U.S. patent application number 11/416314 was filed with the patent office on 2006-08-31 for multi-layer heat-sealable packaging material, a food package made thereof and a method of packaging.
Invention is credited to Jalliina Jarvinen, Erkki Laiho, Kimmo Nevalainen, Tapani Penttinen, Markku Sainio, Martti Vahala.
Application Number | 20060193952 11/416314 |
Document ID | / |
Family ID | 8558166 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060193952 |
Kind Code |
A1 |
Penttinen; Tapani ; et
al. |
August 31, 2006 |
Multi-layer heat-sealable packaging material, a food package made
thereof and a method of packaging
Abstract
The invention relates to a multi-layer heat-sealable packaging
material especially for food packages. In addition, objects of the
invention are a food package formed of the said packaging material,
a method of packaging, and the use of the material for packages.
The packaging material (1) comprises a middle layer (3) of fibre
material, such as cardboard; at least one polymeric protective
layer (4, 5) protecting the product from going bad; and polymeric
heat sealing layers (2, 7) preferably on both sides of the
packaging material. According to the invention, the heat sealing
layer (7) forming the inner surface of the closed package, is
blended with light-absorbing pigment, such as carbon black, for
protecting the product from visible light. By further blending
white pigment, such as titanium dioxide, into the heat sealing
layer (7), a grey tint resembling an aluminium foil has been
achieved for the layer. The heat sealing polymer may be low-density
polyethylene (PE-LD), and an oxygen and aroma proof sealing layer
(4) of, for example, ethylene vinyl alcohol copolymer (EVOH) or
polyamide (PA) may be provided between it and the cardboard
(3).
Inventors: |
Penttinen; Tapani;
(Huutjarvi, FI) ; Jarvinen; Jalliina; (Hamburg,
DE) ; Nevalainen; Kimmo; (Karhula, FI) ;
Laiho; Erkki; (Porvoo, FI) ; Sainio; Markku;
(Porvoo, FI) ; Vahala; Martti; (Porvoo,
FI) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
8558166 |
Appl. No.: |
11/416314 |
Filed: |
May 3, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10181357 |
Sep 4, 2002 |
|
|
|
PCT/FI01/00346 |
Apr 9, 2001 |
|
|
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11416314 |
May 3, 2006 |
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Current U.S.
Class: |
426/106 |
Current CPC
Class: |
B32B 27/20 20130101;
B65D 81/30 20130101; Y10T 428/25 20150115; Y10T 428/31757 20150401;
Y10T 428/31504 20150401; Y10T 428/31913 20150401; Y10T 428/24942
20150115; B32B 27/10 20130101 |
Class at
Publication: |
426/106 |
International
Class: |
A23B 7/148 20060101
A23B007/148 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 10, 2000 |
FI |
20000847 |
Claims
1. A method for packing food comprising the steps of: providing a
packaging material comprising: (i.) a body layer of cardboard;
(ii.) at least one gas-proof polymeric barrier layer; and (iii.) at
least one polymeric heat-sealing layer into which black and white
pigments are blended for protecting the food from visible light and
imparting an aluminum color to the heat sealing layer; bending a
carton or case from said packaging material; and closing food into
said carbon or case by heat sealing.
2. The method according to claim 1, wherein the polymeric
heat-sealing layer comprises 0.05-0.5% light-absorbing black
pigment and 5-25% white pigment.
3. The method according to claim 2, wherein the polymeric
heat-sealing layer comprises 0.10-0.30% carbon black and 10-15%
titanium dioxide pigment.
4. The method according to claim 1, wherein the carton or case is
closed by heat sealing at a temperature of up to about 250.degree.
C.
5. A food package which contains perishable food closed into a
carbon or case formed by bending and heat-sealing from packaging
material comprising a body layer of cardboard, at least one
gas-proof polymeric barrier layer, and at least one polymeric
heat-sealing layer containing black and white pigments blended with
the heat-sealing polymer, the light-absorbing black pigment
protecting the packed food from visible light and the black and
white pigments together imparting a gray color to the heat-sealing
layer.
