Bayhydrol® – The best stone-chip protection with water based primers

Primers are used in automotive OEM finishing for the most sensitive sections of the car body, like for instance door sills and front sections of cars, which need to be protected in the best possible way against severe stone-chipping. Elastic polyurethane systems are able to resist substantial impact stress without major damage. Bayer MaterialScience also developed products for so-called “primerless-concepts”, which consist of layers that are used instead of primer surfacer. These systems are coated wet-in-wet with waterborne base coats and clear coats.

Hydro - Primers

Some polyurethane raw materials for waterborne primers:

waterborne dispersions:

	Type	Solids in %	pH	Viscosity mPas at 23°C	Characteristics
Bayhydrol® E 270	Oil-free saturated polyester	70	8.0	12000	In combination with waterborne amino resins for low co-solvent waterborne primer surfacer in automotive OEM, hard, but elastic films with good adhesion
Bayhydrol® UH 2952/1	Polyurethane dispersion	40	7.0	20*	For airdrying and forced drying basecoats in 2-layer systems for automotive coatings
Bayhydrol® UH 2621	Polyurethane dispersion	40	7.5	20*	For highly stone-chip resistant coatings like low-temperature curing automotive primer surfacer or stone-chip protection coatings and waterborne base coats, cloud-free films with very good metal effect, outstanding gloss and good water resistance
Bayhydrol® A 2290	Polyester- polyacrylate- dispersion	45	7.4	< 200	In combination with materials like Bayhydur® 3100 for high-gloss top coats, good solvent and tar resistance

*Flow time at 23 °C

Polyisocyanate crosslinker for waterborne dispersions:

	Type	Solids in %	% NCO or OH on solids	Viscosity mPas at 23°C	Characteristics
Bayhydur® BL 5140	W / HDI polyisocyanate	39.5	11.1 blocked NCO, on supply form	8000	Hardener for waterborne one-component polyurethane stoving coatings, for automotive OEM finishing (Hydro Intermediate Coatings, waterborne primer surfacer and topcoats)

Starting formulation for a waterborne intermediate base coat for stone-chip protection:

RR 4116	Intermediate polyurethane base coat for stone-chip protection
	(Bayhydrol® E 270 / Bayhydrol® UH 2621 / Bayhydrol® A 2290 / Bayhydur® BL 5140)