Principles of Automotive OEM Coatings
Dr. Ulrike KUTTLER
ALLNEX AUSTRIA GmbH - Our R&D Center in Graz
Allnex at a Glance
A 1.5 Billion $ private equity owned company with
a strong market position in 4 different business lines:




Sales 2012 by Product Line
Liquid Resins and Additives (LRA)
Radiation Curable Resins (RAD)
Powder Resins (PCR)
Crosslinkers (XLR)
Different market segments:
 Automotive
 Industrial
 Packaging coatings and inks
 Protective
 Industrial plastics
 Specialty architectural
Sales 2012 by Segment
Allnex – Our global footprint
2,000 people dedicated to Coating Resins
Allnex – Our Technologies for Automotive OEM Coatings
RESYDROL® :
Waterdilutable Alkyd- and modified Alkyd resins
Waterdilutable Polyester- and modified Polyester resins
DAOTAN ® :
Waterdilutable Polyurethane dispersions
VIACRYL ® :
Water- and solventdilutable Acrylic resins
MACRYNAL ® :
Isocyanate crosslinkable Acrylic resins (s/b & w/b)
CYMEL ® :
Melamine Aminoplast Crosslinkers (methylated, butylated as well as
mixed alcohols range)
CYCAT ® :
Catalysts for Melamine Amino Crosslinkers
ADDITOL ® :
Additives for
 Pigment wetting
 Stabilizing aluminum pigments in waterborne Basecoats
 Leveling & flow
 Substrate wetting
 Degassing & defoaming
Automotive OEM Layers
Clearcoat
DFT: approx. 50 - 60µm
Topcoat
DFT: approx. 50 - 60µm
Basecoat
DFT: approx. 10 - 30µm
Primer Surfacer
DFT: approx. 25 - 35µm
Cathodic Electrodeposition „CED“
DFT: approx. 20µm
Metal & Pretreatment
Automotive OEM Layers - their main responsibilities
Cathodic Electrodeposition „CED“
Corrossion protection (together with pretreatment layer) of the car body
Primer Surfacer – the „damping- and preparation“ layer
Protection against mechanical impacts (stone chip protection )
Leveling of unevenness and irregularities (sanding marks, poor leveling / high
roughness of CED)
Basecoat – the „style / emotion“ layer
Providing color and effect – also of high importance for supporting the shape of
the car body
Clearcoat – the „appearance and protection“ layer
Appearance:
Excellent leveling (smooth surface)
High gloss and body
Protection:
UV radiation (causes degradation of the polymers)
Chemicals (gasoline, acids, tree gum, bird droppings,……)
Mechanical impacts (scratches, car wash brushes,…..)
Cathodic Electrodeposition
A short introduction
CED
 History
 Basics
 Coating composition
 Tank
 Adjustments
CED - History
 Anodic Electrodeposition
Since 1961 (FORD-Patent)
Heyday: 1965 till approx. 1978
 Cathodic Electrodeposition
Starting in 1975
State-of-the-art technology till today
CED - Basics
What do we need for CED?
 A conductive object to be coated
(all kinds of metal or metalized substrates)
 Electric power (DC) generated by a rectifier
 The CED bath with anode cells as counter electrodes
 An oven (150 – 190°C) for the stoving process
CED - Basics
Advantages of CED
 Fully automated
 No limitation for the shapes of objects
 Good penetration into holes (throwing power)
 No overspray and other losses (except loss of the isocyanate
blocking agent)
 Best corrosion resistance of all coating systems
Disadvantages
 Rather high investments for the coating line
 Curing temperature >140°C
CED - Basics
Principle of CED
-
+
Water/e-Coat
Elektrolyse
Electrolysis
Anode:
Formation of H+-ions
(acid)
Coagulation
Koagulation
Cathode:
Formation of OH--Ions
(Base)
The resin coagulates by the pH-shift
CED – The Coating Composition
1. Cationic resin dispersion (also containing the crosslinker)
2. Pigments
3. Cosolvents
4. Additives
5. Curing catalyst
6. Deionised Water
1. Cationic Resin Dispersion for Primer:
A. Backbone resin
OH
OH
N
Epoxy resin
B. Crosslinker: blocked aromatic Isocyanates
C. Catalyst: metal catalyst
H+
N
RCOOOrganic acids like
Formic, acetic, lactic,….
