1. from forest to market - iggesund paperboard · 1. from forest to market ... pensive catalogues...
TRANSCRIPT
7IGGESUND PAPERBOARD | Reference Manual
1. From forest to market
Paperboard the natural choice 9
The philosophy of choice 15
The paperboard product 17
Choices of raw material 19
Differences paper and paperboard 22
Fibre to board 26
The paperboard machine 36
Extrusion coating and lamination 38
Board lamination 44
Design and carton construction 46
Consumer use and appeal 56
Distribution and storage 57
Retailing 60
Taint and odour neutrality 61
Migration into foodstuffs 65
Reference Manual | IGGESUND PAPERBOARD 8
Paperboard – the natural choice
9IGGESUND PAPERBOARD | Reference Manual
Paperboard – the natural choice
Paperboard – the natural choice
When Iggesund published the Paperboard Reference
Manual in 1992 it was an attempt to create a reference
manual for everyone who works professionally with paper-
board material. Over the years the book has been much
appreciated, and in addition to its purely professional use
within the graphics and packaging industries, the book
also features in courses given by a number of universities
and other third-level educational institutions. Our ambition
has been to maintain a high level of factuality and neutrality
of information so that the Paperboard Reference Manual
will remain a credible work of reference.
In this, the second, revised edition, we have continued
with this tradition, with one exception. In this introduction
you are now reading, we discuss some aspects of paper-
board which are not so easy to quantify or assess.
Paperboard – a natural materialAs a material, paperboard is special. It is the material with
the highest added value within the material system com-
prised of paper and paperboard, and is most often used
for packaging and high-quality printed materials.
This material system includes everything from virgin
fi bre-based paperboards, such as Invercote and Incada,
to paper products made of fi bres that have been repeat-
edly recycled. In the market for paper-based products,
pricing is typically based more on price per unit of weight
than price in relation to the end result in terms of its func-
tions, visual appearance and economy of production.
In a typical advertising or packaging project, great effort
is taken to fi nd the right designer and photographer, and
to handle all the produced material in the optimal way
throughout the production chain. As manufacturers of
high-quality paperboard, we are sometimes astonished
at how casually many producers of packaging and printed
materials choose their input material, after having taken
considerable care over the quality of the entire process
that precedes printing or converting. It is easy to fi nd ex-
pensive catalogues or cartons whose colour-printed areas
have cracked along the crease even before any consumer
or reader has handled them. There are also countless
brochures, whose cover, if it had been made of stiff pa-
perboard instead of thick fi ne paper, would have had far
greater impact on the recipient’s experience of quality.
Virgin fi bre-based paperboard is the paper-based mate-
rial with the greatest added value, and for many applica-
tions there are simpler and more cost-effective solutions.
However, for anyone who wants the possibility of creating
more complex shapes to attract attention, for anyone
who wants taint- and odour neutrality, or for anyone who
is looking for the ultimate in printing properties, our virgin
fi bre-based paperboards, Invercote and Incada, are inter-
esting options. If the potential purchaser then explores
how these paperboards behave in graphic post-produc-
tion or in packaging lines, the conclusion is even more
clear: the key issue is not price per kilo, it is performance.
When purchasing the input material, it is important to as-
sess the cost per useable end product instead of merely
considering the price per kilo.
Experiencing paperboard European paperboard normally has a multi-layer structure
that creates a stiffness which exceeds that of all single-
layer, cellulose fi bre-based materials. This stiffness is part
of the quality that we offer our customers and that can be
exploited to reinforce the quality experience or reduce the
grammage of the input material.
Another parameter which is often used when choosing a
material is the degree of measured whiteness. Whiteness
as measured on the paper and board market is a simple
number which is a combination of three different measured
values. The equation by which these values are assessed
is such that paperboards which look completely different
can have the same whiteness value. What is most absurd
is that the blue shade, which causes major problems when
printing accurate skin tones, is rewarded in this combined
calculation of whiteness. At Iggesund, we have deliber-
ately chosen not to attain the highest whiteness measure-
ment. We do not want our paperboard to become bluer in
a purely optical sense, which would make it harder for our
customers to accurately reproduce skin tones. We would
have no problem becoming even whiter if we wanted to,
but we have chosen a whiteness level for good colour
reproduction.
Paperboard within the goods fl owPaperboard is one of the most widely used packaging
materials in the world thanks to the economic benefi ts it
offers throughout the chain from producers to consumers.
Carton blanks can be transported fl at and cost effectively
until they are erected and fi lled with the contents they are
designed to protect and preserve throughout the dis-
tribution chain to the consumer. The printing properties
of paperboard packaging make it easy to convey both
commercial messages that encourage purchase and
legally required information about the contents. Paper-
board packaging can also be recycled as a material or its
stored biogenic energy can be recovered via combustion
or anaerobic digestion in accordance with the appropriate
environmental targets. Paperboard is also compostable,
which means that as a material it functions in all the waste
streams listed in the European directive on packaging and
packaging waste (EC94/62).
Reference Manual | IGGESUND PAPERBOARD 10
Paperboard – the natural choice
For a better environmentAt Iggesund, paperboard production goes hand in hand
with sustainable forest management. For every tree which
is harvested and used in our production process, we plant
three or four new ones. The result is a sustainable closed-
loop cycle that stretches over a century or more. Those of
us who are now collecting the pine cones containing the
seeds for these new trees will not be alive when Iggesund
harvests the trees that will be the fruits of our labour.
Our operations at both Iggesund and Workington are
energy effi cient and their environmental performance fi g-
ures are well within the limits prescribed by their permits.
One of our long-term goals is to further minimise the im-
pact of our large-scale industry on the local environment.
At the most fundamental level, we live off what nature
gives us. A business that bases its operations on this fact
– and has done so for more than four centuries – must
have a sustainable and long-term approach.
We produce one of industrial society’s most environ-
mentally sustainable products. It is made from a renew-
able raw material and can be recycled both as energy and
material. It has minimal impact on our air and water, and
produces no waste material that is sent to landfi ll.
As a material, paperboard is a good component in any
sustainable environmental strategy.
We work within the most sustainable material system in
existence. We have been responsible stewards of our raw
material for centuries. Our manufacturing is integrated
– we transform our own timber into pulp that is optimised
for board production, which gives advantages of produc-
tion economy, quality and quality consistency. Rising
energy prices and more stringent environmental demands
are increasing paperboard’s relative competitiveness
versus other material systems.
On the horizon are a greater use of biomass, smarter
energy solutions that further improve our economy of
production, and new spinoff products that make the forest
raw material even more interesting. Paper and paperboard
are a material system whose raw material is renewable,
whose products are recyclable in many ways, and where
there already exist sophisticated systems for on-site recy-
cling and energy recovery.
Our history goes back many centuries but our material
still has a long future ahead of it!
Paperboard is a natural material with many applica-
tions. As a print medium, paperboard can withstand all the
strains and stresses involved in the use of advanced fi nish-
ing techniques. Paperboard is also highly durable, ensur-
ing that printed materials will last for a long time. Typical
graphical applications are book covers, cards, and CD
and DVD covers. Paperboard packaging is a competitive
method of conveying products from the manufacturer to
the consumer while also being easy to recycle. In terms of
graphic design, paperboard’s excellent printing properties
give brand owners great freedom to express their brand’s
individuality and thereby attract the consumer’s attention.
Compared to other materials, paperboard made of virgin
fi bres has high performance and relatively low weight. It
is safe for consumers to use because it contains known
substances and is made in the same way every time.
In most cases paperboard packaging remains folded or
fl at until the products are packed. Thanks to paperboard’s
small volume and low weight, large amounts of energy are
saved in the transport chain. Paperboard cartons can be
dimensioned to maximise the use of loading pallets, which
leads to further signifi cant energy savings in the distribu-
tion chain. When paperboard cartons have served their
purpose they can be folded and compressed before being
transported to a suitable recycling station. At every step
of the way, paperboard packaging saves more energy and
has lower environmental impact than most other packag-
ing solutions.
Paperboard is made from timber, which is a renewable
resource. Sunlight and water make the trees grow, while
they also bind carbon dioxide and give off the oxygen es-
sential to life. The forest’s closed ecological loop provides
us the raw material for paperboard, while used cartons
and printed matter have their own role to play in the recy-
cling system of a sustainable society.
An overall viewIn considering the merits of packaging and graphical ma-
terials, or the impact of their manufacture on the environ-
ment, it is important to take a holistic view. The issues to
be considered will normally include four key subjects – the
use of raw materials and energy; the production process;
product and function; and final recycling or disposal.
It is meaningless and misleading to address narrow
issues within any of these broad headings, and at the
same time ignore considerations arising from the wider,
overall view.
Meeting real needsAs one of the longest surviving materials for communica-
tion and packaging, paperboard has been meeting the
requirements of many societies for a long time.
Nowadays, discussions about the general topic of
packaging often focus on the issue of whether or not
packaging actually serves a useful function. The question
is often raised in very simplistic terms – is packaging really
necessary?
In fact, effective packaging has helped to revolutionise
the mass distribution of products in advanced industrial so-
cieties. In many cases the existence of effective packaging
actually saves spillage and waste by protecting and
preserving products en route from the manufacturer to the
retailer and on to the consumer.
Packaging meets real needs. Consumers need to have
a wide choice of conveniently available, well presented and
well packaged products from which to choose. Manufac-
turers and retailers need to effectively impart information
and attract purchasers.
11IGGESUND PAPERBOARD | Reference Manual
Paperboard – the natural choice
Reference Manual | IGGESUND PAPERBOARD 12
Paperboard – the natural choice
Raw materials As we explain in the description of our manufacturing
process, the wood fi bre used to produce our products is a
renewable resource. The managed forests which supply
the timber are constantly replenished. A vigorously grow-
ing forest is effi cient in absorbing carbon dioxide, fi xing
carbon, and producing oxygen.
Energy The chemical pulping process is highly energy effi cient and
the chemical recovery in the pulping process is also very
high. The production of pulp and the manufacture of pa-
perboard are carried out on the same site in a continuous
integrated process, giving benefi ts in quality, effi ciency,
and economy.
Taint and odourThe taint and odour characteristics of the packaging itself
are of prime importance where long term close or direct
contact must not impair those characteristics of the prod-
uct it is designed to protect.
The selected packaging must therefore be produced
from raw materials which are made from pure materi-
als, selected and processed under carefully controlled
conditions. Following manufacture, the application of inks
and varnishes also requires careful control to ensure that
residues do not remain and have an impact on the taste
and odour of the product.
Knowledge materialThe Iggesund Paperboard Reference ManualThe Iggesund Paperboard Reference Manual is part of the
Iggesund Anchor MaterialIggesund Anchor Material, a body of information material
that also consists of the following publications:
• Iggesund Product Catalogue• Paperboard – the Iggesund Way• Graphics Handbook – Paperboard the Iggesund Way• www.iggesund.com
The Reference ManualThe Reference Manual is the most extensive and techni-
cal of these texts. It attempts to convey all the collected
knowledge we can present with regard to the design and
production of paperboard applications. The Reference The Reference
ManualManual is primarily a consultative document intended to
assist readers who wish to improve their possibilities of
getting the most out of their paperboard material. It places
great emphasis on paperboard properties, since these de-
fi ne and limit the performance it is possible to achieve with
this natural material – whether that performance involves
effectively conveying a message or effi ciently transporting
a product through the entire distribution chain.
13IGGESUND PAPERBOARD | Reference Manual
Paperboard – the natural choice
The objective of the Iggesund Anchor MaterialIggesund Anchor Material is to assist
people involved in specifying, selecting, printing, convert-
ing or using paperboard. Both the experienced paper-
board user as well as the less frequent user should fi nd the
information they require within this information package.
The Iggesund Paperboard Reference Manual contains the following information• basic facts about paperboard
• paperboard appearance and performance properties,
and their interdependencies
• paperboard conversion methods and the possibilities/
requirements they place on paperboard properties.
The Product Catalogue provides• facts and fi gures about paperboard properties
• general technical information about paperboard
handling, quality assurance, product safety regulations,
sustainability and paperboard terminology.
Paperboard – the Iggesund Way
Contains basic facts about Invercote and Incada and the
paperboard manufacturing process. It also describes the
customer benefi ts available from Iggesund Paperboard’s
mills and paperboard manufacturing processes, customer
support and service.
The Graphics Handbook – Paperboard the Iggesund Way
Focuses primarily on graphical production and fi nishing,
and only touches on the topics of packaging design and
materials knowledge. Selected parts and digital versions
of the publications are available on www.iggesund.comwww.iggesund.com.
If you require further help, please contact your local
Iggesund Paperboard representative.
The information in the Iggesund Anchor Material Iggesund Anchor Material is
correct at publication. It is subject to review as part of
Iggesund Paperboard’s commitment to continuing prod-
uct development.
Reference Manual | IGGESUND PAPERBOARD 14
Paperboard – the natural choice
15IGGESUND PAPERBOARD | Reference Manual
The philosophy of choice
The philosophy of choice
The paperboard choice is determined by the end use
application. We recommend, as the fi rst priority, that the
end use needs are analysed in terms of appearance and
performance.
Aspects of appearance and performance needs for the
two major applications, graphical and packaging prod-
ucts, are described below.
GraphicsGraphical applications can be postcards, brochures, or
book covers. The purpose is to convey a message and
paperboard is the medium. The medium is always a part
of the message, so the appearance of the medium must
correspond to the message it carries.
Printed texts and graphic images are used to convey
the message. A metallic, glossy or matt appearance is an
effective way of giving the graphical product, such as a
magazine cover, an exclusive image. Relief and creative
shapes can be used to generate interest.
