Note: Descriptions are shown in the official language in which they were submitted.
1070587
This invention concerns improvements relating to filters
or filter material for tobacco smoke, especially though not
exclusively to cigarette filters.
Filters made from ~ibrous or filamentary material such as
paper or cellulose acetate are known to remove the particulate
matter from tobacco smoke. Some other components of tobacco smoke,
such as aldehydes, cyanides, sulphides and oxide, can be removed
to some extent by adsorption or absorption on a surface or by
chemical reaction. One of these vapour-phase constituents which
has been found to be difficult to remove from tobacco smoke is nitric
oxide. Nitric oxide is a substance which belongs to a group of
molecules of an electronic constitution such that there is
present an unpaired electron, which gives nitric oxide a free-
radical character.
According to the present invention, a tobacco-smoke filter
or ~ilter material contains granules of porous activated carbon
to which the nitroxide 4-oxo-2,2,6,6-tetramethylpiperidino-oxy
and/or the nitroxide 1-nitronyl-3-oxyl-4,4,5,5-tetramethyl-2-
phenyldihydroimidazole has been applied. Both oompounds are
stable, mon-volatlle, free-radical nitroxides.
By such a filter or material, a considerable filtration
efficiency for nitric oxide (NO) in particular and ~or other
const$tuents which it may be desired to re~ove, can be obtained
without disadvantageous concomitant effects. It is believed that
the reduction in nitric oxide may be linked with the porosity of
the treated carbon and that, desirably, the pore volume should be
at least 0.2 cc/g and the surface area of the said carbon at least
50 m /g. The pre~erred compound 4-~xo-2,2,6,6-tetramethylpiper-
idino-oxy, has the structural formula:-
1070587
C~3
C~
The level of loading of the nitroxide carbon expressed
as a percentage by weight of the untreated carbon, may be from 0.5to 25% and is preferably within the range of 1.0 to 15%. In
commercial practice, the loading level wil~ probably be within
the range of 3 to 10%.
Example 1: 1g of activated carbon in porous granular form
of the type supplied under the trade description "BPL" by the
Pittsburg Activated Carbon Co. was added to a æolution of 100 mg
of 4-oxo-2,2,6,6-tetramethylpiperidino-oxy in 5 ml of ethanol. The
solvent was allowed to evaporate at room temperature until the
granular carbon was dry and free-flowing. This gave a loading
level of approximately 10%. A triple filter containing a bed
composed of 100 mg of this treated carbon disposed between two
sections of cellulose acetate, each 5 mm long, was atteched to a
cigarette having a ~illing of flue-cured tobacco. On smoking the
cigarette through this fil~er, 72% by weight of nit~ic oxide was
removed from the tobacco smoke.
Tests were carried out with a number of available grnnular
activated carbons and with different loadings of the same nitroxide
as in Example ~, using the same application procedure as in that
Example. The results are as tabulated below:
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1070587
.
CARBON LOADING NO Filtration NO Filtration
(% by Efficiency (%) Efficiency (~)
weight) Carbon with Carbon without
nitroxidenitroxide
BPL (Trade Mark) 10 72less than 10
BPL 5 60less than 10
Anthrasorb CC1430/70 10 68 less than 10
(Trade Mark)
MF3 (Trade Mark) 10 57 13
Actibon X 10 45less than 10
(Trade Mark)
Picatif 60143 7 43less than 10
(Trade Mark)
Carbomafra GC 7 43less than 10
(Trade Mark)
207C (Trade Mark) 10 43 17
The suppliers of the several types of carbon were
as follows:
BPL Pittsburgh Activated Carbon Co., of
Pennsylvania, U.S.A.
Anthrasorb CC1430/70 Cardian Chemical Co., of Cheltenham,
England
MF3 Chemviron Ltd., of Brussels, Belgium
Actibon X Hooker - Mexicana S.A. de C.V., of
Mexico
Picatif 60143 Pica, of Paris, France
Carbomafra GC British Traders & Shippers Ltd., of
B
1070587
207C Sutcliffe - Speakman Ltd., of Leigh,
Lancashire, England.
Actibon X was rendered non-acidic, before application, by treatment
with a 0.1M aqueous solution of sodium hydroxide.
Example 2: 1-nitronyl-3-oxyl-4,4,5,5-tetramethyl-2-phenyl-
dihydroimidazole was applied to carbon granules of the type BPL
referred to above, using the same procedure as in Example 1, but
with a loading level of 5%. A triple filter was prepared as
described in that ex~mple. A ~iltration efficiency for nitric
oxide of 44% was obtained.
The amount of treated carbon to be provided in a filter
will depend upon the filtration efficiency required as w~ll as
upon the nitroxide used. me effect of variation of the weight
of treated carbon is illustrated by the table below: The results
tabulated were obtained with the Anthrasorb type of granular
carbon, referred to above, treated as described in Example 1 but
with a loading level of 7% of the 4-oxo-2,2,6,6-tetramethylpiper-
ldlno-oxy nitroxide. The treated carbon was incorporated in
triple filters as described in that Example.
..
WEIGHT OF CARBON FILTRATION EFFICIENCY (~)
(mg) For NO
. . .__
29
100 61
150 75
200 81
The efficiency of filtration for nitric oxide can be enhanced
by so called "ventilation" of the filter, for example by use of a
perforated or porous filter wrapper. Thus, if, in a triple filter
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1070587
whose centre section comprises a bed of the treated carbon, either
the tobacco-end section or the said centre section is ventilated
in known manaer, the filtration efficiency of the filter is signi-
ficantly increased. For example, a triple filter of this kind
with ventilation holes in the wrapping of the centre section was
attached to cigarettes of flue-cured tobacco. There were 3 rows
of holes 1 mm apart, the holes being rectangular (0.1 mm x 0.5 mm)
and the first row being 7 mm from the end of the tobacco rod. 100 mg
of carbon of the Anthrasorb type with 10% loading of the 4-oxo-
2,2,6,6-tetramethylpiperidino-oxy nitroxide was employed as the
aforesaid bed. With the ventilation holes closed by covering with
non-porous tape, the overall reduction of nitric oxide was found
to be 67% whereas, with the holes uncovered, the overall reduction
was 89%.
