MXPA00003377A - Method and apparatus for sterilizing a packaging sheet material - Google Patents

Abstract

The method of sterilizing a packaging sheet material involves the steps of applying hydrogen peroxide to a packaging sheet material, and irradiating the packaging sheet material with light, including at least one UV wavelength between about 200nm and 320nm. The method also has an intermediate step of removing hydrogen peroxide from the packaging sheet material, after the step of applying hydrogen peroxide and before the step of irradiating the packaging material, whereby to target synergy between the UV light and hydrophilically absorbed hydrogen peroxide in any microorganisms present on the packaging sheet material. An apparatus for carrying out the method is also disclosed.

Description

METHOD AND APPARATUS FOR STERILIZATION OF A PACKAGING MATERIAL FIELD OF THE INVENTION The present invention relates to an improved method and apparatus for sterilizing a sheet material for packaging of the type used for packaging pourable food products such as milk, tomato puree, yogurt, fruit juices, wine, tea, etc. Such a packaging sheet material has a multi-layer structure including a base layer made of a material such as paper, which is covered on each side with a heat-sealable plastic material such as polyethylene. When the packaging material is to be used for the sterile packaging of pourable products such as milk treated at ultra-high temperature * (UHT milk), the face of the packaging material intended to be put in contact with the food product is also provided with a layer of barrier material such as eg aluminum, which is re-covered with a layer of plastic material such as polyethylene.

When packaging of the type of the aforementioned sheet material packages is manufactured, it is imperative that the microorganisms are not allowed to come into contact with the food product to be packed. Therefore, the packaging material must be sterilized REF. 33169 immediately prior to the use of the manufacturing packaging, and these must be kept in sterile conditions, until the packaging is completely sealed, thereby ensuring that the food product contained therein is free of microorganisms which otherwise they would spoil food and / or transmit diseases to consumers.

BACKGROUND OF THE INVENTION The laminated packaging material can be produced in the form of a coil which can be continuously fed into a forming, filling and sealing machine. Such machines include the filling machines e.g., the TBA / 19® and TBA / 21®, manufactured by Tetra Brick Packaging Systems, Via Dolphin 1, Modena, Italy. The coil is sterilized with a sterilizing agent such as e.g., hydrogen peroxide, which is subsequently removed by evaporation. The sterile packing material is then maintained in an aseptic chamber, then sealed longitudinally to form a continuous tube, which is filled with liquid food product to be packed.

The tube is then tightly and transversally sealed at regular intervals to produce pillow mold gaskets, which are mechanically bent to produce final gaskets. Such types of packages include e.g., parallelepiped gaskets known by the Tetra Brik Aseptic® and Tetra Brik® trademarks, and substantially parallelepiped gaskets with beveled corners commonly known by the trademark Tetra Prisma® and Tetra Prisma Aseptic®.

Alternatively, the laminated sheet packaging material can be cut into strips and then formed into packages the winch shaft. Such packages are sterilized by spray with hydrogen peroxide. The aerosol produces a thin box of hydrogen peroxide in the thermoplastic, hydrophobic outer layer of the packaging sheet material. Successively a source of UV light in the range of 200-325 nm is irradiated in the outer layer covered with hydrogen peroxide of the packaging material. The synergy that occurs between hydrogen peroxide and ultraviolet light carry out has a deadly effect on any organism in the packaging material. Subsequently, the hydrogen peroxide is removed and the packages are filled with liquid food product and sealed to produce eave packaging commonly known by the trademark Tetra Rex®.

Sterilization with hydrogen peroxide In sterilization systems using hydrogen peroxide, without any irradiation on top of UV light, efforts have been made to extend the time that hydrogen peroxide remains in contact with the packaging material, in order to increase the deadly effect of the sterilization process. U.S. Patent No. 3,904,361 describes a process wherein, in order to prevent or at least minimize the evaporation of a hydrogen peroxide film in a network of packaging material during its passage through a sterilization chamber, to prolong its contact with the network face and obtaining the desired sterilization, the chamber is saturated with steam and hydrogen peroxide vapor obtained by spraying hydrogen peroxide through nozzles in the chamber. Although this technique prolongs the contact of a very hot film of hydrogen peroxide with the net surface of the package to improve sterilization, this imposes severe restrictions on the rate at which the packages could be manufactured with the packaging machine.