A graphical product that may be handled many times,
for example a book cover, requires considerable durability.
Transportation costs can be a major part of the total
production cost in graphical applications, for example
postage costs when mailing brochures to customers.
PackagingThe primary task of a package is to protect the contents
from the surrounding environment, which might include
impacts during handling, pressure in stacking, and
extremes of temperature and moisture. In addition to its
strength the paperboard package is also very suitable for
promotional purposes.
During transportation the protection requirement is
decisive, but on a shelf in the grocery store the package
is more promotional than protective. The major purposes
of the package, which can change in emphasis during the
products life cycle, are:
• Protect the product during transportation and storage.
• Promote the product with an attractive appearance.
• Inform the consumer about how to use the product.
• Protect the product during consumer use.
The demands for protection might vary as well as the
needs for promotion. Each end use application has its own
combination of protection and promotional requirements.
Promotional needsThe package promotes the product and creates an im-
age of the product for the customer. The product and the
package must create the same impression. An exclusive
perfume needs a package with a corresponding appear-
ance, for example a metallic fi nish. Pharmaceutical prod-
ucts often have packages which are very white to empha-
sise the image of a clean and effi cacious product.
Packages with creative shapes attract attention. An exist-
ing product might be given a new package to increase
sales. Paperboard as a material provides endless options
for constructing creative shapes.
Physical protection needsThe concept of physical protection involves the end user’s
requirement that the packages withstand external forces
in order to protect and hold its contents under various
condi tions. This protection is needed during transport
and storage.
To meet extreme requirements, e.g. deep-freeze appli-
cations, additional functional protection is required.
Protection can also be vital during use. A cigarette pack,
for example, must still look attractive after being carried in
a handbag or pocket.
Reference Manual | IGGESUND PAPERBOARD 16
The philosophy of choice
Possibilities and contradictionsPromotional and physical protection needs are met by
the properties of the paperboard, e.g. smoothness, stiff-
ness and strength. Whilst it is always possible to fi nd an
optimum paperboard solution for packaging and graphi-
cal needs it is important to realise that properties such as
smoothness, stiffness and strength, while they all vary with
density, do so in different ways due to the laws of nature.
Limitations due to the laws of natureStiffness and strength are two properties which are depend-
ent on the density of the paperboard, but in opposite ways.
This contradiction is due to the laws of nature and is related
to the characteristics of the cellulose fi bres. The general re-
lationship between stiffness, strength, surface appearance
and density is shown in the illustrations.
Relative economy of productionIf a product is expensive, the package will be more intri-
cate and exclusive to match the product. However, the
cost of the package as a percentage of the value of the
product is still very low.
Runnability is a property which is of great importance
when comparing the economy of production of various
materials. If the chosen paperboard causes a lot of pro-
duction stops in converting and fi lling, due to low runnabil-
ity, it will result in a costly package. A wise choice in the
beginning saves a lot of money in the end. When consid-
ering production economy in choosing paperboard it is
important to have an overall view.
ConsistencyThe importance of consistency cannot be overemphasised.
The demand for consistency applies to all paperboard
properties, including both appearance and performance
parameters.
Two aspects of consistency are relevant:
• consistency within the order
• consistency between orders.
The cost benefi t of conversion and use without prob-
lems and wastage is signifi cant. Short runs with frequent
make-ready stops for new jobs put increased demands on
reliability. It is a great advantage if settings from a previous
run can be used again and again, thereby avoiding costly
adjustments.
When choosing a paperboard it is therefore important
to choose a paperboard supplier that has a documented
reliability. The consistency criterion is probably the most
important paperboard requirement.
ST
IFF
NE
SS
ST
RE
NG
TH
DENSITY DENSITY
SU
RFA
CE
AP
PE
AR
AN
CE
DENSITY
17IGGESUND PAPERBOARD | Reference Manual
The paperboard product
The paperboard product
Since the mid-19th century the primary source of cellu-
lose fi bre has been wood. The fi bre is separated by either
chemical or mechanical means from naturally occurring
species. In the case of Iggesund these species are mainly
spruce, pine and birch from managed forests in Scandina-
via and elsewhere in Europe. Such forests are maintained
and expanded by the industries that rely on good access
to timber. As a result of these efforts the stock of growing
trees is increasing every year. In many areas growth now
exceeds the amount of timber that is harvested.
This careful forest management ensures that even in the
future the forests will form part of the sustainable cycle of
nature and be a permanent source of raw materials.
The fi bres in a tree trunk run parallel to its length. The
fi bre length varies according to the tree species. The rela-
tionship is indicated by the table below.
Spruce fi bre – long and fl at Birch fi bre – short and cylindrical
Pine fi bre – long and fl at Mixed fi bres of spruce, pine and birch
Species
Spruce
Pine
Birch
Fibre length mm
3.1 – 3.5
2.0 – 3.0
0.9 – 1.2
Fibre width μm
19 – 50
22 – 50
20 – 35
Shape
Ribbon fl at
Ribbon fl at
Cylindrical with pointed
ends
Reference Manual | IGGESUND PAPERBOARD 18
The paperboard product
Cellulose and the laws of natureCarbon dioxide and water are converted into simple
glucose-based sugars by the action of sunlight on the
green chlorophyll-containing cells of the plant kingdom.
This process is known as photosynthesis and is accompa-
nied by the emission of oxygen. The natural sugars can be
polymerised in plants to produce cellulose.
Cellulose has a high molecular weight and a straight-
chain molecular structure. Plants use cellulose to grow
by constructing cells – what we call fi bres – and other struc-
tures which support the life of the plant. Each species has
its own characteristic fi brous structure. Many tree species
have been cultivated and developed over time into a renew-
able source of raw materials for the production of a wide
range of paper and paperboard products. Careful forest
management and the manufacture of paper products are
therefore closely linked.
Cellulose makes up around 44 % of the wood fi bre.
Pure cellulose fi bres are soft, fl exible and white. The other
constituents are hemicelluloses, lignin and extractives.
Hemicelluloses are a group of substances related to cellu-
lose but have lower molecular weight and a more compli-
cated chain structure. Lignin is a more complex polymer
and very different from cellulose. It is hard and brittle. Both
hemicelluloses and lignin occur in the fi bre but the main
concentration of lignin is between the fi bres, giving adhe-
sion and rigidity to the structure of wood.
The process of fi bre separation, or pulping, takes ad-
vantage of the differences between lignin and cellulose.
More laws of natureThere are natural properties which all wood fi bres have to
a greater or lesser degree as well as specific properties
associated with the fi bres of particular tree species. Fibre
characteristics are also infl uenced by the method of pulp-
ing which is used.
The general properties • The ability of fi bres to grip each other and bond into a
strong, homogeneous structure.
• Flexibility, shape and dimensional properties which en-
able fi bres to form a uniform interlaced network.
• The capacity of the fibres to be favourably modified,
mechanically or by using additives, during the production
process.
Different levels of magnifi cation of the wood fi bre,
revealing the difference between the seasonal growth
and a close-up of the fi bre showing its hollow interior
and the thin layer of lignin holding the fi bres together
CARBON DIOXIDE (CO2)
SUNLIGHT
OXYGEN (O2)
WATER (H2O)
CHLOROPHYLL
SUCROSE, ETC
19IGGESUND PAPERBOARD | Reference Manual
Choices of raw material
Choices of raw material
Types of fi breBasically the choice is between long fi bres (spruce/pine)
and short fi bres (e.g. birch). The board maker carefully se-
lects and blends different fi bres to achieve the appearance
and functional properties desired for specifi c products.
Types of pulpThere are three different pulping processes, which all pro-
duce different kinds of pulp: mechanical, chemical, and
recycled fi bre.
MechanicalThis process gives a very high yield of fibre from the tim-
ber. The presence of lignin in the pulp makes the fibres
hard and rigid. This produces a paperboard with high
stiffness, limited strength, low density and lower resil -
i ence. Mechanically separated virgin fibre pulp contain-
ing lignin reacts more strongly to changes in external
environment, humidity and temperature, a reaction that
can have a negative effect on flatness and dimensional
stability.
As a result, paperboard made solely from mechanical
pulp is relatively weak. The paperboard retains the yel-
lowish colour of the wood used and is pure because it
is made solely of natural and known raw materials.
ChemicalThis process preserves the length of the virgin fi bre. The
pure cellulose extracted has a high degree of consolida-
tion. Both of these features produce a very strong paper-
board sheet.
The fibre is flexible and soft, giving good creasing,
embossing, and die-cutting properties and low dust
generation.
Bleached cellulose pulp has high whiteness, brightness
and light stability. Paperboard made of virgin fi bre pulp has
the highest possible purity and provides packaged prod-
ucts with the best odour and taste neutrality.
RecycledThis separation and recycling process utilises a wide vari-
ety of waste paper and board. Each time a fi bre is recycled
it is contaminated and shortened and its capacity for con -
solidation is reduced. This means that virgin fibre must
be added to maintain the quality of recycled pulp. Recy-
cled pulp is carefully cleaned and screened during stock
preparation. Mixed waste paper is not usually de-inked
for paperboard manufacture and hence the pulp may
retain traces of inks, adhesives and other residues which
together give this kind of paperboard a grey colouration.
The resulting product has less predictable composition
and poorer functional properties than virgin fi bre-based
boards.
Mechanical pulp Chemical pulp
Reference Manual | IGGESUND PAPERBOARD 20
Choices of raw material
In addition to the types of fi bres and pulp, the construction
and coating of the paperboard sheet also affect the paper-
board’s fi nal properties. Selecting and combining types of
fi bres, the pulp preparation process, sheet construction
and coating give the paperboard the fi nal properties it
needs to meet a wide variety of market demands.
Solid bleached board (SBB)SBB is made exclusively from bleached chemical pulp. It
usually has a coated top surface and some grades are also
coated on the reverse side. The term SBS (Solid Bleached
Sulphate), derived from the method of pulp production, is
sometimes used to describe this product.
This is a medium density paperboard with excellent sur-
face printing properties to meet graphical and packaging
needs. It gives a wide scope for structural design and can
be cut, creased and embossed with ease. It is a pure and
hygienic primary fi bre paperboard and is suitable for the
packaging of aroma and fl avour sensitive products.
Folding box board (FBB)FBB comprises middle layers of mechanical pulp sand-
wiched between outer layers of chemical pulp. The top
layer of chemical pulp is bleached and pigment coated.
The back of the paperboard is cream (manila) in colour.
This is because the back layer of bleached or unbleached
chemical pulp is translucent, allowing the colour of the
middle layers to infl uence the appearance. The back layer
may, however, be thicker or have pigment coating – this
product is known as White Back Folding Box Board. The
combination of inner layers of mechanical pulp with outer
layers of chemical pulp creates a strong and stiff sheet,
taking advantage of the well-known I-beam principle in
physics. The mechanical pulp can be of CTMP (Chemi-
thermomechanical pulp), RMP (Refi ner mechanical pulp)
or TMP (Thermomechanical pulp) origin. This is a low den-
sity material with high stiffness. Fully coated grades give
excellent printing and visual impact. This is a primary fi bre
paperboard with consistent purity for product safety.
Solid unbleached board (SUB)SUB is made exclusively from unbleached chemical pulp.
The base board is brown. To achieve a white surface it
might be coated, sometimes in combination with a layer
of bleached, white fi bres under the coating.
The paperboard is used where there is a high strength
requirement, e.g. carrier sleeves, liquid packaging, etc.
Bytas ut till 3-skickt , Elisabeth pratar
med elena
FBB cross section
Coating
Bleachedchemical pulp
Unbleachedor bleachedchemical pulp
Mechanicalpulp
SUB cross section
Unbleachedchemical pulp
Coating
SBB cross section
Coating
Bleachedchemical pulp
21IGGESUND PAPERBOARD | Reference Manual
Choices of raw material
White lined chipboard (WLC)WLC comprises middle plies of recycled pulp. The top lay-
er or liner of bleached chemical pulp is frequently pigment
coated. The second layer or underliner may also comprise
bleached chemical pulp or mechanical pulp.
The reverse side layer can be made from specially
selected recycled pulp or may be white through the use
of bleached chemical pulp. There are additional grades of
unlined chipboards with coloured (dyed) liner plies.
This is a medium density product which is widely used
in general packaging. It is diffi cult to generalise about WLC
because of the wide range of qualities available.
Abbreviations/keys According to DIN 19303
GZ Coated SBB
AZ Cast Coated SBB
GC1 Coated FBB, white back
GC2 Coated FBB, cream back
GN Coated SUB, white or brown back
GT Coated WLC, cream or white back
GD1 Coated WLC, grey back (spec.volume >1.45 cm³/g)
GD2 Coated WLC, grey back (spec.volume 1.3 to 1.45 cm³/g)
GD3 Coated WLC, grey back (spec.volume <1.3 cm³/g)
UZ Uncoated SBB
UC1 Uncoated FBB, white back
UC2 Uncoated FBB, cream back
UT Uncoated WLC, cream or white back
UD Uncoated WLC, grey back
SBB Solid Bleached Board
FBB Folding Box Board
SUB Solid Unbleached Board
WLC White Lined Chipboard
G Gestrichen, coated
U Ungestrichen, uncoated
A Gussgestrichen, cast coated
Z Chemisch gebleichte Frischfasern, bleached virgin
chemical pulp
C Holzstoff, virgin mechnical pulp
N Chemisch ungebleichte Frischfasern, unbleached
virgin chemical pulp
WLC cross section
Coating
Bleachedchemical pulp
Bleachedreclaimed pulp
Selected wasteor unbleachedchemical pulp
Selected waste
Reference Manual | IGGESUND PAPERBOARD 22
Differences paper and paperboard
Cross section of a multi-ply paperboard
Differences paper and paperboard
Defi nition of the term paperboard varies. According to the
ISO standardisation body, a paper product with a gram-
mage exceeding 200 g/m² is called paperboard; however
the defi nition by the Confederation of European Paper In-
dustries, CEPI, reads “paper is usually called board when
it is heavier than 220 g/m²”. Paper board can be made in
a single ply or, more commonly, in several plies (multi-ply).
