EP2757911A1

EP2757911A1 - Filter materials and uses thereof

Info

Publication number: EP2757911A1
Application number: EP12766471.2A
Authority: EP
Inventors: Yahia LEMMOUCHI; Michele Mola
Original assignee: British American Tobacco Investments Ltd; British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 2011-09-23
Filing date: 2012-09-21
Publication date: 2014-07-30
Also published as: GB201116425D0; US20140318561A1; CA2849204A1; BR112014006572A2; WO2013041873A1; KR20140065005A; CN103945714A; AU2012311315B2; AU2012311315A1; AR088443A1; RU2014116063A; ZA201402023B; JP2014526269A

Abstract

The present invention relates to filter materials comprising cellulose acetate and polylactide in a ratio of about 95:5 to about 75:25 by weight, and to filters (2) or filter elements comprising such filter materials. The invention also relates to smoking articles (1) comprising the filter materials, filters (2) or filter elements.

Description

Filter Materials and Uses Thereof Field

The present invention relates to filter materials. More specifically, the invention relates to filter materials that may be used to filter smoke, such as the tobacco smoke generated by smoking articles. The invention also relates to filters or filter elements comprising the filter materials, as well as to smoking articles comprising the filter materials, filters or filter elements. Background

A variety of materials have been suggested as filter materials for cigarette smoke. Cellulose acetate tow is a commonly used filter material in filters for smoking articles, where it contributes to the selective removal of particulate phase and selected semi-volatile compounds. However, cellulose acetate tow can be expensive compared to some other filter materials which may be used. It is also desirable to seek to use materials in filters which are from a sustainable source. Nevertheless, cellulose acetate is the established tow material for cigarette filters and, for consumer acceptance and potentially for any regulatory acceptance, any replacement filter material would have to have similar filtration properties and would have to provide filtered smoke with similar taste and mouthfeel characteristics.

Summary

According to a first aspect of the present invention there is provided a filter material comprising cellulose acetate and polylactide in a ratio of about 95:5 to about 75:25 by weight.

In a second aspect of the present invention, a filter or filter element for a smoking article is provided, comprising the filter material according to the first aspect. In a third aspect of the present invention, a smoking article is provided, comprising the filter material according to the first aspect or comprising the filter or filter element according to the second aspect. Brief Description of the Drawings

In order that aspects of the invention may be more fully understood, embodiments thereof will now be described by way of illustrative example with reference to the accompanying drawings.

Figure 1 is a schematic side view of a smoking article including a filter according to embodiments of the invention.

Figure 2 is a schematic cross-sectional illustration of the arrangement of the CA tow and PLA fibres in a filter or filter element according to one embodiment.

Figure 3 is a schematic cross-sectional illustration of the arrangement of the CA tow and PLA fibres in a filter or filter element according to another embodiment.

Figure 4 is a schematic cross-sectional illustration of the arrangement of the CA tow and PLA fibres in a filter or filter element according to a further embodiment. Figure 5 is a schematic cross-sectional illustration of the arrangement of the CA tow and PLA fibres in a filter or filter element according to a yet further embodiment. Figure 6 is a schematic cross-sectional illustration of the arrangement of the CA tow and a non-woven sheet of PLA in a filter or filter element according to one embodiment.

Figure 7 is a schematic cross-sectional illustration of the arrangement of the CA tow and a non-woven sheet of PLA in a filter or filter element according to an alternative embodiment.

Figure 8 is a schematic cross-sectional illustration of the arrangement of the CA tow and a non-woven sheet of PLA in a filter or filter element according to a yet further embodiment.

Figure 9 is a schematic axial cross-sectional illustration of a smoking article with a filter comprising filter material according to another embodiment of the invention. Figures 10 to 16 provide graphs showing experimental data from the studies set out in the Examples. Detailed Description

In some embodiments, the invention relates to the combination of cellulose acetate and polylactide to provide filter material. It may be desirable for the filter material to be suitable for use in a smoking article, and/ or for use in a filter or a filter element, such as may be used in a smoking article.

In some embodiments, the filter material comprises cellulose acetate and PLA in a ratio of between about 75:25 and about 95:5 by weight, a ratio of between about

75:25 and about 90:10 by weight, a ratio of between about 75:25 and about 85:15 by weight, or in a ratio of about 80:20 by weight.

