U.S. patent application number 10/502090 was filed with the patent office on 2005-03-10 for method in the manufacture of a packaging laminate, a plant in the manufacture of the packaging laminate, and the thus manufactured packaging laminate.
Invention is credited to Andersson, Ingvar.
Application Number | 20050053738 10/502090 |
Document ID | / |
Family ID | 20287395 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050053738 |
Kind Code |
A1 |
Andersson, Ingvar |
March 10, 2005 |
Method in the manufacture of a packaging laminate, a plant in the
manufacture of the packaging laminate, and the thus manufactured
packaging laminate
Abstract
A method in the manufacture of a web-shaped packaging laminate
(22) comprising a core layer (24) of paper or paperboard, the
method including the steps of coating (38) a first side of a
material web (40) of paper or paperboard with an outer layer (26)
of thermoplastic material, an thereafter forming, with the aid of
laser burning (46, 48) on the thus thermo-plastic coated first side
of the packaging laminate (22), a perforation line (32) through
said thermoplastic layer (26) and said core layer (24). After said
coating (38) with the thermoplastic material but before the
formation of the perforation line, the packaging laminate (22) is
compressed (44, 10) on said first side for the formation of a
compression line (30) in which said core layer (24) is compressed,
whereafter said perforation line (32) is formed in said compression
line (30). The present invention also relates to a plant in the
manufacture of the packaging laminate, as well as the thus produced
packaging laminate (22).
Inventors: |
Andersson, Ingvar;
(Loddekopinge, SE) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
20287395 |
Appl. No.: |
10/502090 |
Filed: |
July 22, 2004 |
PCT Filed: |
March 18, 2003 |
PCT NO: |
PCT/SE03/00456 |
Current U.S.
Class: |
428/34.2 ;
428/156 |
Current CPC
Class: |
B23K 2101/16 20180801;
B23K 2103/40 20180801; B29C 59/007 20130101; Y10T 428/1303
20150115; B29C 2791/009 20130101; B23K 26/0846 20130101; B23K 26/40
20130101; B23K 26/382 20151001; B29C 59/046 20130101; Y10T
428/24479 20150115; B29K 2711/123 20130101; B29L 2009/00 20130101;
B23K 2103/42 20180801; B23K 2103/16 20180801; B23K 2103/50
20180801 |
Class at
Publication: |
428/034.2 ;
428/156 |
International
Class: |
B65D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2002 |
SE |
0200923-1 |
Claims
1. In the manufacture of a web-shaped packaging laminate,
comprising a core layer of paper or paperboard, a method comprising
the steps of coating a first side of a material web of paper or
paperboard with an outer layer of thermoplastic material, and
thereafter, with the aid of laser burning forming, on the thus
thermoplastic coated first side of the packaging laminate, a
perforation line through said thermoplastic layer and said core
layer, comprising the step, after said coating with the
thermoplastic material, but before the formation of the
perforation, of compressing the packaging laminate on said first
side, for the formation of a compression line in which said core
layer is compressed, whereafter said perforation line is formed in
said compression line.
2. The method as claimed in claim 1, wherein the compression line
and the perforation line are formed in relation to one another such
that a build-up of thermoplastic residual material around the
perforation line, after the laser burning, will substantially be
located entirely below the level of the surrounding surface of the
packaging laminate, the core layer preferably being compressed by
at most 70%, preferably at most 60% but at least 20%, preferably at
least 30% of its original thickness in said compression line.
3. The method as claimed in claim 1, wherein the compression is
considerably wider than the perforation line, preferably at least
1.5 times, as wide, and even more preferably at least twice as
wide, but at most ten times as wide, preferably at most five times
as wide.
4. The method as claimed in claim 1, wherein said web-shaped
packaging laminate is further processed after the forming of the
perforation line, on rollers and/or by rolling up on a reel.
5. A plant in the manufacture of a web-shaped packaging laminate
comprising a core layer of paper or paperboard, the plant
comprising a coating station for forming a coating layer of a
thermoplastic material on a first side of said core layer, followed
by a perforation station including a laser burner, the perforation
station being disposed to form a laser-burned perforation line on
the first side of the packaging laminate through said thermoplastic
layer and said core layer, characterised by comprising a
compression station between said coating station and said
perforation station, including a compression tool disposed to form
a compression line on said first side of the packaging laminate,
and that said perforation station is disposed to form said
perforation line in said compression line.
6. The plant as claimed in claim 5 wherein said compression tool
includes a roller which displays a projecting compression portion
around its circumference, said projecting compression portion being
preferably 1-3 mm and even more preferably 1.5-2.5 mm wide and
preferably 0.2-2 mm and even more preferably 0.2-1 mm high above
the surrounding surface of the roller, as well as a counter roller
which preferably displays a smooth circumferential surface, a gap
between said roller and said counter roller being adjustable.
