Disintegratable cigarette filter

Details Disintegratable cigarette filter Disintegratable cigarette filter

2002-04-17

2004-08-17

Griffin, Steven P. (Department: 1731)

Tobacco

Smoke separator or treater

Including a cellulose ester or ether

C131S343000

Reexamination Certificate

active

06776168

ABSTRACT:

The invention concerns a high-performance cigarette filter with mechanical disintegrability and based on cellulose ester fibres or filaments.
The majority of cigarette filters used currently is produced from filter tow, comprising endless, crimped in a crush chamber, cellulose-2,5-acetate filaments. For the production of the filter tow a solution of approx. 30% cellulose-2,5-acetate in acetone is pressed through spinning jets, the acetone is evaporated in a spinning shaft by blowing in heated air, a plurality of filaments (3.000 to 35.000) is combined into a band and subsequently this is crimped in a crush chamber. Afterwards the product is dried, filled into storage containers and finally compressed into bales having a weight of 300-600 kg. The total quantity of filter tow produced currently in the world according to this method is approx. 500.000 t/year, underlining the economic significance of the process. After transporting the filter tow bales to the filter manufacturer or cigarette manufacturer, the filter tow is removed from the bales and processed on a filter rod machine into filter rods, as it is described, for example, in U.S. Pat. No. 5,460,590. At the same time the filter is stretched in a stretching device, provided with an additive to bond the filaments and then, after forming a three-dimensional slub, is introduced into the forming part with the aid of a feed funnel, it is compressed there transversely to the axis, wrapped with paper and cut to the final length of the filter plug.
The additive used to bond the filaments is, as a rule, a solvent for the cellulose acetate with a high boiling temperature, like, for example, glycerol triacetate (triacetin), that, after its application, temporarily dissolves the surface of the filaments. Everywhere, where two filaments accidentally contact one another, after a while a firm adhesive position occurs, since the excess additive migrates into the surface of the fibres, due to which the previously liquid solvent drops, from the cellulose-2,5-acetate in the additive, solidifies. After a period of storage of less than one hour, depending on the previously mentioned migration of the hardening agent, mechanically firm, three-dimensionally interlaced filter plugs are obtained (called “space filter” in the following) with low packing density (nowadays usually 80-120 mg/cm
3
), which due to their hardness can be processed at high speeds in modern cigarette machines.
The advantages of the entire process are the high efficiency of the filter tow production, the low transport costs from the filter tow manufacturer to the end users and, in particular, the high productivity of the filter production, which is determined not insignificantly by the lengths of the bands in the bales. The processing of filter tows is carried out on commercially available filter plug machines, like, for example, the KDF 3/AF 3 by Körber A G, Hamburg. In this conjunction production speeds of 600 m/min are the state-of-the-art. When using the double-strand technology described in DE-A-43 40 029 and when using the twin tow technology illustrated in DE-A-43 20 303, the productivity of the filter production can be even more markedly increased. A further advantage of the conventional filter production is based on the fact that by changing the speed ratios between the preparation and the formatting portions the filter properties regarding the reduction of pressure and consequently the filtration capacity can be varied within wide limits while retaining the specifications of the filter tow. Moreover, by varying the titre of the filament and the total titre an almost arbitrary amount of filters with different filtering capacities can be produced using the described method.
For the production of space filters nowadays mostly cellulose-2,5-acetate is used. With regard to the argument about smoking and health it has demonstrable underlining properties regarding the specific retention phenomena. Thus a filter from cellulose acetate filters nitrous amines and phenols having hazardous for health properties considerably more efficiently than condensate and nicotine. In addition, the taste of the smoke of the tobacco mixture used nowadays, as for example “American blend”, “German blend” and “Virginia”, in combination with a space filter from cellulose acetate is judged by the smoking person as the most pleasant one. Another advantage, not to be underestimated, of a space filter from cellulose-2,5-acetate is the visual homogeneity of the cut surfaces of the filter.
All other possible polymers, with which space filters can be produced by comparable methods, could not penetrate the market due to negatively affecting the taste of the smoke, lack of specific retention, problems with hardening and problems with cutting the filter on the filter rod machine, as well as on the cigarette machine. The very negative assessment of the smoking taste and the lack of specific retentions when using other polymers for the manufacture of space filters suggests that the advantages of today's acetate filters are not casually linked with the physical construction of the filter, but can be traced back to the adsorbing properties of the cellulose-2,5-acetate polymer, which should have positive effect in the case of surface filters also. However, despite their undisputable market domination, space filters from cellulose-2,5 acetate have some serious disadvantages: the draw resistance and filtration capacity are unambiguously defined based on the constructive physical specifications. The particle filtration as well as the condensate retention “R
k
” of a conventional space filter is a function of filament titre (fibre density), filter diameter, draw resistance and length of filter. The following applies:
R
k
=f(dpf, D, l, &Dgr;P)  (1)
where—dpf=filament titre [dtex]
D=diameter of filter [mm]
l=length of filter [mm], and
&Dgr;P=draw resistance [daPA]
There was no shortage of experiments to illustrate the relationship between these values by empirically established equations. Examples of these can be found in the following publications: “Design of cigarettes”, C. L. Brown, Hoechst-Celanese Corporation, 3
rd
edition, 1990 and Cable©: Capability Line Expert Copyright© 1994 by Rhodia Acetow A G, 79123 Freiburg, Germany.
In the currently used filter calculating program “Cable©” the following empirically determined relationship is used:
R
k
=100·(1
−D
k
)  (2)
 where—
D
k
=exp(
L·A+B
)  (3)
A=K
1
-
K
2
·
dpf
  (4)
L
=21
−l
  (5), and
B
=−(
K
3
·
D
4
·&Dgr;P+K
4
/
dpf+K
5
)  (6).
K
1
to K
5
are constants, which have been determined in accordance with the tobacco mixture and the respective method to determine the retention. In other words: for a given filter length and a fixed diameter the filtration capacity of a cigarette filter is unambiguously determined by the draw resistance of the filter and the filament titre of the filter tow specification used.
There was no shortage of experiments to increase the filtration capacity of space filters while retaining specifications like length, diameter, draw resistance and filament titre. Such a high-performance filter is described, for example, in DE-A-26 58 479, wherein the increase of the filtration capacity is achieved by adding retention-increasing, finely dispersed metal oxides. The draw resistance &Dgr;P of a space filter is also clearly defined. It depends from the diameter D of the filter, its length l, the filament titre dpf, the total titre G [g/10exp4·m] as well as the weight of the fibre m
A
[g]
&Dgr;P=f(D, l, dpf, G, m
A
)  (7).
When using a defined filter tow specification, the fibre weight is unambiguously determined for a given filter plug having a draw resistance &Dgr;P, a diameter D and a length l. The relationship between the fibre weight and draw resistance cannot be illustrated by a mathematica

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