EP1269150A1

EP1269150A1 - Method for measuring gas permeability of a coating on a plastic wall and device for implementing said method

Info

Publication number: EP1269150A1
Application number: EP01925443A
Authority: EP
Inventors: Dominique Chatard
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2000-03-15
Filing date: 2001-03-14
Publication date: 2003-01-02
Also published as: WO2001069201A1; DE10012446B4; US20030046982A1; AU2001252195A1; JP2003527595A; DE10012446A1; US6658919B2

Abstract

The invention concerns a method for measuring the permeability of a coating (3) on a plastic wall (1) to low molecular weight gases, wherein the diffusion coefficient and/or solubility coefficient of the coating (3) relative to the low molecular weight gases are lower than for instance those of the plastic wall (1), wherein the space (4) on the coating side is exposed to a first fluid (5) and is rinsed until only the first fluid (5) fills said space. The invention also concerns a device for implementing said method. In order to measure the barrier property of the coating (3), the first fluid is a test medium (5) containing a component that can be diffused in the plastic wall (1) and absorbed by said wall; after rinsing the space (4), the test medium (5) is removed therefrom; the coated space (4) is then exposed to an extraction medium (7) in which the component can be well dissolved and measured and the concentration of the component in the extraction medium (7) is measured.

Description

Method for measuring the gas permeability of a coating on a plastic wall and device for carrying out the method

The invention relates to a method for measuring the permeability of a coating on a plastic wall for low-molecular gases, for example oxygen, the diffusion coefficient and / or solubility coefficient of the coating with respect to the low-molecular gas being approximately one order of magnitude smaller than that of the plastic wall, in which the space on the coating side is acted upon by a first fluid and is flushed through until essentially only this first fluid is in the space mentioned.

It is known to produce liquid packs from plastic, for example in the form of bottles with an opening at the top. Such bottles are made of polyethylene terephthalate (PET) and are widely used for packaging, for example, water. It is known that the walls of the plastic packs are permeable to low-molecular gases, which is why the shelf life for liquid foods, in particular juices and mixed drinks containing CO ₂ , is limited. In order to prevent the oxygen responsible for this from penetrating and the carbon dioxide from escaping and to make such plastic packaging more suitable for liquid foods, various attempts have been made to coat the walls of these plastic packaging inside or outside. An example of such a known coating process for improving this so-called barrier property of plastic packages is the plasma-assisted coating from the gas phase (PECVD). In the case of the inner coating, a gas mixture is introduced into the package or the hollow body. Electromagnetic energy is radiated in, ignites the plasma, and, for example, a glass-like silicon oxide or an amorphous carbon layer is applied to the inside of the hollow body in this treatment process. Low-molecular gas, for example oxygen or carbon dioxide, can penetrate the plastic walls much less or not at all through this additional barrier, and also low-molecular organic compounds can no longer penetrate into the plastic, with the result that, in the case of packaged liquid foods, the beverages thereby their taste and quality can last much longer. However, there are various factors that cause the wall surface to have a different thickness, for example the different shape of the coated body. According to another known method, a piece of wall cut out of the bottle is used to measure by means of X-ray fluorescence whether an application has taken place. With this method, too, it is disadvantageously not possible to determine whether the application is homogeneously distributed over the surface and therefore the coating has a good barrier property. In addition, this elemental analysis can only be determined on a punched-out piece of the packing wall.

A further method has therefore been developed, according to which the barrier property of a coating on a plastic wall is measured with the aid of the oxygen diffusing through the wall and the coating. For example, an airborne package is purged with nitrogen on the inside for a day until the inside of the package is almost certainly free of oxygen, while a gas with 21% oxygen is present outside the package. If you leave the inner atmosphere of the hermetically sealed package with nitrogen after this flushing process, the oxygen which may accumulate over time comes from the surroundings of the package. This oxygen then migrated from the outside through the plastic wall to the inside. After a waiting period of at best about 24 hours (typically up to three weeks), a stationary end value of the oxygen content in the atmosphere inside the package has been established in this measuring method. If you compare this value with a given barrier value, you can determine whether the measured package has been coated with a sufficiently good barrier. This known control method disadvantageously takes a very long time, so that this method can hardly be used in the course of a pack production, since a real-time measurement is practically impractical.

