Tobacco Smoke Filter

Abstract

The invention relates to a tobacco smoke filter which contains fibres which comprise regenerated cellulose (e.g. Lyocell) and an absorbent is introduced therein. More than one absorbent is introduced into the fibres of the tobacco smoke filter and/or the tobacco smoke filter contains an absorbent between said fibres. A higher charge of the absorbent can be obtained by means of said type of tobacco smoke filter.

Description

This invention concerns a tobacco smoke filter and also a smoking product having such a tobacco smoke filter.

Ingredients are removed from the mainstream smoke of smoking products such as cigarettes or cigarillos by using tobacco smoke filters which may contain adsorbents such as activated carbon, for example, for enhanced effectiveness.

Thus, EP 0 532 329 A2 discloses a cigarette having a paper filter incorporating activated carbon introduced in the papermaking operation. EP 1 028 637 A1 discloses a tissue filter comprising paper comprising activated carbon.

EP 1 223 821 A1 describes a triple filter having three segments. One of the segments is an adsorber chamber filled with an activated carbon mixture, while a second segment contains activated carbon in a carbon cloth. The manufacturing operation for this filter material is inconvenient and costly, and the material is very difficult to put into a useful form for a filter.

DE 199 17 614 A1 discloses a process for producing cellulosic articles, in particular fibers, that have high absorbency for polar molecules. The process takes the form of a dry-jet wet-extrusion process whereby cellulose is dissolved in an aqueous tertiary amine oxide and extruded. To obtain the desired adsorption properties, ion exchangers, for example based on polystyrene or polyacrylate resin, are added to the solution. A similar process is known from DE 100 53 359 A1. In this case, neutral adsorbers such as activated carbon, carbonized styrene-divinyl copolymers, molecular sieves from the group of the zeolites or silica gel are used to achieve an adsorption of a polar molecules. The fibers can be processed into papers, staple fibers or continuous filament fibers, and used in smoke filters.

Dry-jet wet-extrusion processes (solvent spinning processes) for producing cellulosic fibers or filaments are well known. Thus, U.S. Pat. No. 4,246,221 describes the production of lyocell fibers. Similar extruded fibers based on cellulose are known under the names of viscose and modal. In what follows, such cellulose materials will also be referred to as “regenerated cellulose”.

Lyocell fibers have already been used in cigarette filters. WO 95/35044 A1 discloses cigarette filters comprising lyocell staple fibers, WO 95/24520 A1 cigarette filters comprising crimped lyocell fibers, EP 0 731 651 A1 cigarette filters comprising paper comprising lyocell fibers and WO 95/35043 A1 cigarette filters comprising entangled continuous lyocell filaments.

The elucidated tobacco smoke filters are cellulosic and therefore superior to the widely used cellulose acetate filters in terms of environmental friendliness and biodegradability.

When such filters include adsorbers, however, the uptake capacity for the adsorber is limited or the manufacturing operation is inconvenient and costly.

It is an object of the present invention to provide a cellulosic tobacco smoke filter having a high adsorber load and providing an enhanced reduction in smoke constituents without being inconvenient and costly to manufacture.

We have found that this object is achieved by a tobacco smoke filter having the features of claim 1. Claim 14 concerns a smoking product comprising such a tobacco smoke filter. Advantageous embodiments of the invention are apparent from the remaining claims.

The tobacco smoke filter of the present invention comprises fibers which comprise regenerated cellulose (preferably lyocell fibers, viscose fibers and/or modal fibers) and incorporate adsorbent. According to the present invention, the fibers of the tobacco smoke filter incorporate more than one adsorbent and/or the tobacco smoke filter includes adsorbent between the fibers.

The tobacco smoke filter of the present invention facilitates high loading with adsorbent, since, first, the regenerated cellulose fibers (i.e., the fibers having regenerated cellulose) include one or more adsorbents and, secondly, adsorbent may also be provided between the fibers of the tobacco smoke filter. Since the adsorbent incorporated in the fibers is bound to the fibers, it is not released as dust in the course of the handling of the tobacco smoke filter. Provided the amount of adsorbent between the fibers does not exceed a limit determined by practical experience, the tobacco smoke filter also holds the adsorbent between the fibers without the occurrence of contamination. If, by contrast, the total amount of adsorbent capable of being taken up by the tobacco smoke filter of the present invention were attempted to be incorporated between the fibers, adsorbent would snow out of the tobacco smoke filter as it was being handled.

