Note: Descriptions are shown in the official language in which they were submitted.
CA 02472385 2004-07-05
D E S C R I P T I O N
SMOKING FILTER AND SMOKING ARTICLE
Technical Field
The present invention relates to a smoking filter
and a smoking article.
Background Art
Various chemical components are contained in
mainstream smoke that is inhaled by the smoker in
smoking a smoking article. Among these chemical
components, the lower aldehydes represented by
formaldehyde are difficult to remove by adsorption on
an ordinary smoking filter. Naturally, it is desirable
to remove the aldehydes from the mainstream smoke.
It was customary to use a filter having activated
carbon added thereto as an adsorbent for removing
formaldehyde from the mainstream smoke. In addition,
it was attempted to use various other adsorbents.
However, the adsorbent used in the past also
adsorbs the components other than formaldehyde, with
the result that it was possible for adverse effects to
be given to the flavor and taste of the smoking
article.
An object of the present invention is to provide
a smoking filter and a smoking article capable of
selectively removing formaldehyde contained in
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2
mainstr am smoke.
Disclosure of Invention
he invention is directed to a cigarette comprising:
a tobacco rod; and
a filter connected to the tobacco rod and containing a hydrotalcite compound
in a ran e of between 48.3 and 146.7 mg/cigarette.
T e smoking filter of the cigarette according to the present invention
contain a hydrotalcite compound exhibiting a lamellar structure in which a
large
number f octahedral layers of a metal hydroxide are laminated one upon the
other.
P eferably, the hydrotalcite compound used in the present invention is
represe ted by a general formula:
2+1-XM3+x (OH) 2 (An-) x/n - mH2O
here M2+ represents a divalent. metal ion selected
from he group consisting of a Mg ion, a Zn ion, a Ni
ion and a Ca ion, M3+ represents an Al ion, An-
represents an anion having a valency of n, which is
selected from the group consisting of CO3, SO4, OOC-
COO, 1, Br, F, NO3, Fe (CN) 63-, Fe (CN) 64-, phthalic
acid, isophthalic acid, terephthalic acid, malefic acid,
alken 1 acid and its derivative, malic acid, salicylic
acid, acrylic acid, adipic acid, succinic acid, citric
acid nd sulfonic acid, 0.1 < x < 0.4, and 0 < m < 2.
he smoking filter of the present invention is
prepared by dispersing a hydrotalcite compound having
an av rage particle diameter falling within a range of
betwe n 200 mm and 800 gm in, for example, the fiber
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2a
tow or an unwoven fabric sheet. The typical fiber used
in the present invention is formed of cellulose
acetate.
It is possible for the smoking filter of the
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3
present invention to be prepared by forming a paper
sheet added with a hydrotalcite compound having an
average particle diameter not larger than 10 p m.
It is possible for the smoking filter of the
present invention to include a plurality of filter
segments, at least one filter segment containing
a hydrotalcite compound. In this case, it is possible
to use a charcoal filter segment in addition to the
filter segment containing the hydrotalcite compound.
It is possible for .the smoking filter of the
present invention to include a plurality of filter
segments and hydrotalcite particles filled in the space
present between the adjacent filter segments.
Further, the smoking article of the present
invention includes the smoking filter referred to above
and a tobacco rod connected to the smoking filter.
Brief Description of Drawings
FIG. 1 is a perspective view showing a filter
manufactured in the Examples of the present invention;
FIG. 2 shows the construction of an apparatus used
in the Examples of the present invention for measuring
formaldehyde contained in cigarette mainstream smoke;
FIG. 3 is a graph showing the removal rate of
formaldehyde achieved by various adsorbents;
FIG. 4 shows a collecting method of the vapor
phase components from cigarette mainstream smoke, which
was employed in the Examples of the present invention;
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FIG. 5 shows gas chromatography of the vapor phase
components contained in cigarette mainstream smoke,
which was used in the Examples of the present
invention;
FIG. 6 is a graph showing the relationship between
the vapor pressure of the vapor phase components and
the removal rate of the vapor phase components,
covering the case where hydrotalcite or charcoal was
used as the adsorbent;
FIG. 7A is a graph showing the particle size
distribution of the hydrotalcite particles;
FIG. 7B is a graph is a graph showing the
relationship between the average particle diameter of
the hydrotalcite particles and the resistance to draw;
FIG. 8 is a graph showing the relationship between
the surface area of the hydrotalcite particle and the
formaldehyde reduction rate;
FIG. 9 is a perspective view showing the
construction of the paper filter prepared in Example 5;
FIG. 10 is a perspective view showing the
construction of the triple segment type filter prepared
in Example 6; and
FIG. 11 is a perspective view showing the
construction of a filter in another Example of the
present invention.
