random orientation of the fibres also provides the required resistance to draw such that the smoking experience of aerosol-generating articles according to the invention is substantially the same as the smoking experience using an aerosol-generating article having a traditional cellulose acetate tow filter.

Preferably, the regenerated cellulose or natural fibres are crimped staple fibres, which helps to reduce mechanical degradation of the fibres during processing of the filtration material to form the downstream element, and during subsequent assembly of the aerosol-generating article. The fibres can be crimped using a known method for crimping textile fibres.

The regenerated cellulose or natural fibres may have a substantially round cross-section.

Preferably, the regenerated cellulose or natural fibres have a denier per filament (dpf) of at least about 2.0, more preferably at least 2.5, more preferably at least 3.0, more preferably at least 3.2, more preferably at least 3.5, more preferably at least about 4.0, more preferably at least 4.5, more preferably at least 5.0.

Preferably, the regenerated cellulose or natural fibres have a denier per filament of no more than 10.0, more preferably no more than 9.0, more preferably no more than 8.0, more preferably no more than 7.0.

The denier per filament, corresponding to the average denier of an individual fibre within the filter, is the weight in grams of a single fibre or filament having a length of 9000 metres. In the present invention, the value of dpf therefore gives an indication of the thickness of each of the individual regenerated cellulose or natural fibres within the cellulosic filtration material. The denier per filament is expressed in units of denier, where 1 denier corresponds to 1 gram per 9000 metres. The dpf of a filter or filter segment can be readily determined based on the measurement of weight and length of a sample of representative fibres from the cellulosic filtration material.

Preferably, the total denier of the cellulosic filtration material comprising the regenerated cellulose or natural fibres is between about 20,000 and about 50,000, more preferably between about 25,000 and about 40,000, more preferably between about 30,000 and about 40,000. The “total denier” of the filtration material defines the total weight in grams of 9000 metres of the combined fibres forming the filtration material. The total denier for the cellulosic filtration material therefore corresponds to the denier per filament multiplied by the total number of fibres in the cellulosic filtration material.

Preferably, the cellulosic filtration material comprises at least 85 percent by weight of the fibrous material, more preferably at least 88 percent by weight of the fibrous material, more preferably at least 90 percent by weight of the fibrous material, more preferably at least 95 percent by weight of the fibrous material.

The cellulosic filtration material preferably comprises up to 99 percent by weight of the fibrous material, more preferably up to 98 percent by weight of the fibrous material, more preferably up to 95 percent by weight of the additive coating, on a dry weight basis.

Advantageously, the regenerated cellulose or natural fibres may be treated with an additive enhancer prior to the application of the additive coating. For example, regenerated cellulose may be contacted with an additive enhancer during the formation of the fibres, such as during an extrusion or spinning process to form the fibres, or during drying or curing.

As used herein, the term “additive enhancer” refers to a compound that controls the polarity of the regenerated cellulose or natural fibres, in order to improve the retention of the additive coating on the surface of the fibres. Suitable additive enhancers include but are not limited to chitin and chitosan.

As defined above, in the cellulosic filtration material forming the downstream element of aerosol-generating article according to the present invention, an additive coating is applied to the plurality of regenerated cellulose or natural fibres, such that the fibres are at least partially coated with the additive coating.

Preferably, the cellulosic filtration material comprises at least 1 percent by weight of the additive coating, more preferably at least 2 percent by weight of the additive coating, more preferably at least 3 percent by weight of the additive coating, more preferably at least 4 percent by weight of the additive coating, more preferably at least 5 percent by weight of the additive coating, on a dry weight basis.

The cellulosic filtration material preferably comprises up to 15 percent by weight of the additive coating, more preferably up to 12 percent by weight of the additive coating, more preferably up to 10 percent by weight of the additive coating, on a dry weight basis.

The additive coating comprises at least one additive for reducing phenols. That is, the additive coating comprises at least one additive which is capable of capturing or otherwise converting at least some of the phenols and phenol derivatives produced upon heating or burning of the aerosol-generating substrate. Preferably, the additive coating comprises at least one additive for reducing other undesirable compounds from the mainstream aerosol, such as carbon monoxide, carbon dioxide and nitrogen oxides.

Preferably, the additive coating is biodegradable such that the cellulosic filtration material including the combination of additive coating and regenerated cellulose or natural fibres is biodegradable.

According to the invention, the additive coating comprises at least 5 percent by weight of exogenous lignin, on a dry weight basis. Preferably, the additive coating comprises at least 6 percent by weight of exogenous lignin, more preferably at least 8 percent by weight of exogenous lignin, more preferably at least 10 percent by weight of exogenous lignin, more preferably at least 12 percent by weight of exogenous lignin, more preferably at least 15 percent by weight of exogenous lignin, on a dry weight basis.

The additive coating preferably comprises up to 50 percent by weight of exogenous lignin, more preferably up to 45 percent by weight of exogenous lignin, more preferably up to 40 percent by weight of exogenous lignin, more preferably up to 35 percent by weight of exogenous lignin, more preferably up to 30 percent by weight, on a dry weight basis.

For example, the additive coating may comprise between 5 percent by weight and 50 percent by weight of exogenous lignin, or between 6 percent by weight and 50 percent by weight of exogenous lignin, or between 8 percent by weight and 50 percent by weight of exogenous lignin, or between 10 percent by weight and 50 percent by weight of exogenous lignin, or between 12 percent by weight and 50 percent by weight of exogenous lignin, or between 15 percent by weight and 50 percent by weight of exogenous lignin, or between 5 percent by weight and 45 percent by weight of exogenous lignin, or between 6 percent by weight and 45 percent by weight of exogenous lignin, or between 8 percent by weight and 45 percent by weight of exogenous lignin, or between 10 percent by weight and 45 percent by weight of exogenous lignin, or between 12 percent by weight and 45 percent by weight of exogenous lignin, or between 15 percent by weight and 45 percent by weight of exogenous lignin, or between 5 percent by weight and 40 percent by weight of exogenous lignin, or between 6 percent by weight and 40 percent by weight of exogenous lignin, or between 8 percent by weight and 40 percent by weight of exogenous lignin, or between 10 percent by weight and 40 percent by weight of exogenous lignin, or between 12 percent by weight and 40 percent by weight of exogenous lignin, or between 15 percent by weight and 40 percent by weight of exogenous lignin, or between 5 percent by weight and 35 percent by weight of exogenous lignin, or between 6 percent by weight and 35 percent by weight of exogenous lignin, or between 8 percent by weight and 35 percent by weight of exogenous lignin, or between 10 percent by weight and 35 percent by weight of exogenous lignin, or between 12 percent by weight and 35 percent by weight of exogenous lignin, or between 15 percent by weight and 35 percent by weight of exogenous lignin, or between 5 percent by weight and 30 percent by weight of exogenous lignin, or between 6 percent by weight and 30 percent by weight of exogenous lignin, or between 8 percent by weight and 30 percent by weight of exogenous lignin, or between 10 percent by weight and 30 percent by weight of exogenous lignin, or between 12 percent by weight and 30 percent by weight of exogenous lignin, or between 15 percent by weight and 30 percent by weight of exogenous lignin, on a dry weight basis.

Lignin provides numerous active functional groups that are capable of scavenging phenols, including acetyl groups. The inclusion of lignin in the cellulosic filtration material therefore reduces the phenols in the mainstream aerosol as it passes through the downstream element from the aerosol-generating substrate.

The ranges above refer to the amount of exogenous lignin in the additive coating. The term “exogenous” refers to any lignin incorporated into the additive coating which is provided in an isolated form and which has been extracted and separated from other components of the plant material from which it derives. The exogenous lignin is therefore provided extrinsically from any cellulosic plant material that is present. In other words, it is a separate and distinct source of lignin to any lignin provided intrinsically within any plant material in the cellulosic filtration material. The same definition of “exogenous” applies in relation to hemicellulose, which is described below.

For the purposes of the present invention, the exogenous lignin may be extracted from any plant source. For example, the exogenous lignin may be extracted from weed straw pulp or wood pulp.

In certain preferred embodiments of the present invention, the exogenous lignin may be in the form of acetylated lignin. Acetylated lignin is a form of modified lignin, which has been modified to increase the number of acetyl groups. As a result of the increased number of acetyl groups, the use of acetylated lignin may further improve the capabilities of lignin in reducing phenols from the mainstream aerosol.

Without wishing to be bound by theory, the introduction of acetyl groups is understood to also have an impact on wettability of the cellulosic filtration material. In fact, the esterification reaction that occurs between the acetyl groups and at least some hydroxyl groups in the cellulose molecules induces a change in the nature of at least some of the regenerated cellulose or natural fibres from hydrophilic to hydrophobic. Thus, the regenerated cellulose or natural fibres to which an additive coating comprising acetylated lignin has been applied may have a reduced tendency to absorb moisture from the smoke or aerosol flowing through the plug element. This is desirable in that it may counter the effect, which has been observed with some conventional cellulose acetate filters and is often referred to as ‘dry smoke’, whereby the smoke or aerosol delivered to the consumer has a significantly reduced moisture content and may, therefore, under certain conditions, be perceived as undesirably dry.

In certain preferred embodiments of the present invention, the exogenous lignin may be in the form of organosolv lignin. Organosolv lignin is lignin that has been produced using an organosolv pulping technique which employs aqueous organic solvents to solubilise the lignin. The use of organosolv lignin is desirable due to its high purity and low ash content.