6. The food package according to claim 5, wherein the heat-sealing
layer has been tinted gray by blending into the heat sealing
polymer 0.05-0.5% light-absorbing black pigment and 5-25% white
pigment.
7. The food package according to claim 6, wherein the heat-sealing
layer has been tinted gray by blending into the heat-sealing
polymer 0.10-0.20% carbon black and 10-20% titanium dioxide
pigment.
8. The food package according to claim 5, wherein the heat-sealing
polymer is a polyolefin.
9. The food package according to claim 8, wherein the heat-sealing
polymer is low-density polyethylene.
10. The food package according to claim 5, wherein the barrier
layer and the pigmented heat-sealing layer are placed to the
interior of the body layer and that a colorless polymeric
heat-sealing layer is provided onto the surface of the package on
the outside of the body layer.
11. A heat-sealed product package for food that is sensitive to
light, said product package comprising multi-layer packaging
material that comprises a body layer of fiber material, at least
one gas-proof polymeric barrier layer, and at least one
light-absorbing polymeric heat-sealing layer containing black and
white pigments blended with the heat-sealing polymer.
12. The product package of claim 11, wherein said food that is
sensitive to light is liquid food.
13. The product package of claim 12, wherein said product package
is a milk carton or a juice carton.
14. A package for a light-sensitive product, said package
comprising an openable carton or case made by bending and heat
sealing packaging material comprising (i.) a body layer of fiber
material, (ii.) at least one gas-proof polymeric barrier layer
inside of the body layer, and (iii.) a polymeric heat-sealing layer
inside of the barrier layer, the polymeric heat-sealing layer
containing black and white pigments blended with the heat-sealing
polymer, the black pigment absorbing light and protecting the
product from visible light and the black and white pigments
together imparting a gray color to the inside of the carton or
case.
Description
[0001] The present invention relates to multi-layer heat-sealable
packaging material, especially for food packages. The packaging
material is based on a middle layer of fibre material, such as
cardboard, besides which it contains one or several protective
layers for extending the durability time of the packed product, and
heat sealing polymer on the surface of the material for closing the
package. In addition, the invention relates to a method based on
the use of the packaging material, a food package closed by heat
sealing, and the use of the packaging material for food packages,
such as heat-sealed milk and juice cartons.
[0002] It has been tried to make the packages for perishable liquid
foods, such as milk products and juices, oxygen and aroma proof for
improving the durability. The traditional procedure has been to
provide the fibre-based packaging material with a grey aluminium
foil, which provides an efficient protection against the
penetration of oxygen in the air and the escape of aromas in the
packed product. However, the use of aluminium foil used for a long
time is now decreasing due to its high costs, environmental hazards
and regulations concerning the recycling of materials. Aluminium is
undecomposable on dumping areas, and it is difficult to regenerate
packaging cardboard lined with aluminum.
[0003] Aluminium used as an oxygen and aroma barrier in food
packages has been replaced by polymers to an increasing extent; the
most important polymers being ethyl vinyl alcohol copolymer (EVOH),
polyamide (PA), and polyethylene terephthalate (PET). By combining
these polymers with binding agents and heat sealing polymers,
multi-layer cardboard has been formed, with which sealing
characteristics almost comparable with aluminium have at best been
achieved.
[0004] Another trend also depending on material costs and
tightening environmental regulations has been to decrease the
amount of polymer used for the coating of packaging cardboard. One
known polymer-coated food packaging cardboard, in which good oxygen
and aroma barrier and low material amounts in polymeric sealing and
binding agent layers have simultaneously been achieved, has been
described in the publication print FI-96752. The advantageousness
of the packaging cardboard of the publication is substantially
based on the low heat sealing temperature of about 250.degree. C.,
with which it is possible to prevent the formation of holes in the
polymer layer at the closing stage of the package and the resulting
weakening of the gas barrier. Also the risk of the taste and smell
of the product being harmed is reduced, as the heat sealing
temperature is as low as possible.
