MXPA98006458A - Metand apparatus for sterilizing surface of articles and an adequate system for sterilizing bottle - Google Patents

Abstract

The surface of articles that are penetrable by high frequency energy, such as for example food plastic packaging, which are manufactured by blow molding or vacuum molding, and in particular returnable bottles for non-alcoholic beverages, are sterilized by providing a film liquid on the articles, after which they are subjected to microwave or high frequency to heat the liquid film, preferably to the boiling point. The liquid is preferably water with a de-stressing agent. An apparatus for performing the method is provided with soaking means, draining means adapted to leave a liquid film on the articles during draining, and heating means. The draining means are substantially constituted by transport means for transporting the articles from the soaking means to the heating means. A system for sterilizing plastic bottles may comprise a washing section, a rinsing section, transport means adapted to allow the bottles to drain during transport, and a heating section.

Description

METHOD AND APPARATUS FOR STERILIZING SURFACE OF ARTICLES AND AN ADEQUATE SYSTEM FOR STERILIZING BOTTLES FIELD OF THE INVENTION The present invention relates to a method and apparatus for surface sterilizing articles and a system suitable for sterilizing bottles. The method is of the type described in the preamble of claim 1, the apparatus of the type described in the preamble of claim 11, and the system is of the type described in claim 17.

BACKGROUND OF THE INVENTION From the German patent publication no. A method for filling containers such as bottles is known, wherein microwaves are applied to the containers before they are filled to sterilize the containers. By this means, the moisture present on the surfaces of the containers evaporates, and the heat developed by the steam kills the undesirable microorganisms on the surfaces. Before or during the microwave treatment, water can be additionally applied to or injected into the containers, therefore, steam is created, due to the treatment with the microwaves, said steam killing the microorganisms. Steam development is established that takes place for a few seconds. From the correspondence relating to the monitoring of the Danish patent application 2354/89, a microwave sterilization system for packaging is known for washing and sterilizing plastic packaging, in particular for returnable plastic polymer bottles, in this system, washing of the packages takes place at a temperature not exceeding 35 to 40 ° C to avoid shrinkage of the package. To obtain, for sure, an optical cleaning of the packages at this low temperature, ultrasound is used, doing everything possible to avoid the addition of bleach to the washing water. The washed package is not sterile after washing at said low temperature, and therefore, a sterilization using a microwave is carried out after washing. It is stated in the correspondence as a fact that the package would be heated to a temperature above the deformation temperature, if it were subjected to microwaves in a humid condition. This is explained by the fact that large amounts of energy would be transferred to the remaining moisture in or on the package. To prevent the application of the microwave from the heating of the plastic material above the deformation temperature, it is therefore established in the correspondence that, during the microwave sterilization treatment, an exact control of the microwave energy must be exercised as well as a removal of moisture from the package by means of a sterile air drying and cooling flow. However, it does not describe in the correspondence how the control of microwave energy is going to be carried out. It only states that the package can tolerate large amounts of microwave energy when it dries, since it has a crystal lattice structure and, consequently, is not influenced by the microwave energy that kills bacteria and spores exclusively which are "organic" There is no detailed description or correspondence of how the system will be operated or worked in order not to heat the package inappropriately and in fact kill microorganisms effectively, and it seems to be ambiguous if a total sterilization would be fully obtainable by following the instructions given in the correspondence.

In addition, Swedish patent publication No. 462,281 discloses a method and apparatus for sterilizing empty packaging containers by applying steam under pressure, preferably at a temperature of 120 to 140 ° C, and preferably by the additional use of peroxide hydrogen. Then microwaves are applied to the containers, which causes the temperature to rise around 145 ° C. From Swedish Patent Publication No. 465,512 a method for sterilizing a width of packaging material by spraying on a sterilizing liquid such as a hydrogen peroxide solution is known., which is then removed from the width of the material by applying infrared light, microwave, high frequency energy or hot air. Finally, the German patent application No. 34 14 268 discloses a method and an apparatus for killing germs in food containers, such as, for example, rates for dairy products, by applying hydrogen peroxide to the containers, the peroxide being atomized by means of of ultrasound at a frequency above one megahertz. At the end of the process, the containers undergo a heat treatment by means of hot air or microwaves. None of the methods described in these three publications can be used to sterilize thermosensitive articles.

