Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to improved aseptic packaging and aseptically packed
products and, in particular, to improved aseptic packaging of products
which are packed in films in the form of sausages but it can also relate to
products packed in film packages of any other configuration.
In present aseptic packaging methods there are three areas in which the
integrity of the package can break down.
In the first of these, if the film or foil, hereinafter called film, is not
impervious to the transmission of micro-organisms, oxygen, other gases or
water vapour, then there can be degradation of the product by transmission
through the film. For ease in this specification we will refer generally to
micro-organisms and such reference is considered to relate to other things
which ean pass through the film and which can degrade the product.
In practice, this has normally been overcome, and generally quite
satisfactorily, by using a composite film which may preferably have two
parent components of a polyester, which may satisfactorily be
polypropylene, which are adhesively secured. Generally each of the parent
materials has a very thin layer of an impervious material coated thereon,
and in many cases this material may be polyvinylidene chloride, and at
least one of the layers may also have a film of a metal, such as aluminium
vacuum deposited thereon.
Such films do provide a good barrier to micro-organisms but, where they
are to be connected, such as along a longitudinal seam, if a cylindrical
package is being formed, or about the periphery of a differently shaped
- package, connection is normally by means of heat welding. The weld is
made between two very thin layers of PV~C and this can cause the second
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area of difficulty which is encountered in that the PVDC layer can partially
separate from its parent layer and the weld may thus not be
microbiologically continuous.
Also, physically, it may be that the weld can break if the package is
distorted as by being dropped.
Further, as PVDC is relatively non-elastic, if there is physical distortion of
the package, as when a package is dropped, then the PVDC tends to split
and the whole package can split and, not only is the integrity of the
package destroyed, the contents may spill. Such packages are generally,
not acceptable to distributors and retailers.
A further area where there have been difficulties with such packages,
particularly when they are in the form of cylinders, has to do with the
closing of the cylinders.
Normally during formation the filled cylinder, where it is to form the ends
of adjacent packages, is compressed and a pair of metallic clips are passed
around the compreæed cylinder and are deformed to draw the package
closed and, after the clips have been closed, the packages are severed
between the clips.~
Because the film is bunched beneath the clip it is possible that there can be
2 0 a path through the seal to perm it degradation of the contents of the
package. Also, because the clips are simply crimped, it is possible that,
on physical mishandling of the package, there can be deformation of the
clip which can destroy the integrity of the package.
The invention has a combination of objects which are designed to
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overcome, or at least minimise, the disadvantages set out hereinbefore.
In a first aspect of the invention I provide a new form of film for aseptic
packaging which film has outer layers of a flexible plastics material and,
sandwiched between these, a material which is impervious to micr~
organisms.
Preferably the impervious layer comprises a layer of a polyester material
and a layer of metal is located adjacent the polyester layer.
The layer of metal, which is preferably aluminium, is preferably deposited
on the layer of thermoplastics material but it may be desposited on one of
the layers of a flexible plastics material before the layer of polyester
material is jointed to the flexible plastics material, either during a
coextrusion process or an adhesive securing process.
In a second aspect of the invention I provide an improved method of sealing
in manufacturing packages from film wherein the layers in contact and
between which the seal is made are of the same material.
Where a lap seal is used, the film has, on both surfaces, a layer of the same
material.
I may also provide an improved method of sealing means in manufacturing
packages from films which includes an adhesive seal which, together with a
heat seQl~ provide a seal which is both mechanically strong as well as being
impervious to micro-organisms.
In a still further aspect of the invention I provide an improved way of
sealing the ends of a cylindrical package in which an adhesive is introduced
into the area where the clip, which can be deformed to seal the end, is to
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be located, which adhesive provides a plug at the end of
the closure which fills the interstices of the material
forming the package.
In a broad aspect, therefore, the present invention relates
to a method of continuously forming and filling aseptic
packages from a film which has outer layers of a flexible
plastic material having sandwiched therebetween a material
that is impervious to microorganisms, said method
comprising forming a continuous substantially cylindrical
package from the film with adjacent edges thereof being in
contact to form a cylinder, heat sealing said adjacent
edges of the film with the plastic materials of the
adjacent edges which are sealed together being the same,
filling the cylinder, after formation thereof and heat
sealing of the adjacent edges thereof, to form a filled
cylinder, locating an adhesive in the cylinder at positions
where the cylinder is to be divided into individual
packages, compressing the filled cylinder at the positions
of the adhesive, placing two clips about the positions of
the adhesive after compression thereof and tightening the
clips such that as the clips are tightened the adhesive
flows to occupy any interstices in the film which are
formed during the compression to thereby provide a plug
between the clips, and separating the cylinder between the
clips into individual packages.
