Tobacco Smoking Filter or Filter Element with a Content of Adjuncts

Abstract

A tobacco smoking filter is disclosed, with adjunets on the surface in the form of fibres filaments or films and whereby the drawing resistance of the tobacco smoking filter and the mass of the adjuncts in the tobacco smoking filter meet the following equation (I) Mad/Δp>1 mg/daPA (I), where Δp is the drawing resistance [daPA], applied as a value calculated with a 7.8 mm filter diameter and Mad [mg] is the mass of the adjuncts. The tobacco smoking filter comprises channel structures and the filer material is provided as a planar material. Said tobacco smoking filter has a low draw resistance on smoking with a particularly good filtration effect and is relatively simple to produce.

Description

The invention relates to tobacco smoke filters or filter elements, which are constructed in one piece and contain fibers, filaments or films based on polymers or polymer mixtures, which can be spun or processed into films, and contain one or more additives.

Tobacco smoke filters of the above type are known in the art. In this connection, “in one piece” is to be understood that the tobacco smoke filters are constructed uniformly in the longitudinal axial direction and can be produced without further limiting filter elements. Here there is a relevant difference from so-called “chamber filters”, for which an outwardly limited chamber is created by an enveloping paper between filter elements of conventional filter material, disposed at a distance from one another in the longitudinal direction. This chamber may be filled with additives, such as granular activated charcoal.

There has been no lack of attempts to design filter construction, which permit a particularly efficient utilization of porous elements. The chamber filter construction named has disadvantages in the efficient utilization of the included activated charcoal. Because of the limitation to the degree, to which the chamber can be filled, and due to the comparatively coarse granulation of the activated charcoal, a portion of the smoke passes through that part of the chamber, which is not filled, and, accordingly, does not come into direct contact with the activated charcoal. The particle size of the activated charcoal cannot be reduced at will, since this would result in an increase in the resistance to airflow, which is not acceptable to the smoker. The filter construction, described in the EPA-O 014 477 behaves more advantageously in this respect. For this construction, the granular activated charcoal is scattered into a filter element in a manner that assures an approximately homogeneous distribution of the activated charcoal particles in the fibers or filaments of the filter material, which, in turn, are distributed homogeneously. Even though the formation of a bypass can be excluded in this manner, coarsely grained additives are nevertheless required, in order to ensure that the aforementioned particles are fixed in the tobacco smoke filter. The disadvantages, ascribed to coarsely grained activated charcoal, are therefore also exhibited by this filter construction.

The following may be mentioned in connection with tobacco smoke filters or their use and as a background for the invention, which is described below. At their mouth end, filter cigarettes are provided with tobacco smoke filters, which intercept at least a portion of the combustion products of the tobacco of the cigarette and, by so doing, prevent inhalation of the combustion products during smoking. On the other hand, a tobacco smoke filter should affect the taste of the tobacco smoke, so that it is evaluated positively by the smoker. For a portion of filter cigarettes, the tobacco smoke filter is treated with a porous, particulate additive, which increases the filtration performance of the tobacco smoke filter or the tobacco smoke filter elements in comparison to a tobacco smoke filter without the particulate additives. This effect frequently can be explained owing to the fact that the porous additives preferentially adsorb gaseous combustion products at their inner surface and, by so doing, reduce their concentration in the smoke. For the most prominent representatives of this type of cigarette filters, activated charcoal is used as porous, particulate additive. Other tobacco smoke filters, such as those described in the DE-A-2 658 479, contain oxides, hydroxides and/or oxide hydrates of different metals, such as silicon, aluminum, magnesium, iron and/or titanium. The accessibility of such porous, particulate additives for the gaseous smoke components is of decisive importance for their effectiveness. For example, it has turned out the filter performance of finely divided porous materials especially is better than that of coarser particles. Further disadvantages of the chamber filters addressed are to be seen therein that the cost of manufacturing them are high.

