EP0675691A1

EP0675691A1 - A filter cigarette

Info

Publication number: EP0675691A1
Application number: EP94903211A
Authority: EP
Inventors: Erik Gunnar Andersson; Eva Margareta Curvall; Curt R. Enzell
Original assignee: Svenska Tobaks AB
Current assignee: Svenska Tobaks AB
Priority date: 1992-12-22
Filing date: 1993-12-17
Publication date: 1995-10-11
Also published as: FI953078A; NO952358L; SE500634C2; NO300112B1; JPH08505051A; RU2113809C1; FI953078A0; NO952358D0; AU5723894A; SE9203878L; SE9203878D0; WO1994014346A1

Abstract

A filter cigarette includes a rod (1) of smokable material enclosed in a burnable envelope (2) and a filter connected to one end of the rod. The filter is a multi-component filter and includes one part (3) which contains activated carbon (6) and at least one part (4) which contains solely cellulose-based fibrous filter material, and is ventilated to a degree of ventilation of at least 50 %.

Description

A Filter Cigarette

The present invention relates to a filter cigarette which, when smoked, will deliver much smallor amounts of undesirable components to the smoker than earlier known filter cigarettes of a similar type.

When composing tobacco products, both for smoking and for other forms of consumption, it has long been endeavoured to restrict to the greatest possible extent the amounts of undesirable substances that can be transmitted to the consumer. However, this endeavour has often been in conflict with the endeavour to pro¬ duce products which are acceptable to the consumers, since many of those components which are contained naturally in the tobacco or which are formed as the tobacco burns contribute to the taste and the aroma of the product.

It has long been endeavoured to reduce the concentra¬ tions of undesirable substances in the main stream smoke from smoking articles, and then particularly cigarettes, with the aid of a filter located at the mouth end of the smoking articles. The literature de- scribes many materials and constructions for such filters.

The filter materials most widely used in the manu¬ facture of cigarettes include fibrous cellulose-based materials, such as crepe paper, regenerated cellulose in different forms, and above all cellulose acetate fibres. The primary purpose of such fibrous filter materials is to remove some of the aerosol "tar" , from the smoke. Cigarette filters may also include different additives which are intended to capture gaseous smoke components. Different types of activated carbon are best known in this regard and the ones most commonly used. Activated carbon can be produced from a number of different starting materials, resulting in end products which have greatly varying properties. The person skilled in this art is also aware of many dⁱfferent ways of treating activated carbon in order to modify the ability of the carbon to capture gaseous sub¬ stances. The inclusion of activated carbon in cigarette filters results in the capture of both gaseous sub¬ stances and volatile tar components, to varying degrees. Different types of activated carbon also affect the taste and the aroma of the smoke to varying degrees. Activated carbon can hardly be used alone as a filter material, but must be combined with some other material, preferably fibrous material.

A cigarette filter which includes activated carbon or some other active substance is normally produced in the form of a multi-component filter in which the active substance is distributed in that part of the filter which is positioned in the immediate vicinity of the tobacco part of the cigarette, or alternatively the active substance is distributed in a section that is located between two filter parts comprised of fibrous material. Both of these general filter constructions are applicable to obtaining a filter constructed in accordance with the present invention.

The action mechanism of a filter is assumed to be that some of the particles of the aerosol are adsorbed on the surface of the fibrous filter material, and tht their components are subeseguently absorbed into the fibre material. In contrast, the activated carbon func¬ tions primarily to adsorb gaseous components present in the smoke.

A filter of this kind constructed in accordance with the two component-model is known under the registered trademark CURZEL.

It is often endeavoured to improve the degree of filtration of a cigarette filter by introducing so- called ventilation. Ventilation implies that small holes are made in the papers which embrace the filter, or that air-pervious papers are used. Ventilation results in secondary, diluting air being drawn in through the air-permeable areas of a cigarette filter periphery while drawing a puff on the cigarette, at the same time as a part of the total puff volume passes directly through the glowing end of the cigarette.

The amount of undesirable components of cigarette smoke can be restricted to a limited extent, by using differ¬ ent types of tobacco, or by using a specially treated tobacco. These measures result in measurable changes in the amount of smoke particulate matter, tar, but only marginal changes in the gaseous components.

