Pira International Ltd-Introduction to Flexible Packaging-iSmithers Rapra Publishing...
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Introduction to Flexible PackagingNnamdi Anyadike
Published by
Pira International Ltd
Randalls Road, Leatherhead
Surrey kt22 7ru
UK
T +44 (0) 1372 802080
F +44 (0) 1372 802079
W www.piranet.com
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The facts set out in this
publication are obtained from
sources which we believe to be
reliable. However, we accept no
legal liability of any kind for the
publication contents, nor any
information contained therein
nor conclusions drawn by any
party from it.
No part of this publication may
be reproduced, stored in a
retrieval system, or transmitted,
in any form or by any means,electronic, mechanical,
photocopying, recording or
otherwise without the prior
permission of the Copyright
owner.
Copyright
Pira International Ltd 2003
ISBN 1 85802 915 5
PublisherAnnabel Taylor
Customer services manager
Denise Davidson
T +44 (0)1372 802080
Typeset in the UK by
Jeff Porter, Deeping St James,
Peterborough, Lincs
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Contents
List of figures vCurrency conversions vi
Raw materials and production 1
Petrochemicals 1
Prices 1
Naphtha 2
Ethylene 4
Cellulose 4
Chemical pulps 5
Sulphate (kraft) pulp 5
Cellulose film 5
Paper 6
Flexible packaging papers 6
Aluminium foil 7
Flexible materials 9
Polyolefins 11
Types of flexible plastics 13
Other materials 14
Conversion of flexible plastics 14
Polyethylene 15
Cast PP 16
PA 16
PET 17
PVC 18
Cellulose 18Barrier packaging materials 18
Ethylene vinyl alcohol 19
Polyacrylonitrile films 19
PCTFE 19
PVOH, metallised films 19
Polyethylene 19
Polypropylene 19
Polyvinylidene chloride: example
Saran 19
High-barrier substrate materials 20
EVOH 20PVdC 21
Some polymer developments 22
Metallocene polymers 23
Flexible packaging implications 25
Fruit and vegetables 26
Development drawback process, cost,
patent concerns 26
The technology 28
Competition 29
Other polymers 29
Biopolymers 30
Aliphatic polyketones 30
Liquid crystal polymers (LCPs) 30
Films 31
Film type and manufacture 31
Cast film 31
Blown film 32
Multilayer (high-barrier) film 33
Coextruded film 34
Laminated film 35
Metallised film 37
Intelligent/smart films 38
Oriented polystyrene films 39
Microwaveable films 39
Edible and soluble films 39
Downgauging 39
Innovations in flexible materials 41
Modified atmosphere packaging 41
Commercial examples 43
Active packaging 43
Fresh foods 44
Processed foods 44
Systems 44
Other developments 46
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Introduction to Flexible Paclaging
Contents
Barrier films 48Intelligent packaging 49
Intelligent plastics for packaging 49
Antimicrobial film 49
Antimicrobial packaging films 50
Flexible-based retail units 53
Pouches 53
Commercial examples 54
Lidding 59
Bags 61
Bag-in-box packaging 62
Stick packs 62
Reclosable devices 63
Flexible cans 65
Shaped bags 66
Sacks 67
PE sacks 67
Heavy duty PE sacks 67
Multipacks 68
Wrapping film 69
Shrink sleeves 70
Label market 72
Printing of flexible packaging 73
Gravure 73
Flexo 75Lithography 77
Digital printing 79
Flexible packaging machinery 85
Calendering 85
Extruding 86
Blown film extrusion 88
Slit die-cast extrusion 89
Coextrusion 89Thermoforming 90
Vacuum forming 91
Pressure forming 91
Thermoform-fill-seal 91
Lamination 91
Metallised film 93
Aluminium 93
Form/fill/seal 93
Legislative issues 97
Food contact materials 97
Current activities possible future 98
Recycling 99
European legislation 99
National legislation 100
End-use markets 107
Fresh food 107
Meat and poultry 107
Vegetables 108
Frozen food 108
Frozen potatoes 109
Soup 109
Cheese 110
Baked products 110Bread 110
Snack foods 112
Biscuits 112
Cakes 112
Coffee and tea 112
Confectionery 113
Dried foods 113
Pharmaceuticals 114
DIY 115
Household detergents 115
Labelling 115
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List of figures
2.1 Monomers 122.2 The evolution of metallocene olefin
polymerisation catalysts 23
5.1 Structure of the flexible spout
pouch 53
5.2 Dual chamber pouch 54
5.3 Structure of the dispenser pouch 55
5.4 The design of Procter & Gambles refill
pack for liquid detergent 55
5.5 A resealable pouchs unique structure
gives easy peel and reclosure 57
5.6 Unique structure of a resealable
pouch 56
5.7 An alternative adhesive closure 57
5.8 The concept behind Amcor Flexibles
Europes EasyPack system 63
5.9 The Amcor FlexCan family 66
5.10 Film structures for pharmaceutical
blister packs 69
6.1 Schematic of a webfed gravure
printing unit 73
6.2 A conventional flexographic printing
unit 76
6.3 The blanket-to-blanket configurationused on perfectors and webfed offset
presses 78
6.4 Typical layout of a sheetfed offset
press 79
6.5 Multiple nozzle, continuous inkjet
printing mechanism 80
6.6 Continuous inkjet printing
mechanism 81
6.7 Impulse (or drop-on-demand) inkjetprinting mechanism 81
6.8 Dry toner electrophotographic (laser)
printer 82
7.1 Four-roll inverted L calender coater 85
7.2 Schematic of a simple extruder 86
7.3 Schematic of a simple extruder 88
7.4 Thermoforming techniques 90
7.5 Cross-section of a typical
lamination 92
7.6 Wet method lamination 92
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Currency conversions
$1 = 0.95
1 = 1.52
1 = 0.008
Ffr1 = 0.15
Fmk1 = 0.17
Esc1 = 0.005
Skr1 = 0.11
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Raw materials and production
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Flexible packaging normally refers to the manufacture, supply and conversion of plasticand cellulose films, aluminium foils and papers. These may be used, separately or in
combination, for: primary retail food packaging and labelling; non-food applications, such
as DIY and household detergents; and certain other specialist non-food niche sectors, such
as medical and pharmaceutical packaging. This chapter endeavours to explain in simple
terms, the basic primary production method of polymers used to make plastics for flexible
packaging from raw materials.
With the exception of regenerated cellulose film and cellulose acetate, with its sub-
variants, all plastics are ultimately based on petrochemical feedstock. Consequently, the
price of raw materials for flexible packaging is very dependent on the price of crude oil.
PVC is a special case as about 50% by weight is accounted for by chlorine, which isavailable from salt or seawater. The main building blocks for producing plastics are
ethylene and propylene, which is obtained from one fraction of the feedstock via catalytic
crackers of petrochemical refineries. Plastics manufacture accounts for only a small
proportion (about 4%) of total world oil consumption.
However, while this pattern has not changed greatly in the past it may well do so if
other end users switch to other forms of raw material or energy sources. The fact remains
that while the flexible packaging industry is not very important to the oil industry, the oil
and downstream, refined products industry remains hugely important to the flexible
packaging industry.
Petrochemicals The supply of crude oil to markets in both the developed and developing world is
surprisingly free from disruption considering the fact that a large portion of it comes from
Prices regions that are inherently unstable, such as the Middle East and Africa. For much of the
1980s, two of the Organisation of Petroleum Exporting Countries (Opecs) major
producers, Iran and Iraq, were at war with one another and, as of the fourth quarter of
2002, all the signs were that the US was about to launch a second war against Iraq.
However, while supply has tended to be unaffected by events in the Middle East, oil
prices have long been subject to volatility. This volatility, which affects ethylene
production costs and thus the price of a key polymer for the flexible plastics packaging
industry, helps to explain the various ways that the industry is attempting to introduce
more cost-effective ethylene production.
Throughout 2002, the crude price of oil has been subject to a number of spikes and
dips in response to sluggish world demand, quota-busting by Opec members, scarce
commercial inventories, government stock-building and the prospect of war against Iraq.
