Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02302329 2000-02-29
WO 99/11540 PCT/US98/16965
DETERGENT TABLETS-PACKAGE COMBINATION
Technical Field
The present invention relates to a packaging system for a stack of tablets
containing a bleaching agent.
Bac~C~around of the Invention
Packaging systems for stacks of tablets are widely used in food industry. Such
packaging systems often take the form of a wrapper, sometimes a shrinkable
wrapper, because such packaging systems are relatively easy to process at
high speed and in large quantities. Because tablets are normally adapted so as
to correspond to a basic consumer unit, the tablets are normally used the one
after the other, and not all at once. In order to protect the remaining
tablets after
the first opening of the packaging system and up to use of the complete stack,
it
is often preferred to have the stack of tablets contained in a packaging
system
comprising re-closing means.
The present invention concerns a packaged product comprising the combination
of a stack of tablets with a packaging system containing the stack of tablets,
whereby the packaging system comprises re-closing means. Such a packaging
system is known from W092I20593 published on the 7"' of November 1992 for
food product.
Among the advantages of such packaging systems is the fact that they are air-
tight when closed, which is particularly adapted for packaging food products
which are very sensitive to oxygen. Further, these pac~Caging systems can be
repeatedly re-closed.
However, air-tight packaging systems for food product are not adapted to
packaging of chemical compositions, such as a bleaching agent. Indeed, if such
materials are packed in an air tight packaging system, the gas may be released
within the package without being evacuated, thus deforming the packaging
system and, in extreme cases, leading to explosion of the packaging system, as
the content may release gas.
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2
The invention seeks to provide a packaged product of the above mentioned kind
which
can protect tablets comprising chemical compositions which may also release
gas.
Summary of the Invention
In accordance with the invention, this object is accomplished with a packaged
product
comprising the combination of a stack of tablets (1 ) with a packaging system
containing
the stack of tablets (1 ), wherein the packaging system comprises re-closing
means, the
tablets comprise a bleaching agent and the packaging system is formed from a
material
(2) having a Moisture Vapour Transfer Rate of less than 20g/m2/day measured at
40°C
and 75% Equilibrium Relative Humidity and further wherein the packaging system
comprises at least a micro-hole, the material having sufficient resiliency
that the micro-
hole is closed when pressure outside the product equals that inside the
product, but
which opens when pressure inside the product exceeds that outside the product.
Detailed Description of the Invention
A packaged product in accordance with the invention has a number of
advantages.
Since the material forming the packaging system has a Moisture Vapour Transfer
Rate
(MVTR) of less than 20g/m2/day, the ingress of water in the packaging system
is limited,
so that the stability of the bleaching agent can be maintained. Indeed, a
bleaching agent
is very sensitive to humidity, so that it decomposes in a humid environment.
Furthermore, a bleaching agent may release gas. Gas release would be
accelerated in
a high temperature environment. Since the material forming the packaging
system may
have a micro-hole, gas would be evacuated out of the packaging system if
pressure
builds up within the packaging system, whereas gas transfer is very limited
when the
pressure inside the packaging system is in equilibrium with the external
pressure.
Indeed, a micro-hole is such that it will give way significantly only in case
of a pressure
gradient between the two sides of the hole. This is due to the resilience of
the packing
material. This is particularly adapted when combined with the package for the
invention
because the pressure gradient is normally such that pressure
CA 02302329 2005-02-10
2a
inside the package is always at least equal to the external pressure, so that
water does
not have any substantial access to the inside of the package, whereas gas
release will
be controlled. Consequently, such a packaged product would not induce a risk
of
explosion while efficiently protecting the tablets from decomposing.
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WO 99111540 PCTNS98/16965
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The invention will now be described by way of example and with reference to
the accompanying drawings in which:
Figure 1 is a perspective view of a flat film with a stack of tablets prior to
wrapping.
Figure 2 is a perspective view of a stack of tablets in a sealed film.
Figure 3 is a perspective view of a stack of tablet in an over~wrapped film.
Figure 4 is a perspective view of a stack of tablets in a flow-wrapped film.
Figure 5 is an elevation view of a packaging system according to the present
invention.
The packaged product of the invention relates to a stack of tablets (1 ).
Tablets
are portions which may have various cross sections. The cross section is
normally circular, but it may be rectangular, square or elliptical for
example.
Tablets can be grouped into a stack (1 ) by stacking them along their axis,
thus
forming a stack which has a shape having the same cross section than a tablet.