The experimental data, which is discussed in detail in the Examples, demonstrates that filter materials of the present invention exhibit good filtration characteristics. It is also shown that the properties of a filter made from this material may be adjusted to produce desired smoke yields and filtration efficiency.

Cellulose Acetate

Cellulose acetate (CA) is an organic ester which is used for many industrial applications in the form of films and fibres. CA is derived from cellulose using the acetylation process and its main properties are its hardness, good resistance to impact, high shine, transparency, pleasing texture, lack of static electricity and resistance to hydrocarbons. CA has been reported to be potentially biodegradable. The biodegradation rate of CA may depend on its degree of acetyl-group substitution (DS). As the DS of CA decreases, the biodegradation rate increases. CA with a DS of less than 2.1 is considered to be biodegradable, whilst CA with a DS above 2.1 is only poorly or slowly biodegradable. The cellulose acetate (CA) used in filter materials for inclusion in smoking articles frequently has a degree of substitution (DS) of around 2.5. Whilst this relatively high DS means that CA is poorly degradable, this DS is selected as it renders the CA soluble in solvents such as acetone. Solvent solubility of the CA allows the material to be processed in useful ways, such as solvent film casting and solvent fibre spinning, which is the process used to form the fibres of the cellulose acetate tow conventionally used in the filters of smoking articles. CA for use in smoking article filters may be treated with plasticizers. This involves applying the plasticizer (usually in liquid form) to the surface of the CA fibres, for example by spraying the liquid plasticizer on to the CA tow. The plasticizer acts by binding adjacent fibres to one another at their contact points, thereby affording the filter rods sufficient hardness for cigarette manufacture and use. Thus, although the materials added to CA in this way are generally referred to as plasticizers, they are really acting as binders or hardeners rather than as plasticizers. Suitable plasticizers for this use include triacetin (glycerin triacetate), TEC (triethyl citrate) and PEG 400 (low molecular weight polyethylene glycol). Plasticized cellulose acetate tow is also known to improve the selective removal of some semi-volatile compounds found in smoke (e.g. phenol, o-cresol, p-cresol and m-cresol). For this effect, it is considered to be necessary for the plasticizer to be present on the surface of the CA fibres.

Because of the fibre-binding effect of plasticizers, CA filters generally include less than 10% plasticizer and frequently less than 7% by weight. It has been found that including plasticizer in greater amounts than this has a detrimental effect on the cellulose acetate tow, causing holes to be formed.

The types of CA discussed above may be used in the present invention. The cellulose acetate may be in the form of fibres, for example in the form of a fibrous tow. Cellulose acetate with a degree of substitution of about 2.1 to about 2.5, or of about 2.5 may used in some embodiments.

In some embodiments, the CA included in the filter materials may be modified in order to provide or enhance beneficial properties, such as degradability, filtration and/ or the taste characteristics of the filtered smoke.

For instance, cellulose acetate tow may be made from compositions comprising a blend of CA and a plasticizer, in which the plasticizer is integrated within the structure of the CA and is retained. The blend may be formed by solvent blending, wherein the CA and plasticizer are soluble in acetone or other suitable solvent and the blend composition is formed from the solution and comprises an intimate blend of CA and plasticizer. Alternatively, the CA and plasticizer may be melt blended. In another instance, the cellulose acetate tow may be made from a composition comprising a blend of cellulose acetate (which may be CA blended with a plasticizer) and a water soluble polymer, said blend being optionally compatibilized. In some embodiments, such compositions may be water dispersive and/or biodegradable. Suitable water soluble polymers include polyvinyl alcohol (PVOH), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), methyl cellulose (MC) and ethyl cellulose (EC), hydroxyethyl methacrylate (HEMA), xanthan and puUulan, or blends thereof. Suitable

compatibilizers include grafted copolymers, such as PLA-grafted water-soluble polymers, and include reactive compatibilizers such as maleic anhydride-grafted polylactide (MA-g-PLA).

Polylactide

Poly(lactic acid) or polylactide (PLA), is a biodegradable and biocompatible polymer. It is derived from renewable resources (e.g., corn, wheat, or rice) and it is biodegradable, recyclable, and compostable. In addition, PLA exhibits excellent processability. It can be processed by injection moulding, film extrusion, blow moulding, thermoforming, fibre spinning, and film forming.

