Injection Moldings for the Compost

ON THE SPOT
Flow-optimized molds
shorten the cycle time.
In one case, the diamond pattern acts as an
additional flow channel
(far left) because of the
somewhat larger wall
thickness at this point;
in another case (third
from left), a combination of a slightly increased wall thickness
and greater radii between the container
base and wall improves
the filling behavior
(figure: Biofibre)
Natural-Fiber-Reinforced Biomaterials. Almost unnoticed by the
public, a manufacturer of elastomer injection molding machines two
years ago founded a subsidiary aimed at biodegradable materials. The
development of natural fiber-reinforced biomaterials is now gaining
speed, and their adaptation to injection molding is opening the door
to a world of “green” applications.
Injection Moldings
for the Compost
hat does a manufacturer of injection molding machines for rubber processing do to
equip himself for the green future of the
plastics industry? He founds a company that develops and processes biomaterials. And what if he lacks
the necessary experience? He enters into a cooperative venture with a manufacturer of plastics injection
molding machines. “So you want to know how a
caoutchouc machine manufacturer gets involved
with renewable raw materials,”says Peter Steinl, managing partner of LWB Steinl & Co. KG, receiving the
visitors in the conference room of his company in
Altdorf, just outside Landshut in South Germany.
W
Translated from Kunststoffe 4/2013, pp. 36–41
Article as PDF-File at www.kunststoffeinternational.com; Document Number: PE111298
24
An Unusual Liaison
This story, and this unusual liaison, starts some years
ago. At K 2004, Steinl was approached at the LWB
booth by the founder of Napac Schweiz AG, which
processed a polymer based on renewable raw materials into compostable plant containers using manually operated presses. His request was to automate
production. “It struck a chord with me,” said Steinl,
“as I’ve been thinking about new sales markets for
our machines for a long time.” So LWB Steinl developed a press for Napac, which produces the plant
containers, marketed as “NaturePots,” by compression molding and automatically ejects them, already
stacked. His ulterior motive was to build up a second
product line of machines for processing renewable
raw materials – beyond its injection molding technology, which is targeted at the rubber industry.
© Carl Hanser Verlag, Munich
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ON THE SPOT
Peter Steinl (right), head of LWB Steinl, confines his activities to developing and producing raw materials mixtures and subsequent applications,
Korbinian Kiesl (left) provides the machines suitable for this
Steinl attempted to persuade Napac to move from
compression to injection molding and to benefit
from the volume and cost advantages of this production process, which is predestined for large quantities; however he was wasting his breath.“We reached
an agreement that we would both continue using the
existing machine base, and development of the material for injection molding purposes would be continued by LWB itself. When, following the unexpected death of its founder, Napac went into liquidation
in 2010, Steinl acted promptly and transferred the
bio plant containers business to Biofibre GmbH, a
100 % subsidiary of LWB Steinl, which had been
newly founded at the Altdorf site.
Since then, the material tinkers at Biofibre have
made decisive progress. The material that Napac
processed by compression molding was a mixture of
35 % cellulose acetate (CA) and 65 % natural fibers,
which was not useful for injection molding. But the
LWB team has recently successfully completed its first
successful injection molding trials with a compound
of 60 % CA and 40 % natural fibers.And this is where
the new partner enters the story. In January, the
French injection molding machine manufacturer Billion equipped the pilot plant in Altdorf with a machine from its all-electric Select range.
Josef Diewald, Jörg Wittgrebe and Rainer Schmidt (from left) in front of the
new Select H260/100 T, which, in a test run with 200 mm/s injection velocity and
2,200 bar injection pressure, easily molds the first containers (figures: Doriat)
Ridiculous Cycle Times
“Actually we wanted to construct the machines for
processing these biomaterials ourselves, that was item
two – besides material development – of our original strategy. But we quickly found that plastics processing machines are ideal for these applications.And
there is no shortage of plastics machinery makers in
the world,” says the LWB boss, and continues,“As regards dynamics, precision and control technology,
plastics injection molding machines are years ahead
of machines for rubber. They simply laugh at our cycle and demolding times.”
Korbinian Kiesl doesn’t blush at these words. The
Munich-born entrepreneur, who bought Billion out
of the former Mannesmann-Demag conglomerate
at the end of 2005, puts things into perspective: “To
be fair, they don’t need this speed. If you injected rubber as fast as we inject thermoplastics, you would only have vulcanized material in the mold.What we lack
in rubber know-how, you lack in thermoplastics
know-how. So we complement each other. And
there’s a small area of overlap – thermoplastic elastomers, which play an important role for us in multicomponent technology.
Seeing Steinl and Kiesl together, you can sense how
well they get on together. “Both are medium-sized,
owner-managed companies who compensate for
their deficits with strategic partnerships. And two
Bavarian-owned companies, that’s also a good fit,”
says Kiesl with a twinkle in his eye. Steinl adds,“There
must be a foundation of trust. The things we are planning together can’t all be framed in contracts.”
