U.S. patent application number 12/993986 was filed with the patent office on 2011-11-03 for gas barrier and liquid absorbent container for the packaging of food products.
This patent application is currently assigned to VITTEMBAL SOCIETE INDUSTRIELLE. Invention is credited to Phillippe Baldet, Stefano Capitani, Eugenio Longo, Jvanohe Rizzi.
Application Number | 20110266168 12/993986 |
Document ID | / |
Family ID | 39884501 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110266168 |
Kind Code |
A1 |
Longo; Eugenio ; et
al. |
November 3, 2011 |
GAS BARRIER AND LIQUID ABSORBENT CONTAINER FOR THE PACKAGING OF
FOOD PRODUCTS
Abstract
The present invention relates to a gas barrier and liquid
absorbent container (1) for use in the modified atmosphere
packaging of food products which tend to release liquids. The
container of the invention comprises a base and upwardly extending
side walls terminating in a continuous flange horizontally
projecting from the side walls, and comprising an inner part of a
liquid pervious material (20), and an outer part of a liquid and
gas barrier material (10), said inner and outer parts being joined
together at the side walls and being spaced apart from each other
at the base to define an interspace (30). A circumferentially
extending continuous portion (11) of the surface of the liquid and
gas barrier material is exposed to provide an area for a gas
barrier closing lid to be sealed. The invention further relates to
a method of manufacture of said container, to its use in the
packaging of food products under a modified atmosphere and to the
gas-tight packages thus obtained.
Inventors: |
Longo; Eugenio; (Rho,
IT) ; Baldet; Phillippe; (Collias, FR) ;
Rizzi; Jvanohe; (Legnano, IT) ; Capitani;
Stefano; (Como, IT) |
Assignee: |
VITTEMBAL SOCIETE
INDUSTRIELLE
Remoulins
SC
CRYOVAC, INC.
Duncan
|
Family ID: |
39884501 |
Appl. No.: |
12/993986 |
Filed: |
April 29, 2009 |
PCT Filed: |
April 29, 2009 |
PCT NO: |
PCT/EP2009/055175 |
371 Date: |
March 1, 2011 |
Current U.S.
Class: |
206/204 ; 53/423;
53/432 |
Current CPC
Class: |
B65D 81/262
20130101 |
Class at
Publication: |
206/204 ; 53/423;
53/432 |
International
Class: |
B65D 81/26 20060101
B65D081/26; B65B 31/02 20060101 B65B031/02; B65B 25/00 20060101
B65B025/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2008 |
EP |
08290480.6 |
Claims
1. A container for the packaging of food products comprising a
first part made of a liquid and gas barrier material comprising a
base and upwardly extending side walls terminating in a continuous
flange outwardly projecting from said side walls said flange being
provided with an upper surface and a lower surface, a second part
made of a liquid pervious material, comprising a base and upwardly
extending side walls optionally terminating in a flange outwardly
projecting from said side walls, said second part being coaxially
positioned into said first part in such a way that the bases of
said first and second parts are spaced apart from each other to
define an interspace and said first and second parts are joined
together at the side walls and, when a flange is present in said
second part, at the flanges provided that a circumferentially
extending continuous portion of said upper surface of the flange of
the liquid and gas barrier material is exposed to provide an area
for a closing lid to be sealed to the container.
2. The container according to claim 1 wherein no flange is present
in said second part and said first and second parts are joined
together only at the side walls.
3. The container according to any preceding claim wherein the
liquid pervious material is a thermoplastic material provided with
one or more perforations.
4. The container according to any preceding claim wherein the
liquid pervious material comprises a foamed material.
5. The container according to any preceding claim wherein the
liquid and gas barrier material of said first part is a multilayer
material comprising a structural layer, a gas barrier layer and a
heat-sealable layer.
6. The container according to any preceding claim comprising a
first part made of a liquid and gas barrier material comprising a
structural layer of foamed polystyrene, a gas barrier layer and a
heat-sealable layer and a second part made of a thermoplastic
material comprising a foamed polystyrene layer provided with one or
more perforations.
7. The container according to claim 6 wherein said second part is
made of a material further comprising an adhesive layer positioned
on the side of said second part facing said first part and wherein
said adhesive layer comprises a blend of high impact polystyrene
and styrene-butadiene-styrene block copolymer.
8. The container according to any one of claims 1 to 4 comprising a
first part made of a liquid and gas barrier material comprising a
structural layer of foamed poly(lactic acid) and a second part made
of a thermoplastic material comprising a foamed poly(lactic acid)
layer provided with one or more perforations.
9. A method of producing a container of any one of claims 1 to 8
comprising the steps of: forming a first part made of a liquid and
gas barrier material, said first part comprising a base and
upwardly extending side walls terminating in a continuous flange
outwardly projecting from said side walls, said flange being
provided with an upper surface and a lower surface; forming a
second part made of a liquid pervious material, said second part
comprising a base and upwardly extending side walls optionally
terminating in a flange outwardly projecting from said side walls;
bringing said second part coaxially into said first part in such a
way that the bases of said first and second parts are spaced apart
from each other to define an interspace and said first and second
parts are joined together at the side walls and, when a flange is
present in said second part, at the flange provided that a
circumferentially extending continuous portion of said upper
surface of the flange of the liquid and gas barrier material is
exposed to provide an area for a closing lid to be sealed to the
container.
10. The method according to claim 9 wherein no flange is present in
said second part and said first and second parts are joined
together only at the side walls.
11. The method according to claim 9 or 10 wherein said first and
second parts are formed simultaneously and joined coaxially
together in the same mold.
12. The method according to any one of claims 9 to 11 wherein said
first and second parts are joined together by heat-sealing.
13. A method of packaging a food product comprising loading said
product in the container of any one of claims 1 to 8; optionally
vacuumizing and/or gas flushing the container with a suitably
selected gas or gas mixture and closing said container by means of
a gas barrier closing lid sealed to the circumferentially extending
continuous portion of the upper surface of the flange of the liquid
and gas barrier material exposed around the circumference of the
container.
