Mark J. Kirwan Paper and Paperboard Packaging Technology
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MULTIWALL PAPER SACKS
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paper mills and machinery manufacturers, this work has enabled the industry to
maintain an edge against competition from new materials and systems. Subse-
quent contribution to the overall reduction of packaging and packaging waste has
largely not been recognised by governmental interests and also by those involved
in the environmental lobby.
Recovered sacks can be recycled. The high quality long fibre they contain
should be suitable to paper makers, provided economical recovery conditions pre-
vail. The paper sack industry is willing and keen to participate in any viable
scheme or schemes of recovery.
In Europe, intensive discussions are underway on implications of the EU
Packaging and Packaging Waste Directive, involving legislators, affected author-
ities and trade associations. There are indications that a lack of awareness exists
about the paper sack industry and the unique position it has within the overall
packaging industry.
It is being suggested that buyers and specifiers should revise their specifica-
tions and maximise the content of secondary fibre. A levy on virgin fibre has been
proposed. In the opinion of the paper-sack industry, these views indicate a lack of
understanding that some virgin fibre in any mix of pulp is, and has to remain, an
essential component in the paper making chain.
To summarise:
•
paper sacks are made from renewable raw materials
•
paper sacks are lightweight materials
•
the inherent energy of paper sacks can be recycled in energy from waste
systems
•
paper sacks are biodegradable.
And, finally, the paper-sack manufacturing industry accepts its responsibility to
contribute to the reduction of the overall volume of packaging.
Useful contacts
European Federation of Multiwall Paper Sack Manufacturers
42, rue galilée
F – 75116 Paris, France
Tel: (33) (0) 1 47 23 75 58
Fax: (33) (0) 47 23 67 53
info@eurosac.org.
Paper Shipping Sack Manufacturers’ Association, Inc.
505, White Plains Road, Suite 206
Tarrytown, NY 10591
Tel: 914/631-0909
Fax: 914/631-0333.
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Environmental and Technical Association for the Paper-Sack Industry (ETAPS)
64, High Street, Kirkintilloch, Glasgow G66 1PR
Tel: +44 (0)141 777 7272
Fax: +44 (0)141 777 7747
Email: NPC@natpack.org.uk
Websites
Environmental and Technical Association for the Paper Sack Industry at: www.natpack.org.uk
European Federation of Multiwall Paper Sack Manufacturers at: www.eurosac.org
Paper Shipping Sack Manufacturers’ Association, Inc. at: www.pssma.com
9 Rigid boxes
Michael Jukes
9.1 Overview
A rigid box is a box set-up ready for use without further fixing when received from
the box manufacturer (BS 1986). The origins of the rigid box and its use go back
centuries but its appeal today is largely based upon perceived quality and its ability
to handle weighty contents – often of high value – and to afford physical protection.
With the dominant position of cartons and corrugated cases within the paper
packaging industry, it may appear that rigid box use is in steep decline. However,
for numerous boxmakers, both large and small, the market niches that rigid boxes
and their derivatives serve is actually widening. While it is a long time since the
rigid box was the packaging container of choice for the myriad of products which
are now not even in cartons but in cellophane wrappers, for example, there are
probably two major factors which underpin the appeal of the rigid box – quality
and perceived luxury.
The range of the rigid box is not simply comprised of lift-off-lid (LOL) boxes.
We should consider the wide range of products made by boxmakers and their
box-making machinery in order to get a full appreciation of the market appeal
of the rigid box. All products have their strengths and weaknesses/limitations
but, in a world where packaging waste is an international environmental issue, the
‘greenness’ of the rigid box, together with its versatility, answers many of our
present concerns.
Strengths
•
structural strength and ability to provide protection for its contents
•
perceived luxury by the ability to combine materials such as board, fabric,
metal, plastics, etc.
•
wide range of styles, sizes and covering materials and accessories, for
example hinges, etc.
•
design freedom – combination of rigid jackets, boxes, slipcases
•
wider range of print and surface finishes compared with carton board
•
compatibility with on-counter display of retail products
•
ability to make ‘small quantity’ production runs
•
second and alternative use when empty
•
typically >80% of material content is recyclable and recycled.
Weaknesses and limitations
•
large ‘empty size’ compared to the fold flat carton type offerings
•
relative higher cost compared with cartons
Paper and Paperboard Packaging Technology
Edited by Mark J. Kirwan
Copyright © 2005 by Blackwell Publishing Ltd
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•
unsuitability for automated processing in volume applications
•
volume restrictions – production rates limited to around 2500 per hour.
