Mark J. Kirwan Paper and Paperboard Packaging Technology
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COMPOSITE CANS
177
6.2.2.3 Linear draw
Multiple plies are wound around a stationary mandrel in the same direction of the
mandrel, Figure 6.4.
6.2.2.4 Single wrap
In this manufacturing process, composite cans are made one at a time. An already-
sized, pre-printed, unglued blank is formed around a mandrel. Once heated, the
can is positioned to receive the bottom-end closure which is heat sealed and
Figure 6.2 Construction of sidewalls of composite containers: (a) convolute construction and
(b) spirally wound construction. (Reproduced, with permission, from the Institute of Packaging.)
Festoons
Skivers
Body glue pots
Can flow
Mandrels
(winding and cutting)
Scrap ring
separator and
upender
Cutter
Label pot
Liner stand
Liner seal
Winder
Figure 6.3 Basic can technology. Source: Sonoco.
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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY
clamped to the body. The top is then heated and curled. The single wrap can is
available as straight wall or tapered to nest, or stack, one inside another, Figure 6.5.
6.3 Historical background
The composite can has a long history that dates back more than 100 years when
packaging was in its infancy and packages were designed to hold and transport
lightweight, easy-to-hold dry products. In its earliest beginnings, it was an
Figure 6.4 Multiple plies wound around a stationary mandrel. Source: Sonoco.
Figure 6.5 Single wrap can. Source: Sonoco.
COMPOSITE CANS
179
offshoot of the paper tube. In the late 1800s, gunpowder, oatmeal and salt were
commonly packaged in paper tubes with crimped ends. At some point, near the
turn of the twentieth century, paper end plugs were added, and composite canisters
were born.
While the early construction of these packages involved nothing more than
unlined paper bodies with crimped paper or metal ends, interest in the composite
can began to grow. Most commonly seen on the pharmacist’s shelf, composite
cans had become the package of choice for items like Epsom salts, sulfur and other
powdered drugs.
Move ahead four or five decades, by the mid-twentieth century, the composite-can
market had experienced rapid expansion. Now, the product was offered with lined
or sprayed can bodies, coupled with the appearance of opening and pouring
features. It was also during this tremendous growth period that manufacturing and
distribution processes were becoming more complex. As production became more
sophisticated, so did the demands placed on manufacturers. New, nationwide dis-
tribution channels led to high-volume, high-speed manufacturing. Package design
began to focus on product protection, ease of handling and user convenience. The
resulting versatility of the composite can made it the package of choice for many
products, such as cleanser, caulks and frozen berries.
It was also during the 1950s, that makers of refrigerated dough began seeking an
inexpensive, convenient package for their products. The composite can was
selected because of its low cost, its ability to hold internal pressure and an opening
feature that did not require the use of a can opener.
Due to the success of the composite can in the dough market, numerous techno-
logical advances were being implemented. These advances included the development
of high-speed winding and cutting equipment, the use of improved liners, like
aluminum foil, for enhanced product protection and special metal-end designs
coupled with better seaming techniques.
Over the next decade, the composite can migrated from specialty markets to
the more high-volume commodity-oriented segments. In the 1960s, the first
commercial shipments of frozen citrus concentrate packaged in composite cans
took place in Florida. Within a few short years, the composite can achieved
package of choice status for 6 and 12 ounces, a position it still maintains in the
twenty-first century.
Paralleling the growth of the concentrated juice market was the petroleum
industry. During the 1960s and through the 1980s, the composite can was the
package of choice for the quart-size container of motor oil. This success, coupled
with some technical experimentation in coffee and solid shortenings, led to further
successes over the next several decades.
In the 1970s, Procter & Gamble made headlines when the company introduced
a brand new product in a brand new package. The Pringles
®
potato crisp, a uniquely
shaped chip, was the first large-scale snack food to be packaged in a hermetically
sealed composite can.
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PAPER AND PAPERBOARD PACKAGING TECHNOLOGY
Major manufacturing companies seized the opportunity to develop the snack-
food business and began, rapidly, establishing production systems and technical
support groups to satisfy the needs of this emerging market. The success of the
nitrogen-flushed, hermetically sealed composite can is well documented, and
created numerous opportunities to use the composite can as a package for
processed meat snacks, powdered infant formula, peanuts and specialty nuts, noodles
and other food items.
6.4 Early applications
Many of the earliest composite can applications, as mentioned in Section 6.3, are
still in use today. Table 6.2 illustrates some of the world’s most famous brands and
the length of time they have been marketed in composite cans.
6.5 Applications today by market segmentation
The packaging industry, valued at more than $400 billion (including packaging
machinery), is one of the world’s largest and most diverse manufacturing sectors.
Nearly 70% of all packaging is found in the food chain, primarily food and drink
(Packworld, 2002).