In certain preferred embodiments of the present invention, the exogenous lignin may be light-coloured, nearly white or white lignin. Such lignin is lighter than standard lignin, which is typically yellow or brown in colour. The use of a light-coloured, nearly white or white lignin may be advantageous since the exogenous lignin will have a colour that is closer to that of the fibrous material to which the additive coating is applied. The exogenous lignin will therefore not be visible within the cellulosic filtration material, such that the overall appearance of the cellulosic filtration material can be similar to a conventional filter of a smoking article.

Suitable processes for producing light-coloured, nearly white or white lignin would be known to the skilled person. For example, suitable processes are disclosed in EP-A-3707194.

Preferably, the cellulosic filtration material comprises at least 0.5 percent by weight of exogenous lignin, more preferably at least 1 percent of exogenous lignin, more preferably at least 1.5 percent by weight of exogenous lignin, more preferably at least 2 percent by weight of exogenous lignin, on a dry weight basis.

Preferably, the cellulosic filtration material comprises up to 8 percent by weight of exogenous lignin, more preferably up to 6 percent by weight of exogenous lignin, more preferably up to 5 percent by weight of exogenous lignin, more preferably up to 4 percent by weight of exogenous lignin, on a dry weight basis.

For example, the cellulosic filtration material may comprise between 0.5 percent by weight and 8 percent by weight of exogenous lignin, or between 0.5 percent by weight and 6 percent by weight of exogenous lignin, or between 0.5 percent by weight and 5 percent by weight of exogenous lignin, or between 0.5 percent by weight and 4 percent by weight of exogenous lignin, between 1 percent by weight and 8 percent by weight of exogenous lignin, or between 1 percent by weight and 6 percent by weight of exogenous lignin, or between 1 percent by weight and 5 percent by weight of exogenous lignin, or between 1 percent by weight and 4 percent by weight of exogenous lignin, or between 1.5 percent by weight and 8 percent by weight of exogenous lignin, or between 1.5 percent by weight and 6 percent by weight of exogenous lignin, or between 1.5 percent by weight and 5 percent by weight of exogenous lignin, or between 1.5 percent by weight and 4 percent by weight of exogenous lignin, or between 2 percent by weight and 8 percent by weight of exogenous lignin, or between 2 percent by weight and 6 percent by weight of exogenous lignin, or between 2 percent by weight and 5 percent by weight of exogenous lignin, or between 2 percent by weight and 4 percent by weight of exogenous lignin.

Preferably, the additive coating further comprises at least one polysaccharide.

The at least one polysaccharide advantageously provides additional active functional groups, such as acetyl groups, that are particularly effective at scavenging phenols and other undesirable gaseous compounds generated from the aerosol-generating substrate. The inclusion of the additional polysaccharide in the additive coating, in addition to the lignin, therefore further reduces the level of phenols and other undesirable gaseous compounds in the mainstream aerosol as it passes through the downstream element from the aerosol-generating substrate.

The polysaccharide can bind effectively to the lignin in the additive coating and may provide the additive coating with improved temperature stability. Further, it is believed that the presence of lignin reduces the crystallinity and glass transition temperature of the polysaccharide such that the polysaccharide has an increased capacity to scavenge and store gases from the mainstream aerosol and an increased speed of absorbing the gases.

The at least one polysaccharide may include one or more plant based polysaccharides. Preferably, the at least one polysaccharide comprises a plant based starch. For example, the additive coating preferably comprises exogenous hemicellulose, corn starch, potato starch or a combination thereof. In particularly preferred embodiments, the additive coating comprises hemicellulose. In other preferred embodiments, the at least one polysaccharide comprises corn starch. In other preferred embodiments, the at least one polysaccharide comprises a modified starch, such as acetylated starch, or oxidised starch. In other preferred embodiments, the at least one polysaccharide comprises a sugar or acetylated sugar.

Similar to what is described above in connection with acetylated lignin, the addition of acetyl groups to the starch molecule or to a sugar molecule is understood to further have some impact on wettability of the cellulosic filtration material. Without wishing to be bound by theory, by reacting with some of the hydroxyl groups in the cellulose molecules, the acetyl groups may contribute to shift the nature of the regenerated cellulosic or natural fibres in the cellulosic filtration material from hydrophilic to hydrophobic. This may advantageously reduce the tendency of the cellulosic filtration material element to absorb moisture and capture nicotine from the aerosol flowing through.

Preferably, the additive coating comprises at least 20 percent by weight of the at least one polysaccharide, more preferably at least 30 percent by weight of the at least one polysaccharide, more preferably at least 40 percent by weight of the at least one polysaccharide, more preferably at least 50 percent by weight of the at least one polysaccharide, on a dry weight basis.

Preferably, the additive coating comprises up to 90 percent by weight of the at least one polysaccharide, more preferably up to 85 percent by weight of the at least one polysaccharide, more preferably up to 80 percent by weight of the at least one polysaccharide, on a dry weight basis.

For example, the additive coating may comprise between 20 percent by weight and 90 percent by weight of the at least one polysaccharide, or between 30 percent by weight and 90 percent by weight of the at least one polysaccharide, or between 40 percent by weight and 90 percent by weight of the at least one polysaccharide, or between 50 percent by weight and 90 percent by weight of the at least one polysaccharide, or between 20 percent by weight and 85 percent by weight of the at least one polysaccharide, or between 30 percent by weight and 85 percent by weight of the at least one polysaccharide, or between 40 percent by weight and 85 percent by weight of the at least one polysaccharide, or between 50 percent by weight and 85 percent by weight of the at least one polysaccharide, or between 20 percent by weight and 80 percent by weight of the at least one polysaccharide, or between 30 percent by weight and 80 percent by weight of the at least one polysaccharide, or between 40 percent by weight and 80 percent by weight of the at least one polysaccharide, or between 50 percent by weight and 80 percent by weight of the at least one polysaccharide, on a dry weight basis.

Preferably, the cellulosic filtration material comprises at least 1 percent by weight of the at least one polysaccharide, more preferably at least 2 percent of the at least one polysaccharide, more preferably at least 5 percent of the at least one polysaccharide, more preferably at least 6 percent by weight of the at least one polysaccharide, on a dry weight basis.

Preferably, the cellulosic filtration material comprises up to 15 percent by weight of the at least one polysaccharide, more preferably up to 12 percent by weight of the at least one polysaccharide, more preferably up to 10 percent by weight of the at least one polysaccharide, more preferably up to 8 percent by weight of the at least one polysaccharide, on a dry weight basis.

For example, the cellulosic filtration material may comprise between 1 and 15 percent by weight of the at least one polysaccharide, or between 1 percent by weight and 12 percent by weight of the at least one polysaccharide, or between 1 percent by weight and 10 percent by weight of the at least one polysaccharide, or between 1 percent by weight and 8 percent by weight of the at least one polysaccharide, between 2 and 15 percent by weight of the at least one polysaccharide, or between 2 percent by weight and 12 percent by weight of the at least one polysaccharide, or between 2 percent by weight and 10 percent by weight of the at least one polysaccharide, or between 2 percent by weight and 8 percent by weight of the at least one polysaccharide, or between 5 and 15 percent by weight of the at least one polysaccharide, or between 5 percent by weight and 12 percent by weight of the at least one polysaccharide, or between 5 percent by weight and 10 percent by weight of the at least one polysaccharide, or between 5 percent by weight and 8 percent by weight of the at least one polysaccharide, or between 6 and 15 percent by weight of the at least one polysaccharide, or between 6 percent by weight and 12 percent by weight of the at least one polysaccharide, or between 6 percent by weight and 10 percent by weight of the at least one polysaccharide, or between 6 percent by weight and 8 percent by weight of the at least one polysaccharide, on a dry weight basis.

The weight ratio of the at least one polysaccharide to the exogenous lignin in the additive coating is preferably at least 2, more preferably at least 2.5, more preferably at least 3, more preferably at least 3.5, more preferably at least 4. The weight ratio of the at least one polysaccharide to the exogenous lignin in the additive coating may be up to 6.

The additive coating preferably comprises an exogenous hemicellulose. Preferably, the additive coating comprises at least 5 percent by weight of exogenous hemicellulose, more preferably at least 6 percent by weight of exogenous hemicellulose, more preferably at least 8 percent by weight of exogenous hemicellulose, more preferably at least 10 percent by weight of exogenous hemicellulose, on a dry weight basis.

Preferably, the additive coating comprises up to 50 percent by weight of exogenous hemicellulose, more preferably up to 45 percent by weight of exogenous hemicellulose, more preferably up to 40 percent by weight of exogenous hemicellulose, more preferably up to 35 percent by weight of exogenous hemicellulose, more preferably up to 30 percent by weight of hemicellulose, on a dry weight basis.