It is therefore an object of the invention to provide a method of the type described at the outset, with the aid of which the barrier property of the coating can be measured in a shorter time, reliably and, if appropriate, for the entire coating surface without destroying the body or the package having the plastic wall.

This object is achieved according to the invention in that

- First, a fluid is applied to the plastic wall, which contains a test medium with at least one component, which can diffuse into the plastic wall and be absorbed there, after the coated space has been applied to the coated surface, test medium deposited on it is removed from the surface, - then the coated space with an extraction medium in which the test medium is readily soluble and the test medium can be measured, is acted upon and the concentration of the test medium in the extraction medium is measured. With this new measuring method, the coating on the entire surface of a plastic wall, for example on the inside or the outside of a package, which can have the shape of a bottle, for example, can be measured for the barrier properties. It can therefore be measured whether low-molecular gases, preferably oxygen or carbon dioxide, can diffuse through the coating or not. If the coating is inhomogeneous or even places where the wall of the package is not coated at all, a significantly greater diffusion of the oxygen will be measured than if the coating on the entire surface is so homogeneous that the oxygen without crossing the barrier cannot pass through the wall.

Both in the known method and in the method according to the invention, the space on the coating side, in the case of an inner coating, that is, the interior of the package, is acted upon by, for example, flushed and then flushed through until no more low molecular weight gas is present This space is located, which is to be prevented by the coating from passing through or diffusing through the plastic wall. In the known case, the coated space is pressurized with nitrogen, which is not a test medium. In contrast, according to the invention, the first fluid contains a test medium, for example acetaldehyde or hydrogen peroxide (H ₂ O ₂ ). In the known method, the flow of the low molecular weight gas, for example oxygen, is always measured in one direction. For example, it is measured whether oxygen outside the plastic package (in the air) diffuses through the plastic wall despite the coating inside. A reverse flow is neither generated nor measured. In contrast, according to the invention, the coated space is also flushed with the first fluid containing the test medium, for example H ₂ O ₂ , but no consideration is given to the oxygen located outside the package. Rather, one selects such a test medium that diffuses into the plastic wall and can also be absorbed there. If the coating were theoretically very good with a 100% barrier property, then no test medium would be absorbed in the coating and certainly not in the plastic wall, could not then be extracted and consequently not measured. The gas flow is therefore provided in two directions, namely, for example, from the inside of the pack into the plastic walls and then back out of these walls or the coating into the interior of the pack. One can see the advantageous independence from low-molecular gases located outside the package, provided the interior is coated (and vice versa). It would also be conceivable to introduce several different test media into the first fluid.

Destruction of the plastic wall is avoided. No wall parts need to be punched out and measured separately. Despite the measurement of the entire hollow body, the barrier property is checked in a shorter time. Good and reliable measurements were obtained in ten minutes or less. Measuring devices for measuring the concentration of a um in another are available in engineering. One can measure precisely and quickly how much test medium, for example H ₂ O ₂ , is contained in an extraction medium, for example water or air.

Under other conditions, the total measurement can be carried out within two hours, and it has been shown that this period is still reasonable and usable for a production control. This enables the measuring accuracy to be increased, in particular, since the total amount of test medium extracted increases with increasing extraction time.