Cationic Resin Dispersion for Monocoats:
A. Backbone resin
OH
OH
N
H+
polyacrylate
OH
B. Crosslinker: blocked aliphatic Isocyanates
N
RCOO-
Performance Comparison
Epoxy - CED
Acrylic - CED
Corrosion resistance
+++
-
UV - resistance
---
++
Feasible color range
---
++
Stoving temperature
> 160°C
> 170°C
Salt Spray Test ASTM (500 hrs)
Infiltration
[mm]
6,5
aromatic
aliphatic
acrylic/30% EP
5
acrylic/15% EP
Epoxy
5
4
3
1
0
1
2
3
4
5
240 hrs Accelerated Weathering (QUV - B)
Loss of
gloss
100
aromatic
100
aliphatic
acrylic/30% EP
68
50
22
15
4
0
1
2
3
4
5
acrylic/15% EP
epoxy
2. Colors/Pigments
 Epoxy CED for car bodies: grey
TiO2, carbon black, (extenders)
 Epoxy CED for small parts: black
Carbon black, extenders
 Acrylic CED for Monocoat systems: different colors
Organic pigments
2. Colors/Pigments
For the pigment grinding a separate grinding resin is used!
The CED system consists of 2 components
 the CED dispersion (clear, not pigmented)
 the pigment paste
Both components are fed into the tank separately
3. Role of the Cosolvents:
Influencing film forming:
The higher the solvent content, the softer the film in the
deposition stage:
 the lower the film resistance
 the higher the flow of electricity
 the higher the film build
 increase of the bath temperature has same effect
Well established cosolvents are Texanol, Hexylglycol,
Phenoxypropanol and Butylglycol (as carrier for the others)
4. Additives
 Anti crater agents (incompatible with the ecoat):
 Edge protection additives
 Zinc pinhole additives (use of cosolvents is also possible)
 Dispersing additive: for preparing the water dilutable catalyst
dispersion
5. Curing Catalysts
 Blocked aromatic isocyanates need a metal catalyst for
deblocking and crosslinking
 Catalysts in use are DBTO, DOTO, Bismuth compounds
 All catalysts need a special preparation to bring them into a
water dilutable form, which cannot be hydrolised in the
waterborne ecoat
E- Coat characteristics (CED)
Solids content
15 – 20 %
pH
4-6
Conductivity
800 – 1500 µSi
MEQ-value
25 - 40
(milliequivalent acid/
100 g solid resin)
Pigment binder ratio
0,15 : 1 (black)
< 0,1 : 1 (organic)
< 0,5 : 1 (grey)
General Parameters
1.
Voltage 30 – 420 Volt DC
2.
Current (Ampere) depending on film resistance
3.
Deposition time (sec)
4.
Bath temperature (°C)
5.
Electric charge (As, Cb)
6.
Deposition equivalent (Cb/g deposited ecoat)
Minimum Coalescing Temperature MCT
(Constant voltage)
µm 40
35
irregular deposition
regular deposition
30
25
20
15
10
20
22
24
26
28
30
32
Bath temperature °C
Cosolvent addition: moves the MCT and µm to the right
CED - Process:
 Deposition time 2 - 4 minutes
 Loss of solid material is compensated by addition
of new material (dispersion as well as pigment paste)
ANODE:
 Formation of the neutralisation acid (removed by the
anolyte)
 Formation of oxygen
CATHODE:
 Deposition, coating formation of hydrogen
Film Forming During the Electrodeposition
 The amount of deposited material decreases with the
time of deposition, as the film forms a layer with strongly
reduced conductivity
 Depending on the softness of the E- coat (Tg of the resin),
normal film thickness (15 – 25 µm) up to high film build
(25 – 50 µm) can be generated
 Throwing power: the ability of the E- coat to penetrate
into holes
 The film is almost dry after deposition (<2% water) after
rinsing
Circulation of Anolyte, Ultrafiltration:
 ANOLYTE = liquid phase in the anode, which absorbs the acid
which is generated by the deposition
 ULTRAFILTRATION = additional removal of waterborne
components from the coatings system.