A stack according to the invention may comprise two or more tablets,
preferably
2 to 10 tablets, more preferably 5 or 6 tablets.
The tablets of the invention comprise a bleaching agent. Typically, the
bleaching agent will be an inorganic per-hydrate bleach. Such bleaching agents
comprise sodium per-borate, which may be in the form of the mono-hydrate or of
the tetra-hydrate. Other per-hydrate salts can also be used, such as sodium
per-carbonate. Such components are a useful source of carbonate ions for
detergency purposes. However, such per-carbonates are particularly unstable
in moisture and also release gas, such as oxygen. Therefore, the packaging
system should be suitable so as to take account of these two features.
Because a bleaching agent is decomposing in moisture and consequently
loosing its bleaching properties, it is important to protect the tablets from
ingress
of external moisture. Ideally, this could be achieved by packing each tablet
in a
separate package to open just prior to use, the package being completely water-
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4
impermeable. However, such an option is not environmentally friendly as it is
maximising the number of packages used. 4n the other side of the range, the
tablets could be delivered in only one bag, however, first opening of the bag
would expose all tablets to the external environment. A compromise is
preferable by grouping the tablets in relatively small numbers in a package in
the form of a stack, in order to minimise the room occupied by the tablets, to
reduce the number of packages and to minimise the exposition of tablets
remaining in the once opened bag. In order to protect the tablet or tablets
remaining in the packaging system after first opening, the packaging system
can
be re-closed. In order to achieve efficient protection of the tablets, it is
needed
that the packaging system has a limited Moisture Vapour Transfer Rate
(MVTR). The MVTR of the packaging system is measured at 40°C and 75%
eRH, which corresponds to a environment particularly damaging for the tablets.
It was found that the MVTR should not exceed 20 g/m2/day in order to fulfil
the
requirements of the packaging system, corresponding to a protection effective
for a six month period in real conditions. This protection is achieved prior
to the
first opening of the packaging system, indeed each further opening is
potentially
introducing moisture within the package, so that protection may not last for
as
long a time once the packaging system has been opened for the first time. This
feature is used for choosing the number of tablets which compose a stack.
The packaging system should also take account of the fact that gas is released
by its content. This may be achieved by a micro-hole which is made in the
packaging system. A micro-hole would act as a communication between the
inside of the packaging system and the outside of the packaging system. The
main characteristics of a micro-hole is that the communication it provides is
pressure sensitive. Indeed, if the pressure inside of the packaging system and
the pressure outside of the packaging system are in equilibrium, the micro-
hole
will have a negligible influence on the transmission characteristics of the
packaging system because of the resilience of the material. indeed, no
sign~cant amount of the material is taken away when making a micro-hole, so
that it will be substantially closed in the absence of a pressure gradient
between
the inside and the outside of the bag. However, once a pressure gradient
appears, the packaging system will be slightly distorted, so that the micro-
hole
will open itself and allow significant communication between the outside and
the
inside of the package in order to minimise the pressure gradient. This is
CA 02302329 2003-05-05
particularly adapted when combined with the invention. Indeed, when a
pressure gradient is created, it is usually because the pressure inside the
bag
increases, as the external pressure is substantially a constant. This means
that
in case of release of a gas, the inner pressure will increase, thus creating a
pressure gradient which will open the micro-hole, through which the excess of
gas will be evacuated. The micro-hole is acting as a discharge orifice without
letting moisture enter the bag in a significant manner as the external
pressure is
normally always lower or equal to the inner pressure. This mechanism can be
tuned by using various sizes for the micro-holes as well as by choosing the
number of micro-holes needed per packaging system, taking account of the
composition and of the quantity of the content of the packaging system, and
taking also account of the MVTR of the packaging system. Indeed, a non zero
MVTR will allow some communication between the inside and the outside of the
bag.
In a preferred embodiment of the present invention, the stack (1 ) is composed
of
five cylindrical tablets having a circular cross section. The tablets comprise
a
bleaching agent, and may also comprise other components such as fragrance,
surfactants, enzymes, detergent etc.... Typical tablet compositions for the
preferred embodiment of the present invention are disclosed in the pending
European published applications of the Applicant n° 846,755,
846,798,
846,756 and 846,754 for example. It should be mentioned that the
fragrance is usually composed of a particularly volatile composition, so that
a
low MVTR prevents not only ingress of water but egress of perfume.
