Electrostatic Reduction of Misting in Roll CoatingUV: Effect of misting from second nip (W0 / W1 ) - Run8: nip unmasked - Run9: nip masked 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0 100 200 300

Electrostatic Reduction of Misting in Roll CoatingBill Smith

Polytype Converting GmbH

AIMCAL R2R Conference USA 2018Phoenix, Arizona,

October 28-31, 2018

AIMCAL R2R Conference USA 2018, Phoenix, Arizona, October 28-31, 2018

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Agenda

Electrostatic Reduction of Misting in Roll Coating

• Introduction• Experimental• Results• Conclusions


Introduction

Misting from film splitting

• Liquid passing through a nip• Development of droplets upon splitting• High splitting speed• Particle size << 50 μm• Health, quality, cleanup, and cost issue.


Introduction

Misting from film splitting

Extended ribs break up

Michel S. Owens 2004

Ribbing lines in forward roll coating

Dontula 1996


W3

W2

W1

W0W00

Introduction

Current options for handling the misting (example: silicone coater)• Chemical anti-misting additives• Mist particle evacuation

5-roll coater: F. Krebs and P. M. Schweizer, Coating 2005 6 , p214-217 and Coating 2005 7, p268-270

5 roll coater


Introduction

Novel electrostatic approach from Eltex: Misting Tacker

F. Knopf, Eltex Elektrostatik GmbH, WO2014030077(A2), DE102012207148A1


Introduction: Misting Tacker

Low Energy DC–Plasma Electrode

DC-Plasma Deposition Unitview into a cross-section

Electrode Tip

Counter Electrode

Plasma Cone

ca.10 mm


Introduction

Misting Tacker: Low Energy DC–Plasma Electrode

deflection instead of suppression

airstreamplasma cone(ionization)


Experimental

Raw MaterialsSilicones 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


Experimental

5 roll silicon coater and electrode placement


Experimental

Techma coater – web upstream view (backside)

W3

W2

W1


Experimental – Data Collection

Measurement around Application Unit – Electrodes off(600m/min)

0

20

40

60

80

100

120

140

160

11:08:30 11:09:00 11:09:30 11:10:00 11:10:30 11:11:00 11:11:30

Part

icle

Conc

entra

tion [

mg/

m3]

Total Concentration of Particles PM1, PM2.5, and PM10

Nip W2/3 Nip W1/2 side AS

(max. >150 mg/m3)



Measurement around Application Unit – Electrodes on(600m/min)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

11:40:00 11:40:30 11:41:00 11:41:30 11:42:00 11:42:30 11:43:00

Part

icle

Con

cent

ratio

n [m

g/m

3]

Total Concentration of Particles PM1, PM2.5, and PM10

(max scale of graph: 1.8 mg/m3)



Aerosol sensor placed at fixed point between roll W2 and W3


Results – Data Collection

Measurement of Aerosols at fixed pointstep by step increase of web speed up to 1000 m/min

0

5

10

15

20

25

30

35

13:19:00 13:20:00 13:21:00 13:22:00 13:23:00 13:24:00 13:25:00 13:26:00 13:27:00

Tota

l con

c of p

artic

les (

mg/

m3)

POLY368-XL325-CATA11091M-MG KRAFT-STARKRAFT--300-600-800-900-1000 m/min

Masking Nip W0/W1Nip below aerosol sensor covered

100 m/min

300 m/min600 m/min

800 m/min

1000 m/min

0

5

10

15

20

25

30

35

00:00:00 00:01:00 00:02:00 00:03:00 00:04:00 00:05:00 00:06:00 00:07:00 00:08:00 00:09:00 00:10:00

Silic

one

part

icle

s (m

g/m

3)

Total Particle Concentration -- 100-300-600-800-1000 m/min(max scale of graphs: 35 mg/m3)


Results – Data Collection

UV: Effect of misting from second nip (W0 / W1)- Run8: nip unmasked- Run9: nip masked

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600

Silic

one m

ist (

mg/

m3)

Machine speed (m/min)

Impact W0-W1 masking (PET-EB)

Run8-no masking Run9-with masking

Web speed W1 speed

300 m/min 210 m/min

400 m/min 280 m/min

500 m/min 350 m/min


Results – Thermic Silicone

Comparison of electrostatic to chemical method- Run2: no measure- Run6: chemical additive- Run5: electrostatic DC-Plasma

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200

Silic

one m

ist (

mg/

m3)


Method Influence Overview (Thermic)

Run2-none Run6-Additive Run5-DC-Plasma



Comparison of electrostatic to chemical method- Run5: electrostatic DC-Plasma- Run6: chemical additive

0

5

10

15

20

25

0 200 400 600 800 1000 1200

Silic

one m

ist (

mg/

m3)


Electrostatic vs Chemical Method (Thermic)

Run5-DC-Plasma Run6-Additive



Comparison of effect by different substrates- Run5: 35 µm Paper- Run7: 12 µm PET

0

5

10

15

20

25

0 200 400 600 800 1000 1200

Silic

one m

ist (

mg/

m3)


Comparison of Substrates (Thermic)

Run5-MGKraft Run7-PET


Results – UV Silicone

Comparison of electrostatic to chemical method- Run12: electrostatic DC-Plasma- Run13: chemical additive- Run10: no measures taken

0

5

10

15

20

25

30

35

40

0 100 200 300 400 500 600

Silic

one m

ist (

mg/

m3)


Method Influence Overview (UV)

Run12-DC Plasma Run13-Additive Run 10-none



Comparison of electrostatic to chemical method- Run12: electrostatic DC-Plasma- Run13: chemical additive

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600

Silic

one m

ist (

mg/

m3)


Electrostatic vs Chemical Method (UV)

Run12-DC Plasma Run13-Additive



Comparison of effect by different substrates- Run9: 12 µm PET- Run12: 35 µm Paper- Run11: 50 µm BOPP

0.000.050.100.150.200.250.300.350.400.45

0 100 200 300 400 500 600

Silic

one m

ist (

mg/

m3)


Comparison of Substrates (UV)

Run9-PET Run12-MGKraft Run11-BOPP


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


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


Electrostatic misting reduction

Questions?

Documents

Electrostatic Reduction of Misting in Roll CoatingUV: Effect of misting from second nip (W0 / W1 ) - Run8: nip unmasked - Run9: nip masked 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0 100 200 300