[0005] According to the publication FI-96752 it is possible to
incorporate glimmer into the EVOH sealing layer for improving the
adhesion of the layer to cardboard. It has also been shown that the
glimmer effects the gas barrier and reduces the permeability of
ultraviolet light. The patent application FI-980086 further
describes a multi-layer packaging cardboard, in which a
considerable amount of talcum has been added to the polymer in the
gas barrier layer. Also this application discloses a UV protection
generated with a sealing layer, according to the application by
adding to the layer, besides talcum, also a dye pigment comprising
at most 5% of the weight of the layer.
[0006] If the packaging cardboard and its polymeric coating layers
are thick, they form a relatively good protection against the
transmission of both ultraviolet radiation and visible light. The
fact that the ultraviolet radiation used as heat sealing polymer
has a weakening effect on polyethylene is mainly an advantage, as
it promotes the material decomposition on dumping areas. However,
as it has been the trend to thin the packaging material the
consequence has been that the transmission of visible light has
increased. This is especially the case when bleached sulphate pulp
is used in the material, which is best suitable for food packages
because of its organoleptic properties. Unbleached pulp efficiently
absorbs light, but its use in food packages is avoided because of
its possibly detrimental effect on smell and flavour. No
transmission of light or UV radiation occurred in traditional
packaging materials provided with aluminium foil.
[0007] The present invention is partially based on the observation
that the multi-layer packaging cardboard according to the
publication FI-96752 and respective modern packaging cardboard can
let through even 10% of visible light coming across it, and partly
on the observation that, similar to oxygen, also this light may
have a detrimental effect on the durability and quality of packed
food. The measurements carried out show that the light penetrating
the packaging material splits ascorbic acid in juice, thus reducing
its amount to about one third of the original during a storage time
of five weeks. In an otherwise similar preservation test, in which
the effect of light was eliminated, about 75% of the ascorbic acid
remained after the end of the test.
[0008] Due to the said surprising observations, it is the object of
the invention to provide a solution, with which the detrimental
transmission of light through the packaging material can be
prevented. The invention thus comprises a heat-sealable packaging
material which contains, besides the middle layer of fibre
material, at least one gas proof polymeric sealing layer protecting
the packed product and at least one polymeric heat sealing layer as
the surface layer of the material; the invention is characterised
in that the heat sealing layer contains a pigment that absorbs
light for protecting the product from visible light.
[0009] The invention thus requires that a pigment blending with
heat sealing polymer be used, which absorbs the visible light on
the wavelength area of 400-700 nm. Most efficient pigments are
black pigments absorbing over the entire wavelength area, such as
carbon black, which is not toxic and which is thus suitable for
food packages. Carbon black also provides an efficient protection
against ultraviolet radiation penetrating the package.
[0010] Incorporating the pigment into the heat sealing layer is
first of all due to the fact that the heat sealing layer generally
is considerably thicker than the other polymeric coating layers in
the multi-layer cardboard; the pigment achieves a smoother overlap
in the polymeric layer without stripes disturbing the appearance of
the layer. Secondly, the sealing characteristics of polymers in the
oxygen barrier layer often depend on their purity, due to which one
tends to avoid adding foreign components to these. Pigments blend
well with polyolefins typically used as heat sealing polymer, and
in the concentrations used, they do not hinder the extrudability or
heat-sealability of the polymer.
[0011] Especially advantageously the heat sealing layer of the food
package material according to the present invention has been tinted
grey by mixing appropriately a black pigment and a white pigment.
The white pigment reflects light from the surface of the material
and thus reduces the transmission of light of the material.