In January 2002, a barrel of Brent crude fetched $17.52; this rose 70% to just under
$30 at the end of September amid fears of war in the Gulf. Then during October the price
of crude fell back 11% as the threat of war appeared to recede.
As a result of the soft demand, supply slumped in 2002 as 4 million barrels a day
were taken off the market. Opec has made progressive cutbacks over the 18 months toNovember 2002 in a bid to bolster the price of oil.
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The Centre for Global Energy Studies (CGES) forecasts that Opec will be forced to cut backits production to 25.3 million barrels a day in 2003 compared with 27.1 million barrels in
2002. Saudi Arabia, as keeper of the oil surplus, has cut the bulk of this, and other
countries quotas have been reduced in proportion to their production.
Meanwhile, commercial US crude oil stocks were at their lowest level in November
2002 since US energy authorities began keeping weekly records in 1979. Stocks are
normally high ahead of winter in Europe and the US. The shortage suggests that prices
could spike in 2003 if the winter is especially cold.
However, other industrialised nations have been quietly building up oil stocks to deal
with any supply interruption during a conflict with Iraq. The US, Japan and Germany hold
a total of3.8 billion barrels in stock, some 114 days of net imports. President Bush hasalready announced that the US is seeking to fill its strategic reserves. Nippon Oil of Japan
has started to buy crude from Russia as well as the Middle East.
Should oil prices, as seems likely, rise further in the current economic climate then
most upstream industrial activity will be affected. High oil prices will feed into inflation,
hamper industrial productivity and, in industries such as flexible plastic packaging where
oil is a key raw material, the pressure on costs will be severe.
Naphtha The term naphtha is usually restricted to a class of colourless, volatile, flammable liquid
hydrocarbon mixtures, one of the more volatile fractions obtained from the fractional
distillation of petroleum (when it is known as petroleum naphtha). It is widely used as a
solvent for various organic substances, such as fats and rubber, and in the making of
varnish. Technically, gasoline and kerosene are also naphthas.
Naphtha is also a feed in olefin production in the production of propylene and
ethylene, roughly in a ratio of3:1. If, however, the concentration of n-paraffins in the feed
can be increased, the yields of ethylene relative to the feed can be substantially higher, up
to3839% or more. With the reduced margins that most steam crackers are forced to
operate under, cost reductions and improved yields are seen as essential.
Naphtha is the most common feedstock sent to naphtha cracking units for the
production of ethylene. A typical naphtha feedstock contains a mixture of paraffinic,
naphthenic and aromatic hydrocarbons with varied molecular weight and structure. The
composition of naphtha feedstocks varies considerably, yet the composition has a
significant impact on ethylene and by-product yields.
If a high ethylene yield is required, then it is preferable to have a high concentration
of normal paraffin in the naphtha. Normal and non-normal paraffin decomposes to
ethylene in a cracker, but the ethylene yield from normal paraffin is much greater.
Coincidentally, refiners and aromatics producers prefer naphtha feedstocks that are
depleted of normal paraffin. Naphtha that is depleted of normal-paraffin contributes
more octane value to the refiners gasoline pool and increases the aromatics yield in an
aromatics complex.Ideally, ethylene producers would use naphtha with a high normal paraffin
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concentration, and refiners and aromatics producers would use naphtha that is depleted
of normal paraffin to increase their yields. However, relatively few steam crackers,
particularly in Europe, are in a position to increase their yields. The main limitation is a
lack of suitable opportunities for process integration that not only reflect the increased
yield in ethylene but also provide for the enhanced utilisation of the remaining
components: isoparaffins, naphthenes and aromatics.
New technologies coming onstream seek to incorporate a processing unit that can
effectively separate n-paraffins from the remaining hydrocarbon components present in
the naphtha feed.
Vapour-phase IsoSiv units were used to enrich the feed to steam crackers as far
back as 1967. Various designs and operating modes were used for such units. In general,
however, these units had fairly high utility and operating requirements and there has been
little interest in the use of this technology in recent years.
Recently, UOP LLC introduced a new approach, the MaxEne process for maximumethylene production, which is an extension of the Molex processing concept. MaxEne
Introduction to Flexible Packaging
Raw materials and production
Petrochemicals The simplest alkene, with two carbon atoms, ethylene is a colourless flammable gas. It is
glossary made industrially by the cracking of a fraction, typically naphtha, from the fractional
distillation of petroleum. It is often used in the manufacture of other chemicals. For
Ethylene (C2H4) example, direct hydration of ethene gives ethanol, whereas oxidation gives epoxyethane
and thence ethane-1,2-diol (common antifreeze). Polymerisation gives polyethylene (PE).
Cracking Cracking is the process whereby a large molecule is broken down into smaller
molecules. The starting molecule is often an alkane from the fractional distillation
of petroleum and the product molecules are smaller alkanes and alkenes, such as
C8H18 >> C6H14 + C2H4.Thermal cracking involves heating the alkane to between 800 and 1000C,
sometimes in the presence of superheated steam. The reaction mechanism involves
radicals. Another type of cracking is catalytic cracking (or cat-cracking). This does not
require such high temperatures, 500C being common, but does require a catalyst, such
as silica (SiO2) or alumina (Al2O3). The mechanism is less certain but may involve
carbocations. The biggest difference is that the carbon skeleton suffers more
rearrangement in catalytic cracking. This is put to good use in reforming.
Naphtha A fraction of petroleum obtained by fractional distillation. Different oil companies use
different names for the fractions which have five to ten carbon atoms; the range from
five to eight is often termed gasoline and that from nine to ten naphtha. Naphtha
contains mainly alkanes, both straight-chain and branched. It is currently the favourite
feedstock for further refining by cracking.
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operates in the liquid phase and was developed for the separation of n-paraffins in theC6C12 range or as required (more often C5C8 or C5C10) as feed to steam crackers for the
production of ethylene.
The recovery of n-paraffins from a MaxEne unit are claimed to be very high, typically
more than 90%. But while single-pass ethylene yields with the MaxEne unit have
increased by over30% the yields of propylene remain largely unaffected.
Ethylene Ethylene is the primary building block for many of the plastics we use every day. Ethylene
is used to produce PE plastics from which a number of plastic packaging items are made.
Ethylene is also used in other plastics, such as polystyrene (PS), polyester and acrylics, and
is the main ingredient in ethylene glycol antifreeze.Ethylenes role in flexible packaging is crucial. Indeed, the raw material for all
packaging plastics is ethylene. Ethylene is a gas derived from natural gas or from a
fraction of crude oil that has a composition similar to natural gas. Both natural gas and
crude oil are products of fossils and are therefore non-renewable.
Producing and refining ethylene uses a lot of energy, requiring combustion to achieve
high reaction temperatures and refrigeration to achieve extremely low temperatures to
condense and separate gases (down to about -260F. Largely because refrigeration is
inherently mechanically inefficient, producing ethylene consumes at least 20 megajoules
(MJ) per kilogram of ethylene produced 20MJ would run a 100W light bulb for 56 hours.
Much of this energy is generated at the production site by burning some of the
feedstock of natural gas or crude oil.
Once ethylene has been produced, it is combined with solvents, comonomers,
additives and other chemicals that will participate in the planned chemical reactions.
The mixture is then subjected to a chemical reaction called polymerisation which creates
long-chain molecules. (Mono means one and poly means many, so a monomer is
a single molecule like ethylene which can be bound with other molecules to form
a polymer.) The new polymer is extruded, pelletised, or flaked and the product is called
a resin. Resin is sold, re-extruded, and made into containers, films and other products
(see Chapter 2).
Cellulose This bio raw material is used to make paper and film, both of which are used as flexible
packaging materials. Paper is made of pulp that is mostly cellulose. The cellulose is
usually derived from various vegetable fibres, chiefly cotton and linen, or from wood pulp.
The pulp and paper industry uses several processes to convert wood fibre into
cellulose pulp, which is then manufactured into paper, newsprint, cardboard and
thousands of other products. The basic pulp process reduces wood to fibre by mechanical
means or by heating in chemical solutions. To make paper, the fibres are mixed with water
and extruded in continuous sheets, which are pressed and dried.
