It should be safe to process, but it is critical that you vent the fumes from both machines to prevent corrosion of your equipment. You should also take the time to educate your employees on the dangers of combining these materials.

It is critical that you create a system to prevent any chance of cross contamination. This may be as simple as a color-coded system so that the color of the container matches a panel next to the machine. Personally, I would create a fool-proof system where the container for VC is not compatible with the acetal material delivery system and vice-versa.

-Andy