Method of sterilizing a package

Abstract

A method of sterilizing packages in production of the packages, wherein the packages have an open end and a closed end. A gaseous sterilizing agent is used and kept in the gaseous phase throughout the sterilization process and an ambient temperature and a concentration of sterilizing agent in a sterilization zone where sterilization is performed are measured and used for controlling the amount of sterilizing agent introduced in the sterilization zone.

1 . A method of sterilizing a package during production of the package, the package comprising an open end and a closed end, the method comprising: sterilizing the package in a sterilization zone using a gaseous sterilizing agent which is maintained in the gaseous phase throughout the sterilizing; measuring a relative humidity outside the sterilization zone where the sterilizing agent does not flow; measuring ambient temperature outside the sterilization zone; measuring a concentration of the sterilizing agent in the sterilization zone where sterilization is performed; and controlling an amount of sterilizing agent introduced into the sterilization zone based on the measured ambient temperature, the measured relative humidity, and the measured concentration of the sterilizing agent. 
     
     
         2 . A method as claimed in  claim 1 , further comprising introducing the gaseous sterilizing agent in a top portion of the sterilization zone, and withdrawing the gaseous sterilizing agent from a bottom portion of the sterilization zone. 
     
     
         3 . A method as claimed in  claim 1 , further comprising introducing sterile air in a top portion of a venting zone, and withdrawing the sterile air from a bottom of the venting zone. 
     
     
         4 . A method of sterilizing a package during production of the package, the package comprising an open end and a closed end, the method comprising: sterilizing the package in a sterilization zone using a gaseous sterilizing agent which is maintained in the gaseous phase throughout the sterilizings; measuring ambient temperature and a concentration of the sterilizing agent in the sterilization zone where sterilization is performed; and
 controlling an amount of sterilizing agent introduced in the sterilization zone based on the measured ambient temperature and the concentration of the sterilizing agent in the sterilization zone.   
     
     
         5 . A method as claimed in  claim 4 , further comprising using the measured ambient temperature to control the heating in a heating zone where heating of the package is performed. 
     
     
         6 . A method as claimed in  claim 4 , further comprising measuring a temperature of the package entering the heating zone is measured and used for controlling the heating in the heating zone. 
     
     
         7 . A method as claimed in  claim 4 , further comprising measuring a temperature of the package just before the package is passed into the sterilization zone, and controlling the heating in the heating zone by taking into account the measured temperature of the package. 
     
     
         8 . A method as claimed in  claim 4 , further comprising maintaining a positive pressure in the sterilization zone in which the sterilization is performed. 
     
     
         9 . A method as claimed in  claim 4 , further comprising passing the package into the heating zone where the package is heated to a temperature above the dew point of the sterilizing agent. 
     
     
         10 . A method as claimed in  claim 9 , further comprising passing the heated package through an opening in a partition and into the sterilization zone where they are subjected to the gaseous sterilizing agent, the partition separating the heating zone and the sterilization zone. 
     
     
         11 . A method as claimed in  claim 10 , further comprising passing the sterilized packages through an opening in a partition and into a venting zone where the package is subjected to hot sterile air for venting away the sterilizing agent, the partition separating the sterilization zone and the venting zone. 
     
     
         12 . A method as claimed in  claim 10 , wherein the gaseous sterilizing agent in the sterilization zone flows essentially in a direction from the open end of the packages towards the closed end of the packages. 
     
     
         13 . A method as claimed in  claim 12 , further comprising introducing the gaseous sterilizing agent in a top portion of the sterilization zone and evacuating the sterilizing agent in a bottom portion of the sterilization zone to maintain an essentially top to bottom flow of the sterilizing agent. 
     
     
         14 . A method as claimed in  claim 11 , wherein the venting air in the venting zone flows essentially in a direction from the open end of the packages towards the closed end of the packages. 
     
     
         15 . A method as claimed in  claim 14 , further comprising introducing the venting air in a top portion of the venting zone and evacuating the venting air in a bottom portion of the venting zone to maintain an essentially top to bottom air flow. 
     
     
         16 . A method as claimed in  claim 4 , further comprising producing the gaseous sterilizing agent by adding liquid sterilizing agent to hot air. 
     
     
         17 . A method as claimed in  claim 16 , further comprising controlling the temperature and flow of air for production of the gaseous sterilizing agent based on detection of condensation in the sterilization zone. 
     
     
         18 . A method as claimed in  claim 4 , wherein gaseous hydrogen peroxide is used as sterilizing agent. 
     
     
         19 . A method as claimed in  claim 11 , wherein a higher pressure is maintained in a filling zone for filling vented packages than in the venting zone.