According to a decision reached by the European Common Market as from 1993, the highest amount of tar that is allowed to be delivered by cigarettes is restricted to 15 mg, whereas cigarettes which deliver from 5 to 12 mg tar are most common on the Swedish market. However, there are a few types of cigarettes which give ultra- low smoke yields down to 1 mg tar. The amounts of tar produced can be determined by standardized methods, such as by ISO standards 3308 and 4387.

Despite the extensive work that has gone into develop¬ ing cigarettes which produce lesser quantities of undesirable smoke components, there is still need for improvement in the field. These improvements are achieved to a great extent by means of the present invention. Accordingly, the present invention provides a filter cigarette comprising a smokable material which is en¬ closed in a burnable envelope and a filter which ad¬ joins the smokable material, said filter ciαarette being characterized in that the filter is a multi- component filter. The filter is either constructed as a two-component filter of which one component is com¬ prised of cellulose-based fibrous filter material and activated carbon, and is connected nearest to the smok- able material, and a cellulose-based, fibrous filter material which contains no activated carbon. Alter¬ natively, the filter is a three-component filter which includes a section which contains activated carbon or the aforesaid combination of fibrous filter material and activated carbon, which is connected at each end to a component of fibrous filter material not containing carbon particles.

All components of an inventive filter construction are cylindrical and have a circumference which is essenti¬ ally identical to the circumference of the rod of smok¬ able material. A filter of this kind constructed in accordance with the invention is ventilated to a venti¬ lation degree of at least 50%, measured by measuring equipment typical to the tobacco industry.

The invention will now be described in more detail with reference to three different embodiments of an inven¬ tive filter cigarette shown schematically in the accompanying drawing. The three Figures are longitudi¬ nal section views of a part of a filter cigarette at the mouth end thereof. Corresponding components have been identified by the same reference signs in the Figures.

Figure 1 shows part of a cigarette which includes a rod of smokable material 1, especially tobacco, which is enclosed in a burnable envelope 2. Located at the mouth end of the cigarette is a filter which comprises two filter components 3 and 4. In the illustrated case, the forward filter component 3 contains a fibro'is filter material 5, identified by zig-zag lines, in mixture with particles of activated carbon 6, identified by dots. The rearward filter component 4, nearest to the mouth end of the cigarette, contains solely a fibrous filter material 7.

Figure 2 illustrates another embodiment in which the filter is comprised of three filter components 8, 9 and 10. In this case, the forward filter component 8 in¬ cludes fibrous filter material 7 and the intermediate filter component 8 contains particles of activated carbon 6 but no fibrous filter material. The rear com¬ ponent 10, nearest to the mouth end of the cigarette, contains solely fibrous filter material 7.

Figure 3 illustrates a third embodiment in which the filter is comprised of three filter components 11, 12 and 13. In this case, the forward and the rearward filter components 11 and 13 respectively contain solely fibrous filter material, corresponding to the embodi- ment illustrated in Figure 2. The intermediate filter component 12, on the other hand, contains a mixture of fibrous filter material 5 and particles of activated carbon 6, corresponding to the filter component 3 of the Figure 1 embodiment.

The filter components of the three different embodi¬ ments are ventilated to an extent of at least 50% totally. This ventilation can be achieved by providing perforations in the wrapping materials of the filter or by forming the filter wraps from a porous material. The manner in which filter ventilation is achieved is well known to the person skilled in this art and is not therefore shown in detail in the drawings.

The smokable material is preferably tobacco, which may be processed according to current standards within the industry. Minor quantities of aromatic and flavouring additives, and also other additives, may be added to the tobacco material, in accordance with standard practices in the cigarette industry. The tobacco may be comprised of specially-treated tobacco, either totally or in part, such as volume-expanded tobacco or re¬ constituted tobacco.

The burnable envelope is primarily comprised of conven¬ tional cigarette paper. It may, however, alternatively be comprised totally or partially of tobacco material, such as reconstituted tobacco. The envelope may have been made naturally porous in manufacture or may have been provided with microscopic perforations after manu¬ facturing the material. Filter cigarettes having burnable envelopes of tobacco material are in some countries classified as "cigars" or "cigarillos". Such products, however, are also included by the present invention.

The filter connected to the burnable material is em¬ braced by papers which have been made naturally porous in manufacture or in which one or more of the papers has or have been provided with perforations either during manufacture of the paper or after fitting the filter to the tobacco rod in the cigar manufacturing process.

