HK1176525B - Filter additive - Google Patents

Description

Filter additive

Technical Field

The present invention relates to filter elements (filters) for smoking articles and methods of making filters (filters) comprising additive materials. The invention relates in particular to a method for introducing an additive which is solid at room temperature into a filter material, comprising a step of melting the additive material.

Background

A variety of materials have been used as filter materials for tobacco smoke. The most commonly used filter material is cellulose acetate tow. However, although cellulose acetate has excellent ability to filter tobacco smoke, it has the disadvantage that it degrades more slowly than other materials and therefore can be environmentally unfriendly.

Filter materials made from nonwoven sheets and paper are known. Suitable sheets include polyvinyl alcohol, reconstituted tobacco, starch and polylactic acid. These materials are much more degradable than cellulose acetate tow, however they have drawbacks. In particular, in order to obtain the desired structural rigidity when constructing filter elements from nonwoven sheet materials and paper, the filter materials are typically tightly packed, meaning that these filter elements have significantly different properties than filter elements made from cellulose acetate. They exhibit greater resistance to smoke flow, resulting in a higher pressure drop than conventional Cellulose Acetate (CA) filters, requiring the user to draw more effort on the smoking article. Perhaps more significantly, it has been found that smoke drawn through conventional cellulose acetate filter materials has a different taste profile than smoke drawn through the filter material. Moreover, filter elements comprising a nonwoven sheet or paper as the filter material have shown significantly lower selective removal of semi-volatile compounds compared to conventional cellulose acetate tow filter materials.

The use of additives such as triacetin (triacetin), TEC (triethyl citrate) and PEG400 (low molecular weight polyethylene glycol) in cellulose acetate filters is known. These additives function as plasticizers, which are commonly used in cellulose acetate filters to impart sufficient hardness to the filter rod for cigarette manufacture and use. Some plasticizers have the additional advantage of providing cellulose acetate tow with improved ability to selectively remove semi-volatile compounds such as phenol, o-cresol, p-cresol, and m-cresol from tobacco smoke.

These plasticizers are liquid at room temperature and are sprayed onto the cellulose acetate tow. The plasticizer coats the individual fibers within the tow and, over time, they bond or fuse adjacent fibers together at their points of contact, thereby increasing the stiffness or rigidity of the filter material, imparting the desired structural strength to the filter core. However, the mode of action of the plasticizer means that there is an upper limit to the amount that can be incorporated into the cellulose acetate tow filter material. When more than about 7% by weight of the filter is incorporated, the plasticizer begins to adversely affect the cellulose acetate tow, forming pores which impair its filtration characteristics.

The incorporation of plasticizers such as triacetin, TEC or PEG400 is more common in CA filters, whereas their incorporation in nonwoven sheet and paper filter materials is less noticeable. First, plasticizers are used in CA filters to bind the fibers, and when incorporated into nonwoven sheets or papers in which the fibers have been bound within the sheet structure, plasticizers do not significantly have this benefit. Second, these commonly used plasticizers are liquids and their application to nonwoven sheets and paper filter materials will be limited because they can cause these materials to become wet and lose their structural integrity. Paper, the most commonly used sheet filter material, may begin to disintegrate when wet, thus reducing the desirability for the user. In addition, many sheets, including polyvinyl alcohol and polylactic acid, are soluble, and thus the addition of aqueous additives can cause the material to partially dissolve.

It is therefore an object of the present invention to provide a method of constructing a filter element which is more degradable than filter elements comprising conventional cellulose acetate tow as the filtration material. Preferably, the method will also produce a filter element that exhibits improved ability to selectively remove semi-volatile compounds and provides smoke having similar taste characteristics to smoke provided by conventional cellulose acetate filters.

Disclosure of Invention

According to a first aspect of the invention, there is provided a method of manufacturing a smoking article filter element. The method comprises the following steps:

i) applying to the filter material an additive that is solid at room temperature;

ii) heating the additive to melt it; and

iii) forming the filter material and the additive into a filter element.

The steps of the method may be performed in any order, although in some embodiments step i) is preferably performed before step iii).

According to a second aspect of the invention, a filter element for a smoking article is provided. The filter element comprising a filter material and an additive which is solid at room temperature, the filter element being obtainable or obtainable by a method according to the first aspect of the invention.

According to a third aspect of the invention, there is provided a filter for a smoking article comprising a filter element according to the second aspect.