Other known filter constructions indicate possibilities of binding also finely grained additives in the tobacco smoke filters. U.S. Pat. Nos. 3,043,736 and 2,881,770 describe a tobacco smoke filter consisting of a bundle of endless crimped filaments of cellulose acetate, which has been combined into a filter rod by enveloping paper, the individual filaments being coated with finely divided activated charcoal. The possible devices for applying the finely particulate additives can be divided into devices a) for applying the additives from a suspension in an aqueous phase or a volatile organic carrier or a plasticizer fluid, b) for blowing-on the additives, which consist of small particles and may previously be wetted with an adhesive or a plasticizer, c) for applying from a latex emulsion and d) for applying the additive, in that a bundle of filaments or threads, previously wetted with adhesive or plasticizer, is passed through a whirled-up bed of finely divided activated charcoal. In this respect, reference is made to the DE 127 4 946.

The tobacco smoke filters, produced according to the above method, are distinguished owing to the fact that the filaments, loaded with additives, are oriented preferably longitudinally and are bound to one another alternately at statistically distributed contact sites by means of the action of an adhesive or plasticizer, so that essentially longitudinal, small spaces, distributed uniformly over the filter, are created between adjacent filaments by the flow of the tobacco smoke.

The examples listed make it clear that the tobacco smoke filters, so produced and treated with particulate additives, have a high resistance to the flow of air, which is similar to that of comparison filters, in which particulate additives have not been enmeshed. Accordingly, filters, which have a uniformly high mass of additives as well as a low resistance to airflow, cannot be produced according to these methods.

Alternatively, paper filters, doped with activated charcoal, are used in tobacco smoke filters. These contain activated charcoals of small particle size, which are bound to the paper during the paper-manufacturing process. At the same time, during the production of the filter material, a fabric is formed, rolled onto bobbins and subsequently sent to the processor. The filter or cigarette manufacturer unrolls the material from the bobbins and forms it into a rod-shaped product, in order to consolidate it then transversely axially in the mold part of the filter rod machine, envelop it in paper and cut it to the ultimate length of the filter rods. In addition, the fabric usually, but not necessarily, is wrinkled parallel to the direction in which it runs through the creping device, before it is shaped into a rod. With that, a reduction in the density of the material on the one hand, and an effect on the resistance to the passage of air through the filter on the other, are achieved. A channel structure, in which longitudinally aligned, channel-shaped regions of low material density extend over a considerable portion of the filter or filter element, is characteristic of such filters produced by folding two-dimensional materials. These channels are bounded by filter material of a higher material density. The comparatively low resistance of these filters to the passage of air can be attributed essentially to this structural property.

However, when these two-dimensional filters, which do not consist or consist only partially of cellulose acetate, are used, the taste of the smoke frequently is evaluated as being negative. In addition, such filters do not exhibit the specific retention performances for phenols or nitrosamines, which are known from cigarette filters of cellulose acetate.

It was therefore an object of the invention to improve the tobacco smoke filters or filter elements, which are constructed in one piece and described above, so that the effectiveness of the bonded, finely divided absorbents is effected as little as possible, and, nevertheless, when a higher mass of the particulate additives are bonded, the resistance to the passage of air is low. Moreover, cellulose acetate, in particular, is to be used as filter material.

Pursuant to the invention, this objective is accomplished owing to the fact that that a) the additives are present on the surface of the fibers, the filaments or the films, b) the resistance of the tobacco smoke filter to the passage of air and the mass of the additives in the tobacco smoke filter observe the following equation (I): M_ad/ΔP>1 mg/daPA (I), in which ΔP is the resistance to the passage of air (daPA), which is used as a value calculated on the basis of a 7.8 mm filter diameter, M_ad(mg) is the mass of the additives, c) the tobacco smoke filter has a channel structure and d) the filter material is present as a two-dimensional formation.

Within the scope of the invention, the usual fibers, filaments and films, based on polymers or polymer mixtures, which can be spun or processed into films, may be used. Within the scope of the invention, the filter material preferably is a two-dimensional structure of fibers or filaments or a film, the two-dimensional structure and/or the film being smooth, folded, embossed and/or partially consolidated.