A Material that Composts Itself
About 25,000 metric tons of plastics are consumed for the
production of plant containers in Germany alone (figure: Biofibre)
Kunststoffe international 4/2013
There’s no lack of ideas and commitment at any rate.
At least this is the impression conveyed by Josef
Diewald, managing director of Biofibre, who is cautiously but firmly laying down the framework for the
immediate future. All these considerations center on
the material. “Here, we have an injection moldable
material that is biodegradable and compostable. This
material is derived from renewable raw materials that >
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25
ON THE SPOT
do not compete with food production,” stresses
Diewald. To avoid the risk of being drawn into the
heated debate about “food or fuel,” Biofibre only uses selected raw materials – for the fibers, for example, grain or rice husks, i. e. waste products of the
crop, or Miscanthus (Chinese silvergrass), which is
cultivated on agricultural compensation areas.
The natural fibers are compounded on a twinscrew extruder together with cellulose acetate, which
originates from the pulp industry and, unlike the
polylactic acid (PLA) that is in strong demand in the
industry, is also not affected by the question of
acreage competition. “Apart from that, PLA is more
difficult to process with fiber raw materials,” says
Diewald, recalling certain failed trials with a pained
expression. The natural fiber biopolymer compound
– the matrix also contains small amounts of resins
and waxes – is supplied to the machine as pellets, and
can also be processed in a standard process. The plant
containers produced by this method are just as stable to handle as their synthetic PP counterparts, and
must take on the competition,” says Diewald. “We
have a clear goal of what the material may cost per
kilogram in which formulation.”
How Do You Reduce the Material Price?
An end price of EUR 2.50/kg could help this vision
to make a breakthrough, if the prices on the raw materials markets can still be calculated at all.“If the cigarette industry dies, the problem will disappear in
any case,” says Peter Steinl complacently about the
cost calculation – referring to the fact that most of
the available CA is used for cigarette filters. But it
would be rash to put all ones hopes on this, and Biofibre is therefore quietly also looking in a different direction. The CEO doesn’t want to say anything about
it, but when asked admits that they are working with
the Wissenschaftszentrum Straubing, and the department of chemistry of biogenic raw materials there
(which is attached to the Technical University of Munich).“There will certainly be some results this year,”
The natural containers are planted with
the plant and degrade
within six to
24 months, depending
on the soil conditions
(figure: Biofibre)
are also suitable for automatic production processes, but can also be planted in the ground and so protect the plant’s root structure. As was confirmed by
the internationally recognized Belgian test company
Vinçotte, the container, with 65 % fibers, degrades
within six to 24 months, depending on the soil conditions. For the injection molded option with 40 %
fibers, Diewald expects a corresponding certificate to
be granted by mid-year.
But that is not the end of the development, “even
if we have achieved an optical and tactile quality that
is unique for a bio-material,” says Josef Diewald,
showing the visitor flawless containers of different
shapes and sizes that really feel good to the touch.
“We are currently working on increasing the natural
fiber content to 50 %, and adapting the process technology to control this process. This makes good sense
– the material would be cheaper overall. Biofibre currently pays about EUR 3/kg for the CA, and the price
for natural fiber recently rose from 10 to 15 cents/kg.
This price probably also reflects the stronger demand
for energy recovery. “A lot is possible in the field of
biopolymers, with the price only playing a subordinate role. But we want to make inroads into applications for which that does not apply and in which we
26
says Diewald. One thing is clear – the as yet unnamed
biopolymer, which is available in huge quantities, will
certainly open up new price horizons.
Cars Later, Packaging Now
Though the company’s activities in the gardening
market are an obvious field – according to Napac’s
original figures, about 25,000 metric tons of plastics
are consumed for the production of plant containers in Germany alone – the suggestion of new applications attracts interest of course. It is common
knowledge that, prompted by the sustainability debate, the car industry is looking for new ways to increase its use of biopolymers. “We actually have requests from car manufacturers, but I have had to hold
back for the time being. We are nowhere near applications in cars at present, not least because of the
question of heat resistance. But I’m firmly convinced
that this will come in the next ten years,” says Peter
Steinl, adding that LWB has entered a cooperation
agreement with a large, locally based automotive supplier to develop the material in this direction.
As a higher priority than auto making, Biofibre
has its sights trained on the packaging industry. Ac© Carl Hanser Verlag, Munich
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ON THE SPOT
Even if marked PP, the
container is made entirely of bio-material. It
has been developed so
that it can be used in
standard injection
molds. Next to it are
some samples from other tests (figures: Biofibre)
cording to authorized signatory Rainer Schmidt, who
has accompanied LWB’s bio-activities from the start,
the company now wants to manufacture flat film in
a first pilot application. The material’s optical and
tactile properties make it ideal for design-oriented
natural packaging, and they are already in contact
with some food discounters. The prospects are good
for replacing the starch-based paper trays, mainly
bought from China, which are often used to package
fruit and vegetables, adds Josef Diewald, continuing,
“If we succeed in developing competitive film from
our material and pressing it into trays, we have a good
chance of penetrating into the entire food packaging area.As far as I know, that would be the only packaging so far consisting entirely of natural fiber-reinforced biopolymers and, what is more, it is derived
for the most part from local sources.” This is an im-
i
Process Technology
It all began with manufacturing plant containers from a
compound of 35 % cellulose acetate and 65 % natural
fibers by compression molding. This involves metering a
cylindrical pellet (diameter approx. 6 mm, length approx.
