WO2002074351A1

WO2002074351A1 - Method for the sterilisation of containers

Info

Publication number: WO2002074351A1
Application number: PCT/EP2002/002268
Authority: WO
Inventors: Robert Frost; Peter Awakowicz; Werner Stahlecker
Original assignee: Rüdiger Haaga GmbH
Priority date: 2001-03-20
Filing date: 2002-03-02
Publication date: 2002-09-26
Also published as: JP4162208B2; JP2008133054A; JP4914971B2; CN1498119A; CN100408105C; JP2004528886A; DE10114758B4; DE10114758A1

Abstract

A method for the sterilisation of a group of containers comprises carrying out the following method steps: introduction of the group of containers into an open sterilisation chamber, hermetic sealing of the sterilisation chamber, pre-evacuation of the sterilisation chamber, injection of a vapour mixture containing steam and hydrogen peroxide vapour into the sterilisation chamber, condensation of the vapour mixture on the surfaces of the containers, removal of the condensate thus formed by evacuation of the sterilisation chamber, flushing the sterilisation chamber with a sterile gas, opening the sterilisation chamber and removal of the group of containers from the sterilisation chamber.

Description

Process for sterilizing containers

The invention relates to a method for sterilizing a group of containers located in an evacuable sterilization chamber.

A method of this type, but with method steps which differ as a result, is prior art, for example, from DE 44 08 301 A1. The known method is carried out in a sterilization chamber, which is part of a so-called linear filler, in which the containers to be filled run straight through the machine system. During the sterilization, a group of, for example, six containers is simultaneously in a sterilization chamber. All containers in the group are therefore at the same position in the relevant process cycle at all times. The machine system works discontinuously. The sterilization itself is carried out by means of a low-temperature plasma generated in the sterilization chamber.

It has been shown that such a plasma sterilization requires relatively long cycle times if it is to be thorough, and that there are always areas on the containers as well as on the walls of the sterilization chamber itself where the sterilization is insufficient. The efficiency of the known method is therefore unsatisfactory.

The invention is based on the object, in a basic method of the type mentioned, but without the low-temperature plasma used for sterilization, to show a method with which such cyclically operating linear fillers work with much better efficiency during sterilization. The object is achieved in that the following procedural steps are carried out in succession:

Introduction of the group of containers into the open sterilization chamber,

- Hermetic sealing of the sterilization chamber,

- pre-evacuation of the sterilization chamber to a pressure below 500 mb,

Feeding a steam mixture containing water vapor and hydrogen peroxide vapor into the sterilization chamber,

Allowing the steam mixture to condense on the surfaces of the containers,

Removing the condensate formed by evacuating the sterilization chamber to a pressure at which the two components of the condensate evaporate,

Flooding the sterilization chamber with a sterile gas,

- opening the sterilization chamber and

- Remove the group of containers from the sterilization chamber.

When sterilizing using hydrogen peroxide, which is always present in aqueous solution, the actual germ killing takes place purely chemically, through the action of “activated” hydrogen peroxide. The term “activating” used here is undefined per se, but it has been found that by suitable heat supply A chemical and / or physical change takes place on the hydrogen peroxide, which ultimately causes the germs to be killed.

In the method according to the invention, the “activation” of the hydrogen peroxide takes place precisely when it is needed for sterilization, so with the condensation. The subsequent removal of the hydrogen peroxide residues is carried out by merely evacuating to a pressure at which the components of the condensate evaporate, which is possible in a matter of seconds and safely removes all hydrogen peroxide residues.

The steam mixture of water vapor and hydrogen peroxide vapor required for sterilization is generated in an evaporator, the design of which is arbitrary per se for the present invention, provided that it is capable of producing a sufficiently large amount of steam with a sufficiently high concentration of hydrogen peroxide vapor in the steam mixture in a sufficiently short time to create. The actual "activation" of the hydrogen peroxide contained in the steam mixture then takes place during condensation on the surfaces to be sterilized. This causes the steam mixture to wet the surfaces with the thinnest possible homogeneous liquid film. Due to the small layer thickness, it does not occur during the subsequent drying by evacuation to any signs of icing.

