Premetered Coating Methods: Attractiveness and Limitations

Preface
Motivation for and Purpose of this Book
Outline of the Book
Past, Present, and Future of Premetered Coating Methods
Acknowledgements
Contents
About the Author
Definition of Symbols
Letters
Dimensionless Numbers
Greek Letters
Part I R&D in Premetered Coating Technology
1 Introduction
1.1 History of R&D in Coating Technology
1.2 History of Dissemination of Knowledge in Coating Technology
References
2 Premetered Versus Selfmetered Coating Methods
2.1 Premetered Coating Methods
2.2 Selfmetered Coating Methods
2.3 Process Limitations
2.4 Attractiveness of Premetered Coating Methods
References
3 Mass Balance and Flow Rates
3.1 Wet Versus Dry Film Thickness
3.2 Flow Rates
3.3 Correlations Between Volume-Based and Mass-Based Parameters
3.3.1 Units
3.3.2 Correlations Based on Dry Coat Weight Adry
3.3.3 Correlations Based on Dry Film Thickness Hdry
3.3.4 Correlations Based on Porous Film Thickness Hporous
3.3.5 Operating Requirements for the Flow Rate
3.3.6 Maximum Web Speed Resulting from Drying Limitation
References
4 Physical Fluid Properties
4.1 Introduction
4.2 Solids Concentration
4.2.1 Solids Concentration by Volume
4.2.2 Solids Concentration by Weight
4.2.3 Measuring the Solids Concentration by Weight
4.3 Densities
4.3.1 Liquid Density Based on Concentration by Volume
4.3.2 Liquid Density Based on Concentration by Mass
4.3.3 Solid Density
4.4 Rheological Properties
4.4.1 Shear Viscosity
4.4.2 Shear Rate Ranges of Coating Flows
4.4.3 Measurement Devices
4.4.4 Rheological Models
4.4.5 Concentration Dependence of Viscosity
4.4.6 Temperature Dependence of Viscosity
4.4.7 Viscoelastic Properties
4.5 Surface Tension
4.5.1 Surface Tension of Coating Fluids
4.5.2 Static or Dynamic Surface Tension
4.5.3 Methods for Measuring Surface Tension
4.5.4 Requirements for Surfactants
4.5.5 Selection of Surfactants
4.6 Contact Angle and Wetting
4.6.1 Static Contact Angle and Spreading Coefficient
4.6.2 Measurement of the Contact Angle
4.6.3 Wettability of Substrates
4.6.4 Wetting Envelope
References
5 Basic Flows of Premetered Coating Methods
5.1 Introduction
5.2 Vortices in Coating Flows
5.3 Strategies for Solving Fluid Flow Problems
5.4 Pipe Flow
5.4.1 Constant Viscosity (Newtonian Flow Behavior)
5.4.2 Shear Rate Dependent Viscosity (Shear Thinning Flow Behavior)
5.4.3 Comparison of Flow Models for Solving Pipe Flow Problems
5.4.4 Vortices in Pipe Flow
5.5 Duct Flow
5.5.1 Flow Along the Axis of Ducts
5.5.2 Flow Across Ducts
5.6 Slot Flow
5.6.1 Constant Viscosity (Newtonian Flow Behavior)
5.6.2 Shear Rate Dependent Viscosity (Shear Thinning Flow Behavior)
5.6.3 Two-Layer Slot Flow (Newtonian Flow Behavior with Carreau-Yasuda Viscosity)
5.6.4 Vortices in Slot Flow
5.7 Film Flow
5.7.1 Single-Layer Film Flow for Constant Viscosity (Newtonian Flow Behavior)
5.7.2 Single-Layer Film Flow for Shear-Dependent Viscosity (Power Law Flow Behavior)
5.7.3 Multilayer Film Flow for Constant Viscosity (Newtonian Flow Behavior)
5.7.4 Waves in Film Flow
5.7.5 Standing Waves in Film Flow
5.7.6 Surface Age of Film Flow
5.7.7 Minimum Flow Rate for Film Flow
5.7.8 Vortices in Film Flow
5.8 Curtain Flow
5.8.1 Curtain Velocity
5.8.2 Extension Rate in Curtain Flow
5.8.3 Curtain Fall Time
5.8.4 Curtain Thickness
5.8.5 Curtain Stability
5.8.6 Curtain Deflection
5.8.7 Vortices in Curtain Flow
5.8.8 Neck-in in Curtain Flow
5.9 Boundary Layer Flow
5.9.1 Concept for Reducing the Boundary Layer Thickness
5.9.2 Boundary Layer in Slot Flow
5.9.3 Boundary Layer in Film Flow
5.9.4 Boundary Layer in Curtain Flow
5.9.5 Curtain Edge Guides
5.9.6 Boundary Layer in Impinging Flow
5.9.7 Vortices in Impinging Flow
5.10 Flow After Coating
5.10.1 Conformity of the Coated Film
5.10.2 Web Path Between Coating and Solidifying
5.10.3 Leveling
5.10.4 Flow Due to Ambient Disturbances
5.10.5 Edge Withdrawal
References
6 Wall Shear Stress
6.1 Introduction
6.2 Cleaning and Contamination
6.3 Wall Shear Stress and Die Design
6.3.1 Wall Shear Stress in the Inner Cavity
6.3.2 Wall Shear Stress in the Outer Cavity
6.4 Effect of Variable Coating Width on Wall Shear Stress Distribution
6.5 Wall Shear Stress and Fluids with a Yield Stress
6.6 Wall Shear Stress and Residence Time
6.6.1 Mean Residence Time
6.6.2 Mean Residence Time Distribution of a Slot Die
6.6.3 Residence Time Spectrum