BRIEF DESCRIPTION OF THE INVENTION The object of the invention is to provide an effective surface sterilization of articles that are penetrable by high frequency electrical energy, in particular articles that do not resist heat exceeding a certain limit. It is part of the object that a definitive part of the surface of the article is sterilized. This part will often be the total surface of the article, but if the article for example is a container the surface in question may be the total interior surface of the article. Important examples of the articles are plastic containers, which have been formed by hot blow molding or vacuum molding, for example, returnable bottles commonly used for non-alcoholic beverages made of PET (polyethylene glycol terephthalate) or commonly used flat PE vacuum film containers (polyethylene), PS (polystyrene) film or the like for packaging, for example, food products in self-service stores. These containers often have a so-called elastic memory or "residual activity", by which the phenomenon that the article can remember a shape and size, which had an earlier stage of manufacture and that this often occurs, is understood. It is forced to return to its shape when heated. Moreover, the articles can, for example, include containers for packing preserves or semi-preserves (for example, transparent containers with screw-in lids for marmalade, herring, etc.), or for packing non-conserved technical products such as non-preserved plastic paint. Soft drink bottles are formed as a so-called preform, that is, a bottle in which the mouth area, with a thread etc., has its final size and shape, but in which the part of the container is much smaller and is thick-walled. These preforms occupy very little space and can, therefore, at a low cost be transported from a central place of manufacture to various finishing sites, often in other countries, where these are inflated in a hot condition for the part of container that occupies the desired shape and size. The container part can then be given to a desired individual form, according to the desire of the producer of the non-alcoholic beverage without the need to use different preforms. This has turned out that the soft drink bottles tend to shrink because of the elastic memory, already in temperature slightly above 40 ° C. Therefore, the known washing and sterilizing processes are not suitable for cleaning these bottles, since the bottles are subjected to shrinkage at the temperatures used in these known processes, typically around 60 ° C or higher. This shrinkage is obviously undesirable, and a main part of the bottles has to be discarded after having been cleaned sometimes using the known procedures. At the same time, there is a considerable need for an effective cleaning and sterilization of these bottles, since partially the owners (the factories producing soft drinks want these to be filled with different products without any kind or previous class, which, as is tested by experience, can dislike the product previously contained, and partially users after emptying the bottles will notoriously use them for most different purposes, such as storing oil or diesel oil, or filling with different drinks strongly of flavor, like a Danish fashion drink "smá-grá" ("Small Gray Ones ", licorice drops and ammonium chloride dissolved in vodka.) In order to satisfy the above objects, the present invention discloses a method, an apparatus and a system The method is characterized by the subject matter of the characterizing clause of claim 1. The desired sterilization is obtained by heating the liquid film, and the heating is carried out by subjecting the article to high frequency electrical energy. Experiments have shown that it is extremely important that the liquid be heated by high frequency electrical energy that is actually present in the article in the form of a liquid film. Only in this way is the generation of a guaranteed amount of heat of sterilization on the desired total surface, without the development of heat becoming so intense that the undesirable heating of the article itself takes place. By providing the liquid film, it is ensured in this way that a substantial heating of the microclimate on the surface of the article actually takes place. Furthermore, a total drying of microorganisms and germs on the article is avoided, which guarantees that they are optimally sensitive to high frequency electrical energy. Finally, the risk of sporogenous microorganisms that create spores is reduced, which will normally happen if these microorganisms are dried. Due to the fact that the liquid is present on the article just in the form of a film, that is, as mentioned above, it is guaranteed, that the amount of liquid is so small that during heating it can not transfer sufficient heat to the article to heat the last significantly. By the liquid film established in the article which is continuous, the sterilization of the surface of the total article, or of a corresponding, definitive part of the surface in its entirety, respectively, is guaranteed. According to the invention, the formation of the substantially continuous liquid film is guaranteed using a liquid that is not repelled by the material of the article. Particularly for food-related uses, it is preferred with water, which is, however, largely repelled by polymeric materials. According to the invention, in this case a de-stressing agent can be added. This also gives the additional advantage that the thickness of the liquid film up to a certain point can be controlled by controlling the type and concentration of the deicing agent. As the de-stressing agent, salts, such as, for example, bicarbonate, organic solvents, for example, ethanol or surface-active agent, can be used. In particular, surface-active agents, particularly of the non-ionic type, are preferred, since they can be used in low concentrations and do not cause substantial foam formation. By the aforementioned measures, it is obtained that the liquid film established in a particularly simple manner. As mentioned in claims 2 to 4, the method according to the invention can be used advantageously for packaging, including returnable bottles and food packaging trays. This is due to the fact that the method according to the invention makes it possible to avoid using washing and sterilization chemicals, which are primarily undesirable in relation to the packing of edible food, and secondarily considerably less harmful to the environment. For the subject matter of claim 5, a particularly effective and rapid sterilization is obtained. By the subject matter of claim 6, it is obtained that any microorganism contained in the water that can be left after the removal of the film, is annihilated. By the material of claim 7, it is obtained that an appropriate charge of the microwave source, usually a magnetron, is occurring, even when the articles with the liquid film present, do not constitute a noticeable charge. By using the frequencies mentioned in claim 8, it is obtained that a comparatively high power supply can be used as in most countries particularly of easy regulations requested for the use of these frequencies. By using the means mentioned in this claim, a particularly simple tool is obtained to transfer the high frequency energy to the items. The subject matter of claim 9, it is obtained that the same liquid that has been used to wash or rinse the article, can be used for the formation of the liquid film. By the material of claim 10, a particularly effective washing is obtained, which is a prerequisite for the adhesion of the liquid film and so that impurities are not present in the article, whose impurities would be able to break the liquid film. The apparatus is characterized by the subject matter of the characterizing clause of claim 11. By designing the apparatus with runoff means in the form of transport means, transport means required also as runoff means are used. By designing the means of transport as mentioned in the characterizing clause of the claim, it is further obtained that in a simple and safe manner a substantially continuous liquid film is left on the articles without any risk of the film drying out. By the subject matter of claim 12, it is ensured that purging of liquid that may have accumulated within the cavities on the article and / or a desired smoothing of the liquid film and / or a desired cooling of the article before treatment with the high frequency energy. In claims 13 to 16, preferred embodiments of the soaking means for forming the liquid film and the heating means for heating the liquid film are described. The system is characterized by the subject matter of claim 17. By constructing a system as described in this claim, the rinsing liquid used in the rinsing section can be used immediately for the formation of the liquid film for use in sterilization, whereupon this liquid serves the double purpose. By this means, a very compact system is obtained together with a washing and sterilizing process which is optimally benevolent towards the bottles with respect to the temperature stress on the material of the bottles. This system is suitable for sterilizing both returnable bottles and discarded bottles. By the subject matter of claim 18, it is obtained that the sterilization can be carried out immediately after the bottles have been washed. When ultrasound is used, the washing can be carried out with a minimum use of exposure or almost no exposure, and in this way as little harmful to the environment as possible. Such washing before anything else will be necessary when the system is being used for returnable bottles. By the subject matter of claim 19, it is understood that the bottles can be transported to fill them in a sterile manner. The invention will now be explained in the following by means of examples, and with reference to the drawings. The invention will be explained with reference to the washing and sterilization of plastic bottles, but the invention can be used for any other suitable article.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, Figure 1 schematically shows an experimental arrangement for carrying out the method according to the invention, Figure 2 schematically shows an elevated view of a machine for washing, rinsing and soaking returnable bottles for soft drinks, and Figure 3 shows a sectional view of a step microwave oven for sterilizing the bottles that have been washed, rinsed and soaked by means of the machine according to Figure 2.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows an experimental arrangement for carrying out the method according to the invention. In a laboratory table 1 with a sump or cavity (not shown), and a tap 2, the containers 3 and 4, are assembled, each having a volume of 41 liters. The container 4 has an outlet 5 towards the container 3. The container 3 is connected through a tube 6 with an outlet not shown. The containers are of the trademark SONOREX type R, provided with two ultrasound transducers (not shown) each of 1,000 W, induced from two ultrasonic generators at a frequency of 35 kHz, built into the containers and through of which the water of containers 3 and 4 can be put in corresponding oscillation. In the other table 1, there is also a microwave oven 7. The oven 7 has been made by modifying a microwave oven of the VOSS brand, type 1.12, model MOA263-1.