According to a fourth aspect of the present invention there is provided a smoking article comprising a filter element according to the second aspect connected to a rod of smokable filler material and/or a filter according to the third aspect. The smokable filler material may comprise tobacco and 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 (expandedtobacco), reconstituted tobacco or tobacco substitutes, and heat-not-burn products.

Detailed Description

The present invention relates to a method of producing a filter element for incorporation into a smoking article, the method comprising applying to a filter material an additive which is solid at room temperature, the method involving heating the additive so as to cause it to melt.

In one embodiment of the invention, the additive is applied to the filter material in a solid state, e.g. in powder form, prior to the formation of the filter rod. The formed filter rod may then be heated to melt the additive while the additive remains in contact with the filter material. When the additive material subsequently cools and resolidifies, it provides one or more of the following characteristics to the filter material and the formed filter element: stability and rigidity; improved smoke taste characteristics; and improved selective removal of semi-volatile compounds.

In another embodiment of the invention, the additive is melted and applied to the filter material in molten or liquid form prior to formation of the filter rod. When the additive material subsequently cools and resolidifies, it provides one or more of the following characteristics to the filter material and the formed filter element: stability and rigidity; improved smoke taste characteristics; and improved selective removal of semi-volatile compounds.

The method of the invention may be used to add additives to any type of filter material, including fibrous filter materials or tows, such as conventional cellulose acetate tow which is currently widely used in smoking article filters. However, the method is considered to be particularly effective when used to add additives to alternative filter materials, such as filter materials constructed from sheet materials, e.g., nonwoven sheet materials or paper.

Paper filter materials typically comprise gathered (gathered), pleated, crimped, creped or even shredded paper. Paper filter materials tend to have low air permeability, exhibit an alkaline pH, and are easily gathered or formed to form filter elements. One preferred filter material for use in the filter element of the present invention is gathered or pleated paper. Examples of suitable papers are Puracel and Myria-plates (Filtrona plc, UK).

Other nonwoven sheets may be used as filter materials. Nonwoven materials are broadly defined as sheet or web structures bonded together by entangling fibers or filaments mechanically, thermally or chemically, or a combination of two or more of these. They are often flat porous sheets made directly from individual fibers. They are not made by weaving or knitting and do not require the conversion of fibers into yarns. The nonwoven sheets used in the present invention are preferably readily biodegradable. Examples of materials include: polyvinyl alcohol (PVOH), polylactic acid or Polylactide (PLA), poly (-caprolactone) (PCL), poly (l, 4-butanediol succinate) (PBS), and poly (1, 4-butanediol adipate-co-terephthalate) (PBAT). Other suitable filter materials include starch fibers and calcium alginate.

Nonwoven sheets and paper are more readily biodegradable than cellulose acetate tow. However, currently, they have drawbacks when used as filter materials. In order to obtain the desired structural rigidity when constructing filter elements from nonwoven sheet material and paper, the filter material must be very tightly packed, which means that these filter elements have significantly different properties than filter elements made of cellulose acetate. They exhibit greater resistance to smoke flow, resulting in a higher pressure drop than conventional cellulose acetate filters, requiring the user to draw harder on the smoking article.

The sheet material used in the process of the present invention may comprise paper, polyvinyl alcohol, reconstituted tobacco, starch or polylactic acid. The sheet filter material is preferably paper.

Preferably, the nonwoven sheet has a thickness greater than about 0.05mm, preferably from about 0.06 mm to about 0.08 mm. The paper filter material may comprise a basis weight of about 15g/m²About 40g/m²Preferably about 20g/m²About 35g/m²The paper of (1).

The sheet used in the process of the present invention may additionally or alternatively comprise polyvinyl alcohol (PVOH). PVOH is unique in that it is the only biodegradable carbon-carbon backbone polymer that can be completely biodegraded into small molecules, such as carbon dioxide and water.

The method may include the use of sheet polylactic acid. The lactate used to produce PLA can originate from the fermentation of agricultural by-products.

However, due to the hygroscopic properties of PVOH and PLA, prior art processing attempts at these materials have resulted in filter rods that are too soft to be effectively handled in high speed cigarette manufacturing machines. In addition, cigarette filter elements formed from PVOH and PLA have failed to provide a porous matrix that is sufficiently stable to allow proper smoking characteristics and avoid collapse in use. Using the method of the invention to apply the additive, the quality of these sheets can be improved to make them suitable for use in filter elements.