14. A gas-tight package for food products comprising a food product
loaded in a container of any one of claims 1 to 8 closed by a gas
barrier closing lid, disposed over the food product, and sealed to
the circumferentially extending continuous portion of the upper
surface of the flange of the liquid and gas barrier material
exposed around the circumference of the container.
15. The package according to claim 14 wherein the food product is
meat, poultry or fish.
Description
TECHNICAL FIELD
[0001] The present invention relates to gas barrier and liquid
absorbent containers for use in modified atmosphere packaging of
food products, in particular products that tend to release liquids.
The invention further relates to a method of manufacture of said
containers, to their use in the packaging of food products and to
the food packages thus obtained.
DISCLOSURE OF INVENTION
[0002] It is common practice in retail stores to display certain
types of foods, such as meat, poultry, fish and some vegetables, in
individually wrapped containers. To improve the shelf life of the
packaged product it is also common practice to package the food
product under a modified atmosphere, that is an atmosphere other
than air selected to prolong the shelf-life of the packaged
product. In order to maintain such a modified atmosphere within the
package gas barrier packaging materials are used. In general the
term "gas barrier" is used with reference to the ability of a
material to serve as a barrier to one or more gases, typically
oxygen. This type of package offers the advantage that food
packages, e.g. meat packages, can be prepared at a central location
and then distributed to supermarkets and small shops. The appeal
for the consumer is the possibility to see and inspect the packaged
product.
[0003] However, in the case of liquid containing products, such as
meat, poultry or fish, the liquids exuded from the food can create
a negative visual impression on the consumer. Furthermore, the
presence of these liquids in direct contact with the food product
may promote the growth of bacteria inside the package, thus
reducing the shelf-life of the product.
[0004] These problems have been generally overcome by the use of
absorbent pads, which are introduced in the package between the
product and the bottom of the container. Typically absorbent pads
comprise a mat of an absorbent material enveloped in a moisture
impermeable film that has a number of perforations on the surface
not in contact with the product. The use of an absorbent pad
suffers from the disadvantage of the labour cost involved in
inserting it into a container, including the cost of a padding
machine specifically designed for this purpose. Another
disadvantage of this system is the poor aesthetics of the pad when
filled with liquids, particularly blood. Furthermore when the pad
is saturated with liquids it tends to stick to the food product and
must be manually removed by the consumer when the package is
opened.
[0005] As an alternative to the use of absorbent pads the use of
double walled containers, provided with an internal reservoir for
the collection of the exuded liquids, has been proposed in the
prior art. WO 86/00275 discloses a rigid container comprising two
or more thermoformed trays nested together; each tray is provided
with a flange and all the flanges have the same size and are sealed
together when a closing lid is sealed to the container for closing
it.
[0006] WO 2007/059187 similarly discloses a container comprising a
first tray and a second tray, provided with at least one hole,
nested within the first tray to define a reservoir between the two,
the flange of the first tray being completely covered by the flange
of the second tray. The container is not provided with gas barrier
properties.
[0007] FR 2,564,807 discloses a container comprising a tray and an
insert, provided with a central opening, defining a reservoir at
the bottom of the tray. The container is not provided with gas
barrier properties.
[0008] It is therefore an object of the present invention to
provide a gas barrier container for food packaging which is capable
of absorbing, retaining and hiding the fluids exuded from the food
product placed thereon without requiring the use of a separate pad
and that at the same time provides an end package, obtained by
sealing a gas barrier closing lid to the container flange, which is
gas-tight.
[0009] In a first aspect the present invention is directed to a
container suitable for food packaging which comprises: a first part
made of a liquid and gas barrier material comprising a base and
upwardly extending side walls terminating in a continuous flange
outwardly projecting from the side walls, said flange being
provided with an upper surface and a lower surface, a second part
made of a liquid pervious material, comprising a base and upwardly
extending side walls optionally terminating in a flange outwardly
projecting from the side walls, said second part being coaxially
positioned into said first part in such a way that the bases of
said first and second parts are spaced apart from each other to
define an interspace and said first and second parts are joined
together at the side walls and, when a flange is present in said
second part, at the flanges provided that a circumferentially
extending continuous portion of said upper surface of the flange of
the liquid and gas barrier material is exposed to provide an area
for a closing lid to be sealed to the container.
[0010] When a gas barrier closing lid is sealed all around the
exposed upper surface of the flange of the liquid and gas barrier
material in the container of the present invention a gas-tight and
liquid absorbent package is obtained.
[0011] In a second aspect the present invention is related to a
method of manufacturing a container suitable for food packaging
comprising: [0012] forming a first part made of a liquid and gas
barrier material, said first part comprising a base and upwardly
extending side walls terminating in a continuous flange outwardly
projecting from the side walls, said flange being provided with an
upper surface and a lower surface; [0013] forming a second part
made of a liquid pervious material, said second part comprising a
base and upwardly extending side walls optionally terminating in a
flange outwardly projecting from the side walls; [0014] coaxially
inserting said second part into said first part in such a way that
the bases of said first and second parts are spaced apart from each
other to define an interspace and said first and second parts are
joined together at the side walls and, when a flange is present in
said second part, at the flanges provided that a circumferentially
extending continuous portion of said upper surface of the flange of
the liquid and gas barrier material is exposed to provide an area
for a closing lid to be sealed to the container.
[0015] In a third aspect the present invention is related to a
method of packaging a food product, said method comprising loading
the product into the storage compartment of the container of the
invention, optionally vacuumizing and/or gas flushing the container
with a selected gas or gas mixture suitable to extend the
shelf-life of the product and sealing a gas barrier closing lid to
the circumferentially extending continuous portion of the upper
surface of the flange of the liquid and gas barrier material
exposed all around the container.