More than half a decade after its introduction as a commodity package, the
composite can still maintains an admirable position in the marketplace. Ernst &
Young estimates that paper and paperboard remain the most important packaging
material, Figure 6.6, accounting for nearly one third of the market (Packworld,
2002).
To summarize, the major markets for the composite can in the packaging industry
include foods, non-food, beverage and adhesive/sealant products. Further segmentation
of each market is listed in Table 6.3.
Table 6.2 Leading brands packed in composite cans
Segment Brand names Time in market (years)
Snacks Pringles/Planters 30
Refrigerated dough Pillsbury 50
Concentrates Minute Maid, Seneca 50
Adhesives/sealants DAP, DOW, GE ≥30
Cleansers Ajax/Comet 50
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6.6 Designs available
While the earliest composite cans were available with limited design options,
technology has enabled a total redesign of the package. The composite can
allows industrial and consumer companies to create packaging based on product
attributes and customer preferences with different sizes and shapes with numerous
opening-feature options.
Others
Caps and closures
Packaging machinery
Corrugated
010203040
Value ($billion)
50 60 70 80
Rigid/semi-rigid plastic
Films, foils and flexibles
Paperboard
Metal containers
Glass containers
Sacks, bags and labels
Figure 6.6 Global packaging analysis by value. Source: Ernst & Young.
Table 6.3 Products packed in composite cans
Foods Misc. non-food Beverage Adhesives/Sealants
Refrigerated dough Petroleum products Frozen concentrates Caulks
Snacks/nuts/chips Agricultural products Coffee Adhesives
Frozen fruits Household products Powdered milk products Sealants
Dried fruit Pet products Powdered beverages
Salt/spices Dish detergent
Solid/liquid shortening Cleansers
Confectionery
Nutraceutical products
Cookies/crackers
Powdered foods
Dried meats
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6.6.1 Shape
Shaped containers are an ideal and proven way to establish product differentiation
on the cluttered shelves of drug, grocery, specialty and retail stores. The traditionally
round composite canister is now available in unique shapes – rectangular, triangular
and oval. The ability to print high-impact graphics is an added bonus to other can
features like stackability and delivering eye-catching billboarding opportunities.
6.6.2 Size
•
Diameter. In the case of a round can the size is determined by the diameter.
There is a difference between the way this is expressed in the US compared with
Europe.
In the US the dimension used is the diameter of the metal can end which
is applied to the tube and in Europe the dimension used is the internal
diameter of the tube itself.
Popular diameters in the US expressed in inches and sixteenths of an inch are:
202, 211, 300, 401, 502 and 601.
In Europe popular diameters expressed in mm (US measurements in
brackets):
65 (211), 73 (300), 84 (307), 93.7 (313), 99 (401), 155 (603).
(The 73, 84 and 93.7 mm are also produced with other styles of closure,
which are within the tube diameter. The 93.7 mm is used for powdered milk
and drinking chocolate and the 73 and 84 mm are used for gravy powders
and have paper bases.)
•
Height. A wide variety of heights is available.
6.6.3 Consumer preferences
Manufacturers of consumer products are taking consumer preferences into consid-
eration when determining composite can characteristics. For example, many conven-
tional canned goods now offer an easy-open (EZO), closure feature to eliminate the
need for any type of opening device, e.g. can opener, twist key. Certain demographics
are also considered. For example, in the United States, where the population is
aging, many can features are designed to make handling and opening easier.
6.6.4 Clubstore/institutional
With the explosion of clubstore and institutional buying opportunities for the
general public, larger cans and combination packs are becoming more prevalent in
the marketplace. Often multi-packs are bundled together with shrink-wrap packaging
or labeling.
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6.6.5 Other features
Because of the composite can’s versatility, there are numerous ways to enhance
the package based on particular customers’ needs:
•
Twist can. This exciting product is directed toward the tween (8–12) and
younger market. The outer ply of the package is lightly scored, so that the
resulting rings spin about the can body. The can becomes a re-usable toy, and
is a great attention-grabbing device that can often result in impulse purchases.
•
Combination packs. As manufacturers of consumer products continue to
consolidate, more combo-packs are appearing on the shelf. One of the fastest
growing markets is the pet-care industry. It is very common to see cans of
pet treats sold in combination with other pet care products. In this type of
scenario, multiple packaging options are combined for promotions.
•
Pressure-sensitive coupon application. To increase shelf appeal and sales,
many manufacturers apply a coupon directly to the end or body of the composite
can prior to shipment. These immediately redeemable in-store money-off
coupons or recipe ideas often influence consumers’ purchasing decisions.
•
Insert-inside overcap. Similar to the pressure-sensitive coupon application,
an insert is attached to the inside of the overcap, and is not visible to the
consumer prior to opening the product. In many instances, a coupon is
included for cents off on subsequent purchases.
