Mark J. Kirwan Paper and Paperboard Packaging Technology

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PAPER-BASED FLEXIBLE PACKAGING

107

See Lockhart & Paine (1996) for pharmaceutical and healthcare packaging.

3.5 Packaging machinery used with paper-based flexible packaging

Flexible packaging is usually associated with form, fill, seal machinery. Vertical

form, fill, seal machines (Fig. 3.14) are used to pack free-flowing food materials

and liquids. Packs made in this way are either flat or incorporate gussets and block

(flat) bottoms. Flat-bottom bags can be made in compact ‘brick’ designs with a

wide range of top closures/reclosures (Figs 3.15 and 3.16).

Table 3.1 Typical paper-based medical packaging structures

Note: lb in this context refers to the basis weight in pounds per 3000 square feet or a ream of 500

sheets of 24 in. × 36 in.

Structure Sterilisation by Application (sealing)

50 g/m

Kraft/30 g/m

LDPE

31 lb Kraft/18 lb LDPE

Compatible with EtO and

radiation

Backing web to peelable

materials on four-side seal

machinery

108 g/m

Kraft/13 g/m

overall

heat seal

70 lb Kraft/8 lb overall heat seal,

white, air-knife coating

Suitable for EtO (sufficient

porosity) and radiation

Lidding for thermoform, fill and

seal, die-cut lids pouches

44 g/m

Kraft/29 g/m

LDPE/4 g/m

overall heat seal

27 lb Kraft/17.8 lb LDPE/2.5 lb

heat seal

Radiation Peelable for four-side sealing

with uncoated paper and also

lidding for thermoformed base

web

60 g/m

Kraft/6 g/m

overall

grid heat seal

37 lb Kraft/3.7 lb overall grid heat seal

EtO and radiation Lidding for thermoformed base

web

60 g/m

Kraft/11 g/m

overall grid

heat seal

37 lb Kraft/6.8 lb overall grid heat seal

EtO and radiation Lidding for thermoformed base

web

100 g/m

Kraft/11 g/m

overall

grid heat seal

61 lb Kraft/6.8 lb overall grid

heat seal

EtO and radiation Lidding for thermoformed base

web

40 g/m

Kraft/12 g/m

LDPE/8 mu

Al foil/14 g/m

Surlyn

25 lb Kraft/7 lb LDPE/32 ga Al foil/

8.6 lb Surlyn

Radiation Suitable for four-side sealing

with equivalent peelable

lacquer- coated material

40 g/m

Kraft/3 g/m

overall

synthetic cold seal

25 lb Kraft/1.8 lb overall synthetic

cold seal

EtO and radiation Seals to itself

60 g/m

Direct-Seal paper (Kraft)

37 lb Direct-Seal paper (Kraft)

EtO and radiation Seals to a partner web with sealing

layer is non-discharge treated PE

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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

Product

Forming shoulder

Tube

Heat sealing

and cutting

Figure 3.14 Vertical form, fill, seal machine.

Pillow

Trapezoid

bag

Trapezoid with

clip

Pillow with

profiled seal

Hole punch Carry handle

Chain bag

Labyrinth

seal

Figure 3.15 Range of typical pillow-type packs produced on vertical form, fill, seal machines, including

chain or strip packs. (Reproduced, with permission, from Rovema Verpackungmaschinen GmbH.)

PAPER-BASED FLEXIBLE PACKAGING

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Another type of machine is filled vertically but the pack is formed horizontally.

It can be formed with a base gusset (Figs 3.17 and 3.18). This type of pack is suit-

able for a powder, granular or liquid product. Single items can be packed and cut

off in multiples forming strip packs – the heat seals separating adjoining individual

packs can be perforated so that the individual sachets can be used progressively.

Flat bottom

Cardboard insert Single side gusset Gusseted

Asymmetric Carry handle Stabilo seal

Figure 3.16 Range of typical gusseted/block bottom bags produced on vertical form, fill, seal machines.

(Reproduced, with permission, from Rovema Verpackungmaschinen GmbH.)