With the modification the grill element was removed and an extra track blade (not shown) was inserted for the microwaves in order to obtain a better distribution of the microwave energy over the oven volume. Moreover, the control of the magnetron was modified in such a way that it can operate continuously (not pulsed for up to 5 minutes), instead of a microwave oven, a high-frequency heating system could be used, for example, of the type described in Danish patent 169,902. The bottles are generally moved in the direction of travel 8, the uncleaned bottles being provided to the left in Figure 1. The bottles 9 are placed in the container 3, and washed with water, which has flowed over the container 4. , through outlet 5, and under treatment with ultrasound. After washing, these are moved to the container 4, where a rinsing with water is carried out, to which only a de-stressing agent has been added, and also under treatment with ultrasound. After washing and rinsing the bottles 10, they are covered by a film of water uniformly distributed, very thin, on the outer and inner surfaces. The washing performed has removed the impurities that could break the water film, and the softening agent ensures that the water film adheres to the bottles even when they have been produced from a type of water repellent plastic. And the bottles are drained under the simultaneous flip to make all the water drain from their inner and outer surfaces and then they are visually controlled. The controlled bottles 10 are with a corresponding number of caps 11 transported to the microwave oven 7, and treated with high frequency electrical energy. Appropriate measures are taken to avoid damage to the water film. During the treatment, the water film is heated, thereby killing the microorganisms present in the water film. The treatment can be continued, since microorganisms may have a certain sensitivity to high frequency electrical energy even after complete or partial drying. The bottles and lids are removed from the microwave oven after the treatment and the lids are placed. The bottles 2 with the caps can now be led to their bacteriological control. Even when a real test arrangement has been described, the person skilled in the art would realize that a system for cleaning and sterilizing bottles or other types of packages or other suitable articles on a large scale may be constructed in the same manner. The bottles 12, then they would be additionally supplied for filling. These would not have layers on them, but these could be temporarily protected against impurities in a similar way or, for example, by means of an awning that is filled with sterile air under a slight overpressure.