The polylactide (PLA) used in the present invention may be produced by different synthetic methods, such as ring-opening polymerization of lactide or direct condensation polymerization from lactic acid. Any PLA grade can be selected for use in this invention, and the molecular weights of the PLA may vary depending on the desired properties and use. In some embodiments, poly(L-lactide) (PLLA) may be preferred due to its crystallinity, which is beneficial for the production of fibres.

The filter material of the present invention may comprise PLA in various forms, including, for example, in the form of fibres, in the form of a fibrous tow and/ or in the form of one or more non-woven sheet materials. The PLA may be present in the filter material in more than one form.

PLA Fibres Where the PLA is provided in the form of fibres, the polylactide fibres may, in one embodiment, consist essentially of polylactide.

Fibres may be manufactured from PLA in various ways including, for example, a solvent spinning process or a melt extrusion process.

In some embodiments, the filter material comprises cellulose acetate fibres and PLA fibres in a ratio of between about 75:25 and about 95:5 by weight, a ratio of between about 75:25 and about 90:10 by weight, a ratio of between about 75:25 and about 85:15, or a ratio of about 80:20 by weight.

PLA Sheet

In some embodiments of the invention, the PLA filter material may be in the form of a non-woven sheet. Non-woven sheet materials may be used as filter materials in smoking articles, for example in the form of crimped or gathered sheets.

Non-woven materials are broadly defined as sheet or web structures bonded together by entangling fibres or filaments mechanically, thermally or chemically, or by a combination of two or more of these. They tend to be flat, porous sheets that are made directly from separate fibers. They are not made by weaving or knitting and do not require converting the fibers to yarn.

Thus, in one embodiment, a filter material according to the present invention may comprise CA tow and one or more PLA non-woven sheets. The two materials may be arranged to ensure that the resultant plug of filter material exhibits sufficient hardness and structural integrity to enable it to be incorporated into a smoking article using the conventional high-speed manufacturing machinery.

Sheet materials can have certain drawbacks when used as the sole form of filter material. In order to attain the desired structural rigidity when constructing a filter element from non-woven sheet materials, the filter material must be very densely packed and this means that these filter elements have quite different properties to those made of fibrous tow. They exhibit a greater resistance to the flow of smoke, resulting in a pressure drop which is higher than that of a conventional cellulose acetate tow filter, requiring the user to draw harder on the smoking article. Perhaps more significantly, the smoke drawn through such filter material has been found to have different taste characteristics compared to the smoke drawn through conventional cellulose acetate filter material. What is more, filter elements comprising non-woven sheet materials or paper as the filter material have been shown to exhibit significantly less selective removal of particulate phase and selected semi-volatile compounds than conventional cellulose acetate tow filter materials.

In one embodiment where a non-woven PLA sheet material is included in the filter material, the sheet material includes one or more plasticizers, including PEG and/ or triacetin and/or TEC. For example, the sheet material may include PEG and one or both of triacetin and TEC. In one embodiment, the polyethylene glycol may be liquid at room temperature, such as PEG 400. In another embodiment, the polyethylene glycol may be a high molecular weight polyethylene glycol, such as one which is solid at room temperature. Such polyethylene glycols include PEG 600 and higher, and preferably PEG 1000 and higher. These particular polyethylene glycols are attractive as they are solid or semi-solid at room temperature and so their addition will not compromise the structural integrity of the non-woven sheet material. Additives which are liquid at room temperature can in some

circumstances adversely affect the structural integrity and strength of a filter element where the filter material is a non-woven sheet material, for example they may soften the non-woven material. For that reason, there may be a limit on the amount of such additives which can be included whilst still retaining the required rigidity and strength of the sheet material.

Indeed, rather than weakening the non-woven sheet filter material, the use of a high molecular weight polyethylene glycol may actually increase the structural integrity and rigidity of the filter material. This provides further flexibility when forming a filter or filter element with regard to the amount of filter material required to achieve the desired hardness and rigidity. This in turn would allow the

manufacturer to adjust the pressure drop of the filter element. This would allow a filter or filter element to be designed having properties which closely resemble those of conventional CA filter elements.

