Automotive Coatings Formulation: Chemistry, Physics und Practices

3 
Automotive OEM coatings .......................................................................... 
41
3.1 
History of automotive coatings ...................................................................................... 
41
3.2 
Automotive coatings as a multilayer system .............................................................. 
42
3.3 
Application processes for automotive coatings ......................................................... 
44
3.4 
Pre-treatment and primers ............................................................................................. 
46
3.4.1 
Substrates and corrosion ................................................................................................ 
46
3.4.2 
Pre-treatment .................................................................................................................... 
48
3.4.3 
Advent of electro deposition primers ........................................................................... 
49
3.4.4 
Requirements and properties ........................................................................................ 
55
3.4.5 
Composition of cathodic electro deposition primers ................................................ 
59
3.4.5.1 
Epoxy resins ...................................................................................................................... 
59
3.4.5.2 
Amine modification of epoxy resins ............................................................................ 
60
3.4.5.3 
Further modifications ...................................................................................................... 
63
3.4.5.4 
Grinding resins ................................................................................................................. 
65
3.4.5.5 
Crosslinkers ....................................................................................................................... 
65
3.4.5.6 
Pigments ............................................................................................................................ 
67
3.4.5.7 
Additives ............................................................................................................................ 
67
3.4.5.8 
Overall primer formulation ............................................................................................ 
68
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3.4.6 
Application of electro deposition primers .................................................................. 
71
3.4.6.1 
Deposition .......................................................................................................................... 
71
3.4.6.2 
Process sequence and equipment ................................................................................ 
72
3.4.7 
Prospects for electro deposition primers .................................................................... 
74
3.4.8 
Underbody seals and seam sealants ............................................................................ 
74
3.4.8.1 
Underbody seals ............................................................................................................... 
74
3.4.8.2 
Seam sealing ..................................................................................................................... 
75
3.5 
Primer surfacers ............................................................................................................... 
76
3.5.1 
Development of primer surfacers ................................................................................. 
76
3.5.2 
Requirements and properties ........................................................................................ 
79
3.5.3 
Composition of solvent-borne primer surfacers ........................................................ 
84
3.5.3.1 
Saturated polyesters ........................................................................................................ 
84
3.5.3.2 
Amino resins ..................................................................................................................... 
86
3.5.3.3 
Blocked polyisocyanates ................................................................................................. 
91
3.5.3.4 
Pigments for primer surfacers ...................................................................................... 
93
3.5.3.5 
Solvents .............................................................................................................................. 
95
3.5.3.6 
Additives ............................................................................................................................ 
96
3.5.3.7 
Formulations ..................................................................................................................... 
97
3.5.4 
Application ........................................................................................................................ 
98
3.5.5 
High-solid primer surfacers ........................................................................................... 
99
3.5.6 
Water-borne primer surfacers ........................................................................................ 
99
3.5.6.1 
Resins for water-borne primer surfacers ..................................................................... 
99
3.5.6.2 
Formulations for water-borne primer surfacers......................................................... 104
3.5.7 
Powder primer surfacers ................................................................................................ 105
3.5.7.1 
Resins for powder primer surfacers ............................................................................. 106
3.5.7.2 
Formulation and production of powder primer surfacers ....................................... 107
3.5.7.3 
Application ........................................................................................................................ 109
3.6 
Topcoats .............................................................................................................................. 
111
3.6.1 
Development of topcoats for automotive coatings .................................................... 
111
3.6.2 
Requirements on topcoats .............................................................................................. 
112
3.6.2.1 
Application behaviour ..................................................................................................... 
113
3.6.2.3 
Resistance properties ...................................................................................................... 
116
3.6.3 
Composition of OEM topcoats ........................................................................................ 
117
3.6.3.1 
Alkyd resins ...................................................................................................................... 
