Sustainable Plastics - May/June 2020 - 32

recycling
continued from page 31
may occur, such as products
exhibiting poor surface quality
or big variations in melt viscosity," Holzner said. "Converters
using recycled materials tend
to mix this with virgin material.
By restabilising the recyclate,
the percentage of recyclate that
can be used can be increased,
which contributes to the sustainability of the polymer in
its application and widens the
range of products for which the
recyclates can be considered."
Preferably, the stabilisers are
added prior to regranulation. As
Holzner explained: "It's because
of the damage done to the polymer during recycling: first it's
melted, then typically, in order
to purify the material, this is followed by a melt filtration, which
means the waste is passed
through fine filters to eliminate
the impurities. But to achieve
the low viscosity needed to
pass it through the filters, the
processing temperature must
be increased."
He
added:
"And if the stabilisation package
is added upfront, a stabilization effect will
occur already at
this stage, and
the
recyclate
production process will not deteriorate your material. Once
the material is harmed, this
cannot be compensated for
by using additives.
Adding the stabiliser as early
in the process also avoids the
polymer balancing on the edge
of being under stabilized, with
for example flowability variations
as a result. Stabilisation ensures
a more uniform product."

How does it work?
A typical stabilising package
for polyolefins consists of three
components. The first is an antacid, which destroys all catalyst
residues and protects the other
additives. In the recycling process it takes care of acidic species that may have contaminated the material during product
life. However, in the recycling
process the second component
is more important. This is a process stabiliser, or a secondary

May/June 2020

antioxidant, which protects the
polymer chains from decomposing. Adding the third component - a primary antioxidant
to the system - then provides to
the polymer the stability needed for long-term use.
"It is about avoiding degradation of the polymer during the
regranulation process and adding to the long-term stability of
the product," said Holzner.

Polyolefins have the
highest potential
with regard to
upcycling."
Andreas Holzner
Baerlocher
It is, however, relatively sophisticated chemistry and recycling is an extremely price-sensitive market. As a result, many
recyclers prefer to avoid adding
costs to their system. And as
long as the recycled resins are
destined for 'low profile' applications, this is not a problem.
However, as Holzner pointed
out, Europe's circular economy
ambitions and the Green Deal
- the roadmap for making the
EU's economy sustainable -
involve commitments from society and the plastics industry
regarding the use of recyclate.
"More recyclers need to learn
how to offer a more consistently performing recyclate. If we
really want to be able to use
recyclate in applications which
are exclusively or mainly served
with virgin polymer today, then
we need to protect the polymer
during the recycling process.
And today, more and more re-

cycling companies realise this.
Plus there are a lot of brand
owners working with them,
communicating their expectations and their specifications
to them. At that point, the recycling companies realise that
they have to act."

A sustainable
technology
Baerlocher has developed
a resin stabiliser technology
which is sold as a formulated
product to the recycling market under the Baeropol brand
name. Dust-free, easy to handle and reliably free flowing,
the technology is tailored to
the environment of a recycling
facility, offering the efficiency of
the additive package with high
workplace hygiene. The products, both for post-industrial
and post-consumer waste, are
selling well.
"Even now, despite the fact
that currently mineral oil prices
are down and virgin polymers
are cheaper than they used to
be, our sales are good. With
brand owners following a clear
philosophy of increasing the
recyclate content of their packaging materials, the demand is
there," said Holzner. Although,
he added, in recent weeks, the
feedback from the market is
that demand for recyclates is
finally starting to slacken due to
'less demand in various industry
segments and lower pricing of
virgin polymers'.
Yet, with the increasing
popularity of online shopping
- especially in these times of
COVID-19 - more and more
packaged products are being
purchased, which means more
and more packaging films to
be recycled.
"And using the right stabilizer
technology means that you can
actually engage in upcycling,"
said Holzner. While regulatory aspects still prevent the use
of this recyclate in most food
packaging and the packaging
of pharmaceutical products,
other high-value applications
are certainly possible.
Such as?
"For me, a high-value application is when, by ensuring that
the recyclate meets strict, narrow specifications processes the

same way every time, your customers are able to serve higher-demanding applications. So,
producing recyclate for blown
film, for example, the stabiliser
technology ensures that you can
filter fish eyes out, that you have
a consistent melt strength and
that consequently the bubble
doesn't burst," said Holzner.
"In other words, a recycler
selling this can now upgrade
the recycling stream, specify
closer tolerances and can guarantee to film producers that if
they purchase this grade, there
will be no viscosity variation,
no melt index drift. For me, applications with high value are
applications with long lifetimes.
And that, as a recycler or a converter, it is possible to replace
more virgin material with recyclate with the help of additive
technology."

What's next
Next to developing stabilisation technology, Baerlocher is
also working on additives for
HDPE - for recycled bottles, for
example.
"Specifically, we are working
on melt strength enhancers
with a certain compatibilising
effect," said Holzner.
One of the crucial issues in
recycling is the quality of the
collection and sorting process:
how clean is the waste stream?
For recyclers, up to a certain
percent of 'contamination' is
permitted - up to 5% PP in PE.
"Additives are used to help
with the compatibilization of the
different polymers and improve
the further performance of the
recyclate," said Holzner.
Baerlocher is working on the
development of additives for increased melt strength, improved
processability, and, in addition,
is collaborating with polymer
producers on the optimisation of
their stabilisation concepts.
"Currently, most resins are
stabilised or additivated for
one-time use: we are also working with polymer producers to
enable them to add higher level
of stabilisers, making their polymer grades again more suitable
for recycling. In other words, we
are working together with both
sides of the value chain: with
the polymer producers and the
compounders."

Sustainable Plastics - May/June 2020

Table of Contents for the Digital Edition of Sustainable Plastics - May/June 2020