In addition, the selective removal of semi-volatile compounds provided by the addition of the PEG to the filter material is proportional to the amount of PEG included. The flexibility to add greater amounts of PEG, including high molecular weight PEG, means that the ability of the filter material to selectively remove semi- volatile compounds may be adjusted to a desirable level. In one embodiment of the present invention, the PEG is included in or on the non- woven sheet material in an amount of up to 30%, preferably up to 20%, and more preferably of 5-10% by weight of the sheet. These figures are determined by comparing the dry weight of the sheet without the PEG to the weight of the sheet including the PEG additive.

The addition of TEC and/ or triacetin has a different effect on the non-woven sheet material. These additives have been surprisingly found to have a beneficial effect on the taste and odour of the smoke which is drawn through the filter element. A common criticism of filter materials other than CA is that they tend to adversely affect smoke taste. The triacetin and TEC have different effects on the smoke's taste characteristics and the two additives may be added in differing amounts in order to produce a desirable smoke taste profile.

In conventional cellulose acetate tow used in filter material, the amount of triacetin or TEC which can be included is limited by the effect that these additives have on binding the fibres of the fibrous material, with amounts of triacetin exceeding about 7% causing holes to be formed in the cellulose acetate material. In contrast, the amount of TEC and triacetin which may be included in or on the non-woven sheet material is not so limited. Indeed, where PEG is also included which is solid at room temperature, the effect of these liquid additives in making the sheet material soggy is minimised and up to 30% by weight of TEC and/ or triacetin may be included, although amounts of up to 20% or up to about 12% by weight of the sheet material may be preferred. These figures are determined by comparing the dry weight of the sheet material without the additive to the weight of the sheet material including the additive.

Further additives can be incorporated into or onto the non-woven sheet material, including tobacco extracts, glycerine, menthol, carbon fibres, carbon particles, and the like. Such additives can be incorporated into the sheet material during its manufacture, or applied to the material after manufacture is complete.

In certain embodiments, filter materials may comprise non-woven sheet materials having a thickness greater than about 0.05 mm, preferably from about 0.06 mm to about 0.08 mm. The non-woven PLA filter materials may have a basis weight of about 15 g/m² to about 60 g/m², preferably about 20 g/m² to about 45 g/m².

The non-woven PLA sheet may be manufactured by any known process. For example, spunbond sheets are made by forming a web from extruded, spun filaments and then bonding the fibres. During the web laying process, the fibres may be separated by air jets or electrostatic charges. The bonding imparts strength and integrity to the web and may be carried out by applying heated rolls or hot needles to partially melt the polymer and fuse adjacent fibres together. Spunlacing is another process which uses high-speed jets of water to strike a web so that the fibers become knotted with one another.

Filters and Filter Elements

Filter elements and filters according to the present invention comprise the filter material according to the first aspect of the invention. These filter elements and filters may be incorporated into smoking articles.

Thus, the filter elements and filters in accordance with the invention may comprise filter material which comprises cellulose acetate and PLA in a ratio of between about 75:25 and about 95:5 by weight, a ratio of between about 75:25 and about 90:10 by weight, a ratio of between about 75:25 and about 85:15 by weight, or in a ratio of about 80:20 by weight. The cellulose acetate may be in the form of a tow. The PLA may be in the form of fibres, in the form of a fibrous tow and/ or in the form of one or more non-woven sheet materials. Referring to Figure 1, for purpose of illustration and not limitation, a smoking article 1 according to an exemplary embodiment of the invention comprises a filter 2 and a cylindrical rod of smokeable material 3, such as tobacco, aligned with the filter 2 such that one end of the smokeable material rod 3 abuts the end of the filter 2. The filter 2 is wrapped in a plug wrap (not shown) and the smokeable material rod 3 is joined to the filter 2 by tipping paper (not shown) in a conventional manner. The filter 2 is substantially cylindrical and has a mouth end 4 and a smokeable material end 5. The filter 2 comprises a plug of filter material according to the present invention, comprising cellulose acetate fibres 6 and polylactide. The plug of filter material preferably has a size and shape suitable to match the size and shape of the rod of smokeable material to which it is to be attached in a finished smoking article.