The basic idea of the new measuring method is that one tries to introduce a selected test medium from the side of the coating into the coating and / or the plastic wall located behind it (exposure), so that there is at least one diffusible and absorbent component in the plastic wall and / or its Coating can accumulate, after which possibly deposited test medium is removed from the surface on the coating side with the aid of a blowing agent, for example gas or liquid. Then, after this process of diffusing in, the test medium will try to diffuse out again. According to the invention, an coated medium, for example water or air, is then applied to the coated space. This must be matched to the test medium so that the test medium can dissolve in the extraction medium and can also be measured in the extraction medium. The test medium thus emerges from the plastic wall and the coating into the extraction medium and delivers a concentration there which, according to a calibration curve, allows statements to be made about the quality of the barrier property of the coating.

It should be noted that a 25% aqueous solution of H ₂ O _{2 is} preferably used as the test medium for coated PET containers.

It is expedient according to the invention if, before the coated space is acted upon by the first fluid, this space and the surface of the coating are heated in a conditioning phase to a temperature at which the material of the coated plastic wall does not deform. In the case of PET as a plastic, it is expedient to heat it to less than 60 ° C. It is advantageously sufficient if an internally coated package with a correspondingly heated air flow is only heated internally by blowing. This conditioning speeds up the measuring process because the test medium then diffuses faster into the layers to be examined.

For a further acceleration of the entire measuring method, it is expedient if, according to the invention, the test medium is removed from the coated surface by blowing on the warm air. During this step of removing the test medium for typical PET bottles with a volume of approx. 0.5 l in just 20 seconds, it can be considered sufficient this inflation and thus the removal of the test medium is then extended by 1 to 2 minutes when the test medium is partly condensed on the surface of the coating. The tendency towards condensation can depend on the concentration of the relevant component of the test medium, for example the concentration of hydrogen peroxide in water. The blowing up of warm air in any case allows the removal of all residual amounts of test medium from the exposed surfaces. A further advantageous acceleration of the measuring method and the guarantee of reliable results is achieved in that, according to the invention, the extraction medium has a temperature of approximately 20 ° C. The extraction time can be shortened even further to a few seconds if the temperature of the extraction medium is increased to uncritical values of, for example, 50 ° C to 60 ° C (uncritical in the sense of a successful measurement without interference factors).

Advantageously, the invention is further developed in that the test medium is approximately 25% aqueous solution of H ₂ O ₂ and if for applying 2 to 10 seconds, preferably 3 to 7 seconds, of warm air to the coating-side space in a predetermined dosage and particularly preferably this test medium is blown in for 5 seconds.

C02 can then also be used as the test medium; nitrogen or an inert gas, preferably helium or argon, as the extraction medium. The method according to the invention can also be carried out on walls made of polyethylene or PVC. The device for carrying out the method described above has an intermittently movable conveyor, above which a plurality of treatment stations are arranged one behind the other in the conveying direction. According to the invention, packages which are open on one side are held with their opening on top of this conveyor and conveyed from one treatment station to the next. In each treatment station, according to the invention, a fluid introduction inlet can then be arranged above the packing opening and connected on the upstream side to a supply line. In the last treatment station, the packing opening can also be sealingly connected to a fluid discharge line. Treatment can be imagined as conditioning, exposure to test medium (for example spraying in the aqueous H ₂ 0 ₂ solution), drying, extraction and measurement. One or more treatment stations can be used for the individual treatments. Different gases and / or liquids can be led through the pack opening into the pack and optionally out of it through the fluid introduction inlet. In the last treatment station, a fluid discharge line can also be sealingly attached to the package. This makes it possible to quantitatively measure the amount of previously introduced fluid that has been pushed out or sucked out. By grasping the fluid introduction inlet, through which, for example, the test medium has been introduced centrally in the manner described above, the fluid discharge line can ensure that a desired dose of the previously introduced fluid, for example the extraction medium, is led out and fed to a measuring room. The device according to the invention can be further configured in that the packing opening can be sealingly connected to a fluid discharge line in each treatment station after conditioning. If C0 _{2 is used} as the test medium, all the packs to be measured are sealed against an outside atmosphere in which there are or may be traces of gases, which under certain circumstances can lead to a falsification of the measurement result.