For quality reasons paperboard usually requires a com-
bination of several layers of fi bre in the wet state. When
studying the traditional paperboard market one can see
that multi-ply paperboard is already made at 160 g/m².
Two clear features distinguish paperboard compared
to paper:
• Paperboard contains a greater proportion of long fi bre
than paper.
• Paperboard does not normally contain fi llers.
At Iggesund Paperboard we claim that paperboard is a
heavier paper product of multi-ply construction.
The advantages of the multi-ply construction lie in the
ability to optimise fi bre characteristics in the different plies
to reach certain functionalities. This is done by varying the
content in each ply. The main features to vary are:
• proportion of long and short fi bres in the respective plies
• type of pulping method
• treatment of pulp to improve strength or bulk quality and
distribution of broke in the structure.
To be able to fully utilise the potential of optimising char-
acteristics in the paperboard it is crucial that the multi-ply
construction consist of at least three plies.
The existence of a middle ply enables the paperboard
maker to optimise surface characteristics in the outer
plies without losing stiffness and paperboard converting
advantages which are built in to the middle ply. The dual-
ply or single ply construction will always lead to one or
more compromises. Features which are easier to optimise
in a multi-ply construction than in a single ply construction
without compromising are:
• bulk
• strength
• stiffness both through high thickness and strong outer
plies
• surface smoothness in combination with desired
strength or stiffness achievements
• functional features in the respective plies such as in-
creased moisture resistance in surface or middle plies.
The ability to alter all these parameters has resulted in a
wide range of products in the industry which target certain
applications and end uses by tailoring features, as can be
seen in the following pages. The advantage of a multi-ply
construction in a paperboard mill is that the quality can be
adapted to different end uses by utilising the possibilities
of fi ne tuning the features mentioned above. This makes
it possible for one supplier to manufacture and supply
paperboard to meet the demands of several different end
uses, whereas a single-ply or dual-ply producer has more
limited possibilities.
Coating
Top ply
Centre plies
Bottom ply
23IGGESUND PAPERBOARD | Reference Manual
Differences paper and paperboard
Reference Manual | IGGESUND PAPERBOARD 24
Differences paper and paperboard
Characteristics of paperboard manufactureIn the beginning of the 20th century the production and
distribution of goods and food products increased and so
did demands for better protection of these items. A cheap
and easy solution was to use boxes made of thicker paper.
A change in the retail industry at this time from selling
products in loose bulk to selling products that were pre-
packed placed demands on packaging to be used not only
for protection but also for display. It became more import ant
to attract the consumer to recognise a product in the store
and pick up a specifi c product for purchase.
Papermakers had to specialise in order to meet box con-
verters’ demands for strong and stiff boxes which protect
the products from collapse during transport and which also
provide good printing and display functions.
Traditional thick paper was no longer good enough. As
a result, the fi rst paperboard machines were developed in
the United States.
Board machines are commonly built for optimum produc-
tion between 200 g/m² and 1000 g/m² while paper machines
have their optimum production grammage range from 70 to
200 g/m² depending on the intended application/end use.
From the layman’s point of view, a paperboard machine
and a paper machine can appear to be very similar. The dif-
ferences lie in the details. To examine these, we must look at
the different sections on the two machines’ confi gurations.
Fibre selection and stock preparationFor a board maker, the selection and refi ning of fi bres
depend both on the specifi c surface properties required
for printing and display and on the requirements for box
converting and the subsequent protection of the box’s
contents.
Using strong and long chemical fi bres from softwood
in the outer layers of a board and more bulky fi bres in the
middle layer is ideal for achieving the relevant stiffness and
strength properties.
Chalk is cheaper than fi bre and is often used by paper-
makers to reduce cost, improve opacity and improve sur-
face properties. However, chalk cannot be used by board
makers because doing so results in a deterioration in the
strength properties of the board. Both board and paper can
be made from recycled fi bres but the same issue of strength
arises, because recycled fi bres are weaker than virgin fi bres.
Stock preparation for board makers must be optimised
for stiffness, strength and surface properties. In contrast,
papermakers can focus solely on surface properties.
In producing board and paper for packaging foods, fatty
foods or liquids, manufacturers add chemicals to prevent
the fi bres absorbing grease or liquid from these contents.
Chemicals used for this type of application must comply
with regulations and directives from the EU and from the
FDA in the United States.
The wet end Paper and board are today produced both on a single wire
machine and on a multi-wire machine.
A board manufacturer selects the multi-wire construc-
tion of the wet end to meet the required surface, stiffness
and strength properties.
For a board maker with a multi-wire machine, the ideal
method is to combine different types of chemical fi bres in
the outer layers to achieve strength and good surface pro-
perties, and then to use one or more centre layers made
of more bulky fibres. Fibres produced by a mechanical
pulping process provide more bulk and are often used by
board makers in the centre layers.
Single-wire machines permit fewer possibilities to opti-
mise bulk, and board makers must compromise more
between stiffness, strength and surface properties.
Board manufacturers who use virgin fi bre are able to
specialise and optimise the sheet better, although board
manufacturers who use recycled fi bre will use similar tech-
niques in how they select and refi ne the fi bre.
The press sectionPhysically pressing out the water from the sheet in the
press section uses less energy than evaporating the water
in the drying section of the machine.
For a board maker, it is essential not to destroy the
strength and bulk properties of the sheet (which have
been built up in the wet end of the machine) in the press
section. At the same time, it is important to press out as
much water as possible so as not to lose economy of
production.
Over the years, board manufacturers have developed
press sections that are more forgiving and have a longer
press nip in order to achieve a high dryness of the sheet
before entering the drying section without compressing
the sheet too much and destroying its bulk, stiffness and
strength.
The drying sectionThere is no major difference between a board machine and
a paper machine. The drying section will typically consist
of a number of steam fi lled cylinders in contact with the pa-
per or board; the number used will depend on the amount
of water to be evaporated. The steam pressure in these
cylinders will be adjustable to control the rate of evapora-
tion and the fi nal moisture content.
CalenderingPre-calendering is used to make the surface of the uncoated
base paper or board as smooth and even as possible so as
to prepare the sheet for the subsequent coating operation.
Finish calendering or gloss calendering is used to improve
the coated surface and/or increase the gloss of the paper.
25IGGESUND PAPERBOARD | Reference Manual
Differences paper and paperboard
Cross section of paperboard
Both paper- and board makers also use calendering tech-
niques to achieve improved surface properties. However,
excessively hard calendering can easily destroy the bulk of
the sheet and thus the stiffness and strength properties of
the board.
Various types of calendering techniques have been
developed in the board industry such as soft nip, long nip
and metal belt calenders. Using these techniques it is pos-
sible to improve the surface without reducing the bulk.
CoatingThe coating operations for paper and board are basically
the same. The difference lies in the coating recipes. Board
manufacturers have different requirements than paper
manufacturers, depending on the intended application.
Converting board into boxes carries specifi c demands,
such as suitability for gluing functions. These must be taken
into account when optimising the coating recipe and testing
its suitability. Because one of the function of packaging is
to protect and not to contaminate its contents, liquid board
and board used to package food must be taint and odour
neutral. Accordingly, the chemicals used in the coating
must meet all the relevant safety requirements.
Winding, slitting and sheetingThere are no major differences between paper- and board
makers with regard to the winding, slitting and sheeting
operations. In order to provide the correct end user ap-
plication and be able to guarantee that the paperboard
has been produced under carefully controlled conditions,
board makers must have a system of full traceability
throughout the process.
100 μm
Reference Manual | IGGESUND PAPERBOARD 26
Fibre to board
Fibre to board
Today’s processes of separating fi bre and making paper-
board take place in facilities characterised by capital
intensity, high production volumes and the application of
the latest techniques of materials handling, continuous
production and process control.
In many cases, including the mills of Iggesund Paper-
board, the production of pulp and the manufacture of
paperboard are carried out on the same site in a continu-
ous integrated process, giving benefi ts in quality, effi ciency
and economy.
Managed forests provide the primary source of cellulose
fi bre from wood varieties such as spruce, pine and birch.
The fi bre is separated by mechanical or chemical pulp-
ing and the whiteness and purity may subsequently be
improved by bleaching.
Processing on the paperboard machine starts with the
formation of a layer of entangled fi bres on a moving wire
or plastic mesh from which water is removed by drainage.
Further layers of pulp are usually combined in the wet state.
More water is subsequently removed by pressing and dry -
ing. Paperboard is coated on-line or off the machine to
improve the printing surface. Large diameter, full machine-
width reels are produced by the machine. These reels are
subsequently cut into smaller reels or sheeted, labelled,
and wrapped prior to dispatch to the customer.
The forestry cycleThe virgin fi bre for paperboard is derived from naturally
occurring species such as spruce, pine and birch, which
provide fi bres with suitable characteristics. These species
are supplied by managed forestry operations in Sweden
and other parts of Europe.
To maintain sustainable development, including the re-
quirements for biological diversity, modern forest manage-
ment makes use of several combined methods. Detailed
planning is done at both a county and local level. Natural
regeneration, planting and sowing are used. Biologically
sensitive areas and old growth forests are protected ac-
cording to the local conditions.
Another important characteristic is that managed for-
estry is an integrated operation whereby wood for pulping
is harvested with wood for the timber industry. Thinnings,
the smaller diameter trees taken from the forest at vari-
ous stages to allow other trees room to mature, are used
to produce pulp. When mature trees are harvested, the
thicker part of the trunk is used as sawn timber, and the
tapered top goes to the pulp mill. This ensures maximum
use of the harvested timber.
Making the best use of raw materials is a key principle
within Iggesund Paperboard. The trees supplied to the
mills are transformed into paperboard – but also into the
energy that drives the production process, heats nearby
homes and dries sawn timber. Other end products are soil
compost and road-building material. Using the entire tree
is an important part of our ambition to carry out sustain-
able production.
From timber to fi bre – the pulping processThe timber logs which are delivered to the pulp mill are fi rst
debarked, since bark does not contain fi bre suitable for
pulp manufacture. Bark is removed by friction, as logs are
tumbled together in a rotating drum. The bark is then used
as a fuel within the mill or composted to create garden soil.
The next process depends on the type of separation or
defi bration process used.
Pulp manufactureBasically the choice is between long fibres (spruce and
pine) and short fibres (birch). The boardmaker optimises
sheet forming, appearance and performance properties
with an appropriate choice and blend of fi bres to meet the
needs of particular products.
PLANTING0-3 years
CLEANING3-15 years UK
3-30 years Sweden
HARVESTING30-50 years UK80-120 years Sweden
THINNING15-30 years UK30-80 years Sweden
pulpwood
pulpwood
sawn timber
27IGGESUND PAPERBOARD | Reference Manual
Fibre to board
Reference Manual | IGGESUND PAPERBOARD 28
Fibre to board
Mechanical pulp characteristicsThis process gives a very high yield from the timber. The
presence of lignin has a number of implications – the fi bre
is hard and rigid and this gives the sheet a limited degree
of consolidation, high bulk (low density), resilience, dimen-
sional stability, and stiffness.
The presence of lignin and the limited degree of consoli-
dation would make a sheet made solely from mechanical
pulp relatively weak. The pulp retains the colour of the
wood used and is of known natural composition and purity.
Refi ner mechanical pulp (RMP) is a two-stage process in
which the debarked logs are fi rst converted into small fl at
chips. These chips, with a moisture content of 25–30 %,
are forced between the rotating metal discs of a refi ning
machine. The heat and water vapour generated soften the
lignin so the fi bres can be separated. The pulp is screened
and cleaned and fi bre clumps are reprocessed.
Mechanical pulping results in a very high yield. About
95 % of the wood is converted to fi bre. Mechanical fi bre
separation requires high levels of electric power, and some
of the energy is usually recovered and used as heat in the
process.
Logsof raw
material
De-barking
Bark forfuel or
compost
Chippingand
washing
Refinerdefibration Bleaching
Washing+
Pulp toboard mill
WOODCHIPSILO
To screensand cleaners
REFINEDFIBRE
BLEACHING
REFINER
Preheater
EXCESS CHIPSRECIRCULATE
CHIP WASHERAND DEWATERER
Preheater
CONVEYORS
Preheater
MeteringScrewConveyors
29IGGESUND PAPERBOARD | Reference Manual
Fibre to board
Chemical pulp characteristicsThis process preserves fi bre length and the pure cellulose
develops a high degree of consolidation, both features that
give a very strong sheet.
The fi bre is fl exible and soft, giving good creasing, emboss-
ing, and cutting properties and with low dust generation.
Bleached cellulose pulp has high whiteness, brightness,
and light stability. This material has the highest purity and
provides products with the best odour and taint neutrality.
In the chemical process timber is fi rst converted into wood
chips. These are then cooked in chemical solutions to dis-
solve 80–90 % of the lignin, allowing the fi bres to separate
easily.
The sulphate process, which is used within Iggesund,
also permits effi cient chemical recovery and energy utilisa-
tion. The fi bre yield of unbleached chemical pulp relative to
wood is in the range of 50–65 %. The dissolved lignin and
resins from the wood are used in internal energy generation.