Turnover
Is the time for full consumption of the material in the tank

Depends on coated surface/time

Typical turnover is 2-5 weeks, but can go up to 1 year
(stability challenge!)

Tank size and turnover define the consumption of the
material; tank size can go up to 500 m³ (bigger cars,
buses)
Metal Substrates/Pretreatments
 Blank steel (only used for testing purposes)
 Iron phosphated steel (low end substrates)
 Zinc phosphated steel (most common substrates for
Automotive and GI, gives highest performance – depending
on dotation and rinsing; Cr free rinse is a must in EU)
 Sandblasted steel (very seldom)
 Other metal substrates Mg, Al, …. deliver different deposition
performance and have to be evaluated individually
Challenges:
 Cratering (external contaminations)
 Leveling
 Pinholes (MCT – behaviour)
 Coagulation in the tank
(too low neutralisation, bacteria ?)
 Redissolution (too low pH in CED)
 New metal pretreatments (e.g. Zirconium- based)
Primer Surfacer
A Short Introduction
Primer Surfacer
 History
 Basics
 Coating composition
 Trends
Primer Surfacer - History
 Only solventbased (s/b) chemistry till late 1980 / early
1990s
 Worldwide first waterborne (w/b) Primer Surfacer at
Opel in Germany early 1990s
 Other OEM‘s (VW- Group, Volvo, Daimler, BMW,…..)
followed within the next decade
 Today w/b Primer Surfacer is „state of the art“ but still a
high amount of s/b technology in use (Fiat, Renault, PSA,
OEM‘s in US and Asia,……)
36
Technology Segmentation Primer Surfacer:
Development from 2004 to 2010
100%
100%
90%
90%
80%
80%
70%
70%
60%
60%
50%
50%
40%
40%
30%
30%
20%
20%
10%
10%
0%
0%
Europe
Eastern&Central
E.
w/b
Primer
Surfacer
Europe
2004
WB
POWDER
SB
40%
2%
58%
100%
Americas
Powder
East &
Central
Europe
2004
10%
0%
90%
100%
Japan
Asia
Europe
Eastern&Central
E.
w/b
solvent
Americas
2004
Japan
2004
8%
51%
41%
100%
10%
Asia
2004
(Outside
JP)
5%
90%
100%
95%
100%
Primer
Surfacer
Europe
2010
WB
POWDER
SB
70%
4%
26%
100%
Americas
Powder
East &
Central
Europe
2010
14%
0%
86%
100%
Japan
Asia
solvent
Americas
2010
Japan
2010
11%
70%
19%
100%
30%
Asia
2010
(Outside
JP)
10%
70%
100%
90%
100%
Primer Surfacer - Basics
 Application of the Primer Surfacer with ESTA (electrostatic
application) by means of high speed bells
 Dry film thickness (DFT) can vary from 20 – 35µm
 Standard baking conditions: 20min/165°C (at some OEMs
lower temperatures down to 145°C )
 Each OEM / OEM line has more or less different requirements
38
Basics
Main Requirements for the Primer Surfacer
 Excellent Appearance (gloss, leveling, absolutely NO surface defects)
 Broad application window = high robustness of the Primer Surfacer
(temperature, humidity, application speed , baking conditions……) to
achieve high first run o.k. rates
 Excellent adhesion to different CED- and PVC qualities
 Excellent intercoat adhesion to a broad variety of Basecoats
 Excellent humidity resistance
 Excellent mechanical properties – tough elastic even at -20°C
 Shear & storage stability
 …….
 ......
39
Primer Surfacer – The Coating Composition
s/b Primer Surfacer
Polyester (mod. Alkyd)
Epoxy resin
Melamine Crosslinker
Benzoguanamine Crosslinker
Pigments
Extenders
Additives
Solvents (> 40%)
w/b Primer Surfacer
mod. Alkyd
Polyester (PU- mod.)
