Automotive Coatings Formulation: Chemistry, Physics und Practices

Light-protection additives
While UV absorbers are essential for clearcoats, they are no longer used in pigmented topcoats 
since the pigment particles adequately absorb the UV light. However, there are some pigment par-
ticles whose surfaces can act as catalysts for photolysis in the binder matrix under the influence 
of UV light. This can lead to destruction of the upper parts of the film, and ultimately to matting 
and chalking. For example, titanium dioxide has to be post-treated with additive oxides to avoid 
this photocatalysis, which induces destruction of the film matrix.
Formulation example
Table 3.6.4 shows the composition of a white automotive OEM topcoat
 
[123]
. The resins contain a 
combination of an alkyd resin, modified with saturated fatty acid and a relatively reactive mela-
mine resin. In addition, the formulation contains a pigment-wetting agent, modified silicone oil 
Table 3.6.4: Example of a white automotive OEM topcoat
Pos.
Components
Solid wt-‰
Formulation wt-‰
01
alkyd resin. modified with saturated fatty acids 
(70 % in xylene)
132.3
189.0
02
dispersion agent
1.8
03
titanium dioxide, rutil
301.0
301.0
04
xylene
66.0
05
aromatic 150
28.2
dispers on fineness <5 µm, then add:
06
alkyd resin, modified with saturated fatty acids 
(70 % in xylene)
56.7
81.0
07
alkyd resin, modified with saturated fatty acids 
and crystalline urea
(67 % in xylene / n-butanol 96/14) 
94.5
4.0
147.0
08
melamine resin (70 %), butanol-etherified
95.2
136.0
09
silicone oil
1.0
10
Depanol J
38.0
11
n-butanol
30.5
sum
683.7
1000.0