Modern Plastics Worldwide - July/August 2009 - dae uptlax

PROCESSING
TECHNOLOGY
Traditionally, highly filled
polyolefin compounds have been
produced by repeated loading via
several feed positions on the compounding
extruder, followed by
mixing up to three or more times.
This, says Eitel, is done because
CaCO 3 , with a bulk density of
600-800 kg/m 3 , tends to be sticky
and build bridges, often creating
headaches for an operator. To
overcome such problems, agitators
are often used, hoppers are
designed with special geometry to
improve material drop, or flexible
walls can be incorporated that
can shake up the filler to break up
bridging.
Coperion says experience has shown,
in its latest line design for such applications,
that, during refilling of loss-inweight
feeders using slide, butterfly, or
rotary valves, the valve itself needs to
be installed closer to the feeder hopper
so that it can react quickly in shutting
PROCESSING TRENDS
Specific energy input drops, and pressure increases,
as filler content increases: that has been Coperion’s
experience with its new line for highly filled compounds.
off. This is necessary to avoid overfilling.
The company developed a new layout
for its ZSK compounder by mounting
the CaCO 3 feeder directly above the
unit’s co-rotating twin-screw side feeder,
ZSB. This setup, says Eitel, results in the
need for only two feeders and two refill
hoppers for the CaCO 3 . It also provides
Bioplastic barrier fi lm matches EVOH, PA
By Matt Defosse
Blown- and cast-fi lm extrusion
line manufacturer Colines (with
manufacturing sites in Novara and
Varese, Italy) says recent testing
proves that PLA/PVOH fi lms extruded
on the company’s cast- and
blown-fi lm lines with structures of
up to 7 layers and with thicknesses
from 50 to 90 μm offer sufficient
oxygen barrier properties, while
also maintaining top optical
performance, as shown by the
values of haze and gloss and the
fi lm’s printability.
Colines officials say the lines have been
modified so as to render the same performance
as lines running barrier films
containing polyamide or ethylene vinyl
alcohol (EVOH) barrier materials, with
no loss in line productivity.
The combined structure of polylactic
acid (PLA), based on plant starches,
and polyvinyl alcohol (PVOH, a biodegradable,
water-soluble polymer) in
these barrier films offers sufficient gas
barrier performance to prove them
suitable for use in applications such
as packaging of meat and fish, and, in
particular, fruit and vegetables.
The company invited interested processors
to its open house from July
27-31, 2009, and requested email preregistration
at marketing@colines.it.
Also during that open house the company
planned to run a line extruding
breathable film with an in-line double
mono-orienting unit (MDO). The line,
which can extrude breathable film in
PE and in PP, has a useful width of
2200 mm and the double-MDO unit
offers orientation of up to 600% (2 x
300%). It will feature post-stretching
embossing and comes outfitted with a
thickness control before and after the
a longer mixing section for the
filler, better dispersion, and higher
output. With the increase by percentage
of the compound/weight
of filler, the discharge pressure in
bar is increased while the specific
energy input measured in kWh/kg
is reduced.
Farrel takes a different approach
to compounding highly filled concentrates.
Its FCM (Farrel Continuous
Mixer) operates on the principle
that the material is exposed
to a variable mixing intensity in
the form of shear stress and strain
developed between the rotor tips
and chamber wall, as well as melt
blending by the kneading action between
the rotors. “The measure of dispersion
through either visual examination or
filter pressure values are as good or better
than those achieved with twin-screw
extruders,” says Broadhead. “Besides
that, we get the added benefit of lower
energy costs.”
stretching, with automatic adjustment
according to the set target. Trim is
recovered directly and pelletized.
It also includes the firm’s Fast
AdJUST (Elav) system for micrometric
adjustments of the stretching parameters
of the line. Colines reports it
has worked with this system and is
able to offer processors the option
of live monitoring of the data relative
to the extrusion lines. The report
system lets a user track consumption
data (energy and raw material), various
trends (throughout and machine data),
recipes, management of the production
orders, ordinary and preventive maintenance,
and diagnostics. The acquisition
and processing of the data are
incorporated directly in the automation
system, with the data then able to
be sent to computers on the other side
of a facility or even further afield.
18 JULY/AUGUST 2009 • MODERN PLASTICS WORLDWIDE mpw.plasticstoday.com