Another problem encountered with known sterilization techniques employing hydrogen peroxide, contemplates the assurance of the uniformity of the degree of sterilization in all the packaging material. In some net-fed packaging machines, the hydrogen peroxide was mixed with water and deposited as a drop in a heated container placed in the sealed tube of packing material. However, the vaporized hydrogen peroxide only began to have a sterilizing effect when most of the water in the droplets had evaporated. Therefore, the concentration of hydrogen peroxide currently acting on the packaging material varied considerably, at the same rate as it was deposited from the drops of the sterilizing agent. In order to overcome this problem, US Patent No. 4,225,556 disclosed the use of a first treatment station with a container of hydrogen peroxide through which the packaging material was passed, and a second treatment station eQmprend.ie.nd_Q a Ca ra with one. inlet, and an outlet for the network of packing material, and a nozzle for spraying hydrogen peroxide on a heated surface. However, neither this disposition nor the above-described sterilization technique known from US Pat. No. 3904361 are compatible with modern high-speed food packaging machines due to the excessive time required to effect sterilization.

In order to overcome problems by observing uniformity of the sterilization of the packaging material network with hydrogen peroxide, the packaging material is passed through a tub containing sterilizing hydrogen peroxide solution, and in order to cope with the percentages of production always increasing, the hydrogen peroxide tubs have been increased in size to maintain the contact time between the packaging material and the sterilizing solution. The intensified contact between the hydrogen peroxide solution and the packaging material is of course an advantage from the point of view of bacteriological death. However, the intensified contact also increases the risk that the hydrogen peroxide solution will penetrate into and degrade the liquid absorbent fibrous layer of the network of packing material through cutting the end of the network. The over-size of the tub also results in an increase in hydrostatic pressure which increases the risk of liquid penetration into the network in the deepest parts of the tub. Moreover, since the packing material located in the tub during machine shutdowns is discarded, the deeper tubs caused large losses of material in each stopped machine.

Sterilization With hydrogen peroxide and UV radiation rays U.S. Patent No. 4,289,728 to Peel et al. Dealt with the synergy that exists between UV radiation below 325 nm, and hydrogen peroxide at a concentration of at least 0.01% and not greater than 10% by weight. By treating a microorganism on the surface of the packaging with a solution of irradiated ultraviolet hydrogen peroxide, the microorganism is rendered non-viable by the synergism between radiation and hydrogen peroxide.

However, even with the use of powerful UV lamps, a long irradiation time was required to complete the sterilization, and this long irradiation time gave rise to damage to the packing material, reducing its seal-hot strength and discoloration. East. As a solution to this problem, U.S. Patent No. 4,366,125 to Kodera et al discloses a system including a first station for applying a thin film of hydrogen peroxide at a lower concentration at room temperature on the external surfaces of a packing material. A second station, located upstream of the first station with respect to a direction of travel defined by the material to be sterilized, was provided by irradiation of the external surfaces covered with hydrogen peroxide with UV radiation. Finally, a third station was provided upstream of the second station to dry the material with aseptic hot air. U.S. Patent No. 5,114,670 to Duffey discloses a sterilization chamber including entry and exit of instruments for the material to be sterilized, instruments for introducing gaseous hydrogen peroxide into the sterilization chamber, and instruments for simultaneously irradiating the material to be sterilized with UV energy.

WO 97/35768 discloses a method of sterilizing food packaging packages comprising a first deposit step of a solution containing hydrogen peroxide having a concentration in a range of 0.05-0.20 wt.% Within an interior of a packer packaging; a second step of irradiating the interior of the container with ultraviolet light after the solution containing hydrogen peroxide is deposited inside the container, and a third step of removing the hydrogen peroxide from the interior of the container.

However, since the removal of hydrogen peroxide is carried out after irradiation with UV light, any microorganism present in the packaging material is, at least to some extent, protected by the layer of excess hydrogen peroxide covering the material of packaging. In addition, the method is applied to intermittently stopped and intermittently packaged packaging, and is not suitable for sterilizing a network by continuously moving or wrapping material sheet.