7. The plant as claimed in claim 5 wherein it includes additional,
subsequent stations for further processing or handling of the
packaging laminate, including rollers and/or stations for rolling
up the packaging laminate on a reel.
8. A packaging laminate comprising a core layer of paper or
paperboard as well as a thermoplastic coating layer on a first side
thereof, displaying a laser-burned perforation line through the
core layer and the thermoplastic layer, wherein said perforation
line is disposed in a compression line on the first side of the
packaging laminate, in which compression line said core layer is
compressed.
9. The packaging laminate as claimed in claim 8, wherein the
compression line and the perforation line are formed in relation to
one another so that a build-up of thermoplastic residual material
around the perforation line is substantially located entirely below
the level of the surrounding surface of the packaging laminate, the
core layer preferably being compressed in said compression line by
at most 70%, preferably at most 60% but at least 20%, preferably at
least 30% in relation to its thickness surrounding the compression
line.
10. The packaging laminate as claimed in claim 8 wherein the
compression line is considerably wider than the perforation line,
preferably at least 1.5 times as wide, and even more preferably at
least twice as wide, but at most ten times as wide, preferably at
most five times as wide.
11. The packaging laminate as claimed in claim 8, wherein said
thermoplastic coating layer displays a surface weight or grammage
of 20-50 g/m.sup.2, preferably 20-40 g/m.sup.2, and that it
preferably includes a thermoplastic material selected from the
group essentially comprising polyethylene and polypropylene.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method in the manufacture
of a web-shaped packaging laminate comprising a core layer of paper
or paperboard, the method including the steps of coating a first
side of a material web of paper or paperboard with an outer layer
of thermoplastic material, and thereafter, with the aid of laser
burning on the thus thermoplastic coated first side of the
packaging laminate, forming a perforation line through said
thermoplastic layer and said core layer. The present invention also
relates to a plant in carrying the method into effect, as well as
the packaging laminate produced by means of the method.
THE STATE OF THE ART AND PROBLEM
[0002] Consumer packages for foods are often manufactured from a
flexible packaging material which, by cutting, folding, sealing and
filling, has been converted into filled and sealed packaging
containers of the desired configuration. The packaging material
normally consists of a laminate which includes a core layer of a
fibre material, e.g. paper or paperboard which is coated on both
sides with a liquid-tight, thermoplastic material, e.g.
polyethylene or polypropylene. The packaging laminate may also
include other layers of plastic or metal foil in order to provide
improved light barrier properties, gas barrier properties (in
particular against oxygen gas) or resistance to liquids. A special
type of packaging container consists of a packaging container
intended for retorting in the filled state. This allows the
packaging container to be stored with its contents at room
temperature for an extremely long time, of the order of up to 24
months, implying that packaging containers of this type constitute
completely adequate alternatives for preserved foods in metal cans
or glass jars, for example for animal foods. However, this
presupposes a packaging laminate particularly adapted for
retorting, for example normally displaying an outer thermoplastic
layer of polypropylene of greater thickness/grammage than that
which is conventional for corresponding packaging laminates which
are not intended for retorting.
[0003] Such a packaging laminate can be provided with a simple
opening arrangement in the form of a perforation which is realised
by laser burning on the thermoplastic side of the packaging
laminate in such a manner that the laser beam is caused to burn
through both the thermoplastic layer and the fibre core but stop at
a gas barrier layer which has higher density, normally a metal
foil. However, in the laser burning operation, residual materials
of the thermoplastic are formed, this residual material forming a
raised ridge on either side of the elongate perforation line
immediately adjacent the line. This phenomenon has been
demonstrated among others in U.S. Pat. No. 3,790,744 and also U.S.
Pat. No. 3,909,582. In packaging laminates for retorting, i.e.
packaging laminates with an extra thick outer thermoplastic layer,
these raised ridges of residual material from the thermoplastic
will become even more accentuated. When the packaging laminate is
further processed, including processing on rollers or rolling up on
magazine reels, these ridges of residual material may cause
problems. Thus, deposits of such residual material occur on the
rollers, and in such an event production must be stopped at regular
intervals for cleaning the rollers. When the packaging laminate is
rolled up on magazine reels, the ridges build up in the different
layers in the magazine reel on one another so that the reel becomes
uneven on the outside, which seriously impedes its handling.
Moreover, residual material from each ridge is deposited from the
outside of the packaging laminate onto the inside of the next layer
of packaging laminate in the reel, which implies an undesirable
presence of residual material on the inside of the packaging
laminate when this is to be reformed into packaging containers and
be filled with their intended contents.
