So it seems that to become a Daemon Prince one must have the patronage of one of the Chaos gods to elevate you to that status. Of all the Daemon primarchs most are obvious except for two, Lorgar and Perturabo.
Angron - Khorne
Magnus - Tzeentch
Fulgrim - Slaanesh
Mortarion - Nurgle
Lorgar - ???? its a mystery. all of the above?
I can see why Lorgar might be a special case and may have been granted Daemon status through the patronage of all four gods, but I really don't see that happening for Perterabo. After reading the the blurb of background in the new codex about Perturabo invoking Nurgle it made me think could Nurgle be his patron? but displayed in a very different way than mortarion. More of a corrupter of the machine rather than flesh. In the blurb Perterabo with Nurgles help essentially creates a computer virus that infects an entire forgeworld turning its machines and factories into living daemon engines. And in older background it is also strongly hinted that Perturabo had a hand in creating the obliterator virus.