Although the illustrated smoking article 1 includes a filter 2 having a single filter element or segment comprising a blend of cellulose acetate and a water soluble polymer as described herein, other arrangements are possible. For instance, the filter 2 can comprise multiple segments, such as 2, 3 or more segments, with some or all of the segments comprising filter material according to the invention. Many different filter arrangements for smoking articles are contemplated, including composite filters wherein the filter comprises a plurality of separate filter elements or sections with different filtering capacities, and/ or comprising different materials, such as different filter materials and additives, such as adsorbents and flavourants. As used herein, the term "flavourant" refers to materials which, where local regulations permit, may be used to create a desired taste or aroma in a product. Where the filter material comprises PLA in the form of fibres, the CA tow and PLA fibres may be provided in the form of a homogenous mixture, with the PLA fibres dispersed throughout the fibres of the CA tow. In alternative embodiments, the PLA fibres are arranged in a tow and the filter material comprises one or more zones of PLA tow and one or more zones of CA tow. Some of the possible arrangements of these zones are illustrated in Figures 2 to 5. In one embodiment, as illustrated in Figure 2, the filter plug 10 is made up of PLA tow 12 arranged as a central core, surrounded by an outer layer of CA tow 11, the filter material in turn being surrounded by a plug wrap 14. In an alternative embodiment (not shown in the figures), the central core is made up of CA tow and the surrounding material is PLA tow made up of PLA fibres.

In other embodiments, as illustrated in Figures 3 and 4, the PLA tow is provided in multiple regions. In Figure 3, the PLA tow 12 is provided as multiple zones which are surrounded by CA tow. The zones are shown as having a circular cross-section, but other shapes may be used. The number, size and the shape of the zones may vary. The zones may extend longitudinally along the entire length of the filter plug, or only along part of it. In Figure 4, the PLA tow 12 is provided in radially extending zones, with CA tow 11 positioned between said zones.

In a further possible configuration, as illustrated in Figure 5, the PLA tow is provided in the form of a layer of tow 12 which is embedded within the CA tow 11 so that the layer of PLA tow 12 is arranged in a spiral configuration, wrapped around the longitudinal axis of the filter. A layer of PLA tow may be incorporated into the filter plug in other ways. According to some embodiments, the filter material comprises PLA in the form of a non-woven sheet material in combination with CA tow. Some of the possible arrangements of this combination of PLA sheet and CA tow are illustrated in Figures 6 to 8. In one embodiment, as illustrated in Figure 6, the filter plug 10 is made up of PLA sheet 13 packed to form a central core, surrounded by an outer layer of CA tow 11. The zones are shown as having a circular cross-section, but other shapes may be used. In an alternative embodiment, as shown in Figure 7, the central core is made up of CA tow 11 and the surrounding material is formed from one or more PLA sheets 13.

Various alternative arrangements of the sheet material and tow are also envisaged. For example, as shown in Figure 8, the PLA sheet material 13 may be arranged in a spiral configuration, wrapped around the longitudinal axis of the filter. Interspersed between the wrappings of the sheet material 13, which may be made up of one or more sheets, is CA tow 11. By way of further example, as shown in Figure 9, the PLA and CA in the filter material of the invention are arranged within the filter "in series". In the figure, the filter 2 is made up of two sections of segments, one comprising CA tow 21 and the other comprising PLA 22, in the form of tow, non-woven sheet, or a combination thereof. Part of the adjacent smokeable material rod 3 is also shown. The CA tow may be positioned adjacent to the rod of smokeable material, with the PLA at the mouth-end of the filter, as illustrated in Figure 9. In an alternative embodiment, these positions could be reversed. The lengths of the segments of sections are different in the figure, to reflect the ratio of CA to PLA being between 95:5 and 75:25.

However, in some embodiments, the PLA and CA of the filter material according to the invention are both provided in the same section or segment of a filter or filter element. It is possible to make filters and filter elements from filter materials as described herein using conventional processes, techniques and apparatus. Some filter elements may exhibit a pressure drop of greater than about 40 mm of water at an airflow rate of 17.5 cm³/ s per 0.1 g of filter material. They may also exhibit a filtration efficiency for particulate matter of mainstream tobacco smoke of less than about 15% per 0.1 gram of filter material.

In one embodiment the filter material comprising CA tow and PLA may be the sole filter material in the filter element or filter. In another embodiment a filter element comprising the CA tow and PLA may be part of a larger filter. In other words, the filter element may be part of a composite or multi-component filter. The filter elements of the composite filter may be arranged longitudinally of one another with the end of each filter element abutting the next. The composite filter may have 2, 3, 4 or more distinct or discrete sections.

