Patent Publication Number: US-2015059789-A1

Title: Tobacco smoke filter

Description:
The present invention relates to filters and filter elements for smoking articles such as cigarettes. 
     There is a widespread desire to reduce the problems associated with the environmental impact of cigarette butt litter. The vast majority of current cigarette filters are constructed using conventional cellulose acetate filamentary tow, for which the rate of biodegradation is very slow. This causes issues when butts are discarded on the ground such that the filters can remain clearly identifiable for prolonged periods of time. In addition, current cellulose acetate filters do not disperse when discarded into waterways and their characteristic size and shape is retained even after lengthy immersion in water. This causes problems in waste water treatment plants where used butts have to be removed from the water stream during the treatment process. Of course, many butts that are originally discarded on land will ultimately end up in water treatment plants after they have been swept away down drains following rainfall. Thus, there is a need for a cigarette filter that is made from readily biodegradable materials and which disperses rapidly when immersed in water. In addition, the filter material must satisfy numerous other criteria, in particular being in a form suitable for high speed conversion into cigarette filters; provide suitable characteristics (e.g. filtration efficiency, hardness, lack of variability, etc) to the finished filter; be economically viable; and enable acceptable subjective characteristics (notably taste and appearance) in the final cigarette. 
     This is not a new problem and researchers have been endeavouring to find a suitable biodegradable cigarette filter material for decades. Numerous patent applications have been filed over this time for materials that are claimed to address these requirements but as yet none have gained any significant market acceptance. There remains, therefore, a need for a tobacco smoke filtering material which is readily biodegradable, disintegrating very rapidly when immersed in water. 
     According to the present invention in a first aspect there is provided a tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres; and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres. 
     According to the present invention in another aspect there is provided a tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: staple fibres (e.g. a sheet of staple fibres); and a water soluble binder; wherein the water soluble binder is applied to the staple fibres in aqueous form. 
     Nonwoven fabrics may be defined as sheet or web structures bonded together by entangling fibres or filaments (and by perforating films) mechanically, thermally or chemically. They may be made directly from separate fibres (or from molten plastic or plastic film). Herein, the term “nonwoven fabric” expressly does not include paper or base paper. 
     Preferably the non woven fabric is a wet laid non woven fabric. The nonwoven fabric may have basis weight of 25 to 42 gsm, for example 27 to 40 gsm. 
     The staple fibres are preferably of a biodegradable material. The staple fibres may be regenerated cellulosic fibres, e.g. Viscose or Tencel, both of which are available from Lenzing AG. Other biodegradable fibres, such as Polyvinyl Alcohol (PVOH), Polylactic Acid (PLA), Polyglycolic acid (PGA) or cotton may also be used. It is possible to use less degradable or non biodegradable fibres, e.g. cellulose acetate fibres, cellulosic ester fibres, but these are not preferred. Preferably, the staple fibres are not cellulose acetate fibres or cellulose ester fibres. 
     Preferably the filter/filter element and/or nonwoven fabric and/or staple fibres have the ‘Ready Biodegradability’ level of biodegradability as measured according to OECD 301B ‘Ready Biodegradability’ method (modified Sturm test), which is well known in the art. 
     The staple fibres may be staple fibres of cut length 4 mm to 10 mm, for example 4 to 6 mm. The staple fibres may be of diameter 1.7 dtex to 3.3 dtex. The staple fibres may be of any cross-section (e.g. round, trilobal, etc). It will be appreciated that staple fibres of any cut length and diameter suitable for use in a wet laid nonwoven fabric may be used without departing from the spirit of the invention and that a blend of different fibres, fibre lengths or fibre diameters may be used in the fabric. 
     The amount of water soluble binder may be 0.1% to 5%, for example 0.5 to 3%, for example 1%, expressed as percentage of the solids level content in the finished nonwoven fabric. The water soluble binder may be carboxymethyl cellulose (CMC), polyvinyl alcohol (PVOH), hydroxycellulose, polyethylene oxide, natural starch, a modified starch, a cationic starch, guar gum, or a derivative of the above. The binder can be applied by any known method suitable for the application of liquid binders such as curtain coating, size press, mangle padding, spray, etc. Preferably the nonwoven fabric does not include an alkaline compound. 
