C☆iGum™ modified starches for high bonding performance, Ivo Baumann, Senior R&D Specialist at Cargill, Michael Stratemann, Senior Technical Account Manager at Cargill

PAPERTECHNOLOGYINTERNATIONAL
C iGum™ modified starches for high bonding performance
Making the adhesive difference in your corrugated board production with your star for starch
Ivo Baumann, Senior R&D Specialist at Cargill, Michael Stratemann, Senior Technical Account Manager at Cargill
INTRODUCTION:
Machine performance, cost-in-use, glue-and energy-consumption are all key criteria for a successful and efficient operating
corrugator. The impact of modified starch in the corrugating adhesive is often underestimated, with this key component instead treated as a
simple commodity product. This is an oversight, as good quality modified starches can make the difference in corrugated board production.
In fact, modified starches play an increasingly significant role in unlocking the full potential of modern corrugating machines. That’s where
Cargill comes in as “your star for starch” to help deliver the solutions for your success.
Starch types and process for glue formulation
Botanical origin has long been considered as the
main criteria in starch selection when targeting specific gluing
characteristics for a wide range of corrugated board products and
applications.
Application specialists were confronted with the decision on
which starch type to go for to reach enough machine and bonding
performance, and how to define glue recipes accordingly.
The main botanical sources of starch used for glue
formulations are wheat, corn, potato and pea (see Picture 1).
•
Corn starch adhesives typically require more caustic
and are less responsive to energy and Borax. This
makes them well suited for boards that are produced
at lower speeds and those that require more heat (e.g.
Kraft liner papers) and heavy board production.
•
Wheat starch glues can be set up for lower gel-point
temperatures. They may require less energy and build
up viscosity faster when exposed to heat. Hence, they
are ideal for fast running machines
with high production rates.
•
Potato or pea starch glues are
sometimes used to ensure good
ply bonding if there is a lack of
initial tack due to more difficult
energy transfer. They are suitable
for challenging applications, e.g.,
for the upper double backer on
triple wall machines.
In this context, synthetic additives
like rheology modifiers or performance
enhancers have also made their way into
glue formulations. However, this is increasing
complexity in the glue kitchen and significantly
affects adhesive cost.
While various glue preparation concepts have been
developed during the last decades, the Stein-Hall process remains
the most widely used by far. This process can either include the
classical 1-tank concept or a modern 2-tank system, with the latter
offering high glue preparation capacities with relatively small tank
volumes.
For the Stein-Hall adhesives, roughly 10-15% of the total
starch in the adhesive is hydrolyzed to form a viscous fluid.
This fluid stabilizes the suspended secondary starch, but
also helps to determine the rheological behavior of the adhesive
during the various process stages and conditions along the
corrugator.
The other 85-90% of the total starch content remains
dispersed in the granular form and is not activated in the cold
adhesive. When exposed to heat, however, it drives the overall glue
viscosity level and so leads to glueing the paper plies together.
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