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In order that the various aspects of the invention may be
more readily understood, I shall describe the invention as
applied to a cylindrical package of a foodstuff, although
it is to be understood that the invention is equally
applicable to packages of other shapes.
The package is illustrated in the accompanying drawings, in
which:-
Fig. 1 is a longitudinal sectional view showing the
arrangement of the foodstuff package;
Fig. 2 is an enlarged view at 2 of Fig. 1 showing
the constituents of the film;
Fig. 3 is a partial view along line 3-3 of Fig. 1
showing a form of lap joint;
Fig. 4 is a Figure similar to Fig. 3 showing a fin
joint before this is turned over against the
package;
Fig. 5 is a view similar to that of Fig. 3 but
showing the addition of an adhesive which
aids the mechanical stability of the
package; and
Fig. 6 is an end view of the package showing the
location of the adhesive plug the area where
the package is sealed.
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Referring initially to the formation of the film, this comprises a central
polyester layer 10, a deposited metal film 11 and two outer layers 12, 13 of
a flexible plastics material, preferably polyethylene.
Whilst the layers 10, 12 and 13 may not be completely impervious to the
transmission of micro-organisms, oxygen, other gasses or water vapour, the
imperviability is provided by the metal film 11.
Preferably this is a film of aluminium which is deposited on the central
polyester film 10 prior to the location of the outer films 12, 13 thereover,
the outer films being formed either by coextrusion or adhesive securing to
the central film.
The deposited layer 11 can be very thin, whilst giving a complete coverage
and complete imperviability, but, at the same time, is very flexible, as will
be discussed hereinafter. Preferably the deposited layer can be printed to
provide an attractive pack for the product.
The outer layers are preferably of linear low density polythene and these
may have additives, known in the packaging art, for example to increase
clarity and for other purposes.
The film of the invention is basically made of very thin layers and an
exemplification could be that the central layer 10 of polyester may be 10
~um thick; the deposited film 11 may be of aluminium and may be of 1-2 11m
thick; and the outer layers 12, 13 may of a linear low density polyethylene
and may be 30 ~um thick, giving a total thickness of the order of 72-75 ~um
when the securement of the layers is considered. We have found a film of
this thickness gives a good package integrity, including a good feel.
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This is distinguished from the films which are used in non-aseptic packaging
processes, normally called retort packaging, in which the product is
initially hermetically sealed within the package snd then goes through a
retorting process which cooks the product and, at the same time, destroys
any micro-organisms which are within the package.
It will be appreciated that, physically, the packaging for such products
must be strong, and any seals must be extensive, as there is a substantial
increase in pressure within the package during the retorting process.
Also, very often, an aluminium foil is incorporated in the packaging
material which adds to the expense and, as indicated herein, is
unsatisfactory for an aseptic package where the ends of the package are
drawn together and crimped, as the aluminium tends to pinhole or crack.
If deposited aluminium is used, this can degrade at retorting temperatures.
Further, such films need to use adhesives which are stable at temperatures
of the order of 120C, whereas, using my process, stability to the order of
80C is all that is required.
With my package, on the other hand, the product, whilst it is fed to the
package hot, has been sterilised during the cooking procedure and the
filling process is aseptic so that there is no contamination introduced
during this procedure and post filling treatment is not required.
It is for this reason that I can use films which are, over all, very much
thinner, and thus cheaper, than the films used in retort packages.
The film of the present invention has substantial advantages over previous
films, and particularly those which included layers of PVDC, which is a
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relatively non-elastic material.
The film of the present invention, as a whole, has a high degree of
elasticity and, thus, it can accept substantial physical mishandling without
damage.
By using the film of the invention,even a relatively heavy package will not
be damaged by being dropped, for example, onto a floor from a substantial
height. The package is sufficiently resilient to absorb such treatment
without damage~
This is, of course, important from a sales point of view. The main
competitive forms of packaging for the type of foodstuffs to which this
invention relates are canned packages or retort packages.
Canning is basically expensive, because of the cost of the can and the cost
in sealing the can and9 for some products, is not completely satisfactory as
the products are treated under high temperatures and pressures to destroy
micro-organisms. On the other hand, physically, a can is a very
satisfactory method of storing products as cans are strong, but cans can be
badly distorted if dropped from a height and can be pierced on striking a
sharp object, although this is unusual.
Retort packaging suffers from a disadvantage similar to cans in that the
2 o product is treated to high temperatures and pressures, often to its
detriment, and, generally, retort packages tend to be damaged if, say,
dropped onto a surface from a height.
