1. Electrostatic Reduction of Misting in Roll Coating
Bill Smith Polytype Converting GmbH
AIMCAL R2R Conference USA 2018
Phoenix, Arizona,
October 28-31, 2018

2. Polytype Converting Company Set-up
Global supplier of coating technology and coating equipment
High-end and performance-driven engineering with more than 50 years industrial experience
2 world class Technical Centers in Switzerland and Germany featuring pilot lines in total
Joint Venture between Olbrich and Jagenberg, allowing Olbrich and Polytype Converting to draw synergies out of their technology portfolios
Competences in:
Winding
Coating
Drying
Treating
Web handling
Automation
Customers have access to 2 Technical Centers:
Polytype Converting in Fribourg
Olbrich in Bocholt
Joint Venture between Olbrich and Jagenberg: 2 well-known companies in the converting business, financially strong with long term strategy
3 brands under one roof for continuity in Service, Spare Parts, Engineering, Representative Support:
Polytype Converting
Pagendarm
Olbrich CTH
A strong bond of solid partners to the coating and converting industry

3. Electrostatic Reduction of Misting in Roll Coating
Agenda
Electrostatic Reduction of Misting in Roll Coating
Introduction
Experimental
Results
Conclusions
Electrostatic precipitators are known for oil separation
What about to apply this technology in forward roll coating -> to reduce misting
Electrostatic DC Plasmas
Oil mist separation
Oil precipitators

4. Introduction Misting from film splitting Liquid passing through a nip
Misting can be observed at many places
Offset printing, Forward roll coating, ….
Misting Study examples: Michael S. Owens (PhD at L.E.Scriven)
Starts with ribbing lines
Liquid passing through a nip
Development of droplets upon splitting
High splitting speed
Particle size << 50 μm
Health, quality, cleanup, and cost issue.

5. Ribbing lines in forward roll coating
Introduction
Misting from film splitting
Ribbing lines in forward roll coating
Dontula 1996
Extended ribs break up
Michel S. Owens 2004
Misting can be observed at many places
Offset printing, Forward roll coating, ….
Misting Study examples: Michael S. Owens (PhD at L.E.Scriven)
Starts with ribbing lines at film splitting meniscus
Then break up in filaments

6. Introduction
Current options for handling the misting (example: silicone coater)
Chemical anti-misting additives
Mist particle evacuation W3 W2 W1 W0
W00
5 roll coater
5-roll coater: F. Krebs and P. M. Schweizer, Coating , p and Coating , p

7. Novel electrostatic approach from Eltex: Misting Tacker
Introduction
Novel electrostatic approach from Eltex: Misting Tacker
Eltex - new system - tested in offset printing:
Misting Tacker – Antimisting Bar
DC Plasma
Low energy DC-Plasma
Permanent operation above the electric break down voltage but no sparks
High electron density
Standard oil mist separators have to work below break down voltage to avid sparks -> low efficiency
The basis of electrostatic precipitators is the generation of a strong electric field with voltages far below the breakdown voltage in relation to the electrode spacing, in order to avoid uncontrolled local discharges and the associated sparking -> Poor efficiency, ...
F. Knopf, Eltex Elektrostatik GmbH, WO (A2), DE A1

8. Introduction: Misting Tacker
Low Energy DC–Plasma Electrode
DC-Plasma Deposition Unit view into a cross-section
Electrode Tip
Counter Electrode
Plasma Cone
ca.10 mm
Low energy DC plasma: high Voltage, but low current -> no sparks
High electron density
Operates permanently 1.5 x above break down voltage
Is placed closer to surface

9. Misting Tacker: Low Energy DC–Plasma Electrode
Introduction
Misting Tacker: Low Energy DC–Plasma Electrode
airstream
plasma cone
(ionization)
Low energy DC plasma: high Voltage, but low current -> no sparks
Principle of operation:
mist deflection instead of suppression
Air flow
Mist flows in boundry layer
Charged particle -> conducting and grounded roll
Typical voltages: kV; 1-4 mA
Boundary layer
Mist coming from the separation process of the formulation flows with boundary layer over the roller surfaces and is guided by electrostatic effects onto earthed rollers (fog deflection instead of
fog suppression)
- Fog at RW is suppressed very well, visible residual fog may be caused by lateral inflow.
- Mist deposits on cliché increase, mist becomes finer
deflection instead of suppression

10. Experimental Raw Materials Silicones from Bluestar:
Thermal curing 100% system
Curing at 180°C
UV curing 100% system
No initiators added, cured using e-beam
Substrates:
Craft Paper 35 µm, Cobb 30 g/m2
BOPP 50 µm
PET 12 µm
100% System without with Antimisting Additive:
Poly parts 100 parts
XL325 7 parts 7 parts
Cata 11091M 3 parts -
Cata parts (includes cat. and additive)
UV-System
Silcolease UV parts
Silcolease UV parts
Silcolease UV CATA part (not used, EB instead)
Silcolapse 801 batch15U111P01 (antimisting additive)

11. 5 roll silicon coater and electrode placement
Experimental
5 roll silicon coater and electrode placement
Feeding nip -> surface quality nip
W2 close to web speed
• Speed roll %
• Speed roll %
• Speed roll %
• Speed roll %
• Substrate speed 200 m/min
• Footprint rolls W00/W mm / W0 - PUR 80 Shore A
• Footprint rolls W0/W mm
• Footprint rolls W1/W mm / W2 - PUR 55 Shore A
• Footprint rolls W2/W mm