It is particularly preferred if the filter material is built up from a cellulose ester, cellulose acetate, cellulose butyrate, cellulose acetobutyrate, cellulose acetopropionate and/or cellulose propionate, in particular, coming into consideration as cellulose ester. A particularly preferred cellulose acetate has a degree of substitution of 1.5 to 3.0, especially of about 2.2 to 2.6 and, particularly of 2.5. Within the scope of the invention or of its realization, it has proven to be particularly advantageous to use a tobacco smoke filter, which is described in WO 01/28369. In a slight modification of the present invention and for the further optimization, it is preferred that the fiber weight (or filament weight resistance to the passage of air ratio S), related to the filament funnel, is larger than about 0.7, the S value being calculated from the formula

S=(m_A)/Δp_7.8/dpf(10 m/daPA)   (II),

in which m_A is the fiber weight (g) ΔP (sic!!) is the resistance to the passage of air (daPA) and dpf is the filament titer (dtex) and, for the resistance to the passage of air, the value, calculated for a filter diameter of 7.8 mm, is used, and the hardness of the cigarette filter exceeds approximately 90 filtrona hardness.

Moreover, it is regarded as preferred here that the fiber weight does not exceed 10 mg/mm of filter length and/or the residual crimping of the filter material does not exceed the value of 1.45, the following formula (III) applying here:

I_r=10,000×m_A/(G×I)   (III),

in which m_A is the fiber weight (g), G is the total titer (g/10 exp 4×m) and I is the filter length (mm).

The optimum residual crimping is between 1.05 and 1.4 and especially between 1.1 and 1.3. Moreover, preferably the fiber weight (or filament weight)/resistance to the passage of air ratio S, related to the filament titer, does not exceed a value of about 2 and, in particular, has a value between 0.8 and 1.3.

Particularly advantageous results are achieved with the inventive tobacco smoke filter if the fiber weight (or filament weight) is at least 4 mg/mm of filter length and especially between about 5 and 8 mg/mm of filter length.

With respect to optimizing the filtrona hardness, it may be noted that this should preferably be between about 90 and 95 and particularly between 91 and 93.

Within the scope of the invention, the additives, which are essential for accomplishing the objectives set, are disposed on the surface of the fibers, the filaments or the films. It is particularly preferred here if these additives are particulate and, in particular, have a particle size of less than 300 μm and especially of less than 100 μm. It is particularly preferred if the particle diameter is less than 50 μm, a particle size of 30 μm leading to particularly good results. The invention is not subject to any significant limitation in the selection of the particulate additives or porous additives. Someone of ordinary of skill in the art is capable of selecting suitable additives without any problems, these being present preferably in the form of an adsorbent based on activated charcoal, metal oxides, metal hydroxides and/or metal oxide hydrates, especially those of aluminum, silicon, titanium and/or magnesium. In individual cases, the porous additive preferably is treated additionally with active substances, especially in the form of antioxidants, flavors and/or anti-mutagenic substances.

The introduction of the particulate additives into the inventive tobacco smoke filter is not limited critically. Nevertheless, it is preferred if the particulate additives are fixed to the surface of the filter material by means of a binder, especially with polyvinyl acetate, polyvinyl alcohol, polyethylene glycol, water-soluble esters or ethers, starch, starch derivatives and/or cellulose esters.

The surface of the fibers, filaments and films may be optimized further, as follows. For example, the additive on the surface may fulfill the function of a filtration aid, especially in the form of organic acids, acidic carboxylic esters, of polyphenol and/or porphyrin derivatives. The fibers, filaments and films of the film material or the fibers, filaments and films, from which the tobacco smoke filters or filter elements are built up, may contain in their interior further additives, which improve their properties. Preferably, these are plasticizers, frosting agents, pigments and/or stabilizers. The inclusion of plasticizers is of particular importance. Preferably, these are present within the fibers or filaments or films in an amount of 0 to 15% by weight and especially of 5 to 12% by weight. Advisably, the plasticizer is present as triacetin, ethylene glycol diacetate and/or diethyl citrate. In addition, the inventive tobacco smoke filter may also contain a photoreactive additive, especially in the form of a finely divided titanium dioxide of the anatase type, having an average particle size of less than 2 μm.