Index feed web

and pouch forming

Flow of work

Index conveyor

carrying individual pouches

Heat seal

web material

Cut web into

individual pouches

Fill

customers

product

Fill

customers

product

Top seal

Figure 3.17 Horizontal pouch/sachet form, fill, seal machine for dry mixes (soups, sauces etc.), pastes and

liquid products.

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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

The flow wrap-type machine both forms and fills the pack in a horizontal plane.

It is used to pack single solid items, such as confectionery bars or multiple products

already collated in trays, which may be made of paperboard or plastic (Figs 3.19

and 3.20).

In-line thermoforming is primarily thought of in the context of plastic

packaging because the base web is made up of one or more plastics. The lidding

and in-mould labelling of such packaging is, however, frequently achieved with

paper-based materials. This was discussed under medical packaging though

there are many food-based applications, chiefly yoghurts and cream-based

desserts (Fig. 3.21).

There are machines which form bags around mandrels, sealing being made

with adhesives, so that they have a rectangular cross section and a block bottom.

(This type of machine can also wrap a carton around the paper on the same

mandrel to form a lined carton.) Roll-wrap machines pack rows of items, for example

biscuits and sugar confectionery. Individual confectionery units may be wrapped

in waxed paper for moisture protection and to prevent them sticking together.

These may be twist wraps, dead folded or plain waxed liners overwrapped

with a folded printed paper.

Figure 3.18 Typical horizontally formed pouches/sachets with 3-side sealing, 4-side sealing and base

gusset providing a ‘stand-up’ feature. (Reproduced, with permission, from Rovema Verpackungmaschinen

GmbH.)

Product

Folding box

Heater blocks

Rotary

crimpers

Finished

pack

Propelling rollers

Figure 3.19 Horizontal form, fill, seal type machine.

PAPER-BASED FLEXIBLE PACKAGING

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Overwrapping square or rectangular shaped cartons with paper coated with

PE or wax with neatly folded heat-sealed end flaps is also used, for example

overwrapping of chocolate boxes, teabag cartons and a grouped overwrap of

10 cartons each containing 20 cigarettes (Figs 3.22 and 3.23). Another form of

overwrap is the waxed paper bread wrap with ends folded progressively and heat

sealed.

3.6 Paper-based cap liners (wads) and diaphragms

Paper-based flexible materials are used inside plastic caps and closures for rigid

plastic and glass jars. They are referred to as discs or innerseals.

Figure 3.20 Typical horizontal form, fill, seal pack. (Reproduced, with permission, from Rose Forgrove

(MOLINS PLC).)

Base material

Filling

Product

Lidding material

Heat sealing/cutting

Thermoforming

Figure 3.21 In-line thermoforming and lidding.

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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

3.6.1 Pulpboard disc

The simplest type of cap liner is a pulpboard disc made from mechanical pulp

fitted inside a plastic cap. The cap liner or wad has to be compressible and inert

with respect to the contents of the container, usually a food product. This liner

could be faced with aluminium foil or PE where the nature of the contents requires

separation from direct contact with the pulpboard.

3.6.2 Induction sealed disc

The disc comprises pulpboard/wax/aluminium foil/heat-seal coating or lacquer

(Fig. 3.24). The cap with the disc in place is applied to the container and secured.

Lateral sealer

Sleeving plates

Underfold

Tuckers

Carriage unit

Outfeed

End sealers

Folding deck

Film control rollers

Film reel

Tear tape

Guillotine

Elevator

Grippers

Front feed

conveyor

Left-

right-hand

side feed

conveyor

Transfer unit

Figure 3.22 Overwrapping machine. (Reproduced, with permission, from Mardon Edwards Ltd.)

Figure 3.23 Overwrapping envelope end-fold folding sequence. (Reproduced, with permission, from

Mardon Edwards Ltd.)

