FLEXIBLE POUCHES AND BAGS

SACHETS ET SACS SOUPLES

English Abstract

ABSTRACT OF THE DISCLOSURE
There is disclosed a flexible pouch comprising a
laminate of two layers of heat-sealable thermoplastic
plastics sheet material permanently adherent in face to
face relationship, the materials of the said two layers
having different melting points and having limited
compatability with each other. The pouch is heat-sealed,
where it will require to be opened, at a line or lines of
contact between a surface of one of the thermoplastics
materials and a surface of the other of those materials
which may be polyethylene materials. At least one of the
two layers may have a vacuum-metallised surface.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flexible pouch comprising a laminate consisting of two
layers of heat-sealable thermoplastic plastics sheet material
which are permanently adherent to each other in face to face
relationship, the materials of the said two layers having
different melting points and having limited compatibility with
each other, and the pouch being heat-sealed, where it will
require to be opened, at a line or lines of contact between a
surface of one of the thermoplastics materials and a surface
of the other of those materials.


2. A pouch according to claim 1, wherein the said two layers
are of polyolefin materials.


3. A pouch according to claim 1, wherein at least one of the
said two layers has a vacuum-metallised surface.


4. A pouch according to claim 1, wherein the said two layers
are of polyethylene materials.

Description

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FLEXIBLE POUCHES AND BAGS
This invention concerns improvements relating to flexible
pouches and bags, hereinafter referred to as pouches, and is
concerned with improvements upon or modifications of pouches
described and claimed in the Specification of Canadian Patent
No. 935,790.
In that patent, a flexible pouch is claimed comprising two
layers of heat-sealable thermoplastic plastics materials
adherent to opposite surfaces of a layer of metal foil, the
materials of the said two layers having different melting
points and having limited compatibility with each other and the
pouch being sealed, where it will require to be opened, at a
line or lines of contact between surfaces of different layers
of the plastics materials. Limited compatibility is defined
as meaning compatibility such that seals produced between
surfaces of the two materials on melting the surfaces under
predetermined conditions of temperature, time and pressure are,
although hermetic, capable of being peeled open. Also in the
present specification and claims, the term limited compatibility
is used with the meaning so defined.
The present invention seeks to provide improvements offering
additional advantages of versatility, practical utility and, in
`some cases, reduction of cost.
According to the invention, a flexible pouch comprises a
laminate consisting of two layers of heat-sealable thermoplastic
plastics sheet material which are permanently adherent to each
other in face to face relationship, the materials of the said
two layers having different melting points and having limited
compatibility with each other (as hereinbefore defined), and the
pouch being heat-sealed, where it will require to be opened, at
a line or lines of contact between a surface of one of the
thermoplastics materials and a surface of the other of those

materials.
The two layers of thermoplastics materials are thus
laminated without an intermediate layer of sheet material.


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The layers of thermoplastics materials of limited
compatibility may be polyolefin materials having different
melting points, a difference within the range of 5 to 50C
being appropriate in the case of polyethylene materials.
Suitably, the material forming the outside of the pouch will
have a higher melting point.
The conformation and manner of production of the pouch
may be as described and illustrated in our aforesaid
Specification.
Ways-ofcarrying the invention into effect will now be
more fully described by way of example:
A sheet material was prepared which consisted of two
adhering plies of polyethylene film of different melt range,
for example, plies 50 micron thick, one having a melting
range of 100-105C and the other a melting range of 105-125C,
the material of the layer forming the outside of the pouch
having a higher melting point than that of the inner layer.
From this material a pouch was produced, the conformation
of the blank and the manner of production being as described
and illustrated in the aforesaid Specification. Thus the
pouch possessed a seal which, although hermetic, was capable
of being peeled open.
Such a pouch possessed effective barrier properties.
If of transparent material, it allows the contents to be
clearly seen. Due to the flexibility of the pouch, possible
danger of damage during storage and transit are reduced, and
the pouch has a good appearance and a soft feel. Deformation
and loss of appearance when the contents are packaged under
reduced air pressure are avoided. Finally a reduction in
cost can be achieved. Either ply or both plies may be
matallised. For example, the outer ply of higher melting

temperature may be vacuum-metallised with aluminium on its
inner surfaces only to give an optical density reading of 3-4.


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Such a metallised ply affords good barrier properties and
neat appearance. An inner surface may be printed. Either
or both plies may be printed.
For some purposes, the metallisation may be dispensed
with, the two plies of polyethylene materials being simply
laminated together. The polyethylene materials may be as
described above. A pouch produced from this sheet material
can be given good flexibility at low cost. In the production
of the laminate, the components may be wound upon a reel
unlaminated and may be sealed together at the edges and/or
laminated when required. Further cost can thereby be saved.