Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CONTROLLED MOISTURE RELEASE HUMIDIFIER FOR USE WITH
TOBACCO PRODUCTS
BACKGROUND OF THE INVENTION
The present invention relates to a controlled moisture release humidifier for
use with
tobacco products.
The tobacco in products such a cigarettes, cigars and loose tobacco for pipe
smoking or
roll-your-own cigarettes is prone to drying out both during the pre-use
storage period and
/0 particularly after the product packaging has been opened. This is
undesirable, since tobacco
becomes less palatable as it dries.
Expensive cigars are generally stored in specially designed humidors
specifically to address
this problem by keeping the cigars at a desired level of humidity to prevent
drying. A more
rudimentary approach is often used by consumers of loose tobacco; a piece of
apple or
potato peel placed in the tobacco pouch or tin can help to keep the tobacco
moist or can
re-moisten tobacco that has become too dry. However, this method may not be
considered
hygienic, and may taint the tobacco with unwanted scents or flavours.
Various humidification devices and moisture dispensers have therefore been
proposed for
use with tobacco products, in particular for use in tobacco pouches and tins
and cigarette
packs. Typically, the devices comprise a source of moisture that can emit
water vapour
which is surrounded by a permeable enclosure such as a housing, casing, layer
or pouch
which keeps the moisture source separate from the tobacco but allows the water
vapour to
be transmitted to the tobacco. The moisture source is often some form of water-
absorbent
medium such as cotton wool, blotting paper, sponge, florist's foam, or
polyacrylamide gel
or crystals, which is soaked in water or salt solution. The permeable
enclosure may be rigid
or flexible, and may be made permeable by the provision of perforations or
apertures
therein, or may be an inherently permeable membrane material. Some devices are
incorporated into tobacco packages, while others are independent devices that
can be
inserted into a tobacco product container. Examples of such devices can be
found in GB
2,345,431, GB 2,265,295, GB 1,369,992, GB 741,475, GB 567,141, GB 308,127,
GB119,489, EP 531,075, EP 363,194, EP 348,840, US 5,957,380, US 5,957,277, US
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5,829,452, US 3,801,011, US 1,847,989, US 1,871,419, DE 4000143, DE 20 2005
008 520,
DE20 2005 010 286 and FR 2,619,289. WO 02/12089 describes the use of a gel to
hold
water for the purposes of humidifying tobacco products and other items. The
gel is used so
that there is no free liquid water present, the escape of which would damage
the tobacco
products, and also because it is suitable to both give out water vapour and
reabsorb it.
Hence a two-way moisture exchange is provided to maintain a particular
humidity level in
the environment of the tobacco products; this is well suited for use with
cigars.
SUMMARY OF THE INVENTION
/0 A first aspect of the present invention is directed to a humidifier for use
with tobacco
products, comprising a gel body comprising a continuous porous network of
particles
supporting a volume of moisturising liquid, the gel body configured to release
the liquid by
evaporation at a predetermined rate; and a permeable layer enclosing the gel
body through
which the evaporated liquid may pass.
Use of a gel body for the provision of moisture to tobacco products has a
number of
advantages. Despite having the appearance of a jelly-like solid material, gels
are mostly
liquid. Hence, a large volume of moisturising liquid can be provided in
proportion to the
overall size of the humidifier, allowing efficient delivery of moisture. The
gel structure
accommodates the large liquid level in a way that prevents the liquid from
escaping in
liquid form; it can only be given off as vapour by evaporation. This is
particularly important
for tobacco products, which would be damaged and possibly rendered un-usable
if exposed
to liquid. Also, the gel can be engineered so as to provide a particular pre-
determined, pre-
selected rate of evaporation. The moisture release is therefore controlled in
advance, and a
humidifter can be provided that offers a chosen level of moisture release
appropriate for a
particular application. For example, a smoker who finds that his loose tobacco
has become
very dry, perhaps because he failed to close the packaging properly after the
previous use,
will want to be able to rehydrate the tobacco very quickly. A gel humidifier
with a high
evaporation rate -,Arill be suitable. Conversely, maintaining the moisture
level of pre-
packaged cigarettes between packaging and consumption demands a slow
continuous
delivery of moisture over a potentially long period, so that a low evaporation
rate
humidifter is appropriate. By varying factors such as the gel material,
structure, density,
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ratio of gel material to liquid, and possibly adding extra substances, the gel
can be tailored
to give a desired rate of evaporation.
