Note: Descriptions are shown in the official language in which they were submitted.
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PACKAGING MATERIAL MADE OF UNBLEACHED KRAFT PAPER, SLEEVE
PRODUCED THEREFROM, AND METHOD FOR MANUFACTURING SAME
The present invention relates to a packaging material
consisting of an unbleached kraft paper with a Kappa number
according to ISO 302:2015 between 38 and 60, preferably
between 40 and 58 as the base material, wherein the kraft
paper is manufactured from at least 90 % primary cellulose
and has a grammage according to ISO 536:2019 between 65 g/m2
and 170 g/m2, as well as a sleeve or banderole respectively,
produced from such a packaging material, a method for
producing the same and a sleeve manufactured from such a
packaging material and a use of the packaging material.
Unbleached kraft paper is widely used as a packaging material
since it has a high resistance to tearing and furthermore,
it also has good stability with respect to exposure to
moisture and chemicals. Kraft paper is also easy to print,
regardless of whether it is bleached or unbleached, so that
for a consumer of the packaged goods the necessary
information printed directly on the packaging can be seen.
A typical use of kraft paper and in particular unbleached
kraft paper is its use in the production of bags for the
packaging of a wide variety of materials, such as building
materials, sharp-edged materials, food, toys or the like. In
the packaging sector, however, there is not only the form of
packaging in which the goods to be packaged are completely
wrapped in the packaging paper, such as, for example, bags
closed on all sides, but it is frequently possible to simply
surround goods to be packaged or goods to be sold in bundles
with a kind of loop, on which information about the contents,
possibly the shelf life or the like, and frequently brand
names are printed. Such loops frequently also serve to
provide cohesion of a plurality of similar or different
related goods to be packaged and, for example, in the
clothing sector frequently several goods, such as a plurality
of T-shirts, socks or the like are packaged by enclosing
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them with a loop or a sleeve. It is essential for the
packaging material from which such a loop is made that it
tightly encloses the goods to be packaged or enclosed so
that the loop cannot be pulled down unintentionally and that
one or more of the products enclosed by the loop cannot fall
out and it is further ensured that the goods to be surrounded
by the loop can be inserted into it without damage on the
one hand and on the other hand, during such an insertion or
a subsequent transport, handling or the like, the loop
surrounding the goods does not tear or become otherwise
damaged.
In the same way, it is frequently necessary to provide
tubular packaging materials in which compressible or
resilient objects must be packaged, as far as possible, in
their most compressed form, in order on the one hand to keep
the space requirement of these packages as small as possible
and, on the other hand, to ensure that the packaged goods
are not compressed and decompressed unnecessarily frequently
during transport and thus possibly results in material
fatigue. It seems particularly important in this context
that the packaging material is not stressed by the tensile
stress exerted by the resilient goods packaged therein beyond
its stretching ability or elasticity and tears, or the
tubular packaging material is damaged when the goods to be
packaged are inserted. To date, plastic films or bands, which
can be produced in different designs and can also be
manufactured to suit the respective requirements, have been
considered to be most suitable for this purpose. For
environmental reasons, the aim is to replace plastic
packaging as far as possible with packaging made from
materials made from renewable raw materials and in particular
biodegradable raw materials. Recently, there has been
increased research into producing special papers, in
particular kraft papers, which meet a wide range of
requirements with regard to durability, elasticity, moisture
resistance and the like in order to replace plastic
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packaging. Particularly in cases where annularly closed
tubes, bands or loops have to be used as packaging materials,
there is the problem that packaging consisting of paper, for
example, is produced from a flat paper web, which web must
be glued or closed in some way to form the ring or tube. If
this closure is only closed or formed after the goods to be
packaged have been inserted therein, the time required until
a formed adhesive point has hardened or dried or a
thermoplastic material has hardened may be too long for mass
production, so that by analogy with plastic packaging, it is
necessary to form this tube, ring or loop before introducing
the products to be surrounded thereby. In order that products
can be inserted into such a tube, ring or loop or into such
a band without destroying it, such packaging material or
packaging paper must not only have excellent elasticity in
the radial direction, i.e. in the circumferential direction
of the ring or loop, but also must not tear at the edges,
particularly when the objects are inserted.
The present invention therefore aims to provide a packaging
material made of an unbleached, optionally coated, kraft
paper, which does not tear both in the machine longitudinal
direction and the machine cross direction under high loading,
in particular a loading that stretches the paper, and remains
sufficiently elastic or resilient over time so that the items
packaged therein cannot fall out after a fairly long time
due to a loss of tension or elasticity of the packaging
material.
To solve this problem, the packaging material according to
the invention is substantially characterized in that the
kraft paper contains at least 90 % primary cellulose,
containing at least 80 %, preferably at least 85 %, in
particular at least 88 % cellulose with a length-weighted
mean fibre length according to ISO 16065-2:2014 between 2.0
mm and 2.9 mm and less than 5 %, preferably less than 4.5 %,
in particular less than 4.2 % fillers as well as cationic
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starch and other process aids, that the primary cellulose is
contained in the form of beaten cellulose, in particular,
high-consistency beaten cellulose having a Schopper-Riegler
degree of beating according to ISO 5267-1:1999 between 13
SR and 20 SR, that the packaging material has strain ratio
MD/CD of the kraft paper at break according to ISO 1924-
3:2005 of > 1.1, a tear length in the machine direction
according to ISO 1924-3:2005 of >10 km, a tear index in the
cross direction of the kraft paper according to ISO 1974:2012
is >16.0 mN.m2/g and that the kraft paper is optionally
coated on at least one side with a coating material.
Since the packaging material contains at least 90 % primary
cellulose, containing at least 80 %, preferably at least
85 %, in particular at least 88 % cellulose with an average
length-weighted fibre length according to ISO 16065-2:2014
between 2.0 mm and 2.9 mm and contains less than 5 %,
preferably less than 4.5 %, in particular less than 4.2 %
fillers as well as cationic starch and other process aids,
it is possible to provide an unbleached kraft paper with an
extremely tear-resistant structure and in particular due to
the narrow length distribution of the fibre lengths of the
primary cellulose used, it is possible to achieve excellent
homogeneous paper properties in both the machine direction
and in the cross direction. Due to its durability and its
ability to be (micro)creped in a Clupak system, such
unbleached kraft paper can also be used safely and reliably
for the packaging of sharp-edged objects or heavy materials,
such as cement or beverage bottles. Since it furthermore
contains less than 5 %, preferably less than 4.5 %, in
particular less than 4.2 % (the stated percentages are always
to be understood as percent by weight in the context of the
present invention) of fillers as well as cationic starch and
process aids, it is possible, at the same time, to obtain a
durable but not excessively stiff unbleached kraft paper in
which high percentages of starch, in particular cationic
starch, can be used due to the lignin remaining in the kraft
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paper and the hemicelluloses remaining in the kraft paper
and the associated high numbers of negative charges. Since
an unbleached kraft paper produced in this way is not
excessively stiff, but is extremely elastic, it is possible,
particularly when loops, bands, sleeves or tubes are made
from this packaging material, to securely and reliably
enclose the objects packaged therein without there being any
need to fear that these will slip out of the packaging
material in an unintentional manner, whereby when producing
such tubes, bands or loops, care must be taken to ensure
that the unbleached kraft paper has greater elasticity in
the winding direction of the loop than in the cross
direction of the loop. Since the packaging material is formed
in such a way that the primary cellulose is contained as
beaten cellulose, in particular cellulose beaten with high
consistency, with a degree of beating according to Schopper-
Riegler according to ISO 5267-1:1999 between 13 SR and 20
SR, it is still possible to break up existing fibre
agglomerates, such as strips and splinters, whereby a uniform
sheet or particularly homogeneous kraft paper can be formed,
in which an optimized combination between flexibility of the
fibre and tear index in the cross direction can be achieved.