The packaging system of the preferred embodiment is originally composed of a
sheet of material (2) having the required MVTR. Materials suitable for this
use
include mono-layer, co-extruded or laminated films. Such films may comprise
various components, such as poly-ethylene, poly-propylene, poly-styrene, poly-
ethylene-terephtalate. In a most preferred embodiment of the invention, the
packaging system is composed of a poly-ethylene and bi-oriented-poly-
propylene co-extruded film with an MVTR of less than 1 gldaylm2. The MVTR of
the packaging system is preferably of less than 10 glday/m2, more preferably
of
less than 5 g/daylm2, even more preferably of less than 1 g/daylm2 and most
preferably of less than 0.5 gldaylm2. The film (2) may have various
thicknesses.
The thickness should typically be between 10 and 150 wm, preferably between
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WO 99/11540 PCT/US98/16965
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15 and 120 wm, more preferably between 20 and 100 hem, even more preferably
between 25 and 80 pm and most preferably between 30 and 40 Vim.
The packaging system preferably comprises at least a micro-hole. There may
also be more than 1 micxo-hole. Preferably, there is between 1 and 10 micxo-
holes per packaging system, more preferably between 2 and 8 micro-holes,
even more preferably between 2 and 5 micxo-holes and most preferably 3 micro-
holes. These micro-holes can be made using a pin. In the preferred embodiment
of the present invention, the pin used has a 1 mm diameter, the head having a
diameter of the order of 0.1 mm. The packaging system may be pinned prior to
wrapping, for example using pins fixed onto a cylinder which rotates while the
film roll passes to apply the micro-holes. Such micro-holes have a size of
typically between 1 ~ and 1000 Vim, preferably between 250 and 900 Vim, more
preferably between 350 and 700 wm and most preferably between 400 and 500
Nm. An advantage of using a micro-hole in combination with a material having
the claimed MVTR is that the problem of the ingress of moisture and the
problem of evacuation of gas is de-coupled. Indeed, ingress of moisture is
readily controlled by choosing the appropriate MVTR, whereas a microfiole has
only a negligible influence on ingress of moisture because it is present only
at
some points on the packaging system without modifying the characteristics of
the remaining surface of the packaging system and a micro-hole will not have a
sign~cant influence if there is no pressure gradient. As a pressure gradient
will
appear precisely when gas needs to be evacuated to prevent deformation of the
packaging system, the micro-hole will fulfil its function without significant
influence on the ingress of moisture.
The stack of tablets can be wrapped after being deposed onto the packaging
system. The packing method used are typically the wrapping methods disclosed
in W092I20593, including flow wrapping (Fig. 4) or over wrapping (Fig. 3).
This
document is included as a reference for the present invention. When using such
processes, a first longitudinal seal is provided (3), which may be a fin seal
or an
overlapping seal, after which a first end (4) of the packaging system is
closed,
followed by closure of the second end (5). The re-closing means may also
comprise means as described in W092I20593. In particular, using a twist, a
cold seal or an adhesive is particularly suited to the packaging system of the
present invention. Indeed, a band of cold seal or a band of adhesive may be
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WO 99/11540 PCTNS98/16965
7
applied to the surface of the packaging system at a position adjacent to the
second end of the packaging system, so that this band may provide both the
initial seal and re-closure of the packaging system. In such a case the
adhesive
or cold seal band may correspond to a region having a cohesive surface, i.e. a
surface which will adhere only to another cohesive surface. Such re-closing
means may also comprise spacers which will prevent unwanted adhesion. Suds
spacers are described in WO 95/13225, published on the 18'" of May 1995.
There may also be a plurality of spacers and a plurality of strips of adhesive
material. The main requirement is that the communication between the exterior
and the interior of the package should be minimal, even after first opening of
the
packaging system: In a preferred embodiment of the present invention, a cold
seal is used, and in particular a grid of cold seal, whereby the cold seal is
adapted so as to facilitate opening of the packaging system. .
Preferably, the tablets of the invention are containing a detergent
composition.
Protection against moisture is an issue which is more acute for detergent
tablets
than for usual detergent powders. Indeed, when exposed to moisture, a first
effect on detergent compositions is to soften its structure and consistency.
This
change in consistency of the detergent composition due to moisture does not
always have significant consequences on the chemical properties of the
detergent. However, a change in structure will be significant for the tablets
because they are likely to break, thus making use awkward and unpleasant.
However, this does not apply to powders in a granular form as dosing is made
by scooping the powder.