117
3.6.3.2 
Melamine resins ............................................................................................................... 120
3.6.3.3 
Other resins ....................................................................................................................... 122
3.6.3.4 
Inorganic pigments .......................................................................................................... 122
3.6.3.5 
Organic pigments ............................................................................................................. 126
3.6.3.6 
Pigmentation of topcoats ................................................................................................ 131
3.6.3.8 
Additives ............................................................................................................................ 134
3.6.4 
Application ........................................................................................................................ 136
3.6.5 
Topcoats with reduced VOC emissions ....................................................................... 136
3.7 
Basecoats ............................................................................................................................ 137
3.7.1 
Development of basecoats .............................................................................................. 137
3.7.2 
Demands on conventional basecoats ........................................................................... 139
3.7.2.1 
Conferring effects ............................................................................................................. 139
3.7.2.2 
Application behaviour ..................................................................................................... 142
3.7.2.3 
Resistance .......................................................................................................................... 143
3.7.3 
Composition of solvent-borne basecoats ..................................................................... 143
3.7.3.1 
Cellulose acetobutyrate ................................................................................................... 143
3.7.3.2 
Polyesters ........................................................................................................................... 145
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Content
3.7.3.3 
Amino resins ..................................................................................................................... 146
3.7.3.4 
Rheological additives ....................................................................................................... 146
3.7.3.5 
Effect substances .............................................................................................................. 146
3.7.3.6 
Coloured pigments ........................................................................................................... 153
3.7.3.7 
Solvents .............................................................................................................................. 154
3.7.3.8 
Other additives ................................................................................................................. 155
3.7.3.9 
Formulation example ....................................................................................................... 155
3.7.4 
Basecoats with increased application solids .............................................................. 155
3.7.5 
Water-borne basecoats .................................................................................................... 157
3.7.5.1 
Resins for water-borne basecoats ................................................................................. 157
3.7.5.2 
Rheological additives ....................................................................................................... 
161
3.7.5.3 
Pigments and effect substances .................................................................................... 162
3.7.5.4 
Cosolvents and additives ................................................................................................ 162
3.7.5.5 
Formulation example and application ......................................................................... 163
3.7.6 
Solid colour water-borne basecoats .............................................................................. 163
3.7.7 
Alternatives ....................................................................................................................... 164
3.8 
Clearcoats .......................................................................................................................... 164
3.8.1 
Development of clearcoats ............................................................................................. 164
3.8.2 
Requirements on automotive OEM clearcoats ........................................................... 165
3.8.2.1 
Application behaviour and surface of clearcoats ....................................................... 166
3.8.2.2 
Weathering resistance ..................................................................................................... 167
3.8.2.3 
Chemical resistance ......................................................................................................... 170
3.8.2.4 
Mechanical resistance ..................................................................................................... 
171
3.8.2.5 
Scratch resistance ............................................................................................................ 
171
3.8.2.6 
Windscreen bonding ........................................................................................................ 173
3.8.2.7 
Protection in transport .................................................................................................... 173
3.8.3 
Composition of clearcoats ............................................................................................... 
174
3.8.3.1 
Acrylic resins .................................................................................................................... 
174
3.8.3.2 
Polyesters ........................................................................................................................... 178
3.8.3.3 
Amino resins ..................................................................................................................... 179
3.8.3.4 
Polyisocyanates ................................................................................................................. 179
3.8.3.5 
Blocked polyisocyanates ................................................................................................. 181
3.8.3.6 
Solvents .............................................................................................................................. 183
3.8.3.7 
Levelling agents ................................................................................................................ 183
3.8.3.8 
Light stabilisers ................................................................................................................ 185
3.8.3.9 
Rheological additives ....................................................................................................... 187
3.8.3.10 
Formulation example ....................................................................................................... 187
3.8.3.11 
Nanoparticles for clearcoats ........................................................................................... 187
3.8.3.12 Lotus effect ........................................................................................................................ 190
3.8.3.13 
Sealers for clearcoats ....................................................................................................... 
191
3.8.4 
Application ........................................................................................................................ 
191
3.8.5 
Clearcoat with increased solid contents ..................................................................... 192
3.8.6 
Water-borne clearcoats .................................................................................................... 193
3.8.7 
Powder clearcoats............................................................................................................. 195
3.8.8 
UV clearcoats .................................................................................................................... 198
3.9 
Reductions in solvent emissions ................................................................................... 200