Pulp is the product of the mechanical or chemical breakdown of fibrous cellulosematerials, more or less into component fibres. When mixed with water the mass of fibres
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can be spread as thin layers of matted strands. When the water is removed the layer offibres remaining is essentially paper, although in practice other materials may be added to
give the paper a better surface for printing, greater density or extra strength, as is the
case for cardboard used in packaging, etc.
Chemical pulps The principal aim of chemical pulping is to remove lignin and other materials that bind
individual cells together, so making fibres directly available for papermaking. Fibres are
less likely to be damaged in chemical pulping than in other pulping processes.
Chemical pulping requires a significant amount of energy, mostly for process heat but
uses less electrical energy than mechanical processes. However, many modern kraft pulp
mills are totally self-sufficient in energy, with the combustion of residues and wasteproducts meeting all heat and electrical needs.
Sulphate (kraft) pulp This process, where chips are cooked in a mix of more or less equal parts of caustic soda
and sodium sulphide, is an improvement on the soda process.
Kraft pulp is used where strength, wear and tear resistance, and colour are less
important. The most obvious examples are brown paper bags, cement sacks and similar
sorts of wrapping paper.
Cellulose film Cellulose is a long-chain carbohydrate with no cross-linking. The large number of hydroxyl
groups in each molecule results in a lot of hydrogen bonds and a consequent strong
attraction between the chains. Cellulose is not thermoplastic.
Cellophane is an important cellulose-based biofilm. It is a transparent and flexible
film, with good tensile strength and elongation properties. Cellophane is a regenerated
form of cellulose. It is often coated (e.g. with nitrocellulose-wax (NC-W) or polyvinylidene
chloride (PVdC)) to improve the water vapour barrier and make it heat-sealable. NC-
W/cellophane is fully biodegradable, but PVdC cellophane degrades to small PVdC
fragments, which are not biodegradable. Uncoated cellophane is a good barrier against
oxygen, fats, oils and flavours at low relative humidity, but these properties suffer as
relative humidity increases.
As cellulose is not thermoplastic it cannot be extruded. Cellulose films are not edible,
although modification can solve this problem. Cellulose ethers (methyl cellulose (MC),
hydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose (HPC), carboxymethyl
cellulose (CMC)) are edible. These films have moderate strength, are flexible, transparent
and resistant to oils and fats.
HPC is the only edible and biodegradable cellulose-derived polymer that is
thermoplastic and, therefore, extrudable. One disadvantage is its sensitivity to water.
However, coating with solid lipids can be one solution, e.g. bilayer films of MC or HPMC
with stearic acid or palmitic acid have been produced. Cellulose acetate or ethylcellulose
are thermoplastic, too, and can be cast from a non-aqueous solution or extruded. Theyprovide good barriers against oils and fats, but not against water.
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Although cellulose acetate is not a good barrier against water or oxygen, it works wellwith high-moisture products, because it breathes and does not fog up.
Properties of cellulose-based films Films cast from aqueous ethanol solutions of
these cellulose ethers have improved properties. They are resistant to oils and fats and act
as moderate barriers to moisture and oxygen. Other properties are: moderate strength,
flexible, transparent, odour-free and tasteless and water-soluble. MC is the most
hydrophobic of the cellulose ethers, but it is still not a good moisture barrier. However, it
is an excellent barrier to the migration of fats and oils. Cellulose-derived edible polymers
are not capable of being extruded or injection moulded, because they are not
thermoplastic (except for hydroxypropyl cellulose). MC and HPMC both form thermally-induced gel coatings and are used on frozen French fries, onion rings and other fried
foods to decrease oil absorption during cooking.
Paper Paper- and board-based packaging accounts for some 40% by weight of all packaging in
the world. The main strength of paper-based packaging is its flexibility. It is easy to print
on and can be used in conjunction with other materials, such as plastics or similar
coatings, for waterproofing. Unlike plastics, paper-based packaging is made from a
renewable material source and there are already extensive mechanisms in place for the
recycling of these grades.
Paper is used to make three main types of packaging: corrugated, sack kraft and
containerboard. Corrugated board for packaging remains popular due to its relative
strength, low cost and adaptability.
Paper products can be divided by grammage into two categories: paper and board.
Papers consist of one layer and weigh 25300g/m2. Board is manufactured using a
multilayer technique, and weighs between 170 and 600g/m2.
The line between paper and board is not clear cut, because the lightest boards are
lighter than the heaviest papers. More important than weight, it is use that determines
where the line is drawn paper for printing and board for packaging.
The strongest packaging paper is made of kraft paper. Unbleached or bleached kraft
is used for making sacks, bags, liners and wrappers.
Flexible packaging This form of packaging is widely used as a disposable wrapping for food products and
papers drinks that are not already packed. They are also used as a presentational outer covering
for different types of products. Wrapping paper may be supplied coated or uncoated and
in colour. Their main applications are in food and gift-wrapping and to give temporary
protection to other loose retail products.
In the wrapping of food, packaging papers can be used to wrap products such as
newly baked bread and fresh cheeses. The latter application is popular in France. In the
gift-wrapping sector, demand for packaging papers is highly seasonal with noticeablepeaks around Christmas.
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Paper wrappings and bags are popular with retailers and their customers because they areinexpensive, lightweight, adequate in performance and easily disposable. Whether natural
or bleached, rubbed, finished, coated or associated with other materials, paper comes in
various shapes and sizes: brown paper bags for fruit and vegetables, cement sacks,
crystallised or sulphured paper, technical and special papers (yoghurt lids, separators for
metal sheets or coffee sacks).
However, the outlook for the flexible paper packaging market in both the UK and
Europe is one of decline. In 2000, demand for flexible packaging papers in western
Europe was put at363,000 tonnes, down from374,000 tonnes in 1997. In 2001, demand
fell to360,060 tonnes and demand for flexible packaging papers in western Europe is
forecast to fall further still to345,700 tonnes in 2006. In the UK, a similar long-termdemand trend has existed for most of the 1990s.
Flexible packaging papers are under constant threat from plastic films in a number of
end uses such as baked goods, dried foods, confectionery and soap. This has only been
partially alleviated by some end-use successes and continuing popularity in countries such
as France and Germany. These two countries are the largest markets for flexible packaging
papers and together account for an estimated 40% of total European consumption.
Among the successes for flexible packaging papers are fast food wrap and metallised
paper cigarette bundle wrap. Also, in the packaging of flour and sugar, and traditional
applications such as French soft cheeses, flexible wrapping paper continues to dominate
because these items are not hygroscopic.
Aluminium foil Aluminium foil is available in a number of specially developed aluminium alloys as well as
pure aluminium. Aluminium alloys provide varying degrees of strength and other
characteristics that result in extremely varied uses for foil in flexible packaging. Coils of
aluminium strip with thicknesses of 24mm are cold rolled to thicknesses of between
0.045 and 0.4mm to make semi-rigid dishes and containers for the bakery, butchery,
ready meals, deli, hotel catering and pet food markets.
Plain (unlaminated) foil in thicknesses of around 0.0120.018mm is used in large
quantities for household and catering wrap. Aluminium foil is used in over 97% of UK
households. Much of the thinnest foil around0.007-0.009mm is used laminated with
one or more layers of other materials, such as paper, board and plastics, coated, printed
and embossed to produce packs for foodstuff, drinks, pharmaceutical, tobacco, cosmetics,
horticultural, medical and industrial products.
Extremely thin aluminium sheet offers many packaged goods the best barrier
properties. These include: preventing the loss of valuable aromas; and protecting contents
against light, oxygen, moisture and contamination. Foil guarantees quality and the best
protection against deterioration for sensitive and valuable products.
Aluminium foil just 0.0063mm thick, commonly used in packaging laminates, can
keep sensitive foodstuffs fresh for months without refrigeration.The main packaging applications include: aluminium-lined beverage cartons, sachets,
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preserved foods in pouches and cartons, yoghurt-pot lids and wrappers for butter orcheese, confectionery wraps, pharmaceutical blister and strip packs, foil containers for
baked products, ready meals and pet foods, etc.