For example, the additive coating may comprise between 5 percent by weight and 50 percent by weight of exogenous hemicellulose, or between 6 percent by weight and 50 percent by weight of exogenous hemicellulose, or between 8 percent by weight and 50 percent by weight of exogenous hemicellulose, or between 10 percent by weight and 50 percent by weight of exogenous hemicellulose, or between 5 percent by weight and 45 percent by weight of exogenous hemicellulose, or between 6 percent by weight and 45 percent by weight of exogenous hemicellulose, or between 8 percent by weight and 45 percent by weight of exogenous hemicellulose, or between 10 percent by weight and 45 percent by weight of exogenous hemicellulose, or between 5 percent by weight and 40 percent by weight of exogenous hemicellulose, or between 6 percent by weight and 40 percent by weight of exogenous hemicellulose, or between 8 percent by weight and 40 percent by weight of exogenous hemicellulose, or between 10 percent by weight and 40 percent by weight of exogenous hemicellulose, or between 5 percent by weight and 35 percent by weight of exogenous hemicellulose, or between 6 percent by weight and 35 percent by weight of exogenous hemicellulose, or between 8 percent by weight and 35 percent by weight of exogenous hemicellulose, or between 10 percent by weight and 35 percent by weight of exogenous hemicellulose, or between 5 percent by weight and 30 percent by weight of exogenous hemicellulose, or between 6 percent by weight and 30 percent by weight of exogenous hemicellulose, or between 8 percent by weight and 30 percent by weight of exogenous hemicellulose, or between 10 percent by weight and 30 percent by weight of exogenous hemicellulose, on a dry weight basis.

Hemicellulose provides numerous active functional groups that are capable of scavenging phenols and other undesirable gaseous compounds generated from the aerosol-generating substrate. The inclusion of hemicellulose in the cellulosic filtration material, in addition to lignin, therefore further reduces the level of phenols and certain other undesirable gaseous compounds in the mainstream aerosol as it passes through the downstream element from the aerosol-generating substrate.

For the purposes of the present invention, the exogenous hemicellulose may be extracted from any plant source. For example, the exogenous hemicellulose may be extracted from weed straw pulp or wood pulp. The lignin and hemicellulose may be extracted from the same plant source.

Preferably, the cellulosic filtration material comprises at least 0.5 percent by weight of exogenous hemicellulose, more preferably at least 1 percent by weight of exogenous hemicellulose, more preferably at least 1.5 percent of exogenous hemicellulose, more preferably at least 2 percent of exogenous hemicellulose, on a dry weight basis.

Preferably, the cellulosic filtration material comprises up to 8 percent by weight of exogenous hemicellulose, more preferably up to 6 percent by weight of exogenous hemicellulose, more preferably up to 5 percent by weight of exogenous hemicellulose, more preferably up to 4 percent by weight of exogenous hemicellulose, on a dry weight basis.

For example, the cellulosic filtration material may comprise between 0.5 and 8 percent by weight of exogenous hemicellulose, or between 0.5 percent by weight and 6 percent by weight of exogenous hemicellulose, or between 0.5 percent by weight and 5 percent by weight of exogenous hemicellulose, or between 0.5 percent by weight and 4 percent by weight of exogenous hemicellulose, or between 1 and 8 percent by weight of exogenous hemicellulose, or between 1 percent by weight and 6 percent by weight of exogenous hemicellulose, or between 1 percent by weight and 5 percent by weight of exogenous hemicellulose, or between 1 percent by weight and 4 percent by weight of exogenous hemicellulose, or between 1.5 and 8 percent by weight of exogenous hemicellulose, or between 1.5 percent by weight and 6 percent by weight of exogenous hemicellulose, or between 1.5 percent by weight and 5 percent by weight of exogenous hemicellulose, or between 1.5 percent by weight and 4 percent by weight of exogenous hemicellulose, or between 2 and 8 percent by weight of exogenous hemicellulose, or between 2 percent by weight and 6 percent by weight of exogenous hemicellulose, or between 2 percent by weight and 5 percent by weight of exogenous hemicellulose, or between 2 percent by weight and 4 percent by weight of exogenous hemicellulose, on a dry weight basis.

The combined amount of exogenous lignin and exogenous hemicellulose in the additive coating is at least 10 percent by weight, more preferably at least 12 percent by weight, more preferably at least 14 percent by weight, more preferably at least 16 percent by weight, more preferably at least 18 percent by weight, on a dry weight basis.

The combined amount of exogenous lignin and exogenous hemicellulose in the additive coating is preferably up to 50 percent by weight, more preferably up to 45 percent by weight, more preferably up to 40 percent by weight, more preferably up to 35 percent by weight, more preferably up to 30 percent by weight, on a dry weight basis.

For example, the combined amount of exogenous lignin and exogenous hemicellulose in the additive coating may be between 10 percent by weight and 50 percent by weight, or between 12 percent by weight and 45 percent by weight, or between 14 percent by weight and 40 percent by weight, or between 16 percent by weight and 35 percent by weight, or between 18 percent by weight and 30 percent by weight, on a dry weight basis.

The combined amount of exogenous lignin and exogenous hemicellulose in the cellulosic filtration material is preferably at least 1 percent by weight, more preferably at least 1.5 percent by weight, more preferably at least 2 percent by weight, more preferably at least 2.5 percent by weight, on a dry weight basis.

The combined amount of exogenous lignin and exogenous hemicellulose in the cellulosic filtration material is preferably up to 10 percent by weight, more preferably up to 8 percent by weight, more preferably up to 6 percent by weight, more preferably up to 4 percent by weight, on a dry weight basis.

For example, the combined amount of exogenous lignin and exogenous hemicellulose in the cellulosic filtration material may be between 1 percent by weight and 10 percent by weight, or between 1.5 percent by weight and 8 percent by weight, or between 2 percent by weight and 6 percent by weight, or between 2.5 percent by weight and 4 percent by weight, on a dry weight basis.

Alternatively on in addition, the additive coating may further comprise at least one monosaccharide derivative or disaccharide derivative, for example, sucrose acetate isobutyrate.

The at least one monosaccharide derivative or disaccharide derivative advantageously provides additional active functional groups, such as acetyl and carboxymethyl groups, that are particularly effective at scavenging phenols and other undesirable gaseous compounds generated from the aerosol-generating substrate. The inclusion of the additional monosaccharide derivative or disaccharide derivative in the additive coating, in addition to the lignin or lignin/polysaccharide mixture, therefore further reduces the level of phenols and other undesirable gaseous compounds in the mainstream aerosol as it passes through the downstream element from the aerosol-generating substrate.

The monosaccharide derivative or disaccharide derivative has also been found to advantageously improve the hydrophobicity of the cellulosic filtration material as well as the temperature stability.

Preferably, the additive coating comprises at least 20 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, more preferably at least 30 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, more preferably at least 40 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, more preferably at least 50 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, on a dry weight basis.

Preferably, the additive coating comprises up to 90 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, more preferably up to 85 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, more preferably up to 80 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, on a dry weight basis.

For example, the additive coating may comprise between 20 percent by weight and 90 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 30 percent by weight and 90 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 40 percent by weight and 90 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 50 percent by weight and 90 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 20 percent by weight and 85 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 30 percent by weight and 85 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 40 percent by weight and 85 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 50 percent by weight and 85 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 20 percent by weight and 80 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 30 percent by weight and 80 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 40 percent by weight and 80 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, or between 50 percent by weight and 80 percent by weight of the at least one monosaccharide derivative or disaccharide derivative, on a dry weight basis.

Alternatively or in addition, the additive coating may further comprise at least one cross-linking agent. The at least one cross-linking agent preferably provides effective cross-linking of the lignin and polysaccharide (where present).

The inclusion of at least one cross-linking agent therefore increases the viscosity of the additive coating such that it can be more readily applied to the fibres. The inclusion of the at least one cross-linking agent also improves the ability of the additive coating to bind the regenerated cellulose or natural fibres of the fibrous material together. Advantageously, the inclusion of the at least one cross-linking agent may improve the hydrophobicity of the cellulosic filtration material as well as the temperature stability. Certain cross-linking agents may additionally provide active functional groups for scavenging of phenols and other undesirable gaseous compounds generated from the aerosol-generating substrate. This may further increase the reduction of the level of phenols and other undesirable gaseous compounds in the mainstream aerosol as it passes through the downstream element from the aerosol-generating substrate.

Suitable cross-linking agents include but are not limited to: acetic anhydride, succinic anhydride, pyridine, triacetin or combinations thereof.

Preferably, the additive coating comprises at least 0.1 percent by weight of the at least one cross-linking agent, more preferably at least 0.2 percent by weight of the at least one cross-linking agent, more preferably at least 0.3 percent by weight of the at least one cross-linking agent, more preferably at least 0.5 percent by weight of the at least one cross-linking agent, on a dry weight basis.

Preferably, the additive coating comprises up to 10 percent by weight of the at least one cross-linking agent, more preferably up to 5 percent by weight of the at least one cross-linking agent, more preferably up to 2 percent by weight of the at least one cross-linking agent, on a dry weight basis.

For example, the additive coating may comprise between 0.1 percent by weight and 10 percent by weight of the at least one cross-linking agent, or between 0.2 percent by weight and 10 percent by weight of the at least one cross-linking agent, or between 0.3 percent by weight and 10 percent by weight of the at least one cross-linking agent, or between 0.5 percent by weight and 10 percent by weight of the at least one cross-linking agent, or between 0.1 percent by weight and 5 percent by weight of the at least one cross-linking agent, or between 0.2 percent by weight and 5 percent by weight of the at least one cross-linking agent, or between 0.3 percent by weight and 5 percent by weight of the at least one cross-linking agent, or between 0.5 percent by weight and 5 percent by weight of the at least one cross-linking agent, between 0.1 percent by weight and 2 percent by weight of the at least one cross-linking agent, or between 0.2 percent by weight and 2 percent by weight of the at least one cross-linking agent, or between 0.3 percent by weight and 2 percent by weight of the at least one cross-linking agent, or between 0.5 percent by weight and 2 percent by weight of the at least one cross-linking agent, on a dry weight basis.