9.2 Rigid box styles (design freedom)
A defining characteristic of the rigid box is the freedom it allows with respect to
shape, materials, use of accessories and overall presentation. Rigid boxes may be
large or small, square, rectangular, round or elliptical in shape. The simplest rigid
box forms are based upon the basic lift-off-lid (LOL) box as shown in Figure 9.1.
The shell and slide, book style and flip top, as indicated in Figure 9.2, show
other distinctive closure designs. The shell and slide has been expanded into a case
with drawers to hold, for example, assortments of chocolates or surgical instruments.
Combining trays (box bases) with different lid constructions results in hinged
and shouldered (jewel) boxes as shown in Figure 9.3.
Turning trays on their sides results in slip cases with a variety of shapes and
design features as shown in Figure 9.4.
Rigid board jacket with pockets and plastic fitments are used to pack digital
video discs (DVDs) (Fig. 9.5).
The addition of accessories in the form of ribbons, bows, clasps and hinges can
provide ‘special’ appeal as shown in Figure 9.6. Plastic and rigid board fitments
are also used.
Tray Lift off lid Shouldered box with lift off lid
Figure 9.1 Basic lift-off-lid (LOL) boxes.
Shell and slide Bookstyle Fliptop
Figure 9.2 Examples of distinctive box styles.
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4-way hinged lid Hinged shouldered box and lid 3-way hinged lid
Figure 9.3 Hinged and shouldered boxes.
Standard slipcase Slantcase Folio slipcase
Figure 9.4 Slip cases.
Pocket
Ri
g
id jacket (1 DVD and pocket)
Pocket
8-PP Roll-fold DVD jacket with pocket (3 DVDs) 2-DVD clamshell
Figure 9.5 Rigid jacket with pockets for DVD.
Metal hinges
Metal clasp
Ribbon stay
Figure 9.6 Incorporation of accessories in box design.
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9.3 Markets for rigid boxes
The UK market sectors that are the largest users of rigid box packaging include:
•
tableware – ceramics, pottery, glassware and cutlery
•
jewellery and watches
•
perfumes and cosmetics
•
music, video and games
•
stationery and office storage
•
luxury drinks
•
publishing
•
chocolate confectionery and gifts
•
boxed greeting cards
•
photographic trade products
•
engineering and DIY hand tools
•
medical equipment.
At current price levels, the UK market, including imports, is in the region of
£80 million. Exports from the UK mostly into near continental markets is low,
probably in the region of <10% of home production. The proportion exported is
low because it is relatively expensive to transport empty rigid, or ‘set-up’ boxes,
over long distances because of the space required. Exported rigid boxes are usually
those with more complex design where there is a high added-value component.
Within many of these sectors, the luxury ‘gifting’ nature of the contents of the
box brings a large seasonal element into play. Typically the run up to Christmas,
which may last four to five months, gives the boxmaker huge challenges as it is
necessary to increase production dramatically. The typical box-making factory is both
machine and labour intensive. Many of the box finishing processes utilise hand
skills, whereas the setting, operating and maintenance of wrapping, laminating and
material preparation machinery demands the highest level of expertise and skill.
In value terms, the use of one-off special boxes probably exceeds that of standard,
repeated products. With short delivery lead-times (10 days would be usual in the
music sector), the rigid boxmaker generally works directly with the client through-
out the design stage, i.e. the use of sales agents is rare. Clearly the use of Computer
Aided Design (CAD), communication through broadband lines, the digitisation of
print and other ‘modern’ processes and systems are key tools in the boxmaker’s
range of competencies.
9.4 Materials
9.4.1 Board and paper
The main raw materials for paper and board are cellulose fibres, water and energy.
The cellulose fibres mostly come from softwoods, but esparto grass and cotton fibres
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are also used for the finest papers. Boards are principally made from recycled
fibres to give maximum humidity-related stability. Board thicknesses are typically
in the range of 1000–2500 microns with weights of 400–1600g/m
2
. In ‘composite
boxes’, where folding box board (FBB) is used in conjunction with recycled chip-
board, lower weights in the range of 270–400g/m
2
are used. As well as boards
made from recycled fibre, solid bleached boards (SBB) and solid unbleached
(brown) boards (SUB) are also used; they may be lined or unlined depending on
their role in the box construction.