De-barking
Barkforfuel
Chippingand
washing
Impreg-nation
Continuouscooking
Washingand
straining
Oxygendelignifi-
cation
Diffusionbleaching
Washing+
Pulp toboard mill
Chemicalrecoveryenergy
generation
Logsof raw
material
Oxygen delignification Final washDoublestraining
NaOH
Pressurediffuser wash
Modified continuouscooking
O2
CIO2 CIO2 O2
H2O2NaOH CIO2 CIO2
PULP
DIFFUSER BLEACHING
DEFIBRATION
CHIPS
Reference Manual | IGGESUND PAPERBOARD 30
Fibre to board
Chips +liquor
High pressure steam
Washliquor
Chips
Impregnated chips(incl. liquor)
Pulp
Caustic soda/sodium sulphidesolution (white liquor)
Causticsoda/sodiumsulphidesolution(whiteliquor) Black liquor
in recycleloop
Reverseflowcooking
Forwardflowcooking
DIGESTERIMPREGNATOR
31IGGESUND PAPERBOARD | Reference Manual
Fibre to board
BleachingAll the varieties of pulp used in the manufacture of paper-
board can be bleached to infl uence colour and purity.
Chemical pulp is brown in colour, the colour density
depending on the cooking process and degree of lignin
removal. While unbleached pulp may be used for some
purposes, such as corrugated board boxes, it is neces-
sary to whiten the pulp for many graphical and packaging
applications.
The whitening of pulp is called bleaching, though the
process can take many forms depending on a number
of factors. These include the degree of colour change
required, choice of chemicals, method of treatment and
whether coloured compounds are removed (delignifi ca-
tion) or merely changed in colour.
All these factors have technical and economic implications,
not least of which is their environmental signifi cance.
Whitening methods fall into three categories:
• Bleaching by delignification using chlorine gas. This
approach has largely been replaced by processes with
better environmental safeguards. The use of oxygen is
being progressively introduced instead.
• Bleaching by oxidation using materials such as chlorine
dioxide, hydrogen peroxide or sodium hypochlorite.
• Bleaching by reduction using materials such as sodium
bisulphite.
If the pulp mill is integrated with paperboard manufac-
ture, the pulp is pumped to intermediate storage facilities.
If the pulp is sold to the open market it is dried in sheets
or by fl uffi ng and drying in hot air. Market pulp is baled for
shipment.
Reference Manual | IGGESUND PAPERBOARD 32
Fibre to board
Pulp (stock) preparationIf the pulp is bought in bales it is fi rst mixed by agitation in
water in a large vessel known as a hydra pulper. All pulp,
including the pulp which comes straight from the pulp mill
without drying, is then treated in various ways to prepare it
for use on the paperboard machine. The processed pulp
is referred to as “stock”. The consolidation properties of
fi bre can be improved by mechanical processing – refi ning
– which modifi es the surface structure of the fi bre. Swelling
in water expands the fi bres’ surface area, thereby increas-
ing their strength and ability to consolidate.
Additives such as internal sizing can be used to increase
the water repellency of fi bres, and retention aids to increase
dry strength. Fluorescent whitening agents (FWAs), also
known as optical brightening agents (OBAs), can be added
as required to increase the whiteness.
Discards and trimmings from the board making process
– called “broke” – are broken up and mixed into the stock
in varying amounts depending on which paperboard layer
the stock is intended for.
Finally, the “consistency” (fi bre/water ratio) is fi nely
adjusted prior to pumping the stock to the paperboard
machine.
FormingThe fibre suspension in water, at a consistency of around
99 % water, is “formed” in several even layers on a mov-
ing wire or plastic mesh. Each layer has a specific stock
composition suited to the layer’s function in the board
construction. The composition and properties of the stock
depend on the amount of long vs. short fi bres, the kind of
pulp, its degree of refi nement, retention properties, and
the proportion of broke that has been added. The water is
drained with vacuum assistance from the layer of entang-
led fi bres. The layers are brought together in the wet state.
PressingAt the end of the wire section and moving at a speed of
between 100–500 m/min the combined sheet or web is
suffi ciently consolidated to briefl y support its own weight
as it is transferred to the press section on an absorbent
textile blanket. Here the board is pressed together with
blankets between hard rollers and, with vacuum assist-
ance, more water is removed, reducing the moisture
content to around 60–65 %.
DryingThe moisture content is further reduced to 5–10 % (de-
pending on the product) by passing the sheet over steam-
heated steel cylinders. Some machines include in their
drying section a very large heated cylinder with a polished
steel surface. A wet paperboard web will adhere to the cyl-
inder surface and be progressively dried while at the same
time achieving a very smooth board surface. This cylinder
is known as an MG (machine glazing) or Yankee cylinder.
Surface sizingA starch solution can be applied to the paperboard surface
to improve strength and anchor surface fi bres fi rmly in the
sheet. Within Iggesund Paperboard the baseboard is sur-
face sized prior to being coated. When board is surface
sized a starch-based solution is applied to both sides of
the product: this improves surface strength and anchors
the fi bres to the sheet.
CalenderingPassing the sheet through a series of nips between steel
rollers or a soft nip calender can improve its smoothness
and adjust its thickness.
BASEBOARD
SURFACE SIZE
Surface sizing principle
33IGGESUND PAPERBOARD | Reference Manual
Fibre to board
The forming process
Headbox Fibre suspension
Formed sheet
Wire
The forming process
H2O H2O H2O H2O H2OH2O
H2O98%
H2O90%
H2O80%
Reference Manual | IGGESUND PAPERBOARD 34
Fibre to board
35IGGESUND PAPERBOARD | Reference Manual
Fibre to board
CoatingPaperboard products are coated to improve the appear-
ance of the product and also to improve performance
during printing.
The processAfter surface sizing the board is coated using blade
coaters, air knife or curtain coating. In a blade coater the
coating is applied to the baseboard using an applicator roll
or a jet applicator. The sheet continues up to a blade that
removes the excess coating. The excess coating is recir-
culated and reused. Once the excess coating has been
removed the paperboard is dried prior to the application
of the next layer of coating.
The coatingWhite pigmented coatings are applied to the print side of
the board and sometimes also to the reverse side. These
consist of selected mineral pigments and synthetic bind-
ers, dispersed in water. Selection depends on product
requirements and processing conditions. The application
and smoothing technique ensures a specifi ed coat weight
and smoothness. Smoothing may be by roll bar, air knife
or blade. There may be one, two or even three coating
layers applied to achieve the required appearance, colour,
smoothness and printing properties. The largest component
of a coating in terms of mass is the pigment. The pigment
used is usually a calcium carbonate (ground marble), clay
or a mixture of the two. The nature of the particles that
make up the pigment has profound effects on the proper-
ties of the paperboard. Calcium carbonate has a very high
whiteness but a relatively low opacity. Clay has a lower
whiteness and its use results in a smooth surface with a
higher gloss level and higher opacity. The second largest
constituent of a coating is the binder, which is often a latex
supplied as a water-borne emulsion. At this stage the latex
is a large number of very small particles. When the latex
is heated during the papermaking process the latex melts
and forms a fi lm that binds the pigment particles to one
another and also to the baseboard. Many other chemicals
are also routinely added to coatings to improve the per-
formance of the coating in the production process and
the performance of the fi nished paperboard.
Brushing and glazingSome paperboard machines incorporate equipment for
further surface enhancement by brushing and glazing.
ReelingThe fi nal process on the paperboard machine is to reel up
the paperboard in the full machine width to specifi ed reel
diameters.
TOPCOATPRECOAT
BASEBOARDBASEBOARDBASEBOARD
SURFACE SIZE
COATING
Reference Manual | IGGESUND PAPERBOARD 36
The paperboard machine
1
1
1
23
The paperboard machine
The basic features of a typical paperboard machines is
shown below.
1. Multi-ply formingIn contrast to paper, Iggesund paperboards are built up
in several layers, or plies. Fibres are supplied via inlets
(“headboxes”) at the wet end of the paperboard machine.
Concentration at the wet end is approximately 0.3 % fi bres
and 99.7 % water. A low fi bre concentration is essential in
order to obtain as uniform a distribution of fi bres as pos-
sible in each layer. The fi rst layer is formed on a plastic wire
and the water drains downwards. The subsequent layers
are stabilised on two upper wires and water drainage is
done both upwards and downwards depending on wire
and position. In the wet state, the layers of fi bre consoli-
date easily.
Precision in the distribution of fi bres and the consolida-
tion of the fi bre layers is a basic condition for qualities such
as fl atness, smoothness, strength and good creasing
properties.
2. PressingWhen the paperboard web reaches the press section,
water content has dropped to 80–85 %. The press section
is important for achieving the correct consolidation of the
fi bre layers. Sandwiched between two fabrics (felts), the
paperboard web is pressed between hard rolls. The water
is effectively removed so that moisture content in the pa-
perboard at the end of the press section is 60–65 %.
Here, qualities such as fl exibility, stiffness and runnability
are ensured.
3. DryingThe drying section allows optimal control over the drying
process. The paperboard web passes over steam-heated,
polished cylinders which gradually reduce the moisture.
A sophisticated system controls the temperature of the
cylinders to ensure that the web tension is under control
during the drying process.
The drying section establishes a uniform moisture pro-
fi le, fl atness and stability.
4. Surface sizingHere a starch solution is applied to one or both sides to
prepare the paperboard for coating. Surface sizing binds
the fi bres to the surface, making the paperboard more
uniform and dense.
5. CalenderingThe paperboard is passed between rotating steel rolls to
further increase surface smoothness. This process also
controls the paperboard’s thickness and density.
3
4
5
6
9
9
7
9
8
6. Surface coatingThe liquid, white-pigmented coating is applied and
smoothed out over the surface with a blade on either
one or both sides depending on the product. Each layer
is dried independently by infra-red and hot air dryers.
The surface coating section allows paperboard to be
coated twice on both sides to provide a high degree of
whiteness, smoothness and gloss. Coating also deter-
mines the surface’s ink and varnish receptivity.
7. Calendering and polishingThe fi nal gloss of the surface is achieved by gloss calen-
dering in a gloss calender or brush polisher. In the gloss
calender the paperboard web passes between a heated
hard steel roll and a soft polymer roll. In the brush polisher
the paperboard is polished by rotating brushes.
These processes give a uniform, smooth surface – which
is essential for good printing and varnishing.
8. Reel-upThe paperboard web is reeled onto a large steel core,
together weighing 30–40 tonnes depending on the pro-
duct. Each fi nished reel of paperboard is given a unique
identifi cation code which allows the product to be traced
all the way back to the raw materials.
9. Online measurement and controlThe web passes thousands of measuring points from
which data is transmitted to the central control system.
Optical on-line measurement is carried out on the mov-
ing web to check thickness, grammage, coating weight,
moisture content, whiteness and gloss. The resulting
regulation and control capabilities are a prerequisite for
uniform, high quality.
FORMATION SURFACE DEWATERING PRESSING DRYING SIZING DRYING GLAZING COATING GLAZING WINDING
STOCK
Moisture Moisture
Grammage
Thickness
Fibreorientation
OpticalProperties
Formation
Moisture
Grammage
Coat weight
BOARD MACHINE
ONLINE MEASUREMENTMoisture
Grammage
Thickness
Coat weight
Gloss
Optical properties
The paperboard machine
37IGGESUND PAPERBOARD | Reference Manual
Reference Manual | IGGESUND PAPERBOARD 38
Extrusion coating and lamination
Extrusion coating and lamination
Paperboard is coated with plastics to combine the me-
chanical properties of the paperboard with the barrier and
sealing properties of plastics. Paperboard combined with
a relatively small number of plastic materials will provide
the extra features needed to make the paperboard suit-
able for a number of specially demanding applications.
Extrusion coating is a process whereby molten plastic is
applied to paperboard and subsequently chilled to form an
extremely thin, smooth layer of uniform thickness.
The molten plastic can be used as an adhesive to lami-
nate a plastic fi lm or a metal foil.
Extrusion coating and lamination are used to achieve:
• moisture protection
• barrier to water vapour, oxygen, aroma, etc.
• grease resistance
• heat sealability
• sales appeal, for example shiny surfaces.
Sales appealThe use of extrusion coated and laminated paperboard
provides outstanding promotional benefi ts in terms of
visual appeal and consumer handling.
High gloss is created by extrusion coating and a specifi c
high gloss chill roll. A metallic effect is created by lamina-
tion with aluminium foil or metallised polyester fi lm. These
materials and processes also provide tactile sensations
of high quality and luxury which the consumer associates
with high value products packaged in these materials.
Examples of extruded and laminated products providing sales appeal • PE (polyethylene) extrusion coating of paperboard with a
gloss or matt fi nish. Printing and gluing (with cold glue) can
be done on a corona-treated surface.
• PP (polypropylene) and PET (polyethylene terephthalate)
are two heat resistant polymers that, applied on the board,
can be used in oven applications.
• Aluminium foil and metallised polyester film may be
laminated to the paperboard to provide a metallic effect.
Printing can be done on a pre-treated surface.
Functional coatingPaperboard as such is suitable for the packaging of dry
products in general. However, plain paperboard is only
suitable for direct contact with moist and greasy foods to
a limited extent, because moisture will affect the mechani-
cal properties of the paperboard, and absorbed grease
will cause stains. Such effects will obviously reduce the
protective function of the package and may detract from
the appearance as well.
Extrusion coating or lamination adds a thin layer of
plastic to the paperboard. Plastic coatings can provide
resistance to grease and moisture and, where appropri-
ate, be heat resistant. Plastic coatings can be heat sealed
and in some constructions these seals can be leak proof.
Depending on the application, the paperboard may be
extrusion coated on one or two sides.
Aluminium lamination provides packages with a barrier
to light, moisture, grease and gases. The aluminium foil
is often plastic coated to provide product safety and heat
sealing abilities.