The applicant suspects that the "activation" of the hydrogen peroxide is caused by the enthalpy of vaporization released during the condensation. The enthalpy of vaporization released during the condensation provides the energy required to be able to dissociate a hydrogen peroxide molecule in such a way that an oxygen atom is released chemically highly reactive atomic oxygen responsible for the germicidal effect.

The temperature of the steam mixture, the pressure of the steam mixture before it flows into the sterilization chamber and the pressure in the sterilization chamber at which the condensation takes place are available to influence the sterilization effect. The condensation pressure should definitely be below 500 mb, preferably wise in a range of 250 to 150 mb. The pressure required to remove the condensate should be below 4 mb.

Since the pre-evacuation for introducing the steam mixture and the later evacuation for removing the condensate take place at different times in the same sterilization chamber, a pumping station consisting of a rotary vane pump and a subsequent Roots pump can be used for both process steps for evacuating the sterilization chamber, although the Roots pump during the pre-evacuation is appropriately avoided by a bypass. This prevents the Roots pump from being exposed to an excessively high pressure difference.

In particular, if the sterilization chamber exceeds a certain volume, it is provided in a further embodiment of the invention that the steam mixture to be fed into the sterilization chamber and / or the sterile gas required for flooding the sterilization chamber are in each case kept in a store upstream of the sterilization chamber and the relevant store during the Process steps in which the memory is not required are replenished. This ensures that both the required steam mixture and the sterile gas required in a later process step are available in sufficient quantities within a very short time. In addition, the required throughput of the evaporator or sterile filter is lower, since a relatively long time is available to fill the storage.

In particular for the storage containing sterile gas, it is important that a prescribable pressure is built up there, which determines the final pressure to be expected in the sterilization chamber. In this way, the final pressure of the sterilization chamber can be determined very precisely, although due to the sudden nature of the flooding, the pressure in the sterilization chamber pressure during flooding cannot be regulated well. At the moment of opening the sterilization chamber, there should be a slight overpressure of about 0.2 to 0.8 mb, so that non-sterile ambient air does not reach the already sterilized containers in this critical phase.

The invention is explained in more detail below with the aid of schematic drawings.

Show it:

FIG. 1 shows a plan view of a sterilization chamber and the way in which a group of containers is fed and removed,

FIG. 2 shows a diagram for explaining the individual method steps,

Figure 3 is a diagram for explaining the functional elements required for the inventive method.

The very schematic FIG. 1 shows a section of a machine system in the area of a sterilization chamber 1. The machine system is a clocked, linear machine network that integrates the sterilization chamber 1 and a filling and closing device in a single frame and for small and medium-sized ones Outputs of around 12,000 containers per hour, for example.

According to this FIG. 1, in a first cycle a conveyor belt 2 brings a group of containers 3 laterally next to the sterilization chamber 1 in the feed direction A. In the present case, the group contains a total of ten containers 3. In a subsequent cycle, the containers next to the sterilization chamber 1 are placed on the conveyor belt 2 waiting The container 3 is simultaneously pushed into holders, not shown, of a lowered loading floor or the like, also not shown, which can then be moved upwards into the sterilization chamber 1. After the sterilization process has been completed, the loading floor is lowered again. In the following cycle, the now sterilized containers 4 are pulled out of the sterilization chamber 1 as a group and transferred to a conveyor belt 5. This leads the sterilized containers 4 in the transport direction B into a filling device which has as many filling stations as the sterilization chamber 1 has container positions. In further cycles, the sterilized containers 4 can then in turn be pushed and filled simultaneously by parallel displacement under the filling valves. Finally, in a further cycle, the filled containers are pushed out of the filling devices onto an opposite conveyor belt, which then moves the containers to a closing station.

However, the present invention relates exclusively to the process steps that take place in the area of the sterilization chamber 1.

The chronological sequence of the sterilization process in the sterilization chamber 1 is shown as a diagram in FIG. 2, the abscissa indicating the time t in seconds [s] and the ordinate indicating the respective pressure P in millibars [mb] prevailing in the sterilization chamber 1. Curve 6 of the diagram shown in FIG. 2 thus shows the pressure curve over time.