9.4.2 Adhesives
The rigid-box industry usually affixes printed paper to recycled board and generally,
depending on the paper, uses glues of both gelatine and polyvinyl acetate (PVA)
varieties for finishing. In all cases, both the paper and the board absorb moisture to
differing degrees and the ‘wet expansion’ of each material is a key consideration,
not only in material selection but also in design and construction. The absolute
level of humidity in each adjacent material is not the issue, but rather the differential
between each material.
Gelatine glues are almost always preferred but their inability to adhere to
laminated paper surfaces is where the PVA type comes into play. Adhesion may
be equal but gelatine provides a cleaner surface not only to the box but also to
the production machinery. Precise glue selection is also dependant on the box
construction with open times being an important consideration. Clearly, glue
temperature and the dispersion of the solid adhesive are features which the
boxmaker must take into account.
9.4.3 Print
Typically rigid boxmakers are not printers; they buy print in, often from local
printers, who are familiar with printing on flat sheets. This is quite different from
the carton-making industry that generally specialises in printing and then adds
extra value by cutting, creasing and gluing to the final carton shape.
Standard sheet–fed printing presses are used with the majority of paper sizes
in the B2 (520 mm × 720 mm) range. With the largest production volumes,
often associated with the music industry, B1 (720 mm × 520 mm) size sheets are
also used. Both ‘standard’ finishes and UV printing techniques are employed,
all driven by the application, with print cost also being a major driving force in
the print-finish selection.
Other embellishments are then added in the box-finishing processes, for example
foil blocking, embossing, debossing and selective lamination or UV varnishing
(where the free areas allow for subsequent gluing).
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9.5 Design principles
The most obvious need for any form of packaging, including the rigid box, is the
need to offer protection for its contents. Depending on the market use, probably a
close second is the need to present, in marketing terms, the packaged product to its
best advantage. This is sometimes achieved by making the product visible whilst
in the box, especially where display at the point of purchase is important, but more
usually it is achieved by the use of arresting graphics and print techniques. Other
display techniques might include window patching and the use of transparent
plastic lids.
Two examples, at opposite ends of the spectrum, might be packaging for the
industrial use of acetate films (OHP slides) and the packaging of luxury cosmetics
or chocolates. In both cases, the contents may have significant mass, both need
protection prior to use or consumption, but their presentation is critical in the eyes
of the customer. A simple lift off lid box with good print may suffice for the
A4-sized box of film but a luxury appearance as, for example, may be provided
by a round, oval or heart-shaped box is required for the beauty preparation or
assortment of Belgian chocolates.
Boxmaking through the use of machinery (as opposed to hand-making tech-
niques) imposes design limitations. The first is that boxes start as flat sheets of
board and paper, and subsequent operations to form the box generally require right
angles, i.e. 90° bends. They are usually rectilinear in shape although some polygonal
shapes can be partially made on machines, for example hexagonal, etc.
From the examples shown earlier in this chapter, more elaboration may be
achieved by the combining together of trays and lids, with or without platforms to
hold the contents in position. The platforms can have complicated shapes and
contours which are achieved by using vacuum formings, or expanded polystyrene,
tailored to hold the contents securely. Transit testing, including drop testing, can
be onerous on rigid boxes so each element of the design has to be carefully
analysed to ensure structural rigidity and provide protection.
Rigid box construction uses a variety of glues and base materials, varying from
recycled board through to covering papers, fabrics, etc., which must be ‘stuck’
together. The widely differing material/moisture expansion issues have to be
borne in mind. Not only can glue/adhesive viscosity have a significant effect on
the overall box dimensional sizing, but also the climatic conditions within the
box-making factory can affect the wet expansion of paper, etc. This in turn can, in
its simplest form, affect the clearances and tolerances of the box and lid. The rigid
box is not, and cannot be considered, a precision product and tolerances of 0.5mm
are not unusual.
The main characteristic of the rigid box is its appearance. It is the variety of
covering materials, including foils, papers, flock or fabric linings, leather – in fact
any material that can be stuck to cardboard and take and hold its shape after the
adhesive is dry – and a wide array of printed effects that give the rigid box its
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unique appeal. Lids may be flanged, domed or padded. Box corners can be metal
edged. Component parts can be hinged together using paper, fabric, metal or plastic;
fastened using many techniques; decorated with bows, ribbons, handles, etc. All
these attributes can combine to make the finished pack suitable for gracing the
most prestigious point-of-sale display, and frequently providing a second use
(often in the home) after the contents are consumed or used.