[0016] In a fourth aspect the present invention is directed to a
gas-tight package for food products comprising a food product
loaded in a container according to the present invention and a gas
barrier closing lid, disposed over the food product, and sealed to
the circumferentially extending continuous portion of the upper
surface of the flange of the liquid and gas barrier material
exposed all around the container. The product is held under a
modified atmosphere suitable to prolong its shelf-life. The
modified atmosphere is maintained within the package due to the gas
barrier properties of both the container and the lid and to the
gas-tight seal that they form in the circumferentially extending
continuous portion of the upper surface of the liquid and gas
barrier material exposed all around the container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a sectional view of a first embodiment of the
container of the present invention;
[0018] FIG. 2 is a top view of a first embodiment of the container
of the present invention;
[0019] FIG. 3 is a sectional view of a second embodiment of the
container of the present invention;
[0020] FIG. 4 is a top view of the second embodiment of the
container of the present invention with a first perforation
pattern;
[0021] FIG. 5 is a top view of the second embodiment of the
container of the present invention with a different perforation
pattern;
[0022] FIG. 6 A-C are sectional views showing alternative
perforation arrangements for the central area of the inner part of
the container;
[0023] FIG. 7 is a sectional view of a first embodiment of the
package of the present invention;
[0024] FIG. 8 is vertical cross-sectional view showing a first step
of a first embodiment of the manufacturing method of the container
of the present invention;
[0025] FIG. 9 is vertical cross-sectional view showing a second
step of a first embodiment of the manufacturing method of the
container of the present invention.
[0026] FIG. 1 shows a container 1 according to the present
invention which comprises a first, or outer, part 10 and a second,
or inner, part 20 coaxially inserted into the first part 10.
[0027] First part 10 of the container comprises a base 12 and
upwardly extending side walls 13 terminating in a continuous flange
14. Flange 14 extends horizontally all around the contour of the
container, outwardly projecting from the side walls. Flange 14 is
provided with a lower surface 15. Flange 14 is provided with an
upper surface 16 for the sealing of a closing lid.
[0028] Relative to the container as a whole first part 10
represents the outer part of the container. That is, base 12 and
side walls 13 of the first part correspond to the base and the side
walls of the container. In the remainder of the text, the term
"outer part" may be exchanged with the term "first part" to
indicate component 10 of the container.
[0029] As shown in FIG. 1, second part 20 comprises a base 22 and
upwardly extending side walls 23 terminating in a flange 24.
Typically flange 24 extends continuously around the perimeter of
second part 20.
[0030] Relative to the container as a whole second part 20
represents the inner part of the container, that is base 22 and
side walls 23 are the internal, food-contact surfaces of the
container. In the remainder of the text, the term "inner part" may
be exchanged with the term "second part" to indicate part 20 of the
container.
[0031] In the embodiment shown in FIGS. 1 and 2 inner part 20 is
provided with a flange 24 and the inner and outer parts are joined
together at the side walls and in part of the flange area. Flange
24 of inner part is sized and/or positioned in such a way that it
does not completely cover flange 14 of the outer part. As shown in
FIG. 2, flange 24 of the inner part covers only partially flange 14
of the outer part of the container 10. A continuous portion 11 of
the upper surface 16 of flange 14 is not covered by flange 24
providing an area for a closing lid to be sealed all around the
circumference of the container. By sealing a gas barrier closing
lid to the exposed surface 11 of the liquid and gas barrier
material making up outer part 10 of the container it is thus
possible to obtain a gas-tight package.
[0032] The feature of the container of the invention whereby the
circumferentially extending continuous portion 11 of the liquid and
gas barrier material of the outer part is available on the upper
surface of the flange of the container for sealing to a closing lid
is advantageous when the inner part of the container is made of a
foamed material. If flange 24 were to cover completely flange 14 of
the outer part the gas barrier closing lid would be sealed to the
upper surface of flange 24. However, if inner part 20 is made of a
foamed material the lateral edges of the foamed material would
allow air to permeate and distribute through the inner part to
eventually equilibrate the atmosphere inside the package with the
atmosphere outside of it. It is only by providing an accessible
surface of the liquid and gas barrier material of the outer part 10
that a gas-tight package can be obtained when sealing a gas barrier
lid onto the container, regardless of the nature of the material
used to make the inner part.
[0033] In an alternative embodiment of the container of the present
invention, shown in FIGS. 3 to 5, inner part 20 does not comprise a
flange. Thus, the container will comprise a first part 10 made of a
liquid and gas barrier material with a base and upwardly extending
side walls terminating in a continuous flange outwardly projecting
from said side walls, said flange being provided with an upper
surface and a lower surface, a second part 20 made of a liquid
pervious material, comprising a base and upwardly extending side
walls, said second part being coaxially inserted into said first
part in such a way that the base of said second part is spaced from
the base of said first part to define an interspace and said first
and second parts are joined together at the side walls. According
to this embodiment the flange of the container consists only of the
liquid and gas barrier material making up the outer part.
[0034] The width of the continuous surface 11 of liquid and gas
barrier material exposed along a closed line all around the flange
area may vary depending on the size of the container but it is at
least 1 mm, at least 1.5 mm, preferably at least 2 mm, even more
preferably at least 3 mm. The width of the exposed surface 11
varies from the entire width of flange 14 of the first part, when
the second part of the container has no flange, to at least 10%,
30%, 50% of the total width of flange 14, when the second part of
the container has a flange 24. Typically the total width of the
flange is at least 3 mm, at least 4 mm, at least 5 mm and up to 10
mm, 11 mm, 15 mm.
[0035] The size and position of inner part 20 is selected in such a
way that, when inner part 20 is coupled to outer part 10, its base
22 does not contact base 12 of outer part. An interspace 30 is
created between the two parts of the container to collect the
fluids exuded from a product placed in the container.
[0036] As shown in FIG. 3 base 12 of outer part 10 may be provided
with ribs to separate the interspace in compartments which may
restrict the mobility of the collected fluids. Features other than
ribs may be present in base 12 to obtain the same effect. When ribs
or other equivalent features are present in base 12 it is preferred
that they do not contact base 22 of the inner part. Thus the
compartments within the interspace 30 are in fluid communication
with each other. Known absorbent materials, e.g. absorbent pads, or
polymers, such as salts of homo- or co-polymers of acrylic or
methacrylic acids or partially saponified polyacrylate or
polymethacrylate polymers, can be placed in interspace 30 to
further restrict or eliminate the mobility of the collected
fluids.