Melamine Crosslinker
blocked Polyisocyanate
Pigments
Extenders
Additives
Solvents (< 5%)
40
Primer Surfacer – The Coating Composition
EPOXY Modifier Resin
Adhesion
Corrosion resistance
Pigment wetting
Basic Resin
Levelling
Hardness
Economic efficiency
Polyester Modifier Resin
Stone chip resistance
IMPROVE
PU Modifier Resin
41
Trends / Challenges for the Primer Surfacer Layer:
 Further improved appearance (gloss, leveling)
 further broadening of application window („robustness“)
 Lower cost / higher productivity
 Low bake (< 120°C?)
 Elimination of Primer Surfacer layer in „Compact Paint
processes“
42
Basecoat
A short introduction
Basecoat
 History
 Basics
 Coating composition
 Trends
Basecoat - History
 Only solventbased (s/b) chemistry till mid 1990s
 All German OEM‘s meanwhile use w/b Basecoat
 Today w/b Basecoat is „state of the art“ but still a high
amount of s/b technology in use (Fiat, Renault, PSA,
OEM‘s in US and Asia,……)
 Due to steadily increasing legislative pressure in China
w/b Basecoat technology is growing much quicker than
expected.
45
w/b Basecoat in Global Car Production
90
80
70
Mio Cars
60
50
40
30
20
10
0
1997
1999
2001
2003
2005
World (w/b)
2007
2009
World (all)
2011
2013
2015
% w/b BC
Conversion from s/b to w/b OEM Basecoat
Basecoat - Basics
 Application of the Basecoat with ESTA (electrostatic
application) by means of high speed bells or for metalic
Basecoats ins 2 runs (ESTA / pneumatic gun)
 Dry film thickness (DFT) can vary from 10 – 30µm (color
dependant!)
 Standard baking conditions: 10min/80°C, followed by
20min/145°C (together with Clearcoat)
 Due to the huge variety of colors and effects the most
sophisticated paint layer of the car. An advanced formulation
know how as well as carefull resin selection is key!
48
Basecoat - Basics
Main Requirements for the Basecoat









Excellent appearance (effect, leveling, absolutely NO surface defects)
Excellent adhesion to different Primer Surfacer qualities
Excellent intercoat adhesion to a broad variety of Clearcoats
Excellent humidity resistance
Excellent mechanical properties – tough elastic even at -20°C
Shear & storage stability
Robust in application
…….
......
49
Basecoat – The Coating Composition
s/b Basecoat
Polyester (PUD mod.)
CAB
Melamine Crosslinker
Pigments
Talcum
Additives
Solvents (> 70%)
w/b Basecoat
PUD, Polyester, Acrylic
Thickener
Melamine Crosslinker
Pigments
Talcum
Additives
Solvents (~ 10%)
50
Basecoats – The Modular Approach
 Polyurethane dispersion (PUD)
Is providing adhesion, flexibility, appearance (flip flop effect in metallic BC) and stone chip
properties. Very important component in the formulation!
 Acrylic dispersion
Is providing hardness, physical drying, helps to fix the aluminum pigment and is decreasing
overall formulation cost
 Melamine resin
Is improving leveling, wetting of Clearcoat, and intercoat adhesion (BC/CC), increase open
time of BC
 Polyester
Can help to improve levelling, adhesion, flexibility and stone chip properties. Is also used in
pigment pastes.
 Thickener
Is providing the rheological properties for the BC. Very important in metallic BC to achieve a
perfect flip flop effect
Structure of PU-Dispersions
In the synthesis of PU dispersions Polyisocyanates (hard segments) and
Polyols (soft segments) are co- reacted in a polyaddition reaction.
Soft - Segments
Hard - Segments
OH-Polyester
OH-Alkyd
OH-Polyether
OH- Acrylate
OH- Polycarbonate
Polyisocyanate (TDI, IPDI,
TMXDI...)
