MXPA96003288A - Process and apparatus for sterilizing superfic - Google Patents

Abstract

The present invention relates to a process for continuously sterilizing surfaces with a mixture of air and gaseous hydrogen peroxide, wherein a stream of hot air is fed through a supply pipe to the different surfaces to be sterilized, characterized in that hot air is mixed with hydrogen peroxide completely vaporized, vaporized hydrogen peroxide is obtained by forming a thin film of liquid hydrogen peroxide that diffuses inside the wall of a porous tube where it is completely vaporized by heating a tube , the porous tube forms part of the hot air feeding tube and diffuses the vaporized hydrogen peroxide into the hot air stream

Description

PROCESS AND APPARATUS FOR STERILIZING SURFACES DESCRIPTION OF THE INVENTION This invention relates to a process for continuously sterilizing surfaces in an aseptic filling line, with a mixture of air and gaseous hydrogen peroxide, in which a stream of hot air is fed through a feed tube to the different surfaces that are going to be sterilized. The invention also relates to the apparatus used in this process. Sterilization of materials for packaging with gaseous hydrogen peroxide is well known in the art. European Patent Application No. 481 '361 relates to an apparatus for sterilizing containers and comprises a nozzle such as the surface of liquid hydrogen peroxide and heated air for vaporization of hydrogen peroxide. The disadvantage of this system is that the use of a nozzle to introduce the liquid hydrogen peroxide leads to a tendency to block the nozzle and, second, it is more difficult to allow uniform atomization and complete vaporization, when the drops have vaporized In addition, the specific vaporization chambers often require a high vaporization temperature and the decomposition rate of the hydrogen peroxide can be relatively high. Finally, the apparatus of the patent application mentioned in the above is complicated, which makes maintenance and cleaning more difficult and expensive. The purpose of the present invention is to overcome the disadvantages mentioned in the above and particularly to find a process, in which a complete vaporization of the aqueous hydrogen peroxide, a constant concentration of the hydrogen peroxide in the vapor phase can be ensured and a reduced decomposition to the minimum of hydrogen peroxide. This invention relates to a process for continuously sterilizing surfaces according to the preamble of claim 1, wherein the hot air is mixed with fully vaporized hydrogen peroxide, the vaporized hydrogen peroxide is obtained by forming a thin film of peroxide of liquid hydrogen in a porous tube and heating it, the porous tube forms part of the hot air feeding tube and diffuses the vaporized hydrogen peroxide into the warm air stream. The process according to the present invention takes advantage of the fact that the heat and mass transfer during evaporation are considerably greater when a thin film of liquid is in contact with a hot surface, compared with the technology mentioned in the above according to EP 481 '361 with the evaporation of the drops in a stream of hot air. Therefore, the formation of the well-spread thin film of liquid hydrogen peroxide is ensured using a porous tube. According to the invention, surfaces should be understood as any type of containers or enclosures, such as containers, made with any type of packaging material, such as glass, plastic or metal. The normal vaporization temperature of the hydrogen peroxide in the aqueous phase is about 107 ° C with about 35% hydrogen peroxide by weight: the vaporization of the hydrogen peroxide was carried out at a temperature of 110 to 130 ° C of the heating equipment . The temperature must be high enough to guarantee the vaporization of all the hydrogen peroxide, but too high to avoid a decomposition of the H202: normally, the temperature of the heating equipment is around 120 ° C. The process according to the invention is continuous and takes into account the new form of vaporization, the consumption of hydrogen peroxide can be reduced: the concentration of hydrogen peroxide is 5 to 20 mg / liter of air.

