U.S. patent number 3,648,712 [Application Number 05/006,867] was granted by the patent office on 1972-03-14 for cigarette filter construction.
This patent grant is currently assigned to Celanese Corporation. Invention is credited to Carl Dean Patterson.
United States Patent |
3,648,712 |
Patterson |
March 14, 1972 |
CIGARETTE FILTER CONSTRUCTION
Abstract
A filter is described which is comprised of a high gas
permeability plug in combination with a low gas permeability
disc.
Inventors: |
Patterson; Carl Dean (Kessler
Air Force Base, MS) |
Assignee: |
Celanese Corporation (New York,
NY)
|
Family
ID: |
21723009 |
Appl.
No.: |
05/006,867 |
Filed: |
January 29, 1970 |
Current U.S.
Class: |
131/339 |
Current CPC
Class: |
A24D
3/045 (20130101) |
Current International
Class: |
A24D
3/00 (20060101); A24D 3/04 (20060101); A24d
001/04 () |
Field of
Search: |
;131/9,10,10.1-10.9,261-269 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rein; Melvin D.
Claims
What is claimed is:
1. A cigarette filter comprising a wrapped high gas permeability
plug of substantially longitudinally aligned, crimped, continuous
cellulose acetate filaments having a total denier of approximately
20,000-40,000 with the individual filaments having a denier of from
2 to 30, said plug being in contact with a low gas permeability
disc formed of a highly compacted stereo-reticulate mass of fibers,
said disc manifesting a pressure drop of approximately 20-40 mm. of
H.sub.2 O, the disc having a diameter which is 5-25 percent less
than that of the plug and so oriented within the wrapper as to
provide an unobstructed annular smoke path therearound.
2. The cigarette filter of claim 1 in which the fibers of the
stereo-reticulate mass are selected from the group consisting of
cellulosic, glass and polyolefin fibers -- The "Abstract of the
Disclosure" has been changed to read:
A cigarette filter is disclosed which is composed of two major
elements, that is, a plug of longitudinally arranged crimped and
continuous cellulose acetate filaments of 20,000-40,000 denier and
secondly a compacted fiber disc which either abuts one end of the
plug or is disposed within the body thereof. The disc is composed
of a stereo-reticulate compacted mass of natural or synthetic
fibers such as cellulose, glass or polyolefin fibers and manifests
a pressure drop of preferably between 20-40 mm. of H.sub.2 O. The
disc is of a diameter which is 5 to 25 percent less than the
diameter of the plug and so oriented as to provide an unobstructed
annular smoke passage therearound.
Description
BACKGROUND OF THE INVENTION
There has been much interest in the past, particularly as evidenced
by the patent literature, in the development of tobacco smoke
filters, particularly cigarette filters. Most of the filters
described have been effective to some extent, but only a few of the
many filters suggested have met with any degree of commercial
acceptance.
To be suitable commercially, a tobacco smoke filter must remove a
significant amount of particulate matter, i.e., "tar", while
exhibiting a draw resistance that is acceptable to the smoker. In
other words, the filter must show an acceptable level of smoke
removal efficiency at an acceptable pressure drop.
Generally, the filter which has the highest smoke removal
efficiency at a given pressure drop is considered to be the best
filter. To be commercially acceptable, the filter must also be
economically producible. Further, the balance of the smoke stream
must not be unduly distorted by the filter.
Because of these factors, only filters of crimped, continuous
filament cellulose acetate tow and filters of corrugated paper webs
have met with any large commercial acceptance. A minor percentage
of these filters contain charcoal to filter the gaseous phase.
Other filters, e.g., filters containing other filtration materials
and/or baffle arrangements, have experienced little or no success
due to economics or a failure to show a smoke removal efficiency to
pressure drop ratio superior to conventional cellulose acetate or
paper filters.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
tobacco smoke filter, and particularly a cigarette filter, which
will have a high smoke removal efficiency at a commercially
acceptable pressure drop.
It is another object to provide a filter which will be economically
producible and which will not unduly distort the smoke stream.