Diol
Dimethylolpropionic acid
(Amine)
52
Typical Hard - Segments
Aliphatic / Cycloaliphatic
(CH2)6
N
O
O C N
(CH2)6
N C O
O C N
Hexamethylene diisocyanate (HDI)
(CH2)6
N
O
N
(CH2)6
(CH2)6
Urethdion
N
Isocyanurate
N
(CH2)6
N C O
(CH2)6
H
O
H
O C N
(CH2)6
O C N
CH3
CH3
O C N
N
N
N
O
H3C
N C O
O
O
O C N
N C O
O
N C O
(CH2)6
N C O
Biuret
N C O
N C O
Isophorone diisocyanate (IPDI)
Dicyclohexylmethandiisocyanate (Desmodur W)
53
Typical Hard - Segments
Aromatic
CH3
CH3
N C O
O C N
N C O
N C O
Toluylene diisocyanate
(TDI)
N C O
O C N
N C O
N C O
Diphenylmethane diisocyanate
(MDI)
54
Schematic Production Process for PUDs
Soft-Segments
Hard-Segments
Co-reacting Soft- and Hard-Segments
Neutralization
(amines or strong bases)
Dispersing in water
Chain elongation
Chain stopping
55
Different Production Procedures for PUDs
„ACETONE“ PROCESS
1. Polyaddition (i.e. co- reaction of soft segments with Polyisocyanates and a
hydrophilic acid component) as well as the chain extension step (with Di- oder
Polyamines) is run in Acetone (homogeneous phase)
(instead of Acetone solvents like e.g. MEK, MIBK, THF are also suitable)
2. After the neutralization- and dispersion step the Acetone is distilled off
Advantages:
• Very universal
• Viscosity during synthesis easy to control
Disadvantages:
• complex and expensive
• residual solvent in the resin
• Process not sustainable
• Unfavorable yield
Different Production Procedures for PUDs
„MELT“ PROCESS
1. Polyaddition (i.e. co- reaction of soft segments with Polyisocyanates and a
hydrophilic acid component) is run WITHOUT any solvent (in a melt)
2. A potential chain extension step is run AFTER the neutralization and
dispersion step (i.e. in water)
Advantages:
• NO residual solvent
• Food yield
• No „solvent waste“
Disadvantages:
• Tricky process (very high viscosities)
• Process not suitable for all the different PUD- chemistries
Different Production Procedures for PUDs
„SOLVENT“ PROCESS
1. Polyaddition (i.e. co- reaction of soft segments with Polyisocyanates and a
hydrophilic acid component) is run WITH solvent (NMP/NEP are the most
common ones)
2. A potential chain extension step is run AFTER the neutralization and
dispersion step (i.e. in water)
Advantages:
• very universal
• viscosity during synthesis easy to control
Disadvantages:
• Resin may contain quite high amounts of solvent
• Toxicology and price of NMP / NEP
Different Production Procedures for PUDs
„MONOMER“ PROCESS
1. Polyaddition (i.e. co- reaction of soft segments with Polyisocyanates and a
hydrophilic acid component) is run in acrylic monomers (acrylic /methacrylic
acid and esters thereof) that act as „solvent“
2. A potential chain extension step is run AFTER the neutralization and dispersion
step (i.e. in water)
3. Radical polymerization of the acrylic monomers yields a solvent free, acrylic
modified PUD (graft polymer)
Advantages:
• NO residual solvent
• Good yield
• No „solvent waste“
Disadvantages:
• Smart but tricky process
• Only for acrylic modified PUDs (graft polymers)
Film Morphology
Hard - Segment 
„ net-points“
Soft - Segment 
flexibility
Soft- and Hard- Segments within the polymer are leading to a
„structure of domains“.
This special stucture is creating the well known tough-elastic behaviour
of PUD based coatings (even at low temperatures!)
60
PU Dispersions – Structure Properties
O
R
NH
C
Urea
O
NH
R
R
NH
C
O
R‘
Urethane
Urea- as well as Urethane groups have a strong dipole moment.