It is unnecessary to state that by increasing or by high- or
low-consistency beating of paper, both the tear length and
the air permeability of the paper can be adjusted, wherein
however the latter is not important in the present case,
especially when coatings are optionally applied, since a
neither a rapid filling of closed bags made of the packaging
material according to the present invention should be
achieved nor does the air permeability in any other way bring
about advantageous or negative properties for packaging made
from the packaging material.
The packaging material can also consist of 100 % primary
cellulose. Since the packaging material, in particular the
unbleached kraft paper, consists of 100 % primary cellulose,
it is possible to safely avoid negative influences on the
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end product, which originate, for example, from recycled
cellulose as well as from cellulose obtained from waste paper
and, in particular, a reduced strength or elongation at break
of the packaging material mostly caused by waste paper or
recycled cellulose can thereby be avoided. In connection
with the present invention, it is essential that the
elongation at break or the strain ratio, the tear length in
the machine direction and the tear index in the cross
direction can be kept high and as constant as possible over
time in order to provide consistent material properties with
which it is possible to produce tubular packaging or sleeves
or loops in which heavy or sharp-edged objects can be
packaged and/or wrapped and can be stored for a fairly long
time without any risk that the unbleached kraft paper will
tear and the packaging manufactured therewith will
deteriorate.
Since the unbleached kraft paper of the packaging material
has a strain ratio MD/CD according to ISO 1974:2012 of >1.1
it is ensured that its elasticity in the machine direction
(MD) is greater than that in the cross direction and the
packaging material is therefore not only stretchable in the
MD and CD direction but can be subjected to a greater change
in length in one direction than in the other without having
to fear destruction, in particular tearing, of the packaging
material.
The fact that the strain ratio MD/CD of the kraft paper is
>1.1 in accordance with ISO 1974:2012 further ensures that
even objects that do not have a homogeneous or even and
smooth surface can be packaged safely and reliably in this
packaging material based on unbleached, optionally coated
kraft paper, since the paper substantially encloses the
packaged goods on all sides after it has returned to its
original shape from its expanded shape due to the insertion
of the goods and is also able to securely and reliably hold
goods with uneven surfaces. At the same time, the stretch is
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sufficiently large so that the products can be inserted into
the packaging material without damaging it, in particular
can be inserted into tubular sleeves shaped from this
optionally coated paper or packaging material and it is
furthermore ensured that after introduction of the materials
and stretching of the paper, the paper is returned to its
original shape and tightly encloses the packaged objects, so
that there is no need to fear that packaged objects can fall
out, for example, from tubular or ring-shaped packaging made
from the packaging material according to the invention.
Furthermore, it has been shown that if the strain ratio MD/CD
of the kraft paper according to ISO 1974:2012 is >3, no
further improvement in the properties of the packaging
material required for packaging heavy objects can be
achieved.
Since the tear length in the machine direction of the kraft
paper is >10 km in accordance with ISO 1924-3:2005 it is
further ensured that the machine strength in the longitudinal
direction of the packaging material is so great that even
if, for example, tubular or ring-shaped packaging was made
therefrom, even non-flexible objects can be inserted into
the interior of this packaging material thus shaped without
needing to fear any unintentional tearing of the kraft paper.
Since the tear index in the cross direction of the kraft
paper according to ISO 1974:2012 is furthermore >16.0
mN.m2/g, it is ensured that there is no risk of tearing of a
free edge of the packaging material, even in the event of
unintentionally high loads on the edge of the packaging
material and in particular if tubular or ring-shaped products
are manufactured from this packaging material, such as loops
or sleeves, there is no need to fear tearing of the packaging
material and therefore destruction of the packaging when the
goods to be packaged are inserted.
Since the packaging material is formed such that a tear index
in the cross direction (CD) of the kraft paper according to
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ISO 1974:2012 is >16.0 mN.m2/g, the packaging material
substantially consisting of unbleached, optionally coated
kraft paper, can also be severely stressed at its edges
without needing to fear any tearing or further tearing of
the paper from the edge to the centre. Finally, it can
thereby be prevented that even if a small crack is formed in
the packaging material, this is not unintentionally
enlarged.
In connection with the present invention, the term "packaging
material" is understood to mean substantially unbleached
kraft paper, which can optionally be coated on one or two
sides. Furthermore, it can have one or more layers of kraft
paper.
According to a further development, the packaging material
can also consist of 100 % primary cellulose. Since the
packaging material, in particular the unbleached kraft
paper, consists of 100 % primary cellulose, it is possible
to more reliably avoid negative influences on the end
product, which originate, for example, from recycled
cellulose as well as from cellulose obtained from waste paper
and in particular, a reduced strength or elongation at break
of the packaging material mostly caused by waste paper or
recycled cellulose can be avoided. In connection with the
present invention, it is essential that in particular the
elongation at break or the strain ratio, the tear length in
the machine direction and the tear index in the cross
direction can be kept high and as constant as possible over
time in order to provide consistent material properties,
with which it is possible to manufacture tubular or ring-
shaped packaging or sleeves in which heavy or sharp-edged
objects can be packaged and/or wrapped therewith and can be
stored for a fairly long time without there being any need
to fear any tearing of the unbleached kraft paper and
deterioration of the packaging produced therewith.
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As corresponds to a further development of the invention,
since the packaging material is formed such that it has a
starch content of 0.5 % to 2.2 % of the kraft paper, in
particular 0.7 % to 2.0 %, it is possible to keep the
excellent mechanical properties of the unbleached kraft
paper, the surface smoothness of at least one side of the
kraft paper, high and keep the Bendtsen roughness low and
thus provide excellent printability of this at least one
side of the packaging material. In the present context, an
attempt is made at the same time to configure only one side,
in particular the side facing away from the machine or "top
side" of the paper, to be correspondingly smooth in order to
make the adhesion to the inside of tubular or ring-shaped
packagings, i.e. the side facing away from the "top side",
made of the packaging material according to the present
invention as great as possible in order to prevent as far as
possible any loss of the items packaged therein due to
slipping out.