For example, the gel body may comprise one or more alginates supporting a
volume of
moisturising liquid. Alternatively, the gel body may comprise one or more
pectins
supporting a volume of moisturising liquid. Other gel materials are not
precluded, however.
Also, the gel body may further comprise one or more modifying substances that
alter the
predetermined rate of evaporation. Additional substances can be used to
further engineer
>0 the evaporation properties beyond those that would be available from any
given pair of gel
network material and liquid. The modifying substances can be included in the
gel network
material or in the liquid, or both. For example, the one or more modifying
substances may
comprise one or more salts. The one or more salts may comprise one or more
calcium
sulphates, but other salts and/or other substance may be used.
In some embodiments, the moisturising liquid is water. This is convenient,
inexpensive and
readily available, and well-suited for moisturising tobacco.
In addition, the water may have dissolved in it one or more water-soluble
flavourants,
fragrances or additives that can be carried through the permeable layer with
the evaporated
water. This is a simple mechanism for enabling a smoker to customise his
tobacco
according to individual tastes.
A wide variety of materials and configurations can be employed for the
permeable layer.
The layer keeps the gel body separate from the tobacco so that tobacco
particles do not
adhere to the gel, and also makes for ease of handling, parricularly in the
case of a very soft
gel. The gel body is also protected from damage (to some extent at least,
depending on the
nature of the permeable layer) and is retained together in the event that it
becomes broken
into pieces. The layer may be embodied using a rigid container, for example,
or a flexible
layer or membrane, for example of plastics material or fabric. The permeable
properties
may arise from the inherent structure of the material from which the layer is
made, or can
be provided by apertures or perforations in an otherwise substantially
impermeable
material. The permeability may be in the form of microscopic pores sufficient
only to let
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the vaporised moisturising liquid pass through, or may be provided by larger
holes or
openings, since there is little possibility of liquid leaking out from the gel
body.
In some embodiments, the permeable layer may comprise a semi-permeable one-way
membrane that transmits evaporated liquid from the gel body but substantially
blocks the
passage of water vapour or liquid to the gel body. This arrangement allows the
required
moisture release from the gel to the tobacco, but prevents the gel from
absorbing moisture
back from the tobacco. This is beneficial in a situation where the humidifter
has been left in
a package of tobacco for a long time and has given up all its liquid; it is
then undesirable for
/0 the gel to take moisture away from the tobacco. Also, it prevents brown
discoloration of
the gel which can arise from absorption of moisture from tobacco, and stops
the take-up of
scents and flavours from the tobacco which would reduce the product quality.
In other embodiments, the permeable layer may comprise a material comprising a
thermo-
mechanically expanded polymer membrane having micropores that render the
material
permeable to the evaporated liquid. The polymer may comprise
polytetrafluoroethylene,
polybutylene terephthalate or polyethylene oxide, for example. Polymer
membranes of this
type are ideally suited for the transmission of moisturising vapour, while at
the same time
are robust and tough so are unlikely to burst or be punctured.
The humidifler may further comprise a removable outer layer covering the
permeable layer
that is substantially impermeable to the passage of the evaporated liquid, the
outer layer
intended to be removed before use of the humidifier. A"water-proof' outer
layer of this
type, which stops the gel from giving up its liquid, allows humidifiers to be
supplied
independently from packaged tobacco products so that a smoker can utilise one
as and
when he finds his tobacco has become dry.
Alternatively, the humidifier may further comprise an outer layer covering the
perrneable
layer that is substantially impermeable to the passage of the evaporated
liquid, the outer
layer having in it one or more apertures covered by one or more sealing
members, the
sealing member(s) being removable from the outer layer to open the aperture(s)
before use
of the humidifier. As an alternative to a removable outer layer, this
embodiment gives the
option of re-sealing the apertures once enough moisture has been released,
allowing the
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remainder to be released at a later time. It also offers further scope for
tailoring the rate of
evaporation, by the provision of larger, smaller, fewer or more apertures. As
a further
alternative, the permeable layer and the outer layer can be a single layer, so
that the
permeable layer comprises a material that is substantially impermeable, the
permeable layer
having one or more apertures therein, and the humidifier further comprising
one or more
sealing members covering the one or more apertures, the sealing member(s)
being
removable from the permeable layer to open the aperture(s) before use of the
humidifier.
