EP0460380B1 - Method and device for the complete sterilisation of stacked packaging elements, especially plastic cups with different wall rigidities - Google Patents

Description

The invention initially relates to a method for all-round sterilization of stacked packaging elements, in particular cups made of plastic with different wall thicknesses, in a separate sterilization chamber on a filling and closing machine by means of a sterilizing agent.

From French patent application FR-A-2354102, a device for treating packaging elements, namely cups stacked one inside the other, has become known, which are subjected to a pretreatment before the actual sterilization. For this purpose, the stacked cups are passed through two treatment chambers, namely through the actual sterilization chamber and a pre-treatment chamber connected upstream of it. In the pretreatment chamber, for example, the air penetrating with the containers carried out can be exchanged for an atmosphere of certain moisture. It is also possible to remove a substantial part of the air brought in with the containers in the pretreatment chamber by evacuating and / or blowing in a protective gas. A treatment gas can be introduced into the second treatment chamber, ie the actual sterilization chamber, to sterilize the containers. This treatment chamber can also be heated to a certain temperature.

The preparation of the treatment rooms or the treatment of the packaging elements in the two treatment chambers each require certain treatment agents which have to be supplied via their own inflow lines. Such a procedure or such a device is quite complex and requires a comparatively large space requirement for the preparation, as well as the supply and discharge of the treatment agents.

When packaging sterilized filling products in aseptic packaging under aseptic conditions, care must be taken to ensure that by sterilizing the packaging, e.g. B. existing plastic cups for receiving liquid or pasty goods such. As milk, yogurt, whipped cream, instant soups, etc. on the one hand achieves the desired or necessary disinfection effect and the sterilizing agent applied as a film to the inner and outer walls of the cup is completely removed from the cup surface and that on the other hand heat damage to the cup is avoided.

When sterilizing with hydrogen peroxide (H2O2), the strong oxidizing effect of a concentrated hydrogen peroxide solution (35% concentration) is used at elevated temperature (60 ° C to 80 ° C), whereby even resistant microorganisms (Bacillus spores) can be killed within seconds becomes. For aseptic filling of neutral contents, a reduction rate of resistant germs (Bacillus subtilis spores) by at least four powers of ten is considered necessary for packaging with a content of up to 2 l.

It is known that there is a dependency between the germicidal effect of hydrogen peroxide and its concentration and the temperature of the H2O2 solutions. The microbicidal effect of hydrogen peroxide increases with increasing concentration. Finally, the germicidal effect of hydrogen peroxide solutions can be significantly improved by increasing the temperature.

The so-called D-value (decimal reduction time) is used as a measure of the killing effect of microorganisms. This value indicates the time in minutes that is required to kill 90% of the existing microbial population at constant temperature. The stubborn spore-forming agents can only be killed in a matter of seconds, as is required in aseptic systems, if minimum temperatures of 80 ° C to 90 ° C are used at H2O2 concentrations of around 30% and beyond.

At the international level, e.g. B. by the American FDA strict guidelines regarding the killing effect and the unsterility rate were required. To meet these requirements, it would be very easy to raise the temperature of the H2O2 solution for the purpose of further killing. Compared to the treatment of foils as packaging, the disinfection of containers, especially if they are made of plastic, is not so easy. Prefabricated plastic cups naturally require stacking elements that are created by ribs, undercuts, raised floors, etc. These areas require a long-lasting and high heat exposure for an effective killing effect, whereas the comparatively thin walls of the container cannot withstand such an action or are deformed or damaged.

Because of this problem, the considerations leading to the invention are based on the knowledge that the bacterial load on the packaging material is of great importance. the lower the bacterial count on the surface of the packaging, the easier it is to sterilize.

The invention is therefore based on the object of proposing a method suitable for all-round sterilization of stacked packaging elements, in particular cups made of plastic with different wall thicknesses, by means of which a sterilization which meets the strict requirements is made possible in a simple and, above all, economical manner, without this Packaging is impaired and / or the residual removal of the sterilizing agent is difficult. At the same time, a device is to be created which enables the task to be solved with the least construction effort and in the smallest of spaces.

In procedural terms, this object is achieved according to the invention in that the sterilization chamber is connected to the pre-treatment chamber (pre-sterilization chamber) via an outflow line through which H2O2-containing air is transferred from a mixture of sterilizing agent and sterile hot air from the sterilization chamber to the pre-treatment chamber (pre-sterilization chamber) can.

With the means according to the invention, an effective all-round sterilization of stacked packaging elements, in particular cups made of plastic with different wall thicknesses, is easily achieved. The process is not only characterized by a good sterilizing effect, but also by an economical energy supply. This is due to the fact that the mixture of sterilizing agent and hot air discharged from the sterilizing chamber is optimally used in the pre-sterilizing chamber for pre-sterilizing the packaging elements. The returned air containing H2O2 should still have a concentration of 2000 to 2500 ppm. Experiments carried out have shown that the temperature of the air containing H2O2 should be at least 90 ° C. and that the packaging elements should be pre-sterilized for at least 30 seconds.