As well as high adsorber loading, the invention also facilitates optimal mixing or combination of selective adsorbents, since the adsorbents can be incorporated in the tobacco smoke filter in various ways (in the fibers, between the fibers). This makes it possible to achieve an improved reduction in smoke constituents.

Surprisingly, it has emerged that the adsorption capacity (efficacy) of the adsorbents is not adversely affected by the manufacturing operation of the regenerated cellulose fibers, i.e., through embedding in the fibers.

The regenerated cellulose fibers are preferably obtained from beechwood, hemp and/or flax fibers.

Compared with the cellulose acetate mostly used in conventional filters, regenerated cellulose (lyocell for example) has an environmentally friendly manufacturing operation. Moreover, the biodegradability of regenerated cellulose is distinctly better than that of cellulose acetate.

The tobacco smoke filter of the present invention is less inconvenient and costly to manufacture than the conventional filters having a high loading of adsorbent, for example the triple filter known from EP 1 223 821 A1.

This invention provides numerous ways to equip the tobacco smoke filter with various adsorbents. For instance, two or more different varieties of adsorbent can be incorporated in one and the same variety of regenerated cellulose fiber. It is also possible to provide various varieties of adsorbent in different regenerated cellulose fibers, for example lyocell fibers produced using one variety of adsorbent and lyocell fibers produced using another variety of adsorbent. Hybrid forms are likewise conceivable. In addition, the tobacco smoke filter can include adsorbent between the fibers, as mentioned before, and again a mixture of adsorbents is possible.

The regenerated cellulose fibers can be present in the tobacco smoke filter in different forms, for example as staple fibers or as continuous filament fibers, but also in an already consolidated state in the form of fibrous nonwoven webs, wovens or papers. Hybrid forms are likewise possible.

Useful adsorbents include numerous substances or classes of substances, examples being activated carbons, aluminum oxides, aluminum hydroxides, mixtures of aluminum oxide and silicon oxide, aluminosilicates in oxide and/or hydroxide form, magnesium silicates, hydrotalcite, ion exchangers, ion exchanger resins, molecular sieves, silica gels, natural minerals, synthetic minerals, argillaceous earths, zeolites, bentonites, diatomaceous earth, meerschaum, superadsorbents and also mixtures thereof. Superadsorbents (SAPS) are polyacrylates, carbonized polyacrylates and also adsorbents based on starch. Particular preference is given inter alia to aluminosilicates in oxide and/or hydroxide form.

In advantageous embodiments of the present invention, regenerated cellulose fibers incorporate at least one smoke-influencing additive. Examples of useful additives include flavor chemicals, vitamins, catalysts or free radical scavengers. The use of regenerated cellulose provides a simple way to endow the fibers with one or more desired additive in the course of fiber production.

In a preferred embodiment, the tobacco smoke filter comprises two or more fibrous nonwoven webs comprising regenerated cellulose fibers, the fibrous nonwoven webs comprising two or more different adsorbents in the regenerated cellulose fibers. The fibrous nonwoven webs are preferably bonded together, for example by embossing, needling or hydroentangling. Additionally, at least one adsorbent is included between the fibers in at least one of the fibrous nonwoven webs and/or between fibrous nonwoven web plies.

In another preferred embodiment, the tobacco smoke filter comprises a paper having, in the paper raw material, regenerated cellulose fibers incorporating adsorbent. The paper can furthermore be produced with additional adsorbent in the pulp.

In one version, the tobacco smoke filter comprises paper comprising as paper stock lyocell loaded with at least one adsorbent, preferably up to 75% by weight of lyocell, based on the final paper. The lyocell fiber preferably includes up to 50% by weight of adsorbent.