It is particularly advantageous if, according to the invention, the following treatment stations are provided in the conveying direction of the conveyor:

1. a first treatment station for conditioning the package with air,

2. a second treatment station for loading the package with test medium,

3. at least one third treatment station for removing the test medium deposited on the surface and not diffused into the wall from the pack,

4. a fourth treatment station for introducing extraction medium into the package and 5. a fifth treatment station for measuring the concentration of the test medium in the

Extraction medium.

To intensify the removal of residual amounts of test medium from the exposed surface, it may be expedient to use three of them instead of one treatment station. The entire measuring process can then be carried out accelerated even under those conditions in which the test medium has deposited on the surface with the formation of a liquid film by condensation. The blown dry air can then be used in any of the three treatment stations to remove the test medium.

The component of the test medium which can diffuse into the material of the plastic wall or the coating should be present in the highest possible concentration. The concentration gradient should be maximal in relation to the other components of the medium, so that a sufficient amount of this component of the test medium can be stored in the coated plastic wall. The measurement is more accurate, the larger the amount of test medium that first diffused into the wall and then extracted in a short time unit.

The test medium must also be so stable that it does not disintegrate until the coated surfaces have been applied. At least the component of the test medium mentioned above should not degrade. With the 25% aqueous H ₂ θ ₂ solution, these conditions are advantageously met.

The test medium should also be heatable to the temperatures mentioned and used in the measuring method. In other words, there must be good temperature resistance of the test medium over the entire sensible parameter range of the measuring method. The measuring process is mostly monitored and controlled by people. The test medium should therefore not be harmful to health for the personnel. It is preferred if an operator can carry out all process steps without protective clothing.

Packs are widely used in the food field, so the test medium should not be toxic in any way. The test medium must be food-compatible without any risk.

If the test medium or at least the aforementioned component thereof is introduced into the package in the gas phase, a homogeneous distribution of the same over the entire surface of the coated package is also ensured. All areas of a coating can then be detected together by one measurement process.

The test medium must also be chemically and physically designed so that it does not destroy the coating.

Similar conditions must also be provided for the extraction medium, for which water or air or noble gases can be used, for example.

The extraction medium should also be food-safe, stable without the risk of disintegration, it should not destroy the coating and should enable the test medium to pass well into the extraction medium.

With the measures mentioned according to the invention, a measuring method is proposed in which the essential conditions can be checked, i.e. can be checked and adhered to and which delivers reliable results in 10 minutes or less.

For the device for carrying out the measuring method, in particular the air quantities, the temperature, time and also the quantity of test medium and also of extraction medium can be reliably checked and maintained.

Further advantages, features and possible uses of the present invention result from the following description of a preferred embodiment in conjunction with the accompanying drawings. These show:

Figures 1 to 6a each schematically on the left a piece of a coated wall, next to which there are gas molecules on the right. Show: 1 shows the first phase in which H ₂ O _{2 is brought} into the space next to the coating as the test medium,

FIG. 2a the absorption phase with a continuous coating,

2b the absorption phase in the case of an interrupted coating, FIG. 3a the diffusion phase in which H ₂ O ₂ begins to diffuse into the coating in the case of a continuous coating,

FIG. 3b also the diffusion phase, but here with an interrupted coating,

FIG. 4a the drying phase with continuous coating,

FIG. 4b the drying phase with an interrupted coating, FIG. 5a the extraction phase with a continuous coating,

FIG. 5b the extraction phase with an interrupted coating,

FIG. 6a the measurement phase with continuous coating,

FIG. 6b shows the measurement phase when the coating is interrupted,

Figure 7 schematically and partially broken the system as a device for performing the measurement method and

FIG. 8 enlarges detail VIII in FIG. 7.