Other objects of the present invention, if not specifically set
forth herein, will be apparent to one skilled in the art upon
reading the following detailed description of the invention.
DRAWINGS
FIG. 1 is a side view of a tobacco column and filter exemplary of
the filters herein described.
FIGS. 2, 3 and 4 are illustrative of suitable discs.
DETAILED DESCRIPTION OF THE INVENTION
Generally, the filter of the present invention is composed of at
least one plug of a conventional filtration material, preferably a
high gas permeability plug consisting of a number of crimped,
continuous cellulose acetate filaments, in combination with a disc
having a low gas permeability. Ordinarily, the filter will be
covered with a conventional paper wrapper.
Preferably, the disc employed in the present filter is composed of
a highly compacted stereo reticulate mass of natural or synthetic
fibers, desirably cellulose, glass or polyolefin fibers, e.g.,
polypropylene or polyethylene fibers. Discs of non-porous material,
e.g., Celluloid, polyolefin, nylon, polyester, etc., may also be
used, if the discs are perforated sufficiently, or are of the
proper size, to give an acceptable pressure drop. For reasons which
will become apparent, however, fibrous discs are preferred.
Regardless of its compositions, the disc, to be acceptable in the
present invention, must exhibit an acceptable pressure drop.
Generally, this pressure drop must be equivalent to from about 15
mm. to about 60 mm. of H.sub.2 O, and preferably, from about 20 to
40 mm. of H.sub.2 O.
While a disc having a diameter up to equal that of the tobacco
column may be employed, it has been found, surprisingly, that the
highest smoke removal efficiency at a given pressure drop is
obtained when the disc has a diameter of about 5 to 25 percent less
than the diameter of the tobacco column and filter plug. While not
wishing to be held to any particular theory, apparently, the
spacing around the disc reduces the pressure drop and permits the
use of a lower permeability disc, and thus produces greater
filtration. In the case of filters for conventional cigarettes,
which have a circumference of about 22-27 mm., the disc will have a
circumference of from about 16 mm. to about 26 mm.
Ordinarily, the disc will have a thickness of from about 0.1 mm. to
about 2.0 mm. The thickness may vary outside these ranges somewhat,
however, so long as the required pressure drop is maintained.
As earlier mentioned, it is preferred that the disc be of fibrous
composition. During smoking, fibrous discs having the herein
described parameters shrink, probably because of the moisture in
the tobacco smoke. As a result of this shrinkage, the pressure drop
produced by the disc will decrease during smoking. The pressure
drop of conventional baffle type filters increase during smoking
due to slugging. The combination of the filter disc with
conventional filtration material, as herein defined, results in a
filter which has a relatively uniform pressure drop throughout the
smoking of the attached tobacco column.
As previously noted, the plug used in conjunction with the above
described disc is preferably formed from a plurality of
longitudinally aligned, crimped, continuous cellulose acetate
filaments. Desirably, these filaments have a denier per filament of
from about 2 to about 30. The filaments may be of regular cross
section or may have a Y, X, or other cross-sectional configuration.
Sufficient filaments will ordinarily be employed to yield a plug
having a total denier of from about 20,000 to about 80,000.
While cellulose acetate filaments of the type described are the
preferred material employed for forming the plug, other fibrous
materials, such as other cellulose esters, cellulose ethers,
polyolefins, nylons, polyesters and cotton may be used for this
purpose, as may paper webs.
In order to be acceptable for use in conjunction with the
aforementioned disc, the plug should have a pressure drop of from
about 20 mm. to about 90 mm. of H.sub.2 O and preferably from about
30 mm. to about 60 mm. of H.sub.2 O. Lower pressure drops will not
yield a filter having optimum properties and higher pressure drops
will be unacceptable to most smokers.
The length of the plug employed is not critical to the present
invention so long as the plug exhibits the required pressure drop.
Ordinarily, to conform with commercial usage, the plug will have a
length of from about 10 mm. to about 30 mm., however.