[0037] The side walls 23 of inner part 20 may have any length
relative to the side walls of the outer part of the container,
provided that when the two parts are coupled an interspace is left
in the base area of the container and the side walls of the inner
part do not exceed the length of the side walls of the outer part.
Typically, the side walls 23 of the inner part are at least 1 mm, 2
mm, 5 mm long to allow joining of the outer and the inner parts of
the container together. Preferably side walls 23 are at least 10
mm, 12 mm long. Even more preferably the length of side walls 23
coincide with the length of the part of side walls 13 of the outer
part comprised between the flange of the container and the base 22
of the inner part as shown in FIG. 3.
[0038] Inner and outer parts 20 and 10 are firmly joined together
at the side walls' area, for example by heat-sealing,
radiofrequency sealing or gluing. Suitable adhesives may be placed
between the side walls to improve the bonding between the outer and
inner parts of the container.
[0039] Typically the distance between inner part 20 and outer part
10, i.e. the height of the interspace 30 ranges from 1 to 40 mm,
from 1.5 to 30 mm, from 2 to 25 mm, from 2 to 20 mm. The distance
between the bases of inner and outer parts of the container of the
present invention may depend on the overall size of the
container.
[0040] The base and the side walls of inner portion 20 define the
storage area 40 of the container. Base 22 provides the resting
surface for the packaged product. Inner part 20 is made of a liquid
pervious material which allows the passage of liquids from the
storage area 40 of the container into interspace 30. When container
1 is used for packaging food products which exude liquids, the
liquid exuded from the product permeates through inner part 20 into
interspace 30 and is effectively removed from the storage area of
the container. The exuded liquid is therefore efficiently removed
from direct contact with the product and from the sight of the
consumer, improving both the shelf-life of the product and the
appeal of the package.
[0041] Inner part 20 is liquid pervious. The term "liquid pervious"
is used herein to indicate a material that allows the passage of a
liquid from the storage area of the container to the interspace.
The term applies equally to materials which are inherently capable
to permit the passage of a liquid as well as to materials which
require physical modifications, such as perforations, in order to
permit the passage of a liquid.
[0042] Inherently pervious materials are for instance some porous
materials. Examples of porous materials that may be pervious to
liquids are some non-woven films or some void-containing films
where the pattern of voids in the polymer matrix allows the passage
of liquids by capillarity. Typically these liquid pervious films
are made of polyolefin resins.
[0043] Pervious materials obtained by physical modification of an
impervious substrate are preferably made of a thermoplastic
material provided with perforations in at least part of its
surface. Examples of suitable thermoplastic materials include
polyethylenes, either homo- or co-polymers, such as
ethylene-.alpha.-olefin copolymers, ethylene-cyclic olefin
copolymers and ethylene-vinyl acetate copolymers, propylene homo-
or co-polymers, styrene homo- or co-polymers, polyesters,
polyamides, starches and the like polymers.
[0044] The thermoplastic material used to produce inner part 20 can
be a monolayer or a multilayer structure.
[0045] In a preferred embodiment of the container of the present
invention inner part 20 comprises at least one layer of a foamed
material.
[0046] Any type of polymer than can be foamed can suitably be
employed for inner part 20. Non-limiting examples of suitable
polymers include ethylene homo- and/or co-polymers, such as
ethylene-.alpha.-olefin copolymers and ethylene-vinyl acetate
copolymers, propylene-based polymers, styrene homo- and/or
co-polymers, polyesters, starches and the like polymers. Preferably
the foamed material is made of a material selected from the group
of styrene homo- and/or co-polymers, propylene-based polymers, and
starches. The foamed material is made of styrene homo- and/or
co-polymers. Alternatively, the foamed material is made of
polyesters homo- and/or co-polymers, preferably of poly(lactic
acid).
[0047] The thickness of the foamed layer is typically comprised
between 0.1 mm and 10 mm, preferably between 0.5 mm and 7 mm,
between 1 and 6 mm, between 1 and 4 mm.
[0048] The foamed material used for inner part 20 may have an open
cell structure, that is a structure in which the cells are at least
for their majority open, that is intercommunicating. Open cell foam
materials may absorb and store liquids similarly to a sponge and
facilitate the removal of liquid from the storage area of the
container of the present invention. Suitable polymers used to make
open cell foam materials are as indicated above for the foamed
material layer. Generally, open cell foam sheets with an absorbency
in the range of from 500 to 1,500 ml/m.sup.2 can be obtained by
suitably selecting the percentage of open cells, the size of the
cells and the thickness of the layer itself.
[0049] Typically, the thermoplastic material used to produce inner
part 20 is a multilayer structure comprising a foamed layer and at
least one solid layer.
[0050] Said solid layer can be positioned on the side of the
material that will be in contact with outer part 10. In this case
the solid layer provides better adhesion between the inner and the
outer parts of the container. Said adhesion layer can be of any
thermoplastic material and the preferred ones are those providing a
good adhesion to the surface layer of the gas barrier material
making up outer part 10. The thickness of said adhesion layer is
typically comprised between about 5 .mu.m and about 90 .mu.m,
preferably between about 10 .mu.m and about 85 .mu.m, more
preferably between about 15 .mu.m and about 70 .mu.m.
[0051] Inner part 20 can be made of a multilayer structure
comprising a styrene homo- and/or co-polymer foamed layer and a
solid adhesive layer. The adhesive layer comprises a material
selected from the group consisting of polystyrene, high impact
polystyrene, styrene-butadiene-styrene block copolymer,
styrene-ethylene/butene-styrene block terpolymer,
styrene-isoprene-styrene block copolymer and blends thereof,
ethylene-unsaturated ester copolymers, such as ethylene-vinyl
acetate copolymers, ethylene-butyl acrylate copolymers and the
like. Preferably the solid adhesive layer comprises a blend of high
impact polystyrene and styrene-butadiene-styrene block copolymer.
More preferably the solid adhesive layer comprises a blend of from
50%, 60%, 70%, 80%, 90% by weight of high impact polystyrene and of
from 10%, 20%, 30%, 40%, 50% by weight of styrene-butadiene-styrene
block copolymer.