Best Mode for Carrying Out the Invention
As a result of extensive research conducted from
CA 02472385 2004-07-05
various viewpoints in an attempt to find an adsorbent
effective for lowering the formaldehyde content in
mainstream smoke, the present inventor has found that
hydrotalcite compounds permit effectively removing
5 formaldehyde.
The hydrotalcite compound exhibits a lamellar
structure in which a large number of octahedral layers
of a divalent or trivalent metal hydroxide are
laminated one upon the other, and an anion is
intercalated in the octahedral layers. The octahedral
layer is referred to as a host and exhibits basicity.
It is considered reasonable to understand that the
removal of formaldehyde achieved by the hydrotalcite
compound results from contribution of the basicity of
the host and from the ion exchange function performed
by the intercalated anions.
In the present invention, it is possible to use a
natural or synthetic hydrotalcite compound. The
hydrotalcite compound is represented by a general
formula:
M2+1-xM3+x (OH) 2 (An-) x/n . mH2O.
In the most general hydrotalcite compound, a Mg
ion constitutes the divalent metal ion M2+ included in
the general formula given above, an Al ion constitutes
the trivalent metal ion M3+, and CO32- or SO42-
constitutes the anion An-. It is possible for a Zn
ion, a Ni ion or a Ca ion to constitute the divalent
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6
metal ion M2+ in addition to the Mg ion. Also, it is
possible for the anion to be selected from the group
consisting of OOC-COO, Cl, Br, F, NO3, Fe (CN) 63-,
Fe(CN)64-, phthalic acid, isophthalic acid,
terephthalic acid, maleic acid, alkenyl acid and its
derivative, malic acid, salicylic acid, acrylic acid,
adipic acid, succinic acid, citric acid and sulfonic
acid in addition to CO32- and 5042-. The symbol x in
the general formula is larger than 0.1 and smaller
than 0.4, i.e., 0.1 < x < 0.4, and the symbol m is
larger than 0 and smaller than 2, i.e., 0 < m < 2.
The Mg-Al-based hydrotalcite compound is stable in the
case where the value of x falls within a range of
between 0.20 and 0.33.
In order to manufacture the hydrotalcite, a
reaction is carried out by adding an alkali carbonate
or both an alkali carbonate and a caustic alkali to an
aqueous solution containing a water-soluble aluminum
salt selected from the group consisting of aluminum
sulfate, aluminum acetate and aluminum potassium
sulfate or aluminic acid and a water-soluble magnesium
salt while maintaining the pH value of the reaction
mixture at 8.0 or more.
It is possible to control a micro pore size of the
hydrotalcite compound by, for example, the size of the
anion intercalated in the hydrotalcite compound. It is
also possible for the hydrotalcite compound to perform
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various functions depending on the nature of the anion
and on the state of the interlayer water.
Various types are conceivable as given below in
respect of a smoking filter having a hydrotalcite
compound added thereto:
(1) A smoking filter in which the hydrotalcite
compound is dispersed in the fiber tow or an unwoven
fabric made of cellulose acetate.
(2) A smoking filter prepared by forming a paper
sheet added with a hydrotalcite compound.
(3) A smoking filter formed of at least two
segments comprising at least one segment, which is
formed of the smoking filter referred to in item (1) or
(2) given above, and the other segment, which is formed
of the conventional cellulose acetate filter or
a charcoal filter.
(4) A smoking filter prepared by filling the space
of the plug-space-plug structure with the hydrotalcite
compound. In this case, the plug is selected from the
conventional cellulose acetate filter or charcoal
filter, or the filter referred to in item (1) or (2)
given above. Also, where there are two or more spaces,
it suffices to fill at least one space with the
hydrotalcite compound, and it is possible to fill the
other space with charcoal.