Preferably, the cellulosic filtration material comprises at least 0.001 percent by weight of the at least one cross-linking agent, more preferably at least 0.005 percent by weight of the at least one cross-linking agent, more preferably at least 0.01 percent of the at least one cross-linking agent, more preferably at least 0.02 percent of the at least one cross-linking agent, on a dry weight basis.

Preferably, the cellulosic filtration material comprises up to 3 percent by weight of the at least one cross-linking agent, more preferably up to 2 percent by weight of the at least one cross-linking agent, more preferably up to 1 percent by weight of the at least one cross-linking agent, more preferably up to 0.1 percent by weight of the at least one cross-linking agent, on a dry weight basis.

For example, the cellulosic filtration material may comprise between 0.001 and 3 percent by weight of the at least one cross-linking agent, or between 0.005 percent by weight and 0.2 percent by weight of the at least one cross-linking agent, or between 0.01 percent by weight and 0.1 percent by weight of the at least one cross-linking agent, or between 0.02 percent by weight and 0.05 percent by weight of the at least one cross-linking agent, on a dry weight basis.

In order to prepare the additive coating, the lignin is preferably combined with the other optional components of the additive coating and formed into a slurry with water. The slurry may be heated in order to bring about any desired reactions between the components of the additive coating.

The additive coating may be applied to the regenerated cellulose or natural fibres in any suitable manner. Preferably, the additive coating is applied to the regenerated cellulose or natural fibres by spraying the additive coating onto the fibres when the fibres are being formed into the downstream element. Alternatively, the additive coating may be injected into the regenerated cellulose or natural fibres, for example, after the fibres have been formed into the downstream element. After the additive coating has been applied to the fibres, the coated fibres are preferably dried by any suitable means, including conventional heating, or microwave heating. Any curing of the additive coating may also be carried out during this drying step.

The present invention further provides a method for the production of a cellulosic filtration material for forming a downstream element of an aerosol-generating article according to the first aspect invention, as described above. The method comprises the steps of: providing a plurality of regenerated cellulose fibres; forming an additive coating solution comprising at least 5 percent by weight of exogenous lignin, on a dry weight basis and optionally one or more polysaccharides in water; applying the additive coating solution to the plurality of regenerated cellulose fibres; drying and optionally curing the coated fibres.

The step of providing the plurality of regenerated cellulose fibres may comprise forming the regenerated cellulose fibres in a spinning or extrusion process. Advantageously, the plurality of regenerated cellulose fibres may be formed in the presence of an additive enhancer, as defined above. The additive enhancer may be applied to the regenerated cellulose fibres prior to any drying of the regenerated cellulose fibres. Alternatively, the regenerated cellulose fibres may be dried prior to the application of the additive enhancer.

The present invention further provides a method for the production of a cellulosic filtration material for forming a downstream element of an aerosol-generating article according to the second aspect invention, as described above. The method comprises the steps of: providing a plurality of natural fibres; forming an additive coating solution comprising at least 5 percent by weight of exogenous lignin, on a dry weight basis and optionally one or more polysaccharides in water; applying the additive coating solution to the plurality of natural fibres; drying and optionally curing the coated fibres.

The plurality of natural fibres may be mercerised prior to the step of applying the additive coating solution. Mercerisation is a well known process for treating cellulosic natural fibres, in particular cotton fibres, in which the natural fibres are soaked in a strong alkaline solution, such as a solution of sodium hydroxide. Mercerisation of natural fibres is known to improve the properties of the fibres and in relation to the present invention, may advantageously improve the adhesion of the additive coating on the surface of the fibres. The mercerisation of the fibres additionally improves the hydrophobicity of the cellulose fibrous material.

Advantageously, the plurality of natural fibres may be treated with an additive enhancer, as defined above, prior to the application of the additive coating.

In all methods according to the invention, the additive coating solution is formed by combining the dry ingredients of the additive coating and dispersing or dissolving them in water. The dry ingredients include exogenous lignin, optionally one or more polysaccharides and optionally one or more cross-linking agents, as described above. The additive coating solution may optionally be heated prior to application of the solution to the regenerated cellulose or natural fibres, for example, in order to bring about any necessary reactions between the components of the additive coating.

The step of applying the additive coating solution to the regenerated cellulose or natural fibres may comprise spraying the additive coating solution onto the surface of the plurality of regenerated cellulose or natural fibres.

The step of drying and optionally curing the coated fibres may comprise heating the coated fibres using a conventional heater. Alternatively or in addition, the step of drying and optionally curing the coated fibres may comprise heating the coated fibres by microwave heating. The drying and optional curing of the additive coating solution is carried out in order to evaporate the water from the solution and to bring about curing and hardening of the additive coating.

Preferably, the downstream element of aerosol-generating articles according to the present invention comprises a segment of the cellulosic filtration material circumscribed by a wrapper, such as a paper wrapper. The segment of the cellulosic filtration material is preferably in the form of a solid plug. Alternatively, as described in more detail below, the segment of the cellulosic filtration material may be in the form of a hollow tubular segment.

The wrapper circumscribing the cellulosic filtration material may have a basis weight of at least 50 grams per square metre (gsm). Where the downstream element is positioned at the downstream end of the aerosol-generating article, this may help to provide a desired firmness for the aerosol-generating article. In certain embodiments, it may be desirable to use a stiff wrapper, for example, a wrapper having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm.

Preferably, the downstream element comprising the cellulosic filtration material has an average radial hardness of at least 75 percent, more preferably at least 80 percent, more preferably at least 85 percent. Preferably, the downstream element has a radial hardness of less than 100 percent, more preferably less than 95 percent. This can provide an aerosol-generating article having a downstream end with a satisfactory hardness for the consumer.

As used herein, the term “radial hardness” refers to resistance to compression is a direction transverse to a longitudinal axis. Radial hardness of an aerosol-generating article around a filter may be determined by applying a load across the article at the location of the filter, transverse to the longitudinal axis of the article, and measuring the average (mean) depressed diameters of the articles. Radial hardness is given by:

Radial ⁢ hardness ⁢ ( % ) = D d D S * 100 ⁢ %

where D_s is the original (undepressed) diameter, and D_d is the depressed diameter after applying a set load for a set duration. The harder the material, the closer the hardness is to 100%.

To determine the hardness of a portion (such as a filter) of an aerosol-generating article, 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 Densimeter device (manufactured and made commercially available by Heinr. Borgwaldt GmbH, Germany), which is fitted with a measuring head for aerosol-generating articles, such as cigarettes, and with an aerosol-generating article receptacle.

For the standard operating procedure for such an apparatus, an overall load of 2 kg is applied for a duration of 20 seconds. After 20 seconds have elapsed (and with the load still being applied to the smoking articles), the depression in the load applying cylindrical rods is determined, and then used to calculate the hardness from the above equation. The temperature is kept in the region of 22 degrees Centigrade±2 degrees. The test described above is referred to as the DD60A Test. The standard way to measure the filter hardness is when the aerosol-generating articles have not been consumed. Additional information regarding measurement of average radial hardness can be found in, for example, U.S. Published Patent Application Publication Number 2016/0128378.

As described above, the downstream element comprising the cellulosic filtration material advantageously provides improved biodegradability compared to conventional cellulose acetate segments.

Preferably, the downstream element is substantially free from cellulose acetate.

As described briefly above, the downstream element is provided downstream of the aerosol-generating substrate and in axial alignment with the aerosol-generating substrate.

In some embodiments, the aerosol-generating article is formed essentially of an aerosol-generating substrate and of a downstream element as described above provided in abutting arrangement with the rod of aerosol-generating substrate. For example, the aerosol-generating substrate may be in the form of a cylindrical rod of shredded tobacco material circumscribed by a wrapper, and the downstream element may be attached to the wrapped rod by a band of tipping paper so as to form a mouthpiece of the aerosol-generating article.

In other embodiments, the aerosol-generating article comprises one or more additional elements also provided downstream of the aerosol-generating substrate and in axial alignment with the aerosol-generating substrate. The downstream element and any further element provided downstream of the aerosol-generating substrate and in axial alignment with the aerosol-generating substrate form a downstream section of the aerosol-generating article.

In some preferred embodiments, the downstream element is a mouthpiece element.

The aerosol-generating article may comprise a mouthpiece at the downstream end or mouth end or proximal end of the aerosol-generating article, the mouthpiece consisting of the downstream element alone.

Alternatively, the aerosol-generating article may comprise a mouthpiece at the downstream end or mouth end or proximal end of the aerosol-generating article, the mouthpiece including the downstream element and one or more further elements axially aligned in an abutting end to end relationship with each other. The downstream element and the one or more further elements may be formed of the same material. Alternatively, the one or more further elements may be formed of a material other than the material of the downstream element.

Parameters or characteristics described herein in relation to the downstream element used as the sole component of the mouthpiece may equally be applied to a downstream element used as one of multiple components of the mouthpiece.

Advantageously, aerosol-generating articles according to the present invention wherein the downstream element is a mouthpiece element provide an acceptable visual impact and tactile experience for the consumer, thanks to the density and firmness of the downstream element. Additionally, in aerosol-generating articles according to the present invention wherein the downstream element is a mouthpiece element, the cellulosic filtration material is capable of efficiently reducing undesirable compounds (for example, phenols) from the aerosol generated from the substrate, with little to no impact on the taste perceived by the consumer during use of the aerosol-generating article. As such, aerosol-generating articles according to the present invention wherein the downstream element is a mouthpiece element provide a much more sustainable alternative to aerosol-generating articles comprising a cellulose acetate filter segment as a mouthpiece filter segment.

