U.S. patent application number 10/492727 was filed with the patent office on 2004-12-09 for package lid, method for manufacturing the same and package sealed with the lid.
Invention is credited to Penttinen, Tapani, Salminen, Risto.
Application Number | 20040245138 10/492727 |
Document ID | / |
Family ID | 8562056 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040245138 |
Kind Code |
A1 |
Penttinen, Tapani ; et
al. |
December 9, 2004 |
Package lid, method for manufacturing the same and package sealed
with the lid
Abstract
The invention relates to a lid (1) that can be heat-sealed to
the opening of a package (2) and peeled off as the package is
opened. In addition, the invention comprises methods for
manufacturing such a lid and a package sealed with the lid, and
also a sealed package equipped with a lid. The lid (1) consists of
a fibrous material layer (6), whichmay be paper or cardboard, a
polymer oxygen-barrier layer (7), suitable materials of which are
polyethylene terephthalate (PET), ethylene vinyl alcohol copolymer
(EVOH) or polyamide (PA), and a polymer heat-seal layer (8). In
accordance with the invention, the heat-seal layer (8) combines
ethylene methyl acrylate copolymer (EMA), ethylene vinyl acetate
copolymer (EVA) and polyamide wax, adherence of the heat-seal layer
directly to the oxygen-barrier layer (7) having been allowed
without any intermediate binder. During the manufacture of the lid,
the oxygen-barrier and heat-seal layers (7, 8) can be applied onto
paper or cardboard by coextrusion. The packages equipped with a lid
in accordance with the invention comprises boxes, cups or goblets,
for instance, into which foodstuffs, such as drinks, nutrients fats
or ready-made foods have been packaged.
Inventors: |
Penttinen, Tapani;
(Huutjarvi, FI) ; Salminen, Risto; (Karhula,
FI) |
Correspondence
Address: |
PATTERSON, THUENTE, SKAAR & CHRISTENSEN, P.A.
4800 IDS CENTER
80 SOUTH 8TH STREET
MINNEAPOLIS
MN
55402-2100
US
|
Family ID: |
8562056 |
Appl. No.: |
10/492727 |
Filed: |
April 15, 2004 |
PCT Filed: |
October 15, 2002 |
PCT NO: |
PCT/FI02/00805 |
Current U.S.
Class: |
206/484.1 ;
53/477 |
Current CPC
Class: |
B32B 27/10 20130101 |
Class at
Publication: |
206/484.1 ;
053/477 |
International
Class: |
B65B 051/10; B65D
073/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 15, 2001 |
FI |
20012000 |
Claims
1. A lid that can be heated-sealed to an opening of a package and
peeled off as the package is opened, the lid comprising: a fibrous
material layer, a polymer oxygen-barrier layer, and a polymer
heat-seal layer comprising ethylene methyl acrylate copolymer,
ethylene vinyl acetate copolymer and polyamide wax, wherein the
oxygen-barrier layer having a higher melting point than the polymer
heat seal layer and wherein the heat-seal layer is adhered directly
to the oxygen-barrier layer without any intermediate binder.
2. A lid as defined in claim 1, wherein the polymer coating on the
fibrous material consists merely of said oxygen-barrier and the
heat-seal layer.
3. A lid as defined in claim 1, wherein the polymer in the
oxygen-barrier layer is comprised of at least one of polyethylene
terephthalate, ethylene vinyl alcohol co-polymer and/or
polyamide.
4. A lid as defined in claim 3, wherein the PET or PA
oxygen-barrier layer has a weight in the range from 10 to 70
g/m.sup.2, preferably from 20 to 40 g/m.sup.2.
5. A lid as defined in claim 3, wherein the EVOH oxygen-barrier
layer has a weight in the range from 5 to 25 g/m.sup.2, preferably
from 10 to 20 g/m.sup.2.
6. A lid as defined in claim 1, wherein the heat-seal layer has a
weight in the range from 5 to 30 g/m.sup.2, preferably from 10 to
20 g/m.sup.2.
7. A lid as defined in claim 1, wherein the fibrous material layer
is made up of paper having a weight in the range from 30 to 120
g/m.sup.2, preferably from 40 to 80 g/m.sup.2.