Boxmakers, like carton producers, generally provide their customers and their
design teams templates that show where the graphics are to appear on the sheet of
print. These are essential as they show the relationship between those visible
faces, flaps, turn-ins, etc. and the parts of the box that are not visible after con-
struction. The addition of printed platforms, sleeves, drawers, etc. all add to the
print complexity but all must be considered during the design stage.
9.6 Material preparation
Rigid boxes typically start as flat sheets that are cut to a predetermined shape before
the box assembly process. ‘Preparation’ machinery and equipment can be as simple
as scissors, continuing through a range of machinery up to computer-controlled
guillotines and continuous cutting machines utilising a stamping-type process.
In the latter case, cutting dies are typically made from steel rule and plywood.
They are often very complicated, including the use of make-readies, and not only
prepare the board for box assembly but also make the scrap/unwanted board easy
to handle and recycle. There are also simple platen dies with different heights of
rule depending on whether a cutting or scoring action is required. (Scoring in this
context means a knife cut in the surface, which penetrates about 50% of the way
through the board.)
Additional equipment is used to cut large boards into manageable sizes for sub-
sequent cutting operations and the forming of grooves and creases on rotary
equipment. The boxmaker is always trying to optimise material usage, i.e. minimise
the scrap cut to waste. This may be by the simple expedient of cutting boards in
half or, more usually, by specifying specific board sheet sizes which the mill then
produces to order.
Covering papers use similar processes but as they are generally printed, the
boxmaker often performs embossing, debossing and foil-blocking operations, all
of which may be vital ingredients of the finished box’s design appeal.
The most simple, covered lift-off-lid box has four main components, each with
its own profile, comprising box card, lid card, box cover and lid cover. Typically
the box and the lid cards will be cut together using a ‘one set-on cutting die’. Simple
cutters for such a construction are relatively inexpensive at around £100 each. This
makes short runs affordable for an extremely wide range of applications.
Modern boxmakers make extensive use of CAD systems for samples and limited
production runs which are often cut on computer-driven plotter tables. The
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component parts are then hand-assembled. This obviously eliminates the need to
buy unique cutters for each box type, size, etc.
Whilst small tooling, jigs and fixtures are generally produced locally, box
wrapping, gluing, spotting and material preparation machinery is available
internationally. Special purpose machinery, i.e. custom designed and built, also
provides equipment manufacturers with unique challenges!
9.7 Construction
At its most simple level, prepared paper is coated with a thin film of adhesive and
applied to the board, with the paper itself wrapped around the corner flaps to
secure them. The next level of complexity is to first ‘stay-up’ the corners of the
board (the box or lid sides) using a heat-activated tape, appropriately called stay
tape, before the covering paper is applied.
Adhesive application may be by hand, simply by passing the paper over a
glue-covered roller, and the paper then being wrapped around the box: this is
suitable for samples, very limited production runs or complex packs/components
which cannot be made by machine. For volume runs, the staying-up of the box is
carried out automatically on a machine. This is then conveyed under a wrapping
head to which the glued-out paper is presented, and through a complex series of
rollers and brushes, the paper wrap is pressed to the back and sides, both on the
outer surface and a turn-in on the inside.
Ideally, two wrapping lines are placed side by side, one producing the box and
the other the lid, with the two parts being put together (lidded-up) by hand or by
machine. Where a book-style box is required, these box-wrapping lines can be
linked to laminating lines (adhering paper sheets to flat boards, grooved or multi-
pieced) to produce a jacket which can then be fixed to the box base. Wrapping
lines are complex and one modern line combined with a staying-up machine costs
in the region of £250000.
A typical high-volume production line is synchronised to perform box staying,
gluing, spotting and then cover-wrapping. A typical machine layout producing
both box and lid is shown in plan elevation in Figure 9.7.
The addition of platforms, both cardboard and vacuum formed, often requires
long conveyorised production lines and throughput levels of 1500–2500 per hour.
The boxmaker is often also called upon to pack the customer’s contents/product.
Box making factories are capital-intensive with the best being air-conditioned or,
at the very least, humidity controlled. Cleanliness and overall pest control are as
necessary for rigid boxes as for any other paper based packaging.
Also the wide variety of box styles inevitably also means that boxmakers are
employers of proportionately more semi-skilled employees than many other manu-
facturing industries. Multi-skilling and a flexible working schedule in manufacture is
essential because of the seasonal variability of the sales of many luxury, gifted, products.