In a first method step (a), the containers 3 provided in a group are introduced into the sterilization chamber 1, which takes place at atmospheric pressure (1000 mb). In the next process step (b), the sterilization chamber 1 is then hermetically sealed. The closing time takes about 0.7 seconds. During a further process step (c), the sterilization chamber 1 is evacuated to a pressure of less than 400 mb, preferably to about 150 mb, that is to say a pressure which allows a subsequently flowing steam mixture of water vapor and hydrogen peroxide vapor to reach the Surfaces of the container 3 can condense. Pre-evacuation takes about 0.8 seconds.

For the admission of the steam mixture into the pre-evacuated sterilization chamber 1, approximately 0.6 seconds are provided according to method step (d). The subsequent condensation corresponding to process step (e) takes about 0.8 seconds, depending on the selected boundary conditions. During this time, the "activation" of the hydrogen peroxide, which has already been explained, takes place, which leads to extremely rapid and thorough sterilization. The pressure in the sterilization chamber rises again slightly as shown in FIG. 2 as the steam mixture is admitted.

In a further process step (f), the condensate must now be removed from the sterilized containers 4, which is done by evacuating the sterilization chamber 1 to a pressure below the current boiling points of water and hydrogen peroxide. It has been shown that the final pressure of process step (f) should be slightly below 4 mb. This is the most time-consuming phase of the sterilization process, which takes about 3.4 seconds.

After the condensate has been drawn off, the sterilization chamber 1 is suddenly flooded with a sterile gas, for example sterile air or sterile nitrogen, within 0.5 seconds. This takes place during process step (g), after which a pressure is reached which is approximately 0.3 mb above the atmospheric pressure prevailing on the outside of the machine system. In further process steps (h) and (i) Finally, the sterilization chamber 1 is opened, the sterilized containers 4 are released and transferred from the opened sterilization chamber 1 to the conveyor belt 5.

The total effort of the sterilization process, including loading and unloading the sterilization chamber 1, is approximately 10.8 seconds.

FIG. 3 schematically shows the interaction of the functional elements assigned to the sterilization chamber 1, with the aid of which the containers 3 are to be sterilized.

In the case of the cyclically operating machine system, process steps (c) and (f) take place at different times, and therefore a common pumping station 7 can be used for both process steps. The pumping station 7 consists of a rotary vane pump 8 and a Roots pump 9.

Since there are very different pressure conditions during process steps (c) and (f), the gas stream of process step (c) can be bypassed the Roots pump 9 via a controllable valve 10 by means of a bypass 11 and this Roots pump 9 can be short-circuited in terms of pressure, so to speak. The pre-evacuation phase (c) is handled by the rotary vane pump 8 alone.

If a gas buffer 12 is additionally provided, which can be opened via a controllable valve 13, this can be flooded at the beginning of phase (c), as a result of which a large amount of the gas flows suddenly from the sterilization chamber 1 into this pre-evacuated volume and not from that Rotary vane pump 8 needs to be promoted. The rotary vane pump 8 could then be made smaller. The filled gas buffer 12 could then during process steps (a), (b), (g), (h) and (i) are evacuated again, i.e. in the phases during which no pump power is otherwise requested.

The steam mixture which is required during process step (d) and consists of water vapor and hydrogen peroxide vapor is generated by an evaporator 14 during the remaining phases and is kept available in a store 15 heated to at least 100 °. The steam mixture flows into the sterilization chamber 1 by briefly opening several likewise heated valves 16. The number of valves 16 is intended to ensure that the steam mixture flows uniformly into the sterilization chamber 1. Nozzles 17 are provided on the sterilization chamber 1, through which the steam mixture flows into the sterilization chamber 1 and which ensure a suitable spatial distribution of the inflow and a suitable inflow speed.

The aqueous hydrogen peroxide solution is fed to the evaporator 14 in the direction of arrow C via a valve 18. A valve 19 enables the evaporator 14 to be shut off from the store 15 if necessary. Another valve 20 enables the storage 15 to be evacuated via a line 21. At the start of operation, air can thus be removed from the storage 15. In addition, a cyclical pressure reduction in the memory 15 can also be carried out, if necessary. This could be necessary if, after the steam mixture flows into the sterilization chamber 1, an excessively high residual pressure remains in the accumulator 15.