According to a further development of the invention, the
packaging material is configured such that the primary
cellulose consists of a mixture consisting of at least 80 %
softwood cellulose, preferably at least 90 % softwood
cellulose, in particular at least 95 % softwood cellulose
having a length-weighted mean fibre length according to ISO
16065-2:2014 of at least 2.0 mm, preferably at least 2.2 mm
and the remainder of hardwood cellulose having a length-
weighted mean fibre length according to ISO 16065-2:2014 of
at least 1.0 mm. Due to the predominant amount of softwood
cellulose having a length-weighted mean fibre length
according to ISO 16065-2:2014 of at least 2.0 mm and the
remainder of hardwood cellulose having a length-weighted
mean fibre length according to ISO 16065-2:2014 of at least
1.0 mm, the strength property can be positively influenced
by the softwood cellulose and the smoothness of at least one
side of the unbleached kraft paper can be positively
influenced by the hardwood cellulose, and by means of a
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targeted choice of the cellulose composition, a packaging
material can be provided having both excellent mechanical
properties, in particular elongation at break, and also
sufficient smoothness, which provides good printability.
Furthermore, with such a choice of cellulose mixture, in
particular the high contents of softwood cellulose, it can
be ensured that an unbleached packaging material thus
produced has a large tear length in the machine direction,
whereby a particularly resilient packaging material can be
provided, in which objects having a higher weight can also
be stored can be packed with a higher weight without the
packaging necessarily needing to have a bottom and/or top
surface.
Since, as corresponds to a further development of the
invention, the packaging material is configured so that it
has a tensile strength index in the machine direction
according to ISO 1924:3: 2005 of >105 Nm/g, preferably at
least 115 Nm/g, a non-destructive packaging of even heavy or
sharp-edged objects in the packaging material according to
the present invention is ensured. Due to the tensile strength
index according to the invention in the machine direction it
is further ensured that when producing, for example, tubular
packaging or loop-shaped or sleeve-shaped packaging from the
packaging material according to the invention, it is possible
to provide sufficient load-bearing capacity of the packaging
material, with the result that even heavy objects can be
safely fitted into such a loop or sleeve made of the
packaging material and furthermore there is no need to fear
tearing of the material.
In the same way, as corresponds to a further development of
the invention, the packaging material has a TEA index in the
machine longitudinal direction according to ISO 1924-3:2005
greater than 5.0 J/g, preferably greater than 5.5 J/g. Since
the TEA index in the machine longitudinal direction is
greater than 5.0 J/g, it is possible to provide a packaging
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material that is extremely elastic and stretchable without
resulting in any tearing of the packaging material. The TEA
index is understood as the tensile energy absorption index
according to ISO 1924-3:2005.
In order in particular to avoid tearing or bursting of
the packaging material according to the invention from the
edges to the centre, the invention is further developed such
that the packaging material has a bursting strength according
to ISO 2758:2014 of greater than 750 kPa, preferably greater
than 770 kPa, particularly preferably greater than 800 kPa.
According to the invention, the bursting strength is adjusted
or increased, inter alia, by a combination of the following
measures: use of cellulose from softwood, a low filler
content and a high proportion of, for example, cationic
starch. Furthermore, beating, in particular low-consistency
beating, also has a positive influence on the bursting
strength.
Since, as corresponds to a further development of the
invention, the packaging material is designed such that it
has a wet strength index according to ISO 3781:2011 in the
machine direction of the kraft paper of at least 14.0 Nm/g,
in particular 14.5 Nm/g, particularly preferably at least
15.0 Nm/g, it is possible to provide in particular tubular
or ring-shaped packaging with the packaging material, which
is also suitable for use in moist environments. Particularly
if, for example, food packagings or loops that enclose and
hold together a plurality of foods or foodstuffs are
manufactured from the packaging material, contact with
condensation, moisture or a damp environment cannot be
avoided, so that a high wet strength or a high wet strength
index is desirable, but without permanent wet strength agents
or large quantities thereof, needing to be used in the
production of the packaging material substantially
consisting of unbleached kraft paper. The wet strength index
according to ISO 3781:2011 in the machine direction can be
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further improved by providing a coating on one or both sides
of the packaging material.
Surprisingly, such a high wet strength can also be achieved
with a high dry basic strength with the packaging material
according to the present invention. In order to achieve high
wet strength, larger amounts of auxiliary materials, such as
wet strength agents, usually have to be used, which in turn
cause problems when recycling the packaging material to be
produced, which substantially consists of unbleached kraft
paper. Since in the packaging material according to the
invention, which substantially consists of unbleached kraft
paper, the dry strength expressed by the tensile strength
index in the machine direction is >105 Nm/g, sufficient wet
strength can surprisingly be achieved very resource-
efficiently without or by only adding very small amounts of
wet strength agents.
In the present case, wet strength agents are understood to
mean water-miscible polymer solutions in the processing
state, which are primarily produced from polyamines and
epichlorohydrin derivatives. Furthermore, products based on
urea-formaldehyde or melamine-formaldehyde are conceivable,
but are preferably no longer used for reasons of avoiding
health risks. When the wet strength agents react with
cellulose fibres, cross-links form between the fibres, which
lead to an increased water resistance of the corresponding
paper thus produced. However, the hydrophobic chain thus
formed prevents easy or successful recycling of a paper
treated with these wet strength agents. Returning used
packaging paper to a cellulose cycle is therefore not
possible or can only be achieved to a limited extent by using
high temperatures and/or additional chemicals and additives.
It is therefore desirable to keep the amount of wet strength
agents used as low as possible, which surprisingly can be
achieved with kraft paper or packaging material according to
the invention.
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According to a further development of the invention, the
packaging material is designed such that a coating material
selected from a polyolefin, in an amount corresponding to
1/15 to 1/6 of the grammage of the kraft paper, is applied
to at least one side. By applying to at least one side of
the packaging material a coating material selected from a
polyolefin or polylactic acid (PLA), in an amount
corresponding to 1/15 to 1/6 of the grammage of the kraft
paper contained in or forming the packaging material, it is
possible, on the one hand, to further improve the wet
strength of the packaging material without the excellent
mechanical properties deteriorating. On the other hand, by
applying such small amounts of a coating material to at least
one side of the packaging material, it can be ensured that
loops, rings, tubes, sleeves or the like can be formed from
the packaging material by superimposing free end regions of
the packaging material and a closed ring can be formed by
heat sealing the at least one thermoplastic polyolefin layer
or the polylactic acid layer.
Finally, by applying an amount corresponding to 1/15 to 1/6
of the grammage of the kraft paper to a polyolefin coating
material or polylactic acid coating material, it can be
ensured that a packaging material thus produced is both
decomposable and, due to the small amount of polymer, is not
harmful to the environment.
By selecting, as corresponds to a further development of the
invention, the polyolefin from high-density polyethylene
(HDPE), low-density polyethylene (LDPE) or polypropylene
(PP), coatings which are both stable and do not impair the
mechanical properties of the kraft paper forming the basis
of the packaging material can be formed.
Polyolefin coating materials having densities in the range
of 900 to 950 kg/m3 as well as softening or melting
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temperatures between 125 and 150 C have proven to be
particularly suitable.