A second aspect of the present invention is directed to a package for tobacco
products
/0 containing one or more tobacco products and a humidifier according to the
first aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention and to show how the same may be
carried into
effect reference is now made by way of example to the accompanying drawings in
which:
Figure 1 shows a cross-sectional view of a humidifter according to a first
embodiment of the
present invention;
Figure 2 shows a cross-sectional view of a humidifier according to a second
embodiment,
including a first example of an impermeable outer layer;
Figure 3 shows a cross-sectional view of a humidifier according to a third
embodiment,
including a second example of an impermeable outer layer; and
Figure 4 shows a cross-sectional view of a humidifier according to a fourth
embodiment.
DETAILED DESCRIPTION
Figure 1 shows a cross-sectional side view of a simple humidifier according to
an
embodiment of the present invention. The humidifier 10 comprises a gel body 12
closely
enclosed in a permeable layer 14, through which liquid held in the gel body 12
can pass as
vapour 16 once it has evaporated.
The gel body 12 is a slab of a gel material that supports a volume of
moisturising liquid,
such as water, which is suitable for moisturising tobacco. A gel is a
colloidal system in
which many particles (nanoparticles) are connected to form a continuous porous
network
that encompasses or spans a volume of liquid. The network particles can be
thought of as
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being dispersed across the liquid, or alternatively, the network supports the
liquid. This
structure gives a gel an apparently solid, albeit jelly-like appearance, but
the gel is in fact
mostly liquid in composition. Gels therefore have densities similar to
liquids, but have the
structural coherence of a solid. The liquid cannot leave the gel network by
flowing out in its
liquid form, but it can leave as a vapour via evaporation.
These properties make a gel well-suited for use in hydrating or otherwise
moisturising
tobacco products. Although a volume of liquid is present, it cannot escape as
such so there
is no risk of wetting the tobacco product. Instead, it is released to the
surrounding
environment as vapour by evaporation, which is a preferred mechanism for
increasing the
moisture content of tobacco. The high liquid content of a gel allows a
proportionally large
amount of liquid to be provided for a given size of humidifier, so that
humidifiers
according to the invention are efficient from the point of view of space. This
is important
given the relatively small size of typical tobacco pouches or tins; the smoker
will not want a
humidifier that occupies a lot of space. A gel body can also be readily made
into any shape
and size.
A further additional and very beneficial property for the hydration of tobacco
is that the
rate of moisture release by evaporation can be engineered, so that a gel body
with a
predetermined rate of moisture release can be provided. Tobacco may need
hydrating
under a variety of circumstances, so according to the present invention, a gel
can be
tailored for a specific application. For example, if a user of loose tobacco
finds that his
tobacco has become dry, it is likely that he will want to rehydrate it as
quickly as possible so
as to be able to use it. A gel body configured for a very high rate of
moisture release by
evaporation will therefore be useful, and a humidifier according to the
present invention
can be provided accordingly, of a shape and size that is convenient for
placing inside a
tobacco pouch or tin. An alternative application is the use of a humidifier to
maintain the
moisture level of packaged tobacco products between packaging and consumption.
Depending on the shelf life and the nature of the packaging, the tobacco may
become dry.
A gel humidifier that provides a very low rate of vapour release over a
sustained period can
mitigate this, if included inside the packaging when the tobacco product is
packaged. After
the packaging is opened, a smoker may like to keep a humidifier inside the
pack to keep the
moisture level relatively high. The loss of moisture from the tobacco will be
faster than
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when the packaging was still sealed, so a humidifier with a somewhat higher
evaporation
rate will be suitable. However, the moisture can be released over a shorter
period, because
the time taken to consume the contents of the pack will likely be shorter than
the time
between packaging and corisumption.
These different moisture release rates can be provided according to the
present invention
by engineering the gel body. Various properties and characteristics can be
modified to tailor
the evaporation rate. These include selection of the material comprising the
gel particle
network, the density of the gel network (for example, how tight or loose the
network is),
>0 the ratio of liquid to gel material, the size and shape of the gel body,
and the type of liquid
used.
A particularly useful group of materials for the gel network are alginates. A
single alginate
may be used, or a combination of two or more alginates may be used to further
tailor the
evaporation properties. Alginates are linear copolymers produced by various
brown algae
including seaweed (such as giant kelp) and bacteria (such as Azotobacter
species), which are
insoluble in water but absorb water quickly, and can form a gel. Alginates are
fully
biocompatible and are used in food stuffs and medicines, so they are a
particularly
attractive option for use with tobacco products, where similar health and
safety issues arise.
An alternative group of gel materials are pectins, which are similarly
biocompatible.