It is desirable to control the particle diameter
of the hydrotalcite compound as follows. In the case
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of using a smoking filter in which the hydrotalcite
compound is dispersed in the cellulose acetate tow or
unwoven fabric, or in which the hydrotalcite compound
is filled in the space of the plug-space-plug, it is
desirable for the hydrotalcite compound to have a
particle diameter of 200 to 800 um, more desirably 400
to 600 gm. On the other hand, in the case of using a
smoking filter prepared by forming a paper sheet made
by adding the hydrotalcite compound, it is desirable
for the hydrotalcite compound to have a particle
diameter not larger than 10 um.
(Examples)
Example 1:
A hydrotalcite compound represented by
Mg6A12(OH)16CO3.4H20 was used. The particle diameter
of the hydrotalcite compound was controlled to 250 to
,500 um by pulverization and sieving. A filter 1 shown
in FIG. 1 was prepared by using the hydrotalcite
compound. To be more specific, a hydrotalcite powder 3
was filled in the space present between two acetate
filter segments 2, 2 each wrapped with a plug wrapper
and, then, the resultant structure was wrapped with a
forming paper 4 so as to prepare the filter 1 of the
plug-space-plug structure.
For comparison, filters of the plug-space-plug
structure as shown in FIG. 1 were prepared by using
following adsorbents: charcoal, charcoal having a high
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specific surface area, alkali metal salt impregnated
charcoal, amine impregnated charcoal, active alumina,
magnesium oxide, aluminum oxide, magnesium silicate,
zinc oxide, silica gel, zeolite, construction material
pulp for formalin, a column packing material for gas
chromatography (GC), and water-absorbing resin.
These filters were made equal to each other in the
amount of the adsorbent. Also, a test cigarette was
prepared by connecting a tobacco section containing 12
mg of tar to each of the filters.
The amount of formaldehyde contained in cigarette
mainstream smoke was measured according to "Health
Canada - Official Method" (2,4-DNPH-HPLC method) so as
to provide the removal rate of formaldehyde.
To be more specific, 9.51 g of 2,4-dinitrophenyl
hydrazine (DNPH) was dissolved in 1L of acetonitrile
under heating, followed by adding 5.6 mL of a 60%
perchloric acid to the solution and subsequently adding
ultra pure water to the solution, thereby preparing 2L
of a trapping solution.
The construction of the measuring apparatus will
now be described with reference to FIG. 2. As shown in
the drawing, a DNPH trapping solution 12 is put in a
Drechsel-type trap 11. The Drechsel-type trap 11 has
an inner volume of 100 mL, and an amount of the DNPH
trapping solution 12 is 80 mL. The trap 11 is put in
an ice water bath 13 so as to be cooled. The lower end
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of a glass pipe 14 to which a cigarette 10 is attached
is dipped in the trapping solution 12 within the
trap 11. Further, a glass pipe 15 having a Cambridge
pad 16 mounted thereto is arranged to communicate with
5 the dead volume of the trap 11, and a smoking machine
17 was connected to the Cambridge pad 16.
The cigarette 10 was attached to the glass pipe 14
so as to permit the cigarette 10 to be automatically
smoked under the standard smoking conditions specified
10 in ISO standards. To be more specific, the operation
of sucking 35 mL of the smoke in a single puff for two
seconds for a single cigarette was repeated at an
interval of 58 seconds. While the mainstream smoke was
being bubbled, formaldehyde was converted into a
derivative of DNPH. Two cigarettes were used for the
measurement. In this case, the cigarettes using the
different adsorbents were controlled to exhibit the
same pressure loss.
The formaldehyde derivative thus formed was
measured by high-performance liquid chromatography
(HPLC). In the first step, the trapping solution was
filtered, followed by diluting the filtered trapping
solution with a Trizma Base solution (4 mL of trapping
solution : 6 mL of Trizma Base solution). Then, the
diluted solution was measured by the HPLC. The
measuring conditions of the HPLC were as follows:
Column: HP LiChrospher 100RP-18(5 )250 X 4 mm
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Guard column: HP LiChrospher 100RP-18(5/.c)4 X 4 mm
Column temperature: 30 C
Detecting wavelength: DAD 356 nm
Injection amount: 20 L
Mobile phase: Gradients by three phases
(solution A: ultra pure aqueous solution containing 30%
of acetonitrile, 10% of tetrahydrofuran and 1% of
isopropanol; solution B: ultra pure aqueous solution
containing 65% of acetonitrile, 1% of tetrahydrofuran
and 1% of isopropanol; solution C: 100% of
acetonitrile).