Some of the large-scale system sections may be in accordance with the invention, for example, being organized as shown schematically in Figure 2 and 3. Figure 2 is an elevated view of the washing, rinsing and soaking machine. for returnable bottles for non-alcoholic beverages of the type generally available in the sizes of half a liter and a liter and a half. The machine consists of a frame 21 of square pipe and having an endless chain 22, which transports the bottles in the direction 39. The chain 22 is provided in its total length with bottle holders 23, however, these have for reasons of clarity have only been shown in some places on the chain 22 in Figure 2. The Chain 2, is driven and operated by chains 28, 29, 37, 38, and guided by the guide 27. At a starting station 24 (not shown in detail), the new non-sterilized bottles are inserted from the factory and the returnable bottles 25 into bottle holders 23 and are put around and they are placed around with the chain 22. The chain 22 first passes through which the bottles 25 are driven, submerged and in a vertical position, whereupon they are completely filled with washing water. In the container 26 is the water with a deicing agent in the form of an active surface agent of the type used in home dishwashing machines (see below). The water is subjected to ultrasound by means of the submerged ultrasound transducers (not shown), which are preferably distributed over the entire length of the container. In the container 26 the residues of the previous contents of the bottles and label, etc., are detached and removed. In the machine 20 shown, the residence time of the container is between 100 and 200 seconds, preferably approximately 150 seconds. Then the chain 22 moves around a chain wheel 29 and back and forth through a section 30, in which the bottles of the washing water are emptied and further cleaned with jets of water to clear the residues of the contents and previous labels in the cleaning stations, 31, 32. The chain 22, as in bottles 25 then pass through a rinsing container 33 of the same construction and mode of operation as the washing container 26. In the rinse vessel 33 is the water with the deicing agent added. The water is conducted from the rinsing vessel 33 to the washing vessel 26 and then moved away, in the same manner as explained above with respect to Figure 1. After rinsing the chain 22 is passed over a chain wheel 37, where it is turned, in such a way that the bottles are emptied and drained 36. The water draining is collected in a tray 34. In the machine shown, the chain speed is 2 m / min (42 mm / s), the speed being continuously variable in the range of about 1.7-3.3 m / min, and the distances around the rinsing vessel and the drip pan 34 are thus adapted so that the bottles after having left the rinsing container they are empty during the course of 108 seconds, and then drained in the course of 60 seconds in addition. During the course of the next 54 seconds, the bottles are transported around the chain wheel 38 and turned vertically followed by which they are removed at a removal station 35 (not shown in detail), and conducted to a heating section. The total transport time for the heating section after finishing the runoff is in the machine shown mode of approximately 120 seconds. Figure 3 is a schematic section in a heating section 40 for a machine 20 as the one described above. The bottles 41 are here recharged on a conveyor belt 25 in the shape of a chain 42, with superabundant carrier members 43 and drag dogs 44, the bottles being transported upright on the upper part on the conveyor belt 45. The band 45 runs through a box 46 that constitutes the compartment of a microwave oven. Devices (not shown) are arranged to provide microwaves and an adequate uniform distribution of these within the oven compartment 46. In order to guarantee an advantageously uniform loading of the microwave source, normally a magnetron the oven compartment can according to the invention to be provided with water absorbing microwave compartments or the like to compensate for the insignificant loading of the source of the bottles 41 with the water film. A system according to the invention can also be constructed in conjunction with a plant for filling the bottles, and in a simple manner, a plant can be established in which the sterile bottles can be kept during filling, in order to obtain a aseptic filling. When sterile air is used under a slight overpressure to create a sterile protective atmosphere, as mentioned the supply of the sterile air can be advantageously carried out, in such a way that because of the movement of air intake in the form of a jet or a curtain, a possible discharge of water residue is obtained on the articles and a cooling of the articles before the treatment with microwave or high frequency energy.