It is easiest if the air containing H2O2 is extracted from the pre-sterilization chamber.

A device suitable for carrying out the method according to the invention for all-round sterilization of stacked packaging elements, in particular cups made of plastic with different wall thicknesses, consists of a separate sterilizing device arranged on a filling and closing machine with two treatment chambers, the first of which as a pre-treatment chamber provided with an inlet and outlet and the second, as also provided with an inlet and an outlet sterilizing chamber for the packaging elements, to which the packaging elements are transferred from the pretreatment chamber for the purpose of sterilizing with a sterilizing agent, the sterilizing chamber with the Pre-treatment chamber (pre-sterilization chamber) is connected via an outflow line, through which air containing H2O2 can be transferred from a mixture of sterilizing agent and sterile hot air from the sterilization chamber to the pre-treatment chamber (pre-sterilization chamber).

In this way you get a particularly simple complete unit that can be attached to a filling and closing machine in a very small space.

A particularly economical procedure results if a suction line is connected to the pre-sterilization chamber and if the outflow line and the suction line also open out on opposite sides of the pre-sterilization chamber. This results in a good and uniform flow through the pre-sterilization chamber, so that the containers located therein are well washed around on all sides.

The same purpose also contributes if the sterilization chamber and / or the pre-sterilization chamber has a distribution chamber delimited by intermediate walls provided with through openings, in the area of which the connection points for the outflow line and the suction line are arranged.

Furthermore, it is advantageous if the through openings of the intermediate walls are directed obliquely downwards towards the interior of the cups or the like, at least on the respective inflow side. This also ensures a good distribution of the H2O2 sterilizing agent or the air containing H2O2.

For good distribution, it is furthermore advantageous if baffle plates provided with through openings are arranged on the inflow sides in the region of the distribution chambers of the sterilization chamber and the pre-sterilization chamber and if finally the inflow sides of the sterilization chamber and the pre-sterilization chamber are arranged on essentially diametrically opposite sides.

As such, it does not matter where the pre-sterilization chamber is located. For structural reasons, however, it is advisable to arrange the pre-sterilization chamber above the sterilization chamber. This also makes it considerably easier to appropriately design transport means arranged in the sterilization chamber and the pre-sterilization chamber. Continuous screw conveyors with the same or expediently different division in the sterilization chamber and the pre-sterilization chamber are suitable as means of transport, for example.

It goes without saying that several sterilization and pre-sterilization chambers can also be arranged in rows next to one another and are connected to the outflow line and the suction line via a suitable line system.

Fig.1

Eine Sterilisiervorrichtung mit Sterilisier- und Vorsterilisierkammer für gestapelte Becher,

Fig.2

eine schematische Aufsicht mit einer teilweisen Schnittdarstellung durch die Vorsterilisierkammer entlang der Linie II-II der Fig. 1,

Fig.3

eine der Fig. 2 entsprechende Darstellung durch die Sterilisierkammer entlang der Linie III-III der Fig. 1 und

Fig.4

ein Schaubild mit zwei Vergleichskurven für eine Sterilisation ohne und mit Vorsterilisation.

A preferred embodiment of the invention is shown in the drawing and is explained in more detail below. Show it:

Fig. 1

A sterilization device with a sterilization and pre-sterilization chamber for stacked cups,

Fig. 2

2 shows a schematic plan view with a partial sectional view through the pre-sterilization chamber along the line II-II of FIG. 1,

Fig. 3

a representation corresponding to FIG. 2 through the sterilization chamber along the line III-III of FIG. 1 and

Fig. 4

a diagram with two comparison curves for a sterilization without and with pre-sterilization.

A filling and closing machine, which is only indicated in FIG. 1, enables the packaging of sterilized filling products in aseptic packaging materials under aseptic conditions. As filling products, liquid and pasty foods come into question, such as. As milk, yogurt, whipped cream, ready-made soups etc. Pre-made cups 14 made of plastic are used as packaging. Basically, cups made of aluminum or composite materials are also possible. The cups have reinforced walls at the bottom, the corners and the edge compared to the side wall. The cups can be securely sealed with plastic lids or aluminum flat lids made of embossed film. A cup conveyor in the form of revolving transport chains is arranged within the housing 2 of the filling and closing machine, which is under sterile air pressure. The filling and closing machine also has a cup stacking and input station 4 with a sterilizing device 5. This has a sterilizing chamber 18 and a pre-sterilizing chamber 10, which is explained in more detail below.