The mouthpiece element may have a low particulate phase filtration efficiency or even substantially no particulate phase filtration efficiency. Whilst capable of preventing substrate material from the aerosol-generating substrate potentially reaching the mouth of the consumer during use, a mouthpiece element having low particulate phase filtration efficiency has a reduced impact on delivery of aerosol species to the consumer. This is especially advantageous in aerosol-generating article wherein the aerosol-generating substrate is heated as opposed to being combusted.

In preferred embodiments, the particulate phase filtration efficiency of the downstream element is less than about 30 percent, more preferably less than about 20 percent.

In some embodiments, the mouthpiece element may have an RTD of less than or equal to about 25 millimetres H₂O, less than or equal to about 20 millimetres H₂O, or less than or equal to about 15 millimetres H₂O. In such embodiments, the mouthpiece element may have an RTD of at least about 10 millimetres H₂O.

The mouthpiece element may have an RTD of between about 10 millimetres H₂O and to about 25 millimetres H₂O, between about 10 millimetres H₂O and to about 20 millimetres H₂O, or of between about 10 millimetres H₂O and to about 15 millimetres H₂O.

Preferably, the mouthpiece element has a substantially circular cross-section.

Preferably, the mouthpiece element has an external diameter that is substantially the same as the external diameter of the aerosol-generating article.

A length of the mouthpiece may be at least about 3 millimetres, or at least about 5 millimetres.

The length of the mouthpiece element may be less than or equal to about 11 millimetres, or less than or equal to about 9 millimetres.

The length of the mouthpiece element may be between about 3 millimetres and about 11 millimetres, or between about 3 millimetres and about 9 millimetres. The length of the mouthpiece element may be between about 5 millimetres and about 11 millimetres, or between about 5 millimetres and about 9 millimetres. For example, the length of the mouthpiece element may be about 7 millimetres.

The length of the mouthpiece element may be selected based on a desired total length of the aerosol-generating article.

The mouthpiece element may be circumscribed by a plug wrap.

The mouthpiece element may be unventilated such that air does not enter the aerosol-generating article along the mouthpiece element.

The mouthpiece element may be connected to one or more adjacent components of the aerosol-generating article by means of a tipping wrapper.

The aerosol-generating article may define a mouth end cavity at the downstream end of the aerosol-generating article. For example, the mouthpiece element may itself be in the form of a hollow tubular element. As an alternative, the mouthpiece may include a non-hollow downstream element as described above immediately upstream of a hollow tubular segment provided at the downstream end of the mouthpiece. As a further alternative, the mouth end cavity may be defined by an outer wrapper of the mouthpiece extending beyond a downstream end of a downstream element as described above.

In some embodiments, the downstream element may be an additional element provided downstream of the aerosol-generating substrate other than a mouthpiece element. That is, the aerosol-generating article comprises a mouthpiece and the downstream element is provided between the aerosol-generating substrate and a mouthpiece of the aerosol-generating article.

For example, the downstream element may be a support element provided immediately downstream of the aerosol-generating substrate, preferably adjacent to the aerosol-generating substrate. One such support element is adapted to impart structural strength to the aerosol-generating article. The support element is advantageously configured to resist downstream movement of the aerosol-generating substrate during insertion of the heating element of the aerosol-generating device into the aerosol-generating.

In some embodiments, the downstream element may form part of an aerosol-cooling element provided downstream of the aerosol-generating substrate, the aerosol-cooling element being adapted to facilitate cooling of the aerosol generated during use of the aerosol-generating article prior to reaching the downstream end of the aerosol-generating article.

The aerosol-cooling element preferably has a low resistance to draw. That is, the aerosol-cooling element preferably offers a low resistance to the passage of air through the aerosol-generating article. Preferably, the aerosol-cooling element does not substantially affect the resistance to draw of the aerosol-generating article.

At least one of the support element and the aerosol-cooling element may be in the form of a hollow tubular element formed of the cellulosic filtration material described above. In some embodiments, both the support element and the aerosol-cooling element are in the form of hollow tubular elements, which may differ in length, internal diameter or both.

In an aerosol-generating article in accordance with the present invention, such a hollow tubular element provides an unrestricted flow channel. This means that the hollow tubular element provides a negligible level of RTD. As used herein with reference to the invention, the term “negligible level of RTD” is used to describe an RTD of less than 1 mm H₂O per 10 millimetres of length of the hollow tubular substrate element, less than 0.4 mm H₂O per 10 millimetres of length of the hollow tubular substrate element, or less than 0.1 mm H₂O per 10 millimetres of length of the hollow tubular substrate element. The flow channel should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. Preferably, the flow channel is substantially empty.

The hollow tubular element may have a total length of at least about 10 millimetres, at least about 12 millimetres, or at least about 15 millimetres.

The hollow tubular element may have a total length of less than or equal to about 30 millimetres, less than or equal to about 25 millimetres, or less than or equal to about 23 millimetres.

The hollow tubular element may have a total length of between about 10 millimetres and about 30 millimetres, between about 10 millimetres and about 25 millimetres, or between about 10 millimetres and about 23 millimetres. The hollow tubular element may have a total length of between about 12 millimetres and about 30 millimetres, between about 12 millimetres and about 25 millimetres, or between about 12 millimetres and about 23 millimetres. The hollow tubular element may have a total length of between about 12 millimetres and about 30 millimetres, between about 12 millimetres and about 25 millimetres, or between about 12 millimetres and about 23 millimetres.

The total length of the hollow tubular element or elements may be selected based on a desired total length of the aerosol-generating article.

In some embodiments, a ventilation zone may be provided at a location downstream of the aerosol-generating substrate.

By way of example, cooling of a stream of smoke generated upon combusting the aerosol-generating substrate may be achieved by providing a ventilation zone at a location along a mouthpiece of the aerosol-generating article.

As another example, a ventilation zone may be provided at a location along the hollow tubular element forming the cooling element. Without wishing to be bound by theory, the temperature drop caused by the admission of cooler, external air into the aerosol-generating article downstream of the aerosol-generating element via the ventilation zone may have an advantageous effect on the nucleation and growth of aerosol particles.

The ventilation zone may comprise a plurality of perforations, for example provided through a tubular wall of the hollow tubular element. The ventilation zone may comprise at least one circumferential row of perforations. The ventilation zone may comprise two circumferential rows of perforations. Each circumferential row of perforations may comprise from 8 to 30 perforations.

In some embodiments, the downstream section of the aerosol-generating article may comprise, in sequential order, a support element, an aerosol-cooling element, and a mouthpiece. Preferably, one or more of the support element, aerosol-cooling element, and mouthpiece are in the form of a downstream element as described above.

In some embodiments, the aerosol-generating article comprises an upstream section located upstream of the aerosol-generating substrate. The upstream section is preferably located immediately upstream of the aerosol-generating substrate. The upstream section preferably extends from an upstream end of the aerosol-generating article to an upstream end of the aerosol-generating substrate. The upstream section preferably comprises an upstream element located immediately upstream of the rod of aerosol-generating substrate.

Where the aerosol-generating substrate comprises shredded tobacco, such as tobacco cut filler, the upstream section or element thereof may additionally help to prevent the loss of loose particles of tobacco from the upstream end of the article.

The upstream section, or upstream element thereof, may also additionally provide a degree of protection to the aerosol-generating substrate during storage, as it covers at least to some extent the upstream end of the aerosol-generating substrate, which may otherwise be exposed. For aerosol-generating articles that are intended to be inserted into a cavity in an aerosol-generating device such that the aerosol-generating substrate can be externally heated within the cavity, the upstream section, or upstream element thereof, may advantageously facilitate the insertion of the upstream end of the article into the cavity.

An upstream element of the upstream section may be made of any material suitable for use in an aerosol-generating article. Suitable materials for forming the upstream element include filter materials, ceramic, polymer material, cellulose acetate, cardboard, zeolite or aerosol-generating substrate.

In preferred embodiments, the upstream element may comprise a cellulosic filtration material comprising: a fibrous material comprising a plurality of regenerated cellulose fibres, wherein the regenerated cellulose fibres are one or more of viscose fibres, modal fibres, Lyocell fibres and viscose rayon fibres; and an additive coating applied to the plurality of regenerated cellulose fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis. For example, the upstream element may be formed of the same cellulosic filtration material as the downstream element described above in relation to the first aspect of the invention.

In other preferred embodiments, the upstream element may comprise a cellulosic filtration material comprising: a fibrous material comprising a plurality of natural fibres, wherein the natural fibres are one or more of flax fibres, hemp fibres, jute fibres, kenaf fibres, ramie fibres, abaca fibres, phormium fibres, sisal fibres, coir fibres, cotton fibres, and kapok fibres; and an additive coating applied to the plurality of natural fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis. For example, the upstream element may be formed of the same cellulosic filtration material as the downstream element described above in relation to the second aspect of the invention.

From an environmental perspective, this is advantageous in that a greater portion of the aerosol-generating article as a whole is more readily degradable. Additionally, from a manufacturing viewpoint, it is advantageous to form different components of a same aerosol-generating article of the same material, as it will generally require less adjustments to the settings of existing apparatus.

Preferably, the upstream section, or an upstream element thereof, has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. Preferably, the external diameter of the upstream section, or an upstream element thereof, is between about 6 millimetres and about 8 millimetres, more preferably between about 7 millimetres and about 7.5 millimetres. Preferably, the upstream section or an upstream element has an external diameter that is about 7.1 millimetres.

