Unit for sterilizing web-fed material on a machine for packaging pourable food products

A unit for sterilizing a web ( 2 ) of packaging material on a machine ( 1 ) for packaging pourable food products, the unit having a bath ( 7 ) containing a sterilizing agent, in which the web ( 2 ) is fed continuously; a process chamber ( 8 ) connected to an outlet ( 12 ) of the bath ( 7 ), and which houses wringing rollers ( 18 ) interacting with the web ( 2 ), and a nozzle ( 22 ) for directing a stream of air on to the web ( 2 ) and removing residual sterilizing agent from the web; an aseptic chamber ( 25 ) communicating with the process chamber ( 8 ) via an opening ( 27 ) for passage of the web ( 2 ), and in which the web ( 2 ) is folded and sealed longitudinally to form a tube ( 29 ) which is filled continuously with the product for packaging; and an air processing circuit ( 24 ) for controlling process conditions, and having a conduit ( 56 ) for feeding a first stream of sterile air into the aseptic chamber ( 25 ), a conduit ( 54 ) for feeding a second stream of sterile air to the nozzle ( 22 ) and housing a heater ( 69 ) for controlling the temperature of the air supplied to the nozzle ( 22 ), and a distributor for regulating the two streams of air.