A horizontal mixer for mixing and processing materials includes a horizontally disposed mixing chamber and an elongated rotatable mixing shaft extending longitudinally through the chamber. The drive apparatus is coupled to a drive of the mixing shaft to rotate the shaft and mix material placed in the chamber. A stub end of the shaft has a bearing portion extending through an end wall of the chamber opposite the drive end of the shaft. The bearing portion engages a sleeve bearing which is operable for rotatably supporting the stub end proximate the end wall opening. A sealing shroud is coupled proximate the sleeve bearing and covers an outer portion of the shaft stub end. A static shroud seal is coupled with the sealing shroud at an interface between the shroud and the sleeve bearing. The static shroud is maintained out of direct contact with the rotatable shaft stub end. The sealing shroud and static shroud effectively isolate the shaft stub such that leakage between the chamber and the outside atmosphere is generally prevented.