Polyurethane glue is very strong glue that hardens within minutes. Once dried, it is very difficult to take it off any surface including vinyl. Removing this glue requires immense patience and physical labor, as it needs to be done manually and takes very long.
Step 1 - Removing
Ensure you wear gloves to protect your skin. Put some soap or nail polish remover and warm water on the glue to slacken it lightly. Use the scraper to remove the glue from the edge and push the blade between the glue and flooring. Continue doing so using the rubber mallet if the glue is still challenging.
Step 2 - Scraping
Lift the scraper slightly to remove the glue from the vinyl surface. Twist the handle of the scraper back and forth to further push in. This would break the strong bond between the vinyl and the polyurethane. Finally, use a fine-grained sand paper to remove all glue snippets.
Step 3 - Finishing Up
Make sure you wear cushioned kneepads if you will be scraping for very long. This will save your knees from the pain that can be caused. Once the glue is removed from the vinyl, it may cause slight discoloration. Also, if using acetone, ensure the room is purely ventilated, as the fumes can be harmful. Moreover, vinyl must be scraped lightly and slowly as it is delicate and can be easily scratched.