According to a further development of the invention, the
packaging material is further developed such that a laminate
consisting of several layers of kraft paper and several
layers of coating material is formed. By forming a laminate
from several layers of kraft paper and several layers of
coating material, it is possible to provide both resilient
and extremely durable packaging materials. Such packaging
materials can be used, for example, as packaging bands, in
particular as a replacement for plastic bands surrounding
packets, packages or similar. Furthermore, such laminates
can not only be used on existing industrial packaging
machines, but due to the particularly high tear strength of
the laminate, these can also be stapled without there being
any need to fear any tearing out of the staples or tearing
of the laminate due to the material weakening that has taken
place.
Since, as corresponds to a further development of the
invention, the laminate has at most 5 layers of the kraft
paper, such as 4 layers for example, more favourably 3
layers, preferably 2 layers of the kraft paper and at most
6 layers of the coating material, such as 5 layers, for
example, more favourably 4 layers, preferably 3 layers of
the coating material, on the one hand, it is possible to
produce laminates that are optimally adapted to the thickness
requirements of industrial packaging machines. On the other
hand, by using a single grammage of the kraft paper, a large
number of different bands, sleeves, loops or the like can be
produced from the laminate, which in particular reduces
downtimes and necessary adjustments to the paper machine. As
a result, the kraft paper forming the basis of the packaging
material can be produced more economically.
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According to a further development of the invention, each
layer of coating material located between two layers of kraft
paper has an amount that corresponds to 1/15 to 1/9 of the
grammage of the kraft paper, and a layer of coating material
forming an outer side of the laminate has an amount which
corresponds to 1/11 to 1/6 of the grammage of the kraft
paper. With such a design, the amount of coating material
used can be minimized, since each layer of coating material
located between two layers of kraft paper only has to ensure
that the two layers of kraft paper hold together and can
therefore be formed from a smaller amount of the coating
material. In contrast, each outer layer of the coating
material must be configured to be sufficiently thick that it
must ensure a secure and durable heat seal of, for example,
two ends of the packaging material.
The invention further aims to design or provide a sleeve
from the packaging material according to the present
invention, with which sleeve it is possible to package or
enclose a plurality of heavy, unconnected products and to
transport them without there being any need to fear any
tearing of the packaging material.
In order to achieve this object, according to the invention,
a sleeve is provided from the packaging material of the
present invention, which is configured such that it is formed
from an optionally coated, at least single-layer web of the
packaging material which is closed in the cross direction,
in particular crimped, glued, preferably double-glued,
welded, stapled, sewn or riveted in the cross direction,
substantially made of unbleached kraft paper, and that a
machine direction of the paper web in the packaging material
forms a circumferential direction of the sleeve. Due to the
fact that this sleeve is formed from the optionally coated,
at least single-layer web of packaging material which is
closed in the cross direction, in particular crimped, glued,
preferably double-glued, welded, stapled, sewn or riveted,
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substantially made of unbleached kraft paper, it is possible
to provide the greater elongation that the unbleached kraft
paper has in the machine direction in the circumferential
direction of the sleeve, the band, the loop or the tubular
packaging, so that due to the excellent elasticity of the
packaging material in the machine direction, a plurality of
objects when inserted into the sleeve or into the packaging
material glued into a ring does not tear or further tear the
packaging material. Since it is thereby possible to enclose
a plurality of objects with the sleeve, several objects that
are similar or different from one another can naturally be
enclosed and held together without having to provide
packaging that completely surrounds the objects.
By arranging the packaging material in the finished sleeve
in such a way that a machine direction of the packaging
material forms a circumferential direction of the sleeve,
the stretch properties in the machine direction introduced
by the manufacturing process of the packaging material can
be used to ensure that the objects to be packaged or enclosed
can be inserted into a sleeve that has already been glued
into a ring using the stretch properties of the packaging
material, without there being any need to fear tearing of
the sleeve and can be held firmly in this ring after they
have been inserted due to the resilience of the packaging
material. Furthermore, a band formed from this packaging
material, in particular a laminate made from this packaging
material, can also be used instead of plastic bands, which
are used, for example, to close packages, to secure objects
from loss and the like.
By connecting the packaging material thus to form a ring or
a loop or sleeve such that it encloses a plurality of objects
in the machine direction of the paper web, it is furthermore
possible to insert the plurality of objects into such a
sleeve without there being any fear that the band will tear
in both the cross direction and longitudinal directions,
even at the edges of the sleeve. It is also unnecessary to
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point out that such a sleeve constitutes an extremely paper-
saving type of packaging with which objects can be packaged
and held together safely and reliably.
Since the sleeve encloses at least two objects that are the
same or different from one another, it is ensured that
containers of any size can be formed, which at the same time
due to the strain ratio MD/CD of the optionally coated kraft
paper in accordance with ISO 1924-3:2005 of >1.1 to about 3
as well as the tear index in the cross direction according
to ISO 1974:2012 of > 16.0 mN.m2/g can be reliably inserted
into the sleeve or the tubular product without there being
any fear of tearing or tearing-out of the edges of the paper.
Objects that are heavy or have a large length or height
compared to the width of the sleeve can also be packaged in
such a sleeve without there being any fear of tipping or
subsequent tearing of the sleeve. This is
because, due to
the material properties of the packaging material, the
objects can be tightly enclosed and therefore, even if one
or more objects tip, there is no need to fear any tearing
and subsequent tearing-through of the sleeve. Such a sleeve
can also be used to close, for example, a box or the like.
The sleeve can be configured such that the plurality of
objects are arranged in several rows, in a circle or to form
a dense package in the sleeve. With such an arrangement of
the enclosed objects, for example, conventional beverage
packs comprising two, six or even twelve bottles can be
surrounded by a band according to the invention or, for
example, food products such as courgettes or bananas can be
arranged in a sleeve or even, for example, several foam
elements that are identical to one another, such as foam
cushions or rods made of metal or wood, can be arranged
inside such a sleeve.
According to a further development of the invention, the
sleeve is configured so that it is subjected to tensile
Date Recue/Date Received 2024-04-08
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18
loading by the enclosed objects, in particular with a tensile
stress that is smaller than an elongation at break in the
machine direction (MD) measured according to ISO 1924-3:2005
of the optionally coated paper web. Due to the tensile
loading or tensile stressing of the objects packaged inside
such a sleeve, it is ensured that an object does not
accidentally fall out of the sleeve, with the result that
subsequently the hold of the remaining products could no
longer be ensured.
In order to provide sufficient elasticity of the packaging
material or to be able to provide sufficient resilience of
the same, the packaging material is substantially configured
such that the elongation at break in the machine direction
(MD), measured according to ISO 1924-3:2005, of the paper
web is >8 %. Kraft papers, which have an elongation at break
of the paper web of >8 % in the machine direction, have
proven themselves in standard packaging materials, such as
heavy-duty bags and the like, which are subjected to severe
loading in the MD direction, and surprisingly it has been
shown that sleeves made from such material are able to hold
products packaged therein safely and reliably due to the
excellent resilience of this material, without there being
any fear of the products slipping or falling out of the
sleeve or tearing or there being any fear of tearing of the
sleeve when inserting the products.