[0052] When the foamed layer has an open cell structure the solid
layer is generally the food-contact layer and may improve the
thermal molding behaviour of the open cell foam sheet when it is
thermoformed. The solid layer, particularly an opaque one, may also
provide an aesthetic function hiding from view the liquid absorbed
in the open cell foam layer. Said solid food-contact layer can be
of any thermoplastic material and the preferred ones are those
providing for a good bond with the underlying open cell foam layer.
Generally the same resin used for the open cell foam layer can be
employed as a thick non-foamed layer for the food-contact layer.
The thickness of said food-contact layer is typically comprised
between about 5 .mu.m and about 100 .mu.m, preferably between about
10 .mu.m and about 85 .mu.m, more preferably between about 15 .mu.m
and about 80 .mu.m.
[0053] The thermoplastic material used to produce inner part 20 may
be provided with two solid layers, a food contact layer and an
adhesive layer.
[0054] Inner part 20 can be made of a multilayer structure
comprising a styrene homo- and/or co-polymer foamed layer, a
styrene homo- and/or co-polymer solid food-contact layer and a
solid adhesive layer. The adhesive layer comprises a material
selected from the group consisting of polystyrene, high impact
polystyrene, styrene-butadiene-styrene block copolymer,
styrene-ethylene/butene-styrene block terpolymer,
styrene-isoprene-styrene block copolymer and blends thereof,
ethylene-unsaturated ester copolymers, such as ethylene-vinyl
acetate copolymers, ethylene-butyl acrylate copolymers and the
like. Preferably the solid adhesive layer comprises a blend of high
impact polystyrene and styrene-butadiene-styrene block copolymer.
More preferably the solid adhesive layer comprises a blend of from
50%, 60%, 70%, 80%, 90% by weight of high impact polystyrene and of
from 10%, 20%, 30%, 40%, 50% by weight of styrene-butadiene-styrene
block copolymer. The foamed layer can have an open cell
structure.
[0055] Additional layers may be present in the multilayer material
used to produce inner part 20. For instance the material may
comprise an adhesive solid layer as described above, styrene homo-
and/or co-polymer foamed layer (with a closed cell structure) and a
styrene homo- and/or co-polymer foamed layer with an open cell
structure in contact with the product as shown in FIGS. 6A and
6B.
[0056] In the embodiments of the container of the invention shown
in FIGS. 1 to 5, perforations 28 are provided in inner part 20 to
allow the fluids to pass from the storage space of the container
into interspace 30. Preferably the perforations have a small
diameter, typically lower than 5 mm. When inner part 20 of the
container is mostly comprised of a close cell foamed material the
perforations have a diameter of at least 2 mm, preferably of at
least 3 mm. When inner part 20 of the container is mostly comprised
of an open cell foamed material the perforations can have a smaller
diameter of about 1.0 mm, preferably of about 1.5 mm.
[0057] Any number of perforations may be present to render inner
part 20 liquid pervious. One single perforation could be used,
although two or more perforations are preferred. The perforations
may have all the same diameter or they may have different
diameters. The perforations may be regularly distributed on the
portion of inner part 20 which defines the internal base of the
container. Alternatively, the perforations may be distributed
across the base portion of inner part 20 according to a specific
pattern. Many different perforation patterns can be devised
depending for instance on the type of product to be packaged, the
size of the container, the materials making up the inner part of
the container and so on. A first pattern, shown in FIG. 2,
comprises one perforation centrally located in the base portion of
inner container 20 and a number of smaller perforations regularly
positioned around the perimeter of said base portion. Alternative
patterns are shown in FIGS. 4 and 5, wherein the perforations are
localised in the central area of inner part 20.
[0058] Typically the number of perforations will depend on the
average diameter of the perforations and may suitably be comprised
between 20 and 40,000 per m.sup.2, between 50 and 30,000 per
m.sup.2, between 50 and 20,000 per m.sup.2, preferably between 100
and 10,000 per m.sup.2. The perforations are preferably
funnel-shaped towards the interspace and may have a round or
slightly oval section.
[0059] When an open cell foam material is used to make inner part
20 perforations that extend only partially through the foam layer
may be sufficient to allow the passage of the fluids from the
storage area of the container to the interspace. Different
perforation arrangements are shown in FIG. 6 A-C. Particularly
advantageous is the use of partial perforations made in a staggered
relationship on both the upper and the lower surface of the inner
part (shown in the FIGS. 6A-C).
[0060] Inner part 20 can also be provided with channels (as the
ones indicated with numeral 29 in FIGS. 4 and 5) or other
equivalent features which guide the exuded fluids towards the
apertures.
[0061] Outer part 10 of the container of the present invention is
made of a liquid and gas barrier material. The liquid and gas
barrier material may be a monolayer material of a gas barrier resin
or, preferably, a multi-layer material wherein at least one layer
has gas barrier properties, the whole structure being also liquid
impervious. Polymers that are typically employed for the gas
barrier layer in packaging applications are EVOH, polyesters,
polyamides and blends thereof.
[0062] As used herein, the term EVOH includes saponified or
hydrolyzed ethylene-vinyl acetate copolymers, and refers to vinyl
alcohol copolymers having an ethylene comonomer content preferably
comprised from about 28 to about 48 mole %, more preferably, from
about 32 to about 44 mole % ethylene, and even more preferably,
from about 36 to about 42 mole % ethylene, and a saponification
degree of at least 85%, preferably at least 90%.
[0063] The term polyesters refers to polymers obtained by the
polycondensation reaction of dicarboxylic acids with dihydroxy
alcohols or alternatively by the ring-opening polycondensation
reaction of lactones or lactides. Suitable dicarboxylic acids are,
for instance, terephthalic acid, isophthalic acid, 2,6-naphthalene
dicarboxylic acid and the like. Suitable dihydroxy alcohols are for
instance ethylene glycol, diethylene glycol, 1,4-butanediol,
1,4-cyclohexanedimethanol and the like. Examples of useful
polyesters include poly(ethylene terephthalate), copolyesters
obtained by reacting one or more dicarboxylic acids with one or
more dihydroxy alcohols, poly(lactic acid), polycaprolactone,
poly(butylene succinate) and the likes.