A composite or multi-component filter may comprise one or more filter elements according to the present invention. Where there is more than one filter element according to the present invention in the composite filter, suitably the filter elements may be positioned longitudinally next to one another or be separated by another filter element.

Where the filter element is used in a composite filter, the one or more other sections of the composite filter may comprise a biodegradable filter material, such as crepe, crimped or gathered paper material. The one or more other sections may optionally comprise one or more additives, such as adsorbent or flavouring materials.

In a yet further alternative, the composite filter may comprise a section which forms a cavity containing granular material.

In addition, the pressure drop and/ or mechanical filtration efficiency of the filter plug sections can be selected to achieve the desired smoking mechanics and filtration characteristics as may be required with the specific product design desired. In a composite filter arrangement the pressure drop of the filtration material plugs/ sections may be varied.

A portion of the filter element and/ or the composite filter comprising said filter element may comprise a catalyst. Advantageously the catalyst facilitates the conversion of carbon monoxide (CO) to carbon dioxide (CO_j) in the vapour phase of the smoke. It is much by preference that the catalyst is highly selective for carbon monoxide. Preferably the catalyst may be one of the group consisting of transition metal oxides, silica, alumina, zeolites, impregnated carbon, for example, carbon impregnated with metals.

In some embodiments, the tobacco-rod end portion of the filter may include a cavity containing an adsorbent and/ or catalyst or, alternatively, may comprise a smoke filtration material having an adsorbent and/ or catalyst dispersed therein. Advantageously the adsorbent is capable of retaining at least a portion of the vapour phase of smoke.

Smoking Articles

Smoking articles of the present invention comprise a filter material according to the first aspect of the present invention. The filter material may be present in the form of a filter element or filter according to the invention, attached to a rod comprising a smokeable filler material (e.g. tobacco). The smoking article may be a cigarette.

As used herein, the term "smoking article" includes smokeable products such as cigarettes, cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes and also heat-not- burn products.

Thus, smoking articles may comprise filter material which comprises cellulose acetate and PLA in a ratio of between about 75:25 and about 95:5 by weight, a ratio of between about 75:25 and about 90:10 by weight, a ratio of between about 75:25 and about 85:15 by weight, or in a ratio of about 80:20 by weight. The cellulose acetate may be in the form of a tow. The PLA may be in the form of fibres, in the form of a fibrous tow and/ or in the form of one or more non-woven sheet materials. The filter element and/ or filter comprising said filter element may be attached to a wrapped rod of smokeable filler material by conventional tipping overwrap to form a smoking article. The tipping overwrap may be ventilating or non-ventilating overwrap. The smokeable filler material may be tobacco material or a tobacco substitute material. Preferably the smokeable material is a tobacco material. Suitably the tobacco material comprises one or more of stem, lamina, and tobacco dust. The tobacco material may comprise one or more of the following types: Virginia or flue- cured tobacco, Burley tobacco, Oriental tobacco, reconstituted tobacco. According to some embodiments, the smokeable material comprises a blend of tobacco material. For example, the smokeable material may comprise 10-80% Virginia tobacco, 10-60% Burley tobacco, 0-20% Oriental tobacco, 0-20% reconstituted tobacco and 0-30% expanded tobacco. In some embodiments, the smoking material of smoking articles comprising a filter material according to the invention and/ or filter or filter element according to the invention may comprise or consist of cut tobacco, a proportion of which tobacco may be expanded tobacco. The smoking material may comprise reconstituted tobacco or tobacco substitute material.

Examples

Experiments have been carried out to investigate and illustrate the filter processing of non-woven PLA, combination of non-woven PLA with cellulose acetate (CA) tow and the smoke chemistry of the different filter variants and the use of three filter plasticizers.

The non-woven PLA was produced using the spun bond process. The basis weight of the sheet is 30 gsm with a thickness is 180 μπι. 1. Filter Manufacture

The non-woven PLA was converted into filter rods using the paper filter process for pure non-woven PLA and using the Combined Material Filter (CMF) filter process in case of filters made from a blend of non-woven PLA and CA.

Table 1 shows the characteristics of the 132mm filter rods (without plasticizer) manufactured from non-woven PLA. Table 1

* Filtrona hardness measurement.

