The Blackhawks announced the moves on Tuesday.
Montador was placed on waivers on Monday and cleared them, meaning the team retained his rights He has appeared in only one game since he suffered a concussion in February 2012 and that was in late March. He has not played this season.
Hayes has 22 goals and 17 assists for Rockford.
The Blackhawks set an NHL record by collecting at least one point in the first 24 games. That streak ended with a loss to Colorado on Friday, and they fell again to Edmonton on Sunday. Chicago's next game is Thursday at Columbus.