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Base coats for automotive OEM


About 80% of all top coat systems in the automotive industry consist of two layers: base coat and clear coat. The base coat provides the actual color and any effects like wet-look and metallic finishes. Good pigment wetting of the binder, fixation of the bronce and lightfastness for a long period of time are very important.

Today's base coats mainly use waterborne raw materials due to the considerable potential to reduce solvents (VOC) in this area. Waterborne polyurethane dispersions also have technical advantages regarding effects and stone chip protection.

For the most part, combinations of polyacrylate and polyurethane binders are used in this area. The function of polyurethanes is to improve important properties like brilliance, adhesion, flow characteristics and elasticity, which are important for the stone chip resistance.

The brand name Bayhydrol® stands for the Bayer MaterialScience’s polyurethanes for base coats and includes waterborne polyurethane dispersions as coating binders.

Some examples for waterbased raw materials in base coats

Polyurethane / polyacrylate dispersions:

Type
Solids
in %
pH
Viscosity
mPas at 23°C
Characteristics
Bayhydrol®
UH 650
Polyurethane dispersion
50
7.0
21 sec*
Aliphatic polyurethane resin, for waterborne air-drying and stoving base coats, excellent adhesion and water resistance
Bayhydrol®
UH 2952/1
Polyurethane dispersion
40
7.0
20 sec*
Suitable for air drying and slightly forced stoving systems, yields even, cloud-free films with good metalic effect, excellent gloss and good weather resistance, good adhesion
Bayhydrol®
UH 2621
Polyurethane dispersion
40
7.5
20 sec*
For waterbased, highly stone-chip resistant coatings, high and low temperature drying automotive fillers and base coats, yields
even, cloud-free films with good metalic effect, excellent gloss and good weather resistance, good adhesion
Bayhydrol®
UA 2798 XP
Polyacrylate / polyurethane
dispersion
44.6
8.0
750
Binder for highly stone-chip resitant coatings, excellent compatibility and pigment wetting
* flow time at 23°C

Polyisocyanate crosslinkers:

Type
Solids
in %
% NCO
on solids
Viscosity
mPas at 23°C
Characteristics
Bayhydur®
3100
HDI polyisocyanate
100
17.4
2800
Hardener component for weather resistant coating systems
Desmodur®
N 3900
HDI polyisocyanate
100
23,5
730
As a hardener for water based systems, mainly as crosslinking partner for waterborne polyol-binders (Bayhydrol®)


Suitable starting formulations

RR 4204OEM – metallic base coat (Bayhydrol® UH 2621)

RR 6902OEM – metallic base coat (Bayhydrol® UA 2798 XP / Bayhydrol® UH 2621)

RR 6903OEM – pearl effect base coat (Bayhydrol® UH 2621)

RR 6901OEM – 2K-metallic base coat for low temperature applications (Bayhydrol® UH 2621 / Bayhydur® 3100 / Desmodur® 3900)


Have a look at this detailed information:

Produktbroschüre Dispersionen
Dispersions - Products and Applications
Toolbox for waterborne 2K Polyurethane-Coating-Systems

Presentation: "Raw materials for one-component stoving coatings - OEM and Industrial"


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See also AutoCreative. The automotive initiative of Bayer MaterialScience