     The filters and element of the invention include a nonwoven fabric which comprises (e.g. short cut biodegradable) staple fibres (e.g. regenerated cellulosic fibres) and a water-soluble binder. Preferably, the water soluble binder is applied (to the fibres) in an aqueous form. Preferably, the water soluble binder is applied (to the fibres) in an aqueous form and subsequently dried. 
     The specific nonwoven fabric material is preferably manufactured by a wet laid process. Nonwovens can be prepared by a variety of different well known manufacturing routes (e.g. dry laid or ‘carded’, spunbound, wet laid, air laid, etc). The present applicants have found that wet laid fabrics are best suited to meeting the demanding tip-to-tip pressure drop reproducibility criteria required for cigarette filters, which is a vital prerequisite for a viable tobacco smoke filtering material (regardless of its dispersability characteristics). The pressure drop is related to the weight of fabric used per tip. The basis weight of papers and nonwovens is measured using a standard method that quantifies the weight of an area at least 20×25 cm. The quantity used in a typical cigarette filters uses only around 10% of this quantity, so data based on the weight variability of such larger test specimens can be misleading as to their suitability to meet the reproducibility criteria for cigarette filters. By measuring the weight variability of fabric strips of 2 cm×30 cm, the applicants determined that wet laid nonwovens were best suited to meeting the required weight variability requirements of not greater than around ±1%. 
     A wet laid fabric made from 100% staple fibre is extremely weak and does not have sufficient mechanical integrity to withstand processing on filter-making machinery. Thus, a binder is needed to provide sufficient strength to the fabric. Prior art wet laid fabrics often incorporate a thermoplastic binder fibre as part of the fibre furnish; these binder fibres are then activated during the drying stage of fabric manufacture. However, the present applicants have found that fabrics that incorporate binder fibres are unsuitable for this application because they do not readily disperse in cold water (see Comparative Example 3 below). The applicants have found that the use of a (e.g. liquid) water soluble binder with the staple fibres results may enable rapid dispersion in cold water. 
     The non woven fabric may be a fabric having a dispersibility wherein 95% or more, for example 96% or more, of the nonwoven fabric passes through 6.3 mm aperture screens after being subjected to EDANA Standard FG511.1 Tier 1 Dispersability Shake Flask Test (using screens of 1.6, 3.15, 6.3 and 12.5 mm aperture). This test is well known in the art, and this dispersibility indicates ready and effective dispersion in cold water (high dispersibility). 
     The end appearance and hardness characteristics of filters according to the invention are also similar to those of cellulose acetate, again enhancing their commercial acceptability. 
     Advantageously, the nonwoven fabrics used in filters according to this invention may be processed (e.g. embossed) using standard equipment which is used for making paper-based cigarette filters. Paper filters give greater tar retention than cellulose acetate filters of the same pressure drop. This means that it is not possible for the cigarette producer to simply replace a cellulose acetate filter with a paper filter, because either the length of the filter would need to change (to maintain the same pressure drop or tar delivery) or the cigarette tar delivery would decrease and pressure drop increase (for a constant filter length). The present applicants have found that the tar retention of filters and filter elements according to the invention are much closer to those of cellulose acetate rather than paper. The present applicants also found that the more open and inherently porous the fabric structure, the lower the tar retention of the filter incorporating that material. Thus, the porosity of the nonwoven fabric may be engineered by controlling the constituent fibre properties such as polymer type, fibre cross-section, fibre crimp and fibre dimensions, to provide filters and filter elements of desirable tar retention and pressure drop. This means that the filters/elements of the invention find further advantage because they may be used as a simple replacement for cellulose acetate filters. 
     The nonwoven fabric may further comprise wood pulp. Herein, the term wood pulp includes a pulp comprising a naturally occurring cellulose fibre (e.g. obtained from a soft wood or hard wood by conventional method such as Sulfite method or Kraft method) which may have been beaten (as is well known in the art) e.g. with the use of a conventional beating machine or refining machine. Wood pulp may enhance the tensile strength of the nonwoven fabric. If wood pulp is included it is preferred that it is present in an amount of 0.1 to 20%, for example 5 to 10%, by weight of the non-woven fabric. In a preferred example, wood pulp is included in an amount of up to 9.5%, for example 1 to 9%, for example 5 to 9%, by weight of the non-woven fabric. The applicants have surprisingly found that the non-woven fabric including this rather small amount of wood pulp (in addition to the water soluble binder) is sufficiently strong to be formed into filters/filter elements. In a different, preferred example, wood pulp is included in an amount of up to 20%, for example 1 to 20%, by weight of the non-woven fabric; and the water soluble binder is present in an amount of 0.1% to 5%, expressed as percentage of the solids level content in the finished non-woven fabric. 