Key characteristicsA number of process parameters infl uence the
grammage of the coating. The most important are:
• fl ow of the plastic melt
• temperature of the plastic melt.
Print on a foil laminated paperboard where the metal details of the guitar
is locked out of the photograph so that the metallic sheen underneath
is entirely exposed
39IGGESUND PAPERBOARD | Reference Manual
Extrusion coating and lamination
Applications
Liquids
Frozen foods
Ovenable packs
Description
Ice cream and soft drinks require a good water barrier.
Two side extrusion coatings are often required to main-
tain the rigidity of the cups. First class runnability in the
cup forming machine is an absolute necessity.
Frozen foods which are pre-frozen and packed as such
can usually be packed in one-side plastic coated paper-
board. Other products, which are packed wet and even
hot for chilling and freezing in the package, will generally
require a two-side plastic coated paperboard to ensure
that the package functions reliably all the way to the
consumer.
The packaging material must resist moisture and grease
at elevated temperatures without penetration into the
paperboard. The paperboard is given a heat-resistant
plastic coating, which must not affect the taste or odour
of the food.
Examples
Drinking cups
Ice cream
Frozen vegetables
Seafood
Baking using the pack-
ages as a baking mould
The extrusion coating
Reference Manual | IGGESUND PAPERBOARD 40
Extrusion coating and lamination
4
2
3
3
1
Extrusion coating and lamination machine
1. UnwindingThe paperboard is loaded into an unwinding position.
2. Surface treatmentThe paperboard surface is pre-treated with an electrical
corona discharge. The plastic fi lm can be treated with
ozone. These methods increase the adhesion of the
plastic to the paperboard.
3. Extrusion coatingPlastic granules such as polyethylene (PE), polypropylene
(PP) and polyethylene terephthalate (PET) are converted
by pressure and heat to the molten state in the barrel of the
extruder. The molten plastic passes through a narrow slit
in the automatically controlled die and onto the surface of
the paperboard. The control of temperature is critical. The
plastic surface is immediately pressed against the chilled
face of a steel roll, controls the fi nish of the plastic surface.
Reverse- side coatings have an NSO (Non-Set-Off) fi nish
and print-side coatings usually have a gloss fi nish.
Extrusion lamination machine
Moltenplastic
Moltenplastic
Coronatreatment
Coronatreatment
Coronatreatment
NSOChill-roll
Chill-roll
Reel up
Ozone
Ozone
Foil
Extrusion coating and lamination
4
3 5
2
6
4. Extrusion laminationAn unwind station is located immediately after the initial
plastic coating is applied. Foil or fi lm can be fed from this
position into the nip between the molten plastic fi lm and
the chill roll such that the plastic initially performs the
functions of an adhesive.
5. Corona treatmentPrint-side plastic coatings are subjected to corona
treatment to achieve good ink wetting. One-side plastic
coatings are also corona treated to improve the sealing
characteristics and permit gluing with emulsion adhesives.
6. Reel-upThe paperboard is wound onto large steel cores (drums)
in batches of between 1 and 3 tonnes depending on the
product. Each drum is given a unique in-house identifi ca-
tion code.
41IGGESUND PAPERBOARD | Reference Manual
Reference Manual | IGGESUND PAPERBOARD 42
Extrusion coating and lamination
Extrusion and lamination materialsThe materials used for extrusion coating and extrusion
lamination are paperboard, paper, plastic resins, plastic
fi lms and aluminium foil.
There are many types of coating resins and many of
them have special features for specific end user appli-
cations. Film and foil suppliers produce both standard
interchangeable products as well as their own speciality
niche products. These can be combined with paperboard
to create a great variety of products.
Plastic coating resins are selected for very low taint and
odour properties so that the packed products will not be
affected.
European waste legislation stipulates that packaging
material should be easily separable to enable recycling
when possible. The plastic layer on extrusion coated
material is by nature difficult to separate from the board,
which makes it difficult to comply with these regula-
tions. Mono materials, which are made from one basic
raw material, are sometimes seen as better alternatives
than composites such as extrusion-coated paperboard.
Composites exist because they are efficient and reliable
in providing the required functions. Promoting mono
materials usually means sacrifi cing functional performance
and adopting packaging materials with signifi cantly lower
effi ciency.
However, if the amount of the plastic barrier is below a cer-
tain level (currently 5 % of the total weight) the packaging
material is regarded as a mono material from a tax point
of view. There are well-proven processes in use today
that can separate plastics and foils from the fi bres. These
fi bres can then be used for the production of recycled fi bre
products. To facilitate recycling and maintain the quality of
the recycled materials, it is always an advantage to sort at
the source.
Key properties required for extrusion coating and lamination:
• surface properties such as structure, smoothness,
strength and profi le
• surface strength properties such as z- and tearing
strength and stiffness
• hydroscopic properties such as moisture, fl atness and
dimensional stability
• fl atness and dimensional stability
• cleanliness of edges and surface
• polymer adhesion
• odour/taint neutrality.
Key properties for glue lamination:
in addition to the above
• surface water absorption
• gluability.
Raw material
Polyethylene (PE)
Polypropylene (PP)
Polyethylene terephthalate
(PET)
Aluminium foil
Metallised PET fi lm
Additional properties
Good moisture barrier and sealability.
Good grease and moisture barrier. Resists high tempera-
tures and is sealable.
Very good grease resistance at elevated temperatures.
The amorphous coating is heat sealable and heat resistant.
Good fl avour barrier and smooth surface with high gloss.
Very high gloss and good printing characteristics. Good
fl avour barrier.
Applications
Frozen food, ice cream,
cups and confectionery.
Ready-made food for
reheating in the package.
Trays for reheating and for
baking.
Luxury products and
chocolates.
Gifts, wines and confec-
tionery.
43IGGESUND PAPERBOARD | Reference Manual
Extrusion coating and lamination
Additional coating propertiesThe strength characteristics of the paperboard are slightly
changed after extrusion coating and lamination. Plastic
coating with low density PE does not alter the stiffness but
PP or PET coatings will increase the stiffness considerably.
The toughness of the resin gives increased tear strength to
plastic-coated paperboard.
Plastic adhesionPlastic adhesion is a dimensionless property defi ning the
relationship between the adhesive and cohesive strength
of the paperboard surface. The bonding should ideally be
higher than the internal bond of the paperboard in order to
create fi bre tear. See Test Method in the Gluing chapter.
Adequate adhesion is important for most converting
operations, such as printing and heat sealing.
For production control an internal method is used.
The plastic coating or fi lm is pulled off at specifi ed angles
and the degree of fi bre tear is determined. The ranking is:
6 = 100 % fi bre tear, 1 = no fi bre tear.
If the strength of the paperboard/pigment coating is
stronger than the bond between the paperboard and the
plastic coating, no fi bre tear is achieved (e.g. fully pigment-
coated paperboard). Then a different scale of evaluation is
applied and the ranking is: 6 = excellent adhesion, 1 = weak
adhesion. In these cases the adhesion can also be measured
as peel strength at a 125 ° angle. The result is expressed as
N/cm width.
The plastic adhesion is mainly governed by:
• surface properties of the baseboard
• pre-treatment of the baseboard (corona and ozone)
• heat content of the plastic melt when applied to the
paperboard.
Corona treatment is necessary when:
• The plastic surface is to be printed (to enable the ink to
wet the surface).
• Emulsion glue is to be used (to enable the glue to wet the
surface).
Corona treatment also improves heat sealability. Two-side
corona treatment is not available because such a material
would give severe blocking problems between the sheets.
The corona-treated plastic surface is extremely sensitive. Any
rubbing, touching by hand, etc. will destroy the treatment.
During production the corona level is mainly affected by
mechanical damage. The moisture content of the paper-
board can also infl uence the level. For two-side PE-coated
paperboard we strongly advise never to stack more than
two pallets high.
Pinholes Pinholes are microscopic holes that might appear in the
plastic film during the coating process. In most cases,
a limited number of pinholes is acceptable. The main
reasons for the appearance of pinholes are irregularities
in the base paperboard (too high surface roughness, loose
fi bres, etc.), an uneven coating profi le or too low a plastic
grammage.
Measurable properties Pinholes
Coloured denaturised alcohol is applied on the test
surface. After 5 minutes the remaining liquid is wiped
off. Pinholes are indicated from the reverse side as
green spots. The number of pinholes is expressed as
number/m².
DROP OF INK
DROP OF INK
UNTREATED PLASTIC SURFACE
TREATED PLASTIC SURFACE
PAPERBOARD
PAPERBOARD
Reference Manual | IGGESUND PAPERBOARD 44
Board Lamination
Board Lamination
The basic paperboard products are produced in a limited
range of thicknesses because of the need for effi ciency
in paperboard manufacture. However, this thickness and
stiffness range is extended considerably when two or
more layers of paperboard are glue laminated together
into equal-sided products with the same smooth and
white printing surface on both sides. The many raw materi-
als available provide numerous combinations so that many
customer needs may be met.
Laminated paperboard offers good rigidity and smooth-
ness which, when combined with excellent visual appeal,
makes the package look more attractive to the consumer
in the store.
Laminated paperboard is smooth and fl at with good
cohesion and adhesion. The combination of stiff ness and
converting possibilities makes it suitable for the packaging
of expensive and luxury products.
Packaging that will come in direct contact with foodstuffs
must be designed for each specifi c end use.
Evaluation of paperboard laminationMost of the evaluation is done off-line. The aim is to deter-
mine and document that:
• the glue covers the whole web
• the glue keeps the webs together after drying
• the sheets are fl at and free from twist
• the pallets are fl at
• there is no damage (e.g. indentations) to the surfaces
• there is no visible dust or loose particles that can disturb
the converting operation.
Glue lamination machine
7. UnwindingThe glue lamination machine has four unwind stands.
8. DryingIR (infra-red) driers are used to control the shape of the
sheets.
9. GluingWater-based adhesives are used to glue the board webs.
10. Press NipAfter gluing, the webs are pressed together.
11. Sheeting and StackingThe glued board is sheeted and stacked on pallets in line.
7
9
11
8
10
45IGGESUND PAPERBOARD | Reference Manual
Board Lamination
Evaluation of extrusion coating and laminationThis process lends itself to control and continuous moni-
toring of the coat weight, coating profi le, thickness and
moisture profi les during production.
The following properties are measured off-line:
• adhesion
• surface smoothness (printing side, reverse side)
• surface tension (treated side)
• pinholes
• fl atness of the sheet
• heat sealability (where applicable)
• odour and taint neutrality
• surface defects
• blistering (where applicable).
Conversion operations in practiceSlightly different settings and techniques are necessary
with extrusion-coated and laminated products in printing,
die-cutting, creasing, gluing, and sealing. They are well
established and do not cause problems in practice.
Low odour printing inks and the programmed airing of
pallets are important to prevent the absorption of taint into
the plastic coating. Always use well-proven procedures
as prescribed by the printing ink supplier. Uniform coat
weight is important for successful conversion.
When paperboard is glue laminated together to give a
thicker and stiffer product, the following changes should
be considered:
Conversion operation
Printing
Die-cutting and creasing
Gluing
Packing
Considerations for extrusion coated and laminated products
Printing on a plastic-coated surface requires corona treatment of the plastic to make it
wettable. In addition, the basically non-absorbent nature of the surface requires the use
of printing inks that do not require absorbency. Such inks are available and they can
also be used on pigment coated surfaces.
Plastic-coated or laminated products with an extra tough layer like PET should prefer-
ably be die-cut from the plastic-coated side. In general, plastic surface layers improve
creasability because they have very good elongation before breaking and tend to
reduce the risk of surface cracking in the creases compared with plain paperboard.
Corona treatment improves the sealing characteristics and permits the gluing of one-
side PE-coated paperboard with emulsion adhesives.
The friction between the blanks should be considered, especially when they are made
with a glossy PE on the outside. The glossy corona-treated surfaces may tend to stick
together if not protected with printing ink or varnish plus spray powder.
Such sticking or blocking tendencies may also appear in some packing lines if the un-
printed glossy PE has to slide past polished steel guides. The remedy is to use varnish
and spray powder on the exposed areas of the paperboard.
Conversion operation
Printing
Die-cutting and creasing
Gluing
Considerations for glue laminated products
Stiffness may make fl atbed printing necessary. Two-side pigment coating means that
the reverse side is as smooth as the printing side. This can cause printing ink set-off.
Creasing must be carefully evaluated; the thicker products will need double creasing or
scoring. Die-cutting and creasing will require higher pressure; this may affect the wear
of the dies.
Gluing is done pigment coating to pigment coating. This procedure will be slightly differ-
ent compared to gluing the printing side to the normal reverse side. The higher stiffness
and different creases will give much higher spring-back force, so glue seams must be
well developed before pressure is released.
Reference Manual | IGGESUND PAPERBOARD 46
Design and carton construction
Design and carton construction
How is paperboard used and how can you get the most
out of it as a material? Whether you are using the paper-
board for a book or brochure cover or for a packaging it is
important to have a detailed knowledge of how it should
be handled and what demands will be made on it from the
various players involved in the chain between manufac-
turer and consumer or sender and recipient. Matching the
requirements for an appealing design with the require-
ments for cost-effective production, simple logistics and
good functioning in a retail environment is not an easy
task. In the following chapters we have chosen to focus
on functional requirements, mainly in the packaging chain,
before we go on to describe paperboard properties that
affect your choice of the most appropriate material.
The appearance of a package or graphical product is
decided during the design process. Paperboard is a ver-
satile material which provides an almost endless number
of possibilities. This means that when designing shapes
the only limitation is your own imagination. The design
comprises both the surface appearance and the shape
or structural design, and these two aspects of design are
discussed separately.