EXAMPLE 1 Nine PET bottles were filled with milk products (see the diagram below), and left for 30 days at room temperature. They were then emptied and washed with water, to which the demeaning agent of the SUN PROGRESS trademark (a common type for use in fret washing machines) had been added, with the use of ultrasound. After washing the bottles they drained. Then five of the bottles (marked 2 to 6) were treated in a microwave oven of the homemade type with pulsating energy of 750 wats for 85 seconds. Two of the bottles (marked 7-8) were not treated with microwaves, while two of the bottles (9-10) were treated as bottles marked 2 to 6, but then covered and finally given the treatment for an additional 30 seconds in the microwave Owen. The bottles thus cleaned, of which bottles 2 to 6 and 9 to 10 have also been sterilized by the method according to the invention, were subjected to a germ control test according to the Koch plate technique. and the following germ counts were observed: EXAMPLE 2 With the arrangement according to Figure 1, 150 returnable PET bottles were washed for non-alcoholic beverages, the volumes being half a liter and one and a half liters. We selected 100 of the bottles at random among the discarded bottles and 50 were newly arrived from the factory. In the container 3, the water coming from the outlet 5 of the container 4 was used at a temperature not above 28 ° C. The bottles were washed in the containers 3, with the application of ultrasound for 3 minutes to remove the residual contents, labels and label glue, etc. In the container 4 it was mainly water, to which detangling agents for homemade dish washing machines have been added, being the deicing agent of the trademark Skandinavish Denckiser A / S, 2800 of Lyngby, Denmark, containing from 5 to 15% of preservative agent and nonionic tensioning agents, in a concentration of 0.28% (one deciliter per 35 liters of water). The water was changed to every 25 bottles and its temperature was kept below 25 ° C. The bottles were rinsed in the container 4 under the influence of ultrasound for 2 minutes. The freshly brought caps from the factory for the bottles were washed in the container 4 for 20 seconds. After washing the bottles, they were checked for optical cleaning with satisfactory results, and the bottles were drained, that is, they were turned over, until all the liquid had been emptied and there were no drops or only very little felling of the bottles without considering his position. The bottles and lids were sterilized for 30 seconds in the microwave oven 7 set at 750 watts, in batches of 7 bottles plus 7 lids, followed by the lids. During the treatment in the oven, the water film disappeared from the bottles in less than 10 seconds. Steam or condensed droplets on or inside the bottles were observed during the first 5 to 8 seconds. All manipulation was done manually in a non-sterile atmosphere in a test room that has a door leading to the outside. Finally, a germ control test of all the bottles was carried out in the following manner: some sterilized water was emptied into each bottle, and after shaking, this water was removed and the germ count was proved by the plate technique of Koch, using a nutrient medium suitable for the relevant bacterial culture in relation to carbonated non-alcoholic beverages (ie, non-alcoholic beverages to which carbonic acid was added). Regarding all the bottles, the germ counts of less than 50 were found, which corresponds to the "satisfactory" assessment.