Aluminium foil has high thermal conductivity. This reduces the energy required for
sealing and sterilisation. Aluminium foil is malleable and can be deadfolded this is
beneficial when deep-drawing containers, embossing surface designs or wrapping, e.g.
hollow shapes. Another advantage is, of course, that it is recyclable.
Recent Pira studies indicate that the flexible packaging market for aluminium foil has
been more than matching the growth in other materials. Lifestyle trends and innovative
packaging will help to underpin its healthy future. New trends include the use of alufoil in
healthcare packaging and an increase in the use of foil pouches.In the case of other flexible packaging applications, aluminium foil is benefiting from
its ability to protect dairy foods from UV light. Studies show that light not only reduces
the vitamin content of milk but also acts as a catalyst for the oxidation of unsaturated
fatty acids. Clear glass transmits 92% of light; a foil-lined carton transmits 0%.
There is now growing evidence on Europes supermarket shelves of the increasing use
of aluminium foil-lined stand-up pouches and cartons for new long-life food products.
The retortable pouch is now well-established in modern packaging. It uses a
minimum of materials yet is extremely robust. Its thin walls, coupled with its slim shape,
allow the heat in a retort to penetrate and cool quickly. This gives full control over
temperature and processing time, which is necessary to ensure the maximum quality
of the food contents. The broad pack format also offers excellent opportunities for
colourful display.
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Raw materials and production
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Flexible materials 2
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One of the fastest growing segments in the packaging industry is flexible packaging ingeneral and its flexible plastic component in particular. Technological developments in
flexible plastics have allowed the material to steal market share from paper-based
packaging, such as the rigid corrugated box. Flexible plastics are still very much a work
in progress with new developments in chemistry, films, forming and filling emerging all
the time.
New plastic products and new applications for existing products are constantly
coming to market. While most flexibles are produced from commodity polymers, an
increasing number are now being made with sophisticated multilayer structures and
combinations of substrates.
Packaging in western Europe is big business, accounting for more than 1% of regionalGDP. Plastic is the second most important packaging material in Europe, after paper and
board; it is also the most dynamic, with growth based on historic trends estimated at
some 45% a year. The flexible component accounts for some30% of all plastic
packaging sales in western Europe. Under its broadest definition, this includes sales of
pallet shrink and stretch wrap, collation shrink, carrier bags, refuse and agricultural sacks,
dry cleaning and laundry, industrial liners, heavy-duty sacks, bubble film, mail film and
converted flexible packaging mainly used for consumer products such as food and
groceries, DIY and healthcare.
According to Pira estimates, by 2002 plastic films accounted for some 78% of the
flexible packaging materials used in western Europe.
The main flexible packaging materials are: polyethylene (PE), biaxially oriented
polypropylene (BOPP), cast polypropylene (PP), polyamide (PA), polyvinyl chloride (PVC),
polyethylene terephthalate (PET), cellulose, aluminium foils and papers.
Among the substrates used for flexible packaging in western Europe, PE has by far
the largest share. However, its rate of growth is slow compared with faster growing rivals
such as BOPP, cast PP, PA and biaxially oriented PET (BOPET). Pira estimates that the
rate of growth for PE is 1.5% a year to 2006, less than the forecast growth for GDP in
western Europe.
Over the past several years, linear polyethylenes (LLDPE and HDPE) and PP have
shown the highest growth rates and are expected to continue to grow at rates well above
GDP. According to some estimates, global demand for PP will grow by 68% a year
through 2006. These growth rates are 1.5 to 2.5 times that of world GDP over the same
period. Per capita consumption of PP resins worldwide is expected to grow throughout the
next several years.
Worldwide PP capacity is forecast to increase by more than 7 million metric tons
between 2001 and 2006. North America, western Europe and Asia account for the
majority of new capacity. As with PE, the new PP facilities being constructed are 1.5 to
two times larger than they were less than five years ago, and more versatile.
Total European production of propylene in 2002 amounted to around 14 milliontonnes. At the end of 2000, there were 50 steam crackers operating in western Europe
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and nine in central/eastern Europe, with annual ethylene capacities of 21.6 and 2.2million tonnes respectively, giving a total 23.8 million tonnes.
In 2002, western European PE consumption was estimated at 975,000 tonnes, little
changed from the 920,000 tonnes consumed in 1998. The rate of growth for BOPP,
estimated at some3.25%, has seen consumption in the region rise from 476,000 tonnes
in 1998 to an estimated 570,000 tonnes in 2002; it is forecast to rise to 650,000 tonnes
in 2006.
Reasons for this growth rate are numerous but BOPP, one of the flexible packaging
success stories of the 1990s, has seen demand grow as it has replaced cellulose films, PVC
films, aluminium foils and paper. So comprehensive was its advance as a material
substitute in flexible packaging applications that western European demand grew from335,000 tonnes to 475,500 tonnes between 1993 and 1998.
If demand for BOPP reaches the 650,000 tonnes expected in 2006 this will represent
a near doubling of demand in ten years. The greatest demand comes from coextruded
films, with around two-thirds of BOPP packaging film demand. Growth in coextruded film
growth continues to outperform coated BOPP, largely because it is a cheaper and more
efficient process.
Around 10% of BOPP packaging films are metallised; two-thirds of this is used for
savoury snacks packaging with most of the balance used for confectionery, baked goods
and dried foods. Growth in demand for metallised BOPP is set to outperform BOPP
packaging films as a whole at around 9% a year.
BOPPs properties, which have allowed it to grow organically and as a material
substitute for paper, aluminium foil, PVC and other films, are:
Good moisture-barrier properties;
A poor gas barrier without coating;
Low tear resistance;
Can be sealed to itself when coated or coextruded;
Excellent clarity and stiffness;
Perception of being an environmentally friendly material easy to recycle or
incinerate;
Handles well through machinery;
Cheaper per square metre than other films (although more expensive than PE) due to
its lower density and higher yield.
BOPPs main drawback is its relatively high melting point of 160165C and very narrow
thermal melt threshold for sealing purposes, which necessitates constant monitoring of
the packaging line.
The principal demand sectors for BOPP film include:
Snack foods
Confectionery
Baked products Biscuits
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Carton overwrap Tea and coffee
Polyolefins Polyolefins is the generic term used to describe a family of polymers derived from a
particular group of base chemicals known as olefins. The polyolefins family includes PP
and PE. Polyolefins are made by joining together small molecules (monomers) to form
long chains (polymers) with thousands of individual links.
The base monomers, propylene and ethylene, are gases at room temperature, but
when linked together they become long chains of molecules called polymers. As polymers,
they form tough, flexible plastic materials with a large variety of uses.
The monomers are linked together by polymerisation. This requires high temperaturesand, in many cases, high pressure and the use of a catalyst system. Catalysts are generally
a mixture of titanium and aluminium compounds. Without these remarkable substances
the production of polyolefins would not be feasible; the polyolefin success story is in large
part due to increasingly powerful and sophisticated catalyst systems.
Although ethylene had been successfully polymerised in the 1930s, it was not until
the early 1950s that progress was made with polymerising propylene. One of the problems
was that the propylene molecule, being slightly more complex than ethylene, could attach
itself to the growing chain in one of three different ways. Unless all the links are facing in
the same direction, however, the PP formed is an oily liquid. The secret to creating an
isotactic form of PP lies in the catalyst used to drive the reaction: the right catalyst lines
up the molecules to ensure they are facing the right way when they join the chain.
After lengthy experiments with different catalysing agents, the breakthrough came on
11 March 1954. Over the following decades the catalysts and process systems used to
produce PP and PE have been progressively refined. As development continued, catalysts
became more powerful and sophisticated, the PP and PE produced became purer and
more versatile and the production process became simpler and more efficient.
Polyolefins are the worlds fastest-growing polymer family. Modern polyolefins cost
less to produce and process than many of the plastics and materials they replace. In
addition, continuous improvement in strength and durability enables manufacturers to use
less of them. Todays polyolefins come in many varieties. They range from tough, rigid
materials for outdoor furniture and car parts to soft, flexible fibres. Some have high heat
resistance for microwave food containers, while others melt easily and can be used in
heat-sealable food packaging. Some are as clear as glass, others completely opaque.