[0064] The term polyamide is intended to refer to polymers obtained
by the polycondensation reaction of dicarboxylic acids with
diamines or alternatively by the ring-opening polycondensation
reaction of lactams. The term polyamide refers to both homo- and
co- or ter-polyamides. This term specifically includes aliphatic
polyamides or co-polyamides, aromatic polyamides or co-polyamides,
and partially aromatic polyamides or co-polyamides, modifications
thereof and blends thereof.
[0065] The thickness of the gas barrier layer in the outer part of
the container will be set in order to provide the outer part of the
container with an Oxygen Transmission Rate (OTR) lower than 20,
lower than 15, preferably lower than 10 cm.sup.3/24 h per unit,
when measured at 23.degree. C. and 50% of relative humidity.
[0066] Preferably the liquid and gas barrier material is a
multilayer material comprising in addition to a gas barrier layer
at least a heat-sealable layer to give a hermetic seal with the
closing lid by a conventional heat-sealing step. Said heat-sealable
layer can comprise any thermoplastic material that can be
heat-sealed to the sealing layer of the closing lid that will close
the package. The preferred material will therefore depend on the
material used for the heat-sealing layer of the closing lid.
Generally said heat-sealable thermoplastic material will be
selected among the polyolefins, such as ethylene homo- or
co-polymers, propylene homo- or co-polymers, etc., the styrene
homo- or co-polymers, such as for instance polystyrene,
styrene-butadiene-styrene block copolymer,
styrene-ethylene/butene-styrene block terpolymer, and
styrene-isoprene-styrene block copolymer, and the hydrogenated
derivatives thereof, and the polyester homo- and co-polymers, such
as PETG, a glycol-modified polyethylene terephthalate, poly(lactic
acid). Suitable blends may also include peelable blends to provide
the container with an easy-to-open feature.
[0067] The thickness of said heat-sealable layer will be typically
comprised between about 2 .mu.m and about 100 .mu.m, preferably
between about 6 .mu.m and about 80 .mu.m, more preferably between
about 10 .mu.m and about 50 .mu.m.
[0068] Additional layers, such as tie layers, to better adhere the
gas barrier layer to the adjacent layers, may be present in the
liquid and gas barrier film and are preferably present depending in
particular on the specific resins used for the gas barrier layer
and on the possible presence of a structural layer.
[0069] The liquid and gas barrier material used for the outer part
of the container should have a sufficient rigidity to provide
structural integrity to the whole container. When the liquid and
gas barrier material is a monolayer structure this can be obtained
by using a material of a sufficient thickness, e.g. higher than
about 100 .mu.m, 150 .mu.m, 200 .mu.m, 300 .mu.m, or even 400
.mu.m.
[0070] When the liquid and gas barrier material used for the outer
part of the container is a multilayer structure the required
rigidity is generally obtained by means of a structural layer. The
structural layer can be made of any suitable thermoplastic
material, such as for instance styrene homo- and/or copolymers,
propylene homo- and/or copolymers, polyesters, polyethylenes, and
the like polymers, and be either foamed or solid. The structural
layer typically represents the outer surface of the end
container.
[0071] The structural layer can be made of a foamed polymer. The
structural layer can be of foamed polystyrene. Alternatively, the
structural layer can be of foamed poly(ethylene terephthalate).
Still alternatively the structural layer can be of foamed
poly(lactic acid).
[0072] Alternatively, the structural layer can be made of a solid,
cast polymer. The structural layer can be of cast polypropylene,
poly(ethylene terephthalate), poly(lactic acid), high density
polyethylene, polystyrene or high impact polystyrene.
[0073] The thickness of the structural layer is typically comprised
between about 0.1 and 7 mm, depending mainly on whether it is a
foamed or a cast material. Structural layers made of a cast solid
material are preferably from 0.1 to 4 mm, from 0.5 to 3 mm thick.
Structural layers of a foamed material are preferably from 1 to 7
mm, 2 to 6 mm thick. Thicker layers can however be employed, if
needed, to get the required stiffness, provided that the end
multilayer sheet can still be formed into a container of the
desired shape.
[0074] In a first embodiment of the present invention the
multilayer sheet used to form outer part 10 of the container will
comprise (from the outermost layer to the innermost layer) a
structural layer, typically of a material such as foamed
polystyrene, foamed polyester or foamed polypropylene, or a cast
monolayer sheet of e.g. polypropylene or polyester, a liquid and
gas barrier thermoplastic film comprising a gas barrier layer and a
heat-sealable layer.
[0075] In a second embodiment of the present invention the
multilayer sheet used to form outer part 10 of the container will
comprise (from the outermost layer to the innermost layer) a
structural layer, typically of a material such as foamed
poly(ethylene terephthalate) or foamed poly(lactic acid), or a cast
monolayer sheet of e.g. poly(ethylene terephthalate) or poly(lactic
acid) and a liquid and gas barrier heat-sealable layer.
[0076] The multilayer sheet can be obtained either by coextrusion
of all the layers using well-known coextrusion techniques or by
heat- or glue-lamination of the structural layer with the liquid
and gas barrier film. The overall thickness of this multilayer
sheet will typically be up to 9 mm, preferably it will be comprised
between 0.1 and 8 mm and more preferably between 0.5 and 7 mm.
[0077] A container according to the present invention which may be
particularly suitable for the packaging of food products like meat,
poultry and fish comprises a first part made of a liquid and gas
barrier material comprising a structural layer of foamed
polystyrene, a gas barrier layer preferably comprising EVOH and a
heat-sealable layer comprising a polyolefin and a second part made
of a thermoplastic material comprising a foamed polystyrene layer
provided with one or more perforations. Preferably, the second part
is made of a thermoplastic material comprising a foamed polystyrene
layer and an adhesive layer comprising a blend of from 50%, 60%,
70%, 80%, 90% by weight of high impact polystyrene and of from 10%,
20%, 30%, 40%, 50% by weight of styrene-butadiene-styrene block
copolymer. The foamed polystyrene layer may optionally have an open
cell structure.