In contrast to the use of additives that are liquid at room temperature, such as the plasticizers commonly used in conventional cellulose acetate filters, including low molecular weight PEG, triacetin and TEC, additives that are solid at room temperature can provide rigidity and rigidity to the filter without damaging the filter material by wetting it.

In fact, the solid additives used in the process of the invention have melted but resolidified at room temperature and caused portions of the filter material to bond together without weakening the nonwoven sheet or paper filter material. Thus, the additive is beneficial in that it actually enhances the structural integrity and rigidity of the filter material. In the case of a sheet filter material, it is possible to use less filter material in the filter element by adding the solid additive by the method of the invention. This provides further flexibility in terms of the amount of filter material required to obtain the desired hardness and rigidity when forming the filter element. This in turn will cause the manufacturer to adjust the pressure drop of the filter element. This would allow the filter element of the present invention to be designed with very similar characteristics to conventional CA filter elements.

Thus, the addition of solid additives to the filter material by the method of the present invention can eliminate the disadvantages currently associated with the use of sheet filter materials by improving filter stiffness, improving the taste of the smoke and increasing the selective removal of semi-volatile compounds. Moreover, the combination of filter material and solid additives may provide significantly improved disintegration, dispersion and/or biodegradability of the filter element.

The method of the invention allows the characteristics of the nonwoven sheet and paper filter material to be fine tuned so that the filter element can more closely resemble a cellulose acetate filter element in its performance. These additives also give much greater flexibility to the application of the sheet filter material, widening its applicability range, while maintaining beneficial biodegradable properties.

In one embodiment of the invention, the additive comprises a high molecular weight polyethylene glycol that is solid at room temperature. Suitable PEGs include PEG 600 and higher, preferably PEG1000 and higher.

An additional advantage of high molecular weight polyethylene glycols is to provide selective removal of semi-volatile compounds. The selective removal of this semi-volatile compound provided by the addition of PEG to the filter element is proportional to the amount of PEG introduced. The method of the present invention, involving the use of PEG that is solid at room temperature (as opposed to PEG used in previous filters), provides the flexibility of allowing the addition of a greater amount of PEG than would be possible if liquid PEG were used.

This means that the ability of the filter element to selectively remove semi-volatile compounds can be easily adjusted to a desired level. This is in contrast to the addition of low molecular weight PEG as a plasticizer to cellulose acetate filters. Cellulose acetate filters are generally disclosed as including less than 10% plasticizer, as the introduction of higher levels of plasticizer than this adversely affects the cellulose acetate tow, resulting in void formation. Thus, the amount of plasticizer that can be used to provide selective removal of semi-volatile compounds in cellulose acetate filters is limited.

According to the method of the invention, the amount of PEG that can be incorporated into the filter material of the filter element is: up to about 30%, preferably up to about 20%, more preferably about 5 to 10% by weight based on the filter element.

Since PEG is water soluble, its incorporation into the filter element should not adversely affect the biodegradation of the product. Indeed, it has been surprisingly found that the addition of PEG to filter elements comprising a nonwoven sheet or paper as the filter material actually enhances biodegradation.

Studies have been conducted to evaluate the effect of the use of paper filter materials and additives on biodegradability. Degradation of the cigarette butts under ambient conditions was evaluated. Samples used included filters with additive-free Puracel (7 mg) and filters with Puracel-cells along with 7% PEG 400. The results show that the introduction of PEG as an additive significantly increases the rate of biodegradation of the butts on the grass surface. Presumably this is due to the presence of microorganisms, insects, etc. (which eat the butts), and the presence of PEG additives makes some butts more attractive. Similar effects are expected to be observed when using high molecular weight PEG as an additive.

Other additives useful in the process of the present invention include high molecular weight methoxypolyethylene glycols (MPEG), such as MPEG 750, 1000, 2000, 3000 and 5000; and waxes that are solid at room temperature, including beeswax, carnauba wax, shellac, castor wax, paraffin wax, and various synthetic waxes.

If desired, the method may further include introducing additional additives such as tobacco extract, glycerin, menthol, carbon fibers, carbon particles, and the like into the sheet filter material.