Through research and development, the variety of materials available is increasing
and polyolefins are steadily replacing other polymers and traditional materials in many
applications. Films made of polyolefins are widely used for packaging food and other
goods. They are made by squeezing molten material through a narrow slit. The film
produced in this way may later be stretched to make it stronger. Films may be used for
coating other materials such as paper to make them glossy or waterproof.As well as being highly transparent and glossy, the materials used for making films
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must also be strong enough to resist tearing or splitting during manufacture. When usedto wrap food they must be acceptable under food contact rules. The worlds most widely
used food packaging material is PP film because it provides strong, attractive protection
for a wide variety of foodstuffs. The latest advances in polyolefins are currently giving rise
to interesting new developments in film technology.
FIGURE 2.1 Monomers
Ethylene monomer:
Propylene monomer:
Vinyl chloride monomer:
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H
H
H
H
C C
H
H
CHH
H
C C
H
H
CII
H
C C
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Styrene monomer:
Types of flexible Flexible plastics packaging benefits from the wide range of polymers available, each with
plastics its own combination of physical and chemical properties. These polymers can be used
alone or in combination with other polymers or with other materials such as aluminium or
cardboard. The following is a broad breakdown of how these materials may be used:
Mono-material shopping bags, candy wraps/twistwraps;
Polymer multilayers detergent refill packs, PP big bags with PE liners, blood/
fluids bags;
Combined with other materials metallised film, PE liner in steel drum, bag-in-box
packages.
Polyethylene PE is produced in several forms. HDPE is used for both rigid and flexible
packaging applications. In flexible applications, it is used in the manufacture of blown
and cast films for many food items. LDPE is used in the manufacture of industrial liners,
vapour barriers, shrink and stretch-wrap films, while LLDPE is used in the manufacture of
stretch/cling film, grocery bags and heavy duty shipping sacks.
Polypropylene PP is used in the manufacture of medical packaging, moisture-proof
wrapping and fat-resistant films.
PET This is used for both rigid and flexible packaging. In flexible packaging, PET is
commonly used in the manufacture of pouches for boil-in-bag foods and pouches for
sterilisable medical applications.
PVC Also used for both rigid and flexible packaging applications, in recent years PVC has
had to contend with concerns from the environmental lobby. It is still used, however, inthe manufacture of films for butter, meat, fish, poultry and fresh produce. It is also used
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H
C
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H
H
C C
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to make bags for blood and intravenous solutions and in the manufacture of blisterpacksfor medical devices, pharmaceutical products, hardware and toys.
Polycarbonate (PC) PC films are used for pre-baked bread, biscuits, confectionery, meat
and processed cheese.
Ethylene vinyl alcohol (EVAL) Also referred to as EVOH, this material is used in
multilayered flexible packaging to provide an oxygen barrier.
Other materials Polyethylene naphthalate (PEN)This polyester is similar to PET but more temperature
resistant; it is expected to have a bright future when prices fall as production increases.PEN offers a good balance of properties and manageability that provide many
advantages in packaging applications that require: transparency, gas and water vapour-
barrier performance, high-thermal performance, UV screening, high strength and
dimensional stability.
PENs mechanical properties allow downgauging to thinner films. It can also be
blended with less expensive PET to produce a copolymer that is cheaper than PEN but
which retains PENs superior barrier properties.
Polymers in combination Each packaging polymer has its own specific physical and
chemical properties. One way of achieving optimum cost performance and a precise
packaging function is to use a combination of different polymers. One example may be
the manufacture of a toothpaste tube. This is commonly made out of several polymer
layers, often with intermediate tie layers that bind them together. It must also contain
a barrier material.
Recycling also plays a role. In the packaging of detergents many containers are now
made with three layers of the same polymer, such as HDPE, but with the middle layer
made from post-consumer waste. The outer layers of virgin polymer achieve the desired
surface characteristics and protect the contents from contamination.
Polymers with other materials Plastics are sometimes used in combination with other
materials. One example is the breakfast cereal box where a plastic bag is often used
inside a cardboard carton. Even here, to ensure maximum product freshness, the bag
often has a multilayer construction of different polymers. In the case of pharmaceuticals,
many products are packaged using plastic blisters and aluminium foil.
Conversion of An important property of plastics, which makes them suitable for a wide range of low-cost
flexible plastics packaging applications, is their ability to be converted into a wide range of shapes.
Extrusion The first of several shaping processes for plastics is extrusion. Granules are fedfrom a hopper into the barrel of the extruder where they are melted by heat and the
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mechanical action of the screw. The action of the screw forces the molten plastic throughan orifice called a die, which determines the type of product produced. A die design will
create thin flexible plastic films of the type used for food packaging.
Cast film Packaging film can be produced by extrusion followed by cooling on chill rolls.
The temperature of the chill rolls is controlled in order to cool the film progressively. The
gauge of the film is determined by the dimensions of the die and the rates of extrusion
and take-off. When more rapid cooling is needed, the film is sometimes passed through a
water bath. During the production process cast film can be oriented by stretching. This
strengthens the film and can also improve its resistance to gas permeation.
Orientation can be in one direction (uniaxial orientation) or both (biaxial orientation).Film used to make bags is usually uniaxially oriented because most of the forces it
experiences only occur in one direction.
Calendering An alternative method of producing film is to pass the extrudate through
a calender. Unlike the chill rolls used in the cast film process, pressure is exerted in the
sheet between the rolls of the calender. This enables special surface characteristics, either
smooth or textured, to be applied. Sheet thickness can be controlled by the size of the gap
between the rolls. The temperature of the rolls is controlled so that the film remains hot
during the calendering process. Cooling is carried out at a later stage. Tight control over
the film or sheet thickness can be achieved through the calendering process, which is
often used in the manufacture of PVC.
Blown film A popular way of making film is by a process of extrusion through an
annular die to produce a tube. Air is blown into the tube causing it to form a bubble.
When the bubble has cooled sufficiently it is collapsed between rollers and wound on to
a drum. The blowing action stretches the film radially; often the film is also stretched
vertically by the winding process. The result is a very strong biaxially-oriented film.
Multilayer films, often used for food packaging, can be produced using this process.
Polyethylene PE in its various forms LDPE, LLDPE and HDPE is by far the most common film
material used in converted primary flexible packaging. Its principal properties are:
Cheap relative to other films
Good puncture resistance
Good low-temperature performance
Good sealing properties and the ability to be sealed to itself without coating
Good moisture-barrier properties
Poor gas-barrier properties.
PE mono web film uses include: frozen foods, confectionery, processed meat packs,
coextruded inner bags for cereal packs, bread bags, rice, collation shrink wraps, andoverwrapping for a number of products such as kitchen rolls and toilet paper.
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Historically growth in western Europe is around 1.5% a year. Based on this consumption in2006 will be just over 1 million tonnes, up from around 975,000 tonnes in 2002.
Some 5.1 million tonnes of PE films were consumed in western Europe in 2001, about
80% of this by packaging applications; under its broadest definition, this included stretch
and shrink films, carrier bags, refuse sacks, household bags and heavy duty sacks.
PE film usage in converted flexible packaging applications is estimated to be around
975,000 tonnes in 2002, having grown from around 920,000 in 1998. Future growth in
demand is unlikely to be high, which reflects both the maturity of the market and the
encroachment of other films such as BOPP in a number of applications.
Cast PP The growth in consumption of CPP is expected to rise in western Europe in the yearsahead. Annual growth, according to historic trends, will be just under 5%. If this
continues, demand for CPP will be around 180,000 tonnes by 2006.
Among the properties for which CPP film is valued are:
High impact strength
Good moisture-barrier properties
Poor gas barrier without coating
Ability to be sealed to itself
Excellent clarity and stiffness
Easy to recycle or incinerate.
Its end use applications include:
Textile packaging
Transparent windows in food cartons
Bread and bakery products, with significant demand in Germany and Scandinavia
Confectionery twistwrap, especially in Germany
Medical and pharmaceutical applications in multilayer constructions
Flower wrap
Laminations with other materials.