[0078] A second container according to the present invention which
may also be suitable for the packaging of food products like meat,
poultry and fish comprises a first part made of a liquid and gas
barrier material comprising a structural layer of foamed
poly(lactic acid) and a second part made of a thermoplastic
material comprising foamed poly(lactic acid) layer provided with
one or more perforations.
[0079] A second object of the invention is a method for
manufacturing a liquid and gas barrier container.
[0080] In the method of the present invention first and second
parts of the container are formed into a tray-like shape comprising
a base, upwardly extending side walls and a flange outwardly
projecting from the side walls (optional for the second part) by
means of known forming techniques. Suitable forming techniques are
vacuum forming by which a preheated softened sheet is disposed on a
molding portion having the shape of a desired product, the air
present in the gap between the molding portion of the molding die
and the sheet is eliminated by pulling vacuum so that the sheet
conforms to the contours of the mold; match mold assist forming in
which a plug matching the internal shape of the mold is used to
guide the deformation of the sheet. Different techniques may be
used to form first and second part of the container.
[0081] Once formed, second part is coaxially inserted into and
joined to the first part in such a way that the base of said second
part is parallel to and spaced from the base of the first part to
define an interspace. The two parts are joined together at least
along the side walls and in the flange area, when the second part
of the container is provided with a flange.
[0082] Joining of the two parts can be done by heat-sealing, said
term indicating the pressing of the two parts together with a
heated tool, or alternatively the pressing of the two parts
together when still in a heated state right after the forming
operation has taken place. Alternatively, the two parts may be
joined together by radiofrequency welding. Still alternatively the
two parts may be joined together by gluing, for instance by means
of a hot-melt adhesive provided on either one of the two parts or
by means of a suitable heat-activated or light-activated adhesive.
Preferably, the two parts of the container are joined together by
heat-sealing. Joining by heat-sealing is facilitated by the
presence of an adhesive layer between the inner and outer parts of
the container, preferably of an adhesive layer positioned on the
side of the inner part of the container facing the outer part (i.e.
the side facing away from the product in the final package).
[0083] When second, or inner, part of the container is made of a
thermoplastic material rendered liquid pervious by perforations,
said perforations can be made in the thermoplastic material at any
time before, during or after the forming of the second part.
Typically the thermoplastic material is perforated in the mold
during the forming operation. Alternatively, the perforations can
be made in the already formed part after cooling of the
thermoplastic material.
[0084] Forming of the two parts can be done separately and the
parts brought together and joined afterwards, in a separate step.
Alternatively forming of the inner and outer parts can take place
substantially simultaneously in one single forming operation.
[0085] In a first embodiment of the manufacturing method of the
present invention first and second parts are formed independently
of each other in separate forming operations and are then coupled
together in a third operation. Joining of the two parts to provide
the final container may be done by heat-sealing, radiofrequency
welding, gluing or the like.
[0086] In an alternative embodiment, first and second parts are
formed simultaneously in the same mold with the base of the first
part oppositely facing the base of the second part. At the end of
the forming operation the second part is inverted, coaxially
inserted into and firmly joined to the first part. Joining can be
done by anyone of the methods discussed for the first
embodiment.
[0087] In still another alternative embodiment of the manufacturing
method of the present invention, first and second parts of the
container are coaxially formed and joined together simultaneously
in the same mold in one single operation. The forming and joining
steps of the method according to this embodiment are schematically
illustrated in FIGS. 8 and 9 which are vertical cross-sectional
views taken through a forming mold suitably designed to carry out
the coaxial forming operation. As shown in FIGS. 8 and 9 forming is
done using a vacuum forming technique.
[0088] FIG. 8 shows the mold 200 in its closed state during the
forming step of the cycle. Mold 200 comprises a female cavity 201
and a male plug 202. Male plug 202 is designed so that at its
maximum extension into female cavity 201 there will be no contact
between their respective surfaces, in particular in the area
defining the base of the final container. This will produce a gap
between the two formed webs of material in the area of the base and
an interspace will be formed in the final container.
[0089] Mold 200 further comprises a platen 203 positioned between
female cavity 201 and male plug 202. Platen 203 is provided with an
aperture which is aligned with both the female cavity and the male
plug.
[0090] A first web of a thermoplastic material 205 and a second web
of liquid and gas barrier material 206 are positioned on opposite
sides of platen 203. In particular first web 205 is positioned
between platen 203 and male plug 202, whereas second web 206 is
positioned between platen 203 and female cavity 201. Platen 203, or
any other suitable equivalent mean, ensures that first and second
webs 205 and 206 are not joined together in the area of the flange
and its immediate vicinity during the forming operation.
[0091] At the stage shown in FIG. 8 both first and second webs 205
and 206 have been preheated to a suitable forming temperature. For
instance, when both the first and the second web are mostly made of
foamed polystyrene material the webs are preheated to a temperature
of from about 120.degree. C. to about 160.degree. C. Heating of the
two webs is carried out with conventional heating means, such as an
heated oven. If required further heating may be provided to the
webs at this stage of the forming process, for instance by
introducing heated air between the webs through a suitably designed
aperture provided in platen 203 (not shown). Such an aperture could
be used also to introduced pressurised air between the webs to
assist with the forming of the parts.
[0092] As shown in FIG. 8 first web of thermoplastic material 205
is deformed to the surface shape of the male plug 202, and second
web of liquid and gas barrier material 206 is deformed to the
surface shape of the female cavity 201. To facilitate shaping,
vacuum may be applied to the underside of both female cavity and
male plug.
[0093] As shown in FIG. 9, once male plug 202 reaches its maximum
extension into female cavity 201 first web 205 is pressed into
contact with second web 206 which is still in contact with the
inner surface of female cavity 201. Male plug 202 and female cavity
201 are so designed that the two webs of material are pressed into
contact only in the area of the side walls and partially in the
area of the flange, when the inner part of the container is
provided with a flange. The pressure exerted at this stage on the
still heated webs effectively joins together the two webs. The two
webs are separated the one from the other in the area of the base
of the container to define an interspace for collecting the liquids
exuded by the product that will be packaged in the container.