8. A lid as defined in claim 1, wherein the fibrous material layer
is made up of cardboard having a weight in the range from 130 to
600 g/m.sup.2, preferably from 220 to 300 g/m.sup.2.
9. A method from manufacturing a lid fixable by heat sealing to an
opening of a package that may be peeled off as the package is
opened, the method comprising the steps of: coating fibrous
material by co-extrusion in one single step with two polymer layers
adhering to fibers of the fibrous material and to one another, one
of said layers forming the oxygen-barrier layer and the other
forming a heat-seal layer comprising at least one of a blend of
ethylene methyl acrylate copolymer ethylene vinyl acetate copolymer
and polyamide wax.
10. A method as defined in claim 9, further comprising the steps
of: providing the fibrous material as a moving fibrous material
web, extruding the polymer layers as continuous films on said
moving fibrous material web; and separating discrete from the web
by one of cutting and punching.
11. A method for manufacturing a sealed package, with a lid that
allows the lid to be peeled off as the package is opened, the
method comprising the steps of: forming the lid from a fibrous
material layer, a polymer oxygen-barrier layer and a heat-seal
layer, the heat-seal layer adhered directly to the oxygen-barrier
layer without intermediate binder, the heat-seal layer containing a
blend of ethylene methyl acrylate copolymer, ethylene vinyl acetate
copolymer and polyamide wax, and heat-sealing the lid at the
opening of the package.
12. A method as defined in claim 11, further comprising the step of
having the heat-sealing temperature is in the range from 150 to
190.degree. C.
13. A sealed package manufactured with the method of claim 11
wherein the package comprises a container, a packaged product
contained in the container and a lid heat-sealed at the opening of
the container, the lid being made up of a fibrous material layer, a
subjacent polymer oxygen-barrier layer, and a heat-seal layer
forming the inner surface of the lid and adhered directly to the
oxygen-barrier layer without any intermediate binder, the heat-seal
layer containing ethylene methyl acrylate copolymer, ethylene vinyl
acetate copolymer and polyamide wax, and allowing the lid to be
peeled off as the package is opened.
14. A package as defined in claim 13, wherein the container is a
cardboard box, cup or goblet coated with polymer on the inside
and/or the outside.
15. A package as defined in claim 13, wherein the container is a
plastic box, cup or goblet.
16. A package as defined in claim 13, wherein the container is made
of glass.
17. A package as defined in claim 13, wherein the package is a
sealed food package.
18. A package having a lid heated-sealed to an opening of the
package and peelable off as the package is opened, the lid
comprising: a fibrous material layer, a polymer oxygen-barrier
layer, and a polymer heat-seal layer comprising at least one of
ethylene methyl acrylate copolymer, ethylene vinyl acetate
copolymer and polyamide wax, wherein the oxygen-barrier layer has a
higher melting point than the polymer heat seal layer and wherein
the heat-seal layer is adhered directly to the oxygen-barrier layer
without any intermediate binder.
Description
[0001] This invention relates to a lid that can be heat-sealed to
the opening of a package and peeled off when the package is opened,
comprising a fibrous material, layer a polymer oxygen-barrier
layer, and a polymer heat-seal layer. Moreover, the invention
relates to a method for manufacturing the lid, a method for package
closed with the lid and the sealed package thus obtained.
[0002] Heat-sealed peelable lids are used in different consumer
packages. Typical packages are consumer and single-use packages
containing liquid, humid or fat foodstuffs. Packaged products
include milk, sour milk, yoghurt and other diary products, juices,
water, desserts, nutrient fats, such a butter and margarine, and
ready-made food. Dry, powderous or particulate products such as
medicines are similarly packaged.
[0003] A package container or vessel sealed with a heat-sealed lid
is most frequently made of plastic, such as polypropylene or
polystyrene, polymer-coated cardboard or glass, for instance. The
lid material is aluminium, which, however, involves the problem of
having a tendency to tear as the package is opened, and what is
more, is not decomposable at waste dumps. Polymer-coated paper or
cardboard an optional lid material eliminating these problems. The
polymer layers in the lid have provided adequate mechanical
strength, the oxygen and aroma seal required for the product and
facilities for heat-sealing the lid as the package is closed and
for peeling it off as the package is eventually opened.