     Thus, according to the present invention in an aspect there is provided a tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres; woodpulp; and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres; and wherein up to 9.5% by weight of the non-woven fabric is wood pulp. 
     According to the present invention in another aspect there is provided a tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres; woodpulp; and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres; wherein the non-woven fabric comprises wood pulp in an amount of up to 20% by weight of the non-woven fabric, and the amount of binder is 0.1 to 5% expressed as percentage of the solids level content in the finished non-woven fabric. Preferably, the staple fibres are not cellulose acetate fibres or cellulose ester fibres. 
     The tobacco smoke filter or filter element may further comprise a flavour enhancing additive. The flavour enhancing additive may be an additive as disclosed in WO 2010/136751 for use in paper filters. The flavour enhancing additive may be an alicyclic lactone, an aromatic lactone, an aromatic ketone, or secondary alcohol or ester thereof, a phthalide, χ-Valerolactone, χ-Hexalactone, δ-Hexalactone, χ-Heptalactone, χ-Octalactone, δ-Octalactone, 4-Hydroxy-3-pentenoic acid lactone, 5-Hydroxy-2-decenoic acid δ-lactone, 4,4-Dibutyl-χ-butyrolactone, Mintlactone, Dehydromenthofurolactone, 3-Butylidenephthalide, 3-n-Butylphthalide, Whiskey lactone or sedanenolide. 
     The tobacco smoke filter or filter element may comprise a longitudinally extending core of tobacco smoke filtering material. The tobacco smoke filtering material may include, or be, the nonwoven fabric. The longitudinally extending core of tobacco smoke filtering material may be substantially cylindrical. 
     A tobacco smoke filter or filter element according to the invention may be of circumference 14 to 28 mm, for example 16 to 26 mm, for example 16 to 17 mm or 24 to 25 mm. A tobacco smoke filter of the invention may be of length 10 to 40 mm, e.g. 15 to 35 mm, e.g. 20 to 30 mm. A tobacco smoke filter element of the invention may be of length 5 to 30 mm, e.g. 6 to 20 mm, e.g. 8 to 15 mm, e.g. 10 to 12 mm. 
     The tobacco smoke filter or filter element of the invention may further comprise a wrapper of e.g. plugwrap. The wrapper is preferably engaged around the tobacco smoke filter or filter element (e.g. around the longitudinally extending core of tobacco smoke filtering material). The wrapper (e.g. plugwrap) is preferably held in place with a water soluble adhesive (e.g. by means of a lapped and stuck seam as is known in the art). The water soluble adhesive advantageously facilitates the opening of the filter on contact with water to expose the filter material (nonwoven fabric) contained therein, thereby facilitating break down of the filter (nonwoven fabric) after use. 
     Filters or filter elements of the invention may be used as single filter tips, as filter rods, as one or more segments within a multi-segment filter etc. Thus, a filter element according to the invention may be used as a segment of a dual, triple, or other multi component (multiple segment), filter. Dual and other multiple component filters are known in the art. Filters according to the invention may be used in machine made cigarettes (e.g. those mass produced and packaged). Filters according to the invention may also be used as a filter tip for use with an individually rolled cigarette (e.g. a hand rolled cigarette) or a Roll Your Own or Make-Your-Own product. 
     According to the present invention in a further aspect, there is provided a filter cigarette which includes a tobacco smoke filter or filter element according to the invention. In a filter cigarette according to the invention, a filter of the invention (or a filter which includes a filter element of the invention) is joined to a wrapped tobacco rod with one end toward the tobacco. The filter may, for example, be joined to the wrapped tobacco rod by ring tipping (which engages around just the adjacent ends of a [wrapped] filter and rod to leave much of the filter wrapper exposed) or by a full tipping overwrap (which engages around the full filter length and adjacent end of the tobacco rod). Preferably the plug wrap/overwrap and/or tipping paper includes a water soluble lap adhesive. The water soluble adhesive advantageously facilitates the opening of the filter on contact with water to expose the filter material (nonwoven fabric) contained therein, thereby facilitating break down of the filter (nonwoven fabric) after use. 
