The company can certainly make claim to almost anything arising out of your employment even if you are doing it on your "own time" (which doesn't really exist for an exempt employee). If you want to guard some independent intellectual property while working a day job, you'd best get an agreement with your employer in advance. We always had sweeping IP employment agreements like the above. I had one employee who designed racing boat hulls on his own time. We wrote a specific exception in to the agreement for him.

