WO2009037461A2

WO2009037461A2 - Tobacco smoke filter

Info

Publication number: WO2009037461A2
Application number: PCT/GB2008/003168
Authority: WO
Inventors: Joanne Anderson; Michael John Taylor
Original assignee: Filtrona International Limited
Priority date: 2007-09-19
Filing date: 2008-09-19
Publication date: 2009-03-26
Also published as: CN101827536A; WO2009037461A3; CN101827536B

Abstract

A tobacco smoke filter or filter element comprising a tobacco smoke filtering material (2,3), and an additive selected from glyceryl tripropionate and triethyl citrate, wherein the additive is present in an amount of between 1% and 30 % by weight of the tobacco smoke filtering material.

Description

TOBACCO SMOKE FILTER

The present invention relates to tobacco smoke filters and filter elements for smoking articles such as cigarettes.

Phenolic compounds - for example phenol, cresols, catechol and resorcinol - are known constituents of cigarette smoke. They are toxic compounds - in particular, phenol and catechol are included on the so- called "Hoffmann" list of the most hazardous compounds found in cigarette smoke. It is considered desirable to potentially reduce the quantities of these compounds delivered to the smoker.

Selective filtration occurs when the yield of selected chemicals in cigarette smoke is proportionally reduced to a greater extent than the majority of compounds in smoke (e.g. tar). The standard filtering material used in cigarette filters is cellulose acetate tow plasticised with triacetin. Plasticisers are added to cellulose acetate tow during filter manufacture in order to give the rod sufficient hardness for cigarette manufacture and use. Cellulose acetate tow plasticised with triacetin is known to exhibit a selective filtration effect towards phenols.

It is often advantageous to reduce the gas phase (notably carbon monoxide) and vapour phase components in smoke relative to the tar delivery of the cigarette. This may be achieved effectively by the use of a combination of high levels of cigarette ventilation and high pressure drop/low retention filters, as exemplified by the Filtrona COR filter, (European Patent No.1555899 B). The COR type filter includes less plasticised cellulose acetate tow than e.g. a conventional monoacteate filter; this may diminish the overall selective filtration for phenols of a COR filter compared to a monoacteate filter. An additive that selectively reduces phenols (and which can be easily applied to cigarette filters), either as a means of off-setting the increase in phenols associated with the reduced gas phase cigarettes as discussed above, such as the COR filter, or for further enhancing phenol reduction in conventional monoacetate filter cigarettes, is desirable.

A problem associated with the use of triacetin as a plasticiser is that it breaks down over time to generate acetic acid, which in extreme cases gives rise to an unpleasant vinegary smell from stored filters. It is desirable that any additive for addition to a filter should not increase acetic acid generation from triacetin.

According to the present invention there is provided a tobacco smoke filter or filter element comprising a tobacco smoke filtering material, for example a rod of tobacco smoke filtering material; and glyceryl tripropionate. Glyceryl tripropionate is also referred to herein as

"tripropionin".

The tobacco smoke filtering material may be, for example, cellulose acetate tow, paper e.g. filtration paper, polypropylene or non-woven filter material. The tripropionin may be included on or in the tobacco smoke filtering material.

The tobacco smoke filtering material (e.g. cellulose acetate tow) may include a plasticiser material (e.g. the filtering material may be a plasticised filtering material, e.g. a filtering material which has been plasticised by a plasticiser material). Plasticiser materials (herein also "plasticisers") for tobacco smoke filter materials are well known in the art. The plasticiser material may be, for example, Triacetin, triethyleneglycol diacetate (TEGDA) or polyethylene glycol (PEG). The tripropionin may be included on or in the plasticiser material. The tripropionin may be mixed with the plasticiser material (e.g. triacetin). The tripropionin may be mixed with the plasticiser material (e.g. triacetin) and the mixture applied to the tobacco smoke filter material (e.g. cellulose acetate tow). The tobacco smoke filter material may be a plasticised filtering material (e.g. plasticised cellulose acetate tow) which has been plasticised with a plasticiser material (e.g. triacetin) which has been mixed with tripropionin.

According to one aspect of the present invention there is provided a tobacco smoke filter or filter element comprising a tobacco smoke filtering material, for example a rod of tobacco smoke filtering material; glyceryl tripropionate; and triacetin.

The amount of glyceryl tripropionate may be, for example, between 1% and 30%, for example between 2% and 25%, for example between 3% and 20%, for example between 4% and 15% by weight of the tobacco smoke filtering material (or plasticised tobacco smoke filtering material).