However, a more important advantage is the appearance of the
material which has been pigmented grey; the grey surface layer
namely looks like the aluminium foil traditionally used in food
packages, which consumers have got accustomed to in course of time.
This matter is very important for getting the material approved in
the market. Black pigment in itself would produce a nondescript
dark, aesthetically questionable material surface, which could be
resented by markets although the material would be functional in
every aspect from the technical point of view.
[0012] In practice, the transmission of light in wavelengths of
visible light can be made to fall almost to zero by adding a rather
small amount of black pigment into the heat seal polymer. The
amount of pigment in the heat sealing layer can be between about
0.05 and 0.5 wt. %, preferably about 0.10-0.30 wt. %, and most
preferably about 0.10-0.20 wt %. 0.2 wt. % is a limit, the
exceeding of which does not improve the absorption in practice, but
which may be exceeded for achieving a suitable level of grey.
Considering the suitable level of grey, the amount of white pigment
has to be considerably bigger than the amount of black pigment,
such as about 5-25%, preferably about 10-20%, and most preferably
about 10-15% of the weight of the heat sealing layer. By blending
0.15 wt. % of carbon black and 12 wt. % of titanium dioxide with a
low-density polyethylene (PE-LD), an optimal heat sealing
concentration has been found, which on cardboard deceptively
resembles aluminium foil.
[0013] The density of low-density polyethylene in the heat sealing
layers may be 912-935 kg/m.sup.3, preferably 915-930 kg/m.sup.3,
and the melt viscosity (MFR.sub.2) 0.5-20 g/10 min., preferably
3-10 g/10 min. In addition to pigments, at most 0.5% of molecular
sieve, such as sodium aluminium silicate, can be incorporated into
the heat sealing layer as deodoriser.
[0014] The packaging material of heat-sealable packages is normally
provided with a polymeric heat sealing layer on both sides. Only
the heat sealing layer remaining inside the packages is then
pigmented in accordance with the invention. The heat sealing layer
on the outer surface of the package is left colourless so that it
would not cover the printings on the cardboard.
[0015] Relating to the oxygen sealing layer of the package material
of the invention, reference is made especially to the publication
print FI-96752. In the said publication, the oxygen barrier polymer
can be EVOH, PET or PA, the latter blended with EVOH; in addition
to these, also PA as such; separate EVOH and PA layers adhered to
each other; and sealing polymers blended with minerals, such as
talcum may also come to question. In all cases, the oxygen and
aroma barrier and protection against visible light are combined in
the same packaging material according to the invention.
[0016] The invention further comprises heat-sealable packaging
material, which contains, besides the middle layer of fibre
material, at least one polymeric-based protective layer tinted grey
by blending into it light-absorbing black pigment, such as carbon
black, and white pigment, such as titanium dioxide, so that the
black pigment provides the packed product with protection against
visible light, the said grey protective layer acting simultaneously
as the heat sealing layer for the material. The blend proportions
of pigments in the protective layer can be as presented above. The
material is suitable for a packed product which has to be, above
all, protected from light during its storage.
[0017] It is characteristic of the method of the invention for the
packaging of food, in which a carton or case is bent from packaging
material comprising a middle layer of cardboard, at least one gas
proof polymeric sealing layer and at least one polymeric heat
sealing layer, into which food is closed by heat sealing, that the
heat seal layer is blended with light-absorbing pigment for
protecting the food from visible light. The heat sealing layer is
preferably tinted grey by using pigments, as is described above.
The carbon black and titanium dioxide pigments used in the
invention do not disturb the heat sealing of the package, so that
about 250.degree. C. is sufficient for the heat sealing
temperature. Thus, the technology known from the publication
FI-96752 can in itself be utilised in the invention without losing
any of the advantages mentioned in the publication.
[0018] In relation to the finished food package of the invention
and the use of the packaging material of the invention, reference
is made to the enclosed claims, especially to claims 13-18.