To prevent the gaseous hydrogen peroxide from condensing, the entire apparatus is maintained at a temperature of the order of 120 ° C. The hot air stream is generated by means of a low pressure fan and a simple heat exchanger and can be easily controlled using a flow meter. After the sterilization stage, depending on the concentration of hydrogen peroxide, condensation of hydrogen peroxide may occur: in this case, it is preferred to remove these residues and have a flow of dry air arriving on the surfaces sterilized at a temperature of the order of 120 °. C. It is also preferable according to the invention, to ensure that the efficient sterilization effect can be guaranteed: therefore, it is. preferable to have a means for controlling the temperature, the hot air flow rate and the hydrogen peroxide concentration of. the gas mixture. The hot air flow rate depends on the diameter of the feeding tube and on the number of containers which will be sterilized on the line: normally, the air velocity is 20 to 50 1 / minute per container. In relation to the concentration of hydrogen peroxide, it is measured in the line by means of a photometer or a system based on the thermal effect of a catalytic decomposition of hydrogen peroxide, in which a small part of the hydrogen peroxide stream It is absorbed through the measuring device (photometer or catalyst) using a small vacuum pump. The measurement will be explained in more detail in the following. The invention further relates to an apparatus for continuously sterilizing containers in an aseptic filling line, comprising a feeding tube for feeding a mixture of hot air and vaporized hydrogen peroxide and a plurality of nozzles through which the mixture is introduced into the surfaces to be sterilized, in which the feeding tube includes a section formed by a porous tube for direct feeding of the gaseous hydrogen peroxide into the hot air stream, the tube is surrounded by a heated medium. As already said in the foregoing, it is preferred that the hydrogen peroxide is fully vaporized at the time of mixing with the hot air. The porous tube is a sintered metal tube, for example, made of stainless steel having pores with a diameter of 20 to 80 microns, preferably of the order of 40 microns. If the pore size is below 20 microns, high pumping pressures are required for the liquid hydrogen peroxide and the pores run the risk of becoming blocked. Conversely, too large a pore size leads to the risk that not all hydrogen peroxide will vaporize. The thickness of the porous tube must be selected carefully for best results: in thin tubes, the contact period is not sufficient to allow vaporization and in too thick tubes, too much hydrogen peroxide decomposition may occur. The best thickness is 3 to 4 mm. In relation to the length, it must be sufficient to allow an adequate flow velocity and evaporation of the hydrogen peroxide, leading to an efficient concentration in the hot air stream: the optimum length is 15 to 30 cm. The liquid hydrogen peroxide is in aqueous solution. The concentration is not critical, but preferably it is between 5 and 45%, preferably about 35%. As already mentioned in the foregoing, it is preferred to avoid any possibility of condensation, for example of the steam coming from the water of the hydrogen peroxide: therefore the feeding tube is steam heated to a temperature of approximately 120 ° C. In the case of an apparatus, which could be operated under ultra hygienic conditions, it should also be possible to reduce hydrogen peroxide to as low as 0; sterilization efficiency is reduced to vegetative germs only compared to a reduction of thermophilic spores by hydrogen peroxide and needs heating of the feeding tube as high as 170 ° C. In the device according to the invention, the supply of gaseous hydrogen peroxide occurs through an inlet or several feed inlets, depending on the capacity of the machine. The diameter of the hot air supply tube is correspondingly increased. To measure the concentration of hydrogen peroxide, the apparatus further comprises a photometer or a system based on the catalytic decomposition of hydrogen peroxide. The hydrogen peroxide shows a characteristic absorption peak at a wavelength of 200 nm. A standard photometer is combined with a vacuum pump, which ensures a constant flow of the test gas through the measuring cell. To keep the test gas above the dew point, cylindrical and heated measuring cells are used. The thermal effect of the catalytic decomposition of hydrogen peroxide can be easily measured by means of a little catalyst. A small constant part of the gas flows, through a bit of catalyst, consisting of a ceramic wafer material that is maintained at a temperature of 120 ° C. Due to the exothermic decomposition of gaseous hydrogen peroxide into oxygen and water, a significant temperature increase of the test gas can be measured between the inlet and outlet of the catalyst. This increase in temperature can be correlated exactly with the concentration of hydrogen peroxide. The apparatus according to the invention, gives a tubular distribution system for the H2O2 vapor, without any valve, orifices or other components built in it. The correct gas distribution to the individual surfaces is ensured by interchangeable nozzles, which can be calibrated at the corresponding outputs, to ensure the desired amount of gas in the specific place. Both of these control systems are suitable for continuously controlling the vaporization quality of hydrogen peroxide and the sterilization effect during production. One embodiment of the invention will be described with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of the apparatus according to the invention; and Figure 2 shows a cross section of part A of Figure 1.

Figure 1 demonstrates the principle of sterilization of a container by means of the hydrogen peroxide vaporizer. The liquid hydrogen peroxide (1) is fed directly into the porous tube (4) by means of a positive pump (not shown), the peroxide which is vaporized by means of the vapor coating (3) heats the porous tube. The stream (2) of hot air is generated by means of a conventional low pressure system (not shown). To prevent condensation of gaseous hydrogen peroxide and steam, the feeding tube (10) is heated with a vapor liner (5). The containers (9) to be sterilized are placed directly under the corresponding nozzles (8) that diffuse the mixture of hot air and gaseous hydrogen peroxide. A measuring device (6), such as a photometer is placed in line to control the concentration of hydrogen peroxide in the line, a measured part controlled by a flow meter (19) of the main stream is absorbed through the device of measurement with the help of a vacuum pump (7), small. The nozzles (8) are also equipped with a vapor liner (11), thus avoiding any risk of condensation in the complete sterilization apparatus. The manner of operation is also explained in relation to Figure 2.