The cup stacking and input station 4 has a stack magazine 13, in which the cups 14 to be sterilized are introduced directly against one another with their opening facing upwards. The pre-sterilization chamber 10 is arranged below the stack magazine 13, which can be formed, for example, by rods arranged at a distance from one another. It should be noted here that both the pre-sterilization chamber 10 and the sterilization chamber 18 are sealed at all points required to maintain a perfect sterilization effect. The sterilization chamber 18 with a housing 15, which has an outer wall 16 and intermediate walls 17, is located vertically below the pre-sterilization chamber 10 (see also FIG. 3). The actual sterilization chamber 18 is formed from the intermediate walls, through which the cups 14 are guided in a manner described in more detail below. After the cup 14 has passed through, it is gripped by means of a gripper (not shown) or a suction element and suspended in cell sheets 19 of the chain conveyor. The chain conveyor can be moved gradually in the direction of arrow 21. The sterilization chamber 18 has an inlet opening 22 and an outlet opening 23 for the entry and exit of the cups. Furthermore, the sterilization chamber 18 has an inlet 24 for a sterilizing agent, such as, for. B. a 35% H2O2 vapor mixture that can be entered via a two-substance nozzle 25 and a heating chamber 30 '. The H2O2 vapor mixture applied to the beakers in the manner described in more detail below is distributed over these as a condensate film. The subsequent drying of the cups is carried out with sterile, about 200 ° C hot air, which is introduced via an inlet 26. The inlet 26 communicates with a distributor chamber 27 in which there is a baffle plate 28 provided with through openings 30. This ensures a good distribution of the hot air. The sterile hot air enters the sterilizing chamber 18 from the distribution chamber 27 via downward-directed through bores 29 in the intermediate wall 17 on the inflow side. The hot air splits the H2O2 into atomic oxygen and water. The residual amount of peroxide in vapor form is sucked out of the sterilization chamber 18 in a targeted manner, and via an outflow line 31 and via a suction line 32 connected to the pre-sterilization chamber 10, in which a suction fan 6 is installed.

Although only one sterilization chamber 18 and one pre-sterilization chamber 10 are shown in FIG. 1, a plurality of such chambers can also be arranged one behind the other, as is shown in FIGS. 2 and 3. In this case, the individual chambers are each connected to the inlet 24, the outflow line 31 and the suction line 32 via a correspondingly designed line system.

The pre-sterilization chamber 10 is also surrounded by a housing 7 which has an outer wall 8 and partitions 20. The intermediate wall 20 has through openings 20 ′ directed downwards on the inflow side and upwards on the outflow side. It should be noted here that in order to simplify the illustration in FIG. 1, only one intermediate wall is shown in each of the sterilization chamber 18 and the pre-sterilization chamber 10 in order to better show the flow conditions, as they are characterized by the arrows shown. The housing 7 of the pre-sterilization chamber 10 in turn has a distribution chamber 11, on the inflow side of which a baffle plate 12 provided with passage openings 12 'is arranged.

Air containing H2O2 at a temperature of at least 90 ° C. and a concentration of 2000 to 2500 ppm exiting from the sterilization chamber 18 via the outflow line 31 passes from the distribution chamber 11 through the through openings 20 ′ in the intermediate wall 20 of the pre-sterilization chamber 10 into the actual pre-sterilization chamber 10. The container 14, which has been pulled apart in the manner described in more detail below, is coated on all sides by the H2O2-containing air and is thus pre-sterilized. The pre-sterilization time should be at least 30 seconds.

The cups are conveyed through the pre-sterilization chamber 10 and the sterilization chamber 18 with the aid of screw conveyors 33. The screw conveyors 33 can be formed in one piece. The synchronously rotating screw conveyors 33 are driven via drive pinions 34 and a drive, not shown. In the area of the pre-sterilization chamber 10, the screw conveyors have a smaller pitch than in the area of the sterilization chamber, with the result that in the area of the pre-sterilization chamber the cups have a smaller mutual spacing than in the sterilization chamber. The ratio is preferably about 1: 2.

(1)

= Ohne Vorsterilisation (Keimreduktion = 4,02 log)

(2)

= Vorsterilisation (Keimreduktion = 2,3 log)

(2) + (3)

= Vorsterilisation mit nachfolgender Sterilisation (Keimreduktion = 5,75 log)

FIG. 4 shows a diagram with two comparative representations derived from tests for a typical sterilization process (Bacillus subtilis spores) without pre-sterilization and with pre-sterilization. The time in seconds for the sterilization or pre-sterilization is plotted on the abscissa and the germ reduction in log on the ordinate. The objects to be sterilized were plastic cups. A 35% H2O2 solution was used as the sterilizing agent. The designations (1), (2), (3) have the following meaning:

(1)

= Without pre-sterilization (germ reduction = 4.02 log)

(2)

= Pre-sterilization (germ reduction = 2.3 log)

(2) + (3)

= Pre-sterilization with subsequent sterilization (germ reduction = 5.75 log)

It goes without saying that the invention is not limited to the exemplary embodiment shown, but also allows modifications within the scope of the claims. So it is fundamentally conceivable that the pre-sterilization chamber 10 is also arranged laterally next to the sterilization chamber and that other suitable transport means, such as chains with grippers or the like, can be provided instead of the screw conveyors as a means of transport for moving the cups through the chambers.

