TOBACCO SMOKE FILTER

Abstract

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. The filter has superior biodegradability.

Claims

1. A tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres; wood pulp; and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres.

2. The tobacco smoke filter or filter element according to claim 1, wherein the non-woven fabric comprises the wood pulp in an amount of up to 20% by weight of the non-woven fabric, and an amount of water soluble binder is 0.1 to 5% expressed as percentage of a solids level content in a finished state of the non-woven fabric.

3. The tobacco smoke filter or filter element according to claim 1, wherein the staple fibres are regenerated cellulosic fibres, viscose, tencel, polyvinyl alcohol or cotton.

4. The tobacco smoke filter or filter element according to claim 1, wherein the water soluble binder is carboxymethyl cellulose, polyvinyl alcohol, hydroxycellulose, polyethylene oxide, a natural or modified starch, a cationic starch, guar gum or derivative thereof.

5. The tobacco smoke filter or filter element according to claim 3, having a dispersibility wherein 95% or more of the nonwoven fabric passes through 6.3 mm aperture screens after being subjected to EDANA Standard FG511.1 Tier 1 Dispersibility Shake Flask Test using screens of 1.6, 3.15, 6.3 and 12.5 mm aperture.

6. The tobacco smoke filter or filter element according to claim 5, having a dispersibility wherein 96% or more of the nonwoven fabric passes through 6.3 mm aperture screens after being subjected to EDANA Standard FG511.1 Tier 1 Dispersibility Shake Flask Test using screens of 1.6, 3.15, 6.3 and 12.5 mm aperture.

7. A tobacco smoke filter or filter element including a nonwoven fabric, wherein the nonwoven fabric comprises: a sheet of staple fibres, wherein the staple fibres have a ‘Ready Biodegradability’ level of biodegradability as measured according to OECD 301B ‘Ready Biodegradability’ method (modified Sturm test); and a water soluble binder; wherein the water soluble binder is uniformly coated on at least one face of the sheet of staple fibres.

8. The tobacco smoke filter or filter element according to claim 7, wherein the nonwoven fabric further comprises wood pulp.

9. The tobacco smoke filter or filter element according to claim 8, wherein the nonwoven fabric further comprises the wood pulp in an amount of up to 20% by weight of the non-woven fabric, and an amount of binder is 0.1 to 5% expressed as percentage of a solids level content in a finished state of the non-woven fabric.

10. The tobacco smoke filter or filter element according to claim 8, wherein a material is considered “Readily Biodegradable” if 60% of degradation is reached within a 10-day window in 28 days and the 10 day window is defined as beginning when 10% of the degradation is reached and ends after 10 days from this point, but before the 28th day.

11. The tobacco smoke filter or filter element according to claim 7, further comprising a flavour enhancing additive; and/or wherein the nonwoven fabric is tobacco smoke filtering material.

12. The tobacco smoke filter or filter element according to claim 1, further comprising a flavour enhancing additive; and/or wherein the nonwoven fabric is tobacco smoke filtering material.

13. A filter cigarette which includes a tobacco smoke filter or filter element according to claim 1.

14. A filter cigarette which includes a tobacco smoke filter or filter element according to claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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”.

DETAILED DESCRIPTION

Example 1

[0038] 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 10 N, 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 65 N, whilst addition of 4.5% PVOH increased tensile strength to 108 N. 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.

[0039] 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

[0040] 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.

TABLE-US-00001 PARAMETER FABRIC/ FILTER ‘A’ FABRIC/ 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 Filter 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 (Equivalent PD - %) 53 51

[0041] 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.

[0042] 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)

[0043] 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.

[0044] 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

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The filters/filter rods/filter segments may be included in filter cigarettes my methods well known in the art.

Example 5

[0049] The Fibre Biodegradability of filters of the invention was compared with known cellulose acetate filters.

[0050] 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.

[0051] 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.

[0052] 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’.

[0053] These results confirm that the filters of the invention show superior biodegradability compared to cellulose acetate filters (and cellulosic ester filters).

Experiment 6

[0054] 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.

TABLE-US-00002 Handsheet Type Total Fibre removed in departing water (%) Total Fibre removed in departing water + that retained on smallest (1.6 mm aperture) screen (%) Fibre Composition Fibre Cross-section 100% Viscose + Round 25 >95 CMC binder Trilobal 20 >95 100% Viscose + Round 5 >95 PVOH binder Trilobal 7 >95