The removal rate of formaldehyde is represented
by:
E = (W - W')/W
where E represents the removal rate of
formaldehyde, W represents the amount of formaldehyde
measured in the case of using a cigarette containing no
adsorbent, and W' represents the amount of formaldehyde
measured in the case of using a cigarette containing an
adsorbent.
FIG. 3 is a graph showing the removal rates of
formaldehyde in the case of using various adsorbents.
As apparent from FIG. 3, formaldehyde was most
effectively removed in the case of using hydrotalcite
as the adsorbent.
Example 2:
The removal rate of the vapor phase components
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contained in cigarette mainstream smoke was measured by
using as an adsorbent a hydrotalcite compound or
charcoal constituting the most general adsorbent for
a cigarette.
A filter similar to that shown in FIG. 1 was
manufactured as in Example 1 by preparing a
hydrotalcite compound having a particle diameter of 250
to 500 gm or charcoal as an adsorbent and loading the
adsorbent in an amount of 50 mg. Then, a cigarette was
prepared by connecting a tobacco section containing
12 mg of tar to the filter thus manufactured.
The method of measuring the removal rate of the
vapor phase components from cigarette mainstream smoke
will now be described with reference to FIGS. 4 and 5.
FIG. 4 shows the trapping method of the vapor
phase components. As shown in the drawing, a cigarette
10 was attached to a smoking machine 17 so as to permit
the cigarette 10 to be automatically smoked under the
standard smoking conditions specified in the ISO
standards. In this case, the particle phase in the
mainstream smoke was removed by a Cambridge filter, and
the vapor phase was trapped by a gas bag 20. Also, the
operation of sucking 35 mL of the smoke in 2 seconds in
a single puff for each cigarette was repeated at an
interval of 58 seconds. Further, 10 conditioned
cigarettes (conditioned under temperature of 22 C and
humidity of 60%) were automatically smoked.
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FIG. 5 shows gas chromatography. As shown in the
drawing, a prescribed amount of the vapor phase
components trapped in the gas bag 20 is stored in
a sample loop 21. After a standard gas is injected,
the vapor phase components are injected into a gas
chromatograph 22. The components are separated in a
column (DB-WAX) and detected in a detector. Further,
the amounts of the components are analyzed by using a
program installed in a personal computer 23. The
analytical value was obtained by dividing the peak area
of each of the vapor phase components by the peak area
of the standard gas.
The removal rate E of each of the vapor phase
components is represented by:
E _ (A - A') /A
where E represents the removal rate of each of the
vapor phase components, A represents the analytical
value of the component measured by using a cigarette
containing no adsorbent, and A' represents the
analytical value of the component measured by using a
cigarette containing an adsorbent.
FIG. 6 is a graph showing the relationship between
the vapor pressure of the vapor phase component and the
removal rate of the component. As apparent from
FIG. 6, the removal rate is increased with increase in
the vapor pressure of the vapor phase component in the
case of using charcoal as an adsorbent. On the other
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hand, in the case of using a hydrotalcite compound as
an adsorbent, the removal rate is specifically high in
respect of formaldehyde, supporting that the
hydrotalcite compound permits selectively removing
formaldehyde.
Example 3:
In the case of using a hydrotalcite compound in a
cigarette filter constructed as shown in, for example,
FIG. 1, it is necessary to control appropriately the
size of the hydrotalcite compound in order to control
the resistance to draw and the outflow of tar/nicotine.
If the hydrotalcite compound is granulated, it is
possible to prepare samples differing from each other
in the particle size distribution. In this case, the
samples are classified depending on the average
particle diameter of the hydrotalcite compound.
FIG. 7A shows three types of samples having the average
particle diameters of 250 gm, 500 um, and 800 um,
respectively.
Filters of the construction as shown in FIG. 1
were prepared by using hydrotalcite particles differing
from each other in the average particle diameter.
