Patent Application
20170136135
The invention relates to the field of the sterilization of caps or necks of containers.
More particularly, the invention relates to a method and a system for decontaminating caps or necks of containers that make it possible to cover in an optimal manner all of the surfaces of these caps or necks.
Containers such as tubes, jars, flasks, cardboard food cartons or bottles made of PET (polyethylene terephthalate) are most often intended to contain common products of consumption, for example beverages, pharmaceutical products, or cosmetic products. Containers, such as bottles (in particular made of PET), are typically obtained via a stretch-blow-molding method starting from parisons, for example preforms or intermediate containers that have previously already undergone a first forming operation. The parisons as well as the caps of the containers are initially stored in a non-sterile environment.
The cardboard food cartons comprise a plugging device, consisting of a connected neck, closed by a plug. The manufacturing of a carton generally comprises a step of gluing the neck at the level of an opening located on one of the faces of the carton. Generally, these cartons, their necks, as well as the caps that are designed for them are also initially placed in a non-sterile environment. Consequently, before any filling and closing of the containers, the latter, their necks, as well as their caps should first undergo a method of decontamination in a sterilization chamber.
One known approach consists in spraying a sterilizing agent on the inside surfaces of the caps, necks and containers, for example hydrogen peroxide (H2O2), and in causing its evaporation by thermal action. Such an approach calls for spraying the agent over all of the surfaces of the containers, necks and caps; however, certain surfaces remain difficult to reach. Furthermore, the containers/necks/caps should be exposed to the agent for a predetermined time that is both long enough to ensure an effective sterilization, but also short enough so as to limit any damage by heating, running the risk of impairing these surfaces. Finally, such a method requires, if appropriate, a rinsing step so as to ensure that any trace of the product has been eliminated. Such an approach involves extended treatment times and turns out to be complex to implement.
Other known methods consist in carrying out the step of sterilizing containers via an accelerated electron bombardment on their surfaces. These methods make it possible to break the DNA bonds of any microorganism, or to create secondary particles that will then react with the microbial cells, thus leading to their elimination.
Contrary to the chemical route, these methods do not necessitate the rinsing step and do not leave any potential residual trace of chemical agent. In addition, the use of a low-energy electron beam (less than 1 MeV) makes it possible to limit the interactions with the material of the object that is to be decontaminated. By way of example, the document JPH06142165 proposes irradiating an object of complex shape, such as a cap, by a low-energy electron beam. Accelerated electrons form this electron beam, some of whose electrons collide with the gas molecules of the irradiated medium, thus creating dispersed electrons. After propagation, the electron beam, consisting of direct and dispersed electrons, then reaches the surfaces of the object and sterilizes them. The irradiated surfaces of the object furthermore induce reflected and/or secondary electrons that make it possible to sterilize the surfaces that are not directly irradiated.
However, the use of a low-energy beam involves a beam current (i.e., an anode current) of low value, most often on the order of about 10 mA. With these current values being low, the quantity of accelerated electrons turns out to be limited, just like their penetration into the material (several μm) and their back-scattering. So as to ensure the complete elimination of any microorganism, a minimal electron dose is to be produced. Consequently, so as to deposit a sufficient lethal dose of electrons on the surface of the object that is to be treated, generally on the order of about 10 kGy, a treatment time of several seconds is usually necessary. The treatment time of an irradiated object is a particularly critical parameter. Actually, an extended time of exposure of an object to electronic radiation runs the risk of creating undesirable effects on the object, namely discoloration, degradation, cross-linking phenomena, or else migration of odors. The approaches of the state of the art only manage to limit these problems partially, however.
One object of this invention is to eliminate all of the above-mentioned drawbacks.
Another object of this invention is to cover all of the surfaces of caps or necks of containers with complex shapes, having zones that cannot be covered directly by an incident electron beam.
Another object of this invention is to reduce the decontamination time of the caps or necks of containers with complex shapes, while improving the effectiveness of treatment, i.e., the bacteriological reduction rate, on the surfaces of these caps or necks of containers.