This is causing strong interactions with the surface of substrates
excellent adhesion to “difficult substrates” like e.g. plastics
Moreover this dipole moment is causing strong intermolecular forces
(cohesion)
outstanding mechanical properties and elasticity
61
PUD Basics – The „Take Aways“
1. PUD‘s are produced by a polyaddition- reaction of soft segments (OH- group
containing pre- polymers) with Polyisocyanates (hard segments) and a
hydrophilic acid component
2. The different production procedures for PUD- resins are tricky and complex
3. The majority of the hard segments (Polyisocyanates) as well as many soft
segments (OH- Polycarbonates, OH- Polyethers,….) are high price raw
materials leading to PUD‘s with elevated price level
4. The achieved properties like
•
•
•
•
Adhesion to critical substrates
Outstanding mechanical properties
Excellent elasticity and abrasion resistance
Tough elastic behaviour even at low temperatures
make PUD‘s a first choice for Automotive OEM Basecoat applications!
Polyurethane Dispersions
Structure – Property
Relationships
PUDs – Soft Segments
Soft Segment
Advantage
Disadvantage
OH- Polyester
Very good appearance
V. good mech. properties
Hydrolytic stability
OH- Alkyd
Good body
Good substrate penetration
Yellowing, outdoor durability
Hydrolytic stability
OH- Polyether
Low viscosity
Hydrolytic stability
Poor light- and thermo
stability
OH- Polyacrylate
Quick drying
Outdoor durability
Stability against oxidants
OH- Polycarbonate
Hydrolytic stability
Outdoor durability
High Price
PUDs – The Molecular Weight
PUD‘s with low / medium molecular weight („chain stopped“ grades)
designed for crosslinking with Polyisocyanates or Amino resins
Advantages:
• Good leveling (due to slow physical drying)
• Good degassing
• Good pigment wetting
• Excellent chemical- and solvent resistance properties
• Excellent mechanical- and adhesion properties
• Can be formulated with little to no solvents
Disadvantages:
• Need crosslinker (Polyisocyanate or Amino resin)
• More complicated handling (valid only for 2K formulations)
• Potlife (valid only for 2K formulations)
• Price (expensive Polyisocyanate)
PUDs – The Molecular Weight
PUDs with high / very high molecular weight („chain extended“ grades)
Designed for 1-pack applications (further crosslinking is possible)
Advantages:
• Quick physical drying
• Excellent orientation of metalic pigments (bright metalic effect!)
• Outstanding elasticity, adhesion and mechanical properties
• No need for crosslinker
• Easy handling (1 pack!)
• No potlife
Disadvantages:
• Weak pigment wetting
• Weak chemical- and solvent resistance properties
• Poor leveling (due to quick physical drying)
• Should be formulated with solvents
PUDs – Preferred Fields of Application
SUBSTRATE
Plastic
Metal
LAYER
MAIN BENEFIT
Primer
Adhesion, mech. properties
Basecoat
Monocoat
Adhesion, metalic effect,
mech. properties
Primer Surfacer
Adhesion, stone chip properties
Basecoat
Adhesion, metalic effect, mech.
properties
Current Trends in the Base Coat Area
 Completely eliminate NMP/NEP from recipes (change in
legislation)
 „Lower cost“
 Further improved robustness i.e. stable color position regardless of
humidity / temperature conditions, spraying conditions, type of
Clearcoat, substrate,…….
 New color effects
 Bell / bell application
Clearcoat
A short introduction
Clearcoat
 Technology- and market overview
 Basics
 Coating composition
 Trends
OEM Clearcoats – Technology Overview
Till 2010 the Clearcoat layer was the one with the broadest diversification.
Following technologies were in use:
Technology
In use at
s/b 1K- Clearcoat
Fiat, Peugeot, Renault,…
s/b 1K- Clearcoat
Toyota and other Japanese OEM‘s
s/b 2K- Clearcoat
VW, Audi, Mercedes, BMW,…….
w/b 1K- Clearcoat
Opel (Eisenach plant only), Mercedes
(Melamine crosslinked)
(Carboxy – Epoxy technology)
(Polyisocyanate crosslinked)
(Melamine crosslinked)
Powder Clearcoat
(Rastatt plant only)
BMW (ONLY!!)