Methods of sterilization of a packaging material are also known from Patent Abstracts of Japan vol. 014, no. 135 (M-0949), March 14, 1990 and JP-A-02 004621, and also from Datábase WPI, section Ch. Week 8707, Derwent Publications Ltd., London, GB; Class D22, AN 87-046573, XP002061293 and JP-A-62004038 (Dainippon Printing Co LTD.), January 10, 1987. In both methods, the irradiation stage with ultraviolet light is performed first for removal of hydrogen peroxide from the surface of the packaging material. This has the disadvantage that any microorganism present in the packaging material is to some extent protected from UV radiation by the layer of excess hydrogen peroxide in the packaging material. Furthermore, these known methods are disclosed for stationary sterilization of packaging containers and are not suitable for the sterilization of a continuously moving network or sheet of packaging material in a modern, high-speed machine for packaging of liquid food products in packaging made of a continuous network of packaging material.

All sterilization techniques mentioned above are susceptible to improvement relative to the deadly effect obtained and the time necessary to ensure the elimination of all pathogenic microorganisms, in the packaging material, to be compatible with modern high speed liquid food packaging machines. which can form, fill and seal 18,000 or even more aseptic packages per hour, and where the packaging material moves at a speed at, or greater than 81.65 cm per second (48,990 meters per minute), such as the packing forming, packing and sealing machine described in European patent application No. 97830312.1, published on June 27, 1997, by the same applicant.

DESCRIPTION •• OF THE INVENTION It is a need in the state of the art to provide a method and apparatuses for the sterilization of packaging sheet material, which overcomes the problems encountered in sterilization methods and prior apparatuses of the state of the art.

A principal objective of the invention is to provide a method and apparatus for sterilization of a packaging sheet material, which achieves improved death rates with respect to known sterilization techniques, thereby improving the quality of the sealed packages manufactured with the packing sheet material and therefore the product released to the consumer.

Another object of the invention is to provide a method and apparatus for sterilization of material. packing sheet which is. Fully compatible: with modern high-speed machines, filling and filling machines.

An object of the invention is to provide a method and apparatus for sterilization of packaging sheet material using hydrogen peroxide., which minimizes the time that the sheet material remains in contact with the hydrogen peroxide, thereby preventing any wetting of the hydrogen peroxide at the cutting end of the packaging sheet material. This is a clear advantage, regardless of instruments which are used to apply hydrogen peroxide in the packaging material, but it is particularly advantageous when a hydrogen peroxide tub is used. The invention makes it possible to build a tub of reduced depth, by means of which problems do not arise relative to hydrostatic pressures which on the other hand would tend to promote the wetting of hydrogen peroxide at the cutting end of the packaging sheet material.

Still another object of the invention is to provide a method and apparatus for sterilization of packaging sheet material employing hydrogen peroxide and UV radiation, in which the UV radiation ion instruments commercially available can be used at a pod level. -r is such that it has no harmful effect on the packaging material.

An object of the invention is to provide a method and apparatus for the sterilization of packaging sheet material using hydrogen peroxide and UV radiation, which can be integrated into the current packaging forming, filling and sealing machines.

With the aforementioned objects in view, as well as other objects of the invention which will be apparent hereinafter, the invention provides a method of sterilizing a packaging sheet material, comprising the steps of; -application of hydrogen peroxide to a packaging sheet material, and; -irradiation of the packaging sheet material with light including at least one wavelength between about 200 nm and 320 nm, characterized in that it comprises the intermediate step of removing the hydrogen peroxide from the surface of the packaging sheet material while retains a residual or trace amount in any microorganism (30a), after the hydrogen peroxide application step and before the irradiation step of the packaging material, whereby said residual amount or trace of hydrogen peroxide absorbed by or located adjacent to any microorganism present in said packaging sheet material is directly objectified with UV radiation.

