I want to use comic book heroes in a line of paintings I am making,
what is the copyright protection on those images? If it is a satire am
I protected?

Comic book characters fall under several copyright and trademark and
unfair competition categories. Owners do this in order to provide
themselves with as wide a protection as possible.

In your case you said " a line of paintings" which implies paintings
that will be sold for commercial gain. You cannot do that without the
copyright / trademark owner's permission and anyone who distributes
such a work would be liable for penalties as well. If the paintings
are for your own benefit there is no problem.

Satire can be fair comment but once again if you are offering the
paintings for sale, you must get permission The more valuable the
copyright / trademark the less likely you will receive such
permission. If your satire is commentary upon a social situation and
not on the hero characters themselves, you might consider creating
your own hero characters for the commentary. It would be a more
valuable enterprise in the long run.