Claims (18)

1. Method for the all-over sterilisation of stacked packing elements (14), particularly tubs made of plastics material and having different wall thicknesses, in a separate sterilisation chamber (18) in a filling and closing machine by means of a sterilising agent, characterised in that before entering the sterilisation chamber (18) and before the sterilisation effected therein with H₂O₂ vapour and hot sterile air, the packing elements (14) are presterilised by means of air containing H₂O₂ flowing out of the sterilisation chamber (18).
2. Method according to Claim 1, characterised in that the air containing H₂O₂ is drawn off by suction from the presterilisation chamber (18).
3. Method according to Claim 1 or 2, characterised in that the air containing H₂O₂ has a concentration of from 2000 to 2500 ppm.
4. Method according to one or more of Claims 1 to 3, characterised in that the temperature of the air containing H₂O₂ amounts to at least 90°C.
5. Method according to one or more of Claims 1 to 4, characterised in that the packing elements (14) are presterilised for at least 30 seconds.
6. Apparatus for the all-over sterilisation of stacked packing elements, particularly tubs made of plastics material and having different wall thicknesses, for carrying out the method according to one or more of Claims 1 to 5, consisting of a separate sterilising apparatus disposed in a filling and closing machine and comprising two treatment chambers (10, 18), the first of which is in the form of a pretreatment chamber (10) provided with an inlet and an outlet, while the second is in the form of a sterilisation chamber (18) which is likewise provided with an inlet and an outlet and to which the packing elements (14) are transferred from the pretreatment chamber (10) for the purpose of sterilisation by a sterilising agent, characterised in that the sterilisation chamber (18) is connected to the pretreatment chamber (presterilisation chamber 10) through a discharge pipe (31) through which air containing H₂O₂ from a mixture of sterilising agent and sterile hot air can be transferred from the sterilisation chamber (18) into the pretreatment chamber (presterilisation chamber 10).
7. Apparatus according to Claim 6, characterised in that a suction pipe (32) is connected to the presterilisation chamber.
8. Apparatus according to Claim 6 or 7, characterised in that the presterilisation chamber (10) is disposed above the sterilisation chamber (18).
9. Apparatus according to Claim 6 or 7, characterised in that the discharge pipe (31) and the suction pipe (32) lead substantially on opposite sides into the presterilisation chamber (10).
10. Apparatus according to one or more of Claims 6 to 9, characterised in that the sterilisation chamber (18) and/or the presterilisation chamber (10) has or have a distributor chamber (27, 11) which is bounded by partitions (17,20) provided with through-openings (29, 20') and in the region of which the connection points for the discharge pipe (31) and the suction pipe (32) are disposed.
11. Apparatus according to Claim 9, characterised in that the through-openings (29, 20') in the partitions (17, 20) are directed, at least on the respective inlet side, obliquely downwards towards the interior of the tubs or the like.
12. Apparatus according to one or more of Claims 6 to 10, characterised in that baffle plates (28, 12) provided with through-openings (30, 12') are disposed, on the inlet sides, in the region of the distributor chambers (27, 11) of the sterilisation chamber (18) and of the presterilisation chamber (10)
13. Apparatus according to one or more of Claims 6 to 11, characterised in that the inlet sides of the sterilisation chamber (18) and the presterilisation chamber (10) are disposed on substantially diametrically opposite sides.
14. Apparatus according to one or more of Claims 6 to 12, characterised in that the presterilisation chamber (10) is disposed above the sterilisation chamber (18).
15. Apparatus according to one or more of Claims 6 to 13, characterised by conveyor means, disposed in the sterilisation chamber (18) and in the presterilisation chamber (10), for the tubs (14)or the like.
16. Apparatus according to Claim 15, characterised in that the conveyor means in the presterilisation chamber (10) are disposed with their carriers, which transport the tubs (14) or the like, a shorter distance apart than in the sterilisation chamber (18).
17. Apparatus according to Claim 15, characterised in that the conveyor means are formed by conveyor worms (33) extending through the sterilisation chamber (18) and the presterilisation chamber (10).
18. Apparatus according to one or more of Claims 6 to 16, characterised in that a plurality of sterilisation chambers (18) and of presterilisation chambers (10) are disposed in respective rows side by side and are connected by a piping system to the discharge pipe (31) and the suction pipe (32).

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