1 to 6a each schematically show a piece of plastic wall 1 of a liquid pack 2 shown in FIG. 7 in bottle form on the left-hand side, it being assumed that the outside of the pack is located to the left of the plastic wall 1. The pack is provided with a coating 3 on the inside. The interior 4 of the pack 2 is located to the right of the outer surface of the coating 3. These representations also apply to the case that 4 is the exterior and the space on the opposite side of the plastic wall 1 is the interior. Room 4 is then the room on the coating side. In the exemplary embodiment shown here, the permeability of the coating 3 to oxygen is to be measured, both the diffusion coefficient and the solubility coefficient of the coating 3 being an order of magnitude smaller than that of the plastic wall 1.

A test medium in the form of a 25% aqueous H ₂ O ₂ solution is added to the so-called first fluid. The component contained in this solution, for example the H ₂ O ₂ molecule, can thus diffuse into the plastic wall 1 and be absorbed there. For this purpose, according to FIG. 1, the coating-side space 4 is initially acted on by the H ₂ 0 ₂ vapor-containing first fluid.

The hydrogen peroxide molecules contained in the fluid can accumulate on the one hand on the outer surface of the coating 3, whereby one can speak of an adsorption phase, which is shown schematically in FIG. 1 in that some H ₂ O ₂ molecules 5 are on the outside of the coating 3 adhere while the other H ₂ 0 ₂ molecules move freely in space 4. All of the circles drawn in gray in the figures represent the H ₂ 0 ₂ molecules 5.

Optionally, before the room 4 is filled with fluid, this room 4 can be heated to a temperature of about 55 ° C. by means of a blown-in air stream, on the one hand to accelerate the diffusion processes and on the other hand not to close the material of the plastic wall 1, for example PET to be heated strongly so that the package as a whole cannot deform.

In the preferred embodiment, the H ₂ O ₂ molecules are blown into the space 4 in connection with warm air, and the exposure to the space with the hydrogen peroxide molecules 5 takes place for five seconds. Part of the hydrogen peroxide (the 25% solution) can also condense on the surface of the coating 3.

FIG. 2a shows how individual H ₂ O ₂ molecules 5 even migrate into the coating 3 in this absorption phase and are absorbed there. In the schematic representation, three such molecules 5 are shown in FIG. 2a. Figure 2b shows the same absorption phase at a poor, non-uniform or discontinuous coating 3. It can be seen how a greater number of H ₂ 0 ₂ -Moieküle 5 at the point of interruption of the coating (in Figure 2b approximately in the middle of the coating) in the plastic wall 1 diffuses into it.

In the diffusion phase as shown in FIGS. 3a and 3b, this diffusing into the good, closed coating 3 according to FIG. 3a continues as well as into the interrupted coating according to FIG. 3b. In the latter case, numerous H ₂ O ₂ molecules 5 have penetrated into the plastic wall 1 in this diffusion phase. The condensation film on the surface of the coating 3 is represented in FIGS. 3a and 3b by molecules 5 lying against one another and lying on the surface of the coating 3.

After this diffusion phase, it is assumed according to the measuring method that a sufficient amount of H ₂ O ₂ molecules 5 for the measurement-technical detection has accumulated in the coating 3 and / or the plastic wall 1 (FIG. 3b), so that another Diffusing is no longer necessary. The coating-side space 4 can thus be freed from the H ₂ 0 ₂ (the solution) of the test medium. The further step of removing the test medium from the surface of the coating 3 now follows. This is done by drying. If a stronger condensation film has formed on the surface of the coating 3, the residual amounts of hydrogen peroxide can also be removed by rinsing.

In FIG. 4, the arrow 6 shows dry air, which (if necessary after rinsing with water beforehand) is blown into the coating-side space 4 in order to remove the entire remaining amount from the space 4 and from the surface of the coating 3. One can see in Figure 4a in the continuous coating 3 that the H ₂ θ ₂ molecules 5 located in the room are entrained by the air stream 6 and removed downwards.