EXAMPLE 3 New and returnable PET bottles used were washed and sterilized, mixed 2 x 25 for non-alcoholic beverages of a volume of half a liter and liter and a half respectively, with the use of the arrangement according to Figure 3 and the method according to example 2. The volume and the height of the Bottles were measured before washing and sterilizing, and after 5, 10 and 25 times of washing and sterilizing. The volume was measured by filling the bottle to the edge, and the height was measured by means of a gauge ruler mounted on a surface plate. The results of the measurement listed below were obtained, each being average values for the bottles measured. The difference in volume measurements is attributed to the unstable measurement of the measurement method used: EXAMPLE 4 16 returnable PET bottles for non-alcoholic beverages were washed and sterilized using the arrangement according to Figure 1 and the method according to example 2, then the bottles were filled with the undesired products and liquids, respectively, mentioned in diagram below, and were left for periods established in the diagram. After the bottles had come to rest, they were washed again and sterilized under the use of the arrangement according to Figure 1 and the method according to example 2, and then filled with natural soda water. A test tasting gave the classifications 1 to 3 established in the diagram below and have the meanings: 1: satisfactory 2: not very satisfactory (after tasting) 3: not satisfactory (after tasting). The first product mentioned in the "smá grá" diagram has been described in the introductory part of the present description. The last two products mentioned in the diagram are examples of the previously mentioned, undesirable liquids. The remaining products are different non-alcoholic beverages, most of them being carbonated. Out of the 16 bottles, 4 were considered satisfactory (1), four were not very satisfactory (2) and (8) were unsatisfactory (3). These classifications were attributed to the fact that they are better than those obtained with traditional cleaning methods.