These porous or perforated papers which embrace the filter provide ventilation as a puff is taken on the cigarette, and the degree of ventilation is preferably at least 70% and may be as high as 80% or even higher, as measured by conventional methods and equipment which are well-known in the cigarette industry-

In the case of one particularly preferred embodiment, the smokable material is comprised of a tobacco mate- rial and, as determined by standard methods, delivers at most about 5 mg tar at the aforesaid ventilation ranges, said filter comprising any one of the aforesaid three multi-filter constructions.

The cellulose-based filter material may be comprised of any of the materials earlier known for this purpose. It is particularly preferred that the filter material is a creped paper, regenerated cellulose or fibres of cellu¬ lose acetate. Mixtures of cellulose-based filter mate- rials may also be used.

The activated carbon used may be any type of activated carbon having a vegetable, mineral or animal origin and being available commercially. The carbon may have been subjected to different chemical or physical treatment processes, in order to modify the carbon in different respects and therewith to improve its general or speci¬ fic adsorption properties. Carbon of mineral origin, and then particularly from coal, has been found to give particularly beneficial results.

Analyses have shown that the amount of gaseous smoke components, many of which are undesirable, which are delivered to the smoker are greatly reduced with a filter cigarette that is constructed in accordance with the invention, in comparison with other filter cigaret¬ tes. This reduction. is surprisingly high in comparison with what is to be expected with knowledge of present- day standpoints of technique. The use of the described, preferred filter in a cigarette which produces about 6 mg of tar per cigarette and has a degree of ventilation of about 50% reduces the amount of undesirable compo- nents in the gas phase by about 50% compared to a refe¬ rence cigarette which differs solely by having the described filter replaced by a cellulose acetate filter. On the other hand, the use of the inventive preferred filter having a degree of ventilation of about 80% and a tar emission of about 1 mg with each cigarette results in a reduction in the amount of un¬ desirable components in the gas phase by all of 78%, in comparison with a cigarette which includes solely an acetate filter but which is identical in all other re¬ spects.

This percentage reduction with a higher degree of ven¬ tilation and therewith a lower tar emission is totally surprising. It is probable that one skilled in this art who has knowledge of the performance of the inventive filter with a cigarette that has a lower degree of ventilation and a higher tar content would expect a reduction of at most 50% of the volatile components when increasing the ventilation.

The main stream smoke from the inventive filter cigarettes has been subjected to comparison tests with regard to the concentrations of undesirable components in the gas phase and with respect to cytotoxicity. These tests are described in more detail in the following:

The test cigarettes and reference cigarettes contained the same tobacco material, furnishing a tar yield of about 1 mg/cigarette, a nicotine yield of about 0.2 mg/cigarette and a CO yield of about 1 mg/cigarette, determined by standard methods.

The inventive cigarette filter consisted of two parts, one part containing a mixture of cellulose acetate fibres and activated carbon derived from mineral coal, and one part containing only cellulose acetate fibres and which was located nearest to the mouth end of the cigarette. The filters of the reference cigarettes contained only conventional cellulose acetate fibres. The degree of ventilation for both the inventive ciga¬ rettes and the reference cigarettes was about 80%.

1. Chemical Gas-Phase Analysis

The concentrations of a number of gas-phase components belonging to different functional groups were deter¬ mined quantitatively with the aid of high-resolution gas chro atography, in a conventional manner. The re¬ duction in the concentration of gas-phase components for an inventive filter cigarette is given in percent in the following Table 1 in relation to the reference cigarette.

Table 1

Chemical gas-phase: Reduction of gas-phase components

(%) compared with reference

Chemical group (n = the number Reduction, % of specific compounds within each group) :

Saturated hydrocarbons (n=10) 52

Unsaturated hydrocarbons (n=6) 75

Aromatic hydrocarbons (n=3) 86

Aldehydes (n=6) 71 Alcohols (n=l) 66

Nitriles (n=3) 90

N-heterocycles (n=4) 95

Ketones (n=ll) 88

Mean value (n=44) 78

2. Cytotoxicity Test 10

The cytotoxicity was determined in a known manner, by measuring the ability of the cigarette smoke to induce failure for single V79 cells from Chinese hamster lung to form colonies, (Jenssen, D., in: G.J. Kiλbey, M. Legator, W. Nichols and C. Ramel (Eds) , Handbook of Mutagenicity Test Procedures, Elsevier Science Pub¬ lishers BV, Amsterdam (1984), pp. 269-290).