Another advantage of the method of the invention is that filter elements to which an additive has been applied using the claimed method are more stable to subsequent addition of additives, including liquid additives. Other additives that are otherwise difficult to apply to the sheet material without moistening the sheet material, including liquid additives, can be added to the filter rod to adjust the characteristics of the filter or to provide further qualities to the filter element as desired, such as flavors for enhancing flavor.

The method of the present invention encompasses different ways of applying the additive to the filter material.

In one embodiment, the method involves applying the additive to the filter material in a liquid state. To do this, the additive must be heated and sprayed or otherwise applied to the filter material before the filter material is formed into a filter rod or core of the filter element.

This embodiment is attractive because it requires only minor modifications to conventional filter making machines. The only real change is to equip the device for heating the additive so that the additive is in molten form and can be applied to the filter material in this form. The application of heat is relatively easy to control and monitor. Furthermore, heat is applied primarily only to the additive, and thus the other components of the filter element need not be exposed to localized heat.

The method is suitable for both fibrous tow filter materials and nonwoven sheet and paper. Although such sheets are fed under tension, the application of the liquid additive does not weaken the sheet-like structure to a sufficient extent to cause problems.

In another embodiment, the method involves applying the additive to the filter material in a solid state, such as in powder form, prior to forming the filter material into a filter rod or core of the filter element. Once formed, the filter rod is heated to melt the additive. The additive melts and then resolidifies to bond the filter material without wetting the filter material.

The method allows for the application of additives to filter materials in a controlled and uniform manner while minimizing the amount of additive material lost. It also avoids any possible disadvantages associated with applying liquid to the filter material. For example, in the case of a sheet filter material, this embodiment avoids the possibility of weakening the sheet structure by the application of liquid.

When applying the solid additive to a sheet material, such as the nonwoven sheet material and paper discussed herein, steps need to be taken to ensure that the solid additive remains in contact with the sheet filter material while the sheet is being formed into a filter rod. This may require the application of some adhesive or specific orientation of the sheet.

Filter elements comprising a sheet material are generally manufactured using a process comprising the steps of: the sheet is crimped and then gathered to form a cylindrical filter rod. The additives may be added before or during the crimping process, or may be added to the sheet after the sheet has been crimped. The additive may even be added to the crimped material as it is gathered to form a filter rod, the effect of which is that it is stored directly within the rod without being adhered.

Any suitable binder may be used to adhere the additive to the filter material, for example, liquid starch binders, or EVA and PVA binders.

The solid additive may be applied to the sheet filter material in the form of a powder or larger pieces, such as in the form of flakes or pellets.

The additive may be applied to the filter material by any suitable method known to those skilled in the art. For example, the powdered additive may be sprayed onto the filter material, or may be applied by an applicator that may or may not be in direct physical contact with the filter material. The additive may be applied loosely to the filter material, for example by spraying or splashing, or may be applied using a degree of force, such as by pressing or painting onto the filter material.

In a particular embodiment, the filter material is formed with solid additives embedded therein or thereon. Applying an additive that is solid at room temperature to the filter material in this way simplifies the process of the invention. Once the filter material has been formed into a filter rod, the rod may be heated to melt the additive and then allowed to resolidify.

It is known to add various materials to or on sheets, such as nonwoven sheets and paper. For example, the additives may be applied to the sheet during its manufacture or as part of a post-manufacturing processing step. In this way, the additives may be incorporated into the sheet, or the additives may be incorporated as a coating on one or both sides of the sheet. The additive may be present uniformly within the sheet or on the surface of the sheet, or may be present in discrete areas (discrete areas), such as in patches or in stripes on the sheet.

Fibrous filter materials can also be made with solid additive material particles dispersed throughout the fibers. Such particles may need to adhere to the fibers. Alternatively, they may be trapped between adjacent fibers if the fibrous material is sufficiently dense.

When the additive is applied to the filter material in a liquid state, the heating step of the process of the present invention involves the application of sufficient heat to the additive to ensure that the additive melts to such an extent that its viscosity is suitable for the selected application. The molten or liquid additive may be sprayed or printed, or the filter material may be dipped in the liquid additive.

According to one embodiment, a system for applying a molten or liquid additive to a filter material comprises: a heating chamber in which the additive is maintained in a liquid state, a pump and a hose with one or more nozzles configured to spray droplets onto the filter material prior to filter formation.