[0004] Polymer-coated package lids have been manufactured by first
producing a polyethylene terephthalate film laminated with hot-seal
varnish, and then attaching it to paper or cardboard by gluing.
However, it is awkward to use such a two-step process yielding said
polymer film as an intermediate product.
[0005] WO patent specification 92/04187 describes a process for
manufacturing a heat-sealed and peelable package lid by applying
the polymer layers forming the polymer coating on top of one
another onto the paper in one single co-extrusion step. The coating
consists of a binder layer, an oxygen-barrier layer, a second
binder layer and a heat seal layer, the layers being placed in this
order on the bottom side of the paper, which ultimately will form
the inner surface of the lid. The specification mentions as
materials of the oxygen-barrier layer polyethylene terephthalate
(PET), ethylene vinyl alcohol polymer (EVOH) and polyamide (PA).
The heat-seal layer is defined as a mixture containing polyethylene
modified with metacrylic acid and ethylene vinyl acetate acting as
an adhering component and ethylene metacrylic acid copolymer acting
as a detaching component. FI patent specification 104 887 further
describes a polymer-coated package lid, in which the warping
problem entailed by the lid of WO patent specification 92/04187 is
solved by admixing crystaline and amorphous polymer in the
oxygen-barrier layer. The inner paper surface of the three-layered
coating described in the reference comprises an oxygen-barrier
layer, a binder layer and a heat-seal layer, in this order.
[0006] The purpose of this invention is to provide a package lid
made of polymer-coated paper or cardboard which can be heat-sealed
and peeled off, which can be manufactured by co-extruding the
polymer layers in one single step and which allows reduction of the
number of polymer layers on top of each other. The invention is
characterised by the heat-seal layer containing a mixture of
ethylene methyl acrylate copolymer (EMA), ethylene vinyl acetate
copolymer (EVA) and polyamide wax, and in the heat-seal layer being
adhered directly to the oxygen-barrier layer having a higher
melting point, without any intermediate binder.
[0007] In accordance with the invention, it has now surprisingly
been found that said polymer material in the heat-seal layer can be
adhered as such by co-extrusion to the most frequently used
oxygen-barrier polymers, i.e. polyethylene terephthalate, ethylene
vinyl alcohol copolymer or polyamide, despite the large difference
between the melting points of the polymers. Consequently, it will
not be necessary to use any prior art polymer binder layer between
the oxygen-barrier layer and the heat-seal layer.
[0008] The mixture of EMA, EVA and polyamide wax in accordance with
the invention has been stated to provide good heat-sealing to
materials of various types, such as plastic, polymer-coated or
uncoated paper or cardboard and also glass.
[0009] A particularly preferred embodiment of the invention
comprises a permanent seal of a cardboard freeze box, mould or
drinking cup coated with PET by means of a heat-seal lid, such a
seal having been problematic using prior art heat-seal
materials.
[0010] Heat sealing can be performed at temperatures at which the
oxygen-barrier layer remains intact with no leakage occurring
through the heat seal, which would risk deteriorating the
conservation of the product. The sealed package has been noted to
withstand freezing without the lid coming off or leakage of the
heat seal.
[0011] Without restricting the invention, the EMA obviously has the
function in the heat-seal mixture of allowing the lid to be peeled
off. EVA achieves adherence of the heat-seal layer to the
oxygen-barrier layer and adherence of the seal to the counter
surface of the lid, from which the lid can be detached. Experiments
have shown that, if EMA and also EVA are excluded, the lid becomes
inoperative, in other words, the presence of both EMA and EVA is
indispensable. Polyamide wax is necessary for workability of the
mixture, the wax accounting for 0.8% of the mixture according to
tests. If a smaller amount is used, the mixture adheres to tools
and prevents materials with which it is coated from rolling.
Polyamide wax also contributes to the ease of peeling off the lid.
Polyolefin is added to the blend as a less expensive filler. In
accordance with the invention, the proportion of polyamide wax in
the polymer blend of the polymer-seal layer may be in the range
from 0.8 to 5%, the proportion of EVA in the range from 20 to 50%,
and the proportion of EMA in the range from 10 to 30%. The
remainder of the blend may consist of polyolefin, such as
polyethylene or polypropylene.