     Any filter or filter cigarette according to the invention may be unventilated, or may be ventilated by methods well known in the art, e.g. by use of a pre-perforated or air-permeable plugwrap, and/or laser perforation of plugwrap and tipping overwrap. 
     The filters or filter elements according to the invention may be made (by methods known in the art) as continuous rods. The continuous rod as it issues continuously from the production machine outlet is cut into finite lengths for subsequent use. This cutting may be into individual filters or filter elements as defined and described above, each of which is then attached to an individual wrapped tobacco rod to form a filter cigarette. More usually, however the continuously issuing rod of filters is first cut into double or higher multiple (usually quadruple or sextuple) lengths for subsequent use; when the initial cut is into quadruple or higher lengths, then the latter are subsequently cut into double lengths for the filter cigarette assembly—in which the double length filter rod is assembled and joined (by ring tipping or full tipping overwrap) between a pair of wrapped tobacco rods with the combination then being severed centrally to give two individual filter cigarettes. Similar techniques are used with e.g. double length filter elements which are combined to make dual or multiple filters, as is known in the art. The invention includes double and higher multiple length filter rods (and/or filter element rods). 
     According to the present invention in a further aspect there is provided a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres; and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres. According to the present invention in another aspect there is provided a nonwoven fabric, wherein the nonwoven fabric comprises: staple fibres (e.g. a sheet of staple fibres); and a water soluble binder; wherein the water soluble binder is applied to the staple fibres in aqueous form. Preferably the non woven fabric is a wet laid non woven fabric. The nonwoven fabric of the invention comprises (e.g. short cut biodegradable) staple fibres and a water-soluble binder. Preferably, the water soluble binder is applied (to the fibres) in an aqueous form. The staple fibres may be staple fibres of cut length 4 mm to 10 mm, for example 4 to 6 mm. The staple fibres may be of diameter 1.7 dtex to 3.3 dtex. The staple fibres may be of any cross-section (e.g. round, trilobal, etc). It will be appreciated that staple fibres of any out length and diameter suitable for use in a wet laid nonwoven fabric may be used without departing from the spirit of the invention and that a blend of different fibres, fibre lengths or fibre diameters may be used in the fabric. 
     The staple fibres are preferably of a biodegradable material. The staple fibres may be regenerated cellulosic fibres, e.g. Viscose or Tencel, both of which are available from Lenzing AG. Other biodegradable fibres, such as Polyvinyl Alcohol (PVOH), Polylactic Acid (PLA), Polyglycolic acid (PGA) or cotton may also be used. It is possible to use less or non biodegradable cellulose acetate fibres but these are not preferred. 
     The nonwoven fabric may further comprises wood pulp. Wood pulp may enhance the tensile strength of the nonwoven fabric. If wood pulp is included it is preferred that it is present in an amount of 0.1 to 20%, for example 5 to 10%, by weight of the non-woven fabric. 
     The amount of water soluble binder may be 0.1% to 5%, for example 0.5 to 3%, for example 1%, expressed as percentage of the solids level content in the finished nonwoven fabric. The water soluble binder may be carboxymethyl cellulose (CMC), polyvinyl alcohol (PVOH), hydroxycellulose, polyethylene oxide or starch. The binder can be applied by any known method suitable for the application of liquid binders such as curtain coating, size press, mangle padding, etc. Preferably the nonwoven fabric does not include an alkaline compound. 
     In a preferred example, wood pulp is included in an amount of up to 9.5%, for example 1 to 9%, for example 5 to 9%, by weight of the non-woven fabric. The applicants have surprisingly found that the non-woven fabric having this rather small amount of wood pulp (in addition to water soluble binder) is sufficiently strong to be formed into filters/filter elements. In a different, preferred example, wood pulp is included in an amount of up to 20%, for example 1 to 20%, by weight of the non-woven fabric; and the water soluble binder is present in an amount of 0.1% to 5%, expressed as percentage of the solids level content in the finished non-woven fabric. 
     Preferably, the staple fibres are not cellulose acetate fibres or cellulose ester fibres. 
     According to the present invention in a further aspect there is provided a tobacco smoke filter or filter element comprising a filtering material which includes a nonwoven fabric according to the invention. 
     The present invention will now be illustrated with reference to the following Examples and the attached drawing in which  FIG. 1  shows a plot of biodegradability with time for “Viscose 2” and “Tencel 2”, filter rods of the invention, compared to a known cellulose acetate filter rod “CA”. 
    