Many application systems suitable for applying molten or liquid additives to filter materials are known. Such systems are available, for example, from SPIDevelopments, C.B. Kaymich & Co. Ltd, or Kohl Maschinenbau GmbH.

When the additive is to be melted after the filter material is formed into a rod or core, sufficient heat needs to be applied to ensure that all of the additive dispersed throughout the rod is melted.

Heating of the formed filter rod must be done with care because it may adversely affect other components of the filter rod, including the filter material and any wrapper (which may be paper and may be burned or charred by exposure to high temperatures).

Obviously, the temperature to which the filter rod must be heated and the duration of heating depend on the melting point of the additive. The preferred additive, PEG1000, has a melting point of about 37 ℃, so in this case the filter rod is heated to a temperature greater than 37 ℃. The filter rod may be heated to a temperature of more than 40 ℃, preferably more than 45 ℃, most preferably more than 50 ℃. Furthermore, the heating is required for a sufficient time to ensure that the entire rod is heated, rather than just the outer region.

Heating may be carried out using any suitable method. For example, the filter rod or filter element may be brought into close proximity to the heating element. Alternatively or additionally, the filter rod or filter element may be heated by a hot air stream, such as hot air or steam, or via the application of radiation, such as microwave radiation.

The filter rod may be heated as soon as it is formed. In other words, heating the filter rod may be performed at a section of the filter rod between where the filter rod is formed at the cigarette gun (garniture) and the cigarette maker knife-edge (cut-off) where the filter rod is separated into a plurality of sections. The heating of the rod will generally last for a very short time, such as less than 1 second, caused by the linear movement of the rod through the machine. Obviously, since filter rods are currently formed without a heating process, the coexistence of filter rod formation and heating may require expensive modifications to current devices.

To this end, the filter rod is preferably heated at a later stage, which may be achieved by means of a heater that is substantially separate from the apparatus involved in forming the filter rod. The heating is preferably carried out in a separate conditioning step, wherein the entire filter rod is kept at an elevated temperature for a long time to ensure that all additives are melted and bonded to the filter material.

The method of the present invention may further comprise wrapping the filter rod in a suitable wrapper, such as plugwrap (plugwrap). In this case, the heating may be done before the filter rod is wrapped. Alternatively, the filter rod may be wrapped and then heated.

According to some embodiments, the assembled filter is heated to melt the additive, although this approach may be complicated by the insulating properties of the filter material. Furthermore, the speed of filter manufacture means that the time available to heat the filter is limited. In this regard, heating of the assembled filter may be achieved in a number of ways. For example, the filter rod may be exposed to heat caused by conduction, such as on a drum dryer in the presence of hot air. Alternatively, trays of filter rods (such as 4,000 filters per tray) may be passed through a heating tunnel or similar device in the presence of hot air. The filter tray may alternatively be heated by applying radiation, such as microwave radiation.

The method of the invention may further comprise the step of introducing particulate material into the filter element. Suitable particulate materials include: an adsorbent (e.g., selected from activated carbon, charcoal, silica gel, sepiolite, alumina, ion exchange material, etc.), a pH adjuster (e.g., an alkaline material such as Na)₂CO₃Acidic materials), fragrances, other solid additives, and mixtures thereof.

Advantageously, the particulate material may be selected from a group of higher surface area materials capable of non-highly specific adsorption of smoke constituents. Suitable common adsorbents may be selected from carbon, activated coconut carbon, activated carbon-based carbon or charcoal, zeolites, silica gel, sepiolite, alumina (active or inactive), carbon-containing resins, or combinations thereof.

One class of particulate materials that can be used in the process of the present invention are carbon (e.g., activated carbon) or charcoal or other carbonaceous absorbent materials. A preferred class of activated carbons is activated coconut carbons.

The particulate material may be introduced into the filter element in a manner that causes the particulate material to be dispersed throughout the filter element, or may cause the particulate material to be dispersed in some portions (but not all) of the filter element. The particulate material may be dispersed throughout the longitudinal length of the inner core. Alternatively, the particulate material may be dispersed from one end of the core to a section at the other end. Alternatively, the particulate material may be present in discrete regions that do not necessarily extend from or are present at either end of the inner core. Different fields may have different loadings of particulate material and/or different types of particulate material.

The method of the present invention may further comprise wrapping the filter element in a suitable wrapper.