[0012] The polymer coating on the lid of the invention may
preferably consist merely of a double-layer coating comprising said
oxygen-barrier and heat-seal layers. However, whenever necessary,
the oxygen-barrier may consist of more layers, which are different
barrier polymers, such as EVOH and PA layers adhered to each
other.
[0013] With PET or PA as the material of the oxygen-barrier layer,
its layer weight may vary in the range of 10 to 70 g/m.sup.2, most
preferably in the range from 20 to 40 g/m.sup.2. With EVOH as the
packaging material, the layer weight may be in the range from 5 to
25 g/m.sup.2, most preferably 10 to 20 g/m.sup.2. The heat-seal
layer, in turn, may have a weight in the range from 5 to 30
g/m.sup.2, most preferably 10 to 20 g/m.sup.2.
[0014] In accordance with the invention, the fibrous material layer
may consist of paper, having a weight from 30 to 120 g/m.sup.2,
preferably 40 to 80 g/m.sup.2, or cardboard, having a weight of 130
to 600 g/m.sup.2, Preferably 220 to 300 g/m.sup.2. A paper-base lid
is suitable for sealing a relatively small cup or goblet, whereas a
cardboard-based lid is is suitable especially as the inner lid of a
box-like package.
[0015] The method according to the invention for manufacturing the
above-described lid that can be heat-sealed and peeled off is
characterised by coating the fibrous material by coextrusion in one
single step with two polymer layers adhering to the fibres and to
each other, one of said layers forming the oxygen-barrier layer and
the other forming the heat-seal layer allowing peeling off of the
lid, the latter containing a blend of EMA and EVA and polyamide
wax. The polymer layers can be extruded as continuous films on a
fibrous material web, and separate lids are subsequently formed by
cutting or punching the web.
[0016] The method in accordance with the invention for
manufacturing a sealed package comprises substantially heat-sealing
of a lid at the opening of the package, the lid comprising a
fibrous material layer, a polymer oxygen-barrier layer and a
heat-seal layer adhered directly to the oxygen-barrier layer
without intermediate binder, the heat-seal layer containing EMA and
EVA and also polyamide wax and enabling the lid to be peeled off as
the package is opened. The heat-sealing temperature may vary within
the range of 150 to 190.degree. C. At these temperatures,
heat-sealing does not cause holes in the oxygen-barrier layer made
of PET, EVOH or PA and having melting points above 160.degree.
C.
[0017] The sealed package of the invention is characterised by
comprising a container, a package product contained in the
container, and a lid heat-sealed to the opening of the container,
the lid being made up of a fibrous material layer, a subjacent
polymer oxygen-barrier layer and a heat-seal layer forming the
inner surface of the lid and adhered directly to the oxygen-barrier
layer without any intermediate binder, the heat-seal layer
containing a blend of EMA and EVA and also polyamide wax allowing
the lid to be peeled off as the package is opened. In food packages
of the invention, such as packages for drinks, diary products,
nutrient fats or ready-made foods, the container is typically a box
or goblet made of plastic or cardboard coated with polymer on the
inside and/or outside. In box-like packages, and also in packages
having a package container made of glass, the heat-sealed lid is
typically a peelable inner lid inside the outer cover fixed by
screwing or snap attachment.
[0018] The invention is explained more in detail below with
reference first to the accompanying drawing, in which
[0019] FIG. 1 shows a drinking cup with a lid in accordance with
the invention,
[0020] FIG. 2 illustrates the opening of the cup of the Figure in
cross-section on a larger scale, showing the heat-seal joint
between the opening and the lid,
[0021] FIGS. 3 and 4 show the layer structures of the lid in two
different material combinations, and
[0022] FIG. 5 shows co-extrusion and adherence of the polymer
layers to the fibrous material web in the lid manufacturing
process.
[0023] FIG. 1 exemplifies a product package of the invention, which
is formed of a drinking cup 2 equipped with a lid 1. The content 3
of such a package is typically water, juice, milk or a diary
product, such as yoghurt. The lid 1 shown in FIG. 2 is tightly
heat-sealed to the border flange 4 of the cup 2, comprising a flap
5, which can be pulled in order to remove the lid and open the
package.