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It then passes under an induction heating coil. This heats the aluminium foil which

causes the wax to melt and become absorbed in the pulpboard. It also activates the

heat-seal coating and seals the aluminium foil to the perimeter of the opening of

the container. When the consumer removes the cap the adhesion between the pulp-

board and the aluminium foil breaks down leaving the foil attached to the con-

tainer. This seal therefore provides product protection and tamper evidence.

Where subsequent contact between the contents and the pulpboard is undesirable,

the pulpboard is permanently bonded to the aluminium foil. (A simpler version

dispenses with the wax and replaces the pulpboard with paper.)

3.7 Tea and coffee packaging

There are many different types of tea and coffee packaging (Fig. 3.25). In the

context of paper-based flexible packaging, the main interest is in tea and coffee

Closure

Pulpboard

Wax

bond

Foil

Heat seal

coating

Heat seal

coating

Paper or foam

Foil

Figure 3.24 Pulpboard discs for induction-sealed cap liners. (Reproduced, with permission, from The

Institute of Packaging.)

Figure 3.25 A selection of heat sealed tea and coffee bags. (Reproduced, with permission, from IMA,

Industria Machine Automatiche.)

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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY

bags and the printed, heat-sealed envelopes, and tags which are associated with

them in some of the forms of marketing product presentation.

The bags themselves are made from very lightweight porous tissue. The tissue

is either heat sealable or non-heat sealable. A typical heat sealable tissue is 17g/m

and contains a heat sealable thermoplastic fibre such as PP in addition to its long

fibred structure. Bags may be flat, square, four-side perimeter sealed. Two webs

are used at high packing speeds. Alternatively, bags may be round or pyramidal

in shape. Non-heat sealable tissue is used to make a bag which is folded and stapled

giving a larger surface area for infusion and using a lighter weight tissue, typically

12 g/m

. All these bags are closely associated with the machinery which forms,

fills and seals the bags – both types may have strings and tags (Fig. 3.26).

It is possible to link such machines with enveloping machines which can

comprise paper, or paper laminated or coated with moisture and gas barrier

properties. Tea and coffee bag packing machines can include, or be linked to,

cartonning or bagging machines.

3.8 Sealing tapes

Sealing tapes have much in common with labels but they can be considered a flexible

packaging product as paper reels are subjected to a reel-to-reel conversion process

and sometimes they are also printed.

Sealing tapes are narrow-width reels comprising a substrate and a sealing

medium which can be dispensed and used to close and seal corrugated fibreboard

cases, fibre drums, rigid boxes and folding cartons. Sealing tapes are also used by

the manufacturers to make the side seam join on corrugated fibreboard cases and

tape the corners of rigid boxes, thereby erecting or making-up corner-stayed boxes.

A traditional and commonly used substrate is hard-sized kraft paper, both

unbleached (brown) and bleached (white). Where higher strength is required the

kraft is reinforced with glass fibre, and up to four progressively stronger specifications

are typically available from some suppliers. Reel widths start at 24 mm, though

Figure 3.26 Tea and coffee bag with tag, string and envelope. (Reproduced, with permission, from

IMA, Industria Machine Automatiche.)

PAPER-BASED FLEXIBLE PACKAGING

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50-mm width tape would be a typical width to seal the flaps of an average sized

corrugated fibreboard case.

In the case of gummed tape, adhesion is achieved by coating the kraft paper

with a modified starch adhesive; animal glue has largely been superseded. The

adhesive is then dried and the reels are slit to size. In subsequent use the adhesive

is automatically, and evenly, reactivated by water in a tape dispenser. Tape dispensers

which can cut pre-set lengths for specific taping specifications are available.

The advantages of gummed paper tape are that it is permanent and provides

evidence of tampering, it can be applied to a dusty pack surface without loss of

adhesion, is not affected by extremes of heat and cold and does not deteriorate

with time. Pressure-sensitive tapes, on the other hand, are used on all types of

packaging from paper and paperboard to metal, glass and plastic containers.

Pressure-sensitive adhesive can be applied to several types of substrate, including

moisture-resistant kraft paper which has been coated on the other side with silicone

to facilitate dispensing from the reel.