EXAMPLE 5 In a test corresponding to the test according to Example 4, the following results were obtained, with meanings similar to Example 4: In cases where it was established that the bottles have been washed twice (column 2 of the diagram) the result of the tasting test has been (not satisfactory), after the first washing and filling with natural serum water. These bottles are then washed a second time and once again filled with soda water and tasting proof. As a whole, the result of this test is considered to correspond to that obtained by traditional cleaning methods.

EXAMPLE 6 Two returnable PET bottles of non-alcoholic beverage fresh from the factory and three bottles used (recycled), with a volume of liter and a half were washed and sterilized under the use of the arrangement according to Figure 1 and the method of agreement with Figure 2. However, no de-stressing agent was added to the water, neither in the washing container 3 nor in the cleaning container 4. A visual check after washing, rinsing and draining, showed that the water adhered to the surface of the bottles with an interrupted film, that is to say, there were scattered dry areas of various sizes, in which the water had collected in drops and in "elongated strips" interlaced covered by the water film. After sterilizing with example 2, the bottles were divided, and a nutrition agent suitable for the bacteria in water and in the form of a jelly was applied to the inner surface of the cylindrical part of the bottle wall. After standing for 24 hours, the growth of bacterial colonies was demonstrated, with the germ count being 2 to 3,000 in scattered areas of size and shape as the previously observed dry areas of the inner wall of the bottle. This test result clearly indicates that it is vitally important for effective sterilization at the low temperatures used herein, that the liquid be present on the article as an uninterrupted liquid film. As will be seen from the examples, the invention makes it possible to wash articles, such as plastic bottles at a fairly low temperature with satisfactory results, since due to effective sterilization a better cleaning is obtained in total than by using methods traditional methods of cleaning. With this, you get the possibility to clean thermosensitive plastic packages, as for example, returnable PET bottles for non-alcoholic beverages, considerably many times more than is possible with the cleaning methods currently used. In this way, the bottles can be recycled more times than is currently possible, where they have to be discarded because of the large shrinkage before they are damaged. Moreover, the invention makes it possible to wash the articles without the addition of bleach, or at least with very low concentration of bleach. In addition, for example, bicarbonate bleach to wash water causes environmental problems and moreover presents a particular problem in the washing of returnable PET bottles for non-alcoholic beverages. The tension, to which these bottles are exposed during use, causes the formation of many very small cracks in the plastic material, and the sodium hydroxide deposits in the cracks, which gives the material an undesirable gray appearance. The cleaning methods used today need the use of wash water at a temperature of 58 to 69 ° C, and the addition of bicarbonate bleach to a NaOH concentration of 3 to 7%. By way of comparison, it can be added that the returnable glass bottles for non-alcoholic beverages are washed in water with a temperature of 92 ° C and the bicarbonate bleach being added at a NaOH concentration of 16%. In short, the invention offers, in addition to what has already been established, two very important advantages in comparison with traditional cleaning methods for the same purpose, namely a considerable energy saving and considerably reduced environmental damage. The energy saving is obtained because much less energy is used for the operation of the ultrasonic generators and the heating means, such as the microwave oven that is saved by only having to heat the wash water to 25-28. ° C. Substantially reduced environmental damage is obtained because the addition of environmentally harmful substances, such as bicarbonate-to-water d-lye, is avoided. Finally, effective sterilization makes it possible to reduce the use of preservatives in the products contained in the bottles.

Claims (19)

1. A method for superficially sterilizing an article made of a polymeric material and finished by heat deformation, such as molding, blow molding or vacuum molding, said method comprising treatment with high frequency electrical energy such as microwave, characterized in that: a film of substantially continuous liquid is provided on the article by applying to the article a liquid that is not stopped by the material of which it consists of the articles, said liquid preferably being water to which a de-stressing agent has been added, in particular an agent of active surface, and the liquid is carried away from the article and allowed to drain, followed by which, the article is subjected to high frequency electrical energy to heat the liquid film and sterilize at least a definite part of the surface of the Article.