Figure 10 shows the variation of the pressure drop (PD) as a function of the sheet width. The filter rod length was 132 mm. Figure 11 shows the relationship between the pressure drop and the rod weight. The filter rod length was 132 mm. The "Corrected PD" means that the pressure drop is calculated for a circumference of 24.30 mm in case the initial filter circumference is slightly different from 24.30 mm. The results show a linear relationship between pressure drop and the weight of the filter rods. A comparison between the capability curve of the non-woven PLA (Figure 11) and those of CA tow (not shown here) indicates that for the same pressure drop the weight of the filter rod is much higher in case of non-woven PLA. The weight of filter rod (132 mm) manufactured from a conventional CA tow is 807 mg. The characteristics of the filter rods (132 mm length) manufactured using different plasticizers are summarized in Table 2 (TA = triacetin, PEG = poly(ethylene glycol) and TEC = triethyl citrate). The filter rods were manufactured from non-woven PLA web with a width of 250 mm. The hardness results show that none of the additives used act as a binder. The filter rod hardness decreases with increasing the amount of the additives used (see Table 2).

Table 2

* Filtrona hardness measurement.

The characteristics of the filters (132 mm length) manufactured by combining non- woven PLA and CA tow are summarized in Table 3. The filters where made using the Combined Materials Filter (CMF) process. The plasticizer used was triacetin (TA).

Table 3

Rod Parameters Filter Reference

D645/4384C D645/4384A D645/4384B

Composition: 75/25 47/53 35/65

CA/PLA (wt%)

CA tow 2.5Y37 2.1Y22 6Y17

PLA sheet width (mm) 55 115 145

Filter rod weight (g) 1.11 1.04 1.12

TA loading (mg/ rod) 89.3 50.4 73.0

Circ. (mm) 24.09 24.24 24.48 Hardness * (%) 94.6 91.3 93.4

PD (mm WG) 758.3 577.2 370.1

* Filtrona hardness measurement.

2. Cigarette Manufacture

Cigarettes were assembled using the filters mentioned in Tables 1 to 3 without any major processing issues. A conventional CA tow was used as the CA control.

3. Smoke Chemistry

3.1. Filtration efficiency

In order to evaluate the filtration efficiency of the new filters and control, cigarettes were smoked under the ISO regime with the ventilation zone blocked. Table 4 summarizes the effect of pressure drop on the smoke yields of cigarettes with PLA filters (without additives) of different pressure drops and CA control.

Table 4

Table 5 shows the smoke yields of cigarettes with PLA filters containing different additives, compared to a conventional CA control. The additives were triacetin (TA), poly (ethylene glycol) (PEG) and triethyl citrate (TEC).

Table 5

Smoke yield Additive

7.3% TA 8.7% PEG 6.4% TEC CA control

(8.6% TA)

NFDPM (mg/cig) 13.6 12.9 11.8 13.3 Nicotine (mg/cig) 0.9 0.9 0.9 1.1

CO (mg/cig) 14.7 13.9 12.4 14.0

Water (mg/cig) 3.9 2.5 2.7 4.5

Puff no. 8.8 8.8 8.4 8.7

Figure 12 shows the filtration efficiency results for PLA filters (without plasticizer) at different pressure drops. The results show for NFDPM the efficiency of the PLA filter became similar to the CA control around the PD of 71 mm WG.

Figure 13 shows the filtration efficiency in the presence of different additives, using conventional CA as a control. The results indicate that the nature of the additive has a small effect on the NFDPM filtration efficiency. The water filtration efficiency is significantly affected in the case of PEG and TEC in comparison to TA. One possible explanation is that the presence of these additives may affect the hydrophilicity of PLA. The additives used do not show any significant effect on nicotine filtration efficiency.

The smoke yields and the filtration efficiency in the case of filters manufactured using the Combined Materials Filter (CMF) process are shown in Table 6 and Figure 14, respectively. The filter composition is expressed as CA/PLA (w/w) percentage. The results show that the NFDPM filtration efficiency is higher in the case where the filter composition (CA/PLA) is 47/ 53 and even higher where the composition (CA/PLA) is 75/25. However, it should be noted that the pressure drop and filter weight of the CMF filters (Table 3) are higher in comparison to the CA control (420 mm WG, 810 mg for the filter rod of 132 mm). (Filter characteristics are reported in Table 3.)