In larger systems, it can be useful if several evaporators 14 feed a common storage 15. The memory 15 has a temperature sensor 25 and a pressure sensor 26 for controlling the process and for monitoring the proper functioning. The residue-free removal of the condensate during process step (f) is monitored by means of a pressure sensor 22. If the pressure falls below a limit of around 3.8 mb, pump valves are activated

23 is closed, and a sterile gas is flooded into the sterilization chamber 1 via the flood valves 24 until the external pressure is reached. Only then can the sterilization chamber 1 be opened. There are several flood valves for even distribution of the flood gas in the sterilization chamber 1 and for avoiding unfavorable flow conditions

24 provided. For the same reason there are also two pump valves 23.

During process step (g), a quantity of gas of about 130 normal liters is required for flooding within about 0.5 seconds. This number of normal liters corresponds to the volume of the sterilization chamber 1. Such a gas stream cannot be passed through a sterile filter during flooding, since such a flow would be too large. For this reason, a further store 27 is provided, which during the remaining process phases is continuously pre-filled with pressurized air or pressurized nitrogen via a sterile filter 28 and a shut-off valve 29 with sterile gas fed.

Because of the sudden flooding, the pressure generated in the sterilization chamber 1 can practically not be regulated. With known volume ratios, as is the case here, however, the pressure that arises in the sterilization chamber 1 can be precisely determined by building up a very specific pressure in the accumulator 27 before flooding. After the pressure equalization, this pressure determines the final pressure to be expected in the accumulator 27. For this purpose, a very precisely working pressure sensor 30 is provided. Before opening the sterilization chamber 1, the pressure in the sterilization chamber 1 must correspond very precisely to the outside pressure of the machine system and have a slight overpressure of approx. 0.3 mb, so that no harmful flows resulting from pressure differences enter the inside of the sterilization chamber 1. The entry of contaminated air from the machine hall into the area of the machine system must be avoided in any case.

On the one hand, the volume of the storage 27 for the sterile gas should be as small as possible so that space is saved. On the other hand, however, the pressure required should only be so high that the accuracy of the flooding to the level of the external pressure is not impaired. A good compromise is between 1.5 and 2.5 bar. This results in a storage volume that corresponds to approximately 1.5 to 2 times the volume of the sterilization chamber 1. With the arrangement mentioned, de-oiled and dried compressed air removed from the line can be used for this purpose.

Claims

claims

1. A method for sterilizing a group of containers located in an evacuable sterilization chamber, characterized by the following method steps:

(a) placing the group of containers in the opened sterilization chamber,

(b) hermetically sealing the sterilization chamber,

(c) pre-evacuating the sterilization chamber to a pressure below 500 mb,

(d) feeding a steam mixture containing water vapor and hydrogen peroxide vapor into the sterilization chamber,

(e) allowing the vapor mixture to condense on the surfaces of the containers,

(f) removing the condensate formed by evacuating the sterilization chamber onto one

Pressure at which the two components of the condensate evaporate,

(g) flooding the sterilization chamber with a sterile gas, (h) opening the sterilization chamber and

(i) removing the group of containers from the sterilization chamber.

2. The method according to claim 1, characterized in that the sterilization chamber is evacuated to a pressure of about 4 mb to remove the condensate.

3. The method according to claim 1 or 2, characterized in that a pumping station consisting of a rotary pump and a Roots pump is used to evacuate the sterilization chamber, the Roots pump being bypassed during the pre-evacuation.

4. The method according to any one of claims 1 to 3, characterized in that the steam mixture to be fed into the sterilization chamber and / or the sterile gas required for flooding the sterilization chamber are each available in a storage upstream of the sterilization chamber and the relevant storage during the process steps in which it is not needed, is replenished.

5. The method according to claim 4, characterized in that a presettable pressure is built up in the storage containing sterile gas, which determines the expected final pressure in the sterilization chamber.

6. The method according to claim 5, characterized in that there is a slight excess pressure of about 0.2 to 0.8 mb in the sterilization chamber when it is opened.