    
     EXAMPLE 1 
     Small scale wet laid fabrics of about 40 gsm were prepared using a Handsheet Former in accordance with TAPPI standard T205. A fibre blend of 90% PVOH fibre (2.8 dtex, 4 mm length) and 10% woodpulp was used. The tensile strength of these sheets was below 10N, i.e. fairly weak. CMC or PVOH water soluble binders were subsequently applied to these sheets using a padding machine—the addition of 4% CMC increased tensile strength to 65N, whilst addition of 4.5% PVOH increased tensile strength to 108N. Thus the addition of liquid-based binders imparts sufficient strength to enable such fabrics to be processed on high speed cigarette filter making equipment. These handsheet fabrics were subjected to EDANA Standard FG511.1 Tier 1 Dispersability Shake Flask Test (using screens of 1.6, 3.15, 6.3 and 12.5 mm aperture) and it was found that over 99.5% passed through the smallest 1.6 mm screen, thereby demonstrating a very high level of dispersability. It was also observed that the addition of binder to the untreated sheet improved the level of dispersability as measured by this test. 
     Example 1 demonstrates that nonwoven fabrics of the invention are suitable for use in tobacco smoke filters and filter elements (according to the invention), and have excellent levels of dispersability in cold water meaning they are highly biodegradable. 
     EXAMPLE 2  
     Two types of wet laid fabric (labelled A and B) according to the invention were prepared using a pilot scale inclined wire hydroformer. Fabric A used 100% viscose fibres of length 6 mm and linear density 1.7 dtex (supplied by Kelheim Fibres GmbH) and fabric B used 100% tencel fibres of length 6 mm and linear density 1.7 dtex (supplied by Lenzing AG). A 1% solution of water soluble CMC binder (Finnfix 700, manufactured by Noviant) was applied to both fabrics during manufacture via a curtain coating technique. Cigarette filters were then manufactured from both types of fabric using equipment for the manufacture of paper-based cigarette filters, as is well-known in the art (see e.g. Example 4). An essential aspect of this latter process is the longitudinal embossing of the fabric in order to facilitate its condensing into a cylindrical rod form. The bulk, tensile and stretch characteristics of the fabric are highly important in determining whether it is able to withstand the embossing process—e.g. it must not break or block the rollers—and the applicants surprisingly found that both fabrics processed well on the filter-making equipment. The table below gives test results for the fabrics and for cigarette filters made from these fabrics. 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 FABRIC/ 
                 FABRIC/ 
               