The fraction of adsorbent based on the total mass of the tobacco smoke filter is preferably in the range from 20% by weight to 90% by weight or in the range from 50% by weight to 90% by weight and more preferably in the range from 50% by weight to 70% by weight, whereby a high loading of the tobacco smoke filter with adsorbent is achieved.

When the tobacco smoke filter includes just one segment, this segment has the above-elucidated features. Tobacco smoke filters of the present invention which have a plurality of segments are likewise conceivable. In this case, at least one of the segments has the elucidated features; in addition, segments of conventional kind can be present. Preferably, the segments have a conjoint wrapping.

Preferably, the tobacco smoke filter has a wrapping. But it is also conceivable to produce tobacco smoke filters of the present invention in unwrapped form (for example by inclusion of glue or of a meltable fibrous fraction (bicomponent fibers)) and, for example, to only circumscribe them with a paper during the joining to cigarette rods.

Smoking products contemplated for equipping with the tobacco smoke filter of the present invention include in particular cigarettes and cigarillos. A further possibility is to use paper sleeves which are tipped at one end with a tobacco smoke filter of the present invention and into which cut tobacco can be introduced from the other end.

The invention will now be further elucidated with reference to operative examples.

Lyocell fibers can be produced by the process described in DE 199 17 614 A1 and DE 100 53 359 A1 and be loaded with adsorbent in the course of their process.

EXAMPLE 1

A staple fiber mixture consisting of equal portions of (a) lyocell staple fibers having a fiber length of about 6 mm and loaded with 50% by weight of Siralox 40 aluminosilicate (from Sasol Ltd.), and also (b) lyocell staple fibers having a fiber length of about 6 mm and loaded with 50% by weight of zeolite HY, was additionally admixed, by the process described in EP 1 354 522 A2, with granular activated carbon in an amount of 10 mg per mm of filter length. After mixing in an air stream, the material was formed into a filter body 7.8 mm in diameter. Then, the filter body was wrapped with paper and cut to a filter rod length of 90 mm. The particle size of the granular activated carbon was 30 to 70 US mesh, corresponding to a particle diameter of about 0.2 mm to 0.6 mm. The total load of adsorbent in the filter amounted to 17.5 mg per mm of filter length.

EXAMPLE 2

Two fibrous nonwoven webs were produced from loaded lyocell staple fibers. One fibrous nonwoven web included an adsorber load of 50% by weight of Siralox 40 (Sasol Ltd.) in the lyocell fibers to be used in its production. The other fibrous nonwoven web included a loading with 50% by weight of HY zeolite in its fibers. Following addition of granular activated carbon atop one of the two plies of fibrous nonwoven web, the two fibrous nonwoven webs were bonded to each other by needling.

The bonded material formed from the needled fibrous nonwoven webs was, in a paper filter machine from Burghart, embossed (i.e., pleated into longitudinal folds) and formed into a filter body which was subsequently wrapped with paper and cut into pieces of filter rod length. The total load of adsorbent in the filter amounted to 17.5 mg per mm of filter length.

EXAMPLE 3

Lyocell staple fibers were loaded with 50% by weight of Siralox 40 (Sasol Ltd.) and used as paper raw material. In fact, 75% of the paper pulp was represented by loaded lyocell fibers. The pulp was additionally admixed with 50% by weight of activated carbon powder in the course of further papermaking. The paper produced in this way had a total adsorbent content of at least 60% by weight.

This paper was, in a paper filter machine from Burghart, embossed (i.e., pleated into longitudinal folds) and formed into a filter body which was subsequently wrapped with paper and cut into pieces of filter rod length.

Such papers (tissue) comprising lyocell staple fibers (up to 75% of loaded lyocell staple fiber, based on the total mass of the paper) loaded with up to 50% by weight of adsorbent (including activated carbon for example) achieve a particularly high total adsorbent content (namely up to 70% by weight of adsorbent, for example activated carbon, based on the total mass of the paper) when—as in the example—the pulp likewise has adsorbent added to it, for example up to 50% by weight of activated carbon powder. The resulting advantages include an enhanced adsorbent content and an enhanced condensate retention by fibrillated lyocell fibers.