The overall pressure drop of the filter will normally be from about
40 mm. to about 110 mm. of H.sub.2 O, preferably, 50 to 90 mm.
More than one plug may be used in conjunction with the disc. For
example, the disc may be disposed between two plugs. In this case,
the total length of the plugs would normally be equal to the length
of the above described single plug. The two plugs need not, of
course, be of equal length.
Similarly, more than one disc may be incorporated into the filter.
These discs may be of the same or different composition or
configuration. They may be in juxtaposition or separated by a plug
of high gas permeability filtration material.
The diameter of the plug will be approximately the same as the
diameter of the tobacco column.
FIG. 1 illustrates one embodiment of the invention in which a disc
10 is positioned between two plugs of filamentary filtration
material 11 and 12. It is to be noted that the diameter of disc 10
is less that the diameter of the filter or tobacco column attached.
Disc 10 is disposed substantially normally to the longitudinal axis
of the tobacco column and plug, as is the case with all filters of
the present invention.
If a decrease in the pressure drop produced by the disc is desired,
the disc may be perforated with one or more holes as shown, for
example, in FIGS. 2 and 3, or an edge of the disc may be trimmed as
shown in FIG. 4.
While the present invention has been described as being a
combination of a high pressure drop disc with a low pressure drop
plug of filtration material, it will be understood by one skilled
in the art that the filter may include, or be used in conjunction
with, other filtration materials or selective filtration additives,
either solid or liquid, such as carbon, silica gel, polyalkylene
glycols, etc.
The following examples are presented as illustrative of the present
invention and are not to be considered as being in limitation
thereof.
EXAMPLE I
A celluloid disc of 8 mm. in diameter of 0.5 mm. in thickness was
perforated with five 0.023 inch in diameter holes in a "star"
pattern. The disc was placed between two plugs of cellulose acetate
tow of 45,000 denier composed of 5 d.p.f. filaments of regular
cross section. The composite filter was wrapped in paper. The
initial pressure drop, or resistance to draw, of the filters varied
from 63 to 82 mm. H.sub.2 O. Upon attaching to a tobacco column and
smoking, the smoke removal efficiency was found to vary from 52 to
73 percent. Conventional cellulose acetate filters of comparable
pressure drop give an SRE of from about 44 to 51 percent.
EXAMPLE II
A paper disc of 0.5 mm. in thickness and 8 mm. in diameter was
perforated at the center of an 0.059 inch hole. The paper disc was
placed in juxtaposition with a plastic disc with the same diameter
similarly perforated. The two discs were then placed between two
plugs of 45,000 denier cellulose acetate tow comprised of 5 d.p.f.
filaments of regular cross section. The total length of the plug
was 20 mm. After wrapping the perforated plug in paper, the
pressure drop was measured and found to be from 67 to 81 mm.
H.sub.2 O. Smoking of the tobacco column attached to the filter
showed that the filter had an SRE of 66-76 percent. A conventional
cellulose plug of the same dimension has an SRE of from about 48 to
53 percent.
EXAMPLE III
A disc of compressed cellulose fibers was perforated in the center
with an 0.059 inch hole and positioned between two tow segments.
The filter had an initial pressure drop of 74 mm. of H.sub.2 O and
an SRE of 46.8 percent.
EXAMPLE IV
A porous paper disc of 8 mm. in diameter was placed between two 10
mm. cellulose acetate plugs having a total denier of 44,000 and
comprised of filaments having 3.3 d.p.f. and Y cross section. The
pressure drop of the samples varied from 71-75 mm. H.sub.2 O. The
SRE was approximately 50 percent.
EXAMPLE V
A disc of compacted spray spun polypropylene fibers having a
diameter of 8.15 mm. was perforated with a Number 17 needle in the
center and placed between two plugs of cellulose acetate filaments
having a d.p.f. of 25. The initial pressure drop was 64 mm. H.sub.2
O and the SRE was 49.1 percent.
While the present invention has been described in terms of specific
embodiments, it is to be understood that any variations and
modifications may be made within the scope of the present
invention.
* * * * *