PA In 2002, some 100,000 tonnes of nylon resins were consumed in western Europe in
flexible packaging applications. In the late 1990s, demand was growing at some 4000
tonnes a year. Based on historic trends, consumption will rise to close to 120,000
tonnes by 2006.
Nylon films are used in a number of packaging applications. Their gas-barrier
properties mean that they are often used in multilayer structures and frequently in
combination with polyolefins for barrier pouches and lidding films. Among the end-use
applications are: PA/PE laminations reverse printed for conversion into pouches for
processed meats and frozen fish; and coextrusions for processed meats, cheese and
medical packaging.
More than half of western European demand for nylon resins for flexible packagingapplications is for cast nylon films (CPA). The remainder is for biaxially-oriented nylon film
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(BOPA), for which demand is growing at some 6% a year compared with 5% for CPA,barrier films and other coextrusions.
PAs characteristics include:
It is the most expensive of the main films used in flexible packaging;
Excellent puncture resistance giving high-tensile strength and the ability to remain
flexible at low temperatures;
Good gas- and odour-barrier properties;
Moderate to good moisture-barrier properties;
It is not sealable to itself except with coextruded versions.
PET Some 60,000 tonnes of PET was used in western Europe for flexible packaging in2002.Based on historical growth rates of more than 7% a year, this could rise to around 75,000
tonnes by 2006.
Polyester film is highly regarded for its advanced technical properties, which are
exploited in a wide range of food applications. The most important are in the packaging
of fresh meat, fish and poultry, processed meats, snack foods, baked goods, dried foods
and convenience foods.
Polyester film, which is expensive relative to PE and BOPP, has the following
properties:
Superior puncture and stretch resistance
Very strong
Good thermal stability
High clarity
Available in thin gauges down to 12 microns
Moderately good gas and moisture barrier
Excellent carrier web for coatings and vacuum metallising
Cannot be sealed to itself except when coextruded or coated with a heat-seal layer.
The main trends associated with the different types of PET film include:
Growth in the use of corona-treated film because suppliers now sell it at the same
price as plain film;
PVdC-coated PET films are being replaced by silicon oxide- and EVOH-coextruded
PET films;
It is anticipated that coated PET films, such as acrylic-coated films, will become the
standard commodity film in place of corona-treated and plain PET film.
The PET packaging film market in western Europe is growing at around 4.5% a year based
on historic trends, and should continue to do so over the next few years.
The principal reasons for the continued growth in demand for PET films reflect those
for growth in the flexible packaging market as a whole. These include: the growth of
packaged foods in western Europe, particularly prepackaged fresh meat, snack foods and
convenience foods, such as ready-made meals; and the growing use of prepackaged foodsin southern European countries like Spain.
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In addition, polyester film-based flexible packaging is replacing other packaging formatsand materials, including rigid packaging, and aluminium foils are being replaced by
metallised polyester film in laminate applications.
PVC Very little growth is expected for this sector in the years ahead. Demand for PVC films for
flexible packaging applications in western Europe was around 53,000 tonnes in 2002 and
is expected to rise to 56,000 tonnes by 2006. By far the most important applications are
for machine overwrapping of fresh meat, fish, poultry, cheese and carton overwrap. Some
PVC film is also used for confectionery twistwrap, particularly in France, Spain and other
parts of southern Europe.
In western Europe as a whole, consumption of PVC films is growing at barely 1% ayear. This is largely because the use of PVC packaging film has come under attack from
the environmental lobby, but also because of downgauging.
Environmental concerns have been the main reason for the decline in consumption of
PVC films in the northern European markets of Germany, Scandinavia and the Netherlands
since the early to mid-1990s. By the late 1990s, demand in the UK, which had previously
held up because of effective lobbying by the industry and the higher cost of alternatives,
also began to decline.
This was in part a result of the multiples moving from in-store PVC overwrapped EPS
trays for red meat to centrally-packed MAP systems. In other areas, such as overwrap for
fresh poultry, demand has been resilient, although new thermoformed packaging formats
are challenging PVC overwrap.
Alternatives to PVC film for cling overwrap include newly-developed high-clarity
thermoplastic elastomers and pastomers based on olefin and styrenic monomers.
Cellulose Western European demand for cellulose film for f lexible packaging applications in 2002
is estimated at around 15,000 tonnes, 2000 tonnes less than in 1997. Although the steep
declines of the late 1990s are levelling off, further decline is expected in the years ahead;
demand in 2003 is forecast at 13,400 tonnes.
Cellulose has been the victim of material substitution by BOPP and other films in
high-volume standard packaging applications. One of the drawbacks of cellulose film is its
relatively high cost compared with BOPP, a result of the expensive chemical production
process involved in its manufacture.
Nonetheless, despite this adverse price differential, cellulose remains popular among
many small food processors that operate older or slower equipment, as it is a forgiving
material with a wide thermal-sealing tolerance and good machineability.
It is expected to continue to fulfil a niche role in flexible packaging. New products,
such as pearlised colour effects, are being developed to broaden its appeal.
Barrier packaging The presence of a layer of ethylene vinyl alcohol (EVOH) in, for example, high-barriermaterials pouches dramatically lowers the oxygen transfer rate (OTR). Their lower OTR makes these
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Ethylene vinyl alcohol pouches a good choice for products, such as sliced luncheon meats and cheeses. EVOH isfar and away the most widely used barrier material. However, it is sensitive to moisture.
As moisture increases, EVOHs crystalline structure plasticises and creates pathways for
gas molecules. Its effectiveness as an oxygen barrier then decreases accordingly.
Polyacrylonitrile films Polyacrylonitrile (PAN) films are fabricated using both spin- and solvent-casting
techniques, and pyrolyzed to produce carbon films 20050,000A thick. These films have
higher electrical conductivity than carbon films produced from most other precursors at
similar temperatures. Just over 25 tonnes a year of PAN is used as barrier material in
packaging worldwide and growth is estimated at just under 4% a year. Larger amounts
are used in composites for non-packaging applications in, for example, the automotive,construction and aerospace sectors.
PCTFE The best current moisture-barrier film is polychlorotrifluoroethylene (PCTFE), which has a
water vapour transmission rate (WVTR) of less than 0.03mg/day for most structures and
is the only true high-moisture-barrier film resin. The WVTR is usually determined at 100F
and90% relative humidity. High-barrier films have WVTR values of 0.03mg/day or lower.
A commercial example from the pharmaceutical sector is Aclar, Honeywell International,
Inc.s registered trade name for its high-barrier films made from PCTFE.
PVOH, metallised film PVOH is used as a coating to give packaging film high-barrier properties. One commercial
example is Hifipac S.A.s cast PP, acrylic/PVOH-coated transparent film for packaging
dried fruits and nuts. This package is said to have an eco-friendly structure and a good
combination of materials for high barrier, transparency and gloss.
Polyethylene Low-density PE film is a poor gas barrier, but resistance to gas transmission increases with
density. PE is frequently laminated with other, often more expensive films to combine its
good moisture-barrier and heat-sealing properties with other desirable properties.
Polypropylene OPP film is usually stronger and more resistant to the transmission of water vapour and
gas than PP. This orientated film has slightly lower water vapour and gas transmission
rates than a medium-density PE. It is resistant to fats, acids and alkalis.
Polyvinylidene chloride: Manufactured by Dow, Saran F-Resins are available for solvent coating of cellophane and
example Saran other film substrates. Polyvinylidene chloride (PVdC) is inert when in contact with food
and can be used either as a film or as a coating on other films. It is often linked
chemically with PVC to produce a range of copolymers. PVdC provides an excellent barrier
to water vapour and oxygen and is therefore useful in preventing fat in fish from going
rancid. It is resistant to fats and oils and to many organic solvents. PVdC and its
copolymers are most frequently used as thin coatings on other, cheaper films.