[0004] One method of solving the problem of the build-up of ridges
of residual material could be grind them down. However, this is not
desirable, given the problem of dust formation. In large scale
production, large quantities of dust would be created which would
have a harmful effect on the working environment and which would
need to be taken care of.
[0005] Another, more general problem in connection with opening
arrangements in the form of perforation lines is to realise a
perforation which is easy to open (good accessibility) but which
does not incur the risk of leakage in the event of rough handling
of the packaging container.
BRIEF SUMMARY OF THE INVENTION
[0006] According to the present invention, a method and a plant are
proposed in the manufacture of a laser-perforated packaging
laminate whereby the above-outlined drawbacks are obviated or at
least reduced. According to the present invention, the thus
manufactured packaging laminate is also proposed which lacks
projecting ridges of residual material substantially from its outer
surface from the laser perforation, and which preferably displays
improved accessibility in the perforation, simultaneously with
superior integrity, i.e. slight risk of leakage.
[0007] This and other objects are attained by means of the method,
the plant and the packaging laminate as these are defined in the
appended Claims.
[0008] Instead of attempting to avoid the build-up of residual
material in the laser perforation, or to remove such a build-up of
residual material before the packaging laminate is further
processed and handled, the inventive concept herein is to conceal
the ridges of residual material so that they are substantially not
permitted to project out over (beyond) the outer surface of the
surrounding material. In practice, this is realised in that the
web-shaped packaging laminate is provided with a compression line
in which the laser perforation operation is thereafter carried out.
Thus, a compression line is formed on the outer thermoplastic side
of the packaging laminate whereby the fibre core layer is caused to
be compressed.
[0009] The compression line is formed in a compression station in
the plant, the compression station comprising a compression tool
with a male part in the form of a projecting compression portion
around the circumference of a roller, and a smoother counter
abutment, preferably in the form of a counter roller. The tool, and
thereby the thus formed compression line, differ from a tool for a
conventional crease line and the crease line proper, respectively,
both in dimensions and in the fact that the tool displays no female
part, i.e. a depression in the counter roller for receiving the
male part. Thus, in a conventional crease line, the material has
not substantially been compressed, but merely displaced out of the
plane of surrounding material, while the material (at least the
fibre core layer) in the compression line according to the present
invention is de facto compressed, the packaging laminate being
smooth on the opposite side against the compression line. Further,
the compression line according to the present invention naturally
differs from a conventional crease line in that a perforation line
is formed therein by laser burning.
[0010] According to one aspect of the present invention, said
packaging laminate, at least when it is intended for retorting,
displays a total thickness of the order of magnitude of 0.2-0.6 mm,
preferably 0.3-0.5 mm. On the opposing side to the outer
thermoplastic layer which is pressed down in the compression line,
the packaging laminate displays a gas barrier layer, preferably a
metal foil such as aluminium foil (Alifoil) as well as at least one
inner thermoplastic layer, intended to be in contact with the
contents of the packaging container.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention will now be described in greater
detail hereinbelow, with particular reference to the accompanying
Drawings. In the accompanying Drawings:
[0012] FIG. 1 shows a compression tool for carrying the method
according to the invention into effect;
[0013] FIG. 1A shows a part A of the tool according to FIG. 1 in
greater detail and in cross section;
[0014] FIG. 2 is a cross section througha compression line
including a perforation line in a packaging laminate according to
the present invention; and
[0015] FIG. 3 shows a production line for the present
invention.
[0016] FIG. 1 shows a compression tool for carrying the method
according to the present invention into effect, the tool carrying
generic reference numeral 10. The compression tool 10 includes a
roller 12 with a central portion 14 of larger diameter than the
roller 12 proper. On this portion 14, there are disposed two
projecting compression portions 16 which extend around the
circumference of the roller 12 and the central portion 14. That two
compression portions 16 are provided with slight interspace is
because the present invention, in the illustrated embodiment, is
intended to be utilised in connection with a plant of the type
described in SE-C-516 532, i.e. a production plant where the
web-shaped packaging laminate is provided with a printed region
centred in relation to a longitudinal centre line, the material web
being, in a step following the perforation step, divided up into
two webs of a final width through incisions in said centre line.
The centre line of the packaging laminate is thus disposed
according to the present invention centrally between the two
projecting compression portions 16 in FIG. 1.
[0017] A counter roller 18 with a smooth casing surface is disposed
to constitute a counter abutment in the compression operation. A
nip or gap 20 between the roller 12 and the counter roller 18 is
adjustable, whereby the compression tool 10 may be set, on the one
hand, for different thicknesses of the packaging laminate and, on
the other hand, for different depths of the compression line 30
(FIG. 1 A).