EXAMPLE 4

Lyocell staple fibers were loaded with 50% by weight of adsorbent (Siralox 40 from Sasol Ltd. or, alternatively, activated carbon) and used as paper raw material. In fact, 75% of the paper mass was represented by loaded lyocell fibers. The paper produced in this way had a total adsorbent content of 37.5% by weight. The rest of the processing of the paper to form a filter body was carried out as in Example 3.

Claims

1. A tobacco smoke filter comprising:

fibers having regenerated cellulose and incorporating adsorbent therein, wherein the tobacco smoke filter presents additional adsorbent properties selected from the group consisting of incorporating more than one adsorbent in said fibers, including adsorbent between said fibers, and combinations thereof.

2. The tobacco smoke filter of claim 1,

at least some of said regenerated cellulose fibers incorporating two or more different adsorbents.

3. The tobacco smoke filter of claim 1,

said adsorbent comprising two or more different adsorbents incorporated into different fibers having regenerated cellulose.

4. The tobacco smoke filter of claim 1,

said regenerated cellulose fibers comprising at least one fiber species selected from the group consisting of lyocell fibers, viscose fibers, and modal fibers.

5. The tobacco smoke filter of claim 1,

said regenerated cellulose fibers being present in at least one form selected from the group consisting of staple fibers, continuous filament fibers, fibrous nonwoven webs, papers, and wovens.

6. The tobacco smoke filter of claim 1,

said adsorbent comprising at least one substance selected from the group consisting of activated carbons, aluminum oxides, aluminum hydroxides, mixtures of aluminum oxide and silicon oxide, aluminosilicates in oxide and/or hydroxide form, magnesium silicates, hydrotalcite, ion exchangers, ion exchanger resins, molecular sieves, silica gels, natural minerals, synthetic minerals, argillaceous earths, zeolites, bentonites, diatomaceous earth, meerschaum, and superadsorbents.

7. The tobacco smoke filter of claim 1,

at least some of said regenerated cellulose fibers incorporating at least one smoke-influencing additive,

said at least one smoke-influencing additive preferably comprising at least one substance selected from the group consisting of flavor chemicals, vitamins, catalysts, and free radical scavengers.

8. The tobacco smoke filter of claim 1,

wherein two or more fibrous nonwoven webs comprise said regenerated cellulose fibers,

said fibrous nonwoven webs comprising two or more different adsorbents in the regenerated cellulose fibers.

9. The tobacco smoke filter of claim 8,

at least one of said adsorbents being included in a manner selected from the group consisting of between the fibers in at least one of the fibrous nonwoven webs, between fibrous nonwoven web plies, and combinations thereof.

10. The tobacco smoke filter of claim 1,

said regenerated cellulose fibers being in paper raw material of a paper.

11. A tobacco smoke filter comprising:

paper comprising as paper raw material lyocell loaded with at least one adsorbent.

12. The tobacco smoke filter of claim 1,

wherein the fraction of adsorbent based on the total weight of the tobacco smoke filter is in the range from 20% by weight to 90% by weight.

13. A tobacco smoke filter comprising:

a plurality of segments, with at least one of the segments having the features of claim 1 and the segments preferably having a conjoint wrapping.

14. A smoking product comprising:

a tobacco smoke filter as claimed in claim 1.

15. The smoking product of claim 14,

wherein the smoking product is selected from the group consisting of cigarettes, cigarillos, and filter paper sleeves.

16. The tobacco smoke filter of claim 8,

said fibrous nonwoven webs being bonded together.

17. The tobacco smoke filter of claim 10,

said paper being produced with additional adsorbent in the pulp.

18. The tobacco smoke filter of claim 11,

wherein the paper is loaded with the at least one adsorbent up to 75% by weight of lyocell, based on the final paper.

19. The tobacco smoke filter of claim 12,

wherein the fraction of adsorbent based on the total weight of the tobacco smoke filter is in the range from 50% by weight to 90% by weight.

20. The tobacco smoke filter of claim 19,

wherein the fraction of adsorbent based on the total weight of the tobacco smoke filter is in the range from 50% by weight to 70% by weight.