For this purpose, a method is proposed, according to a first aspect, for decontaminating plugs or necks of containers by electron bombardment, each cap comprising a roof, a body projecting from a peripheral edge of the roof, this body having an opening opposite the roof, ribs projecting from an inside face of the body and/or an inside face of the roof, each neck comprising ribs and an opening, the ribs having shadow zones, with this method comprising:
Various additional characteristics can be provided, by themselves or in combination:
According to a second aspect, a system for decontaminating caps or necks of containers by electron bombardment is proposed, each cap comprising a roof, a body projecting from a peripheral edge of the roof, with this body having an opening opposite to the roof, ribs projecting from an inside face of the body and/or an inside face of the roof, each neck comprising ribs and an opening, with the ribs having shadow zones, this system comprising:
Advantageously, this system comprises a device for transport of caps that are adjacent to one another, along a transport path and at a predetermined speed.
Advantageously, in this system, the transport device is created by a set of rails.
Other objects and advantages of the invention will become evident from the description of embodiments, provided below with reference to the accompanying drawings in which
According to various embodiments, the electron flow/beam at the exit of the gun is formed by a set of electrons, with the latter being accelerated via the application of a potential difference between two electrons, respectively a cathode and an anode. The cathode is placed in a closed space 5, for example a “vacuum” chamber, i.e., at a pressure of very low value, for example less than 10−5 bar, ensured by a pumping device.
Advantageously, the creation of such a vacuum prevents the potential collision of electrons with gas molecules, then running the risk of creating a loss of energy for these electrons. The pumping device is connected to the space that is closed by means of a pipe 6. The anode constitutes one of the outside faces of the closed space under vacuum. The electron stream can be emitted, by way of example, in the direction of the anode by an explosive emission cathode, with this cathode and anode constituting a diode. By way of non-limiting examples, the explosive emission cathode that constitutes the diode can be made of graphite, stainless steel, copper, carbon or any other material that is known for the production of this type of electrode. Advantageously, this cathode does not comprise a filament.
In contrast to the filament diodes, the use of an explosive emission cathode diode has the following advantages:
The anode 7 is placed downstream in relation to the cathode in the direction of movement of the electrons and is made in the form of a unit of conductive metal, for example copper.
So as to allow the accelerated electrons to pass into the atmosphere, the former is pierced in its center and covered by a fine metal sheet 9, typically with a thickness on the order of several tens of μm, able, for example, to be made of titanium or aluminum. The thickness of the metal sheet 9 is selected in such a way as to make airtight the gap between the cathode and the anode 7, while allowing accelerated electrons coming from the cathode and impacting this sheet to pass through it.
The thus produced anode 7 constitutes an electron bombardment window 8 that makes possible the passage of accelerated electrons between the gap 10 of the closed space and an outside, for example gaseous, environment 11, such as ambient air. Advantageously, the way in which the conductive metal unit of the anode 7 is pierced conditions the shape of the electron beam that passes through the surface of the metal sheet 9 of the anode 7. Thus, the form of the electron beam and therefore the opening of the electron bombardment window 8 can be selected according to different geometries, by way of non-limiting examples in rectangular, circular or else annular shape.
By way of example,
In addition, it will be ensured, for the preceding reason, that the sheet 9 covering the anode 7 will be kept at a low enough temperature via the installation of suitable cooling means, not shown. The anode 7 can be designed, for example, in such a way as to comprise heat dissipation zones, or else be cooled by having a cooling fluid circulate along the latter through channels.
Advantageously, the electron beam that is obtained at the exit of the electron gun is homogeneous enough to cover all of the exposed surfaces of the object that is to be treated. By way of example, the surface of the electron bombardment window 8 is sized in such a way as to cover a surface that is considerably larger than the exposed surface of the bottom of a cap 2 that is centered in relation to this window 8.
The electron gun further comprises power-supply means, making it possible to establish a potential difference between the anode 7 and the cathode, so as to accelerate the electrons emitted by the cathode. The cathode is, for example, fed by an electrical energy source (not shown), while the anode 7 is grounded. According to various embodiments, so as to generate a pulsed electron flow at the exit of the electron gun, a continuous electrical energy source will be used, for example a high-voltage power supply coupled to means making it possible to store the electrical energy, for example a capacitive or inductive storage.