6.6.6 Opening/closing systems
In addition to strength and versatility, the composite canister is also known for its
numerous options for opening and closing systems. Consumers prefer easy-opening
and dispensing features that provide resealability to maximize freshness. Paper,
aluminum, steel, plastic or membrane closures are fitted on cans by single or
double seaming, gluing, pressure inserting or heat sealing.
Closure choice primarily depends on the product to be packaged, as well as the
ease of use, protection needed, dispensing requirements, the opening and re-opening
ability and the necessary hermetic properties. Choices include:
•
glued or heat-sealed paper bottoms and/or lids
•
steel and aluminum bottoms and/or EZO lids with single or double seaming
•
lever system with or without pilfer-proof membrane
•
seamed metal ring with a foil membrane and plastic overcap
•
plastic lids and/or bottom with pour spouts
•
rolled edge with flat membrane and plastic overcap
•
sealed recessed foil membrane with pull-tab and plastic lid
•
glued-in or sealed plastic closure with hinged lid and pilfer-proof membrane
•
paper lid with or without flat membrane.
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6.6.6.1 Top end closures
Top-end closures are often, but not always, differentiated from bottom-end
closures by the presence of an opening feature. Various types of opening features
are available in the market today due to the wide range of products packaged in
composite cans. In today’s economy, consumer preferences dictate the types of
opening features which are most frequently used. Some of these opening features
are also used with shaped and non-round composite cans. Details of various designs
of opening are given below. For their features and benefits, see Table 6.4.
Table 6.4 Features and benefits of various opening ends for composite cans
Source: Sonoco Phoenix.
Steel end options
Type • Full panel
Features • Full panel easy open ring-pull end
• Food and non-food applications
• Double reduced steel available in select diameters
• Safety fold available in select diameters
Benefits • Easy open
• Lithography, embossing available
• Style, design options
• Recloseable with overcap
• Vacuum or nitrogen flush capable
Aluminum end options
Features • Full or partial-pour panel with easy open ring-pull end
Benefits • Easy open
• Folded edge or hot melt bead provides cut protection
• Recloseable with overcap
• Vacuum or nitrogen flush capable
Flexible membrane options
Features • Peelable, flexible multi-layer or foil membrane heat sealed to
a
tinplate ring or tinplate steel ring
• Valve available for pressure applications
• Ring-pull option for some diameters
• Leveling feature
Benefits • Easy open
• Printing, embossing available
• Recloseable with overcap or plastic plug
• Pressure, vacuum or nitrogen flush capable
Plastic end options
Features • Resealable molded plastic overcap
• Available in colors to complement label
Benefits • Easy dispensing
• Preserves freshness and integrity of product
• Increases shelf life
• Provides tamper resistance, deters pilferage
• Is spill proof
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Steel ends
•
Full panel
•
Partial pour
•
Mira strip (peelable and ring-pull options).
Aluminum easy-open ends
•
Full panel
•
Partial pour.
Flexible membrane
•
Paper or aluminum foil
•
Recessed membrane with plastic plug
•
Flat membrane applied to curl-top can.
Plastic
•
Full-panel easy-open end
•
Rotor-tops
•
Shake and pour
•
Overcaps.
6.6.6.2 Bottom end closures
Bottom end closures are primarily coated with steel although plastic, paper and
aluminum are used in some applications.
The strength of the steel end is generally correlated with basis weight and
temper. Commonly used base weights range from 55 to 107lb per basis box, with
temper ranging from T-3 to T-5.
Coatings may also be applied to the end closure. This is done to protect
the raw material from attack by the packaged product or other, environmental,
elements. Examples of coatings include tinplate (the most common), vinyl,
epoxy and phenolic. If maximum protection is needed, a sealing compound is
applied to the end. The compound serves as a gasket to seal the can and protect
the contents. The chosen compound is based on the properties of the product
being packaged.
6.7 Materials and methods of construction
As mentioned in Section 6.2, the composite can is made from several layers of
material, Figure 6.7, and is sealed with top and bottom ends. Material selection
and the final can composition are based on customer needs and end-user
preferences.
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6.7.1 The liner
The function of the liner is to provide product protection. It must be impervious
to attack by the product, and at the same time resist transmission of its own
components into the product. The liner must also maintain its integrity under
impact from external forces, particularly during shipping. In some applications,
such as salty snacks, it must also resist abrasion and puncture from within. In
some cases, the liner must also act as a barrier to oxygen and moisture, while in
others, it serves only to prevent product leakage.
Depending on the product to be packaged, the liner is structured with two or
more layers of material. Materials used on the product contact surface include
polypropylene, polyethylene (PET), Surlyn
®
, metalized PET (MPET) and
others. In order to maintain a complete barrier with spiral winding, the edge of
one spiral winding overlaps the preceding winding, the edge is turned
Lable
overlap
Body ply
skive
Outer
body ply
Label
Inner
body ply
Liner
Body ply
skive
Anaconda
fold and
seal
Figure 6.7 Cross section of composite can body. Source: Sonoco.