6.6.4 Transfer Function
6.6.5 Change-Over Time
6.7 Wall Shear Stress and Reactive Fluids
References
7 Dynamic Wetting and Hydrodynamic Assist
7.1 Introduction
7.2 The Concept of Hydrodynamic Assist
7.3 Process Optimization
References
Part II General Properties of Premetered Coating Methods
8 Preparing, Conditioning, and Delivering Coating Fluids
8.1 Introduction
8.2 Elements of the Fluid Conditioning and Delivery System
8.2.1 Preparation Vessel
8.2.2 Coating Vessel
8.2.3 Degassing
8.2.4 Pump
8.2.5 Flow Meter
8.2.6 Filter
8.2.7 Temperature Control
8.2.8 In-Line Mixing
8.2.9 In-Line Fluid Change
8.2.10 Pulsation Dampener
8.2.11 Pipe Line
8.2.12 T-Junction
8.2.13 Valves and Fittings
8.2.14 5-Way Valve and Recirculation Loop
8.2.15 Die
8.2.16 Cleaning-In-Place (CIP)
References
9 Film Thickness and Film Thickness Uniformity
9.1 Introduction
9.2 Nominal Film Thickness
9.3 Film Thickness Uniformity in Machine Direction
9.4 Die Design (Film Thickness Uniformity in Cross-Web Direction)
9.4.1 Concepts for Liquid Distribution
9.4.2 Film Thickness Nonuniformity
9.4.3 Recent Literature on Die Design
9.4.4 Die Geometry
9.4.5 Modeling Die Performance
9.4.6 Bar Deflection
9.4.7 Die Design Procedure
9.4.8 Analyzing Die Performance
9.4.9 Optimization of Die Design
References
10 Concepts for Varying the Coating Width
10.1 Introduction
10.2 Width Change for Slide Dies
10.3 Width Change for Slot Dies
Reference
11 Splice Passage and Coatability
11.1 Introduction
11.2 Types of Splices
11.3 Splice Passage
11.4 Splice Coatability
12 Simultaneous Multilayer Coating Capability
12.1 Introduction
12.2 Examples of Multilayer Products
References
13 Mixing of Adjacent Layers
13.1 Mixing Due to Convection
13.2 Mixing Due to Diffusion
References
14 Guidelines for Designing Single-Layer and Multilayer Films
14.1 Introduction
14.2 Guidelines for Single-layer Films
14.2.1 Viscosity
14.2.2 Surface Tension
14.3 Guidelines for Multilayer Films
14.3.1 Density Structuring
14.3.2 Viscosity Structuring
14.3.3 Surface Tension Structuring
14.3.4 Surface Tension Structuring for Multilayer Curtains
References
15 Modeling Economic Aspects of Coating Methods
15.1 Introduction
15.2 Effect of the Coating Speed and the Size of the Coating Lot on the Specific Machine Utilization
15.3 Effect of the Lot Size and the Non-productive Time on the Specific Machine Utilization
15.4 Cost Savings from Reduced Coating Passes
15.5 Cost Savings from Improved Coat Weight Uniformity
Reference
Part III Specific Properties of Premetered Coating Methods
16 The Concept of the Coating Window
16.1 Introduction
16.2 Coating Windows for Premetered Coating Methods
References
17 Specific Properties of Slot Coating
17.1 Introduction
17.2 Process Configuration and Equipment
17.3 Geometry of the Coating Bead
17.4 Operating Window
17.5 Low Flow Limit
17.6 Implications of the Low Flow Limit
17.7 The Pressure Profile in the Coating Bead
17.8 Coating Defects
17.8.1 Ribbing Lines
17.8.2 Air Entrainment
17.8.3 Vortices
17.8.4 Heavy Edges
17.8.5 Effect of the Uniformity of the Coating Gap on the Uniformity of the Wet Film Thickness
17.9 Process Optimization
17.9.1 Optimizing the Viscous Operating Mode
17.9.2 Optimizing the Capillary Operating Mode
17.10 Operational Aspects
17.10.1 Coating Start
17.10.2 Coating Stop
17.10.3 Cleaning the Die and Changing the Coating Fluid
17.10.4 Changing the Coating Width
17.10.5 Splice Passage
17.10.6 Prevention of Lines and Streaks
17.11 Tensioned-Web Coating
17.12 Double-Sided Coating
17.13 Stripe Coating
17.14 Intermittent Coating
17.14.1 Trailing Edge
17.14.2 Leading Edge
17.15 Pattern Coating
17.16 Simultaneous Multilayer Coating
References
18 Specific Properties of Slide Coating
18.1 Introduction
18.2 Process Configuration and Equipment
18.3 Flow Field of the Coating Bead
18.4 Operating Window
18.5 Coating Defects
18.5.1 Ribbing Lines
18.5.2 Air Entrainment
18.5.3 Vortices
18.6 Process Optimization
References
19 Specific Properties of Curtain Coating
19.1 Introduction
19.2 Process Configuration and Equipment
19.2.1 Web Path
19.2.2 Design of Coating Station
19.2.3 Slide or Slot Die
19.2.4 Suction Baffle
19.2.5 Operating Modes
19.2.6 Coating Start and Stop
19.3 Operating Window
19.3.1 Operating Window for Long Curtains
19.3.2 Operating Window for Short Curtains
19.4 Process Optimization
References
Index