Aseptic advances - the Tetra Evero milk carton bottle

Packaging Professional magazine
,
17 Jul 2011
Tetra Pak aseptic milk carton

The world’s first aseptic carton bottle for milk has been launched
by Tetra Pak. Felicity Murray visited the company’s headquarters
in Lund, Sweden, to find out more about the engineering processes
that have come together to create Tetra Evero.

Product innovation is an ongoing
process in the various departments of
Tetra Pak’s massive site in Sweden.
The latest development from their stable is
the Tetra Evero Aseptic, which combines
the convenience and functionality of a
bottle with the benefits of a carton system.
The makers claim the container’s one-step
opening and closure, easy handling and
pouring, cost and environmental qualities
give it the edge over other aseptic bottles.
The bottles keep milk safe and fresh
in ambient conditions for up to six months. The TEA and new Tetra Pak A6 iLine
are covered by 14 design and
application patents. Developments include
an industry-first ‘gas phase’ sterilisation
technique and advanced injection
moulding technologies to fuse the top,
carton sleeve and capped neck into a
ready-to-fill package.

Speed to market

Tetra Pak uses advanced computer
modelling to create virtual simulations of
fluid dynamics, which is how the gas phase sterilisation technique was developed, as
well as the ideal pack shape for optimum
product pour. Using more traditional
engineering approaches to test machine
types would have involved thousands
of man-hours and taken several years –
simulation ensured that it took months.

Market drivers

Globally, the key market drivers are
functionality, brand differentiation, system
cost, environmental sustainability, and
food safety and traceability. To meet these growing demands, the company
set out to design an environmentally
sustainable package that not only provides
differentiation on-shelf for brand owners,
but also provides consumers with added
convenience and greater food safety.

Initially the TEA is aimed at the ambient
white milk market and non-oxygen
sensitive milks, such as those enriched
with calcium, proteins, fibres (inulin),
vitamins A and D and some minerals.
However, the next stage of development
will expand its suitability to cover a wider
range of beverages, including flavoured milk, cream and oxygen sensitive milk
products, such as omega 3, iron, zinc, and
vitamin C.

The body of the pack presently comprises
the same multi-layer FSC-certified
paper-board composition as existing
Tetra Pak cartons and has a similar folded
carton base. The top edge is sealed to a
‘green’ HDPE-moulded top with integrated
closure that is derived from crop-sourced
oils rather than petroleum. The next
generation of Evero carton bottles,
expected in 2012, will comprise a ‘green’
PE-coated sleeve and cap that will be constructed so the consumer can
separate the carton material from the
plastic top for recycling. The next step is to
make the packaging process suitable for
oxygen-sensitive products.

The aseptic closure has a one-step
opening/closing mechanism that negates
the need for an additional foil seal or
ring-pull. The thread of the cap is such that
the upper section of the cap sheers off the
inner membrane in a controlled process as
the cap is turned.

The bottle sleeve is an ergonomic
cylindrical shape with flat side panels to
make it easier to hold. The shape also
provides the ideal angle for pouring.

Forming and filling

The pack is formed and filled in a new,
compact, Tetra Pak A6 iLine, which offers dairy producers a more cost-effective and
efficient packaging solution for ambient
white milk in a bottle. It has a capacity of
10,000 packs/hour and, compared to PET
aseptic bottling lines, requires up to 50%
less space, calls for 30% less investment,
offers 25% lower operating costs and
requires half the electricity consumption.

The roll-fed packaging material is
automatically fed into the machine, cut
into blanks in the sleeve-forming unit,
then wrapped around a mould and sealed
to create accurately formed sleeves. The
neck and cap are then injection-moulded
onto the in-line moulded plastic top,
and the carton sleeve and top fused
together. As this function is integrated
into the machine, it saves space in the
production hall.

Injection-moulding

In the injection-moulding process, hot
melted plastic is forced into a cavity in a
cold metal mould at very high pressure.
The plastic is cooled so it rapidly becomes solid. The mould is then opened, the
solid plastic part released and the
mould closed again ready for the next
cycle – all in less than 1.5 seconds.
Simplification comes from creating a mould
with only two parts – an inner and outer
mould – and integrating the injectionmoulding
module into the filling machine.
In addition, the carton sleeve is present
in the mould when the hot plastic is injected, meaning that the three separate
components – plastic cap, plastic top and
carton body – are fused and sealed.

While the mould is simple, the
engineering required to deliver it was
not. One of the challenges involved
development of the ‘hot runner’, which
injects the plastic into the outer mould. To
ensure consistent quality, the plastic must
be injected symmetrically and be heated to
210°C. If the temperature is too low, the
seal might leak – too hot and the
moulded top might deform. Applying
a systematic failure mode approach to
identify any factors that could impact the
equipment, Tetra Pak engineers and an
external specialist created a hot runner
using four inlet valves to deliver the
plastic symmetrically and at precisely the
right temperature.

Sterilisation

In a traditional brick-shaped carton,
materials come flat-packed, meaning they
can be aseptically sterilised before they are
formed into shape. But the TEA’s new
shape requires a different approach.

Sterilisation takes place in an aseptic chamber and is in three steps – the pack is
pre-heated, treated with evaporated
hydrogen peroxide and then ventilated
with a sterile airflow to remove gas
residues. The hydrogen peroxide comes
into contact with the whole preformed
package, both inside and out, removing
any contaminants that might have
been present before entering the aseptic
chamber. The sterilisation, filling and
sealing section is a completely sterile
environment protected by flows of overpressured,
controlled Hepa air.

The line also has an automatic fourstep
filling system with few moving
parts, to prevent air-flow disruption and
minimise foaming.

Further information

Tetra Pak Ltd, Bedwell Road, Cross
Lanes, Wrexham LL13 0UT, UK.
Tel: +44 870 442 6600.
Email: enquiries.uk@tetrapak.com
Websites: www.tetrapak.com and
www.tetrapaksustainability.co.uk