According to another aspect of the present invention, there is also provided an apparatus for sterilization of packaging sheet material which comprises -instruments for application of hydrogen peroxide to a packing sheet material moving in a forward direction, - instruments for irradiating the packaging sheet material with light including at least one UV wavelength between 200 nm and 320 nm, arranged upstream of said instrument for application of hydrogen peroxide, with respect to said advancement direction, and; instruments for removing hydrogen peroxide from the surface of the packaging sheet material, characterized in that said instruments for removal of hydrogen peroxide from the surface of the packaging sheet material are interposed between said instruments for application of hydrogen peroxide and said instruments for irradiation of the packaging material with light including at least one UV wavelength between 200 nm and 320 nm, by means of which a residual or trace amount of hydrogen peroxide absorbed by or located adjacent to any microorganism present in said packaging sheet material is directly objectified with UV radiation.

BRIEF DESCRIPTION OF THE DRAWINGS Below, the features and advantages of the invention will become apparent from the following detailed description of the invention and from the accompanying figures drawings in which: Figure 1 is a schematic view of the apparatus according to the invention; Figure 2 is a schematic, enlarged sectional view of a portion of packaging sheet material irradiated with UV light according to the methods of the prior art, and; Figure 3 is a schematic, enlarged sectional view of a portion of packaging sheet material irradiated with UV light according to the method of the present invention.

IDEAL FORM OF CARRYING OUT THE INVENTION With reference to the drawing of Figure 1, the apparatus according to the invention is shown together with a packaging sheet material to be sterilized. Although, in the illustrated example, the packaging material is in the form of a net 1, it will be appreciated that the material may also be in the form of a sheet cut. As shown in Figure 3, network 1 is a laminated multi-layer material of the type commonly used for aseptic packaging of pourable food products. The laminated structure has a base layer of fiber 20 made of a material such as paper, and heat sealable layers 21, 22 made of plastic materials such as polyethylene, provided on each side of the base fiber layer 20. When the material of packaging is to be used for aseptic packing of pourable foods such as milk treated at ultra high temperature (UHT milk), the face of the packaging material intended to be put in contact with the food product is also provided with a layer of barrier material 23, such as eg, aluminum, which is re-coated with an additional heat-sealable layer 24 of plastic materials such as polyethylene.

The network 1 is moved in a forward direction, indicated by the arrow 2, and guided in its trajectory, by conventional instruments which are not part of the present invention and thus are not illustrated. As clearly shown in Figure 1, the apparatus according to the invention includes instruments for applying hydrogen peroxide to the surface of the packaging sheet material 1, moving in the direction of advance 2, which are preferably constituted by a tub 3 containing liquid hydrogen peroxide 4. The hydrogen peroxide 4 in the tub 3 can have a concentration of above 50% by weight, and preferably has a concentration of from 10% by weight to 50% by weight, more preferably a concentration of from 20% by weight to 40% by weight. A conventional roller 5 is provided in the tub for guiding the packaging material 1. As also schematically shown in Figure 1, the instruments 6 are also connected to the bath 3 to maintain the hydrogen peroxide at a temperature preferably comprised between 15 degrees Celsius and 80 degrees Centigrade, and may be constituted by a thermostatically controlled conventional heating mechanism 6 as is commonly used in the technical field of the invention as those present in the TBA / 19® liquid food packaging machines and TBA / 21® cited above, available from Tetra Brik Packaging Systems, Via Dolphin 1, Modena, Italy.

In the apparatus according to the invention, the depth of the bath with hydrogen peroxide can be reduced with respect to conventional baths, and the hydrogen peroxide 4 in bath 3 preferably defines a liquid column having a height of less than 50 cm. One skilled in the art will appreciate that other instruments for applying the hydrogen peroxide liquid or vapor to the surface of the packaging material can also be used, as spray instruments.

The instruments for irradiating the packaging sheet material with light, including at least one UV wavelength between 200 nm and 320 nm, are located at the lower end of the bath 4, with respect to the direction of advance 2, and comprises a UV light source 7. According to the preferred embodiment of the invention, the UV light source 7 for irradiation of the packaging sheet material may comprise a monochromatic source of UV light having a wavelength of 222 nm . The monochromatic source of UV light having a wavelength of 222 nm preferably comprises at least one excimer lamp. Such lamps are available from Heraeus Noblelight, Kleinostheim, Germany. Alternatively, a polychromatic UV light source can also be used. Such polychromatic lamps are manufactured, for example, by Berson UV-techniek, De HuufTes 23, NL-5674 Nuenen, The Netherlands. Other lamps or lasers can also be used which emit light in the UV wavelengths.