Other gel materials may be used, however.
A convenient liquid for inclusion in the gel body is water, since it is safe,
inexpensive,
readily available, and suitable for the moisturisation of tobacco. Other
liquids and solutions
which can provide the necessary moisture supply by evaporation from the gel
body may be
used instead, however.
If water used, it need not be plain water. The water may include one or more
water-soluble
additives that can be carried through the permeable layer by the water vapour
and hence
delivered to the tobacco. These may include flavourants and fragrances. For
example, a
moisture-releasing element containing menthol can be used to impart a menthol
flavour
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and smell to the tobacco. Vanilla, coffee and other flavours may be similarly
provided. In
this way, the consumer has a mechanism for flavouring a tobacco product with a
flavour of
their choice. The inclusion of such additives may determine the evaporation
rate to be
provided by the gel body. For example, an amount of additive sufficient to
impart its
characteristics to a typical quantity of packaged loose tobacco can be
accommodated in a
gel body so that it is given off at a suitable rate and over a suitable time
scale to adequately
modify the tobacco over a typical pack consumption period.
Additives of this type may similarly be used with non-water liquids.
Also, additives in the form of substances that modify the evaporation rate can
also be
added to the gel body. These may be added to the liquid, or to the gel network
material.
Salts can be used for example, such as calcium sulphates. An aqueous salt
solution used as
the liquid gives control over the evaporation rate. Other non-volatile liquid
ingredients may
similarly be used for the same purpose; these include glycerol (glycerine) and
propylene
glycol.
The permeable layer 14 surrounding the gel body 12 may be made from a wide
range of
materials and may have a variety of structures and configurations. Provided
that it is
sufficiently permeable so that vapour evaporated from the gel body may pass
through to
the environment surrounding the humidifier, there are few other requirements
beyond the
usual health and safety standards of the tobacco industry. The liquid-
retaining nature of the
gel body means that the permeability can be achieved by any porous structure,
from
microscopic pores that transmit water (or other liquid) vapour but not liquid
droplets, to
much larger apertures or perforations. The functions of the permeable layer,
besides the
transmission of moisturising vapour, include keeping the gel body separate
from the
tobacco (so that loose tobacco particles do not become stuck to the gel), and
facilitating
handling of the gel body, which may be difficult in the case of a soft gel
having a high
liquid content. If deemed necessary, the permeable layer may also provide some
protection
for the gel, to reduce damage or breaking up of the gel body in the event of
impacts or
rough handling.
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The outer layer may be substantially rigid, for example a box or other
container made from
metal, paper, cardboard or rigid plastics material. In such a case,
perforations or apertures
will typically be needed in the outer layer to give the necessary
permeability. Alternatively,
flexible materials may be used for the outer layer, including fabrics, gauzes
and nettings;
thin plastics materials, plus perforations if they are otherwise impermeable
to water vapour;
and permeable membranes.
A possible permeable layer material is a semi-permeable one-way membrane that
transmits
the moisturising vapour outwardly from the gel body to the surrounding
environment, but
/0 is impermeable to the passage of vapour and liquid in the opposite
direction, into the gel
body. A gel body can absorb moisture to which it is exposed. In the event that
a humidifier
is left inside a package of tobacco over a long period so that all the
moisture escapes from
the gel, it is undesirable if the gel body then begins to re-absorb moisture
from the tobacco,
thereby drying it out. A one-way membrane around the gel prevents this.
Suitable materials
include reverse osmosis membrane, such as synthetic dialysis membrane or other
food
grade pharmaceutical membrane. Further details regarding the use of one-way
membranes
in tobacco product humidifiers can be found in our co-pending application
"Disposable
humidifier for use with tobacco products", filed in the United Kingdom on the
same date
as the present application.
A further example of a suitable permeable layer is a material comprising a
thermo-
mechanically expanded polymer membrane having microscopic pores that render
the
material permeable to the evaporating vapour from the gel body. This type of
membrane
can be used alone, or laminated with a fabric. In the latter form, it is
commonly used to
make waterproof clothing, under brand names such as GORE-TEX (RTM). The
microscopic pores (micropores) are of a size to let water vapour through, but
to block the
passage of liquid water. Suitable polymers from which these membranes can be
made
include polytetrafluoroethylene, polybutylene terephthalate and polyethylene
oxide. Further
details regarding the use of these polymer membranes in humidifiers for
tobacco products
can be found in our co-pending application "Humidifying capsule for use with
tobacco
products", filed in the United Kingdom on the same date as the present
application.