The present invention in a further aspect also provides the use of glyceryl tripropionate (tripropionin) in a tobacco smoke filter or filter element for selectively reducing one or more phenolic compounds in tobacco smoke. The phenolic compound may be, for example, phenol, o- cresol, m-cresol or p-cresol.

The applicants have found that the inclusion of tripropionin in a tobacco smoke filter or filter element may provide a remarkable and unexpected reduction in phenol yield in tobacco smoke, as well as in the phenol:tar ratio.

The present invention in a further aspect also provides the use of glyceryl tripropionate (tripropionin) [optionally with triacetin] in a tobacco smoke filter or filter element for selectively reducing one or more of pyridine, quinoline and/or styrene in tobacco smoke.

The applicants have found that the inclusion of tripropionin in a tobacco smoke filter or filter element may provide a remarkable and unexpected reduction in pyridine, quinoline and/or styrene yield in tobacco smoke, as well as in the pyridine:tar, quinoline:tar and/or styrene:tar ratio. According to the present invention in a further aspect there is provided a tobacco smoke filter or filter element comprising a tobacco smoke filtering material, for example a rod of tobacco smoke filtering material; and triethyl citrate, in an amount of between 1% and 30%, for example between 2% and 25%, for example between 3% and 20%, for example between 4% and 15% by weight of the tobacco smoke filtering material. The triethyl citrate may be present in an amount, for example, of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19 or 20% by weight of the tobacco smoke filtering material.

Triethyl citrate is also referred to herein as "TEC".

The tobacco smoke filtering material may be, for example, cellulose acetate tow, paper e.g. filtration paper, polypropylene or non-woven filter material. The tobacco smoke filtering material may be plasticised. The triethyl citrate may be included on or in the tobacco smoke filtering material.

The tobacco smoke filtering material (e.g. cellulose acetate tow) may include triethyl citrate as a plasticiser material [e.g. the tobacco smoke filtering material may be a plasticised filtering material, e.g. a filtering material (e.g. plasticised cellulose acetate tow) which has been plasticised by triethyl citrate]. The plasticised filtering material may be plasticised by triethyl citrate as sole plasticising agent, or plasticised using triethyl citrate in combination with other plasticisers, for example, Triacetin, triethyleneglycoldiacetate (TEGDA) or polyethylene glycol (PEG).

Thus, according to the present invention in a still further aspect there is provided a tobacco smoke filter or filter element comprising a tobacco smoke filtering material to which triethyl citrate plasticiser has been applied in an amount of between 1% and 30%, for example between 2% and 25%, for example between 3% and 20%, for example between 4% and 15% by weight of the tobacco smoke filtering material. The triethyl citrate may be present in an amount, for example, of 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% by weight of the tobacco smoke filtering material. The tobacco smoke filtering may be for example a rod of tobacco smoke filtering material, for example a rod of cellulose acetate tow.

In a still further aspect the present invention provides the use of triethyl citrate (TEC) in a tobacco smoke filter or filter element for selectively reducing one or more phenolic compounds in tobacco smoke.

The phenolic compound may be, for example, phenol, o-cresol, m-cresol or p-cresol.

The applicants have found that the inclusion of triethyl citrate in a tobacco smoke filter or filter element (as e.g. plasticiser) may provide a marked and unexpected reduction in the yield of phenols and in the phenohtar ratio in the tobacco smoke.

According to the present invention in a still further aspect there is provided a tobacco smoke filter or filter element comprising a tobacco smoke filtering material, and an additive selected from glyceryl tripropionate and triethyl citrate, wherein the additive is present in an amount of between 1% and 30% by weight of the tobacco smoke filtering material.

The additive may be present in an amount of between 2% and 25%, for example between 3% and 20%, for example between 4% and 15% by weight of the tobacco smoke filtering material. The additive may be present in an amount, for example, of 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19 or 20% by weight of the tobacco smoke filtering material. The tobacco smoke filtering may be for example a rod of tobacco smoke filtering material, for example a rod of cellulose acetate tow. Neither TEC nor Tripropionin have been found to give rise to any increase in acetic acid generation.

In filters and filter element according to aspects of the invention, the tobacco smoke filtering material may be over wrapped with a wrapper or plugwrap, for example a wrapper of paper, for example a wrapper of an air-permeable paper.

A filter element according to the invention may be used as a segment of a multi-segment filter, e.g. a COR filter as mentioned above, a dual, triple, other multiple filter, or a co-axial filter. Such filters are well known in the art. If the filter element is used as or in a segment of a multi- segment filter, it may be used at (or in) the mouth or buccal end segment of the filter, or as (or in) any other segment of the filter. A filter element according to the invention may be used on its own e.g. as a single segment filter (e.g. a monoacetate filter). Such filters are well known in the art.