In the interrupted coating 3 according to FIG. 4b, one can see how the H ₂ O ₂ molecules 5 are also entrained by the air 6 from the space 4 and removed downward, but also in addition to the molecules 5 held in the coating 3 in FIG a large number of molecules 5 remain in the plastic wall 1 because these cannot be captured and removed by the air 6.

This results in the state shown in FIGS. 5a (or 5b for the interrupted coating) for the plastic wall 1 and its coating 3. The room 4 is initially filled with warm air and is now filled with water at 20 ° C as the extraction medium. These water molecules are represented by black circles in FIGS. 5a to 6b (in contrast to the light gray circles which represent the H ₂ O ₂ ). After rinsing the room 4 with water (water molecules 7), the state of FIG. 5a for the continuous coating 3 and that of FIG. 5b for the interrupted coating are obtained.

Now the H ₂ O ₂ molecules 5 contained in the plastic wall 1 and its coating 3 begin to be extracted. These H ₂ 0 ₂ molecules 5 (light gray) thus begin to migrate to the right out of the wall 1 with the coating 3 into the room 4. Depending on the embodiment, this extraction phase can last from 5 minutes to 2 hours. Thereafter, the state shown in FIGS. 6a for the continuous coating 3 and FIG. 6b for the interrupted coating 3 is reached. The actual measurement can begin in this state of FIGS. 6a and 6b. It can be seen from FIGS. 6a and 6b that between the black circles representing the water molecules 7 there are light gray circles representing the H ₂ O ₂ molecules. In the case of the "good", namely continuous coating 3 according to FIG. 6a, there are only a few (in this example four) H 0 molecules 5 between the water molecules 7. A small concentration of test medium will therefore be measured in space 4 with the Conclusion that the coating 3 has good barrier properties because only a few H ₂ O ₂ molecules (test medium) were able to penetrate into the coating and / or plastic wall 1, which were then extracted.

In the case of the interrupted coating 3, a state is established according to FIG. 6b. The H ₂ θ ₂ molecules 5 that have migrated into the plastic wall 1 in FIG. 5 b have migrated (extracted) to the right into the space 4 through the opening in the coating 3, but a much larger number of H ₂ O ₂ molecules can be seen 5 between the water molecules 7 in Figure 6b than in Figure 6a. The operator can therefore measure a high concentration of H ₂ 0 ₂ (test medium) in the water (extraction medium) with the conclusion that the coating 3 is not good, namely interrupted. These method steps shown in principle in FIGS. 1 to 6b can be carried out in the device shown in FIGS. 7 and 8.

In FIG. 7, the conveying direction 9 is represented by an arrow in a transport space, generally designated 8, which points from left to right in FIG. A conveyor known per se is to be thought of here, which moves the packs 2 intermittently from left to right at predetermined intervals. Under the transport space 8 there is a catalytic converter 10 which cleans the exhaust air which is drawn through the line 11 in the direction of the exhaust air arrow 12 to the pump 13 and is expelled by the latter in the direction of the arrow 14. The amount of exhaust air flowing through line 11 can also be measured using flow meter 15.

Seven treatment stations © to © are arranged above the transport space 8, which can also be designed as a hygiene room, in which the germ load in the atmosphere is thus reduced. The bottle-shaped packs 2, which are open on one side, each have an opening 16 at the top and are held on the conveyor (conveying direction 9) in such a way that a fluid introduction inlet (not shown in more detail) can be arranged above the pack opening 16 in each of the treatment stations © to ©. On the upstream side, each fluid introduction inlet is connected to a supply line.

For the treatment station 1 it is the supply line 17 through which dry air is supplied, the amount of which is measured via a flow meter 18 and the temperature of which is measured via a thermometer 19. The treatment station © is about conditioning. The dry air flows through an oil separator 20 through a valve, a flow meter 21, through a heat exchanger 22 and via a filter 23 to the treatment station © (for the conditioning phase).