Preferably, the upstream section or an upstream element has a length of between about 2 millimetres and about 8 millimetres, more preferably between about 3 millimetres and about 7 millimetres, more preferably between about 4 millimetres and about 6 millimetres. In a particularly preferred embodiment, the upstream section or an upstream element has a length of about 5 millimetres. The length of the upstream section or an upstream element can advantageously be varied in order to provide the desired total length of the aerosol-generating article.

The upstream section is preferably circumscribed by a wrapper, such as a plug wrap. The wrapper circumscribing the upstream section may be a stiff plug wrap, for example, a plug wrap having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm. This provides increased structural rigidity to the upstream section.

The upstream section is preferably connected to the rod of aerosol-generating substrate and optionally at least a part of the downstream section by means of an outer wrapper.

The aerosol-generating article may be a combustible smoking article. A combustible smoking article typically comprises a cylindrical rod of tobacco cut filler surrounded by a paper wrapper and a cylindrical filter axially aligned, most often in an abutting end-to-end relationship, with the wrapped tobacco rod. The cylindrical filter typically comprises one or more plug elements of a fibrous filtration material circumscribed by a paper plug wrap. The wrapped tobacco rod and the filter are typically joined by a band of tipping wrapper, that circumscribes the entire length of the filter and an adjacent portion of the wrapped tobacco rod. In combustible smoking articles according to the present invention, the cylindrical filter comprises a downstream element having the characteristics described above.

The aerosol-generating article may be an aerosol-generating article for generating an aerosol upon heating (a heated aerosol-generating article). A heated aerosol-generating article typically comprises a cylindrical rod of aerosol-generating substrate surrounded by a paper wrapper and a downstream section downstream of the rod of aerosol-generating substrate. The downstream section typically comprises at least one hollow tubular element immediately downstream of the rod of aerosol-generating substrate and a mouthpiece.

The aerosol-generating article preferably has an overall length of from 40 millimetres to 80 millimetres, or from 40 millimetres to about 70 millimetres, or from 40 millimetres to about 60 millimetres, or from 45 millimetres to about 80 millimetres, or from about 45 millimetres to about 70 millimetres, or from 45 millimetres to 60 millimetres, or from 50 millimetres to 80 millimetres, or from 50 millimetres to about 70 millimetres or from about 50 millimetres to about 60 millimetres. In an exemplary embodiment, an overall length of the aerosol-generating article is about 45 millimetres.

Preferably, the aerosol-generating article has a substantially circular cross-section.

The aerosol-generating article preferably has an external diameter of from about 5 millimetres to about 12 millimetres, or from about 6 millimetres to about 12 millimetres, or from about 7 millimetres to about 12 millimetres, or from about 5 millimetres to about 10 millimetres, or from about 6 millimetres to about 10 millimetres, or from about 7 millimetres to about 10 millimetres, or from about 5 millimetres to about 8 millimetres, or from about 6 millimetres to about 8 millimetres, or from about 7 millimetres to about 8 millimetres. In other embodiments, the aerosol-generating article has an external diameter of less than 7 millimetres.

The overall RTD of the aerosol-generating article is preferably at least 10 millimetres H₂O, more preferably at least 15 millimetres H₂O, more preferably at least 20 millimetres H₂O, more preferably at least 25 millimetres H₂O, more preferably at least 30 millimetres H₂O.

The overall RTD of the aerosol-generating article is preferably no more than 70 millimetres H₂O, more preferably no more than 60 millimetres H₂O, more preferably no more than 55 millimetres H₂O, more preferably no more than 50 millimetres H₂O, more preferably no more than 45 millimetres H₂O.

For example, the overall RTD of the aerosol-generating article may be between 10 millimetres H₂O and 70 millimetres H₂O, or between 15 millimetres H2O and 60 millimetres H₂O, or between 20 millimetres H₂O and 55 millimetres H₂O, or between 25 millimetres H₂O and 45 millimetres H₂O, or between 30 millimetres H₂O and 45 millimetres H₂O.

As described above, an aerosol-generating article in accordance with the present invention comprises an aerosol-generating substrate. In several embodiments, the aerosol-generating article comprises a rod of aerosol-generating substrate circumscribed by a rod plug wrap.

Preferably, the rod of aerosol-generating substrate has a length of at least 8 millimetres, more preferably a length of at least 9 millimetres, more preferably a length of at least 10 millimetres. Preferably, the length of the rod of aerosol-generating substrate is less than 16 millimetres, more preferably less than 15 millimetres, more preferably less than 14 millimetres. For example, the rod of aerosol-generating substrate may have a length of between 8 millimetres and 16 millimetres, or between 9 millimetres and 15 millimetres, or between 10 millimetres and 14 millimetres. In a particularly preferred embodiment, the rod of aerosol-generating substrate has a length of about 12 millimetres.

Preferably, the ratio between the length of the rod of aerosol-generating substrate and the overall length of the aerosol-generating article is at least 0.10, more preferably at least 0.15, more preferably at least 0.20, more preferably at least 0.25. Preferably, the ratio between the length of the rod of aerosol-generating substrate and the overall length of the aerosol-generating article is less than 0.50, more preferably less than 0.45, more preferably less than 0.40, more preferably less than 0.35. For example, the ratio between the length of the rod of aerosol-generating substrate and the overall length of the aerosol-generating article may be between 0.1 and 0.5, or between 0.15 and 0.45, or between 0.2 and 0.4, or between 0.25 and 0.35.

Preferably, the rod of aerosol-generating substrate has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

Preferably, the rod of aerosol-generating substrate has an external diameter of at least 5 millimetres, more preferably at least 6 millimetres, more preferably at least 7 millimetres. Preferably, the rod of aerosol-generating substrate has an external diameter of less than 12 millimetres, more preferably less than 10 millimetres, more preferably less than 8 millimetres. For example, the external diameter may be between 5 millimetres and 12 millimetres, or between 6 millimetres and 10 millimetres, or between 7 millimetres and 8 millimetres. In a particularly preferred embodiment, the rod of aerosol-generating substrate has an external diameter of about 7.1 millimetres.

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

The aerosol-generating substrate may have a density of at least about 150 milligrams per cubic centimetre, at least about 175 milligrams per cubic centimetre, at least about 200 milligrams per cubic centimetre, or at least about 250 milligrams per cubic centimetre.

The aerosol-generating substrate may have a density of less than or equal to about 500 milligrams per cubic centimetre, less than or equal to about 450 milligrams per cubic centimetre, less than or equal to about 400 milligrams per cubic centimetre, or less than or equal to about 350 milligrams per cubic centimetre.

The RTD of the rod of aerosol-generating substrate may be at least about 4 millimetres H₂O, at least about 5 millimetres H₂O, or at least about 6 millimetres H₂O.

The RTD of the rod of aerosol-generating substrate may be less than or equal to about 10 millimetres H₂O, less than or equal to about 9 millimetres H₂O, or less than or equal to about 8 millimetres H₂O.

The aerosol-generating substrate may be a solid aerosol-generating substrate. Suitable types of materials for use in the aerosol-generating substrate are described below and include, for example, tobacco cut filler, homogenised tobacco material such as cast leaf, aerosol-generating films and gel compositions.

The aerosol-generating substrate preferably comprises an aerosol former. Suitable aerosol formers are for example: polyhydric alcohols such as, for example, triethylene glycol, 1,3-butanediol, propylene glycol and glycerine; esters of polyhydric alcohols such as, for example, glycerol mono-, di- or triacetate; aliphatic esters of mono-, di- or polycarboxylic acids such as, for example, dimethyl dodecanedioate and dimethyl tetradecanedioate; and combinations thereof.

Preferably, the aerosol former comprises one or more of glycerine and propylene glycol. The aerosol former may consist of glycerine or propylene glycol or of a combination of glycerine and propylene glycol.

In certain embodiments, the aerosol-generating substrate preferably comprises at least 5 percent by weight of aerosol former on a dry weight basis of the aerosol-generating substrate, more preferably at least 10 percent by weight on a dry weight basis, more preferably at least 15 percent by weight on a dry weight basis. In such embodiments, the aerosol-generating substrate preferably comprises no more than 30 percent by weight of aerosol former on a dry weight basis of the aerosol-generating substrate, more preferably no more than 25 percent by weight on a dry weight basis, more preferably no more than 20 percent by weight on a dry weight basis. For example, the aerosol former content of the aerosol-generating substrate may be between 5 percent and 30 percent by weight, or between 10 percent and 25 percent by weight, or between about 15 percent and about 20 percent by weight, on a dry weight basis. In such embodiments, the aerosol former content is therefore relatively low.

In other embodiments, the aerosol-generating substrate preferably comprises at least 40 percent by weight of aerosol former on a dry weight basis of the aerosol-generating substrate, more preferably at least 45 percent by weight on a dry weight basis, more preferably at least 50 percent by weight on a dry weight basis. In such embodiments, the aerosol-generating substrate preferably comprises no more than 80 percent by weight of aerosol former on a dry weight basis of the aerosol-generating substrate, more preferably no more than 75 percent by weight on a dry weight basis, more preferably no more than 70 percent by weight on a dry weight basis. For example, the aerosol former content of the aerosol-generating substrate may be between 40 percent and 80 percent by weight, or between 45 percent and 75 percent by weight, or between about 50 percent and about 70 percent by weight, on a dry weight basis. In such embodiments, the aerosol former content is therefore relatively high.