The cytotoxicity is determined on fresh (non-condensed) gas-phase and on fresh whole smoke. The results are given in the form of an IC-50% value, i.e. as the number of cigarette puffs which reduce the number of colonies formed by 50% relative to an untreated control group. The results are set down in the following Table 2.

Table 2

Biological tests of gas-phase and whole smoke: Cytoxicity in V79-cellε

Gas-Phase Whole Smoke

Cigarette IC-50% value IC-50% value (puffs) (puffs)

According to the invention 29.8 (0.2) 16.7 (2.2) Reference cigarette 11.0 (1.7) 8.5 (1.5)

It can be seen from the results presented in the Table that the cytoxicity of the gas-phase from the reference cigarette is nearly three times higher than the toxici- ty of the gas-phase of the inventive cigarette, and that the cytotoxicity of the whole smoke from the re¬ ference cigarette is essentially twice the cytoxicity of the whole smoke from the inventive cigarette, in the test carried out.

In summary, it has thus been shown that filter cig¬ arettes constructed in accordance with the present invention exhibit a pronounced reduction in the concen¬ tration of undesirable components in the gas-phase and in a markedly lower cytotoxicity of the gas-phase and the whole smoke in comparison with reference cigarettes which differ solely with regard to the filter used. The inventive filter cigarettes thus represent a consider¬ able technical advance with regard to the present standpoint of techniques.

This step forwards in the art is completely surprising to the skilled person, since the percentage reduction in the concentration of undesirable gas-phase compo¬ nents is much greater than that which is obtained when making a comparison between corresponding filters on cigarettes which have a lower degree of ventilation and a higher tar yield, as illustrated in the aforegoing. With a more diluted gas-phase, obtained with a higher degree of ventilation, a lower rather than a higher percentage degree of reduction would be expected. This unexpected effect is obtained with filter cigarettes constructed in accordance with the present invention.

Although the invention has been described in the afore¬ going with reference to a specific example of a filter cigarette constructed in accordance with the invention, it will be understood that the invention is not res¬ tricted to solely this particular embodiment, but in¬ cludes all conceivable variations and modifications within the scope of the following Claims.

Claims

1. A filter cigarette comprising a rod of smokable material which is enclosed in a burnable envelope, and a filter connected to one end of the rod, c h a r a c t e r i z e d in that the filter is a multi-component filter comprising a component which contains activated carbon and at least one component which contains cellulose-based fibrous filter material; and in that the filter, as mounted on a cigarette, has a degree of ventilation of at least 50%.

2. A filter cigarette according to Claim 1, c h a r ¬ a c t e r i z e d in that the filter is comprised of a forward component which contains cellulose-based fibrous filter material in mixture with activated carbon, and a rear component located nearest to the mouth end of the cigarette and containing solely the fibrous filter material.

3. A filter cigarette according to Claim 1, c h a r ¬ a c t e r i z e d in that the filter is comprised of three components, a forward component which contains solely the fibrous filter material, an intermediate component which contains solely activated carbon, and a rear component which contains solely the fibrous filter material.

4. A filter cigarette according to Claim 1, c h a r - a c t e r i z e d in that the filter is comprised of three components, a forward component which contains solely the fibrous filter material, an intermediate component which contains the fibrous filter material in mixture with activated carbon, and a rear component which contains solely the fibrous filter material.

5. A filter cigarette according to any one of Claims 1-4 , c h a r a c t e r i z e d in that the activated carbon is of a mineral origin, particularly a coal origin.

6. A filter cigarette according to any one of Claims 1-5, c h a r a c t e r i z e d in that the smokable material is tobacco.

7. A filter cigarette according to any one of Claims 1-6, c h a r a c t e r i z e d in that the cigarette yields at most 5 mg tar as determined by a standard smoke analysis.

8. A filter cigarette according to any one of Claims 1-7, c h a r a c t e r i z e d in that the filter has a degree of ventilation of at least 70%.

9. A filter cigarette according to any one of Claims 1-8, c h a r a c t e r i z e d in that the cellulose- based fibrous material is crepe paper, regenerated cellulose or cellulose acetate fibres.