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 of the filter towards 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 wrap exposed] or by a full tipping overwrap (which engages around the full filter length and the adjacent end of the tobacco rod). 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 present invention will now be illustrated with reference to the following Examples and the attached drawing in which FIGURE 1 is a schematic sectional side elevation view, not to scale, of an individual filter according to an aspect of the invention.

Example 1

Sample monoacetate cigarette filters were prepared using cellulose acetate tow, which was either unplasticised, or plasticised with one of the following plasticiser materials (triacetin, triethyl citrate, acetyl triethyl citrate, or triethyleneglycol diacetate), applied at different levels. The samples were made by methods which are well known to the skilled man, including steps of blooming the tow, application of plasticiser (if present) to the tow using a plasticiser applicator, and gathering and condensing the tow into rod form using a conventional rod making and wrapping garniture.

Tripropionin was included in some of the samples containing triacetin (the plasticiser normally used in the manufacture of cigarette filters).

The hardness values (defined as the compressed diameter of the filter rod as a percentage of the initial rod diameter, the compression of the rod being caused by a known weight applied through a circular foot for a specific period of time) and pressure drop (PD) (expressed in mm Water Gauge) were measured for all samples. A hardness value in excess of 85% is normally considered acceptable. The samples made and the hardness and pressure drop values obtained are summarised in Table 1 below.

Table 1

Sample filter cigarettes were assembled using the sample filters described in Table 1 and aged for three weeks. The yields of phenol, o-, m- and p-cresol (collectively termed the mono-hydroxyphenols) were then measured for all samples smoked under ISO conditions. The tar yields from the cigarettes were also measured in order that the changes in the ratios of phenols to tar could be assessed.

The results are summarised in Table 2.

Table 2

Samples according to the invention which include tripropionin (Samples/Examples 3, 4, 5, 7 and 8) mixed with a plasticiser such as triacetin demonstrate a further, unexpected, reduction in phenol yield as well as in the phenol:tar ratio. These samples/Examples have acceptable hardness and Pressure Drop characteristics.

Furthermore, it also can be seen that samples according to the invention which include Triethyl Citrate (Samples/Examples 9 and 10) give a much greater reduction in the yield of phenols and in the phenol:tar ratio than other plasticisers known for cigarette filter applications. These samples/Examples have acceptable hardness and Pressure Drop characteristics.

Example 2 - COR Filter

In the accompanying drawing Fig. 1 is a schematic sectional side elevation view, not to scale, of an individual filter according to an example of the invention, known as a Filtrona COR filter. The Fig.1 filter has a cylindrical buccal end filtering plug 2 which is of relatively high draw resistance (pressure drop) and low tar retention, a cylindrical upstream filtering plug 3 which is of relatively low draw resistance (pressure drop) and low tar retention, and a filter wrapper 4 engaged around the plugs to form a cavity 6 therebetween. The filter is 27 mm long and about 25 mm in circumference. The buccal end plug 2 is a 10 mm long preformed non- wrapped plug of plasticised cellulose acetate filaments gathered and bonded together. The plasticiser is triacetin which was mixed with 10% (by weight of the cellulose acetate) tripropionin prior to application to the cellulose acetate filaments (tow). The plug is made of a mixture of two tows from two respective bales, one bale being of 8/39 denier - i.e. 8 dpf (denier per filament) and 39 x 10³ total denier - and the other being of 7/34 denier to give a 7-8/73 denier product. The upstream end plug 3 is a 10 mm long preformed wrapped plug of plasticised cellulose acetate filaments - made from a 9/37 denier tow. Again the plasticiser is triacetin mixed with 10% (by weight of the cellulose acetate) tripropionin. The filter wrapper is 27 mm long to give a cavity 7 mm long extending between plugs 2 and 3 and is of air-permeable paper to provide for ventilation into cavity 6. The plugs 2, 3, are made by adaptations of known methods of WA and NWA plug manufacture to add tripropionin to the plasticiser. The complete filter element is made by known methods - e.g. that disclosed in EP 1555899A.

Example 3 - Selective Filtration Using Tripropionin

Samples of 'COR' filters (e.g. as described in EP 1555899) were made with and without additional tripropionin in order to assess the effects of the additive on the performance of this type of filter.