Technology Segmentation Clearcoat: Development from 2004 to 2010
100%
100%
90%
90%
80%
80%
70%
70%
60%
60%
50%
50%
40%
40%
30%
30%
20%
20%
10%
10%
0%
Europe
Eastern&Central
E.
w/b
CLEAR
COAT
Europe
2004
WB
1K
Melamine
2K
1K_Acidcar
boxy
Powder
1.6%
100%
1K s/b
Americas
2K s/b
Japan
Carboxy-Epoxy
Asia
0%
Europe
Powder
Eastern&Central
E.
w/b
Middle/East/
Central
EU2004
Americas
2004
Japan
2004
Asia 2004
(Outside JP)
CLEAR
COAT
Europe
2010
1.7%
70.0%
80%
60%
21%
58%
WB
1K
Melamine
26.7%
20%
15%
25%
30%
49%
16%
26%
2K
1K_Acidcar
boxy
Powder
100%
100%
100%
100%
1K s/b
2K s/b
Americas
Japan
Carboxy-Epoxy
Asia
Powder
Middle/East/
Central
Europe 2010
Americas
2010
Japan
2010
Asia 2010
(Outside JP)
4%
54%
80%
57%
21%
62%
38%
20%
15%
27%
30%
49%
14%
24%
100%
0.3%
100%
4.6%
100%
100%
0.5%
100%
OEM Clearcoats – Technology Overview
Since 2010 a steady consolidation of Clearcoat technologies is ongoing:
 w/b 1K Clearcoat stopped at Opel Eisenach and Mercedes Rastatt ->
switch to s/b Clearcoat!
 BMW stopped powder Clearcoat -> switch to s/b 2K Clearcoat
 s/b 2K Clearcoat is increasing, but worldwide s/b 1K Clercoat still has
a share of approx. 80%
Clearcoats – Basics
 Application of the Clearcoat with ESTA (electrostatic
application) by means of high speed bells
 Dry film thickness (DFT) in the range from 50 – 60µm
 Standard baking conditions: 20min/145°C
 The paint layer where majority of final properties is provided
by the resin technology. Carefull resin selection is key!
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Clearcoats – Basics
Main Requirements for the Clearcoat
 PREMIUM Appearance (gloss, leveling, absolutely NO surface
defects)
 Excellent adhesion to different Basecoat qualities
 Excellent outdoor durability, no yellowing
 Excellent humidity resistance
 Excellent mechanical properties – tough elastic even at -20°C
 Excellent chemical resistance (solvents, chemicals, acids, …….)
 Excellent scratch resistance (carwash!!)
 Robust in application
 Easy to repair by sanding or polishing
 ......
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s/b 1K Clearcoats
Basic components
Properties
Acrylic resin
Outdoor durability, chemical
resistance and hardness
Polyester resin
Body, leveling, adhesion, scratch
resistance, outdoor durability
Sca mod. resins
Antisagging and good flow/aspect
Melamine
Crosslinker
Blocked Isocyanate
Flexibility, chemical resistance
Catalyst
Reactivity (if necessary)
s/b 2K Clearcoats
Basic components
Properties
Acrylic resin
Outdoor durability, chemical
resistance and hardness
Polyester resin
Body, leveling, adhesion, scratch
resistance, outdoor durability
Sca mod. resins
Antisagging and good flow/aspect
Polyisocyanate
Crosslinker
Melamine resin
Additional crosslinking
OEM Clearcoats – Technology Comparison
Technology
s/b 1K
(Melamine)
s/b 2K
(Polyisocyanate)
PROS
Price
Robustness
Scratch resistance
Easy handling (no 2K equipment!)
No Formaldehyde issue
Acid- / chemical resistance
Film build
Appearance
Gloss
Suitable for compact process
CONS
Formaldehyde release
Acid- / chemical resistance
Film build
Appearance , gloss
not for compact process
2K equipment needed
Price
Scratch resistance
Current Trends for the Clearcoat
 Appearance, appearance, appearance
 „Lower cost“
 Further improved robustness (less rework!)
 Improved scratch resistance
 Higher solids content (due to more stringent legislation)
Contact Details:
Dr. Ulrike KUTTLER
Global Application Technology Manager, Automotive
Ulrike.Kuttler@allnex.com
Phone: +43 50399 1302
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