A particular characteristic is given by the distinguishing feature b) of the above-defined inventive teachings. According to this, it is a requirement of the invention that the resistance to the flow of air of the tobacco smoke filter and the mass of the additive in the tobacco smoke filter adhere to the following formula M_ad/ΔP_7.8>1 mg/daPA (I), in which ΔP is the resistance to the passage of air (daPA), which is used as a value calculated on the basis of a 7.8 mm filter diameter, M_ad(mg) is the mass of the additives. In particular, it is preferred if the ratio of M_ad/ΔP is more than 2 mg/daPa and, in particular, more than 3 mg/daPa.

The channel structure of the claimed, one-piece tobacco smoke filter or filter elements is a further significant distinguishing feature of the invention. It should be pointed out that, for a channel structure, longitudinally aligned, channel-shaped regions of lower material density extend over an appreciable part of the filter or filter element. These channels are limited by the filter material of a higher material density. In particular, this channel structure is adhered to owing to the fact that a two-dimensional formation is used, pursuant to the invention, as filter material.

Someone of ordinary skill in the art can, without problems and without further additional technical information, produce the one-piece tobacco smoke filter or the one-piece tobacco smoke filter element. A particularly suitable method is dealt with in the following. Here, for the production of the inventive tobacco smoke filter tow is pulled from bales, prepared pneumatically according to methods customary for space filters. Before the actual activation step, a nonwoven fabric, with the highest possible strength in the direction of the two axes of the surface, is produced in an intermediate step, wound onto spools and acted upon with additives. Any method, suitable for producing tobacco smoke filters, can be used for distributing powder on a fiber surface. The devices are particularly suitable a) for applying the additives from a suspension in an aqueous liquid or a volatile, organic carrier or in a plasticizer liquid for the filaments, to which, in each case, a binder may be added and b) for blowing the additive, consisting of small particles, onto the filaments, which may previously be wetted with an adhesive or a plasticizer. Alternatively or in addition, the adhesion of the particulate additives can be ensured by a melt adhesive, which is applied either together with the particulate additives or separately or activated by heating briefly.

The inventive tobacco smoke filter can be produced continuously, starting from filter rods, and cut to a limited length. Each individual element of a length, limited in this way, could be used by itself as a tobacco smoke filter for a cigarette. However, preferably, it is used in a longitudinally aligned arrangement with at least one further filter element as part of an assembled (such as a double or triple) cigarette filter. Preferably, a single filter element of the present invention is used in combination with a longitudinally aligned mouthpiece element of the usual appearance, for example, a uniform rod of cellulose acetate fiber cable.

The advantages, which are associated with the present invention, can be summarized as follows. It has turned out that, by adhering to the inventive teachings, finely divided additives can be introduced into tobacco smoke filters, and, at the same time, contrary to the corresponding comparison product from the prior art, a particularly low resistance to the passage of air can be noted during smoking. It was found that a particularly high filtration performance can be achieved with the inventive filters.

Moreover, in comparison to the corresponding comparison products of the state of the art, the inventive one-piece tobacco smoke filter can be produced relatively easily. Moreover, the expensive production of the aforementioned chamber filter from several filter elements is omitted. It is a further advantage that, particularly when the filter material is constructed from cellulose acetate, the taste of the smoke is evaluated as particularly positive. A selective retention effect with respect to phenols is also observed.

The invention is described in greater detail below by means of examples.

EXAMPLE 1

Preparation of an Inventive Filter

A filter tow, having the specification 2,1Y48 (with a filament titer of 2.33 dtex and a total titer of 53,333 dtex) is prepared on a conventional, two-step KDF drafting device of the Hauni Company, Hamburg and sprayed with 8% triacetin. After leaving the guide roller, the filter tow web, with a minimum width of 250 mm is introduced into a pair of heated calender rollers and calendered with an effective line pressure of 40 kg/cm. The profiled calender rollers have a diameter of 230 cm and a grooved width of 355 mm and have 10 profiled grooves per cm, whereas the other roller is not profiled. They are heated to 150° C. with a silicone oil. The grilled profile is trapezoidal with an upper width of 0.4 mm and a depth of 0.5 miTL.