These filters differed from each other in the loading
amount of the hydrotalcite particles. For reference,
filters of the construction shown in FIG. 1 were also
prepared by using charcoal. These filters also
differed from each other in the loading amount of the
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charcoal.
The resistance to draw was examined in respect of
these filters under the sucking flow rate of
1050 mL/min. Here, the resistance to draw was
5 calculated by excluding the resistance to draw due to
the two acetate filter segments 2, 2 shown in FIG. 1.
FIG. 7B is a graph showing the relationship
between the average particle diameter and the
resistance to draw. As apparent from FIG. 7B, the
10 resistance to draw is high in the case of using the
adsorbent particles having the average particle
diameter of 250 gm and is low in the case of using the
adsorbent particles having the average particle
diameter of 800 um. FIG. 7B also indicates that it is
15 reasonable to use hydrotalcite particles having the
average particle diameter falling within a range of
between 400 um and 600 um in designing cigarettes.
In the case of using granulated particles, it is
possible to provide hydrotalcite particles having a
desired size by employing any granulating method such
as rolling granulation, compression molding, coating
granulation, or extrusion molding. It should be noted
in this connection that, in order to avoid the breakage
of the hydrotalcite particles in the manufacturing
process of the filter, it is desirable to employ a
granulating method that permits manufacturing
granulated hydrotalcite particles having an appropriate
CA 02472385 2004-07-05
16
hardness. The present inventor found that it is
possible to prevent the hydrotalcite particles from
being broken in the manufacturing process of the filter
if the hydrotalcite particles have a hardness falling
within a range of between 300 g/mm2 and 3,000 g/mm2.
Example 4:
This Example is intended to support that the
reduction rate of the formaldehyde content in
mainstream smoke achieved by the hydrotalcite particle
is dependent on the surface area of the hydrotalcite
particle.
Various granulated hydrotalcite particles were
prepared by means of (A) rolling granulation, (B)
compression molding, and (C) extrusion molding.
The average surface area per unit weight of the
hydrotalcite particles was calculated by using a laser
scattering type particle size distribution measuring
apparatus.
Filters of the construction as shown in FIG. 1
were prepared by using hydrotalcite particles having
various surface areas. In this case, the total surface
area of the hydrotalcite particles was adjusted by
controlling the amount of the hydrotalcite particles.
Then, the relationship between the total surface area
of the hydrotalcite particles and the reduction rate of
the formaldehyde content in the mainstream smoke was
examined. FIG. 8 is a graph showing the result.
CA 02472385 2004-07-05
17
As apparent from FIG. 8, it has been found that
the reduction rate of the formaldehyde content in the
mainstream smoke can be increased with increase in the
total surface area of the hydrotalcite particles. This
tendency is exhibited regardless of the granulating
method of the hydrotalcite particles.
Example 5:
This Example is intended to examine the reduction
rate of formaldehyde contained in mainstream smoke,
which is achieved by a paper filter to which
hydrotalcite particles are added, and by a cellulose
acetate filter to which granulated hydrotalcite
particles are added.
Specifically, a paper sheet was made while adding
hydrotalcite particles having an average particle
diameter not larger than 10 gm. Then, the paper
filter 7 shown in FIG. 9 was prepared by using the
resultant paper sheet. For comparison, a filter was
prepared by forming a paper sheet to which hydrotalcite
particles were not added.
A filter was also prepared by dispersing
granulated hydrotalcite particles in the cellulose
acetate tow. For comparison, a cellulose acetate
filter was prepared without using hydrotalcite
particles.
Incidentally, the filters thus prepared were 25 mm
long and were made as uniform as possible in the
CA 02472385 2004-07-05
18
resistance to draw.
The reduction rate of the formaldehyde content in
mainstream smoke was examined by using the filter thus
prepared. Table 1 shows the result.
As shown in Table 1, the ratio of formaldehyde
outflow to tar outflow was decreased in the paper
filter containing the hydrotalcite particles, compared
with the acetate filter containing the hydrotalcite
particles. It is considered reasonable to understand
that the result was achieved by the large contact
surface area of the hydrotalcite particles having an
average particle diameter not larger than 10 u m
dispersed in the paper filter.
