Coating and Drying Defects: Troubleshooting Operating Problems (Society of Plastics Engineers Monographs)

COATING AND DRYING DEFECTS......Page 3
CONTENTS......Page 9
Preface......Page 17
Preface to the First Edition......Page 19
About the Authors......Page 23
1 Introduction......Page 25
2 Troubleshooting or Problem-Solving Procedure......Page 29
Basic Troubleshooting Principles......Page 30
Detect the Defect......Page 32
Define the Defect or Problem......Page 33
Name the Defect......Page 35
Problem Statement......Page 39
Process Information......Page 40
General Process Information......Page 41
Analyze the Data and Identify Potential Causes of Problem......Page 43
Document the Results......Page 49
References......Page 51
3 Coater and Defect Analytical Tools......Page 53
Analytical Methods to Characterize Defects......Page 54
Video Enhanced Microscopy......Page 55
Surface Characterization Techniques......Page 57
Coater Characterization Instruments......Page 62
Data Loggers......Page 66
Rheological Measurements......Page 68
Surface Properties......Page 73
On-Line Inspection Systems......Page 74
On-Line Coating Weight Measurement......Page 76
On-Line Viscosity......Page 78
Data Analysis Techniques......Page 79
Keeping Current......Page 80
References......Page 85
Dirt and Other Particulates......Page 87
Filtration......Page 88
Agglomerates......Page 90
Bubbles......Page 92
Poor Cross-Web Uniformity......Page 93
Feeding the Coating Liquid......Page 94
Magnetic Flow Meters......Page 96
Coriolis Meters......Page 97
References......Page 98
Coating Methods......Page 99
Control of Coating Weight......Page 106
Ribbing......Page 110
Ribbing in Forward Roll Coating......Page 111
Ribbing and Cascade (or Herringbone or Seashore) in Reverse Roll Coating......Page 113
Streaks and Bands in Roll Coating......Page 116
Sagging......Page 118
References......Page 119
Description of Coating Methods......Page 121
The Window of Coatability......Page 131
Slide Coating......Page 133
Vortices and Eddies......Page 134
Slot Coating......Page 141
Extrusion Coating......Page 148
Curtain Coating......Page 150
Effect of Surface Roughness on the Limits of Coatability......Page 152
Ribbing......Page 155
Edge Beads and Heavy Edges......Page 157
Waves in Slide and in Curtain Coating......Page 159
Streaks and Bands in Premetered Coating......Page 161
References......Page 165
Cross-Web Uniformity......Page 167
Temperature Control......Page 172
Corrections to the Coating Die Internals......Page 173
Die Internal Pressures and Spreading......Page 174
Extrusion Dies......Page 175
Wall Shear Stress Control and Residence Time Control......Page 177
References......Page 179
8 Surface Tension Driven Defects......Page 181
Surfactants......Page 182
Surface Tension Effects in Coating......Page 183
Convection or Bénard Cells......Page 186
Craters......Page 187
Fat Edges or Picture Framing......Page 188
Nonuniform Edges in Multilayer Coatings......Page 189
Dewetting and Crawling......Page 190
Adhesive Failure and Delamination......Page 191
References......Page 192
9 Problems Associated with Static Electricity......Page 193
Formation of Charges......Page 195
Electrostatic Fields......Page 197
Surface Resistivity......Page 198
Measurement of Static Charges......Page 201
Free Charges......Page 204
Bound Charges......Page 206
References......Page 207
10 Problems Associated with Drying......Page 209
Dryer Control and Solvent Removal......Page 213
Drying Condition Case History......Page 219
Drying Defects......Page 222
Blushing......Page 223
Bubbles and Blisters......Page 224
Curl......Page 225
Delamination......Page 228
Dryer Bands......Page 229
Dryer Remelt......Page 230
Dryer Contamination Spots......Page 231
Mottle......Page 232
Reticulation......Page 233
Starry Night......Page 235
The Role of Dryer Simulation in Troubleshooting......Page 236
The Role of Radiative Heating in Defect Reduction......Page 238
References......Page 239
11 Problems Associated with Web Handling......Page 241
Web......Page 242
Base Web Defects that Cause Wrinkling......Page 243
Web Camber......Page 245
Web Cross-Machine Thickness Profile Variation......Page 247
Surface of the Web......Page 249
Plastic Web......Page 251
Web Transport Systems......Page 252
Tension......Page 254
Unwind Stand......Page 255
When to Use Drive Motors on an Unwind Stand......Page 257
Web Control......Page 258
Web Slippage and What Slip Affects......Page 259
Nip Rolls......Page 260
Unnipped Rolls (Elastomer Rolls)......Page 261
Suction Rolls......Page 265
Suction Aprons or Tables......Page 266
Tension Isolation......Page 267
Differential Tension......Page 268
Driving Web-Carrying Rolls Within a Dryer......Page 269
Use of Accumulators at the Rewind and Unwind......Page 270
Surface/Center Rewinds......Page 271
Drives for Laminators......Page 272
Coating Defects—Sources and Some Solutions......Page 273
Backlash Exists in Timing Belts, Gearboxes, and Geared Couplings......Page 274
Roll Unbalance......Page 275
Coating Roll Drive Systems......Page 276
Transmission of Vibration Through Structural Members to the Coating Stand......Page 278
Troubleshooting "Sudden" Coating Problems......Page 279
Monitoring the Speed of Idler Rolls......Page 281
Tension Monitoring Systems......Page 282
Why Is Tension Control Needed?......Page 283
Effects of Wiring Practices on Tension Control......Page 284
When Do You Use a Pure Speed Control?......Page 285
Equipment Lists Avoid Problems and Help Plant Personnel......Page 288
Frequency and Direction of a Speed Perturbation......Page 289
Types of Tension Control Systems......Page 290
Dancer Roll Control......Page 292
Using Air Roll Air Gap Control as a Dancer in the Dryer......Page 294
Force Transducer Control......Page 296
Master or Lead Section......Page 298
Sections with Limited Ability to Control Web Transport or Tension......Page 299
Dealing with Sections that Have Limited Ability to Control Tension......Page 300
Sections that Always Slip or Almost Always Slip......Page 301
Machine Alignment: Avoiding Many Web Handling Problems......Page 302
Alignment Problems Due to Building Location in a Swamp or Tidal River......Page 303
The Alignment Process......Page 304
The Baseline......Page 305
Checking the Alignment of a Size Press (Roll Coater) on a Paper Web......Page 306
Knowing How Your Machine Operates Can Avoid Problems in the Future......Page 307
References and Bibliography......Page 308
Introduction......Page 311
Definitions......Page 312
Mechanical Chatter......Page 315
Serpentine Chatter......Page 316
Contamination Spots......Page 318
Scratches......Page 319
Mottle......Page 320
Air Bar Rubs in a Floater Dryer......Page 321
Selection of Equipment......Page 322
Need for Coating Defects Database......Page 323
Defects Database: Examples......Page 326
Bubbles......Page 327
Need for Lexicon......Page 330
Glossary......Page 332
Troubleshooting Guide......Page 333
Search Capability......Page 334
Availability......Page 336
References......Page 338
Introduction......Page 339
Define Product and Process Requirements......Page 340
Ensure Web Coating Process Meets Specifications......Page 343
Use Appropriate Coating Method......Page 344
Quantify and Understand Defect Losses......Page 345
Use Computer Database to Store and Share Information......Page 349
Use Statistical Process Control......Page 351
Develop Fundamental Process Understanding......Page 352
Index......Page 355