               
                 PARAMETER 
                 FILTER ‘A’ 
                 FILTER ‘B’ 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Fabric Weight (gsm) 
                 39.4 
                 36.9 
               
               
                 Fabric Weight Variation (%) 
                 0.76 
                 0.88 
               
               
                 Tensile Strength - Machine Direction (N) 
                 37.2 
                 32.3 
               
               
                 Tensile Strength - Cross Direction (N) 
                 28.5 
                 20.9 
               
               
                 Filter Rod Hardness (%) 
                 89 
                 91 
               
               
                 Filter Rod Pressure Drop C/V (%) 
                 2.0 
                 3.2 
               
               
                 Fiter Rod Weight C/V (%) 
                 0.6 
                 0.7 
               
               
                 Filter Hardness (%) 
                 89 
                 91 
               
               
                 27 mm Filter Tip Pressure Drop (mm Water) 
                 75 
                 70 
               
               
                 Filter Tip Tar Retention (%) 
                 59 
                 57 
               
               
                 Tar Retention Paper (Equivalent PD - %) 
                 72 
                 70 
               
               
                 Tar Retention Cellulose Acetate  
                 53 
                 51 
               
               
                 (Equivalent PD - %) 
               
               
                   
               
            
           
         
       
     
     The dispersion characteristics of these filters were assessed by placing filters from which the plugwrap had been removed in a beaker of cold water. Filters A and B both completely dispersed in less than one minute with occasional gentle agitation. This was significantly faster than paper filters which showed no sign of dispersion over the same time frame. Samples of fabrics A and B were also subjected to EDANA Standard FG511.1 Tier 1 Dispersability Shake Flask Test (using screens of 1.6, 3.15, 6.3 and 12.5 mm aperture). It was found that 99% of fabric A and 97% of fabric B passed through 6.3 mm aperture screens after being subjected to the conditions, indicating a high level of dispersability. 
     Example 2 demonstrates that nonwoven fabrics of the invention are suitable for use in tobacco smoke filters and filter elements (according to the invention), and have excellent levels of dispersability in cold water meaning they are highly biodegradable. 
     Comparative Example 3 (Not of the Invention) 
     A further trial was conducted to prepare a third material (“Fabric C”) using the same equipment and viscose fibres as Fabric A, but using 5% PVOH binder fibres rather than 1% water soluble liquid binder—i.e. it comprised 95% viscose and 5% PVOH fibre. Fabric C had a weight of 36 gsm, a weight variation of 1.05%, a machine direction tensile strength of 47N and a cross direction tensile of 33N, which were all close to the values of Fabrics A and B. However, the dispersion characteristics of Fabric C were markedly inferior to those of Fabrics A and B. There was no sign of rapid dispersion after the tip was placed in water and less than 10% passed through a screen of 6.3 mm apertures after being subjected to the same Shake Flask Test as in Examples 1 and 2. 
     Comparative Example 3 demonstrates that for rapid dispersion the water soluble binder should be applied to the nonwoven fabric as a uniform layer (e.g. by application in aqueous form), rather than as binder fibres within the nonwoven fabric. 
     EXAMPLE 4 
     Two types of wet laid fabric (again labelled A and B) according to the invention were prepared using a pilot scale inclined wire hydroformer, as with Example 2. Fabric A used 100% viscose fibres of length 6 mm and linear density 1.7 dtex (supplied by Kelheim Fibres GmbH) and fabric B used 100% tencel fibres of length 6 mm and linear density 1.7 dtex (supplied by Lenzing AG). A 1% solution of CMC binder (Finnfix 700, manufactured by Noviant) was applied to both fabrics during manufacture via a curtain coating technique. Cigarette filters were then manufactured from both types of fabric using equipment for the manufacture of paper-based cigarette filters, as is well-known in the art. 
     Sample filters were made from a cylindrical rod (of length 15 mm and circumference 24.50 mm) formed from wet laid fabric A or B according to the method set out in GB2075328A. 
     The wet laid nonwoven fabric is formed on an inclined wire machine as set out above. The longitudinally advancing finished web of nonwoven fabric is then longitudinally advanced between co-operating rolls having circumferentially-extending corrugations (to longitudinally emboss the fabric), and thereafter continuously gathered (while longitudinally advancing as a nonwoven fabric web) laterally into rod form. The resulting continuously produced rod is continuously cut transversely into finite lengths to give the product filters or filter rods, by methods which are also known in the art. 