Brand owners and designers need to have a good un-
derstanding of the different stakeholders and their respec-
tive needs in order to make the most of the packaging and
its potential.
Examples of infl uencing factors• the brand itself
• the core product
• printer/converter
• packer/fi ller
• distributor
• retailer
• consumer
• legislation
• non-governmental organisations such as environmental
organisations.
Surface designThe surface design of a packaging or graphical product
based on paperboard comprises the effect of its print
presentation with the possible additional use of varnish-
ing, embossing, hot foil stamping, extrusion coating or
lamination.
The end user must defi ne and describe the surface
design needs of the packaging or graphical product. This
usually relates to the promotional and information needs
concerning the product and its use.
The designer has to prepare suggestions to meet the
surface design needs described by the end user. This may
have consequences concerning the choice of conversion
process, which in turn affects the choice of paperboard.
The converter has to reproduce the ordered quality in
such a way that it conforms with the agreed surface design
using the specifi ed paperboard.
The best basis for achieving the desired visual impact
is by using paperboard based on primary fi bres with uni-
formly white-coated surfaces with a high smoothness and
a good print reproduction.
When discussing surface design we usually mean the
exterior or print side of the product. Aspects of surface de-
sign, depending on the product and its use, may also ap-
ply to the reverse side or inside surface. The inside surface
may be printed, as with chocolate and cosmetics cartons,
or it may be important to convey a hygienic image, as with
food and pharmaceutical packaging.
Examples of surface designFeatures which can be used in surface design are de-
scribed below. Often a combination of techniques
is used.
Text and pictures bring the product’s message to the
customer. The shape and colour create an image for the
product. High whiteness together with smoothness give
good print reproduction.
Key paperboard propertiesThe decisive paperboard properties for achieving good
design are:
• printability
• whiteness
• surface smoothness
• ink absorption and drying
• rub resistance
• lightfastness
• strength and elasticity.
47IGGESUND PAPERBOARD | Reference Manual
Design and carton construction
Text, colour and images
Printing
Metallic appearance
Glossy or matt appea-
rance
Relief
Description
Text and pictures bring the product’s message to the
customer. The shape and colour create an image for the
product. High whiteness together with smoothness gives
good print reproduction.
A metallic appearance is effective in giving the product a
luxury image.
A way to attract attention is to create a contrast between
glossy and matt areas of the design.
An overall effect such as a linen fi nish or high relief of
specifi c parts of the design will give the product an
exclusive image.
Achieved by
• choice of paperboard
• print method
• post print fi nishing
• choice of paperboard
• aluminium foil lamination
• metallised polyester fi lm
lamination
• metallic ink printing
• hot foil stamping
• cold foil transfer
• effect varnishes
• choice of paperboard
• varnishing
• gloss PE extrusion
coating
• fi lm lamination
• choice of paperboard
• embossing & debossing
• effect varnishes
Reference Manual | IGGESUND PAPERBOARD 48
Design and carton construction
Structural designPaperboard is widely used for graphics and packaging
applications where its versatile cutting, creasing, folding,
locking and gluing properties, together with its strength,
make it suitable for a wide range of functional and creative
structural designs.
Both creative shape and functional shape are important
aspects of the structural design. Packaging applications
have to meet functional needs, such as protection during
distribution and storage, and ease of handling and display
at the point of sale, as well as fulfi lling the consumer’s de-
mands. Creative design is used for promotional purposes.
The graphics designer has the freedom to use a wide
range of shapes.
Critical aspects of structural design differ depending
on both the conversion and packing processes and also
the ultimate end use. To a converter these are the quali-
ties of stiffness, creasability and fl exibility and the ease
with which paperboard can pass through the conversion
process.
An end user only sees the fi nal carton shape. The critical
aspects are good presentation, effective protection and
durability, when prolonged or extended use is required.
From a sales or promotional point of view the visual appeal
is vital. Structural design provides creative ideas for pro-
moting new products but perhaps the main responsibility
is to provide a functional shape which in the majority of
cases is based on accepted or specifi ed carton shapes.
Popular carton shapesThe potential of paperboard to provide an almost end-
less range of carton shapes is considerable. Some of the
more popular shapes are described in the following table
together with the specifi c requirements these place on
conversion and end use.
Type of carton shape
Simple rectangular or
square carton shape
Hinge lid carton
Simple rectangular or
square carton shape
Description
The rectangular or square cross-section with a large or
main display panel is the most widely used carton shape.
It is based on a simply cut and creased square or rectan-
gular sheet, or blank, of paperboard. The carton is side
seamed, leaving ends which are closed after the product
is loaded.
The product, method of fi lling and the way the pack will
be stored and displayed will have a major infl uence on
the dimensions. The ratio of the sides of the main panel is
usually between 5:3 and 5:4 as these dimensions display
well. This may not be possible if the product is an object or
objects with differing dimensions. The rectangular shape
also makes effi cient use of space in storage, distribution
and merchandising. Shelf stability of the pack will also be
taken into account in defi ning panel dimensions as well as
the facings expected to be made available for display with
products sold through supermarkets.
The dimensions of the unit package also infl uence the
dimensions of the transit outer (secondary packaging) and
the pallet plan. It is worth considering the latter at an early
stage as a difference of a few millimetres in one or two
dimensions can signifi cantly affect distribution costs.
This style of carton is widely used for cigarettes. It includes
a U-card inner frame, which assists the packing of the
product, is part of the unique fl ip-top closure and increases
the compression strength. Security and additional pack
protection is achieved by the use of an overwrapped heat-
sealed clear fi lm.
49IGGESUND PAPERBOARD | Reference Manual
Design and carton construction
Type of carton shape
Flanged and double-
walled carton
Trays
Top load tray erected
cartons
Cartons with windows
and plastic panels
Display outers
Description
These designs give added strength and rigidity. A popular
use is for assortments of chocolate confectionery. They
may have double-walled hinged lids or separate lids and
bases.
Two popular applications are available:
1. Thermo-formed trays made from extrusion-coated
paperboard enabling lids to be applied by heat sealing.
These trays may be slightly tapered. With a heat-resistant
plastic extrusion coating, e.g. PET, these trays are used
for heating chilled and frozen foods in microwave and
conventional ovens. These trays can also be used to
cook bakery products.
2. Shallow trays (25–38 mm deep) with glued or locked
corners to hold groups of cartons or other types of pack-
ages for stretch and shrink wrapping.
These cartons comprise a tray erected carton (glued or
locked corners) with a hinged top flap. The product is
loaded from above, i.e. top load. There are two main types
of closure:
1. The top fl ap has an extended tuck in fl ap feature which
tucks in and can lock into the front panel of the tray. This
type of pack is usually fi lm overwrapped for product pro-
tection and security.
2. The top flap is extended on three edges which fold
down over the outside of three of the sides of the tray
and are sealed by hot melt adhesive. Alternatively, if the
paperboard is PE coated on one or two sides the closure
can be made by heat sealing.
These cartons can be used to show the product inside the
carton. The windows can simply replace cut-outs of the
paperboard in one panel or form part of patented, more
sophisticated systems in which the clear plastic incorpo-
rates creases and replaces paperboard on two or more
sides of the carton.
These cartons may have crash lock or lock end bases and
specially designed top fl aps. The cartons hold a number
of unit packages which are sold individually from the outer
in a point of sale display. The top fl ap and, optionally, addi-
tional portions of the side panels are creased and perfo-
rated so that they can be opened and partly tucked down
behind the product and the back panel, thereby attracting
attention to and promoting sale of the product.
Flanged and double
walled cartons
Trays
1
2
Top load tray
erected cartons
1
2
Display
outers
and plastic panels
Reference Manual | IGGESUND PAPERBOARD 50
Design and carton construction
Type of carton shape
Lined cartons
Cartons with internal
display fi tments
Sleeves
Sleeves with inner
sliding components
Other shapes of paper-
board packaging
Description
In this style a fl exible material (paper/PE, paper/foil/PE,
etc.) is either positioned inside a side seam glued carton
blank by the cartonmaker, or is applied on the packag-
ing line. The base of the barrier material is then sealed
or folded on the packaging line, the base of the carton
sealed, product fi lled, pouch sealed or folded and fi nally
the top carton fl aps sealed or tuck-in closed. Associated
with this type of design are cartons incorporating plastic
ends, tamper-proof, and product protecting diaphragms.
These cartons can be used to protect sensitive products,
they can be gas fl ushed or vacuumised, e.g. for coffee,
and they can be liquid tight or provide protection against
the ingress of moisture vapour.
These have paperboard fi tments inside the carton which
support and display the contents. The carton may have a
top opening hinged or separate lid or it may be a windowed
carton of the types already described. The fitments may
be integral parts of the carton blank or separate structures
added during the packaging operation. Another type of fit-
ment is a divider. These can also be either an integral part
of the carton blank or a separate fi tment.
Paperboard sleeves can be wrapped tightly around other
items, e.g. a ready prepared meal in a lidded tray, “six pack”
for plastic pots or other containers, or pre-wrapped prod-
ucts such as cheese. The sleeves are sealed by either
locking tabs or adhesive.
Typical examples are:
1. matchbox
2. hull and slide cigarette carton.
Typical examples are:
1. triangular shape, e.g. chocolate confectionery
2. hexagonal shape, e.g. chocolate confectionery
3. wallet style, e.g. hosiery
4. tubes, e.g. tubes with paperboard or plastic ends for
products such as confectionery and cosmetics.
Other packages with a high degree of ingenuity in design.
They display the product and often use additional paper-
board fi tments to support the product. Other additional
confectionery products are often incorporated in the
packages. These are usually, but not exclusively, associ-
ated with confectionery and toy packaging where they
have a play value after use. In other product areas they are
associated with gift packing.
is
the carton
Cartons with internal
display fitments
Sleeves
sliding components
Other shapes of
paperboard packaging
1
2
3
4
51IGGESUND PAPERBOARD | Reference Manual
Design and carton construction
Type of carton shape
Cartons for
hanging
Cartons with
curved panels
Blister and skin
packaging
Tubs
Composite
packages
Plastic-coated
barrier cartons
Media
Description
This feature can be incorporated by extending the back
panel of a rectangular fi tment display shaped carton, fold-
ing the panel over and tucking it inside the carton. A hole
may be punched through two thicknesses of paperboard
which may be reinforced with a plastic clip for merchandising.
Interesting shapes can be created with curved creases
or straight creases meeting other creases at other angles
than 90 °. Typical examples are:
1. curved panels
2. round corners.
A printed card, often printed on both sides, is used to
support the product by either enclosing the product in a
plastic tray, the fl anges of which are then heat sealed to
the card or, alternatively, by folding extended panels of
the plastic over the edges of the card or by draping clear
plastic over the product and sealing to the whole area of
the card.
For example ice cream tubs. Tubs of this type may also
have circular paperboard lids.
Granular powder products e.g. retortable packages.
Plastic and foil containing laminates with paperboard.
1. For example milk, fruit juice. Two-side PE coated paper-
board and other plastic foil laminations on paperboard.
2. Cartons with PE on both sides can have heat-sealed
side and end seals which are liquid tight and can give
moisture vapour protection to the contents. These cartons
can also have PE on the reverse only, in which case they
may be sealed with a fl exible diaphragm material having
PE on one side to seal across the end closure.
There are different solutions for covers entirely out of
paperboard. They can have sliding components, a perfo-
rated or die-cut slit or folds that hold the discs.
artons for hanging
ment display
Cartons with
curved panels
12
and skin
ging
Tubs
CD
Reference Manual | IGGESUND PAPERBOARD 52
Design and carton construction
ClosureThe type of closure, opening feature and, where required,
reclosure feature can be chosen from a number of design
options. These features provide security and protection of
the contents during storage, distribution and at the point
of sale and, subsequently, convenience for the consumer.
Types of closure
Glued or sealed end
Tuck end
Lock end
Crash lock
Description
The style shown has full-depth overlapping outer fl aps
with the inner fl aps meeting. This gives a leak-proof style
for powdered or granular products in direct contact with
the paperboard. The inner fl aps never exceed the depth
of the outer fl aps as this would lead to an uneconomical
use of paperboard. The outer fl aps may be shorter than
the depth of the carton, in which case they are known as
economy fl aps. The most common type of adhesive used
is hot melt, although emulsion adhesives are also used.
The position and pattern of the adhesive applied can be
varied to suit the needs of security, opening and reclosure.
Alternatively, if the paperboard is extrusion coated with
PE (or other thermoplastic material) on one or both sides,
secure closures can be achieved by heat sealing, usually
with hot air or direct gas fl ame.
The top fl ap has an extended crease-hinged section which
is folded through 90 ° and simply tucked down into the
carton. With tuck-in fl aps at each end there is a choice of
whether they tuck in on the same side or on the oppo-
site side. Small cuts at each end of the hinged tuck flap
crease give greater security against accidental opening.
For greater security and product protection a heat-sealed
transparent overwrapping fi lm can be used.
An alternative is to overlap a self-adhesive label across
the 90 ° angle between the end and main panel, i.e. over
the tuck-in entry position. It is also possible to position
adhesive between the underside of the tuck-in panel and
the inner fl aps. The tuck-in cannot then be opened without
rupturing this glued area.
1. Used as the base of a carton with a simple tuck-in fl ap
at the top.
2. The carton has extra cuts in each side panel fl ap for
extra security. For greater security and product protection
a heat sealed transparent overwrapping fi lm can be used.
The cartonmaker pre-glues this style, which is quickly
hand erected by the packer. It is usually used as the base
of a carton and can support a considerable weight.
