comparison of coating techniques gravure roll (contact) vs. … · 2018-10-08 · page 1 - jens...

- Jens Vollpott, KROENERT Hamburg - AIMCAL Web Coating Conference, Prague 2012

Comparison of Coating Techniques Gravure Roll (Contact)

vs. Curtain (Non-contact)

Presented by: Jens Vollpott Area Sales Manager KROENERT GmbH & Co KG Schützenstraße 105, D-22761 Hamburg, www.kroenert.de


Structure

• Introduction

• The Kroenert Group

• Coating Techniques – Overview

• Gravure techniques, principle (contact)

• Curtain technique, principle (non contact)

• Coating Techniques - Limits

• Comparison gravure vs. curtain

• Conclusions


Bachofen + Meier Bülach, CH

KROENERT Hamburg, GER

DRYTEC Norderstedt, GER

The KROENERT Group


Typical products


Auxiliary unwinding (wet laminating)

Curtain- Coater

Multi-Coater equipment with changeover

Online Thickness Measurement

UV-system

Corona Web cleaner

Unwinder Winder

Convective drying channel (18 m)

Online moisture measuring

Laminate unwinding Auxiliary rewinding

Lamination station

steam moisturizer

WEKO moisturizer

Auxiliary unwinding (re-laminating)

steam moisturizer

Coating Techniques - Overview


Coating Techniques - Overview Pre-metering

systems

Contact systems Non-contact systems

Screen roller coating •pan or open chamber

Screen roller coating • closed and pressurized

chamber

Die coatings

Curtain Coating •Slot die •Slide die

Scatter coating Powder coating Air knife

Vaporize Plasma coating Spray coating

•Die coatings

Self-metering systems

Contact systems Non-contact systems

3 - rollers

4 - rollers

5 - rollers

6 - rollers

Metering nip

Dip coating

Special solutions

Blade coating

Special solutions

Curtain Coating •Slot die •Slide die

•Screen roller coating •pan or open chamber

•Screen roller coating •closed and pressurized chamber


Gravure techniques, principle (contact)

Conventional gravure T-type chamber Pressurized chamber MPG 600 CI

With pan feeding and oscillating doctor blade in positive position.

Direct and reverse coatings are possible

Closed chamber system without pan, metering blade in negative position.


Closed chamber, pressure controlled without pan, metering blade in negative position (positive possible).


Large variability in coat weight with just one screen roller


Pressurized Chamber MPG 600

Conventional gravure

Gravure Coating

Gravure techniques, principles (contact)


Curtain technique, principle (non contact) 1-Layer Slot-Die 3-Layer Slide-Die

Just one coating station for multiple functional coats (e.g. peelable labels, solvent-based varnish undercoats and top coats)

Reduced raw material costs (e.g., multilayer structure, improved barrier properties due to multiple, but thinner layers)

Greater range of application weights through opening and closing of slots

Improved adhesion between layers

More-compact coating systems — lower investments (fewer coating stations and dryer sections)

Non-contact coating (no contact with the substrate web)

High coating speeds

No compound circulation and recirculation

Contour coats with application weight tolerances of up to ≤ 1%

Low wear, low maintenance (no rolls, blades, etc.)

Short cleaning times


3-Layer Slide-Die

1-Layer Slot-Die

Curtain Coating

Curtain technique, principle (non contact)


Coating Techniques –Limits by coat weight

500 1000 1500 Speed [m/min]

1

10

100

200

Coat Weight [gsm]

Standard Coating Systems Coat weight / Speed

Metering nip (Comma)

Screen rollers (Blade)

4-Rollers

5-Rollers

6-Rollers

Curtain

Die


Curtain


Coating Techniques – Limits by viscosity

Metering nip (Comma)


Rollers (4, 5 and 6)

Curtain

Die

500 1000 1500 Speed [m/min]

500

1000

5000

10000

Viscosity [mPa s]

100

Standard Coating Systems Viscosity / Speed


Curtain


Comparison gravure vs. curtain

MPG 600 Ci Multi Pressure Gravure 600 Chamber Injection

Curtain Coating

SWC Single Wet Curtain

MWC Multi Wet Curtain

max. working speed up to now: a) production machines b) R+D machines

1.100 m/min 1.200 m/min

1.200 m/min 1.600 m/min

1.100 m/min 1.500 m/min

Min. working speed for stable operation

< 20 m/min To be determined per product through test runs; experiences with acrylate adhesives

40 gsm wet app. 150 m/min 6 gsm wet app. 1.000 m/min

Online Coat weight measurement unit

Not necessary; only flow indicator is recommended.

Not necessary; only a flow indicator is recommended.




Curtain Coating



Coat weight range (depending on coat weight and product)

wet 1 – 120 gsm wet 1 – 150 gsm wet 1 – 150 gsm

Viscosity (at shear rate >1.000 i/s)

10 – 1.200 mPas 100 –300 mPas

Influence of unstable viscosity Compounds with intrinsic viscosity to be used,

operation viscosity should be nearly constant

The operation viscosity should not deviate more than ±30 % from the average viscosity




Curtain Coating



Surface tension Adaption of materials is possible

< 30 mN/m dynamic

Coat weight tolerances in lenght and cross profile

± 3% 1 – 3% for curtain die depending on required quality

grade

Contact / non contact coating to substrates

Contact Non contact gentle operation for compounds and

substrates




Curtain Coating



Compound circulation and recirculation

Yes No, or only a small return of coating liquid

Filtering of compounds Is recommended but not a requirement

Without filtering there is a risk for streaks on the coated web and the curtain breaks down

Influence of air into compounds Compounds should be bubble free

Compounds have to be bubble free




Curtain Coating



Coat weight variance Variation without changing screen roller just by pump

pressure adjustment

Control of flow rate by pump pressure variance

Web-width adjustment Change of sleeve type backing roller

Manual or motorized adjustment of edge units

Quality of rubber covered breaking roller

Roundness tolerance of rubber backing roll

≤ 8 – 10 µm

None




Curtain Coating



Influence of air boundary layer on substrates

None Large, if speed exceeds 250 m/min; vacuum units are required

Change time for exchange of compound

With cleaning 30 – 40 min; With second circulation

system < 15 min

With cleaning > 60 min; With second circulation system and if a new

compound does not contaminate with the used slurry < 15 min

Flexibility for small order lots Wide Limited




Curtain Coating



Requirements for wear parts Larger (sleeves, blades)

Very less

References (KROENERT group) 140 pieces in operation for different applications.

Actual development, app. 14 pieces supplied

Price level differences for coating system including required auxiliary equipment

100 % 150 % >200 %


Conclusions • Both coating systems – gravure and curtain – have their needs • Both coating systems – gravure and curtain – have their limits • Gravure system covers a wide range in coat weight and

viscosity • Curtain coating is limited in lower coat weights at lower speeds

and in viscosity, but it is capable for higher speeds • Curtain coating needs adaptation in surface tension of

compound • Curtain coating needs higher investment cost but less wear

parts • Curtain coating treat the materials much more gentle • Curtain coating reduces raw material costs • Gravure coating is preferable for short order runs • Curtain coating is preferable for commodities and for

multilayer functional coatings


“Thank You for your attention”

PRESENTED BY Jens Vollpott Regional Sales Manager KROENERT GmbH & Co KG Schützenstraße 105, D-22761 Hamburg, www.kroenert.de

All photos and grafics by KROENERT

comparison of coating techniques gravure roll (contact) vs. … · 2018-10-08 · page 1 - jens...

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