FILTER ELEMENT FOR MOUTHPIECES FOR USE WITH SMOKING PRODUCTS OR HNB PRODUCTS

Abstract

The invention relates to a filter element for mouthpieces for use in smoking products or HNB products. The filter material has a filter main part from a tow material, the tow material being formed by a plurality of individual threads from cross-linked and crimped cellulose acetate filaments. The cellulose acetate filaments have a particularly polygonal and preferably Y-shaped cross-sectional geometry, and the tow material has a mass specific surface area of less than 0.15 m.sup.2/g, more particularly less than 0.3 m.sup.2/g, and more than 0.025 m.sup.2/g.

Claims

1. A filter element for mouthpieces for use with smoking products or HNB products, wherein the filter element has a filter body made from a tow material, whereby the tow material is formed by a plurality of individual filaments of cross-linked and crimped cellulose acetate filaments, whereby the cellulose acetate filaments in particular exhibit a polygonal and preferably Y-shaped cross-sectional geometry, and whereby the tow material has a mass-related specific surface area of less than 0.15 m.sup.2/g and more than 0.025 m.sup.2/g, and wherein the tow material of the filter body exhibits a residual crimp (RS) and a density (), whereby a residual crimp-related density value A amounts to at least 0.016 mg.sup.2mm.sup.6, with: $A={}^2*\mathrm{RS}.$

2. The filter element according to claim 1, wherein the residual crimp (RS) of the tow material of the filter body does not exceed the value of 1.7, whereby the residual crimp (RS) of the tow material of the filter body is preferably between approximately 1.1 and approximately 1.7 and in particular between 1.3 and 1.7.

3. The filter element according to claim 1, wherein the filter body exhibits a fiber weight, whereby the fiber weight of the filter body amounts to a maximum 10 mg/mm filter length.

4. The filter element according to claim 1, wherein the cellulose acetate filaments of the tow material exhibit an in particular predefined or definable uniform filament titer, particularly a predefined or definable uniform filament titer within a range of between 8 denier (8.88 dtex) and 30 denier (33.33 dtex), and preferably between 9 denier (10 dtex) and 30 denier (33.33 dtex), and more preferentially between 10 denier (11.11 dtex) and 20 denier (22.22 dtex).

5. The filter element according to claim 4, wherein a coefficient of variation of the uniform filament titer is at most 0.1 and preferably 0.05 maximum to 0.01 maximum.

6. The filter element according to claim 1, wherein the individual filaments of the tow material formed from the cellulose acetate filaments exhibit an in particular predefined or definable and preferably uniform filament titer of at least 200 denier (222 dtex) and at most 4000 denier (4.444 dtex) and preferably at least 250 denier (277 dtex) and at most 2500 denier (2.777 dtex).

7. The filter element according to claim 6, wherein a coefficient of variation of the uniform filament titer is at most 0.1 and preferably 0.05 maximum to 0.01 maximum.

8. The filter element according to claim 1, wherein the filter body is in particular realized as a filter rod and preferably with a diameter of between approximately 8 mm and approximately 5 mm and particularly a diameter of approximately 7.8 mm or approximately 5.35 mm, whereby at least part of the filter body is wrapped in a paper or paper-like material.

9. The filter element according to claim 8, wherein the filter body with the wrapping composed of paper or paper-like material has a compression depth of less than 0.90 mm and in particular less than 0.85 mm when a cylindrical test piece having a mass of 300 g and a diameter of 12 mm is placed at the front end of the filter body perpendicular to the filter body axis.

10. The filter element according to claim 8, wherein the filter body without the wrapping composed of paper or paper-like material has a compression depth of less than 0.90 mm and in particular less than 0.85 mm when a cylindrical test piece having a mass of 300 g and a diameter of 12 mm is placed at the front end of the filter body perpendicular to the filter body axis.

11. The filter element according to claim 1, wherein the cellulose acetate filaments of the individual filaments of the tow material are at least partially formed as hollow and/or tubular cellulose acetate filaments.

12. The filter element according to claim 1, wherein the hardness of the filter body is at least 80% Filtrona hardness and preferably at least 90% Filtrona hardness.

13. The filter element according to claim 1, wherein the filter body has a plasticizer exhibiting a plasticizer content between approximately 2% and approximately 15% and preferably between approximately 4% and 10%, whereby the plasticizer in particular contains triacetin, triethylene glycol diacetate and/or citric acid diethyl ester.

14. The filter element according to claim 1, wherein the tow material exhibits a total titer of between 4000 denier (4.444 dtex) and 40000 denier (44.444 dtex) and preferably between 6000 denier (6.667 dtex) and 30000 denier (33.333 dtex).