As shown in Figure 1, instruments 8 are also provided for the removal of hydrogen peroxide from the surface of the packaging sheet material 1, or, as will be explained here below, reducing hydrogen peroxide on the surface of the packaging sheet material to a minimum. In the illustrated example, the instruments 8 for removal of the hydrogen peroxide from the packaging sheet material preferably comprise at least one air knife 9 for driving air into the sheet of the packaging material 1. Such air knives are known from United States patent No. 4603490 to Hilmersson et al, and have a chamber 10 including an air inlet 11 and an air outlet 12 for an air flow, an inlet material 13 and an outlet material 14 for a network of packaging material 1, and a baffle plate 15 disposed on the air outlet 12 at an angle in relation to the travel path of the network 1 through the chamber 10.

The air driven in network 1 in the air knife is preferably heated to a temperature of 80 degrees centigrade to 150 degrees Centigrade. It will be appreciated that other hydrogen peroxide removal instruments of network 1 can also be used. For example, conventional rubber rollers or imitation rollers can also be used in addition to or instead of the air knife. Other instruments can also be used for the generation of a flow of hot air suitable for the evaporation of hydrogen peroxide. However, instruments for driving warm air into the network of the packaging material are preferred, especially where the network has any part, such as the package opening devices injection molded directly into the network, which can affect the efficiency of the network. the rubber rollers.

An "important feature of the present invention resides in the specific location of the instruments for the removal of excess hydrogen peroxide from the network surface of the packaging material. 1. As clearly shown in Figure 1, the instruments for the removal of the excess hydrogen peroxide 8 are interposed between the instruments for applying hydrogen peroxide, constituted in the example illustrated by the bath 3, and the instruments 7 for irradiation of the packaging material with light including at least one UV wavelength of between 200 nm and 320 nm. The reason for this location of the instruments for the removal of hydrogen peroxide is the following: With reference first of all the drawings of the figure 2, there is illustrated an enlarged sectional view of the portion of a laminated packaging sheet material with multiple layers as the network 1 described above, where the identical layers of the laminated structure are identified by the same reference numerals. Additionally, the reference number 30 schematically indicates microorganisms present on the surface of the packaging material, and the reference number 31 indicates the layer of hydrogen peroxide applied to the surface of the packaging material. Figure 2 illustrates the treatment of the material of a packaging sheet according to the methods of the prior art, where the hydrogen peroxide at a concentration not greater than 10% by weight is first applied to the material of the packaging sheet. Then the hydrogen peroxide is irradiated with UV light, and the synergy between hydrogen peroxide and UV light has the known killer effect on microorganisms 30.

Figure 3 illustrates the treatment of a packaging sheet material according to the invention, wherein the hydrogen peroxide, preferably at a concentration of up to 50% by weight, and preferably from 10% to 50% by weight, is first applied to the material of the packaging sheet. Later the hydrogen peroxide is removed from the surface of the packaging material. Thus it would appear that if one irradiates the packaging material with UV light at this point, ie, in the UV irradiation zone indicated by reference number 19 in Figure 1, there could be no interaction between UV light and hydrogen peroxide. , since the last one has been removed. However, the applicant has discovered that on the contrary, the murderous effect achieved is significantly improved with respect to known techniques. This is due to the fact that although the excess hydrogen peroxide is removed from the hydrophobic material of the packaging sheet, a residual or trace amount is retained in any of the microorganisms 30a, which are believed to absorb hydrophilically the hydrogen peroxide 31a or otherwise retain the residual hydrogen peroxide. Therefore, when the material of the packaging sheet is successively irradiated with UV light, the occult interaction between hydrogen peroxide and UV light, which has the known killer effect on microorganisms, is directed specifically to the microorganisms themselves, which have hydrophilically absorbed or otherwise retained hydrogen peroxide. In addition, the removal of the protective layer of the excess hydrogen peroxide allows it to take advantage of the possibility of using higher concentrations of hydrogen peroxide than those which were considered to be maximally usable by the prior art.