After leaving the calender rollers, the nonwoven, so prepared, is wound on a spool. Such a nonwoven spool is unwound at a conventional Foulard and passed through a bath, which is filled with an aqueous suspension of activated charcoal. In so doing, the nonwoven, directed downwards, is immersed up to 5 cm in the suspension and then deflected upward at a guide roller. On leaving the suspension bath, the excess suspension is squeezed off by a pair of squeeze rollers. The squeeze rollers are driven at a speed of 10 m/min and ensure uniform movement of the nonwoven through the suspension. After leaving the squeeze rollers, the nonwoven is passed through a recirculating air dryer at a temperature of 150° C. The dryer has a drying segment of 4 meters and, with that, ensures the drying of the suspension and the fixing of the activated charcoal on the nonwoven.

Upon leaving the dryer, the nonwoven, doped with activated charcoal, is folded into strands in a conventional commercial KDF 2 of the Korber Company, Hamburg, by being introduced into an inlet nozzle, enveloped with paper and cut to a filter length of 126 mm. The diameter of the filter rods was adjusted to 7.8 mm.

COMPARISON EXAMPLE 1

Preparation of an Activated charcoal Filter by Scattering Carbon Particles into a Filter Tow

A filter tow, having the specification 2,1Y48 (with a filament titer of 2.33 dtex and a total titer of 53,333 dtex) is prepared on a conventional KDF 2 drafting device of the Hauni Company, Hamburg and sprayed with triacetin. Upon leaving the guide roller, the filter tow web with a minimum width of 200 mm is guided through a spreader nozzle and treated pneumatically with activated charcoal particles having a particle size of approximately 250 μm. For this purpose, the activated charcoal powder is dosed continuously with a dosing balance onto an intake connecting piece and blown with compressed air through a pipeline to the spreader nozzle. Advantageously, the spreader nozzle is enclosed in a box with suction, which has openings only for the intake and discharge of the filter tow web, in order to avoid any escape of carbon dust into the surroundings. By matching the amount of activated charcoal supplied to the speed of the filter tow web, the amount of activated charcoal on the filter tow web can be adjusted very accurately. Upon leaving the device described, the filter tow web is folded into strands in an inlet nozzle and enveloped with paper in a conventional commercial KDF 2 of the Korber Company, Hamburg, at a strand speed of 50 m/min and cut to a filter length of 126 mm. The filter rod diameter was adjusted to 7.8 mm.

The results of measuring the resistance to airflow and the mass of the activated charcoal are summarized in the Table.

				Activated
	Particle Size			Charcoal mass	Resistance to
	Activated			(mg per 21 mm	flow of air
	Charcoal	Dpf	Total	of filter	(filter plug)	Mad/ΔP
	(μm)	(dtex)	(dtex)	plug	(daPA)	(mg/daPA)
Comparison	250	2.33	53	80	131	0.61
Example 1			333
Example	20	2.33	53	80	10	8.0
			333

Claims

1. Tobacco smoke filters or filter elements, which are constructed in one piece and contain fibrous filaments or films based on polymers or polymer mixtures, which can be spun or processed into films and contain one or more additives, wherein

a) the additives are present at the surface of the fibers, the filaments or the films,

b) the resistance of the tobacco smoke filter to the passage of air and the mass of the additives in the tobacco smoke filter observe the following equation (I): Mad/ΔP>1 mg/daPA   (I),

in which ΔP7.8 is the resistance to the passage of air (daPA), which is used as a value calculated on the basis of a 7.8 mm filter diameter, Mad(mg) is the mass of the additives, and

c) the tobacco smoke filter has a channel structure and d) the filter material is present as a two-dimensional formation.

2. The tobacco smoke filter of according to claim 1, wherein the filter material is a two-dimensional formation of fibers or filaments or folded film, the two-dimensional formation and/or the film being smooth, folded, embossed and/or partially consolidated.

3. The tobacco smoke filter according to claims 1, wherein the filter material is built up from a cellulose ester.

4. The tobacco smoke filter according to claim 3, wherein the cellulose ester is cellulose acetate, cellulose butyrate, cellulose acetobutyrate, cellulose acetopropionate and/or cellulose propionate.