[0024] FIGS. 3 and 4 exemplify the three-layer structure 6-8 of the
lid shown in FIG. 2. The lid comprises a paper layer 6, having a
weight of e.g. 40-80 g/m.sup.2 and forming the outer surface of the
lid 1. In FIG. 3, the inner polymer coating of the lid consists of
a PET layer 7, having a weight e.g. in the range from 20 to 40
g/m.sup.2, and a heat-seal layer 8, which forms the inner surface
of the lid 1 on the package and whose weight is e.g. in the range
from 10-20 g/m.sup.2. The heat-seal layer 8 of the example may
contain, for instance, at least polyamide wax, about 20% of EMA,
about 40% of EVA, the remainder being polyolefin. A suitable
material of the heat-seal layer 8 is the product Mormelt 84
marketed by Rohm & Haas, having a density of 0.955 g/cm.sup.2,
a fusion point of 74.degree. C. and a melt index of 45 to 55 g/10
min.
[0025] The layer combination of the lid 1 in FIG. 4 differs from
that of FIG. 3 only in that the material of the oxygen-barrier
layer 7 is EVOH instead of PET, having a layer weight of e.g. 10 to
20 g/m.sup.2.
[0026] Besides for cups or goblets of plastic or coated cardboard,
the lid materials shown in FIGS. 3 and 4 are suitable also for
box-like packages made of plastic or cardboard, especially as an
inner peelable lid of the package or as similarly removable inner
lids for glass container packages. Instead of paper 6, cardboard
having e.g. a weight in the range from 220 to 300 g/m.sup.2 is
preferably used in the inner lids of boxes.
[0027] As shown in FIG. 5, the lid material is manufactured in a
continuous process, in which the polymer oxygen-barrier layer 7 and
the polymer heat-seal layer 8 are co-extruded on a continuous
moving paper or cardboard web 6. The web 6 is subjected to a
preliminary corona treatment 9. The polymer layers 7, 8 are joined
in an extruder 10 and are guided from the nozzle end 11 as a
uniform film 12 to a nip between the rollers 13, 14 rotating along
with the paper or cardboard web 6, with the rollers pressing the
layers together while maintaining the webs in movement. Thus, the
process yields the lid material as a continuous web 15, from which
the lids of individual packages are removed by cutting or
punching.
EXAMPLE 1
[0028] A PET layer having a weight of 20 g/m.sup.2 was applied to
wrapping paper having a weight of 90 g/m.sup.2, and uppermost a
heat-sealing layer (Mormelt 804) having a weight of 15 g/m.sup.2. A
piece was cut from the polymer-coated paper thus obtained to form
the lid of a food box made of polystyrene. The lid was fixed to the
box opening by heat-sealing for 2 seconds at a sealing temperature
of 175.degree. C. A tight seal was achieved between the polystyrene
and the Mormelt heat-seal layer, and to open the box, the lid was
removable in intact state from the box opening.
[0029] The test was repeated with the same result, using package
boxes made of polyethylene and polypropylene.
EXAMPLE 2
[0030] A piece was cut from the polymer-coated wrapping paper
obtained in example 1 and the piece was heat-sealed to form the lid
at the opening of a glass container. The heat-sealing period was 2
seconds and the temperature 175.degree. C. During the sealing, the
Mormelt layer of the lid adhered tightly to the glass surface of
the container opening, and to open the container, the lid was
removable intact from the container opening.
EXAMPLE 3
[0031] Packing board having a weight of 255 g/m.sup.2 was coated
with a PET layer having a weight of 40 g/m.sup.2, and a nutrient
fat box was made from this coated board by scoring, with the PET
layer as inner surface of the box. The same packing board was also
coated by applying by means of co-extrusion a PET layer having a
weight of 20 g/m.sup.2, with an uppermost heat-seal layer (Mormelt
804) having a weight of 15 g/m.sup.2. A piece was cut from this
double-layer coated board and heat-sealed to form the lid at the
opening of the nutrient fat box, with a sealing period of 2 seconds
and at a temperature of 175.degree. C. During the sealing, the
Mormelt heat-sealing layer adhered tightly to the PET coating on
the border flap of the box, and to open the box, the lid was
removable intact from the opening of the box.
[0032] The test was repeated with the same result on a box made of
uncoated packing board.
[0033] It is obvious to those skilled in the art that the
applications of the invention are not confined to the examples
above, but may vary within the scope of the accompanying
claims.
* * * * *