[0019] The invention is next explained in more detail by way of
example, referring to the enclosed drawings, in which
[0020] FIGS. 1-5 schematically present five different laminated
packaging materials of the invention; and
[0021] FIGS. 6 and 7 describe the transmission of light as a
function of the wavelength of light, measured from some packaging
materials of the invention and some packaging materials
representing the known state of technology.
[0022] FIGS. 1-5 are examples of multi-layer heat-sealable
packaging materials of the invention principally for the packaging
of food. The packaging material 1 consists in both cases of a
heat-sealable surface layer 2 of low-density polyethylene (PE-LD),
which forms the outer surface for the finished, closed package.
This is followed by a middle layer 3 of fibre material, which may
be, for example, cardboard of bleached sulphate pulp. Next in FIGS.
1-3 is a polymeric, oxygen and aroma proof sealing layer 4, the
material of which is ethylene vinyl alcohol copolymer (EVOH),
polyethylene terephthalate (PET), or a mixture of ethylene vinyl
alcohol copolymer (EVOH) and polyamide (PA). The packaging
materials of FIGS. 4 and 5 comprise two sealing layers 4, 5 adhered
to each other, the materials of which are EVOH and PA; in FIG. 4,
PA is placed against cardboard and EVOH is adhered to PA, and in
FIG. 5, EVOH is against cardboard and PA is adhered to EVOH. The
sealing layer 4 or layers 4, 5 is followed by a binding agent layer
6, which is, for example, low-density polyethylene modified with
maleic anhydride, and the purpose of which is to bind the sealing
layer to the heat sealing layer 7 of low-density polyethylene
(PE-LD) forming the inner surface of the package.
[0023] In the package materials 1 shown, one or several pigments
have been incorporated into the heat sealing layer 7 forming the
inner surface of the package according to the invention, the
intention being to prevent visible light from penetrating into the
closed package, in which light could harm the packed product..
Preferably the pigment used in accordance with the invention is
carbon black, which already in low concentrations provides an
almost perfect protection against light. According to the
invention, also white pigment, such as titanium dioxide, can be
added into the heat sealing layer 7, which has some effect on the
light protection but which, above all, provides the heat sealing
layer with an aesthetically pleasant appearance. resembling an
aluminium foil.
[0024] In the packaging materials 1 shown, the weight of the middle
layer 3 of cardboard is at least 170 g/m.sup.2, preferably 200-400
g/m.sup.2. The superimposed polymeric layers 4-7 can be placed to
the cardboard 3 as one stage by coextrusion. The amount of material
of the sealing layers 4, 5 and the binding agent layer 6 are 1-10
g/m.sup.2 per layer, preferably 2 -5 g/m.sup.2. The amount of
material of both the heat sealing layers 1, 7 is 5-60 g/m.sup.2,
preferably 20-50 g/m.sup.2, and most preferably 30-40 g/m.sup.2.
The share of carbon black in the heat sealing layer 7 forming the
inner surface of the package is 0.05-0.5 wt. %, preferably about
0.15 wt. %, and the share of titanium dioxide is 5-25 wt. %,
preferably about 12 wt. %, respectively.
[0025] The packaging material of the invention manufactured as a
continuous web can be die cut as blanks, which again can be bent
and heat-sealed to form closed food packages. The heat sealing
temperature is at most about 250.degree. C. Packed products may be
especially liquid foods, for example, juices and milk products,
such as milk, cream, sour milk, yoghurt, and ice-cream . Likewise
box-like packages for dry foods are possible, such as packages for
flour, powders, flakes, cereal, and animal food. Further, closed
dishes for ready-prepared foods can be provided, in which both the
dish and its lid are made of light-impermeable packaging material
of the invention.