Lock end
1 2
Crash lock
d or sealed, end
53IGGESUND PAPERBOARD | Reference Manual
Design and carton construction
Opening and reclosing featuresThe tuck-end carton clearly has an effi cient method of
opening and reclosure once the overwrapping fi lm or other
method of security is broken. There are several
opening designs for glued-end cartons – some of which
incorporate reclosure features.
Types of opening
Tear strip
Perforation
Pull tab
Perforated press
opening
Glue lines
Perforated panel
Concora
Description
If the overlapping fl ap is full or nearly full depth, a tear strip
with a lead-in tab comprising two intermittent lines of cuts
can be incorporated across the full width of the panel
between the glue line and the flap crease. This design is
not normally used for reclosure, though it can be to meet
special needs.
Both overlapping flaps can be perforated in the same
positions in two parallel lines so that by means of a lead-in
tab both thicknesses of paperboard can be removed. This
method of opening is not suitable for reclosure.
The edge of the outer overlapping fl ap incorporates a tab
to facilitate pulling and tearing – not suitable for reclosure.
A push-in area is perforated in the top of the face panel,
with the perforations extending and widening into the end
panels, so that a clean tear-open is achieved, providing a
partial reclosure.
Normally, the glue line is continuous across the full width
of the end fl ap. If, however, the glue line is not applied in
the middle area, a fi nger can be carefully slid under the
fl ap so that by breaking the glued area to the right and left
it is possible to open the carton. Reclosure is achieved by
inserting a tab in the outer fl ap into a cut in the under fl ap.
A variation of this form of opening is to replace the line of
adhesive with a row of dots of adhesive which more readily
break open. Another alternative allows the use of a con-
tinuous line of adhesive. In this case the underlapping fl ap
is printed and varnished, leaving small areas without print
and varnish such that good adhesion is only achieved over
these areas. The perimeter of these areas can be scored
so that tearing is limited to the areas of good adhesion.
A perforated area in one of the main panels of the carton
can be removed allowing access to the product, e.g. facial
tissues.
Through a scoring (half-cut) on both sides (printed side +
reverse side) of the carton, tear tabs can be worked out,
guaranteeing a fail-safe opening of the packaging without
the assistance of a plastic strip.
The appearance of the sales packaging on the shelf will
not be negatively affected by this scoring.
p
PAPERBOARD
Tear strip Hot-melt adhesiveon underside
Interrupted glue line
Glue lines
Reference Manual | IGGESUND PAPERBOARD 54
Design and carton construction
Conversion, packaging, and graphics fi nishingThe following operations are used by converters, pack-
ers, and graphic fi nishers to make creative and functional
shapes.
Creasing makes the paperboard fold accurately along
well-defi ned lines.
Die-cutting produces a blank for further conversion. It is
usually performed at the same time as creasing. Perfora-
tions can be used to facilitate opening. Tabs and slits can
be cut in separate panels. When tabs are inserted into the
slits a self-locking permanent structure is created.
Folding is usually performed to 90 ° or 180 ° angles.
Gluing means applying glue on a side fl ap, pressing it to
a carton panel and maintaining the pressure until the glue
seam has set. The paperboard is converted to a perma-
nent shape.
Heat sealing, heat and pressure can be used to seal
plastic coated surfaces or surfaces to which a pattern of
hot melt adhesive has been applied in an earlier operation.
Key paperboard characteristics Stiffness is probably the most important property related
to packaging structural design. As we have seen, this
property is closely related to other strength related fea-
tures, such as fi bre composition, particularly in the outer
layers, and thickness.
Important considerations for carton panels are stiffness,
panel dimensions, paperboard grade and fi bre orientation.
Paperboard stiffness is anisotropic with respect to the
machine direction (MD) and cross direction (CD).
Box compression strength is closely related to structural
design requirements.
When packed cartons are stored or transported they are
often stacked in such a way that the boxes are subjected
to compression loading. In practice the strength require-
ment of the fi lled carton is dependent upon:
• Package design, i.e. shape and general strength due to
the structure.
• Whether the contents support the package or not.
• Design and strength of transit package (the outer, etc.)
• Storage and distribution method – palletisation, stacking
and climatic conditions.
• Conversion route – presence of barrier materials may be
relevant in some methods of distribution.
Carton design must take into account the stresses
that are likely to be exerted on creases during the pack-
ing process and also during end use. To this end, creases
must be well formed to avoid premature failure under com-
pression, and must also provide a crease stiffness that is
suitable for the packaging operation. Folded creases and
adjacent panel size must not exert unnecessary stresses
during the gluing operation and subsequent handling and
storage.
Key paperboard properties The following paperboard properties are important for
achieving good structural design:
• stiffness
• tensile strength
• compression strength
• box compression strength
• tear strength
• creasability and foldability
• elasticity
• density
• plybond
• lamination strength (for plastic coatings and laminates).
55IGGESUND PAPERBOARD | Reference Manual
Design and carton construction
Reference Manual | IGGESUND PAPERBOARD 56
Consumer use and appeal
Consumer use and appeal
The efforts of the manufacturers of paperboard, printers,
converters, manufacturers and packers of goods, distribu-
tors, and retailers must ultimately ensure consumer appeal
and satisfaction with cost-effective, effi cient packaging
that has a sound environmental background.
What are consumer needs? All consumers look for
“value for money” and “fi tness for purpose” and require a
clear demonstration of brand values and access to prod-
uct information. The information, form and functions need
to be adapted to demographic groups or individuals with
special needs.
From a consumer’s point of view, the key requirements of
packaging are to promote or provide:
• product declaration
• handling instructions
• brand recognition
• product protection
• oxygen-, light- and moisture barriers
• convenience
• safety in use
• recyclability
• economic use of resources and accurate representation
– not excessive nor deceptive
• a responsible attitude to the environment
• “intelligent” packages
• and to separate and fi x the contents.
Consumers expect packaging to be functional, easy to
handle and safe to use. They require packaging to give
“easy recognition of product”, be “easy to locate” in the
store and refl ect the perceived value. Instructions for use
and disposal must be clear and distinct. These are all ap-
pearance features relating to the material, shape, decora-
tion, and printed matter.
Packages should be tamper evident, especially for food,
gift packages, and products for personal use. Adhesive
joints and opening devices must remain secure. Packages
must not appear damaged or faded on the shelf, this being
equated with old or badly handled stock. Packages which
attract condensation after purchase, i.e. frozen and chilled
food and ice cream, should have good moisture resistance.
With multi-portion packaging the consumer requires
packages which are easy to open, close and reclose,
and ultimately empty the package entirely. A perforated
opening should be easy to tear, whilst a hinged tuck-in fl ap
must not tear after repeated opening and reclosing during
the life of the package.
Packaging should not deteriorate in use or storage, and
proximity to other products should not be allowed to affect
the fl avour or aroma of the product.
An element of “convenience” is necessary depending on
the product and the method of use. This can be achieved
in a number of ways through the material and package
design, depending on the nature and use of the product.
Key paperboard characteristicsAs with retailing, the decisive characteristics are depend-
ent on the type of product under consideration.
The consumer expects packaging to be effi cient and
functional and to meet needs in terms of the appearance
and performance requirements of specifi c products. The
properties of appearance and performance do interact;
thus, for example, a poor appearance usually leads to
a poor performance. Key characteristics as regards
consumer appeal primarily concern the cost effectiveness
of paperboard packaging and its sound environmental
background.
57IGGESUND PAPERBOARD | Reference Manual
Distribution and storage
Distribution and storage
Distribution and storage comprise those activities occur-
ring between the point at which the product is packed and
its ultimate point of sale in the retail store, supermarket,
vending machine, pharmacy, etc.
At the end of the packing line the packages are collated
by hand or by machine in groups of 6, 12, 24, etc. for
packing in a transit package. This may comprise:
• A shallow-depth paperboard tray which is subsequently
stretch or shrink wrapped in fi lm.
• An open-ended corrugated fi breboard sleeve which is
subsequently stretch or shrink wrapped in fi lm.
• A corrugated case with glued or taped closure. There is
also a shelf-ready corrugated case which has a crocodile-
type opening and is designed to go directly on the super-
market shelf.
• A unit of 6/12/etc. packs simply shrink wrapped in fi lm
with no additional paperboard protection.
These transit packages are usually palletised, alternate
layers being packed in a different pattern or plan to give
stability to the load. The pallet load may be further stabi-
lised with strapping or stretch fi lm.
Standard retail pallets are reusable with a common size
being 1000×1200 mm.
Pallet loads are stored in warehouses which may or may
not be heated. Frozen and chilled foods are stored in ap-
propriate conditions, i.e. –20 °C to –35 °C for frozen prod-
ucts and 0 to +3 °C for chilled products. Storage is usually
freestanding, limited to two pallets high, or in racking.
It is unusual for full pallet loads to be delivered directly
from the manufacturer to the retail store except in the case
of very large stores. Pallet loads are usually distributed to:
• Distribution warehouses of major retail organisations.
These are strategically placed to meet the stocking
requirements of a number of the company’s stores in a
given area. Mixed loads are “picked” or made up to meet
the needs of the respective stores. This means that mixed
numbers of transit packages of different products are
placed in special cages, often in a somewhat random ar-
rangement.
• Distribution warehouses of companies which are inde-
pendent of both the manufacturer and the retail stores.
The procedure for distribution is the same as that de-
scribed previously.
• Distribution warehouses of independent cash and carry
companies. These companies display pallet loads of
goods in bays or racking allowing small retailers to pick the
goods for themselves. This type of distribution has led to a
more attractive cash and carry transit package, e.g. shrink
wrapped to allow the more attractively printed individual
cartons to be seen, or by the use of pre-printed white lin-
ers for corrugated cases.
Key paperboard characteristicsThe main requirement of both the individual carton or
other forms of packaging is for stacking, handling, and
transit protection. Stacking requires vertical compression
strength. That may be assessed under static or dynamic
loading on a pallet, a transit package or an individual pack-
age. Handling of transit packages requires strength to
resist impact and uneven compression in mixed loads.
Transport hazards usually refer to impact and can be
checked on sliding planes or by drop testing. Some sensi-
tive products may need special cushioning protection and
the needs can be assessed on variable frequency vibration
tables and by the use of special records in practical transit
tests. Vibration can cause damage to the package by
scuffi ng or rubbing adjacent surfaces.
These requirements may also have to be met in frozen
(–20 °C to –35 °C), chilled (0 to +3 °C), very damp or wet
conditions, or very hot and dry conditions.
Key propertiesIn general the strength-related properties are:
• grammage
• thickness
• moisture content
• stiffness
• compression strength (short span)
• box compression strength
• water resistance (frozen and chilled food distribution).
Distribution and storage in practiceThe following factors are essential to good distribution and
storage:
• The strength of paperboard
• The structural design of the unit package
• The nature of the product, i.e. if it contributes to the
strength of the package
• The strength and structural design of the transit package
• The pallet plan. The dimensions of the unit transit
package can now be examined by computer to give the
optimum utilisation of the pallet volume. This also leads
to the best stacking performance as a result of close and
interlocked packing on the pallet.
Some additional comments are, however, necessary for
particular conditions of storage and distribution, see the
following page.
Reference Manual | IGGESUND PAPERBOARD 58
Distribution and storage
Distribution and storage conditions
Frozen food and ice cream
Chilled food
Very damp or wet conditions
Very hot conditions
Descriptions and actions
The storage temperature will be around –20 °C. The printed or varnished
print must not craze at this temperature.
The storage temperature is 0 to +3 °C and the main hazard is the very high
relative humidity which raises the moisture content of the paperboard with
a consequent loss of stiffness and strength. There are a number of ways of
reducing this effect such as by using a tight sleeve where the product is in a
plastic or aluminium foil tray, or by packing the product directly into a plastic
coated paperboard tray with a printed heat sealed plastic coated paper-
board lid. The paperboard can be made more resistant to moisture by:
• Hard sizing all layers of the paperboard, thereby improving its edgewise
wicking tendency.
• Functional coating with plastic, aluminium foil, wax or moisture resistance
varnish.
The paperboard can be given enhanced moisture resistance as discussed
under “Chilled food”. These conditions also demand a coating on the paper-
board and a choice of compatible inks and varnish with good keying, wet
rub, and scuff resistant properties.
Here the main problem to arise is blocking, i.e. the sticking together of
sheets or packages. It is avoided by the choice of a suitable paperboard
coating and compatible non-blocking inks and varnish.
SummaryAppearance needs are provided by surface and structural
design. Performance needs relate to printing, conversion
and use. This may involve special protection or functional
requirements relating to the paperboard product or to any
other products with which it may be in contact, or to the
handling, storage and use of the product.
Design in the broadest sense highlights every need which
must be incorporated into the choice of paperboard for every
graphical or packaging product.
59IGGESUND PAPERBOARD | Reference Manual
Edge water absorption, Wick testIn many wet applications such as deep-freeze packaging,
or for drinking cups, a higher degree of water resistance
is needed. Examples of the most demanding applications
might be the packaging of hot spinach, or cups for tea
or coffee. Even if the inside of the package or the cup is
plastic coated, the edges normally remain exposed. The
Wick test is the method commonly used to evaluate water
absorption via the paperboard edges.
The mechanism involves capillary attraction, which is
reduced when the paperboard has been treated with a
sizing agent. As only the paperboard edges are involved in
this test, the internal sizing of the paperboard and also the
type of fi bre in use are of major importance.
The test sample is covered on both surfaces with a
waterproof tape and cut to a specifi c size. The sample is
then weighed before being placed in water at 80 °C, so
that water can only be absorbed through the edges. After
20 minutes the sample is weighed again and the increase
in weight recorded as the Wick test value in kg/m². This
wicking test is used for testing of Solid Bleached Board
products.
