Sustainable Plastics -March/ April 2021 - 31

sustainable materials
continued from page 29

Chemical structure
of isosorbide.

ical feedstock so (partial)
substitution by plant-based
isosorbide is also potentially
appealing from the perspective of the material's environmental impact.

Isosorbide - what is it?
" Isosorbide is a really versatile,
safe, environmentally benign
performance chemical with
great potential as a co-monomer, " said Bruno Plancke,
head of Global BU Industry, at
Roquette, the France-based
leading producer worldwide of
plant-based ingredients such as
isosorbide for the performance
plastics and chemistry markets.
Isosorbide is produced from
annually renewable plant feedstocks by a process of sequential hydrolysis and hydrogenation. Hydrolysis converts plant
starches to glucose which are
subsequently converted to
sorbitol; the hydrogenation of
sorbitol to isosorbide is the final step. Isosorbide production
technology has been optimized
over the last two decades, to
minimize carbon footprint and
deliver consistently high purity.
Since starting production at
a modest scale in 2002 in Lestrem, France, Roquette has continued to expand its isosorbide
activities. Today, the company
operates a large-scale production facility at its Lestrem
site, using its patented sorbitol-based process to produce
isosorbide which is marketed
under the brand name Polysorb. The different purification
steps in the production process
produces isosorbide grades of
very high purity-over 99.5%
isosorbide content-which enables Roquette to comply with
all quality requirements of its
customers, as well as to support the development of innovative high-performance solutions for the global plastics and
chemistry industry. Its Polysorb
is a REACH compliant, non-toxic, non-endocrine disrupting,
valuable feedstock for multiple
applications; moreover, it is
suitable for food contact, and
compatible with cosmetic and
pharmaceutical requirements.
Previously, the availability of
a consistent supply of high-pu-

rity isosorbide tended to be
uncertain, but now, having successfully put a reliable, high
purity industrial-scale supply
of Polysorb isosorbide in place,
polymer manufacturers are free
to exploit its full potential, said
Plancke.

Leading the way -
SK chemicals
South Korean green chemistry and life science company
SK chemicals is one such polymer manufacturer. Early on,
the company saw the potential
of isosorbide to enhance the
properties of PET and realised
how this could even, in some instances, open up new areas of
use, such as hot fill.
" We've found that incorporating isosorbide can help PET to
perform perfectly in areas where
it currently fails, " said Eung-Soo
Kim, head of the Copolyester
business at SK chemicals.
" Hot fill for food and beverage is a prime example. Isosorbide is highly effective at
increasing Tg and allows us to
produce a stretchable, transparent, heat-resistant plastic
that can be directly substituted into existing blow moulding
processes. "
The company launched its
first polyethylene-co-isosorbide
terephthalate - PEIT - products
under the Ecozen brand name
in 2012, based on isosorbide
from Roquette. SK chemicals
has since continued to advance

the development of its Ecozen
portfolio, in cooperation with
Roquette.
According to Jiae Kim, Global Market Manager for Performance Materials division at
Roquette in South Korea, this
illustrates precisely the kind of
long-term, collaborative relationships Roquette maintains
with its customers.
" Roquette is not simply a
manufacturer of a plant-based
monomers; we are experts in
the chemistry of these monomers, " she said. " Developing
new polymers for specific applications is a demanding task
and the insight we bring to the
table is valuable to this process. "
Roquette considers itself
therefore far more than as just
a supplier, said Jiae Kim.
" We are very much an active
partner in the development of
new PEIT grades, " she stresed.
The development process was
one that demanded patience and
hard work to achieve the quality and performance attributes
required by the market, while at
the same time to delivering an
improved environmental profile.
" Since 2012, the Ecozen range
has been progressively segmented, refined and expanded
to closely match customer requirements, " Jiae Kim explained.
" For example, the Ecozen T polymers all offer chemical resistance, heat resistance and transparency but different grades
are tailored to provide different
levels of heat resistance, for de-

fined applications. In its entirety
this range is now suitable for use
in the manufacture of products
ranging from food containers
and baby care products to construction materials and household appliances. "
She added that PEIT can typically be processed using existing equipment and that many
grades can be directly recycled
into the PET waste stream. " In
other words, switching to PEIT
does not incur additional costs
in these areas, " she stressed.

Latest developments
SK chemicals has now developed two new PEIT polymers
tailored to the requirements of
hot-fill applications. Semi-crystalline and offering high thermal
stability, these polymers have
a glass transition temperature
of 90 or 95oC depending on
grade, in contrast to that of PET
- 70oC - and PETG's 70 -80oC.
PETG, a transparent copolyester, is a glycol-modified class of
PET; an example is Eastman's
Tritan material.
Both grades have undergone
extensive testing to establish
its suitability for hot-fill applications. These tests revealed, for
example, that the intrinsic viscosity (IV) of the new polymers
compares with a range of 0.6
to 0.85 for PET, depending on
application; PET for bottles typically has an IV of around 0.73
to 0.80. As IV is indicative of the
flow properties of the molten
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