According to a further development of the invention, the
sleeve, band or the like is configured such that it consists
of a laminate consisting of several layers of kraft paper
and several layers of coating material, such as at most 5
layers of kraft paper, for example 4 layers, more favourably
3 layers, preferably 2 layers of the kraft paper and at most
6 layers of the coating material, such as 5 layers, more
favourably 4 layers, preferably 3 layers of the coating
material. By using a laminate, the sleeve, band or loop can
be used as a replacement for conventional plastic bands
Date Recue/Date Received 2024-04-08
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19
without there being any need to fear tearing of the laminate.
Unintentional loosening of a connection point of two ends of
the laminate is also reliably prevented and this is
regardless of whether the band or the sleeve is heat-sealed,
stapled, crimped or connected to one another in any other
way.
A further aim of the present invention is to provide a method
for forming a sleeve from the packaging material according
to the invention, whereby, due to the conventional
manufacturing processes, the problem essentially lies in the
fact that as a result of corresponding treatments, in
principle a paper web has greater stretching properties in
the machine direction than in the cross direction. It is
true that isotropic papers are already known which have the
same properties in the longitudinal and cross directions,
these can only be produced to a limited extent on large paper
machines and in particular these papers usually have at least
slightly inferior properties in the cross direction.
In order to be able to optimally utilize the favourable
properties of the packaging material according to the
invention in a sleeve, the method according to the invention
is formed such that a length of the packaging material
slightly exceeding a circumference of the sleeve to be formed
is cut from a web of the packaging material substantially
consisting of unbleached kraft paper which is unrolled in
the machine longitudinal direction, the cut length of the
packaging material is pivoted through 900, those two free
edges of the cut length, which run in the cross-machine
direction when the web of packaging material is unrolled,
are folded over one another and closed into a tube and that
a plurality of sleeves are separated from the closed tube or
prepared for separation, in particular perforated, scratched
or marked. Due to the non-existent possibility or economic
senselessness of performing cuts or a large number of cuts
in the paper in the machine longitudinal direction in a
Date Recue/Date Received 2024-04-08
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running paper web on a paper machine, the process is
essentially carried out such that only a length of the
packaging material is cut off from an unrolling web of the
packaging material, which length substantially corresponds
to the circumference of the sleeve to be produced. Naturally,
a certain excess length can be provided here, which must be
present as an overlap of the material during a subsequent
closure of the layer of packaging material to form a tube or
possibly to form a single sleeve. After cutting off the
corresponding length, a tube can either be formed directly
from the cut length, wherein the paper is then folded such
that in principle the cross direction, i.e. the width of the
web of packaging material, forms the circumferential length
of the tube, or however, the cut piece of packaging material
can be directly turned by 900 and subsequently glued,
crimped, riveted, sewn or similar into a tube. In a final
step, it is now necessary to separate corresponding pieces,
which correspond to the width of the sleeve, from the tube
thus formed. The separation can be done by cutting, punching,
tearing off and the like, wherein perforations, marking
lines, pre-punched areas or the like can be carried out for
this purpose either beforehand, in which case this is either
carried out directly or at the end customer, depending on
the intended use and final use of the sleeve. It makes sense
that those pieces that form a large number of sleeves are
not separated in advance, since, for example, printing is in
principle easier if larger areas can be printed accordingly
at the same time.
According to a further development of the method according
to the invention, the method can be carried out such that
the pivoting of the cut length of the packaging material by
90 is carried out before or after folding over and closing
those two free edges of the cut length that run in the cross-
machine direction during unrolling of the web of packaging
material. Here, as stated, it is irrelevant whether the
pivoting of the cut length of the packaging material by 90
Date Recue/Date Received 2024-04-08
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21
is carried out before or after folding over one another to
close the two free bands of the cut length.
The packaging material according to the invention can, as
corresponds to a further development of the invention, be
used as a sleeve or as a band, in which case it should not
go unmentioned that conventional sacks and the like can
naturally also be made from this packaging material which
however, only seems meaningful for high-performance products
due to the special material properties.
The invention is further explained hereinafter using
exemplary embodiments and drawings. In the figures:
Fig. 1 shows a schematic diagram of possible types of
connection of a packaging material according to the invention
to form a sleeve or loop; and
Fig. 2 shows a schematic diagram of the process sequence for
producing a sleeve from the packaging material according to
the invention.
In detail, Fig. la) shows schematically a sleeve or loop 1
shows which sleeve 1 is configured such that two free ends
2, 3 of the packaging material forming the sleeve 1 overlap
and at least one connection is formed in the area of the
overlap 4.
With such a packaging material, which is in particular
configured as a loop or sleeve, it is therefore possible to
hold a plurality of objects of the same or different design
by the sleeve 1, without having to use, for example, an
additional plastic packaging that extends over the entire
package of objects. The area of the connection 4 can have
any type of connection, such as for example, flat adhesive
bonding (see Fig. lb)), punctuate adhesive bonding (see Fig.
1c)), or any type of connection, such as sewing (see Fig .
Date Recue/Date Received 2024-04-08
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22
1d)), crimping, large-area gluing or thermal sealing or the
like can be used. A sleeve thus formed is then pulled over
the objects to be held together, whereby they are held
together tightly or firmly due to the resilience of the
material.
Figure lb) shows a perspective longitudinal view of an
endless tube formed from the packaging material according to
the invention, which endless tube is intended for forming a
plurality of sleeves 1. In the embodiment shown in Fig. lb),
the free ends 2, 3 of the packaging material are again
arranged in an overlapping manner and the connection area 4
is adhesively bonded over the entire surface, as shown by a
dashed area. The dashed lines 11 in Fig. lb) indicate
possible dividing lines for separating individual sleeves 1.
Figure 1c) shows a representation of an endless tube made of
the packaging material according to the invention in a
similar manner to that in Fig. lb), wherein instead of a
large-area adhesive bonding, in the overlap area 4, punctuate
adhesive points are implemented which are in particular
arranged in two rows which are offset from one another.
Needless to say, any other type of adhesive bonding can
naturally be selected, whether it is in two individual
adhesive lines, one adhesive line or the like. If a packaging
material that is coated on one or two sides is used, the
adhesive bonding can preferably be achieved by thermal
sealing or welding of the coating made of a thermoplastic
material.
In Fig. 1d), in which a diagram as in Fig. lb) of the
packaging material according to the invention was also
selected, it is shown that the free ends 2, 3 of the packaging
material forming the endless tube are sewn to a second layer
of the packaging material 8, as indicated schematically by
the seam lines 6.
Date Recue/Date Received 2024-04-08
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23
With such sleeves 1, it is now possible to captively pack a
wide variety of objects together and, in particular, to
ensure that, even when heavy objects, such as metal rods or
the like, are packed, any tearing of the packaging material
8 is avoided. If such a sleeve 1 is pulled over objects to
be packaged, in particular heavy or hard objects, it is
possible to ensure that as a result of the resilience of the
unbleached kraft paper forming it, in particular due to the
elongation at break, tensile strength or even the tear
resistance index, if a small tear should be formed in the
packaging material 8 forming the sleeve 1, this does not
tear any further and, moreover, the sleeve 1 thus formed
contracts to such an extent after stretching that any
slipping out of the objects packaged therein after the
packaging has been completed can be prevented. In addition,
due to the special configuration of the packaging material
8, a certain static friction can also be exerted on the
objects packaged therein, which ensures that the objects are
immovably accommodated inside the sleeve 1 and that any
slipping out of one or more of the objects is safely
prevented. The static friction mentioned here can be exerted
not only by the sleeve 1, but also, for example, by the
surface of the objects packaged therein.