Description

[0025] According to embodiments of the inventive filter element, the cellulose acetate filaments of the tow material's individual filaments are at least partially formed as hollow and/or tubular cellulose acetate filaments.

[0026] Particularly to be understood by hollow/tubular cellulose acetate filaments are preferably cylindrical filaments exhibiting one or more continuous cavities when viewed in cross section.

[0027] Such hollow fibers can be at least partly designed as multi-lumen hollow fibers. Compared to solid cellulose acetate filaments, single-lumen or multi-lumen tubular cellulose acetate filaments are considerably more resistant to kinking, whereby particularly high Filtrona hardness can be realized without increased material compression.

[0028] According to embodiments of the present invention, the hollow cellulose acetate filaments exhibit an at least partially trilobal; i.e. three-armed star-shaped, cross-sectional shape. Such a cross-sectional shape is well-suited when the cellulose acetate filaments are to have the largest possible specific surface area so as to enable high filtration capability along with simultaneous economical use of raw materials, for example.

[0029] Alternatively thereto, it is possible to obtain the desired large specific surface area using a bundle of extremely fine filaments of circular cross-section. However, other cross-sectional shapes for the hollow cellulose acetate filaments are also conceivable such as, for example, a four-sided cross-sectional shape.

[0030] Because the inventive filter element comprises a filter body able to be based at least in part on cellulose acetate filaments which are at least partially formed as hollow cellulose acetate filaments, a low draw resistance and low filtration performance can be realized since the filaments of the filter element at least partially formed as hollow cellulose acetate filaments have a small external surface area in relation to the total fiber volume.

[0031] In this context, it was surprisingly found that due to the filaments being partially formed as hollow cellulose acetate filaments, particularly high Filtrona hardnesses can be realized with the filter element.

[0032] In fact, it became evident that filter elements which are at least partially formed from hollow cellulose acetate filaments (hollow fibers) achieve the desired minimum Filtrona hardness with a lower fiber weight per unit of volume.

[0033] Since the inventive filter element is based on cellulose acetate filaments, the inventive filter element is designed to form a uniform, white and smooth mouth-side front end for a tobacco rod of for example a cigarette, whereby a selective phenol filtration effect can further be realized.

[0034] The use of a filter element based on cellulose acetate filaments for one thing enables producing filter rods particularly for cigarettes which, from the smoking and health standpoint, have shown demonstrably outstanding properties relative to specific retention phenomena.

[0035] A filter made from cellulose acetate thus filters harmful nitrosamines and phenols far more efficiently than condensate and nicotine. In addition, smokers rate the taste of today's customary tobacco blend such as e.g. American Blend, German Blend and Virginia combined with a filter rod made of cellulose acetate to be the most palatable. A further advantage of a cellulose acetate filter rod not to be underestimated can be found in the optical homogeneity of the filter's cut surfaces.

[0036] By the inventive filter element being at least partially formed from hollow cellulose acetate filaments serving as filler material according to embodiments, there can be a wide range of varying draw resistance and filtration performance in filter rods made from the inventive material.

[0037] It has in particular been shown that a filter material consisting at least partially of hollow cellulose acetate filaments exhibits an improved thermal cooling effect. It was determined that the use of hollow cellulose acetate filaments as filler material was still able to achieve a very low filtering effect; i.e. retention effect, for the suspended substances and gases to be removed.

[0038] It is presumed that this effect is achieved due to the surface or the flow of gas or air to be cleaned being changed by the hollow cellulose acetate filaments in such a way as to only marginally retain any potentially suspended matter in the gas/air. Another reason could be that the use of hollow cellulose acetate filaments is able to achieve a different, particularly advantageous filter material surface structure.

[0039] The inventive filter element further has the advantage of enabling in particular variable cooling of a heated particle-laden gas (particularly aerosol) such that the temperature of the gas, aerosol or vapor taken in by the user of a smoking product or HNB product can be selectively reduced. By varying the proportion of hollow cellulose acetate filaments in the filter and/or filler material, the desired cooling effect can thus be adapted specifically to the application.

[0040] Further important to note is that the flow in the inventive filter element is essentially around and less through the hollow cellulose acetate filaments (=hollow fibers). From geometrical considerations, it is obvious that the fiber-to-fiber distances are thereby considerably larger than the lumen (hollow portion) of the hollow fiber. The viscosity of the aerosol (substantially air) then occasions the path of least resistance to be taken (i.e. flow between the filaments and not through each individual filament).