Dry air at a temperature of approximately 100 ° C. is also pumped through the supply line 24 in the treatment station ©. In this there are the oil separator 20, the temperature measuring device 25, the pressure regulating valve 26, the filter 23 etc. In the embodiment shown here, a 25% aqueous solution of hydrogen peroxide (H ₂ O ₂ ) sprayed in as test medium, as can be seen in FIG. 8. The spraying takes place in the supply line 24 at the point above the heat exchanger 27. In FIG. 8, the storage vessel for H ₂ O ₂ is designated 28, from which the aqueous solution is pumped into the flow container 31 by means of the pump 29 via line 30 until the liquid level is between the MAX and MIN marks. The dose of the 25% aqueous solution of H ₂ 0 ₂ in this embodiment is 200 ul. This relatively low dose is sprayed via the nozzle 32 into the feed line 24, not shown in FIG. 8, in accordance with the spray jets 33. A pneumatic valve 34 ensures that a mixture of (possibly sterile) air and H 0 _{2 is} produced in the nozzle 32 and then sprayed according to the jets 33. In FIG. 8, the H ₂ O ₂ is fed from the flow tank 31 from above in accordance with the amount controlled in the nozzle 32 via the pressure line 35 and with that of sterile air introduced below according to arrow 36. The spray jets 33 contain this sprayed mixture, which is mixed with the dry air supplied through the line 24. By arranging the opening 16 of the pack 2 below the outlet end of the supply line 24, this gas / H ₂ O ₂ mixture reaches the bottle-shaped pack 2, gets there on the bottom and upwards through the opening 16.

If C0 _{2 is used} as test medium instead of H ₂ 0 ₂ (in another embodiment, not shown), from the treatment station © to the end to the treatment station © in each treatment station, the packing opening 16 should be sealingly connected to a fluid discharge line, as is the case designated for the treatment station © with 37 and is shown for all embodiments. The purpose of this sealing connection is that when C0 _{2 is used} as the test medium, the measurement results should not be falsified by the amount of C0 ₂ in the air.

The phase for removing the test medium, in the shown embodiment of the H ₂ 0 ₂ , takes place in the treatment stations ® to ©. In these drying phases, too, dry air is fed through a feed line 38 via the distributor 39 to the respective heat exchanger 27 and then down to the packing 2. It is assumed that after the interior of the package has been flushed three times with the dry air via the respective supply line 38, the test medium is reliably removed.

In the treatment station ©, pure water is supplied via the flow meter 40 to the package 2 via the feed line 41. This is the extraction medium into which the H ₂ 0 ₂ molecules migrate. The extraction takes place in a few minutes, preferably in a time between 1 and 9 minutes and particularly preferably and reliably in 5 minutes according to the test.

In the treatment station ©, H ₂ O ₂ -free gas, for example air, is fed to the interior of the pack 2 via the feed line 42 in order to drive out the water, which is partly laden with H ₂ O, as the extraction medium through the fluid discharge line 37. The H ₂ 0 ₂ content is then measured in this within 1 minute. The result obtained is reliable and secure. The total time for carrying out the measuring process is less than 10 minutes if the extraction time is assumed to be about 5 minutes.

The time taken to remove the test medium is 7 seconds per treatment station. In the treatment stations ® to ©, the H ₂ 0 ₂ is removed in 3 x 7 seconds, for a total of 21 seconds.

Alternatively, one can also provide C0 ₂ as the test medium, which can be detected very easily, for example optically. In the above description, 1 PET was assumed as the material for the plastic wall. Other materials on which the new measuring method according to the invention can also be carried out are polyethylene, PVC and aliphatic polyamide, which is also commercially available under the protected trademark “nylon”. Regarding its chemical definition, Rompps Chemie-Lexikon, 8. Edition, 1985, Volume 4.

Water and air have been specified above for the extraction medium, but nitrogen or a noble gas, such as preferably helium or argon, is also possible.