     The filters/filter rods/filter segments may be included in filter cigarettes my methods well known in the art. 
     EXAMPLE 5 
     The Fibre Biodegradability of filters of the invention was compared with known cellulose acetate filters. 
     Sample filters according to the invention were made according to the method set out in Example 4 above. The “Viscose 2” filter was made from a fabric which used 100% viscose fibres of length 6 mm and linear density 1.7 dtex (supplied by Kelheim Fibres GmbH). The “Tencel 2” filter was made from a fabric which used 100% tencel fibres of length 6 mm and linear density 1.7 dtex (supplied by Lenzing AG). A 1% solution of CMC binder (Finnfix 700, manufactured by Noviant) was applied to both fabrics during manufacture via a curtain coating technique. The filters were then manufactured from both types of fabric using equipment for the manufacture of paper-based cigarette filters, as is well-known in the art. 
     The biodegradability was measured according to OECD 301B ‘Ready Biodegradability’ method (modified Sturm test) by an independent laboratory. The test provides a measure of the biodegradability of a material (expressed as a percentage) over a 28 day period.  FIG. 1  shows the results for the Viscose 2 and Tencel 2 filters according to the invention compared to ‘CA’—standard cellulose acetate filter rods—when tested according to this method. 
     It is clear that the Viscose 2 and Tencel 2 filters (and materials) according to the invention degrade faster and more extensively than cellulose acetate. Moreover, in accordance with this test, materials can be assigned three levels of biodegradability as measured by their biodegradation over a 10 day period. The pass level of biodegradability is ‘Ready Biodegradability’ (gives greater than 60% biodegradability over the defined 10 day period), but there other lesser levels of biodegradability depending on the materials performance in the test, for example ‘Ultimate Biodegradability’ and ‘None’. The Viscose 2 and Tencel 2 filters according to the invention were all certified as ‘Ready Biodegradability’, whereas ‘CA’ received the lesser certification of ‘Ultimate biodegradability’. 
     These results confirm that the filters of the invention show superior biodegradability compared to cellulose acetate filters (and cellulosic ester filters). 
     Experiment 6 
     EP 0709037 refers to the advantages of cellulose ester fibres with modified cross-section, e.g. specific X, Y or I shapes. Comparative examples 1-5 therein refer to fibres with more regular fibre cross-sections, and are described as having “poor” disintegratability in comparison to “excellent” disintegratability from the modified cross-section fibres. The EDANA Flask Shake test (see method described in Example 1) was performed on a number of handsheets of the invention, made with viscose fibres of different cross-sections. The viscose fibres used were ‘Danufil’ and ‘Galaxy’ from Kelheim Fibres, which have a round cross-section, and a modified trilobal cross-section, respectively. The results are shown in the Table below. The results show that there is little difference between the dispersibility of sheets made using round and modified trilobal cross-sections. This result is entirely unexpected given the teaching of EP 0709037, which suggests that (cellulose ester) fibres with modified cross-section, e.g. specific X, Y or I shapes, have “excellent” disintegratability, while fibres with more regular fibre cross-sections have “poor” disintegratability. This demonstrates that the biodegradability of the filters of the invention which include staple fibres, a small amount of water soluble binder, and (optionally) a small amount of wood pulp, is remarkable. Further, these results show that, surprisingly, in non-woven fabrics (and filters) of the invention, the shape of the fibre cross section is irrelevant with regard to dispersibility. 
     
       
         
           
               
               
               
            
               
                   
               
               
                   
                   
                 Total Fibre removed in 
               
               
                   
                 Total Fibre  
                 departing water + that 
               
               
                 Handsheet Type 
                 removed in  
                 retained on smallest  
               
            
           
           
               
               
               
               
            
               
                 Fibre 
                 Fibre Cross- 
                 departing  
                 (1.6 mm aperture)  
               
               
                 Composition 
                 section 
                 water (%) 
                 screen (%) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 100% Viscose +  
                 Round 
                 25 
                 &gt;95 
               
               
                 CMC binder 
                 Trilobal 
                 20 
                 &gt;95 
               
               
                 100% Viscose + 
                 Round 
                 5 
                 &gt;95 
               
               
                 PVOH binder 
                 Trilobal 
                 7 
                 &gt;95