In other words, instead of irradiating the entire layer of hydrogen peroxide for the purpose of killing any microorganisms contained therein, as taught by the prior art, in accordance with the invention, the excess layer of hydrogen peroxide 31 is removed and only the residual hydrogen peroxide located in, on or adjacent to any of the microorganisms 30a present on the surface of the packaging material will be directly aimed at the UV radiation. It will be understood that the positional relationship between the residual hydrogen peroxide and the microorganisms shown in Figure 3 is purely schematic and representative of what is believed to be occurring.

Therefore, when the packaging material is irradiated with UV light, instead of having an excess layer of hydrogen peroxide protecting the microorganisms, the irradiation of the UV light is directed to the residual hydrogen peroxide absorbed by or located adjacent to the the microorganisms. The removal of the excess layer of hydrogen peroxide in practice has the surprising effect of significantly increasing the efficiency of the sterilization process.

The method according to the invention, carried out with the apparatus described above, will now be described: First of all, the hydrogen peroxide, preferably liquid hydrogen peroxide at a concentration of up to 50% by weight, preferably from 10% by weight to 50% by weight, and more preferably at a concentration of 20% by weight to 40% by weight, it is applied to a packaging sheet material. According to the preferred embodiment of the invention, this is achieved by immersing the material of the packaging sheet in a bath of hydrogen peroxide at a temperature comprised between 15 degrees Celsius and 80 degrees Celsius, with a time interval of 0.5 seconds. to 2 seconds. During this time, it is believed that the hydrogen peroxide is absorbed hydrophilically in, or passes in some way to be trapped adjacent to, or on any of the microorganisms present in the packaging material. Preferably, the height of the liquid column of hydrogen peroxide in the bath does not exceed 50 cm on the material of the packaging sheet. Although deeper hydrogen peroxide baths can be used, this relatively short residence time and moderate depth obviates problems related to soaking the ends or igniting the hydrogen peroxide in the fibrous layer of the laminated packaging material.

Later, the excess hydrogen peroxide is removed from the material surface of the packaging sheet, preferably by driving on it an air stream heated to a temperature of 80 degrees Celsius to 150 degrees Celsius, to reduce the peroxide of hydrogen on the surface of the packaging material to a minimum. This removes the excess hydrogen peroxide from the surface of the packaging material, but a trace amount of residual hydrogen peroxide is retained in any of the microorganisms present on the surface of the packaging material. Once the excess hydrogen peroxide has been removed from the surface of the packaging material, the material is irradiated with light including at least one UV wavelength between about 200 nm and 300 nm. According to the preferred embodiment of the invention, the material of the packaging sheet is irradiated with UV light at a wavelength of 222 nm, and more preferably, the UV light source is an excimer lamp. In this way, it has been found that it is possible to directly target the residual hydrogen peroxide trapped in any of the microorganisms present in the packaging sheet material with UV radiation. The use of an excimer lamp has the additional advantages of instantaneous activation and deactivation and without significant heat emission. From the experimental tests, it has been observed that when hydrogen peroxide is not reduced to a minimum (ie, to a residual or trace amount in any of the microorganisms in the packaging material to be sterilized) prior to irradiation with UV light, an extremely lower results than that which has been achieved in comparative examples which have been carried out in accordance with the invention.

The sterilization system according to the invention is fully compatible with modern aseptic high-speed liquid food packaging machines, producing up to 18,000 or more packs per hour, where the packaging material moves at a speed of, or greater than 81.65 cm per second (48,990 meters per minute).

The present invention can be modified subsequently, without departing from the scope of the appended claims.

Having described the invention as above, the contents of the following are declared as property:

Claims (19)

1. The method of sterilization of a material of '-. packaging sheet, comprising the steps of; -application of hydrogen peroxide to a packaging sheet material, e; -radiation of the material of "packaging sheet with light including at least one UV wavelength between about 200 nm and 320 nm, characterized in that it comprises the intermediate step of removing the hydrogen peroxide from the surface of the sheet material. packaging, while retaining a residual or trace amount in any of the microorganisms, after the step of applying the hydrogen peroxide and before the step of irradiating the packaging material, where said residual amount or trace of hydrogen peroxide absorbed by or located adjacent to any of the microorganisms present in said material of the packaging sheet is directly targeted with UV radiation.

