ACA Sustainability Report 2022 - Report - Page 23
Innovation Leads to Environmental Improvement
MEMBER STORY
High-Performance Aliphatic Hardener Takes
the Next Step in the Sustainability Journey
Something exciting has happened in
the polyurethane world. For multiple
decades, aliphatic polyurethane
coatings have long been recognized as
the high-performance option for critical
applications such as automotive,
industrial, and infrastructure due to the
inherent strength of the polyurethane
bond and the excellent properties it
imparts. These proven hardeners,
while fulfilling the durability and
aesthetic demands of the market,
have been traditionally formulated with
fossil-based raw materials. However,
aliphatic hardener technology has
taken the next step forward.
Covestro has developed a new
aliphatic hardener, the first in the
market in over 30 years, that has
replaced a significant amount of the
fossil-based carbon content with
over 70% of bio-based material. The
polyisocyanate, Desmodur® eco N, is
a pentamethylene diisocyanate (PDI)
based trimer and yields excellent
properties like hexamethylene
diisocyanate (HDI) trimer. A unique
feature of this bio-derived material is
that it utilizes non-edible corn starch
which is enzymatically converted by
specially developed microorganisms
in a highly efficient manner. The
Desmodur® eco N version has been
developed to be similar to existing HDItrimer for use in solventborne topcoats
and the Bayhydur® eco N version is
hydrophilically modified to have better
compatibility in waterborne systems.
With the creation of this bio-based
aliphatic hardener, formulators have
begun to use this new building block
within current developments. Two
examples are the use of the crosslinker
in a two-part automotive OEM exterior
clearcoat. The coating needed to meet
current stringent testing specifications
with no sacrifices in performance. It’s
very important to note that moving
to bio-based materials does not have
to equate to reduced performance.
These two automotive manufacturers
desired the sustainability attribute of
a bio-based aliphatic hardener while
retaining the proven performance value
of a polyurethane clearcoat.
Chemists are also evaluating the use of
this unique hardener in the formulation
of abrasion and chemical resistant
concrete floor coatings. The coating
can be classified as a polyurethane
or a polyaspartic depending on which
resins are used, but in either case the
expectation is for similar floor coating
properties such as durability, stain and
chemical resistance, and long-term
color and gloss retention. However, it
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is not enough to include the bio-based
trait while allowing other environmental
concerns to suffer. So, the new
hardener has a similar viscosity profile
as traditional products which allows
for the formulation of ultra-low VOC
construction coatings – continuing
the downward sustainability desire for
lower VOC.
Similarly, the high bio-based hardener
is of interest to coatings companies
that formulate fluid-applied reflective
roof coatings. For this application,
the final coating supports two
sustainability drivers – bio-based
content and energy efficiency. In
particular, two component aliphatic
polyurethane roof coatings are not
only durable, they also have the
all-important quality of reflecting
sunlight’s IR rays rather than absorbing
them – initially as well as years after
application. Since there are existing
aliphatic polyurethane roof coatings
available with 22 to 25% range using
resins, this bio-based hardener would
allow for sustainable roof coatings with
a bio-based content more than 50%.
A step in the right direction!
Learn more at https://www.covestro.
com/en/sustainability/what-drivesus/circular-economy.