Process for the preparation of the top coat layer of an automotive OEM multi-layer coating

A process for the preparation of the outer top coat layer of an automotive Original Equipment Manufacture multi-layer coating comprising the steps:

• (1) providing an automotive substrate to be Original Equipment Manufacture top coated,
• (2) preparing an aqueous two-component polyurethane top coating composition by static mixing a non-aqueous hydrophobic polyisocyanate crosslinker component and an aqueous binder component having a binder solids content comprising at least one water-dilutable hydroxyl-functional binder,
• (3) spray-applying the aqueous two-component polyurethane top coating composition on the automotive substrate to be Original Equipment Manufacture top coated, and
• (4) thermally curing the top coat layer applied in step (3),
• wherein the binder solids content of the aqueous binder component comprises 5 to 30 wt.-% of at least one urethane compound A with at least two terminal urethane groups (—NHC(O)OR;
• R=hydrocarbyl residue of a monoalcohol) and having a number-average molar mass (Mn) of from 400 to 5,000, and
• wherein the binder solids content consists of 5 to 30 wt.-% of the at least one urethane compound A and 70 to 95 wt.-% of the at least one water-dilutable hydroxyl-functional binder, wherein the sum of the wt.-% totals 100 wt.-%.