5. The tobacco smoke filter according to claim 4, wherein the cellulose acetate has a degree of substitution of approximately 1.5 and 3.0 and especially of 2.2 to 2.6.

6. The tobacco smoke filter according to claim 1, wherein the ratio of Mad/ΔP is more than 2 mg/daPa and especially more than 3 mg/daPa.

7. The tobacco smoke filter according to claims 1, wherein the additives, on the surface of the fibers, filaments or films are particulate, and, in particular, have a particle size of less than 300 μm.

8. The tobacco smoke filter according to claim 7, wherein the particle size of the additives is less than 100 μm and especially less than 50 μm and particularly less than 30 μm.

9. The tobacco smoke filter according to claims 7, wherein the particulate additives are porous additives, especially in the form of an absorbent based on activated charcoal, metal oxides, metal hydroxides and/or metal oxide hydrates.

10. The tobacco smoke filter according to claim 9, wherein the metal oxides, hydroxides and/or metal oxide hydrates are those of aluminum, silicon, titanium and/or magnesium.

11. The tobacco smoke filter according to claims 9, wherein the porous additive is treated with active substances, especially in the form of antioxidants, flavors and/or antimutagenic substances.

12. The tobacco smoke filter according to claims 1, wherein the additive, on the surface of the fibers, filaments and films, is a filtration aid, especially in the form of organic acids, acidic carboxylic esters of polyphenol and/or porphyrin derivatives.

13. The tobacco smoke filter according to claims 1, wherein the particulate additives are fixed on the surface of the filter material by means of a binder, especially with polyvinyl acetate, polyvinyl alcohol, polyethylene glycol, water soluble esters or ethers, starch, starch derivatives and/or cellulose esters, especially cellulose acetate with an average degree of acetylation of 0.3 to 1.

14. The tobacco smoke filter according to claims 1, wherein the fibers, filaments or films of the film material contain further additives in their interior to improve the properties.

15. The tobacco smoke filter according to claim 14, wherein the further additives are plasticizers, marking agents, pigments and/or stabilizers.

16. The tobacco smoke filter according to claim 15, wherein the plasticizer within the fibers or filaments or films is present in an amount of 5 to 15% by weight.

17. The tobacco smoke filter of according to claims 15, wherein the plasticizer is present in the form of triacetin, ethylene glycol diacetate and/or diethyl citrate.

18. The tobacco smoke filter according to claim 1, wherein the fiber weight (or filament weight/resistance to the passage of air ratio S, related to the filament funnel, is larger than about 0.7, the S value being calculated from the formula in which mA is the fiber weight (g), ΔP (daPA) is the resistance to the passage of air and dpf is the titer of the filament (dtex) and, for the resistance to the passage of air, the value, calculated for a filter diameter of 7.8 mm, is used, and the hardness of the cigarette filter exceeds approximately 90 filtrona hardness.

S=(mA/ΔP7.8)/dpf [10 m/daPA]  (II)

19. The tobacco smoke filter according to claim 18, wherein the fiber weight does not exceed 10 mg/mm of filter length and/or the residual crimping of the filter material does not exceed the value of 1.45, Formula (III) applying here:

Ir=10,000×mA/(G×I) (III), in which mA is the fiber weight (g), G is the total titer (g/10 exp 4×m) and I is the filter length (mm).

20. The tobacco smoke filter according to claim 19, wherein the residual crimping is between 1.05 and 1.4 and especially between 1.1 and 1.3.

21. The tobacco smoke filter of according to claims 18, wherein the fiber weight (or filament weight)/resistance to the passage of air ratio S, related to the filament titer, does not exceed a value of about 2 and, in particular, has a value between 0.8 and 1.3.

22. The tobacco smoke filter according to claim 18, wherein the fiber weight (or filament weight) is at least 4 mg/mm of filter length and especially between 5 and 8 mg/mm of filter length.

23. The tobacco smoke filter according to claim 18, wherein the filtrona hardness is between about 90 and 95 and particularly between 91 and 93.

24. The tobacco smoke filter according to claim 1, wherein the filter contains a photoreactive additive, especially in the form of finely divided titanium oxide of the anatase type having an average particle size of less than 2 μm.