[0041] In other words, the operative filtration surface is by no means maximized in the embodiment of the inventive filter element since there is no flow through the hollow cellulose acetate filaments in the tow material.

[0042] In particular, the hollow cellulose acetate filaments can thus have kinks that close off the lumen of the hollow cellulose acetate filaments without this having an effect on the performance of the inventive filter and/or filler material as regards the set target parameters.

[0043] Particularly to be noted in this context is that the hollow cellulose acetate filaments realized as hollow fibers do not need to be continuously hollow but rather can also be partially closed off by kinks. They can also deviate from an ideal circular shape.

[0044] Embodiments of the invention provide for the hollow cellulose acetate filaments of the tow material to serve on the one hand as a support material and on the other hand as cooling material. By the hollow cellulose acetate filaments simultaneously serving as a support material, particularly compact filter elements can be realized which do not thereby necessitate increasing the dimensions of the smoking product.

[0045] The term Filtrona hardness as used herein refers to the filter hardness as determined according to the Filtrona principle. Under this principle, the filter hardness is determined by vertically pressing the flat front end of a cylindrical rod 12 mm in diameter onto a horizontally positioned filter rod at a load of 300 g. The ratio of the compressed diameter to the initial diameter previously determined at first contact yields the Filtrona hardness percentage.

[0046] The filter element or filter rod hardness respectively is an important target criterion particularly for cigarette filters. It is typically indicated as the so-called Filtrona hardness. To hereby be noted is that Filtrona hardness is only measured on a filter element but not, however, on the underlying (raw) filter material; i.e. tow material. The Filtrona hardness of a filter element is particularly influenced by the amount of triacetin which is/can be sprayed onto the filter element.

[0047] The minimum limit of Filtrona hardness is approximately 88% and is geared toward market requirements. The Filtrona hardness of the filter element can thereby preferably be set to approximately 88% to 95%, in particular approximately 90% to 93%.

[0048] Preferential embodiments of the inventive filter element provide for the filter body to be realized in particular as a filter rod and preferably with a diameter of between approximately 8 mm and approximately 5 mm, and particularly a diameter of approximately 7.8 mm or approximately 5.35 mm, wherein at least part of the filter body is wrapped in a paper or paper-like material.

[0049] The Filtrona hardness of the filter element should preferably be greater than 85% in this embodiment and, in particular, greater than 90%.

[0050] Filtrona hardness is particularly dictated by the fiber weight per volume for a given filter diameter, whereby the filament titer of the tow material's cellulose acetate filaments only has a minor influence on the Filtrona hardness.

[0051] Configurations of the inventive filter element provide for the filter body to have a fiber weight amounting to a maximum 10 mg/mm filter element length.

[0052] The Filtrona hardness of the filter element can also be achieved by means of a stronger filter wrap paper or stronger tipping paper.

[0053] Tipping paper is a paper in which either multiple filter elements are coupled together or a filter element is connected to a tobacco rod. However, increasing the Filtrona hardness of the filter element by using stronger filter wrap paper or stronger tipping paper has economic disadvantages since higher costs can be expected with this approach.

[0054] Associated with the Filtrona hardness of the filter element is the so-called hot collapse, in which the filter hardness decreases as the filter element is being used; i.e. the filter element being used with smoking or HNB products. This phenomenon can particularly occur with a traditional cigarette when the filter element is heated in the presence of moisture during one of the last puffs, although this undesirable effect can also occur with HNB products.

[0055] It has been shown in this context that the degree to which the Filtrona hardness decreases due to the hot collapse phenomenon can be significantly reduced when a tow material having the cited mass-related specific surface area of less than 0.15 m.sup.2/g is used as the base material of the inventive filter element.

[0056] By the tow material of the filter body of the inventive filter element having a mass-related specific surface area ranging between 0.3 m.sup.2/g and 0.025 m.sup.2/g, and in particular being less than 0.15 m.sup.2/g, the draw resistance and the filtration performance of the inventive filter element can be reduced without the length of the filter element being reduced. Relatively long filter elements enabling a correspondingly long cooling section can thus be realized, which is advantageous relative to the heat balance, particularly when the filter element is used with HNB products.

[0057] Additionally thereto, the inventive specification of the mass-related specific surface area of the tow material at a value particularly less than 0.15 m.sup.2/g enables the draw resistance and the filtration performance of the filter element to be reduced without reducing the fiber weight in the filter element per volume fraction and/or without reducing the total titer of the tow material. This has the advantage of there being no decrease in the filter element's Filtrona hardness due to a reduction of the fiber weight in the filter element per volume fraction and/or due to a reduction of the total titer.