The wrapper for the filter element is preferably a wrapper paper, most preferably comprising conventional plug wrap paper, such as having a basis weight of about 20g/m²About 35g/m²Preferably about 27g/m²The molding paper of (1). The plug wrap may be porous or non-porous.

The method may comprise using a wrapper comprising a particulate material adhered to one or more portions of a surface thereof. Preferably, the particulate material is adhered to two or more portions of the wrapper, the portions being circumferentially spaced from one another, wherein at least one of the portions continues over the entire longitudinal length of the wrapper.

A smoking article filter element produced according to the method of the invention may be incorporated into a smoking article filter.

The smoking article filter may comprise a single filter element produced according to the method of the invention. Alternatively, the smoking article filter may comprise two or more filter elements produced according to the method of the invention. In other words, the filter element may be part of a composite (or multi-) filter. Suitably, the filter elements of the compound filter are arranged longitudinally to one another in such a way that the end of each filter element abuts the next. The composite filter may have 2, 3, 4 or more distinct or discrete segments. In one embodiment, the filter is a triple filter having three sections. In another embodiment, the filter is a binary filter having two sections.

The filter segments of the composite filter may be identical, or one or more of the segments may have a different composition than another one or more segments. For example, in some implementations, one or more of the segments can optionally include: (i) a cellulose acetate filter material; (ii) biodegradable filter materials such as creped, crimped or gathered paper materials; (iii) one or more additives, such as adsorbent or flavouring materials, which may be encapsulated; and/or, (iv) a cavity, which may contain a particulate material such as an adsorbent material.

A smoking article filter element produced according to the method of the invention may be incorporated into a smoking article. The filter element may be in the form of a smoking article filter as described above.

The filter element and/or filter containing the filter element may be attached to a rod of smokable filler material (e.g. a wrapped tobacco rod) wrapped by a conventional tipping overwrap to form a smoking article, which may be a cigarette.

Suitably, the smokable filler material may be a tobacco material or a tobacco substitute material. The smokable material is preferably tobacco material. Suitably, the tobacco material comprises one or more of stems, lamina and tobacco dust. The tobacco material preferably comprises one or more of the following types: virginia tobacco (Virginiatobacco) or flue-cured tobacco, Burley tobaco, aromatic tobacco (Oriental tobacaco), reconstituted tobacco. Smokable materials comprising blends of tobacco materials are particularly preferred.

The smokable filler material may also comprise one or more of the following: combustion additives, ash improvers, inorganic fillers, organic fillers, aerosol generating agents, binders, flavorings, and/or colorants.

The tipping overwrap may be a vented or non-vented overwrap.

It will be apparent to those skilled in the art that many modifications and variations can be made in the method and system of the present invention without departing from the scope of the invention. While the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described embodiments of the invention which are obvious to those skilled in the art are intended to be within the scope of the appended claims.

Claims (12)

1. A method of manufacturing a smoking article filter element comprising a sheet filter material and an additive, wherein the method comprises the steps of:

i) applying an additive that is solid at room temperature to the sheet filter material;

ii) heating the additive to melt it; and

iii) forming the sheet filter material and additive into a filter element,

wherein the steps of the method may be performed in any order.

2. A method according to claim 1, wherein the additive material is applied to the sheet filter material prior to forming the filter element and subsequently heating the additive.

3. The method of claim 1, wherein the additive is heated and applied to the sheet filter material in a liquid state prior to forming the filter element.

4. The method of claim 1, wherein the additive comprises a high molecular weight polyethylene glycol that is solid at room temperature.

5. The method of claim 4, wherein the polyethylene glycol is PEG 1000.

6. The method of claim 1, wherein the amount of additive introduced in the filter element is at most 50% by weight based on the filter element.

7. The method of claim 1, wherein the sheet filter material is a nonwoven sheet or paper.

8. The method of claim 1, wherein the filter element further comprises at least one adsorbent material.

9. A filter element for a smoking article comprising a sheet filter material and an additive which is solid at room temperature, wherein the filter element is obtainable by the method of any preceding claim, and wherein the sheet filter material comprises paper, reconstituted tobacco or starch.

10. A filter for a smoking article comprising the filter element of claim 9.

11. A smoking article comprising a filter element as claimed in claim 9 and/or a filter as claimed in claim 10, and a rod of smokable filler material.

12. The smoking article of claim 11, wherein the article is a cigarette.