The steam jacket (3) of the vaporizer comprises two concentric tubes (12, 13), which are heated by steam, at a temperature of 120 ° C, which flows through the channel (14). The liquid hydrogen peroxide (1) coming through the inlet (15) diffuses through the porous tube (4), where it is completely vaporized by heating the tube (13), enters the feeding tube (10) and mixes with the hot air (2) that arrives. The vaporizer further comprises a connection part (16), which is necessary to allow the vaporizer to be placed in the feed tube (10). A second part (20) comprises an extension (17) to prevent the liquid hydrogen peroxide from dripping directly into the air stream. A connecting ring (21) joins the connecting part (16) with the part (20). Taking into account the presence of the steam jackets (5, 11), no condensation occurs and the mixture of air and hydrogen peroxide flows through the feed pipe (10) to the nozzles (8) and sterilizes the containers ( 9), which are then ready to go to the drying step (not shown) and finally under the aseptic filling nozzle. Normally, three seconds are necessary for the sterilization of each container. In the case of an apparatus operating with several inputs (1), the presence of the extension (17) is not very useful.

Example The apparatus of Figure 1-2 is used with hydrogen peroxide at a concentration of 35% and operating with a steam jacket at 120 ° C for container sterilization (volume of 200 ml) for aseptic applications. A concentration of hydrogen peroxide in the gas mixture of 10 mg / liter of air is used. The nozzle (8) operates at 30 1 / minute to achieve a decimal reduction of 5 D with Bac. subtilis, var. globigii and an exposure time of 3 seconds. Having described the invention as above, property is claimed as contained in the following:

Claims (11)

1. A process for continuously sterilizing surfaces with a mixture of air and hydrogen peroxide, in which a stream of hot air is fed through a feed tube to different surfaces to be sterilized, characterized in that the hot air is completely mixed With the vaporized hydrogen peroxide, the vaporized hydrogen peroxide is obtained by forming a thin film of liquid hydrogen peroxide in a porous tube and heating it, the porous tube forms part of the hot air feeding tube and diffuses the vaporized hydrogen peroxide into the hot air stream.

2. The process according to claim 1, characterized in that the vaporization of the hydrogen peroxide is carried out at a temperature of 110 to 130 ° C of the heating equipment, preferably at a temperature of around 120 ° C.

3. The process according to claims 1 or 2, characterized in that the concentration of hydrogen peroxide is 5 to 20 mg / liter of air and a hot air outlet consisting of between 20 and 50 1 / minute.

4. The process according to any of claims 1 to 3, characterized in that the complete system is maintained at a temperature of the order of 120 ° C.

5. The process according to any of claims 1 to 4, characterized in that the concentration of the hydrogen peroxide is controlled in the line by means of a photometer or a system based on the thermal effect of a catalytic decomposition of the hydrogen peroxide, in the that a small, measured part of the mixture is desired. to the photometer or the catalyst system.

6. An apparatus for continuously sterilizing surfaces in an aseptic filling line, comprising a feeding tube for feeding a mixture of hot air and vaporized hydrogen peroxide and a plurality of nozzles through which the mixture is introduced onto the surfaces that are going to be sterilized, characterized in that the feeding tube includes a section formed by a porous tube for direct feeding of the gaseous hydrogen peroxide into the hot air stream, the porous tube being surrounded by a heated medium.

7. An apparatus in accordance with the claim 6, characterized in that the porous tube has a length sufficient to allow a suitable flow rate and evaporation of the hydrogen peroxide.

8. The apparatus according to claim 6 or 7, characterized in that the porous tube is a sintered metal tube.

9. The apparatus according to claim 8, characterized in that the sintered metal tube has pores with a diameter of 20 to 80 microns, preferably of the order of 40 microns.

10. The apparatus according to any of claims 6 to 9, characterized in that the feeding tube is heated with steam.

11. The apparatus according to any of claims 6 to 10, characterized in that it also comprises in the line, for the measurement of the concentration of hydrogen peroxide, a photometer or a system based on the catalytic decomposition of hydrogen peroxide.