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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

E [email protected]

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

[email protected]

Customer services manager

Denise Davidson

[email protected]

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

Page iii Copyright Pira International Ltd 2003

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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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Page v Copyright Pira International Ltd 2003

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

Page vi Copyright Pira International Ltd 2003


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Raw materials and production

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Page 1 Copyright Pira International Ltd 2003

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

Introduction to Flexible Packaging




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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



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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Flexible materials 2


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

Introduction to Flexible PackagingFlexible materials



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2


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:



H

H

H

H

C C

H

H

CHH

H

C C

H

H

CII

H

C C


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2


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


H

H

C

6

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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2


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


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



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

pira international ltd-introduction to flexible packaging-ismithers rapra publishing...

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