NFM
Plastic Devolatilization
In the field of polymer
devolatilization, NFM/Welding Engineers holds an
impressive array of experience and accomplishments
that include:
- patented multi-stage venting
- rear venting
- counter-current and co-current
stripping
New products include:
- streamlined preconcentration
systems that maximize output and quality of
solution polymers
- large-scale processing techniques
for extrusion drying of elastomer solutions.
Over 25 years ago, NFM/Welding Engineers was the
first manufacturer to commercialize twin screw devolatilization
of reactor solutions with 6" lines for devolatilizing
acrylic and styrenc polymers from 50% solids. We
are currently enganged in the creation of a new generation
of devolatilizing equipment.
The Advantages of
Twin Screw Extrusion
- Capable
of Handling Many Viscosities:
Twin screw
extruders excel in positively conveying
high viscosity fluids. By contrast, other
equipment may have torque limitations
or insufficient conveying capabilities,
resulting in material degradation and
long changeover between product grades.
- Contained
and Recoverable Waste Streams:
The design
flexibility of NFM/WE extruders allows
environmental considerations to be addressed
as part of the process.
- Short
Residence Time:
Our twin screw
design has the shortest residence time
of any devolatilization device (less
than three minutes, typical). Changeovers
are faster, thermal history is minimized,
and product is less likely to be degraded.
- Efficient
Heat Transfer:
Twin screw
extruders can increase temperature by
controlled shearing of the polymer solution.
Other devices rely on surface renewal,
pressure, and conductive heat transfer
for devolatization.
- Narrow
Residence Time Distribution:
Gel information,
discolored product, or broad molecular
weight distributions are reduced by the
design of the twin screw, small volume
and positive conveying characteristics.
- Efficient
Surface Renewal:
For highly
concentrated polymer solutions (less
than 1% solvent), twin screw extruders
are ideal for renewing surfaces through
the use of multi-flighted screw elements
and high screw speeds.
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SUCCESSFULLY
DEVOLATILIZED POLYMERS
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Styrenic Materials |
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SAN
ABS
SMA
SB Copolymers
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SIS, SEBS & SBS
Block Copolymers
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Engineering Thermoplastics
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Polyarylate
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PEI
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Synthetic Rubber
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SBR
EPDM
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PBd
Silicones
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Other Materials
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PMMA
PE
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PP
Expoxies
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The
Advantages of an NFM/WE Twin Screw Extruder
- Large
Free Volume Contains Foaming Melts:
NFM/WE's counter-rotating,
non-intermeshing screw design has the largest
free volume capabilities of any twin screw
extruder manufacturer for containing foaming
melts (typical of 30%-50% solvent concentrations).
This extra free volume also means that
we can provide longer residence time under
each vent reducing tendencies for vent
flow and overall better performance and
operability.
- Large
Vents Up to 6 D Long by 1 D Wide:
Our extruder
design offes longer, wider vents allowing
vapor velocity to be lowered and the entrainment
of the polymer to be reduced accordingly.
Larger vents also mean higher vapor removal
capability, due to low velocity when removing
large amounts of solvent and extra residence
time under vacuum removal of the final
parts per million of solvent.
- Downward
Screw Rotation Resists Vent Fouling/Flow:
Our design allows
the barrel to be open for a vent over a
full diameter directly over the center
of the screws (and wider in some cases).
The screws' rotation acts to pull polymer
down in the vents, thus resisting vent
fouling or flow.
Process Parameters
- Viscosity
Range:
5,000-5,000,000
centipoise @ 100 reciprocal seconds, 20-80
Mooney Viscosity.
- Free
Solids Content:
30% and higher
to the extruder.
- Temperature
Control:
Temperature is
controlled by screw design, screw speed,
and barrel temperature regulation. The
use of water stripping may also provide
some cooling capacity.
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Contact
Us
- For more information on devolatilization
or any other processes made possible by an
NFM/Welding Engineers' system, please contact
us. We would be glad to provide additional
data or technical support at any stage of your
project.
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