[0026] In FIGS. 6 and 7 there are shown light-permeability curves
measured in the wavelength range of 400-700 nm for visible light,
of some multi-layer packaging materials of the invention and the
state of the art. In FIG. 6, the curve 8 has been obtained from
cardboard of bleached pulp, with a weight of 240 g/m.sup.2 and with
a coating of 20 g/m.sup.2 of clear, unpigmented polyethylene
(PE-LD); curve 9 has been obtained from likewise coated cardboard
of bleached pulp, with a weight of 300 g/m.sup.2; curve 10 has been
obtained from similarly coated cardboard of unbleached pulp, with a
weight of 239 g/m.sup.2, and the curve 11 illustrating the
invention has been obtained from cardboard of bleached pulp, with a
weight of 240 g/m.sup.2 and coated with 20 g/m.sup.2 of
polyethylene (PE-LD) which was tinted grey by blending into it
0.12% of carbon black and 7.5% of titanium dioxide.
[0027] By comparing the curves 8 and 9 of FIG. 6, the increase of
light transmission, which is a consequence of thinning the
cardboard manufactured of bleached mass, can be observed. The curve
10 further indicates that if the cardboard is made of unbleached
pulp, the problem of light transmission hardly exists. The
substantially corresponding light permeability of curve 11 has been
achieved by a polymeric coating layer of the invention, tinted grey
with the help of white and black pigment.
[0028] FIG. 7 contains light transmission curves measured as in
FIG. 6, illustrating the effect of the amount of titanium dioxide
and carbon black to the absorption of light. The curve 9
illustrating the state of the art and the curve 11 illustrating the
present invention are similar to those in FIG. 6. The curve 12 has
been obtained from cardboard of bleached pulp, with a weight of 300
g/m and coated with 20 g/m.sup.2 of polyethylene (PE-LD) containing
7.5% of titanium dioxide. The curve 13 was obtained from the same
base cardboard, which was coated with 17 g/m.sup.2 of the said
polyethylene bleached white, with 3 g/m.sup.2 of the said
polyethylene tinted grey blended with it. By comparing the curves
in FIG. 7, it can be noted that the titanium dioxide has a
relatively small effect on the reduction of light transmission, as
again the carbon black, even as low concentrations as 0.018%,
reduces the light permeating the material to under a third of the
value it would be without the adding of pigment.
[0029] The invention was further tested by following the change in
ascorbic acid concentration in packed apple juice during a five
week long durability test in storage temperatures of 9.degree. C.
and 23.degree. C. The packages were heat-sealed closed cartons, in
which packaging cardboard of the invention was used, the weight of
which was 240 g/m.sup.2, and which was coated with 5 g/m.sup.2 of
ethylene vinyl alcohol copolymer, 6 g/m.sup.2 of polymeric binding
agent, and on top 45 g/m.sup.2 of polyethylene (PE-LD) blended with
0.12% of carbon black and 7.5% of titanium dioxide, with which the
layer was tinted grey. The reference material was a packaging
cardboard similarly coated with polymer, but without the pigments
added to the topmost heat sealing layer.
[0030] Ascorbic acid concentration was measured from the juices at
the moment of packaging and after a storage time of two and five
weeks. The results are shown in the following table. TABLE-US-00001
TABLE Change in the ascorbic acid concentration (mg/l) in apple
juice Storage time 0 2 weeks 5 weeks Invention 9.degree. C. 450 395
355 Invention 23.degree. C. 450 355 340 Reference 9.degree. C. 450
375 155 Reference 23.degree. C. 450 275 145
[0031] The results show the considerable improvement in the
preservation of ascorbic acid in packed juice, achieved by the
invention.
[0032] It is obvious for one skilled in the art that the various
forms of embodiment of the invention are not restricted to the
above examples, but they may vary within the scope of the enclosed
claims. Instead of cardboard, also paper may be used as the middle
layer of the packaging materials, which is suitable for dry package
embodiments. In addition, the polymeric heat sealing layer can be
provided only on one side of the packaging material. On the other
side of the material, especially on the outer side of dry packages,
heat-sealable lacquer can be used.
* * * * *