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Nomenclature Bayhydrol®

K 2010
Customer
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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, base coats are mostly waterborne. There is an increasing trend to use waterborne systems due to the efforts to reduce solvent emissions (VOC) in general and the considerable potential to reduce solvents in this area. Waterborne polyurethane dispersions also have technical advantages regarding certain 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 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*
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*
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*
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®
A 145
Polyacrylate dispersion
45
8.0
950
For waterbased base coats, to modify hardness and resistance
Bayhydrol®
UH XP 2648
Polycarbonat/ Polyurethan Dispersion
35
8.0
37*
For flexible waterbased coating system on plastic or metal substrates like one-component metallic, one- and two-component filler and topcoat systems
* 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®)
* NMP= N-Methylpyrrolidon

A suitable starting formulation


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

Have a look at this detailed presentation:

"Bayhytherm®, Bayhydur® BL, Bayhydrol® Dispersions for one-component stoving applications"


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"Download entire brochure on dispersions"



See also AutoCreative. The automotive initiative of Bayer MaterialScience