Also, as discuæed earlier, the films used for retort packaging are relatively
expensive because they are thick.
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The film of the invention thus has substantial advantages over both these
previously used forms of packaging whilst having only minor disadvantages.
Referring now to Figs. 3 and 5, I show means whereby the longitudinal seal
of a package can be made.
Fig. 3 shows the most usual type of seal, a lap seal, and it will be seen that
the outer layer 13 along one edge of the film is in contact with the inner
layer 12 along the other edge of the film and it is these two layers which
are connected together.
As previously explained, these layers are of a similar material, in the
specific example, polyethylene, and it is thus possible to make a good and
continuous seal between these layers thus preventing ingress of micro-
organisms or other deleterious gaæes into contact with the food contained
in the package.
Also, as each of these films can be strongly laminated to the central layer
10, there is no likelihood of delamination when the seal is made and thus a
good and coherent package is formed.
The example of Fig. 4 is somewhat different as, in this case, the abutting
surfaces, which form 8 fin 15, are both the inner layer 12. This, of course,
ensures, once again, a good seal being achieved but this arrangement can be
used where the inner and outer layers are of different m~terial.
In the form of arrangement shown in Fig. 4, there would normally be
another step in the formation of the cylindrical package, that is by turning
- the fin lS to one side and then securing it to the surface of the package.
Fig. S, as explained, is a view similar to that of Fig. 3 but, in this case, I
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also provide an adhesive material 16 at the edge of the lap joint, which
material can assist in aiding the mechanical integrity of the seal as well as
adding an additional barrier to the passage of micro-organisms.
A third aspect of my invention is basically directed to the end seals 20 of
cylindrical packages and will be described as so directed but it will be
understood that it can be applied to different forms of packages.
In the manufacture of a product which is aseptically packaged in film, the
film, either in the form of a cylinder or in the form of a sheet which is
formed into a cylinder, is filled continuously with a material and where the
individual packages are to be formed, means are provided to compress the
cylinder thus, basically, removing the material being packaged from the
area and when comp~ession is completed, deformable clips 21 are placed
about the package at two spaced positions, which clips effect the sealing of
the ends of the packages and, after location, the material 22 between the
clips is severed.
Conventionally, the clips 21 used were of aluminium, as being a metal
which is relatively easy to deform, but I prefer to use steel clips which,
although more difficult to deform, once they are deformed, tend to retain
their deformed condition and are unlikely to be displaced.
In the sealing of the ends, it will be appreciated that the film is bunched
whilst the foodstuff in the package is displaced and, provided the final
compression is sufficient, there should be no voids through the seal.
~owever, because of this bunching, there is always a possibility that a
passage sufficient for the passage of micro-organisms can be left in the
sealed end.
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In order to overcome this, I prefer to locate, at the position at which the
sefll is to be maintained, an adhesive material, which may be a micro-
crystalline wax or some form of silicone adhesive, which material, on
compression, flows to fill any interstices which are left in the package and
to, thus, increase the integrity of the seal.
The wax or adhesive should have properties of a good tack, to adhere to the
film, be solvent free, plastic at the clipping stage, be compatible with food
and be of relatively low cost. Two suitable materials are those sold under
the trade marks "Ultraflex Amber" and "Microflex".
This adhesive may be applied to the film as it is passing along its path to
the position where it is formed into the package and, preferably, the
adhesive sets so that it retains its position on the film during movement.
When the actual closing step takes place, as the clip is tightened, the
adhesive is caused to flow into any interstices in the film and fill these. It
may be preferred that the adhesive softens or melts, at least to a certain
degree, when heated by the product which is in contact with the adhesive,
to aid this ~low.
When the product cools, the adhesive sets to iorm a plug which provides a
barrier to the passage of micro-organisms.
The adhesive is selected so that it is inert to foodstuffs and does not
attract foodstuff to its surface, although this is not critical as the package
is normally opened by removing the end inside the clip and the adhesive
would normally be discarded with the end of the package and the clip.
It will be seen that the adhesive not only provides a physical barrier for
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micro-organisms and other deleterious substances, but, also, can act to
physically strengthen the package at its ends.
It will be seen that the use of the various aspects of the invention in
aseptic packaging does provide a package which is more successful than
previously proposed packages and, at the same time, provides a package
which can permit satisfactory packaging of products at a price which can
be substantially less than competitive packages.
It will be appreciated thst the different aspects described herein do not
have to all be used in a particular packaging arrangement, they can be
selectively used as required.
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