By way of example, a Tesla transformer coupled to a shaping line PFL (English acronym of “Pulse Forming Line”), or any other power-conditioning device, for example a Marx generator, is used. Advantageously, a switch makes it possible to control the pulse time (pulse) of the electrical energy of the beam, stored for a charging period of the electron gun. This switch is coupled to a conductor, placed in an insulation sheath. By way of example, in
A high-intensity pulsed electron flow is therefore obtained at the exit of the electron bombardment window 8. Advantageously, the use of a pulsed mode coupled with a low-energy electron beam (less than 1 MeV) makes it possible, in contrast to a continuous mode, to reduce the electrical insulation stresses of the electron gun and consequently to make it more compact. By way of example, effective electrical insulation of the transformer and the conductor is carried out via insulation by oil, and a thin steel or lead shield.
Advantageously, the pulsed electron beam that is obtained at the exit of the electron gun is used to bombard caps 2 of containers of complex shape, thus making possible their decontamination of any microorganism. Here, cap of complex shape is defined as any cap that comprises shadow zones, i.e., zones that cannot be reached directly by incident diffused electrons.
In the embodiments described below, the electrons obtained at the exit of the electron gun are diffused in air (external environment 11) and the caps 2 that are covered in this same environment. However, it is understood that any other gaseous or vacuum environment 11 can be used for the diffusion of electrons and the decontamination of caps 2.
According to various embodiments, caps 2 of complex shapes are brought into a sterilization chamber 4, in front of the electron bombardment window 8 of the electron gun, with the opening of the caps being turned toward this window 8. Sterilization chamber is defined as a hermetic and sterile closed space, comprising sterilization/decontamination means. For example, with reference to
According to an embodiment that is illustrated in
Advantageously, such a rail system makes it possible to ensure that the opening of the caps 2 of the containers is well turned toward the electron bombardment window 8 of the electron gun, during the passage of the caps 2 under the former. However, any other transport device 3 that makes it possible to ensure this arrangement of caps 2 could be used—by way of non-limiting example a pneumatic transport device. According to another embodiment, the caps 2 are positioned step by step under the electron bombardment window 8.
Advantageously, the caps 2 of containers that pass (or that are positioned) in front of the electric bombardment window 8 undergo an operation of bombardment by the pulsed electron beam that is generated at the exit of the electron gun.
A cap of complex shape, such as the one that is illustrated in this figure, typically comprises:
According to various embodiments, the cap 2 is a single-material unit that can be made of polyethylene terephthalate (PET), high-density polyethylene (HDPE) or polypropylene (PP), or any other thermoplastic polymer. This type of cap 2 comprises shadow zones 21, i.e., surfaces that cannot be reached directly by an incident particle beam, by way of examples the zones below the projecting parts of the body 18, the skirt 27 and the roof 17 of the cap 2 according to the direction of movement of the particles.
The pulsed electron beam at the exit of the electron gun undergoes a diffusion in the direction of the caps 2 that pass (or are positioned step by step) in front of the electron bombardment window 8. The diffusion of the electrons is conditioned by the propagation environment. Thus, in one embodiment, when the sterilization chamber 4 is created under a vacuum-type external environment 11, the electrons that come from the electron gun constitute a beam that is diffused in a rectilinear manner and reach directly via the opening the surfaces of the cap 2 with a complex shape, first sterilizing the inside exposed surfaces that are reached by, for example, the roof 17 of the cap or the inside surfaces of its body 18.
In the embodiment shown in
Advantageously, the primary electron beam is homogeneous enough to impact all of the exposed surfaces of the cap 2.
Based on the trajectories of the primary electrons, different physical phenomena are then observed:
The container neck 30 that is illustrated has a complex shape and comprises the following elements:
The collar 31, the transfer ring 32, and the threads 33 all form projecting ribs (helicoidal in the case of the threads 33), although with various radial extensions.
This type of neck 30 also comprises shadow zones 21, i.e., surfaces that cannot be reached directly by an incident particle beam, by way of examples the zones below the collar 31, the transfer ring 32, and threads 33. The rim 34 and the inside surface 35 are exposed to exposed zones of the neck 30, i.e., zones that can be directly reached by a primary electron beam that comes from the electron bombardment window 8.
Just as in the case of the decontamination of the caps, the following physical phenomena are observed:
Thus, the primary electrons make it possible to decontaminate the exposed parts of the neck 30, while the shadow zones 21 are decontaminated using back-scattered electrons.