[0018] FIG. 1 A shows the section A in FIG. 1 in greater detail as
well as in cross section. Here, it is also shown how the packaging
laminate 22 is disposed between the roller 12 and the counter
roller 18.
[0019] The packaging laminate 22 includes a fibre core layer 24 of
paper or paperboard, as well as an outer thermoplastic coating
layer 26 which displays a surface weight or grammage of 20-50
g/m.sup.2, preferably 20-40 g/m.sup.2 and preferably also includes
a thermoplastic material selected from the group essentially
comprising polyethylene and polypropylene, most preferably
polypropylene. On its opposite side, the packaging laminate 22
displays a gas barrier layer, preferably an aluminium foil
(Alifoil), as well as at least one liquid barrier layer of
thermoplastic material. In the Figure, the gas barrier layer and
liquid barrier layer(s) have jointly been given reference numeral
28.
[0020] The projecting compression portion 16 on the roller 12 is
preferably 1-3 mm, and even more preferably 1.5-2.5 mm wide and
preferably 0.2-2 mm, and even more preferably 0.2-1 mm high above
the surrounding surface of the roller 12 (i.e. in reality the
surface of the central portion 14). Normally however, the entire
height of the projecting compression portion 16 of the compression
roller 12 is not utilised, but only its upper region is pressed
down into the packaging laminate 22. Both the inner and outer
angles of the projecting compression portion 16 are provided with
gently rounded radii, with a view to not damaging the thermoplastic
layer 26.
[0021] The projecting compression portion 16 on the roller 12
compresses the core layer 24, normally by at most 70%, preferably
at most 60%, but at least 20%, preferably at least 30% of its
original and surrounding thickness in the thus formed compression
line 30. As a result, the thermoplastic layer 26 sinks down into
the compression line 30 proper, but is not subjected to any actual
compression itself.
[0022] FIG. 2 shows the packaging laminate 22 after a laser
perforation line 32 has been formed substantially centrally in the
compression line 30. The compression line 30 is considerably wider
than the perforation line 32, preferably at least 1.5 times as
wide, and even more preferably at least twice as wide, but at most
ten times as wide, preferably at most five times as wide, in which
even the compression line 30 is preferably 1-3 mm, and even more
preferably 1.5-2.5 mm wide and 0.1-0.3 mm, preferably 0.15-0.25 mm
deep. The term `width` of the perforation line 32 is here taken to
signify the width of the holes themselves through the thermoplastic
layer 26 and the core layer 24, i.e. not including the width of
residual material 34 built up around the perforation line after the
laser burning operation. On the other hand, the width of the
compression line 30 should not be such that it may encompass both
the width of the perforation line 32 proper and the residual
material 34 built up around the perforation line. The depth should
be the least possible depth that permits the ridges of residual
material 34 after the laser perforation substantially to be located
completely below the level of the surrounding surface of the
packaging laminate 22.
[0023] FIG. 3 shows a plant or production line for carrying the
present invention into effect. A web-shaped core layer of paper or
paperboard is rolled up on a magazine reel 36. In a lamination
station (coating station) 38, an outer layer of thermoplastic
material, e.g. PE (polyethylene) or PP (polypropylene) is extruded
on the first side of the core layer. The web-shaped material 40 is
also provided with other layers, for the formation of the packaging
laminate 22 according to FIG. 1A. These additional
coating/lamination operations do not, however, form part of the
present invention and will not, therefore, be described in detail
here. The packaging laminate is possibly rolled up on a reel (not
shown) and transferred to another production line which. commences
with application of printing ink on the first side of the packaging
laminate, i.e. that side provided with the outer thermoplastic
layer 26, in one or more printing works 42a-f. The web-shaped
packaging laminate thereafter runs further to a compression station
44 where the compression tool 10 according to FIG. 1 and FIG. 1A
execute the compression line according to the present invention in
the packaging laminate. Thereafter, the packaging laminate is led
to a perforation station 46 where a conventional laser burner 48 is
disposed to form the perforation line 32 proper (FIG. 2). The
packaging laminate now provided with perforation line(s) is led
further via rollers 52 and is once again rolled up on a reel 54 in
order thereafter to be transferred to additional treatment and
processing stations. Such subsequent treatment operations may, for
example, consist of creasing and severing the web into a plurality
of narrower webs and/or into individual blanks. It is also
conceivable that the printing operation and/or the creasing
operation be carried out at other sites in the production line.
[0024] The present invention is not restricted to the embodiments
disclosed here, but may be varied without departing from the scope
of the appended Claims.
* * * * *