10 mm) by electronic weighing. The material is plasticated in the heated mold as it is pressed. The part is produced in cycle times of 10 to 12 s. Injection molding such
a container (28 g part weight) on a machine with
1,000 kN clamping force, on the other hand, only takes
7.5 s. However, the original material did not have adequate flow characteristics for this process. Success was
achieved with a mixture of 60 % CA and 40 % natural
fibers. Now, Biofibre is working on further increasing the
fiber content, but with the proviso that none of the raw
materials must compete with food production.
Kunststoffe international 4/2013
portant sales argument today, not only for so-called
“Lohas” (lifestyle of health and sustainability).
The material developers are currently testing the
matrix and fibers in different percentages, and with
various additives to modify the properties according
to needs. Of course, that also means that, if the material cannot manage without additives, they, too,
must be bio-certified. Biofibre is currently working
together with Wacker Chemie in Burghausen, Germany, which has the technical facilities for producing sample films and sheets. Diewald shows us a sample with very pleasant tactile properties: “With the
next batch, we will have reduced the thickness from
1.3 to less than one millimeter. We are already holding talks with a manufacturer who works with ecopackaging. We are talking about a potential of many
million units per year.”
Clear Fronts
But all that is a long way off, at least until the thermoforming process for mass production of packaging has
been mastered.And Korbinian Kiesl need not concern
himself with that. So let’s stick with injection molding – where process optimization is in full swing.“We
have long been familiar with glass fiber-reinforced materials. We also have experience with processing WPC
– that is always a mixture of wood components and a
polymer. But injection molding purely with natural
raw materials was also new to us,”he admits.“And nevertheless, we understood one another straightaway: It
works,” confirms his cooperation partner, Steinl.
Kiesl brought Jörg Wittgrebe, Billion’s director in
Germany, with him to Altdorf. The engineer explains
the technical points: “Even though the natural-fiberreinforced material has very exceptional behavior, this
is a normal injection molding process. Only the pro- >
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ON THE SPOT
cessing temperature at about 190°C is lower than for
a standard thermoplastic. And we use a screw with a
mixing head to achieve better homogenization of the
material.” Since the material freezes relatively quickly
and the moldings are thin walled, according to
Wittgrebe, the machine is set for high injection velocity and pressure.For venting the mold – a critical point
in such applications – the Select range is equipped with
the “Easyflow” function. Once the mold is closed, the
full clamping force only builds up gradually in several stages on the start of injection – the air can escape
via venting channels in the parting line.
Peter Steinl is impressed by the all-electric Billion
machine: “Mold exchange takes place very rapidly,
the machine returns to the operating point with the
first shot.” In a direct comparison of the processes,
the fronts have already long been clear: While the
plant containers have wall thicknesses of 1.2 mm in
compression molding, the injection molding trials
have already succeeded with 0.8 mm; and, with a
flow-optimized mold machined with a diamond pattern, even 0.6 mm. It goes without saying that each
material saving additionally improves the market
chances (not to mention the cycle times). Biofibre
and Billion will be putting a great deal of thought into this, too, as well as into their plan to increase the
fiber content significantly, too. “We still haven’t exhausted the potential, neither with the machinery
and mold nor with the material,”says Jörg Wittgrebe,
summing up the status quo.
Anyone Who Doesn’t Start Now …
Steinl’s financial commitment leaves no doubt that
he is serious about his start-up: “So far, we have invested over half a million euros in the development
and want to build up a long-term business. Our goal
for coming years is to develop the company from
our cash flow.” Steinl has no doubt that raw materials, along with alternative energy sources, will be the
crucial issue in the medium and long term. “Anyone
who doesn’t start building up competence now will
soon have problems catching up. It isn’t something
The injection molded bio plant containers are optically and
tactilely flawless (figure: Doriat)
you can do in passing.” And when does he expect the
breakthrough? “I can’t say whether it will take two or
five years or longer. It depends on the impact of the
global economy and the development of oil prices.”
Then the LWB head reaffirms his commitment to
his new partner: “We will work together exclusively
with Billion in this field; after all, Mr. Kiesl has invested here, too. That’s what we mean by dealing fairly with one another. But if a customer wants to use
his own machines, we will have no choice.”And turning to his visitors: “The topic is still so new and the
portfolio of our possibilities so huge – if you come
back in six months we will have a lot to tell you
again.” Clemens Doriat, editor
In two-shift operation
and with about 250
work days per year, the
two compression molding machines in Altdorf
can produce between
2.5 and 4.5 million plant
containers, depending
on the product. The
main customers are
horticultural stores
with bio product lines
(figure: Biofibre)
28
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