2. A method according to claim 1, wherein the article is a package.

3. A method according to claim 2, wherein the package is a returnable bottle for beverages, the bottle being manufactured by blow molding.

4. A method according to claim 2, wherein the package is a tray to a box made by vacuum molding and is intended to pack or store food such as food products.

5. A method according to any of the preceding claims, characterized in that the liquid film at least locally is heated to the boiling point.

6. A method according to any of the preceding claims, characterized in that the article is still subjected to high frequency electrical energy after heating to boiling or evaporation of the liquid film.

7. A method according to any of the preceding claims, characterized in that the high-frequency electric energy is supplied in the microwave form, and the surplus microwave energy is preferably removed from the treatment site with energy, particularly preferred. by circulating a liquid that absorbs the excess energy.

8. A method according to any of claims 1 to 6, characterized in that the high frequency electric power is supplied at a frequency of 3-300 Mhz, preferably one of the frequencies of 13.56 Mhz, 27.12 Mhz or 40.68 Mhz, and preferably placing the article between two capacitor layer elements, through which the high frequency electrical voltage is supplied.

9. A method according to any of the preceding claims, characterized in that the sterilization is carried out immediately after a previous washing or rinsing of the article and in which the liquid is left on the article in a stage of the washing process or rinsed, respectively.

10. A method according to claim 9, characterized in that the ultrasound is being applied to the liquid used in the process of washing or rinsing during the process.

11. An apparatus for sterilizing surfaces of articles such as packages, including returnable bottles for beverages, whose articles are manufactured from a polymeric material and terminated by heat deformation, such as blow molding or vacuum molding, the apparatus being provided with soaking means for applying liquid to the articles, draining means for removing the liquid from the articles and heating means for subjecting the articles to high frequency electric power, characterized in that the draining means are substantially constituted by means of transport to transport the articles from the soaking means to the heating means under the simultaneous draining of the liquids of the articles, the transports are adapted to flip and / or move the articles such that all the liquid drains quickly from them, and the transport time of the soaking means to the heating means is measured, such, in relation to the prevailing temperature and air humidity, that the substantially complete runoff of the articles is guaranteed without drying the liquid film of liquids about the articles completely or partially.

12. An apparatus according to claim 12, characterized in that the draining means comprise members for blowing air through the articles, preferably sterile air and / or cooled air.

13. An apparatus according to claim 11 or 12, characterized in that the soaking means are substantially constituted by a washing or rinsing device for washing and / or rinsing the articles.

14. An apparatus according to claim 13, characterized in that the washing or rinsing device is provided with means for applying ultrasound to the rinsing or washing liquid, respectively.

15. An apparatus according to claims 11 to 14, characterized in that the heating means are substantially constituted by a continuous flow microwave oven.

16. An apparatus according to any of claims 11 to 14, characterized in that the heating means are substantially constituted by a high frequency heating system, preferably comprising capacitor plate means connected to a high power generator. frequency for applying to said capacitor plate means a high frequency electrical voltage, u between which means the articles are transported by means of the transport means.

17. A system for sterilizing bottles made of a polymeric material, the bottles being manufactured by heat deformation, such as blow molding, which system comprises: a rinse section for rinsing the bottles with water, preferably to which it has been applied a deicing agent, and preferably under the application of ultrasound, a heating section for applying high frequency energy to the bottles, such as, for example, a flow-through microwave oven, or a high-frequency heating installation and, first, means of transport for transporting the bottles from the rinsing section to the heating section, the transport means being adapted to allow the bottles to run substantially completely during transport and to protect the bottles against partial drying, preferably being constructed with a short transport path.

18. A plant according to claim 17, and further comprising: a washing section for washing the bottles with water or bleach before rinsing, preferably under ultrasound pressure.

19. A plant according to claim 17 and 18, further comprising second conveying means for transporting the bottles from the heating section to a packed bottling section or machine under aseptic conditions, preferably transporting in closed circuits and in an atmosphere of sterile air under pressure.