12. Techma coater – web upstream view (backside)
Experimental
Techma coater – web upstream view (backside) W3 W2 W1

13. Experimental – Data Collection
Measurement around Application Unit – Electrodes off
(600m/min)
(max. >150 mg/m3)
Trial #6; run 02:
Includes startup of machine Measurement web downstream (front side) then backside then from side
AU is not inside housing -> draft of air hampers measurement

14. Experimental – Data Collection
Measurement around Application Unit – Electrodes on
(600m/min)
(max scale of graph: 1.8 mg/m3)
Trial #7; run 03: Measurement around the applicator (front-back-front) with electrodes switched on (600m/min)

15. Experimental – Data Collection
Aerosol sensor placed at fixed point between roll W2 and W3
DustTrak DRX 8534 from TSI (

16. Results – Data Collection
Measurement of Aerosols at fixed point
step by step increase of web speed up to 1000 m/min
(max scale of graphs: 35 mg/m3)
Particle measurement at increasing speed levels up to 1000 m/min. Left without (Trial #08), right with Nips W0/1 cover (Trial#09-10)100 m/min
300 m/min
600 m/min
800 m/min
1000 m/min max value=25mg/m3 (scale = 35)
Masking of Nip 0/1 essential
Masking Nip W0/W1
Nip below aerosol sensor covered

17. Results – Data Collection
UV: Effect of misting from second nip (W0 / W1) - Run8: nip unmasked - Run9: nip masked
UV Silikon
Influence of Nip W0/1 cover on aerosol measurement; Trials #05-07 (Run8) without cover, Trials #08-11 (Run9) with cover
W1 at 70% ->
W0 at 12% -> high differential speed
Web speed
W1 speed
300 m/min
210 m/min
400 m/min
280 m/min
500 m/min
350 m/min

18. Results – Thermic Silicone
Comparison of electrostatic to chemical method - Run2: no measure - Run6: chemical additive - Run5: electrostatic DC-Plasma
Comparison of manuring with electrode or additive against no measure on paper substrate

19. Results – Thermic Silicone
Comparison of electrostatic to chemical method - Run5: electrostatic DC-Plasma - Run6: chemical additive
Comparison of efficiency of electrodes for antimisting additive (Trial #09 (Run5) with cover Nip W0/1 and Trial #11(Run6))

20. Results – Thermic Silicone
Comparison of effect by different substrates - Run5: 35 µm Paper - Run7: 12 µm PET
Comparison of substrates paper to 12µm PET (Trial #9-10 (Run5); Trial #12-13 (Run7) )
-> BOPP not possible due to drying temperatures

21. Results – UV Silicone
Comparison of electrostatic to chemical method - Run12: electrostatic DC-Plasma - Run13: chemical additive - Run10: no measures taken
UV system generally less misting (web speed limited due to E-Beam dose of 20kGy (570mA; 160kV))
Comparison of manuring with electrode or additive against no measure UV
Trials #19-22 (Run12): Eltex electrodes, on paper
Trials #23-27 (Run13): with antimisting agent, on paper
Trials #12-14 (Run10): no measure, on PET

22. Results – UV Silicone
Comparison of electrostatic to chemical method - Run12: electrostatic DC-Plasma - Run13: chemical additive
Comparison of manuring with electrode or additive against no measure UV?
Trials #19-22 (Run12): Eltex electrodes, on paper
Trials #23-27 (Run13): with anti-misting agent, on paper

23. Results – UV Silicone
Comparison of effect by different substrates - Run9: 12 µm PET - Run12: 35 µm Paper - Run11: 50 µm BOPP
Comparison of the different carrier substrates with electrodes switched on:
Trials #08-11 (Run9): 12 µm PET
Trials #19-22 (Run12): 35 µm Paper from Starkraft
Trials #15-18 (Run11): 50 µm BOPP
-> misting influenced by surface tensions, insulation of substrates, etc

24. Conclusions
The electrostatic DC-plasma system by Eltex worked very efficiently :
On all tested substrates
With both tested silicon types
It can be used instead of any chemical antimisting additive
Worked as efficient in Thermic silicones
Worked better for the UV silicones
all three nips in 5 roll coater need an antimisting device, especially if high web speeds are targeted.
the deflection of misting by the DC-plasma system might be used where no chemical means are available
Two industrial implementations already in progress
Silicon coating and coating of a thin wax layer
Studies to explore the deeper understanding of all the variables would be welcome
Method, where chemical solution is not available (i.e. thin layer wax applied at 80°C)
For many other coatings the suppression of misting is not possible by chemical means and the aerosols are removed by suction systems.
However, this is a somewhat messy method and consumes a lot of energy.
Here the electrostatic suppression could offer a much more efficient solution.
There are still a lot of unknown variables -> studies welcome

25. Acknowledgements go to all participants of the tests:
Gilbert Gugler (iPrint, Fribourg, Switzerland; previously at Polytype),
Franz Knopf (Transferzentrum, Offenburg, Germany)
Eltex-Elektrostatik-GmbH (Weil am Rhein, Germany)
Bluestar Silicones (Saint Fons, France)
Techma Team at Polytype Converting AG

26. Electrostatic misting reduction
Questions?