Once any urethane adhesive has cured, it is extremely difficult to remove without damaging the surface beneath or whatever it encapsulates. It is important that if you spill urethane adhesive that you remove excess as quickly as possible before it completely dries. Here are a few things you can do to remove urethane from places you don't want it to be.
Apply either a specific urethane adhesive remover solution, mineral spirits or methyline chloride to the adhesive.
Make certain you totally cover all of the adhesive you are removing. Protect surrounding areas from spills and splashes to prevent places becoming unglued that you don't want to come unglued.
Allow the solution to sit for 15 minutes and soften the dried adhesive.
Wipe the spot with a soft cloth to remove loosened adhesive. If the adhesive is not completely removed, repeat.
Gently work loose any remaining adhesive with a putty knife or flat scraper. Be careful not to damage the surface underneath. Wipe off the area with a cloth and warm water.
For More Durable Surfaces
Heat the adhesive with a propane torch until it softens. This way works best on metal and concrete, but cannot be done if the surface beneath the glue is fragile.
Insert a chisel or sharp faced tool to chip away the urethane once its temperature has been raised above the softening point.
Gently wipe down the area with a warm wet cloth to remove any loose residue.