Table 6

Smoke yield Filter variant

CMF CMF CMF PLA Control 35/ 65 47/ 53 75/ 25 100 % 100% CA

NFDPM (mg/cig) 13.8 11.7 10.4 11.5 13.3

Nicotine (mg/cig) 1.0 0.9 0.8 0.8 1.1 CO (mg/cig) 12.4 13.2 12.5 13.0 14.0

Water (mg/cig) 3.0 2.9 2.0 2.5 4.5

Puff no. 8.6 8.3 8.6 8.4 8.7

3.2. Filtration Selectivity

In order to evaluate the filtration selectivity of the different filters, cigarettes were smoked under the ISO regime with ventilation blocked and Hoffmann analytes were measured under the same conditions for all the cigarettes. Only the phenolic compounds were considered in this study.

Table 7 summarizes the effect of different additives in the PLA filter on the phenolic compound yields. (Filter characteristics are reported in Table 2.)

Table 7

Figure 15 shows the effect of additives on the filtration of the selected phenols using a pure non-woven PLA filter as the control. The results are normalized to tar and expressed as a percentage difference with CA control. The results show clearly a decrease of the cresols and phenol in comparison to the PLA filter without additive, especially for phenols when TEC is used. It appears that the PLA filter has certain selectivity towards catechol, hydroquinone and resorcinol and there is no difference compared to the CA control. Since these compounds are found in the particulate phase, this result is consistent with particulate filtration theory.

In the case of CMF, the results show that blending CA with PLA enhances the filtration selectivity in comparison to 100% PLA filter and the best results for phenol selectivity were obtained for the filter with the CA/PLA composition of 75/25. Table 8 shows the phenols delivery using Combined Materials Filter (CMF) compared to 100% PLA and a conventional CA control. The filter composition is expressed as CA/PLA (w/w) percentage. (Filter characteristics are reported in Table 3.)

Table 8

Figure 16 shows the effect of the filter composition on the filtration selectivity. The results are normalized to tar and expressed as a percentage difference with CA control. CA control is used as a baseline.

As set forth above, non-woven PLA can be processed into a cigarette filter using the paper filter process and a combination of non-woven PLA and CA tow can also be combined to form filter material. The capability curve shows that a wide range of filters can be manufactured with different pressure drops depending upon the width of the material. The weight of the filter made from non-woven PLA is higher than that made from CA tow with the same pressure drop. The additives TA, PEG and TEC do not act as a binder to harden the non-woven PLA in a filter. However, TA, PEG, TEC can be used as an additive in the PLA filter to enhance the filtration selectivity towards phenols.

The combination of CA tow with non-woven PLA gave some advantages in comparison to PLA filters such as increased hardness of the filter and increased selective filtration of phenols.

For the avoidance of doubt, it is confirmed that any feature of the invention discussed herein may be used in combination with any other feature. In particular, any feature in a claim may be used in combination with any other feature in a claim.

Embodiments described above are configured to comply with applicable laws and/ or regulations, such as, by way of non-limiting example, regulations relating to flavourings, additives, emissions, constituents and/or the like.

Many other modifications and variations will be evident to those skilled in the art, that fall within the scope of the following claims.

Claims

1. A filter material comprising cellulose acetate and polylactide in a ratio of about 95:5 to about 75:25 by weight.

2. A filter material as claimed in claim 1, wherein the cellulose acetate tow and polylactide are present in a ratio of about 80:20 by weight.

3. A filter material as claimed in claim 1 or claim 2, wherein the cellulose acetate comprises cellulose acetate tow.

4. A filter material as claimed in any one of the preceding claims, wherein the polylactide comprises a fibrous polylactide tow.

5. A filter material as claimed in any one of the preceding claims, wherein the polylactide comprises one or more non-woven polylactide sheets.

6. A filter material as claimed in any one of the preceding claims, wherein the cellulose acetate tow includes a plasticizer.

7. A filter material as claimed in any one of the preceding claims, wherein the polylactide includes a plasticizer.

8. A filter material as claimed in claim 6 or 7, wherein the plasticizer is selected from the group consisting of triacetin, triethyl citrate, polyethylene glycol.

9. A filter material as claimed in any one of the preceding claims, wherein the amount of plasticizer included in the filter material is 0 to 20% by weight of the filter material.

10. A filter or filter element for a smoking article, comprising a filter material as claimed in any one of the preceding claims.

11. A smoking article comprising a filter material as claimed in any one of claims 1 to 9, or comprising a filter or filter element as claimed in claim 10.