In Fig. 2, in which the reference numerals from Fig. 1 are
retained, the process sequence for producing a sleeve from
the packaging material 8 according to the invention is shown
schematically.
In Fig. 2, 7 denotes a roll of the packaging material 8, as
it is rolled up from production from a paper machine onto a
reel. From the roll 7 of the packaging material 8, the
packaging material 8 is unrolled in the direction of the
arrow 9, which arrow 9 at the same time corresponds to the
machine direction of the machine on which the packaging
material 8 was produced, for example a paper machine. When
a sufficient length of the packaging material 8 has been
Date Recue/Date Received 2024-04-08
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24
unrolled, this is cut along the width of the packaging
material 8, as indicated by the dashed line 10. In a second
step, this cut length of the packaging material 8 is turned
by 900, as indicated by arrow 11, in order to have the
original machine direction 9 now arranged in the cross
direction of the cut piece of the packaging material 8, as
again indicated by arrow 9. The cut piece of packaging
material 8 here has a length L in the machine direction of
the roll of packaging material 8, which substantially
corresponds to the circumference of a sleeve 1 to be formed
from this packaging material 8, wherein depending on the
subsequent method of connecting the packaging material 8
either a small excess length is selected in order to be able
to glue the ends on top of each other, in particular when
using a packaging material coated with a thermoplastic
material, such as PE or PLA, to be able to seal them
thermally, or in principle exactly the circumferential
length of the sleeve is selected if the connection is made
by crimping, stapling, sewing or the like. In a third step,
a tube is formed from this separated length of packaging
material 8, wherein any conventional tube forming process
can be used here, as indicated in the figure. In the present
case, the tube is formed such that the free ends 2, 3 of the
packaging material 8 overlap each other by a distance or a
length 4 in order to subsequently be able to glue the free
ends 2, 3 together, for example, in particular even to be
able to glue them twice. The free ends of the packaging
material 8 are here, as in Fig. 1, designated by the
reference numerals 2 and 3 and the overlapping piece by 4,
as shown for example in Fig. la. The tube thus produced can
either be printed or subjected to any further treatment,
such as perforating, marking, punching or, in particular,
cutting, in order to produce the sleeves 1 according to the
invention from the material.
It is unnecessary to note that the second step of the process
of turning the packaging material 8 by 90 can also take
Date Recue/Date Received 2024-04-08
CA 03234736 2024-04-08
place after forming the tube. In any case, the packaging
material 8 must be connected to one another along the edges
2, 3 in order to have the favourable material properties,
which result from the machine direction of the production of
the kraft paper, available in the circumferential direction
of a finished sleeve 1.
With regard to the optional process steps, such as printing,
perforating or the like, it should be noted that these can
be carried out before or after each step following separation
of the web of packaging material 8 from the reel. Thus, it
can be favourable to print immediately on the separated piece
of packaging material and only then form a tube from the
packaging material 8.
The sleeve or loop 1 can not only be designed in one colour,
but can also be printed in multiple colours, provided with
company names, logos and the like, and it can also have a
one-sided or two-sided coating in order, for example, to
improve the moisture resistance of the packaging material 8.
Finally, it can also have more than one layer of unbleached
kraft paper. A laminate can thus be formed consisting of
more than one layer of the kraft paper, with respectively
one layer of the coating material between the individual
kraft paper layers and an outer layer of the coating material
in each case. The grammages of the individual coating
material layers and also the grammages of the individual
kraft paper layers can also differ from one another. In this
case, it should be noted that the essential properties of
the sleeve 1 must not be changed and neither the elongation
at break, the bursting strength, the tear length, etc. are
changed compared to an optionally coated single-layer paper
sleeve.
Finally, it is unnecessary to point out that with a sleeve
1 according to the invention not only heavy and hard objects
or plastic containers can be held together, but also, for
Date Recue/Date Received 2024-04-08
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26
example, socks can be surrounded, foods such as bananas,
courgettes, cucumbers or the like can be connected to one
another or boxes can be closed. Also, for example, goods
packaged in cans or food, boxes and the like can be connected
to each other to form containers.
Furthermore, the invention is explained in more detail
hereinafter by reference to exemplary embodiments.
Example 1: Production of a packaging material based on
unbleached kraft paper with a grammage of 82 g/m2
Process description:
An unbleached cellulose consisting of 100 % primary cellulose
from softwood (mixture of spruce and pine) with a Kappa
number of 51 was first subjected to high-consistency beating
with a beating capacity of 230 to 240 kWh/t, wherein a degree
of beating of the cellulose after high-consistency beating
was 17 SR. This cellulose was then subjected to low-
consistency beating with a beating capacity of 90 to 100
kWh/t. The following auxiliary materials were added to the
constant part of the paper machine. Here the pH was adjusted
to a pH of 6.8 to 7.0 with aluminium sulphate, cationic
starch having a degree of cationization DS of 0.03 was added
absolutely dry in an amount of 17 kg/t paper, alkenyl
succinic anhydride in an amount of 0.8 kg/t dry kraft paper
was added as sizing agent and 10 kg/t PAAE was used as wet
strength agent. Furthermore, no fillers were added. The
consistency of the cellulose at the headbox was 0.19 %. The
dewatering was carried out on a Foudrinier wire section and
with a press section with three nips, wherein one of the
presses can be a shoe press, wherein the line pressure at
the three nips was 60 kN/m, 90 kN/m and 500 kN/m respectively
(in the shoe press). Before the still wet paper was fed to
the Clupak system, it was subjected to contact drying,
conventional drying using hot air at 167 C, then pre-dried
in a slalom drying section and treated in a Clupak system
Date Recue/Date Received 2024-04-08
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27
with a differential speed of -7.9 % and finally dried to a
final residual moisture content of 7.5 %.
The kraft paper can be used as such for the production of
bands, loops or sleeves and the paper properties described
in the following table were measured in this kraft paper.
