CIGARETTE

CIGARETTE

Abrégé anglais

Cigarette, the wrapper of which comprises a layer of paper with water
impregnation
made from a cellulose derivative.

Revendications

4
Claims
1. Cigarette, the tobacco strand of which is wrapped around with a layer of
paper with water repellent impregnation made from a cellulose derivative,
preferably of ethyl cellulose, wherein in order to obtain air permeability in
the wrapper of at least 20 Coresta units, preferably at least 50 Coresta
units,
the cellulose derivative is applied in several layers.
2. Cigarette according to claim 1, wherein the cellulose derivative is applied
on
both sides of the paper.
3. Cigarette according to claim 1 or 2, wherein the cellulose derivative is
applied in a quantity of at least 1 g/m2.
4. Cigarette according to one of claims 1 to 3, wherein the cellulose
derivative
is applied by means of a coating roller in a gravure process.
5. Cigarette according to one of claims 1 to 4, wherein the wrapper is
composed
of only one layer of paper,

Description

CA 02300715 2000-03-10
1
The invention is based on the problem of avoiding spotting on the wrappers of
cigarettes.
The buyers of cigarettes consider the spotless white appearance of a cigarette
as an
indication of quality. Even if this opinion is not particularly correct - in
hot, humid
climates cigarettes can show discoloration even after a short period of
storage, which
~o does not affect the smoke flavour - manufacturers have to focus upon market
expectations.
Spotting of cigarette paper can be explained in that dissolved substances
contained in
the tobacco can penetrate the paper at the points of contact between the paper
and the
~5 tobacco particles, as said paper is both porous and hydrophilic.
It would be conceivable to reduce spotting on cigarette paper in that said
paper is
coated with any substances that would make the paper completely impervious.
Such
coatings have been proposed in order to effect rapid extinguishing of
discarded
2o cigarettes. In order to be able to control the content of different
substances contained
in the smoke, however, the cigarette manufacturer is generally interested in a
certain
degree of air permeability of the cigarette paper. The problem is consequently
to, on
the one hand, keep the paper permeable for air, and on the other hand to
reduce the
permeability for dissolved cigarette ingredients.
For solving the problem, US-A 5,143 099 proposed to form the cigarette wrapper
using two layers of paper, wherein the inner wrapper is provided with a very
high
degree of permeability, so tha; the overall permeability remains sufficient.
In this
context, the possibility of making the inner wrapper water repellent by adding
0.5%
so alkyl ketene dimer was mentioned.
In comparison with the prior art described, the object of the invention is to
make the

CA 02300715 2000-03-10
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use of two layers of paper superfluous, this being by means of an impregnating
agent
that is harmless and changes the smoke flavour as little as possible.
It was unexpected that providing the cigarette with a wrapper that comprises a
layer of
paper with water repellent impregnation made from a cellulose derivative, in
particular
of ethyl cellulose, would lead to a solution of the object. EP 0 419 981 does
describe
such a cigarette, in which, however, the air permeability is below 5 Coresta
units.
The invention is based on the recognition that the impregnation can be
sufficiently thin
~o to retain the desired air permeability, if it is applied in several layers.
It is thus
provided according to the invention that the cellulose derivative is applied
in several
. layers in order to obtain an air permeability in the wrapper of at least 20,
preferably 50
Coresta units.
~5 Different cellulose derivatives per se satisfy the physical criteria
required with respect
to air permeability and water permeability in the impregnated paper, for
example,
sufficiently highly derived cellulose ether and cellulose ester (for example,
nitrocellulose). Ethyl cellulose is preferred, however, as it is harmless - it
complies
with the German regulations - and makes practically no change to the smoke
flavour.
zo
Further details of the invention will be discussed hereinafter with reference
to
comparative tests.
z5 Cigarette papers with a substance of 26g/m2 were coated, in a gravure
process by
means of a coating roller, with cellulose azetoproprionate (CAP) or with
cellulose
azetobutyrate (CAB) or with ethyl cellulose (EC). The amount applied was
approximately 0.7 g/mz. Cigarettes were manufactured with the cigarette paper
manufactured in this way.
In order to test their spotting tendency, the cigarettes were stored packaged
and
unpackaged at either 20°C and 60% relative humidity or 30°C and
80% relative

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humidity. Examination for spotting (in each case 100 cigarettes) was carried
out
immediately after production and after 24 and 48 hours. An evaluation was made
according to spot size and number, and the results were converted, by means of
weighting, into a point system.
The evaluation produced the following results:
Coating with 0.7 g EC 572 points
Coating with 0.7 g CAP 223 points
Coating with 0.7 g CAB 77 points
~a
Although ethyl cellulose coated paper showed a comparatively strong tendency
for
spotting (large number of spots), the further development was carried out with
this
material, as an undesired change in the smoke character was determined with
CAP and
' CAB. Even with the use of EC coated paper, a significantly lower spotting
frequency
~ 5 was nevertheless determined, compared with uncoated paper. After
approximately one
month, however, the cigarettes manufactured using paper coated with EC showed
no
dark spots, whereas large yellow spots appeared on those with uncoated paper.
This is
probably because coloring agents penetrate the paper through flaws in the
coating, the
spreading of which agents is prevented by the coating. Due to these
observations, the
2o tests were repeated with twice-coated paper, that is to say with cigarette
paper loaded
with 1.4 g/m2. With this, the spotting tendency decreased, according to the
method of
calculation described hereinabove, to 56 points, that is to say it reduced by
the power
of 10 compared to the single coating. This excellent result was confirmed in
long-term
testing.
It is to be emphasised in particular that the success described was obtained
even
though the porosity of the paper, which was SO Coresta units before coating,
was still
20 Coresta units after coating. Initial tests with more porous paper as the
starting
material confirm that even ~~ith a final porosity of 50 Coresta units, the
radical
so reduction in the tendency to spot, according to the invention, was
obtained. (One
Coresta unit (CU) indicates how many cmz of air flow per minute through an
area of 1
cm2 of paper under pressure of a 10 cm head of water.)