A total of four filter specifications were manufactured, all of which featured an 11mm length mouth end segment of non-wrapped acetate construction, a 5mm empty cavity and an 11mm wrapped cellulose acetate tobacco end segment. Details of the filter specifications are given in the table below. The level of triacetin (TA) plasticiser was kept at a constant 7%, whilst tripropionin (TP) was added at 10% as shown in Table 3 below.

5 Table 3

Cigarettes were assembled using these filters and then aged for 3 weeks prior to analysis. The yields of tar, nicotine, carbon monoxide and phenolic compounds were measured under ISO smoking conditions. In

10 addition, the yields of pyridine, quinoline and styrene - toxic compounds found in the semi-volatile fraction of cigarette smoke - were also measured. The results are given in Table 4 below.

15

20 Table 4

These results confirm the ability of a filters according to the invention (TP BS;TP TE; and TP ME) containing tripropionin and triacetin to significantly reduce the yields of phenols, pyridine, quinoline and styrene (both in absolute terms and expressed relative to the tar yield) as compared to a comparative filter (of the prior art) which contains only triacetin.

Claims

1. A tobacco smoke filter or filter element comprising a tobacco smoke filtering material, and an additive selected from glyceryl tripropionate and triethyl citrate, wherein the additive is present in an amount of between 1 % and 30% by weight of the tobacco smoke filtering material.

2. A tobacco smoke filter or filter element comprising a tobacco smoke filtering material; and glyceryl tripropionate.

3. A tobacco smoke filter or filter element comprising a tobacco smoke filtering material; glyceryl tripropionate; and triacetin.

4. A tobacco smoke filter or filter element according to any of claims 1 , 2 or 3 wherein the tobacco smoke filtering material is in the form of a rod.

5. A tobacco smoke filter or filter element according to any preceding claim wherein the filtering material is cellulose acetate tow, paper, polypropylene or non-woven filter material.

6. A tobacco smoke filter or filter element according to any preceding claim wherein the glyceryl tripropionate is included on or in the filtering material.

7. A tobacco smoke filter or filter element according to any preceding claim wherein the filtering material has been plasticised by a plasticiser material.

8. A tobacco smoke filter or filter element according to claim 7 wherein the plasticiser material is triacetin, triethyleneglycoldiacetate (TEGDA) or polyethylene glycol (PEG).

9. A tobacco smoke filter or filter element according to any of claims 7 or 8 wherein the glyceryl tripropionate is on, or mixed with, the plasticiser material.

10. A tobacco smoke filter or filter element according to any of claims 2 to 9 wherein the amount of glyceryl tripropionate is between 1% and

30% by weight of the tobacco smoke filtering material or plasticised tobacco smoke filtering material.

11. A tobacco smoke filter or filter element according to any preceding claim wherein the amount of glyceryl tripropionate is between 2% and 25% by weight of the tobacco smoke filtering material or plasticised tobacco smoke filtering material.

12. A tobacco smoke filter or filter element according to claim 1 or claim 4 including triethyl citrate in an amount of between 2% and 25% by weight of the tobacco smoke filtering material.

13. A tobacco smoke filter or filter element according to claim 12 wherein the filtering material is cellulose acetate tow, paper, polypropylene or non-woven filter material.

14. A tobacco smoke filter or filter element according to claim 12 or claim 13 wherein the triethyl citrate is included on or in the filtering material.

15. A tobacco smoke filter or filter element according to any of claims 1 , 4 and 12 to 14 wherein the filtering material is plasticised by the triethyl citrate.

16. A tobacco smoke filter or filter element comprising a tobacco smoke filtering material to which a triethyl citrate plasticiser has been applied in an amount of between 1 % and 30% by weight of the tobacco smoke filtering material.

17. A tobacco smoke filter or filter element substantially as hereinbefore described with reference to one or more of the Examples and/or the attached drawing.

18. A filter cigarette including a filter according to any preceding claim, or a filter which includes a filter element according to any preceding claim, joined to a wrapped tobacco rod.

19. Use of triethyl citrate (TEC) in a tobacco smoke filter or filter element for selectively reducing one or more phenolic compounds in tobacco smoke.

20. Use of glyceryl tripropionate (tripropionin) in a tobacco smoke filter or filter element for selectively reducing one or more phenolic compounds in tobacco smoke.

21. Use according to claim 19 or 20 in which the phenolic compound is one of phenol, o-cresol, m-cresol or p-cresol.

22. Use of glyceryl tripropionate (tripropionin) in a tobacco smoke filter or filter element for selectively reducing one or more of pyridine, quinoline and/or styrene in tobacco smoke.