Advantageously, the back-scattered electrons make it possible to reach the shadow zone of the cap 2 and/or the neck 30 by their trajectories, and have high enough energy to be absorbed by the material of these zones, thus making possible their decontamination. Actually, the use of a pulsed electron flow makes it possible at the same time to obtain a high-intensity flow of electrons, ensuring the deposition of a sufficient lethal dose in the shadow zones, without thereby degrading the exposed surfaces that are exposed to the primary electron beam: the time of exposure of the cap 2 and/or the neck 30 to the electron bombardment is actually reduced to the minimum that is possible. In addition, it is advisable to note that the more heavy atoms a material comprises, the more electrons will be back-scattered by this material. A decontamination of caps and/or necks of containers with complex shapes by back-scattering of electrons is therefore particularly advantageous for caps and/or necks of containers made of the following materials: PET, HDPE, or PP.
One example of a set of parameters relative to the electron gun making it possible to obtain a pulsed electron flow and a back-scattering of electrons that can decontaminate caps 2 and/or necks of containers of complex shapes is provided below. So as to illustrate the advantages of the embodiments described above, these parameters are compared in relation to a configuration that relates to the current state of the art, using a continuous electron flow for the decontamination. The state of the art being considered is here an electron gun with scanning that uses a continuous electron beam for decontaminating caps. The assumption here is that the total treatment time for decontaminating a cap with such a gun is 1 second so as to provide a sufficient lethal dose of electrons and to cover all of the shadow zones. A potential difference of 250 kV is applied to the terminals of a filament diode of this gun, making it possible to obtain an anode current of 50 mA. By way of example, a continuous flow of electrons irradiating a cap for a period of 1 ms so as to calculate the electron dose received by the cap during this interval is considered.
Regarding the embodiments of the gun with pulsed electron flow of this application, the configurable parameters of this gun are the following: the number of pulses, the pulse time of a pulse, the discharge voltage that is applied to the terminals of the diode, the current of the anode of the diode, and the frequency of the emissions of the pulses. In this example, 10 pulses of 10 ns, generated at a frequency of 100 Hz, are used by applying a potential difference of 250 kV to the terminals of the diode with an anode current of 5 kA. Furthermore, the recharging time of the electron gun before being able to generate a new pulse is approximately 10 ms here.
Finally, a cap of a mass of 3 g and comprising a back-scattering coefficient of 0.07% will be assumed. The results that are obtained are summarized in the table below.
The example provided above illustrates several advantages that result from using a pulsed electron gun. In particular, the use of an anode current with a much higher value than the one used in the state of the art makes possible very short irradiation times while making possible the distribution of a much higher electron dose, here ten times more than in the state of the art. Thus, the quantity of electricity associated with back-scattered electrons is also higher and makes it possible to decontaminate correctly the shadow zones of the cap. In contrast, with the electron doses received in the state of the art being smaller, the same holds true for the quantity of energy of back-scattered electrons, which greatly limits the covering of shadow zones. In addition, it is observed that the use of a pulsed electron flow makes possible much shorter treatment times and therefore the decontamination of a much higher cap number during the same time period.
Experimental works for the purpose of decontaminating caps and/or necks of containers with complex shapes have led to identifying values of electron doses making possible an effective treatment of these caps and/or necks of containers. Preferably, the values of these doses are in a range of between 15 and 50 kGy.
Thus, according to various embodiments, other combinations of parameters can be selected in addition to the preceding example, making it possible to obtain electron doses located in this range. The table below specifies the range of these parameters:
In addition, according to various embodiments, so as to be able also to reduce the decontamination time of the caps and/or necks of containers, a number of pulsed electron guns can be used simultaneously. Since the parallel use of several guns is known to one skilled in the art, this embodiment makes it possible in particular to be able also to reduce the application time of a pulse on the object that is to be treated.
Advantageously, the above-described embodiments make it possible to provide a method for decontamination of caps and/or necks of containers that is efficient (reduction
| Number | Date | Country | Kind |
|---|---|---|---|
| 14 55305 | Jun 2014 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2015/051296 | 5/19/2015 | WO | 00 |