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High-barrier Western European demand for high-barrier substrate materials, such as EVOH and PVdCsubstrate materials for flexible packaging applications, was put at around 95,000 tonnes in 2002. The growth
in demand is high and, in 2006, is forecast to reach 140,000 tonnes, a near doubling in
demand compared with 2000 when it was 79,000 tonnes.
The development and exploitation of a growing range of sophisticated barrier films in
the form of laminations, coextrusions and coated films, including metallised materials, has
been central to the success of flexible packaging in the past two to three decades.
In the years ahead new developments are expected which will lead to greatly
extended shelf lives for a wide range of food products. The use of smart films, which can
modify their barrier properties in response to external changes in temperature and
humidity, is also expected to grow.High-barrier substrates are often loosely defined to include a wide range of
laminated, coextruded, coated and foil substrates that offer a better oxygen- and
moisture-transmission barrier than monolayer and coextruded films.
EVOH EVOH is a polymer with superior oxygen-barrier properties in dry conditions, but not when
exposed to water and steam during thermal processing or retorting. However, EVOH can
be partially protected from moisture when it is coextruded as an internal layer in
multilayer plastic retortable structures that include high temperature-resistant polymers
such as PP. Because of their excellent gas-barrier properties EVOH resins offer outstanding
protection against odour and flavour permeation and are finding applications in the
active packaging area.
EVOHs growing importance as a food packaging polymer is a result of its excellent
processability, high thermal stability and recyclability. Indeed, some studies forecast that
demand for EVOH will grow at 10.6% a year, as it has proven its value when used in
coextrusion structures.
The biggest EVOH producer in Europe, EVAL Europe N.V. (Antwerp, Belgium), a
subsidiary of Kuraray Co. Ltd, is currently doubling its production capacity from 12,000
tonnes to 24,000 tonnes a year. The new facility, which is costing an estimated 8.5
billion (68 million), is scheduled for completion in the third quarter of 2003.
This is considered necessary in order to meet growing worldwide demand for EVAL
EVOH resins. EVAL is the registered brand name while EVOH copolymer resin is the
chemical name of the product.
EVAL Europe is the only producer of EVOH copolymer resins in Europe and is a world
leader in EVAL EVOH production and development.
Kuraray has continued to expand its food packaging business since commercial
production of EVOH resins began in 1972.
Principal EVAL applications include food packaging (coextruded flexible films, sheets,
bottles and tubes), automotive components (fuel tanks and lines), and medical and
pharmaceutical packaging.Worldwide growth in demand is over 10% a year, with growth in the food and
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pharmaceutical sectors accounting for a large proportion of this. The company has plantsin Okayama, Japan (annual capacity 10,000 tonnes), Pasadena, Texas (EVAL Company of
America, 23,000 tonnes) and Belgium (annual capacity 12,000 tonnes). The combined
capacity of the Kuraray Group stands at 45,000 tonnes, which the company estimates will
not meet growing demand and explains the reason for its expansion plan.
Kuraray designates EVAL as one of its core businesses in its five-year New Medium-
Term Business Plan (G-21). The plan focuses on the strengthening and expansion of its
global business. EVAL is also regarded as a key product for expanding demand in eco-
friendly areas, one of the four strategic areas defined in the companys expansion plan. In
line with this goal, it aims to ensure that the new production facilities feature process
improvements that take environmental preservation needs into consideration.After expanding in Europe, Kuraray is considering a similar increase at its EVAL
Company of America site in Texas, US. The plan is to increase capacity by 12,000 to
24,000 tonnes a year to35,000 to 47,000 tonnes a year.
EVAL produces a number of EVOH resins for a range of applications:
EVAL L has the lowest ethylene content of any EVOH and is suitable as an ultra high-
barrier grade for several applications.
EVAL F offers superior barrier performance and is widely used for automotive, bottle,
film, tube and pipe applications.
EVAL T has been specially developed to obtain good layer distribution in thermo-
forming and has become the industry standard for multilayer sheet applications
EVAL J offers thermoforming results said to be superior to those of EVAL T, and can
be used for unusually deep-draw or sensitive sheet-based applications.
EVAL H has a balance between high-barrier properties and long-term run stability. It
is especially suitable for blown film. There are special U versions that allow improved
processing and longer running times even on less sophisticated machines.
EVAL Es higher ethylene content allows for greater flexibility and easier processing.
There are different versions for cast and blown film as well as for pipe.
EVAL G has the highest ethylene content, making it the best candidate for stretch-
and shrink-film applications.
EVALs main customers are in the food and non-food packaging sectors. Foods packaged
include: meat (fresh meat, dry meat), fruits, cheese, ham, pasta, pizza, sausage, salami,
yoghurt, mayonnaise, ketchup, bread, coffee, tea, milk, beer, juice, snacks and pet food.
Unspecified growth is forecast for all sectors to 2007.
PVdC PVdC was developed in the 1950s and therefore has a long history of use as a high-barrier
material. In the early 1990s, it was one of four options for customers that required barrier
properties in their packaging; the others were nylon, EVOH and metallised films.
Nowadays, PVdC is commonly used in multilayer constructions with other materials
to provide enhanced barrier properties.Copolymers made from PVdC are resistant to a number of foreign materials. They
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provide a barrier against gases, odours, water, water vapour, oils and fats, and are alsoused in the coating of various materials (paper, plastic film, thin aluminium foil) which is
primarily used in the packaging of food and pharmaceuticals.
Widely used to over-wrap foods, Dows Saran wrap is a commonly used trade name
for PVdC. Saran monolayer films come in a variety of grades, with various cling, shrink,
barrier properties and colours. Each grade can be supplied in a range of widths, lengths,
and thicknesses, and several grades are available in a rainbow of colours.
Saran films can be used in a number of ways:
To wrap items such as cheese, bakery goods, marzipan, processed meats and other
food items.
In more sophisticated packaging applications they can be heat-tacked and sealedusing radio frequency sealing equipment on form/fill/seal (FFS) machines.
In tubular form for the production of low-shrink bags or for sausage production.
As part of a laminated packaging structure or in water vapour-retardant structures in
the building and construction industry.
Saran PVdC has a unique molecular composition, which gives the film high-barrier
properties, including cost-effective and dependable oxygen-barrier performance for the
packaging of meats and fish. It also has an improved moisture-barrier performance that
keeps crackers, cereal and shelf-stable baked goods fresh and crisp.
Dow claims that its PVdC has superior barrier characteristics to EVOH as it delivers
performance at real-world temperatures and humidities, not the zero relative humidity
environs where EVOH is typically tested.
Some polymer The flexible packaging industry is poised to introduce and capitalise on new technologies.
developments It will also benefit from new specialty PP copolymers and terpolymers, including
functionalised resin systems that make it possible to produce both engineered and
elastomeric PP grades. Many of these new technologies result from improved
metallocene/single-site and traditional ZieglerNatta (ZN) catalysts.
While large producers such as Basell, BP, ExxonMobil and Dow are leading the way,
the PP industry as a whole retains latent and commercially underdeveloped product
technology with cost/performance advantages. Access to these technologies will play a
role in improving producers long-term profitability.
Although PP offers a cost/performance advantage over other materials, it is still
applications driven. PP product applications development, diversification and substitution
for existing plastics and materials have been and will continue to be a lifeline for PP
producers. In addition to the obvious economic benefits derived from consolidation,
improved access to technology will broaden the range of higher value products offered
by larger players.
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Metallocene Metallocene-based catalyst technology is revolutionising the polyolefin industry,polymers particularly the markets for PE and PP. Some have called metallocenes the single most
important development in catalyst technology since the discovery of ZieglerNatta
catalysts. This optimism is reflected in the R&D efforts of the major polyolefin producers
which, according to some estimates, spend about 75% of their total polyolefin research
effort on metallocenes, with the remaining 25% spent on the incremental improvement of
conventional technologies.
Metallocene polyolefins are projected to penetrate many polymer markets. First, the
higher priced specialty markets, followed by the high-volume and commodity markets.
New markets are also expected to be created with the development of new classes of
polymer that were not possible with conventional ZieglerNatta technologies.Conventional LDPE accounts for 55% of the polymers processed by European film
extruders. But an AMI study shows that linear low density and metallocene polyethylenes
(mPE) are growing steadily; they accounted for 28% of films in 2000.