The kraft paper thus produced would have the following
properties:
Table 1:
Paper Standard Unit Direction Result
property
Grammage ISO 536:2019 g/m2 82
Tensile ISO 1924-3:2005 kN/m MD 8.9
strength
Tensile ISO 1924-3:2005 Nm/g MD 109
strength
index
Tensile ISO 1924-3:2005 kN/m CD 5.4
strength
Tensile ISO 1924-3:2005 Nm/g CD 66.3
strength
index
Elongation ISO 1924-3:2005 % MD 9.6
at break
Elongation ISO 1924-3:2005 % CD 8.6
at break
Tensile ISO 1924-3:2005 J/m2 MD 578
energy
absorption
Tensile ISO 1924-3:2005 J/m2 CD 405
energy
absorption
Bendtsen ISO 8791-2:2013 ml/min Upper 867
roughness side
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28
Bendtsen ISO 8791-2:2013 ml/min Lower 1250
roughness side
Bursting ISO 2758:2014 kPa 781
strength
Wet ISO 3781:2011 Nm/g MD 15.2
strength
index
Tear index ISO 1974:2012 mN.g/m2 MD 14.2
Tear index ISO 1974:2012 mN.g/m2 CD 16.1
Strain ISO 1924-3:2005 - MD/CD 1.12
ratio
Tear ISO 1924-3:2005 Km MD 11.06
length
Example 2: Production of a packaging material based on
unbleached kraft paper with a grammage of 130 g/m2
Process description:
An unbleached cellulose consisting of 95 % primary cellulose
from softwood with a Kappa number of 41 and 5 % primary
cellulose from hardwood with a Kappa number of 40 was first
subjected to high consistency beating with a beating capacity
of 190 to 210 kWh/t, wherein the degree of beating of the
cellulose after high-consistency beating was 19 SR and this
cellulose was then subjected to low-consistency beating with
a beating capacity of 70 to 80 kWh/t. The auxiliary materials
were added into the constant part of the paper machine. The
pH was adjusted to a pH of 6.8 to 7.0 with aluminium sulphate,
cationic starch having a degree of cationization DS of 0.03
was added absolutely dry in an amount of 14 kg/t of paper
and alkenyl succinic anhydrides were used as the sizing agent
in an amount of 0.8 kg/t kraft paper absolutely dry.
Glyoxalated PAM with 10 kg/t absolutely dry kraft paper was
used as the wet strength agent. Furthermore, no fillers were
added. The consistency of the cellulose at the headbox was
Date Recue/Date Received 2024-04-08
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29
0.23 %.The dewatering was carried out on a Foudrinier wire
section and with a press section with three nips, wherein
one of these can be a shoe press, wherein the line pressure
at the three nips is 60 kN/m, 90 kN/m and 500 kN/m (in the
shoe press). The kraft paper is pre-dried and then treated
in a Clupak system with a differential speed of -8.6 % and
finally dried to an ultimate final moisture content of 7.5 %
The kraft paper can be used as such and the paper properties
described in the following table were measured with this
paper.
The kraft paper thus produced had the following properties:
Paper Standard Unit Direction Result
property
Grammage ISO 536:2019 g/m2 130
Tensile ISO 1924-3:2005 kN/m MD 16.2
strength
Tensile ISO 1924-3:2005 Nm/g MD 124.6
strength
index
Tensile ISO 1924-3:2005 kN/m CD 6.3
strength
Tensile ISO 1924-3:2005 Nm/g CD 48.5
strength
index
Elongation ISO 1924-3:2005 % MD 10.3
at break
Elongation ISO 1924-3:2005 % CD 8.5
at break
Tensile ISO 1924-3:2005 J/m2 MD 871
energy
absorption
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Tensile ISO 1924-3:2005 J/m2 CD 372
energy
absorption
Bendtsen ISO 8791-2:2013 ml/min Upper 1420
roughness side
Bendtsen ISO 8791-2:2013 ml/min Lower 1890
roughness side
Bursting ISO 2758:2014 kPa 812
strength
Wet ISO 3781:2011 Nm/g MD 16.1
strength
index
Tear index ISO 1974:2012 mN.g/m2 MD 12.1
Tear index ISO 1974:2012 mN.g/m2 CD 19.3
Strain ISO 1924-3:2005 - MD/CD 1.21
ratio
Tear ISO 1924-3:2005 km MD 12.7
length
Example 3: Production of a packaging material based on
unbleached kraft paper with a grammage of 130 g/m2
Process description:
An unbleached cellulose consisting of 95 % primary cellulose
from softwood with a Kappa number of 41 and 5 % primary
cellulose from hardwood with a Kappa number of 40 was firstly
subjected to high-consistency beating with a beating
capacity of 190 to 210 kWh/t, wherein a degree of beating of
the cellulose after high-consistency beating was 19 SR and
then this cellulose was subjected to low- consistency beating
with a beating capacity of 70 to 80 kWh/t. The auxiliary
materials were added into the constant part of the paper
machine. The pH was adjusted to a pH of 6.8 to 7.0 with
aluminium sulphate, cationic starch with a degree of
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31
cationization DS of 0.03 was added absolutely dry in an
amount of 14 kg/t of paper and alkenyl succinic anhydrides
were used as the sizing agent in an amount of 0.8 kg/t kraft
paper absolutely dry. Glyoxalated PAM with 10 kg/t absolutely
dry kraft paper was used as the wet strength agent.
Furthermore, no fillers were added. The consistency of the
cellulose at the headbox was 0.23 %. The dewatering was
carried out on a Foudrinier wire section and with a press
section having three nips, wherein one of which can be a
shoe press, wherein the line pressure at the three nips was
60 kN/m, 90 kN/m and 500 kN/m (in the shoe press). The kraft
paper is pre-dried and then treated in a Clupak system with
a differential speed of -8.6 % and finally dried to an
ultimate final moisture content of 7.5 %.
The kraft paper can be used as such and the paper properties
described in the following table were measured with this
paper.
The kraft paper thus produced had the following properties:
Paper Standard Unit Direction Result
property
Grammage ISO 536:2019 g/m2 130
Tensile ISO 1924-3:2005 kN/m MD 16.2
strength
Tensile ISO 1924-3:2005 Nm/g MD 124.6
strength
index
Tensile ISO 1924-3:2005 kN/m CD 6.3
strength
Tensile ISO 1924-3:2005 Nm/g CD 48.5
strength
index
Elongation ISO 1924-3:2005 % MD 10.3
at break
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32
Elongation ISO 1924-3:2005 % CD 8.5
at break
Tensile ISO 1924-3:2005 J/m2 MD 871
energy
absorption
Tensile ISO 1924-3:2005 J/m2 CD 372
energy
absorption
Bendtsen ISO 8791-2:2013 ml/min Upper 1420
roughness side
Bendtsen ISO 8791-2:2013 ml/min Lower 1890
roughness side
Bursting ISO 2758:2014 kPa 812
strength
Wet ISO 3781:2011 Nm/g MD 16.1
strength
index
Tear index ISO 1974:2012 mN.g/m2 MD 12.1
Tear index ISO 1974:2012 mN.g/m2 CD 19.3
Strain ISO 1924-3:2005 - MD/CD 1.21
ratio
Tear ISO 1924-3:2005 Km MD 12.7
length
Example 4: Production of a packaging material based on
unbleached kraft paper with a grammage of 161 g/m2
Process description:
An unbleached cellulose consisting of 100 % primary cellulose
from softwood with a Kappa number of 46 was first subjected
to high-consistency beating with a beating capacity of 210
to 220 kWh/t, wherein a degree of beating of the cellulose
after high-consistency beating was 18 SR and this cellulose
was then subjected to low-consistency beating with a beating
capacity of 70 to 85 kWh/t. The auxiliary materials were
added into the constant part of the paper machine. The pH
Date Recue/Date Received 2024-04-08
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33
was adjusted to a pH of 6.8 to 7.0 with aluminium sulphate,
cationic starch with a degree of cationization DS of 0.05
was added in an amount of 12 kg/t of kraft paper absolutely
dry and alkenyl succinic anhydrides were used as sizing agent
in an amount of 0.8 kg/t of kraft paper absolutely dry.
