Extrusion Coating, Lamination and Coextrusion The complete process manual B.H. Gregory First edition 2012 P las tics NFORMATION^ A division of Applied Market Information Ltd. AMI House, 45-47 Stokes Croft, Bristol BS1 3QP, United Kingdom www.pidbooks.com
Contents Introduction 1 Chapter 1 The extrusion coating process 5 1.1 Chill roll cooling section 8 1.2 Chill roll surfaces 15 1.3 Pressure roll 17 1.4 Web tension control 19 1.5 Winders and splicing 20 1.6 Stretching flows and neck-in 24 1.7 Draw resonance 31 Chapter 2 Extrusion coated products 33 2.1 Paper/aluminium/polyethylene structures 35 2.2 Triplex coating lines for aseptic packaging 36 2.3 Photographic paper coating 38 2.4 Laminates for toothpaste tubes 39 2.5 Barrier coatings and laminations 40 2.6 Extrusion coating PP on aluminium foil 42 Chapter 3 Extruder and screw design 44 3.1 Basic extruder functions 46 3.2 Origins of extruder output pulsations 48 3.3 Optimizing screw design 52 3.4 Barrier screws 61 3.5 Sizing extruders 64 3.6 Polyester (PET) extrusion 66 3.7 Ethylene-vinyl alcohol extrusion 68 Chapter 4 Die design 71 4.1 Automatic dies 76 4.2 Flat die computer simulations 77 4.3 Design modification oft slot die 78 4.4 T slot die and other polymers 82 Hi
Extrusion Coating, Lamination and Coextrusion: The complete process manual 4.5 Coat hanger die 86 4.6 Comparative die performance 88 Chapter 5 Adhesion in extrusion coating 91 5.1 Effect of polyethylene additives on adhesion 93 5.2 Chill roll cooling and coating weight 94 5.3 Effect of melt temperature on adhesion 97 5.4 Time in air gap 100 5.5 Temperature drop in the air gap 103 5.6 Elongational stress and melt relaxation 105 5.7 Screw speed and residence time 108 Chapter 6 Adhesion promotion methods 112 6.1 Corona treatment 113 6.2 High density atmospheric plasma 115 6.3 Ozone treatment 116 6.4 Flame treatment 121 6.5 Chemical priming 124 6.5.1 Aqueous primers 126 6.5.2 Solvent based primers 128 Chapter 7 The adhesive lamination process 129 7.1 Adhesives 133 7.2 Solvent-free adhesives 137 7.3 Product resistance 140 7.4 The anti-sealing effect in laminates 143 Chapter 8 Polyethylene lamination films 146 8.1 Tubular film production 146 8.2 Corona treatment of lamination film 156 8.3 Heat seal behaviour 159 8.4 Hot tack 161 8.5 Additive migration to surfaces 163 8.6 Surface contamination 163 8.7 Peelable seal film and coatings 166 8.8 Scalping 168 iv
Contents Chapter 9 Coextrusion processes 172 9.1 Flat die coextrusion options 172 9.2 Typical coextrusion problems 174 9.3 Layer rearrangement 175 9.4 Coextrusion profiling 177 9.5 Interfacial instabilities 180 9.6 Computer simulations 182 9.7 Some methods to minimize interfacial shear stress 186 9.8 Flow dividers 189 9.9 Heat transfer inside a coextrusion die 190 9.10 Coextrusion with dual manifold dies 192 9.11 Coextrusion coating with ethylene copolymers 194 9.12 Some coextruded structures 198 9.13 Tubular film coextrusion 199 Chapter 10 Coextrusion tie-resins 203 Chapter 11 Substrates and films 209 11.1 Adhesion of cellulose/paper materials to PE 210 11.2 Paper and paperboard 210 11.3 Aluminium foil 213 11.4 Flexible packaging films 216 11.5 Regenerated cellulose film (RCF) 216 11.6 Oriented polypropylene film (BOPP) 217 11.7 Oriented polyester film (OPET) 219 11.8 Polyamide film (nylon) 220 11.9 HDPE coextrusions 222 11.10 Metallized films 222 11.11 Oxide (ceramic) coated films 224 Chapter 12 Multilayered film applications 227 12.1 Calculating film stiffness 229 12.2 Form, fill and seal packaging (FFS) 231 12.3 Aseptic packaging 236 12.4 Bag-in-box (BIB) laminates 237 v
Extrusion Coating, Lamination and Coextrusion: The complete process manual 12.5 Dry food (cereal) packaging 239 12.6 Snack foods 240 12.7 Films for coffee packaging 241 12.8 Frozen food films (retail) 244 12.9 Liquid pouches 247 12.10Modified atmosphere packaging (MAP) 249 Chapter 13 Polyethylene materials and processes 255 13.1 Low density polyethylene 257 13.2 High pressure ethylene copolymers 260 13.2.1 Ethylene-vinyl acetate copolymer (EVA) 262 13.2.2 Ethylene-alkyl ester copolymers (EAE) 263 13.2.3 Ethylene-acid copolymers 264 13.2.4 Ionomers 267 13.3 Linear low density polyethylene (LLDPE) 269 13.4 Melt viscosity of LD/LLDPE...274 13.5 High density polyethylene (HDPE) 276 13.6 Polyolefin blends for extrusion coating 283 13.7 Metallocene-catalyzed PE 286 Chapter 14 Barrier and other polymers 292 14.1 Ethylene-vinyl alcohol polymers (EVOH) 294 14.2 Polypropylene in extrusion coating 297 14.3 Polyester (PET) 299 Recommended further reading 302 Index 304 VI