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Basecoats for plastics


About 80% of all topcoat systems in automotive applications consist of two layers: basecoat and clearcoat. The basecoat provides the actual color and any surface effects like wet-look and metallic finishes. Good pigment wetting of the binder, fixation of the bronce and color resistance for a long period of time are very important for basecoats.

There is an increasing trend to use waterborne systems due to the efforts to reduce solvent emissions (VOC) and the considerable potential to reduce solvents in this area. Coating systems based on waterborne polyurethane dispersions can also provide technical advantages in certain effects like stone chip protection. Normally, combinations of polyacrylate and polyurethane binders are used in this application. The function of polyurethane components in this application to improve important properties like brilliance, adhesion, flow characteristics and elasticity, which is important for the stone chip resistance.

The product range of Bayer MaterialScience for base coats in plastic applications covers a broad range of waterbased dispersions under the brand name Bayhydrol®. Our experts can give recommendations for your particular requirements.

Some examples for raw materials in basecoats

Waterbased dispersions:

Type
Solids
in %
pH
Viscosity
mPas at 23°C
Characteristics
Bayhydrol®
UH 650
Polyurethane dispersion
50
7.0
21*
Aliphatic polyurethane resin as co-binder 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®
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 for waterbased dispersions:

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
Hardener for waterbased systems, mainly as crosslinking partner for waterborne polyol-binders (Bayhydrol®)

A selection of starting formulations:

RR 4205Two component basecoat for low temperature applications (Bayhydrol® UH 2621 / Bayhydur® 3100)

RR 6901One component basecoat for low temperature applications (Bayhydrol® UH 2621 / Bayhydur® 3100 / Desmodur® 3900)

RR PCO 006e-BCOne component basecoat for low temperature applications (Bayhydro® UH 2952/1)


For more on basecoats for plastic applications have a detailed look at these brochure:

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





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