Hi

Hoping there may be some people here with knowledge on 2K paints that may be able to clarify something for me:

When spraying 2K polyurethane auto paints, isocyanates and solvents are present in the spray mist. If the over-spray is captured in an exhaust filter at normal temperatures (and no longer airborne), do the isocyanates remain and cure like the resins or do they evaporate / vaporise like the solvents and continue to vent to atmosphere?

I had thought that they evaporate but upon reading some literature on brushing / rolling on 2K paint, they seemed to indicate nil isocyanates detected in the air (but that could just be that the iso's evaporate a while after the application).

Any help appreciated.

I think that the first thing is to understand tat the isocyanates are not separate, i.e. they're mixed in with the hardener which is then mixed with the paint base (2K, acrylic or urethane). Thus, the whole mixture that you're spraying contains isocyanates, including any overspray.

A filter on your exhaust will capture usually the larger droplets and any metallic or pearl flakes floating in the air stream, but vapours containing isocyanates will still pass through.
Some, top end booths then have a water wash system which captures most of the vapour. Not that you'd want to breathe this, but our regulations here require that the exhaust flue be at least 3m higher than the highest point on the roof and by the time it goes up there and mixes with whatever wind there is, the danger to people on the ground is minimal. If you wanted to clean your exhaust to breathable standards then you'd have to pass it through an activated charcoal filter. Nice idea but activated charcoal is both expensive and doesn't last long with the volumes being pushed through by a booth exhaust fan.

I don't think I'd place a lot of faith in a statement that brushing or rolling 2K paints results in nil iso content in the air. Even mixing the paint can be dangerous, which is why mixing rooms have exhaust fans and best practice is to wear at least a mask when mixing these paints.

Appreciate the reply mate.

Do you know if spraying Epoxy primer at a residential premises is illegal in Australia? It must be legal to brush / roll given the 2 part epoxy flooring products available for home use.

I see Eastwood sell a roll on epoxy primer for auto use.

Epoxy primer does not contain isocyanate. Still need a mask, but not the same danger/risk as 2K paint.

Depending where you live, painting in residential areas is permitted in some places, not in others. In the ACT I can paint 2K products so long as I have a booth that meets the minimum standards. Note that there are differing standards for a spray enclosure and a paint booth. A spray enclosure can have a limit on volume (3 panels/day) while, here in the nation's capital, we can paint as much as we like in the back yard, so long as it's in a booth and does not create more than 5 traffic movements per day in the street.