The primary reason for the increased interest in this new technology is that metallocenesoffer some significant process advantages and produce polymers with very favourable
Introduction to Flexible PackagingFlexible materials
FIGURE 2.2 The evolution of metallocene olefin polymerisation catalysts
Source: Pira International Ltd
Ti
Me
Me
+ B(C6F5)g
Me
Me
Me
MeB(C6F5)g
+ Support +
+ Support + B(C6F5)g
NSi
R
Ti
NSi
R
a
aa
a
a
a
+ MAO
+ MAO + Support
+ MAO cocatalyst
Constrained geometry
catalyst
Homogeneous
Ti
NSi
R
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properties. Metallocenes are a relatively old class of organometallic complexes, with
ferrocene the first to be discovered in 1951. At the time, the term metallocene was used to
describe a complex with a metal sandwiched between two eta5-cyclopentadienyl (Cp)
ligands. Since the discovery of ferrocene, a large number of metallocenes have been
prepared and the term has evolved to include a wide variety of organometallic structures
including those with substituted Cp rings, those with bent sandwich structures, and even
the half-sandwich or mono-Cp complexes.
The sandwich structures have been known for decades, but were not considered
practical as catalysts. Then, in the mid-1980s, German professors Walter Kaminsky of the
University of Hamburg and Hans H. Brintzinger of the University of Konstanz showed that
metallocenes had industrial potential. Since then research has focused on modifying,
improving and extending this catalyst family.
Metallocene-based polymers tend to have the following features, for example:
increased impact strength and toughness; better melt characteristics, because of the
control over molecular structure; and improved clarity in films. Most early applications
have been in specialty markets where value-added and higher-priced polymers can
compete. As the technology develops and catalyst costs decrease, metallocene-based
polymers are expected to compete in the broader plastics market.
Exxon Chemical and Dow Plastics are leading the plastics industry into the
metallocene era. Competition comes from other plastics producers which are polishing
technologies to increase productivity, reduce costs and create intellectual property estates.
Exxon first produced metallocene-based polymers with its Exxpol catalysts in 1991. It
now markets about30 grades of ethylene-butene and ethylene-hexene copolymers under
the Exact trade name. In April 2002, ExxonMobil Chemical Company and Mitsui
Engineering and Shipbuilding, Inc. began expanding their metallocene ethylene elastomer
production facility in Baton Rouge, Louisiana. The facilities are expected to be operational
by the third quarter of 2003 and will add capacity of more than 90,000 tonnes a year.
The capacity expansion will include EPDM (ethylene propylene diene rubber),plastomers and novel polymers, all produced using Exxpol metallocene technology. Exxon
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Differences between ZieglerNatta catalysts:
ZieglerNatta The presence of several metal sites gives less control over polymer branching
catalysts and Monomer insertion occurs at the end of the growing chain
metallocenes Changing metal centre is ineffective
Metallocenes:
Single metal site allows for more control over branching and molecular weight
distribution;
Insertion of monomers between metal and growing chain of polymer;
Versatility with countless variations (i.e. bridging atoms, overcrowding).
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believes that having both conventional ZieglerNatta and metallocene catalysttechnology gives it the opportunity to supply its customers with a broad range of current
and new products.
Dow uses its Insite technology to make ethylene-octene copolymers, which the
company launched in 1993. Copolymers with up to 20% (by weight) octene are sold as
Affinity plastomers and compete with specialty polymers in packaging, medical devices
and other applications. Dow says its catalysts permit the uniform introduction of
comonomers and long-chain branches that improve processability in otherwise essentially
linear polymers.
With an octene content of more than 20%, the copolymers fall into the elastomers
category and have been sold under the name Engage since early 1994.In Freeport, Texas, Dow converted 113,500 tonnes a year of solution process capacity,
which previously produced its Dowlex PE, to produce metallocene-based polymers. In
2001, as a result of a merger with Union Carbide Corporation, Dow agreed to divest to BP
Chemicals Limited its interest in technology developed in the course of their joint
development programme between 1995 and 1999; Dow also divested a research
programme with BP and Chevron Phillips Chemical Company L.P. between 1998 and 2001.
Each of these programmes was directed at the development of metallocene catalysts
for gas-phase PE. Dow also agreed to divest to BP its patents and other assets solely
related to gas-phase PE processes using metallocene catalysts, including a license granted
to Chevron Phillips.
Flexible packaging The new breed of metallocene catalysts is ushering in a new age of custom-made
implications commodity plastics. Metallocene technology is finally reaching critical mass, accounting
for more than 1 million tonnes of the plastics sold in 2001.
Few materials can match the versatility and economy of modern PE and PP. These are
by far the best-selling plastics. Whether in bottles, plastic films or medical products, the
two polymers collectively known as polyolefins have proved themselves to be
workhorse materials since the 1960s.
For all that, polyolefins still leave much to be desired. The average plastic is a mixture
of polymer chains and structures whose properties are difficult to predict and demand
many compromises in their use. Designers and engineers typically factor in these
uncertainties by making their products thicker, larger and less intricate, or by using special
additives, at great expense, to change the properties.
Metallocenes promise to fix all that and deliver new properties. The catalysts act
rather like tiny molecular robots to let chemists control the alignment and structure of
polymer chains. By some measures, films made of metallocene-based PEs can have two
to three times the tensile strength, five times the impact strength and twice the tear
strength of traditional polymers. This means users can make much thinner films and parts,
saving on everything from plastic resin to transport costs.
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Fruit and vegetables The ability to produce lower-density polymers creates softer, more elastic films that canbreathe oxygen in packaging for fruit and vegetables. Traditional food packaging is
perforated with tiny holes to allow the food to breath and be stored for longer, all at a
cost in strength and overall expense. Metallocene-based packaging can be tailored to
breathe at a specific rate to match the respiration of the food it is storing and is stronger.
Notably, too, the narrow distribution of polymer and the low residual catalyst content in
metallocene-based PE means that the plastics give off little flavour or scent to the food
they are storing.
Development Although the technology was well developed by the end of the 1980s and commercialised
drawbacks early in the 1990s, the market for metallocene plastics has remained largely one forprocessing, cost, specialty and high-value applications. More important, perhaps, is the fact that licensees
patent concerns of the technology have been slow to come forward.
However, the market has increased and the use of metallocene polymers has grown at
2530% in recent years. In total, the market amounted to about 1.1 million tonnes of PE
and nearly 115,000 tonnes of PP in 2001. But these amounts are small compared with the
large volumes of traditional polyolefins sold. All told, metallocenes amount to little more
than 1% of the total market. What is more, the bulk of that growth has come from
cannibalising the existing PE and additives markets. Still, metallocene producers see
countless new applications ahead that will boost demand, such as replacing glass,
specialty polyesters and even PVC, the other major plastic.
Processing concerns A number of hurdles must be cleared first, however. In the first
place, metallocenes are fraught with processing problems that make it hard to use them
in existing equipment. The resulting narrow polymer distribution makes extrusion and
processing more complicated. Clear metallocene-made films tend to crackle on the
surface, making it hard to produce a smooth film. And all sorts of modifications to
plastics machinery are required to account for their varied properties.
Metallocene producers say they have taken great strides towards overcoming such
problems. Ironically, one of the solutions has been to add specific copolymers into the mix
to give the effect of ZieglerNatta distributions, but in a more controlled way. Other
efforts seek to tweak the processes to make switching from ZieglerNatta to metallocene
as easy as swapping one for the other.
Patent concerns With all the billions spent on research and development, some3000
individual patents have been issued for various processes and designs. Most of these have
been locked up by Dow, which developed its Insite metallocenes for solution-based PE
production, and by Exxon, which commercialised metallocenes for a gas-phase PE process.
As chemical companies sought to consolidate control over intellectual property, they
set off a series of lawsuits that has mired the industry in courtrooms for close on adecade. Dow, Exxon, Mobil, Phillips and others filed more than ten big patent lawsuits in
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the 1990s, and a number are still in court today. With millions being spent on litigation,plasti