[0058] According to embodiments of the inventive filter element, the filter body has a fiber weight of maximum 10 mg/mm filter element length. The tow material, which constitutes the base product for the production of the inventive filter element, should in particular exhibit a total titer of 10,000 denier to 40,000 denier.

[0059] The cellulose acetate filaments of the tow material serving as the base product for producing the inventive filter element are in particular cellulose-2,5-acetate, cellulose butyrate, cellulose acetate butyrate, cellulose acetate propionate and/or cellulose propionate filaments. The cellulose acetate filaments preferably have a degree of substitution of approximately 1.5 to 3.0, preferably approx. 2.2 to 2.6.

[0060] The plasticizers preferably used for the plasticizing and in particular thermo-plasticizing of the cellulose acetate fibers and applied to the fibers can for example be selected from among the following groups: glycerol ester (particularly glycerol triacetate), ethylene and propylene carbonate, citric acid ester (particularly acetyl citrate, triethyl citrate), glycose ester or diethylene glycol dibenzoate.

[0061] The person skilled in the art of this technical field is familiar with the amount of plasticizing agent and/or water-soluble bonding agent to be used. In general, there is a plasticizer and/or bonding agent content of about 1 to 14% by weight; in special cases, however, the plasticizer content can easily exceed this range.

[0062] Water-soluble bonding agents, as preferentially present on the surface of the cellulose acetate filaments, can in particular be high-boiling solvents applied to the individual filaments of the tow material or to the tow material such as polyalkylene oxides, water-soluble ester or ether, starches, starch derivatives, p-polyvinyl alcohols, polyvinyl ethers, p-polyvinyl acetates and/or polysaccharides, water soluble polyamides and polyacrylates.

[0063] Particularly recognized in the present case was that also the residual crimp (RS) of the tow material of the filter body and the density () of the filter body have a significant impact on the performance of the filter element. A residual crimp-related density value A is thereby preferably at least 0.016 mg.sup.2mm.sup.6 with:

[00001]$A={}^2*\mathrm{RS}.$

[0064] The residual crimp (RS) of the filter body's tow material in particular should thereby not exceed the value of 1.7, and particularly the value of 1.45, whereby the residual crimp (RS) of the tow material is preferably between approximately 1.05 and approximately 1.4 and in particular between 1.1 and 1.3.

[0065] The residual crimp is thereby understood as the ratio of the length of the final crimped cellulose acetate filament to the length of the filter element. Residual crimp is a characteristic property for a given filter element.

[0066] A further aspect of the present invention relates to specifying a tow material for producing a filter element for mouthpieces used with smoking products or HNB products, wherein the tow material is optimized to the effect of the filter elements produced from the tow material exhibiting the most consistent possible performance particularly in terms of filtration performance and filter hardness.

[0067] In this context, also thereby determined to be particularly important is the cellulose acetate filaments of the tow material in particular having an predefined or definable uniform filament titer. This predefined or definable uniform filament titer is particularly within a range of between 8 and 30 denier, preferably in a range between 9 and 30 denier, and more preferentially between 10 and 20 denier.

[0068] In order to achieve consistent performance of the filter element made from the tow material, particularly with respect to filtration performance and filter hardness, a coefficient of variation of the uniform filament titer should be at most 0.1 and preferably 0.05 maximum to 0.01 maximum.

[0069] The coefficient of variation of the uniform filament titer, which can also be called the deviation coefficient, is a statistical parameter and characterizesin contrast to variancea relative measure of dispersion; i.e. is not dependent on the measurement unit of the statistical variable or random variables.

[0070] In other words, it is ensured during the production of the tow material that the individual filaments produced by the respectively used spinnerets of the spinning frame exhibit a uniform filament titer.

[0071] This can thereby be realized in practice by each spinneret being allotted its own in particular frequency-controlled spin pump in order to ensure that each spinneret of the spinning frame is supplied with the spin fluid (solution of approximately 30% cellulose-2,5-acetate in acetone) in such a way as to enable realizing a uniform nozzle pressure and a uniform amount of spin fluid delivered from each spinneret per unit of time.

[0072] This easily realizable yet nevertheless effective approach enables realizing an in particular predefined or definable uniform filament titer.

[0073] Alternatively or additionally thereto, it is preferential for the individual filaments of the tow material formed from the cellulose acetate filaments to exhibit a predefined or definable and preferably uniform filament titer of at least 200 denier and at most 4000 denier, and preferably at least 250 denier and at most 2500 denier, wherein a coefficient of variation of the uniform filament titer here is preferably at most 0.1 and in particular 0.05 maximum to 0.01 maximum.