In some preferred embodiments, the aerosol-generating substrate comprises tobacco material. For example, the aerosol-generating substrate may comprise shredded tobacco material. For example, the shredded tobacco material may be in the form of cut filler, as described in more detail below. Alternatively, the shredded tobacco material may be in the form of a shredded sheet of homogenised tobacco material. Suitable homogenised tobacco materials for use in the present invention are described below.

Within the context of the present specification, the term “cut filler” is used to describe to a blend of shredded plant material, such as tobacco plant material, including, in particular, one or more of leaf lamina, processed stems and ribs, homogenised plant material.

The cut filler suitable to be used with the present invention generally may resemble cut filler used for conventional smoking articles. The cut width of the cut filler preferably may be between 0.3 millimetres and 2.0 millimetres, or between 0.5 millimetres and 1.2 millimetres, or between 0.6 millimetres and 0.9 millimetres.

Preferably, the strands have a length of between about 10 millimetres and about 40 millimetres before the strands are collated to form the rod of aerosol-generating substrate.

Preferably, the cut filler is soaked with the aerosol former. Soaking the cut filler can be done by spraying or by other suitable application methods. Preferably, the aerosol former in the cut filler comprises one or more of glycerol and propylene glycol. The aerosol former may consist of glycerol or propylene glycol or of a combination of glycerol and propylene glycol.

In other preferred embodiments, the aerosol-generating substrate comprises homogenised plant material, preferably a homogenised tobacco material.

As used herein, the term “homogenised plant material” encompasses any plant material formed by the agglomeration of particles of plant. For example, sheets or webs of homogenised tobacco material for the aerosol-generating substrates of the present invention may be formed by agglomerating particles of tobacco material obtained by pulverising, grinding or comminuting plant material and optionally one or more of tobacco leaf lamina and tobacco leaf stems. The homogenised plant material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

The homogenised plant material can be provided in any suitable form.

In some embodiments, the homogenised plant material may be in the form of one or more sheets. As used herein with reference to the invention, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

The homogenised plant material may be in the form of a plurality of pellets or granules.

The homogenised plant material may be in the form of a plurality of strands, strips or shreds. As used herein, the term “strand” describes an elongate element of material having a length that is substantially greater than the width and thickness thereof.

The aerosol former content of the homogenised tobacco material is preferably within the ranges defined above for aerosol-generating substrate having a relatively low aerosol former content.

In other preferred embodiments, the aerosol-generating substrate is in the form of an aerosol-generating film comprising a cellulosic based film-forming agent, nicotine and the aerosol former. The aerosol-generating film may further comprise a cellulose based strengthening agent. The aerosol-generating film may further comprise water, preferably 30 percent by weight of less of water.

As used herein, the term “film” is used to describe a solid laminar element having a thickness that is less than the width or length thereof. The film may be self-supporting.

In the context of the present invention the term “cellulose based film-forming agent” is used to describe a cellulosic polymer capable, by itself or in the presence of an auxiliary thickening agent, of forming a continuous film. Preferably, the cellulose based film-forming agent is selected from the group consisting of hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), hydroxyethyl methyl cellulose (HEMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and combinations thereof. In particularly preferred embodiments, the cellulose based film-forming agent is HPMC.

The aerosol former content of the aerosol-generating film is within the ranges defined above for aerosol-generating substrates having a relatively high aerosol former content.

Suitable aerosol-generating films for use as the aerosol-generating substrate of aerosol-generating articles according to the invention are described in WO-A-2020/207733 and WO-A-2022/074157.

Preferably, the aerosol-generating film comprises between 0.5 percent and 10 percent by weight of nicotine, or between 1 percent and 8 percent by weight of nicotine, or between 2 percent and 6 percent by weight of nicotine, on a dry weight basis.

The aerosol-generating film may be a substantially tobacco-free aerosol-generating film.

In alternative embodiments of the invention, the aerosol-generating substrate may comprise a gel composition that includes nicotine, at least one gelling agent and the aerosol former. The gel composition is preferably substantially tobacco free.

The preferred weight ranges for nicotine in the gel composition are the same as those defined above in relation to aerosol-generating films.

Suitable gel compositions for use as the aerosol-generating substrate of aerosol-generating articles according to the invention are described in WO-A-2021/170642.

The gel composition preferably comprises at least 50 percent by weight of aerosol former, more preferably at least 60 percent by weight, more preferably at least 70 percent by weight of aerosol former, on a dry weight basis. The gel composition may comprise up to 80 percent by weight of aerosol former. The aerosol former in the gel composition is preferably glycerol.

In certain embodiments of the invention, the aerosol-generating article further comprises one or more elongate susceptor elements within the rod of aerosol-generating substrate. For example, one or more elongate susceptor elements may be arranged substantially longitudinally within the rod of aerosol-generating substrate and in thermal contact with the aerosol-generating substrate.

As used herein with reference to the present invention, the term “susceptor element” refers to a material that can convert electromagnetic energy into heat.

Suitable susceptor elements for use in the aerosol-generating substrate of aerosol-generating articles according to the present invention are described in WO-A-2021/170673.

Preferably, the rod of aerosol-generating substrate is circumscribed by a wrapper. The wrapper may be a paper wrapper or a non-paper wrapper.

Suitable paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps. Suitable non-paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to sheets of homogenised tobacco materials.

According to a second aspect of the present invention, there is provided an aerosol-generating system comprising: an aerosol-generating article according to the first aspect of the invention; and an aerosol-generating device configured to heat the aerosol-generating substrate of the aerosol-generating article.

The aerosol-generating device comprises means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate. Preferably, the aerosol-generating device comprises a housing defining a cavity configured to receive the aerosol-generating article, and means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate when the aerosol-generating article is received within the cavity.

The aerosol-generating device may be a handheld aerosol-generating device.

The aerosol-generating device may be an electrically-operated aerosol-generating device.

The aerosol-generating device may comprise a power supply and control electronics.

The aerosol-generating device may comprise a battery and control electronics.

The aerosol-generating device may be configured to heat the aerosol-generating substrate internally. That is, the aerosol-generating device may be configured to supply heat to the aerosol-generating substrate from a location internal to the aerosol-generating article.

For example, in some embodiments the aerosol-generating device comprises a heater element configured to be inserted into the aerosol-generating element when the aerosol-generating article is received within the cavity of the aerosol-generating device.

In other embodiments, the aerosol-generating article comprises a susceptor element provided at a location within the aerosol-generating element, and the aerosol-generating device comprises an inductor coil positioned on or within the housing, a power supply of the aerosol-generating device being connected to the inductor coil and configured to provide a high frequency oscillating current to the inductor coil.

The aerosol-generating device may be configured to heat the aerosol-generating substrate externally. That is, the aerosol-generating device may be configured to supply heat to the aerosol-generating substrate from a location external to the aerosol-generating article. For example, in some embodiments the aerosol-generating device comprises a heater element located about a perimeter of the cavity and configured to heat the aerosol-generating substrate of the aerosol-generating article from an exterior of the aerosol-generating element of the aerosol-generating article.

Examples will now be further described with reference to the drawings of the accompanying Figures in which:

FIG. 1 shows a schematic side sectional view of an aerosol-generating article in accordance with an embodiment of the invention;

FIG. 2 shows a schematic side sectional view of another aerosol-generating article in accordance with another embodiment of the invention; and

FIG. 3 shows a schematic side sectional view of another aerosol-generating article in accordance with a further embodiment of the invention.

The aerosol-generating article 1000 shown in FIG. 1 comprises an aerosol-generating element 1002 in the form of a substantially cylindrical rod 1004 of shredded tobacco circumscribed by a wrapper 1006. Further, the aerosol-generating article 1000 comprises a substantially cylindrical mouthpiece 1008 comprising a segment 1010 of a cellulosic filtration material circumscribed by a plug wrap 1012.

The mouthpiece 1008 is attached to the aerosol-generating element 1002 by a band 1014 of tipping paper. Perforations 1016 formed through the tipping paper and the plug wrap are provided to enable admission of ventilation air into the segment 1010 when the consumer draws upon the mouthpiece 1008 during use. The aerosol-generating article 1000 has a length of 70 millimetres and an external diameter of 7.6 millimetres.

The segment 1010 is in the form of a plug element comprising a cellulosic filtration material. One example of a suitable cellulosic filtration material comprises viscose fibres and an additive coating applied to the viscose fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis. A further example of a suitable cellulosic filtration material comprises cotton fibres and an additive coating applied to the cotton fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis.

The aerosol-generating article 10 shown in FIG. 2 comprises a rod 12 of aerosol-generating substrate 12 and a downstream section 14 at a location downstream of the rod 12 of aerosol-generating substrate. Further, the aerosol-generating article 10 comprises an upstream section 16 at a location upstream of the rod 12 of aerosol-generating substrate. Thus, the aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or mouth end 20, and has an overall length of about 45 millimetres.

The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of aerosol-generating substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of FIG. 2, the upstream end of the support element 18 abuts the downstream end of the rod 12 of aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol-cooling element 24 located immediately downstream of the support element 22, the aerosol-cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of FIG. 1, the upstream end of the aerosol-cooling element 24 abuts the downstream end of the support element 22. In the embodiment of FIG. 2, the support element 22 and the aerosol-cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 10.