Heat-fix tapes are based on kraft paper where the adhesive is applied as a

thermoplastic emulsion, dried, subsequently reactivated by heat when applied to

the sealing surface with pressure. Sealing tapes used are plain, preprinted or printed at

the point of application.

References

AMCOR, 2003, Per-Stefan Gersbro, AMCOR Flexibles Europe, personal communication to M.J. Kirwan,

visit www.packaging-technology.com.

Dow, 2005, Dow Chemical at http://www.dow.com/svr/prod/.

FOPT, 1996, Walter Soroka, The Fundamentals of Packaging Technology, revised UK edition, edited

by Anne Emblem & Henry Emblem, pp. 30–31.

FPA, 2003, Flexible Packaging Association (US), Facts and Figures, 01 May at Website

www.flexpack.org.

Inman, B., 2004, Private Communication to M.J. Kirwan from Bill Inman, past Technical Manager,

Henry Cooke Ltd.

James, R., 1999, Packaging for Sterile Medical Devices, Seminar, April 1999 (Association of British

Healthcare Industries).

Merritt, J., 2002, Medical Device Technology, January/February.

Merritt, J., 2003, Medical Device Technology, March.

Paine, F.A., 2000, Prof. Frank A. Paine and Eric Corner, Market Motivators – The Special Worlds of

Packaging and Marketing, CIM publishing, pp. 161–164.

Paine, F.A. and Lockhart, H., 1996, Packaging of Pharmaceuticals and Healthcare Products, Blackie

Academic and Professional, pp. 50–89, 120.

Websites

AMCOR Flexibles at www.amcor.com.

Flexible packaging at www.interflexgroup.com.

Medical papers at www.billerud.com.

Papers for flexibles at www.smithanderson.com.

www.medicalpackaging.dupont.com.

4 Paper labels

Michael Fairley

4.1 Introduction

The use of labels in a format that would be recognised today can be traced back to

the early 1700s. At that time, labels were used mainly to identify products such as

bales of cloth and medicines. Labelling of products for sale using printed labels

had not evolved to any significant extent at that time, largely because few of the

population could read or write and because there was no trade of mass produced and

packaged goods.

All that began to change with the advent of education and mass literacy programmes

in the 1800s, together with the evolution of the mass production of food and drink

in bottles and cans – the need to put descriptive and brand information on products,

and to produce labels in volume quantities, now became a necessity.

By the later part of the nineteenth century, the introduction of the papermaking

machine and the invention of lithography provided the means to produce econom-

ically long runs of the same quality (label) papers and to print them, in sheeted

form, in colour. It was the advent of cost-effective colourful labels produced in this

way that enabled manufacturers to take advantage of the opportunity to individually

package and label their products themselves, rather than having them individually

weighed and wrapped by the provision merchant. Product labelling, as we know it,

had arrived.

Initially labels were printed onto plain paper and cut to a rectangular size by

guillotine – even scissors or punches, if a special shape was required – before being

applied with a wet-glue or gum. Early methods of labelling used gums and adhesives

which were brushed on to the label and then the label applied by hand. These first

slow labelling methods eventually evolved into full-blown applicator machines and

systems which applied a wet-glue to the back of each label and then applied the

label to the bottle or can. Wet-glue paper labelling in a form that would be recognised

today became a reality. Pre-gummed paper labels for application to paper and

paperboard packaging was a later evolution, helping to speed up address labelling

for the dispatch of transit packaging.

With these developments, the product manufacturer was able to use the label as

a means of contact with the customer so as to promote a product or brand, add

information regarding contents or usage, provide the name and address – even claim

all kinds of (unproven) health, digestive, beauty or other benefits of the product.

Indeed, it was the widespread growth of such claims that led governments to start

introducing legislation to protect the consumer from misleading claims.

The dominance of the wet-glue applied label for product labelling of glass bottles

and cans, and gummed paper labels for addressing and shipping labelling of

Paper and Paperboard Packaging Technology

Edited by Mark J. Kirwan