2. The method according to claim 1, characterized in that said step of applying the hydrogen peroxide to said packaging sheet material comprises the application of liquid hydrogen peroxide at a concentration of up to 50% by weight.

3. The method according to claim 1, characterized in that said step of applying the hydrogen peroxide to said packaging sheet material, comprises the application of liquid hydrogen peroxide at a concentration of 20% by weight to 40% by weight.

4. The method according to claim 1, 2 or 3 characterized in that said step of applying the hydrogen peroxide to said packaging sheet material comprises the step of immersing said material from the packaging sheet in a bath of hydrogen peroxide to a temperature between 15 degrees Celsius and 80 degrees Celsius, for a time interval of 0.5 seconds to 2 seconds.

5. The method according to claim 1, characterized in that said intermediate step of removing excess hydrogen peroxide from said packing sheet material comprises the impulse of a stream of heated air, heated to a temperature of 80 degrees centigrade to 150 degrees. Celsius in said material of the packaging sheet.

6. The method according to claim 1, characterized in that said step of irradiating the material of the packaging sheet with light including at least one UV wavelength, consists in irradiating said material from the packaging sheet with polychromatic UV light.

7. The method according to claim 1, characterized in that said step of irradiating the material of the packaging sheet with light including at least one UV wavelength, consists in irradiating said material from the packaging sheet with UV light at a length of 222 nm wave.

8. The method according to claim 7, characterized in that said step of irradiating the material of the packaging sheet with UV light at a wavelength of 222 nm comprises irradiating said material from the packaging sheet with an excimer lamp.

9. The method according to one or more of claims 1-8, characterized in that said material of the packaging sheet is a network unwound from a spool.

10. The method according to one or more of claims 1-8, characterized in that said material of the packaging sheet is blank.

11. An apparatus for sterilizing a material of the packaging sheet according to the method defined in claims 1-10, comprising; - instruments for the application of hydrogen peroxide to a material of the packaging sheet moving in an upward direction, - instruments for irradiating the material of the packaging sheet with light including at least one UV wavelength between 200 nm and 320 nm, arranged downstream of said instruments for the application of hydrogen peroxide, with respect to said upward direction, and; - instruments for the removal of hydrogen peroxide from the surface of the packaging sheet material, characterized in that said instruments for the removal of hydrogen peroxide from the surface of the packaging sheet material are interposed between said instruments for the application of hydrogen peroxide and said instruments for irradiating the packaging material with light including at least one UV wavelength between 200 nm and 320 nm, where a residual amount or trace of hydrogen peroxide absorbed by or located adjacent to any of the microorganisms present in said packaging sheet material is directly targeted with UV radiation.

12. An apparatus according to claim 11, characterized in that said instruments for the application of hydrogen peroxide to said packaging sheet material comprise a bath containing liquid hydrogen peroxide at a concentration of up to 50% by weight.

13. An apparatus according to claim 11, characterized in that said instruments for the application of hydrogen peroxide to said packaging sheet material comprise a bath containing liquid hydrogen peroxide at a concentration of 20% by weight to 40% by weight.

14. An apparatus according to claim 12 or 13, characterized in that it comprises instruments for the maintenance of said bath with hydrogen peroxide at a temperature comprised between 15 degrees Celsius and 80 degrees Celsius.

15. An apparatus according to claim 12, 13 or 14, characterized in that said hydrogen peroxide in said bath defines a liquid column having a height of less than 50 cm in said bath.

16. An apparatus according to claim 11, characterized in that said instruments for the removal of hydrogen peroxide from said packaging sheet material comprises at least one air knife to drive the air in said sheet of packaging material at a temperature of 80 degrees Celsius at 150 degrees Celsius.

17. An apparatus according to claim 11, characterized in that said instruments for irradiating the material of the packaging sheet with light including at least one UV wavelength between 200 nm and 320 nm comprise a monochromatic source of UV light having a length of 222 nm wave.

18. An apparatus according to claim 17, characterized in that said monochromatic source of UV light comprises at least one excimer lamp.

19. An apparatus according to claim 11, characterized in that said instruments for irradiating the material of the packaging sheet with light including at least one UV wavelength comprise a polychromatic UV lamp.