The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of filtration material. The first hollow tubular segment 26 defines an internal cavity 28 that extends all the way from an upstream end 30 of the first hollow tubular segment to an downstream end 32 of the first hollow tubular segment 20. The internal cavity 28 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 28.

The first hollow tubular segment 26 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter of about 1.9 millimetres. Thus, a thickness of a peripheral wall of the first hollow tubular segment 26 is about 2.67 millimetres.

The aerosol-cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of filtration material. The second hollow tubular segment 34 defines an internal cavity 36 that extends all the way from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The internal cavity 36 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 36.

The second hollow tubular segment 34 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter of about 3.25 millimetres. Thus, a thickness of a peripheral wall of the second hollow tubular segment 34 is about 2 millimetres. Thus, a ratio between the internal diameter of the first hollow tubular segment 26 and the internal diameter of the second hollow tubular segment 34 is about 0.75.

The aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. In more detail, the ventilation zone is provided at about 2 millimetres from the upstream end of the second hollow tubular segment 34. A ventilation level of the aerosol-generating article 10 is about 25 percent.

In the embodiment of FIG. 2, the downstream section 14 further comprises a mouthpiece element 42 at a location downstream of the intermediate hollow section 50. In more detail, the mouthpiece element 42 is positioned immediately downstream of the aerosol-cooling element 24. As shown in the drawing of FIG. 2, an upstream end of the mouthpiece element 42 abuts the downstream end 40 of the aerosol-cooling element 18.

The mouthpiece element 42 is provided in the form of a cylindrical plug element 44 comprising a cellulosic filtration material. One example of a suitable cellulosic filtration material comprises viscose fibres and an additive coating applied to the viscose fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis. A further example of a suitable cellulosic filtration material comprises cotton fibres and an additive coating applied to the cotton fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis.

The mouthpiece element 42 has a length of about 12 millimetres and an external diameter of about 7.25 millimetres.

The rod 12 comprises an aerosol-generating substrate of one of the types described above.

The rod 12 of aerosol-generating substrate has an external diameter of about 7.25 millimetres and a length of about 12 millimetres.

The aerosol-generating article 10 further comprises an elongate susceptor 46 within the rod 12 of aerosol-generating substrate. In more detail, the susceptor 46 is arranged substantially longitudinally within the aerosol-generating substrate, such as to be approximately parallel to the longitudinal direction of the rod 12. As shown in the drawing of FIG. 2, the susceptor 46 is positioned in a radially central position within the rod and extends effectively along the longitudinal axis of the rod 12. In more detail, the susceptor 46 is in thermal contact with the aerosol-generating substrate. The susceptor 46 extends all the way from an upstream end to a downstream end of the rod 12. In effect, the susceptor 46 has substantially the same length as the rod 12 of aerosol-generating substrate.

In more detail, in the embodiment of FIG. 2, the susceptor 46 is provided in the form of a strip and has a length of about 12 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

The upstream section 16 comprises an upstream element 48 located immediately upstream of the rod 12 of aerosol-generating substrate, the upstream element 48 being in longitudinal alignment with the rod 12. In the embodiment of FIG. 2, the downstream end of the upstream element 48 abuts the upstream end of the rod 12 of aerosol-generating substrate. This advantageously prevents the susceptor 46 from being dislodged. Further, this ensures that the consumer cannot accidentally contact the heated susceptor 46 after use.

The upstream element 48 comprises a segment of material 50 in the form of a cylindrical plug of filtration material and a first wrapper 52 circumscribing the segment of material 50. The segment of material 50 has a length of about 5 millimetres. The RTD of the segment of material 50 is about 30 millimetres H₂O.

The aerosol-generating article 10 further comprises a combining wrapper 54 which attaches the upstream element 48 to the remaining components of the aerosol-generating article. In the embodiment of FIG. 2 a single combining wrapper 54 is depicted, which circumscribes and holds together the upstream element 48, the rod 12, and the downstream section 14 to form the aerosol-generating article.

However, it will be clear that alternative configurations are possible, wherein two or more combining wrappers are employed to assemble the different components of the aerosol-generating article. For example, a first combining wrapper could be used to attach the support element 22 to the aerosol-cooling element 24, and the resulting assembly could then be attached by means of a second combining wrapper to the upstream section 16 and the rod 12. The resulting combination of components could then be attached to the mouthpiece element 42 By means of a tipping wrapper. As shown in the drawing of FIG. 1, the aerosol-generating article 10 further comprises a wrapper 70 circumscribing the rod 12 of aerosol-generating substrate. The wrapper 70 is separate and distinct from the first wrapper 52 circumscribing the segment of material 50. Neither one of the first wrapper 52 and the wrapper 70 comprises a metallic foil.

In the aerosol-generating article 10 of FIG. 2, one or more of the first hollow tubular segment 26 of the support element 22, the second hollow tubular segment 34 of the aerosol-cooling element 24, and the segment of material 50 of the upstream element 48 may be made of the same material according to the present invention used in the mouthpiece element 42.

The aerosol-generating article 100 shown in FIG. 3 comprises a rod of aerosol-generating substrate 112 and a downstream section 114 at a location downstream of the rod 112 of aerosol-generating substrate. Additionally, the aerosol-generating article 100 comprises an upstream section 116. Thus, the aerosol-generating article 100 extends from an upstream or distal end 118—which substantially coincides with an upstream end of the upstream section 116—to a downstream or mouth end 120, which coincides with a downstream end of the downstream section 114. The downstream section 114 comprises a hollow tubular element 122 and a mouthpiece element 150. The upstream section 116 comprises an upstream plug element 124.

The aerosol-generating article 100 has an overall length of about 45 millimetres and an outer diameter of about 7.2 mm.

The rod of aerosol-generating substrate 112 comprises a shredded tobacco material. The rod of aerosol-generating substrate 112 comprises 150 milligrams of a shredded tobacco material comprising from 13 percent by weight to 16 percent by weight of glycerine. The density of the aerosol-generating substrate is about 300 mg per cubic centimetre. The RTD of the rod of aerosol-generating substrate 112 is between about 6 to 8 mm H₂O. The rod of aerosol-generating substrate 112 is individually wrapped by a plug wrap (not shown).

The hollow tubular element 122 is located immediately downstream of the rod 112 of aerosol-generating substrate, the hollow tubular element 122 being in longitudinal alignment with the rod 112. The upstream end of the hollow tubular element 122 abuts the downstream end of the rod 112 of aerosol-generating substrate.

The hollow tubular element 122 defines a hollow section of the aerosol-generating article 110. The hollow tubular element 122 does not substantially contribute to the overall RTD of the aerosol-generating article. In more detail, an RTD of the hollow tubular element 122 is about 0 mm H₂O.

As shown in FIG. 3, the hollow tubular element 122 is provided in the form of a hollow cylindrical tube made of cardboard. The hollow tubular element 122 defines an internal cavity that extends all the way from an upstream end of the hollow tubular element 122 to a downstream end of the hollow tubular element 122. The internal cavity is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity.

The hollow tubular element 122 has a length of about 21 millimetres, an external diameter of about 7.2 millimetres, and an internal diameter of about 6.7 millimetres. Thus, a thickness of a peripheral wall of the hollow tubular element 122 is about 0.25 millimetres.

The aerosol-generating article 100 comprises a ventilation zone 160 provided at a location along the hollow tubular element 122. The ventilation zone 160 comprises a circumferential row of openings or perforations circumscribing the hollow tubular element 122. The perforations of the ventilation zone 160 extend through the wall of the hollow tubular element 122, in order to allow fluid ingress into the internal cavity from the exterior of the article 100. A ventilation level of the aerosol-generating article 10 is about 16 percent.

On top of a rod 112 of aerosol-generating substrate and a downstream section 14 at a location downstream of the rod 12, the aerosol-generating article 100 comprises an upstream section 140 at a location upstream of the rod 112. As such, the aerosol-generating article 10 extends from a distal end 116 substantially coinciding with an upstream end of the upstream section 140 to a mouth end or downstream end 118 substantially coinciding with a downstream end of the downstream section 114.

As described briefly above, the upstream section 116 comprises an upstream plug element 124 located immediately upstream of the rod 112 of aerosol-generating substrate, the upstream plug element 124 being in longitudinal alignment with the rod 112. The downstream end of the upstream plug element 124 abuts the upstream end of the rod 112 of aerosol-generating substrate. The upstream plug element 124 is provided in the form of a hollow cylindrical plug of filtration material having a wall thickness of about 1 mm and defining an upstream internal cavity. The upstream element 124 has a length of about 5 millimetres. An external diameter of the upstream plug element 124 is about 7.1 mm. An internal diameter of the upstream plug element 42 is about 5.1 mm.

The mouthpiece element 150 extends from the downstream end of the hollow tubular element 122 to the downstream or mouth end of the aerosol-generating article 100. The mouthpiece element 150 has a length of about 7 mm. An external diameter of the mouthpiece element 150 is about 7.2 mm.

The mouthpiece element 150 is provided in the form of a cylindrical plug element comprising a cellulosic filtration material. One example of a suitable cellulosic filtration material comprises viscose fibres and an additive coating applied to the viscose fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis. A further example of a suitable cellulosic filtration material comprises cotton fibres and an additive coating applied to the cotton fibres, the additive coating comprising at least 5 percent by weight of exogenous lignin on a dry weight basis.

In the aerosol-generating article 100 of FIG. 3, the plug element 124 of the upstream section 116 may be made of the same material according to the present invention used in the mouthpiece element 150.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A±5% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.