CA 02472385 2004-07-05
19
ro .H M cr Ol
E-+ CO Ol ~,O
w v N l0 N
O
4J
O 4J
4-I ?4 lO o t O M
4-) ro r o
O =r-1 N N CO
Cam, ~'
3 a)
4-d M Ol ,-1 N
41 L *" i m c1
o N (N
r lO
S4 U
Q ro \
H
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U 3
ro cf) 0) co i )
V7 'CS E Ln If) Lr)
='-I
C
tr Ln in in u')
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F:~ w a w
CA 02472385 2004-07-05
Example 6:
This Example is intended to support that the
reduction rate of the organic vapor components can be
increased by the combination of a hydrotalcite filter
5 and a charcoal filter.
Filters I, II, III of the triple segment structure
including an acetate filter segment, a hydrotalcite
(HT) filter segment and a charcoal filter segment as
shown in Table 2 were prepared. The acetate filter
10 segment was prepared by bundling cellulose acetate tow
and was 7 mm long. The hydrotalcite (HT) filter
segment was prepared by bundling cellulose acetate tow
having 70 mg of hydrotalcite particles dispersed
therein and was 10 mm long. Further, the charcoal
15 filter segment was prepared by bundling cellulose
acetate tow having 70 mg of charcoal particles
dispersed therein and was 10 mm long.
FIG. 10 shows the construction of the filter III
shown in Table 2. As shown in the drawing, a charcoal
20 filter segment 5 is arranged on the side of the cut
tobacco, an acetate filter segment is arranged on the
inhaling side, and an HT filter segment 6 is arranged
intermediate between the charcoal filter segment S and
the acetate filter segment 2.
The reduction rate of the total organic vapor
(TOV) and the reduction rate of formaldehyde (FA) from
mainstream smoke were examined by using these filters.
CA 02472385 2004-07-05
21
Table 2 shows the results.
As shown in Table 2, the filter III permits
lowering the content of the total organic vapor because
of the function of the charcoal filter and also permits
lowering the formaldehyde content because of the
function of the hydrotalcite (HT) filter.
CA 02472385 2004-07-05
22
C
0
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.N
Ex riS ~O [~ Cl H
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N
r
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.r-i a) r- co CC)
> 41
El r rtl ~O N O N
u lfl N ( ~
(d 41 M -W (D
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In U U U L~~ 44 4-4
off
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U 4-1 4-a 4a > O
U) -i
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O Sa (0 -o
W o a1)` -Li 'm1 o 1w1 ro on
-W u 10 u U C~ 'H -H r-1 r-I
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JJ ~4 r--1 r--I
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t~ .0 4J Q) =r-4 a) a)
F--(
CA 02472385 2004-07-05
23
Various modifications are conceivable as follows
in respect of the filter of the present invention.
For example, in the filter of the construction as
shown in FIG. 1, it is possible to use another filter
segment in place of at least one of the acetate filter
segments 2. To be more specific, it is possible to use
a hydrotalcite filter segment or a charcoal filter
segment in place of at least one of the acetate filter
segments 2. In the case of using a charcoal filter
segment, it is desirable to arrange the charcoal filter
segment on the cut tobacco side as in FIG. 10.
In the structure shown in FIG. 10, the cellulose
acetate tow having a hydrotalcite compound dispersed
therein were used for forming the hydrotalcite filter
segment. Alternatively, it is also possible to use a
hydrotalcite filter segment prepared by forming a paper
sheet made by adding hydrotalcite compound.
It is also possible to prepare a filter of a four-
segment structure by attaching an additional filter
segment to the filter of the three-segment structure
shown in FIG. 10.
Further, it is possible to use a filter comprising
a charcoal filter segment 5, a space filled with
hydrotalcite particles 3, a hydrotalcite (HT) filter
segment 6 and an acetate filter segment 2, as shown in
FIG. 11.
It is possible for the hydrotalcite filter segment
CA 02472385 2004-07-05
24
6 to be acetate filter-based or paper filter-based in
this case, too. It is possible for the arrangement of
the space filled with the HT particles 3 and the HT
filter segment 6 to be opposite to that shown in
FIG. 11. In FIG. 11, the space is filled with HT
particles. Alternatively, it is possible for the space
to be filled with charcoal particles.
Industrial Applicability
According to the present invention, it is possible
to provide a smoking filter and a smoking article,
which permit effectively lowering the formaldehyde
content in mainstream smoke.