Furthermore, talc was added as a filler in an amount of 2
kg/t of kraft paper absolutely dry. The consistency of the
cellulose at the headbox was 0.25 %. The dewatering was
carried out on a Foudrinier wire section, such as a press
section with three nips, wherein the line pressure at the
three nips was 60 kN/m, 80 kN/m and 80 kN/m, respectively.
The kraft paper was pre-dried, then fed to the Clupak system
and subjected to a differential speed of -10.9 %, then
finally dried to a final residual moisture content of 8 %.
The kraft paper can be used as such and the paper properties
described in the following table were measured with this
kraft paper.
The paper thus produced had the following properties:
Table 3:
Paper Standard Unit Direction Result
property
Grammage ISO 536:2019 g/m2 161
Tensile ISO 1924-3:2005 kN/m MD 19.1
strength
Tensile ISO 1924-3:2005 Nm/g MD 118.6
strength
index
Tensile ISO 1924-3:2005 kN/m CD 7.9
strength
Tensile ISO 1924-3:2005 Nm/g CD 49.1
strength
index
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34
Elongation ISO 1924-3:2005 % MD 12.7
at break
Elongation ISO 1924-3:2005 % CD 9.0
at break
Tensile ISO 1924-3:2005 J/m2 MD 1007
energy
absorption
Tensile ISO 1924-3:2005 J/m2 CD 461
energy
absorption
Bendtsen ISO 8791-2:2013 ml/min Upper 1970
roughness side
Bendtsen ISO 8791-2:2013 ml/min Lower 2480
roughness side
Bursting ISO 2758:2014 kPa 903
strength
Wet ISO 3781:2011 Nm/g MD 15.8
strength
index
Tear index ISO 1974:2012 mN.g/m2 MD 12.7
Tear index ISO 1974:2012 mN.g/m2 CD 20.6
Strain ISO 1924-3:2005 - MD/CD 1.41
ratio
Tear ISO 1924-3:2005 Km MD 12.1
length
It is needless to say that the kraft papers according to the
invention can additionally be calendered, for example in a
soft nip or long nip calender, or in particular can also be
subjected to a coating treatment, such as a dispersion
coating treatment with a thermoplastic material, such as
HDPE, LDPE, PLA or PP. With such further treatments, however,
the essential properties of the packaging material, such as
elongation at break, Bendtsen roughness, tear length, tear
index, tensile strength index, are not changed, in particular
do not deteriorate. If there is a loop or sleeve further
Date Recue/Date Received 2024-04-08
CA 03234736 2024-04-08
manufactured from the packaging material, care must be taken
to ensure that the packaging material is arranged such that
the original machine direction is arranged such that an
increase in diameter or stretching of up to 20 % of the
sleeve or loop is possible in the event of a stretching
stressing of the sleeve. By means of a coating optionally
applied on one or both sides of the sleeve, the way in which
the free ends of the packaging material forming the loop or
sleeve are connected, can be changed. In particular, in such
a case, a thermal sealing of the free ends is carried out.
Without a coating, the free ends can be connected by gluing,
clipping, crimping or even sewing or the like. In the case
of a packaging material that is coated on one side, a
connection using hot glue, hot melts or the like can also be
provided. In the case of packaging materials coated on both
sides, a direct connection of two coating layers is in
particular provided, which can be achieved with an extremely
small expenditure of time.
Multi-layer packaging materials are preferably formed as
laminates consisting of at least one kraft paper layer,
preferably several kraft paper layers and at least two
coating layers consisting of a polyolefin, in particular
HDPE, LDPE or PP or PLA.
Example 5 shows a laminate consisting of an unbleached kraft
paper layer (KP) with a grammage of 120 g/m2 and an outer
coating layer made of HDPE with a grammage of 15 g/m2 on both
surfaces of the base paper. The kraft paper was produced as
described in Example 3. An extrusion coating process was
used as the coating process. The laminate formed therefore
has the following structure: 15 g/m2 HDPE/120 g/m2 KP/12 g/m2
HDPE.
The laminate thus produced had the properties described in
the following table.
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36
Table 4
Paper Standard Unit Direction Result
property
Grammage ISO 536:2019 g/m2 150
Tensile ISO 1924-3:2005 kN/m MD 12.5
strength
Tensile ISO 1924-3:2005 kN/m CD 5
strength
Elongation ISO 1924-3:2005 % MD 12.5
at break
Elongation ISO 1924-3:2005 % CD 9.4
at break
Tear index ISO 1974:2012 mN.g/m2 MD 1300
Tear index ISO 1974:2012 mN.g/m2 CD 2000
WVTR A5TM1249 g/m2/24h MD 3
(23 C/50 %
RH)*
*WVTR test climate 38 C/100 % RH
Example 6 shows a laminate consisting of 3 kraft paper layers
(KP), each having a grammage of 120 g/m2 and both an outer
coating layer made of LDPE with a grammage of 15 g/m2 and an
LDPE coating between two kraft paper layers with a grammage
of 12 g/m2. The kraft paper was produced as described in
Example 3. An extrusion coating process was used as the
coating process. The laminate formed therefore has the
following structure:
15 g/m2 LDPE/120 g/m2 KP/12 g/m2 LDPE/120 g/m2 KP/12 g/m2
LDPE/120 g/m2KP /15 g/m2 LDPE
The laminate thus produced had the properties described in
the following table.
Table 5
Paper Standard Unit Direction Result
property
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37
Grammage ISO 536:2019 g/m2 414
Thickness ISOP pm -430
534:2012-02
Tensile ISO 1924- kN/m MD 39.4
strength 3:2005
Tensile ISO 1924- kN/m CD 15
strength 3:2005
Elongation at ISO 1924- % MD 12.9
break 3:2005
Elongation at ISO 1924- % CD 9.4
break 3:2005
Burststrenght ISO 9895:2008 kPa - 2442
Tear index ISO 1974:2012 mN.g/m2 MD 4680
Tear index ISO 1974:2012 mN.g/m2 CD 7200
WVTR (23 C/50 A5TM1249 g/m2/24h MD 3
% RH)*
*WVTR test climate 38 C/100% RH
Furthermore, it is possible to replace one or all of the
polyolefin or polylactic acid layers arranged between two
layers of paper with a glue and thereby create a firm
cohesion of the individual layers forming the laminate.
In this case, however, it is essential that the two outer
coating layers are made of a polyolefin or PLA.
A band produced from such a laminate could, on the one hand,
be used on conventional strapping machines and, above all,
heavy and bulky objects can be held together or packaged
therewith without fear of the band tearing. A band produced
from such a laminate could therefore be used as a replacement
for a conventional strapping band manufactured entirely of
plastic.
Date Recue/Date Received 2024-04-08
