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Journal of Coatings Technology and Research

, Volume 15, Issue 5, pp 899–911 | Cite as

Slot die stripe coating of low viscous fluids

  • Sebastian M. Raupp
  • Marcel Schmitt
  • Anna-Lena Walz
  • Ralf Diehm
  • Helga Hummel
  • Philip Scharfer
  • Wilhelm Schabel
Article
  • 227 Downloads

Abstract

Slot die coating is applied to deposit thin and homogenous films in roll-to-roll and sheet-to-sheet applications. The critical step in operation is to choose suitable process parameters within the process window. In this work, we investigate an upper limit for stripe coatings. This maximum film thickness is characterized by stripe merging which needs to be avoided in a stable process. It is shown that the upper limit reduces the process window for stripe coatings to a major extent. As a result, stripe coatings at large coating gaps and low viscosities are only possible for relatively thick films. Explaining the upper limit, a theory of balancing the side pressure in the gap region in the cross-web direction has been developed.

Keywords

Slot die coating Stripe coating Process window Minimum film thickness Upper limit Low viscous liquids Model for film spreading 

Letters

CF

Correction factor

ETOH

Ethanol

h

Height (z-axis) (µm)

l

Length (x-axis) (mm)

n

Power law exponent

p

Pressure (mbar)

PAA

Polyacrylamide

q

Specific volume flow (m2/min)

t

Time (s)

u

Speed (m/min)

w

Width (y-axis) (mm)

x

x-axis in web direction

y

y-axis in cross-web direction

Greek letters

\(\dot{\gamma }\)

Shear rate (1/s)

\(\eta\)

Newtonian viscosity (Pa s)

\(\theta\)

Static contact angle (°)

\(\vartheta\)

Dynamic contact angle (°)

\(\kappa\)

Consistency factor (Pa sε)

\(\sigma\)

Surface tension (mN/m)

Indices

approx.

Approximated

Bead

Bead

Ca

Capillary number

Cap

Capillary

crit

Critical

D

Downstream

G

Gap

Fluid

Fluid

max

Maximum

min

Minimum

s

Slot

Side

Side

solid

Solid

spacer

Spacer

spread

Spread

U

Upstream

Vac

Vacuum

w

Web

wet

Wet

1

Position 1

2

Position 2

3

Position 3

Notes

Acknowledgments

The authors acknowledge financial support via the projects KOBALT and POESIE of the German Federal Ministry of Education and Research (Contract Nos. 13N0883 and 13N13692) and Philips Technologie GmbH Innovative Technologies, Aachen. We would like to thank all involved mechanics, assistants, and students for contributing to this work as well as TSE Troller AG, Murgenthal, Switzerland, for technical support.

Supplementary material

11998_2017_39_MOESM1_ESM.pdf (2.4 mb)
Supplementary material 1 (PDF 2459 kb)

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Copyright information

© American Coatings Association 2018

Authors and Affiliations

  • Sebastian M. Raupp
    • 1
    • 3
  • Marcel Schmitt
    • 1
  • Anna-Lena Walz
    • 1
  • Ralf Diehm
    • 1
    • 3
  • Helga Hummel
    • 2
  • Philip Scharfer
    • 1
    • 3
  • Wilhelm Schabel
    • 1
  1. 1.Institute of Thermal Process Engineering, Thin Film Technology, Karlsruhe Institute of TechnologyKarlsruheGermany
  2. 2.Chemistry and Biotechnology, University of Applied Sciences, FH AachenJülichGermany
  3. 3.InnovationLabHeidelbergGermany

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