LIST OF REFERENCE NUMERALS

1 plastic wall

2 liquid pack

3 coating

4 coating-side space

5 H ₂ 0 ₂ molecules

6 dry air (arrow)

7 water molecules

8 transport space

9 Direction of conveyance

10 catalyst

11 line

12 exhaust air

13 pump

14 arrow (exhaust air discharge direction)

15 flow meters

16 upper opening of the pack

17 supply line (dry air)

18 flow meter

19 thermometers

20 oil separators

21 flow meter

22 heat exchangers

23 filters

24 supply line

25 temperature measuring device

26 pressure control valve

27 heat exchangers

28 storage vessel for H ₂ 0 ₂

29 pump

30 line

31 Aqueous solution

32 nozzle

33 sprays

34 pneumatic valve

35 pressure line

36 arrow (direction of introduction of sterile air)

37 fluid discharge line

38 supply line

39 distributors

40 flow meters

41 supply line for water

42 supply line

Claims

Patent claims

1. A method for measuring the permeability of a coating on a plastic wall (1) for low-molecular gases, for example oxygen, the diffusion coefficient and / or solubility coefficient of the coating with respect to the low-molecular gas being approximately one order of magnitude smaller than that the plastic wall (1), in which the space (4) on the coating side is acted upon by a first fluid (5) and flushed through until essentially only this first fluid (5) is left in the space (4), characterized in that

the first fluid is a test medium (5) with at least one component which is incorporated in the

Diffuse plastic wall (1) into it and can be absorbed there, after the coating-side space (4) has been applied to the coated surface, test medium (5) deposited on it is removed from it, then the coated space (4) with an extraction medium (7), in which the test medium (5) is readily soluble and the test medium (5) can be measured, acted upon and the concentration of the test medium (5) in the extraction medium (7) is measured.

2. The method according to claim 1, characterized in that in the coating-side space (4) this and the surface of the coating are heated in a conditioning phase (Φ) to a temperature at which the material of the coated plastic wall (1) is not deformed.

3. The method according to claim 1 or 2, characterized in that the removal of the test medium (5) from the coated surface by blowing hot air (treatment stations ® - ©).

4. The method according to any one of claims 1 to 3, characterized in that the extraction medium (7) has a temperature of about 20 ° C.

5. The method according to any one of claims 1 to 4, characterized in that the test medium (5) is approximately 25% aqueous solution of hydrogen peroxide and for the application of the coating-side space (4) in a predetermined dosage with warm air. 2 is blown in for up to 10 seconds, preferably for 3 to 7 seconds and particularly preferably for 5 seconds.

6. Device for performing the method according to one of claims 1 to 5, with an intermittently movable conveyor (conveying direction 9), over which a plurality of treatment stations (© to ®) in the conveying direction (9) are arranged one behind the other, characterized in that - open on one side Packings (2) are held with their opening (16) on the top of the conveyor, a fluid introduction inlet can be arranged above the packing opening (16) in each treatment station (© to ®) and upstream with a supply line (17, 24, 38, 41, 42) is connected and - in the last treatment station (©) the packing opening (16) seals with one

Fluid discharge line (37) can be connected.

7. The device according to claim 6, characterized in that in each treatment station (© to ®) after conditioning (treatment station ©), the packing opening (16) can be sealingly connected to a fluid discharge line (37).

8. Apparatus according to claim 6 or 7, characterized in that the following treatment stations are provided in the conveying direction (9) of the conveyor:

- A first treatment station (©) for conditioning the package (2) with air, a second treatment station (©) for loading the package (2) with test medium (5), at least a third treatment station (® to ©) for removing the test medium (5) from the pack (2) deposited on the surface and not diffused into the wall, a fourth treatment station (©) for introducing extraction medium (7) into the pack (2) and a fifth treatment station (®) for measuring the concentration of the test medium (5) in the extraction medium (7).