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Clearly, a humidifier such as that shown in Figure 1, comprising only a gel
body and a
permeable layer, will start to give up moisture by evaporation as soon as it
is fabricated. If
the humidifier is to be quickly placed inside a package of tobacco product for
the purpose
of humidifying the product until the package is sold and opened for
consumption, such a
configuration will be satisfactory.
However, it is envisaged that humidifiers according to the present invention
will also be
supplied as separate items for a smoker to purchase and use in the event that
his tobacco
needs rehydrating, or as an item inside a packaged tobacco product for use
after the packet
/0 is opened. In these situations, it is necessary to stop evaporation from
the humidifier
before it is desired to use the humidifier.
Figure 2 shows a cross-sectional view through a humidifier according to an
embodiment
that seeks to address this issue. In this example, the humidifier 10 comprises
a gel body 12
with a permeable layer 14, as in Figure 1. Additionally, however, the
humidifier is provided
with an outer layer 18 over the permeable layer 14, that encloses the
humidifier 10. The
outer layer 18 is substantially impermeable to the passage of moisturising
vapour
evaporating from the gel body 12, so that the moisture is retained within the
humidifier 10
while the outer layer 18 is in place. However, the outer layer 18 is intended
to be removed
from the humidifier 10 before use, to allow the evaporating moisture to escape
to the
surrounding environment. The outer layer may be made from a thin flexible
plastics
material, for example. The material may be configured as a sachet, such as the
type
commonly used to provide individual portions of condiments in catering
establishments,
which can be readily torn open via serrations across the ends of the sachet.
This
arrangement provides a removable outer layer that is very simple and
economical to
implement, and which uses known packaging technology. However, other
configurations
of impermeable removable outer layer may be used if preferred.
Figure 3 shows a cross-section of a humidifter having an impermeable outer
layer according
to a further embodiment. In this example, the outer layer 18 again encloses
the permeable
layer 14 and the gel body 12, but is not intended to be removed from the
humidifier 10
before use. Instead, the outer layer 18, made from substantially impermeable
material, is
provided with one or more apertures or perforations 20. Before use of the
humidifier 10,
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these are sealed with one or more sealing members 22, which are adhered over
the
apertures 20 to render the outer layer 18 impermeable. The sealing members 22
are then
removed by peeling from the outer layer 18, to open the apertures 20 and allow
the escape
of moisturising vapour therethrough. The sealing members 22 may be provided
with
protruding pull tabs 24 to facilitate removal from the outer layer 18. If the
sealing members
22 are adhered to the outer layer 18 using re-usable adhesive, they can be
reapplied to cover
the apertures when enough moisture has been obtained from the humidifier 10.
Liquid
remaining inside the gel body can thereby be retained for future uses of the
humidifier.
Alternatively, the sealing members may be disposable, allowing a single use of
the
>0 humidifier only. Furthermore, if more than one sealing member is provided,
the user can
decide ho`v many to remove and therefore how many apertures to open, so that
the user
has a degree of control over the amount of moisture released.
In a still further alternative, the permeable layer and the impermeable outer
layer may be
combined. The permeable layer may be made from a substantially impermeable
material,
and made permeable by a number of apertures or perforations, as discussed
above. If the
apertures are provided in only part of the permeable layer (rather than a
continuous array
of perforations, for example), the apertures may be closed by removable
sealing members
(which may or may not be replaceable) such as those described with respect to
Figure 3. In
this way, the additional advantages of an impermeable outer layer for
maintaining the
humidifier for use at some future time can be implemented in a particularly
simple manner.
Figure 4 shows a cross-sectional view of a humidifier according to this
embodiment. The
humidifier 10 comprises a gel body 12 enclosed in a permeable layer 14 as in
the previous
examples. The permeable layer 18, made from substantially impermeable
material, has a
series of apertures 20 in one side, which are covered by a removable sealing
member 22
having a pull tab 24.
Humidifiers according to the present invention may include additional features
in various
combinations with the features described. For example, the humidifier may
further
comprise a sealed compartment containing a supercoolable salt hydrate solution
that can be
activated to crystallise and release heat to the gel body, thereby increasing
the rate of
moisture release by evaporation. Humidifiers comprising such heat-releasing
elements are
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described in our co-pending application GB 0710776.6 "Heatable humidifying
device for
use with tobacco products", filed in the United Kingdom on 5th June 2007.