[0094] To facilitate the joining of first and second part of the
container within the mold the formed portion of thermoplastic
material which corresponds to the inner part of the container (20)
may be severed from the web 205 while still in the mold. Typically
the cutting of the formed portion 20 from web 205 takes place
during the extension of male plug 202 into female cavity 201, for
instance by means of a cutting blade positioned in a gap between
male plug 202 and platen 203. Alternatively, platen 203 may
function as a cutting tool to severe the formed portion 20 of first
web 205 from the web itself.
[0095] At the end of the forming cycle container 1 is released from
the mold. Generally at this stage container 1 is still connected to
second web 206 and ready to be severed from said web in a
subsequent cutting station.
[0096] When second, or inner, part of the container is made of a
thermoplastic material rendered liquid pervious by perforations,
said perforations can be made at any time before, during or after
the forming of the container. The perforations in the inner part of
the container can be produced with conventional perforating means
in a separate step after the container has been released from the
mold. Alternatively, the perforations can be produced during the
thermoforming step, by providing male plug 202 with suitable
perforating means. Still alternatively, a thermoplastic web 205
already provided with perforations can be fed to the forming
operation.
[0097] A further specific object of the invention is the use of a
container according to the present invention in the packaging of a
food product under a modified atmosphere.
[0098] Modified atmosphere packaging is defined as "the packaging
of a perishable product in an atmosphere which has been modified so
that its composition is other than that of air". The air
surrounding the food product in the package is changed to another
composition selected among those capable to prolong the shelf-life
of perishable products like meat, poultry, fish and some
vegetables.
[0099] In the packaging method according to the present invention
the food product is loaded in the storage compartment 40 of
container 1 (FIG. 7).
[0100] The atmosphere inside the package is modified before a gas
barrier closing lid is heat-sealed to the container. The atmosphere
can be modified either by simply flushing with a suitable gas or
gas mixture or by firstly evacuating and then back-filling with a
suitable gas or gas mixture the space between the container and the
closing lid. The gas or the gas mixture is selected to maximize the
shelf-life of the product. Preferred gases to replace evacuated air
include oxygen, carbon dioxide, nitrogen, argon and mixtures
thereof.
[0101] Once this step has been completed, the gas barrier closing
lid is heat-sealed along a continuous sealing line to the portion
11 of the upper surface of the flange of the liquid and gas barrier
material exposed of the all around the container. A gas-tight
hermetic seal is obtained that allows to maintain the modified
atmosphere within the package.
[0102] Products which typically exude liquids and for which the use
of the container of the present invention would be advantageous are
for instance meat, poultry, fish and some vegetable products.
[0103] The packaging method of the invention may be performed on
currently available tray lidding machines, either automatic or
manual, like the ones commercially supplied by, e.g., Sealpac GmbH,
Multivac GmbH or Mondini SpA. In this type of machines pre-formed
containers are loaded onto the machine and, after loading of the
product in the container, sealing of a closing lid is carried out
by means of a sealing frame, which forms a continuous seal around
the circumferentially extending upper surface 11 of the liquid and
gas barrier material on the flange of the container. When inner
part of the container has a flange that extends partially over the
flange of the outer part the closing lid may be heat-sealed also to
the portion of the liquid pervious material present on the
flange.
[0104] FIG. 7 shows an example of a package 100 thus obtained,
wherein a product 101 is placed into a tray-shaped container 1 (as
illustrated in FIG. 3). The package is then closed by sealing a gas
barrier closing lid 102 to the circumferentially extending portion
11 of the upper surface of the flange of the liquid and gas barrier
outer part 10 along a closed line around the container. The closing
lid can be a flexible, semi-rigid or rigid film or sheet. The
closing lid may have a thickness ranging from 10 to 250 .mu.m, from
12 to 150 .mu.m, from 15 to 80 .mu.m, from 15 to 60 .mu.m. It can
be stretchable or not, oriented or non-oriented and if oriented it
can be heat-shrinkable or heat-set.
[0105] Closing lid 102 may be a monolayer or a multilayer material.
Closing lid 102 is provided with gas barrier properties in order to
preserve the modified atmosphere inside the package. Suitable gas
barrier lids typically have an oxygen transmission rate at
23.degree. C. and 0% relative humidity lower than 150, lower than
130, preferably lower than 100 cm.sup.3/m.sup.224 hatm (evaluated
according to ASTM method D-3985 and using an OX-TRAN instrument by
Mocon). Preferably closing lid 102 is a multilayer structure
comprising at least a gas barrier layer and a heat-sealable layer.
The heat-sealable layer will be selected to create with the exposed
upper surface of the flange of the liquid and gas barrier outer
part of the container a hermetic, gas-tight seal. Suitable resins
for the heat-sealable and the gas barrier-layers being as indicated
above for the liquid and gas barrier layer of the container.
Typically closing lid 102 will be provided with antifog properties.
Suitable films to be used as gas barrier lid 102 are for instance
those described in EP-A-692,374, EP-A-739,398, EP-A-797,507,
EP-A-801,046, EP-A-881,966, EP-A-987,103 or WO 2001/68363.
[0106] In a preferred embodiment of the package of the invention
gas barrier closing lid 102 is a multilayer heat-shrinkable film
provided with antifog properties. The film comprises a gas barrier
layer comprising EVOH and at least one heat-sealable layer
comprising one or more polymers selected from the group of
ethylene-.alpha.-olefin copolymers, ethylene-vinyl acetate
copolymers and propylene-.alpha.-olefin copolymers.
[0107] In an alternative embodiment gas barrier closing lid 102 is
a polyester based film provided with a heat-sealing layer capable
of sealing to a polyester sealing surface on the container.
[0108] Without prejudice to the principle of the invention, the
details of execution and the embodiments may vary from what has
been described by way of illustration, while remaining within the
scope of the invention as defined by the appended claims.
* * * * *