Surface water absorption, Cobb testThe Cobb value quantifi es the amount of water absorbed
via the paperboard surface during the Cobb test.
In the offset litho printing process, where water is used,
there is a need for some degree of water holdout. For
packaging applications for deep freeze/ chilled foods the
requirements can be demanding.
The paperboard sample is weighed and a cylinder with
a cross sectional area of 1 dm² is placed on the sample.
Water (100 ml) is poured into the cylinder. After 1 minute
the cylinder is emptied and excess water blotted from the
surface. The weight increase is registered as the one-
minute Cobb value in g/m².
The test can be used for the outer surfaces as well as
the internal layers of a multi-ply paperboard. The centre
plies are tested after delamination of the outer plies.
Hard-sized Folding Box Board products, where the
middle plies are additionally treated to give high water
resistance for deep-freeze and chilled food applications,
are tested using an extended time. The commonly speci-
fi ed time is 3 minutes, with the test also performed on the
middle plies, in addition to the outer plies.
On pigment coated surfaces water absorption is to a
large extent dependant on the coating composition. For
uncoated surfaces internal sizing and composition of the
surface size are important.
The internal sizing of fi bres is of vital importance in slow-
ing down the water absorption of the centre plies.
Distribution and storage
Covered surface
Open edge
Reference Manual | IGGESUND PAPERBOARD 60
Retailing
Retailing
Retailing comprises the activities involved in offering
goods for sale to the general public.
In most cases the consumer can inspect the product
and choose at the point of sale, stores and supermarkets.
Retailers often market their own private brands alongside
other producers’ branded products. They are therefore
involved in all the aspects of package specifi cation, includ-
ing the choice of paperboard.
In case of mail order, internet sales, vending machines
and the issuing of prescription medicines in pharmacies,
the customer does not handle the goods prior to pur-
chase. Packaging protection and information are vital to
meet functional needs and emotional satisfaction (post-
purchase satisfaction). The package is the last part of the
brand communication chain, as it is often kept for storage,
e.g. CDs and perfume bottles.
The retailing requirements of a package are listed below:
• Brand appeal.
• Transit packages for packaged and graphical products
must arrive in good condition, thereby ensuring that the
contents are also in good condition.
• The transit packages should be convenient for transpor-
tation, handling, opening, and recycling.
• Unit packages should be convenient for stacking and
display. They should be shelf-stable and make optimum
use of the space available.
• Unit packages should have structural and graphical
designs which promote the product. The graphics should
be appealing, distinctive and informative.
• Unit packaging should provide appropriate protection for
the product to prevent damage and maintain the quality of
the contents.
• Unit packages should conveniently conform to the needs
of the retailer in respect of store handling,
e.g. bar codes, ability to apply labels, provide tamper
evidence, safety in handling and in packing at check-outs.
Equally, the requirement to complete the sale safely and
conveniently applies to mail order, internet sales, vending,
and prescription dispensing.
• Primary and/or secondary (display trays) packaging
needs to conform to the retailers’ shelf space standards
and to their standard transit packaging sizes.
Key paperboard characteristicsThese characteristics will vary depending on the type of
product being considered. Guidance is given for major end
uses at www.iggesund.comwww.iggesund.com.
In general the paperboard characteristics necessary will
be those providing promotional and protective features.
These features may vary from surface and structural
appearance to box compression strength and taste and
odour neutrality.
Key propertiesKey paperboard features for the retailing process:
• Print reproduction (whiteness, gloss, smoothness)
• Product protection (stiffness, compression strength,
tearing resistance, water absorption, taste and odour
neutrality)
• Designability (Good creasing, embossing and folding
characteristics, gluability)
• Wide grammage and thickness range enables a well-
adapted choice, depending on protection and perform-
ance need.
There is also an important environmental dimension for
the manufacturer and retailer to consider which is con-
sumer driven. Certifi cation schemes, such as PEFC and
FSC, have been introduced to ensure a sustainable chain
of custody from the forest to the consumer. Details regard-
ing certifi cations are available on www.iggesund.comwww.iggesund.com.
61IGGESUND PAPERBOARD | Reference Manual
Taint and odour neutrality
Taint and odour neutrality
One purpose of a package is to protect its contents from
damage. For many products, such protection also in-
cludes preservation of the product’s fl avour. The package
itself must not contribute to any unacceptable alterations
by releasing or absorbing odorous substances which
could affect susceptible products such as cigarettes
and chocolate.
Odour from paperboard can arise from a number of
sources such as wood resins from mechanical pulp or
residual chemicals from chemical pulp. During the produc-
tion of the paperboard, biological activity may produce
odorous substances. Furthermore, the coating contains
synthetic binders, and there is a risk that these impart an
odour to the paperboard.
Mechanical and chemical pulps are selected to mini-
mise odour and steps are taken within the mill to eliminate
biological activity in the machine systems. The paperboard
is tested on a regular basis to ensure that the risk of taint-
ing of food is minimised. In addition, coating materials are
subject to stringent specification and control to reduce
tainting risks.
Experience has, however, shown that by far the greatest
risk of tainting of sensitive products by cartons comes
from the printing ink or varnish residues remaining in the
paperboard after printing. Ink solvents and vehicles are
often absorbed into the paperboard and may be absorbed
by the fibres only to be released later. Paperboard may
also absorb odorants during storage, and care should be
taken to store the paperboard in an odour-free area prior
to printing.
Different printing methods can cause odour problems to
varying degrees. Classical offset ink, based on drying oils,
develops large amounts of volatile substances when dry-
ing. It is essential that the printed sheets are well dried and
well aired to prevent problems. Modern “odourless” offset
inks, which reduce these risks, are available.
UV curing of offset inks is sometimes used to obtain a
very high gloss. In case of insuffi cient or irregular curing
this printing technique can cause odour problems. Grav-
ure printing is often considered the safest method to avoid
odour problems provided the solvents are carefully chosen
and the drying is suffi cient.
To detect and measure volatile and possibly odorous
substances in paperboard or paperboard cartons, gas
chromatography is often used. Ideally, each volatile sub-
stance in the sample is represented by a peak in the chro-
matogram and the peak area indicates the concentration
of the substance.
The paperboard choice Paperboard that will be used for the packaging of sensitive
goods such as foodstuffs or tobacco should be tested to
ensure that it meets required taint and odour standards.
As mentioned earlier, the surface coating composition and
pulp are some possible sources of odorous substances in
the paperboard. Printing inks can also cause odours and
different printing methods show major differences in odour
contribution.
Both Folding Box Board (where mechanical and chemi-
cal pulps are used in combination) and Solid Bleached
Board (where only pure chemical pulp is used) consist of
primary fi bres, which means that their contents are known.
Chemical pulp offers the least contribution to taint and
odour.
Time: 16,997 MinutesTYPICAL CHROMOTOGRAMS: WLC, FBB and SBB
Reference Manual | IGGESUND PAPERBOARD 62
Characteristics of taint and odour neutrality A paperboard carton must be as free as possible of odor-
ous substances which could originate from:
• the pulp used in the paperboard
• the coating of the paperboard
• extrusion coating
• printing, lamination or other conversion steps.
Assessment of taint and odourAn optimised paperboard package will not interact with
its contents in such a way that their odour and fl avour are
changed. In order to be regarded as a good performer with
regard to taint and odour, a paperboard must therefore
have a very low concentration of odorous substances.
Different pulp and coating characteristicsBleached chemical pulp contains cellulose and only traces
of impurities. These are small amounts of fatty acids, resins
and other impurities which could create odour problems.
Fatty acids will oxidise in storage, if present, and develop
a “woody” or even rancid odour.
Mechanical pulp contains large amounts of lignin (wood
substance) and resins containing fatty acids. A paperboard
based on this type of pulp could contribute to taint and odour
risks, but these can be diminished with a proper manufac-
turing technique and screening.
Primary fi bres can be fairly well controlled but second-
ary fi bres are often of unknown origin and have undergone
various converting stages such as printing before being
reclaimed and reused. This means there is a considerable
Taint and odour neutrality
Chromatogram of unprinted paperboard
Chromatogram of printed paperboard
63IGGESUND PAPERBOARD | Reference Manual
Taint and odour neutrality
risk of inconsistency in the amount of contamination and
impurities in the paperboard, leading to variations in the
board’s taint and odour characteristics. A paperboard
based on recycled fi bres is therefore not recommended
for the packaging of sensitive products.
Most high-class packaging boards have a pigment
coating to ensure good printability. The binders in the
coating are normally latices, which may contain various
organic substances as impurities. Some of these could
create odour problems and must be carefully controlled.
Key propertiesFor paperboard and cartons to be taint and odour neutral,
the following features play a crucial role:
• primary fi bre
• the coating ingredients
• the plastic coating
• the printing method used.
Measuring equipmentThe most sensitive instrument available to measure the
odour and/or flavour of a substance is a human being.
Only humans can describe an odour or a flavour. The
members of trained panels assign numerical ratings and
record their impression of tainting flavours or volatile
odours experienced. By using no fewer than eight asses-
sors, accurate and objective results may be achieved.
A number of sensory test methods are available. The
choice of test method is dependent on factors such as the
specific issue (e.g. type of products, type of questions)
and how quickly the results are needed.
Instrumental techniques are valuable complements to
the human assessments. Headspace sampling combined
with gas chromatography (GC) is used to measure chemi-
cal compounds that are released from the products. To
identify the compounds, this method is combined with
mass spectrometry (MS).
In headspace sampling, the volatile substances that
are released are collected in gas form. In GC the volatile
substances are separated through differences in boil-
ing points and absorption rates in the GC column. Their
concentrations are recorded with a detector, normally a
fl ame ionisation detector (FID). However, the instrument
cannot differentiate between odorous and non-odorous
substances. To solve this problem it is possible to split the
gas stream after the separation and lead one part to the
instrument. The other part is led to a person who sniffs the
gas stream and notes whether there is a noticeable odour.
Quality controlFor quality control two methods may be used. The fi rst
uses a panel which compares the outturn sample (either
fi nished product or raw material) with a reference. In the
second a gas chromatogram is run to detect any new
peaks indicating contamination or to note major changes
in the concentration of known odorous substances.
When evaluating a gas chromatogram it is important
to select compounds which are known as risk factors if
they occur above the detection threshold. These com-
pounds are of course different for different applications;
for instance, cigarettes and chocolate are susceptible to
different compounds.
Sampling and sample handlingTo achieve proper measurements attention must be paid
to the sample handling. Due to the sensitive nature of this
type of analysis some important issues are to avoid per-
fume and perfumed soap before handling the samples and
to use proper aluminium foil as protection for the samples.
Please consult the Laboratory for Sensory and Chemical
Analyses for advice.
Iggesund Paperboard’s Laboratory for Sensory and
Chemical Analyses is accredited (accreditation number
1740 ISO/IEC 17025) for the following analyses:
Type of test
Robinson EN1230-2
Odour EN1230-1
Difference testing Triangle
test (ISO 4120) Duo-trio
test (ISO 10399)
Methods
Intensity of taint resulting
from interaction material –
test medium.
Odour intensity of the
materials.
Pair-wise comparison
(mod. ISO 5495).
Type of information
Scores (0 – 4)
Scores (0 – 4)
The certainty of that there
is a difference.
Remark
The standard test medium
is ground chocolate but
other media can be chosen.
The materials are put into
glass flasks and subse-
quently the air of the glass
fl ask is smelled.
Two samples are compared.
Can be applied both to taint
and odour.
Reference Manual | IGGESUND PAPERBOARD 64
Gas chromatography principle
Taint and odour neutrality
TAINT TEST
PROCEDURE
(LSCA)
Stored in jarroom temp, 2 days
Pieces equal to2 A4 sheets are cut into strips
VARNISH
PAPERBOARD
INK
FOOD SIMULANT (CHOCOLATE)placed in indirect contact with the sample Chocolate assessed
C 100%M 100%Y 100%B 100%
92
51
31
CARRIER GAS COMPUTER
COLUMN OVEN
COLUMN
INJECTOR
DETECTORSAMPLEA/D
CONVERTER
CHROMATOGRAMS
65IGGESUND PAPERBOARD | Reference Manual
Migration into foodstuffs
Migration into foodstuffs
The maximum amounts of substances allowed to migrate
into packed foodstuffs are limited by regula tions that have
been sharpened in recent years. To ensure that our board
materials fulfi l the stipulated requirements, migration tests
are performed. These tests bring different types of food
simulants into contact with the board and then store them
for specific time periods at a specified temperature. The
type of test food and the choice of time and temperature
depend on the intended use of the packaging materials.
After this contact period, the amounts of substances
that have migrated into the food simulant may be weighted
(resulting in an estimate of total migration) or specifically
analysed (resulting in identifi cation and quantifi cation of
the substances).
The limits apply to packaging materials made of several
components. It is important to realise that while the board
is often the basis of the packaging, other components
such as printing inks and varnishes may contribute con-
siderably to the migration.
Specifi c methods may also be used to analyse amounts
of certain substances, such as optical bleaching agents,
that are not well quantified when applying the more gene-
ral migration tests.
MIGRATION TEST
PROCEDURE
(FABES)
Stored in migration cell
1 dm² is cut Migrants identified and quantified (GC)
VARNISH
PAPERBOARD
INK
FOOD SIMULANT (TENAX)placed on the sample
Migrants dissolvedin solvent
40°C10 days
C 100%M 100%Y 100%B 100%
MIGRATION TEST PROCEDURE (FABES), OBA:s
ETHANOL+WATER
1 g cut paperboard OBAs in extract quantified (UV-spectrum)Stored at 60°C, 2 days.Migrants are extracted
PAPERBOARD