JP2004223038A - Method and device for microwave plasma sterilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize a low-cost method and device for plasma sterilization, safe and easy to handle, enabling low temperature treatment at 70°C or lower and high-speed and high-capacity treatment. <P>SOLUTION: Oxygen gas is introduced from a gas inlet 2 after a vacuum container 1 is exhausted to a predetermined pressure using a vacuum pump (not shown in figure) through a vacuum exhaust outlet 3. After providing a microwave of 2.45 GHz introduced through a waveguide 7 from a microwave generator (not shown in figure) to a slot antenna 10 for converting plasma of a surface wave plasma converter 6, the microwave is introduced into the vacuum container 1 with a microwave introducing device 5 disposed on its upper part through a silica board 11, which generates microwave discharge plasma. Using the generated oxygen plasma, the object to be sterilized disposed on a mounting table 15 is sterilized at a low temperature at 70°C or lower. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sterilization method and apparatus, and more particularly, to a sterilization method and apparatus using microwave plasma for disinfecting and sterilizing medical instruments and for food packaging containers, bags, or food products.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, techniques for disinfecting and sterilizing medical instruments and sterilizing food packaging containers, bags or foodstuffs include (1) dry heat sterilization, (2) high-pressure steam sterilization, (3) radiation sterilization, and (4) ethylene. Oxide gas sterilization and the like are known.
[0003]
{Circle around (1)} Since the dry heat sterilization method has a high temperature of 160 to 180 ° C. or higher, the target object is limited to metal or glass products, and a sterilization time of 60 minutes is required. {Circle around (2)} Since the high-pressure steam sterilization method has a high temperature of 121 ° C., the target object is limited to metal or glass products, requires a sterilization time of 20 minutes, and cannot be used for materials (such as paper) where moisture is a problem. In addition, (3) the radiation sterilization method could not be effective in places where there is no danger to the human body or where radiation is not applied. (4) The ethylene oxide gas sterilization method has problems in handling due to toxicity, flammability, and the like, and in treating residues after sterilization.
[0004]
In addition, sterilization techniques using plasma are also performed by a plurality of companies, but those which sterilize by raising the heat in principle are the mainstream, and there is a problem in handling. In some cases, an argon gas or chlorine-based gas, which is an inert gas, is introduced into a vacuum vessel, and a plasma of the gas is generated by a high-frequency power supply to sterilize the object to be treated. At the same time, plasma was generated on the surface of the discharge electrode, which was not efficient. (See Patent Document 1).
[0005]
[Patent Document 1]
JP-A-6-57352
[Problems to be solved by the invention]
As described above, the conventional sterilization method limits the objects to be sterilized, and requires long-term treatment at high temperatures, handling due to danger to humans, toxicity, flammability, etc. There was a problem with the processing of things. Accordingly, an object of the present invention is to realize a low-cost plasma sterilization method and apparatus capable of handling a sterilization apparatus safely and easily, performing low-temperature processing, enabling high-speed processing, and performing large-capacity processing. I do.
[0007]
[Means for Solving the Problems]
To achieve the above object, a microwave plasma sterilization method according to claim 1 of the present invention is configured to sterilize an object to be sterilized by high-density microwave plasma generated using oxygen gas.
[0008]
The microwave plasma sterilization method according to claim 2 of the present invention is a method for sterilizing an object to be sterilized by high-density microwave plasma generated using oxygen gas, wherein the discharge conditions for generating the high-density microwave plasma include: The microwave incident power was 1 KW, the reflection power was 20 to 30 W, the oxygen gas pressure was 10 to 200 Pa (Pascal), and the gas flow rate was 100 to 200 sccm.
[0009]
Thus, the use of high-density microwave plasma at a low temperature (70 ° C. or lower) can realize a large-volume sterilization process and a high speed (several minutes), and the use of oxygen gas improves the handling safety of the device. By irradiation for 3 minutes or more, complete sterilization of the sample, which is a sterile substance having a bacterial concentration of 10 or more to the sixth power, was confirmed. Analysis of the sterilized sample by a scanning electron microscope revealed that the surface of the bacterium was decomposed by oxygen plasma and changed its shape by plasma irradiation, and the size of the bacterium was extremely small and thin.
[0010]
A microwave plasma sterilizing apparatus according to claim 3 of the present invention is a microwave introducing apparatus for introducing microwaves from a microwave generator into an upper portion of a vacuum vessel having an oxygen gas inlet, a vacuum exhaust port, and an opening / closing door. And a surface wave plasma conversion device having a slot antenna, and a mounting table for mounting and holding an object to be sterilized is provided at the center of the vacuum vessel.
[0011]
The microwave plasma sterilization apparatus according to claim 4 of the present invention is a microwave introduction apparatus from a 2.45 GHz microwave generation apparatus in an upper portion of a vacuum vessel having an oxygen gas inlet, a vacuum exhaust port, and an opening / closing door. And a surface wave plasma conversion device having a slot antenna, and a mounting table for mounting and holding an object to be sterilized is provided at the center of the vacuum vessel.
[0012]
In this way, the use of high-density microwave plasma can achieve a large-volume sterilization process and a high speed, and the use of oxygen gas improves the handling safety of the device, eliminating the need to handle high-pressure steam and high-temperature steam. In addition, the microwave generator used in the present invention can use an oscillator equivalent to that of a microwave oven, and the price is almost the same as that of a microwave oven. Further, the manufacture of the vacuum vessel 1 has a significantly simpler structure than an ethylene oxide gas sterilization apparatus or an autoclave apparatus requiring a high-temperature steam facility, and the manufacturing cost of the apparatus can be reduced.
[0013]
The microwave plasma sterilizing apparatus according to claim 5 of the present invention is a microwave introducing apparatus for introducing microwaves from a microwave generator into an upper portion of a vacuum vessel having an oxygen gas inlet, a vacuum exhaust port, and an opening / closing door. And, a plasma generator comprising a surface wave plasma conversion device having a slot antenna is disposed, a mounting table for mounting and holding an object to be sterilized is disposed at a central portion in the vacuum vessel, and the mounting table is positioned as described above. It is configured to be connected to the elevating means for adjustment.
[0014]
In this way, the object to be sterilized is placed on the mounting table from the opening / closing door by the vertically movable operation of the elevating means, and then moved to an appropriate position, or the position of the mounting table of the object to be sterilized according to the state of the generated plasma. Can be adjusted.
[0015]
A microwave plasma sterilizing apparatus according to claim 6 of the present invention is a microwave introducing apparatus for introducing microwaves from a microwave generator into an upper portion of a vacuum vessel having an oxygen gas inlet, a vacuum exhaust port, and an opening / closing door. And a plasma generating device comprising a surface wave plasma conversion device having a slot antenna, and a mounting table for mounting and holding an object to be sterilized is disposed at a central portion in the vacuum vessel. It was configured to be installed separately.
[0016]
When a large amount of sterilization is performed in this way, the mounting table can be provided in a plurality of stages, and the object to be sterilized can be placed on the mounting table, and the gas flow rate can be appropriately increased to perform appropriate sterilization. As a result, the sterilization can be performed at higher speed and safely than the conventional method, despite the simple device.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a microwave plasma sterilizer of 2.45 GHz. FIG. 1 (A) is a front sectional view, and FIG. 1 (B) is a partially broken top view.
[0018]
A microwave introduction device 5 for introducing a microwave of 2.45 GHz from a microwave generation device (not shown) into an upper portion in a vacuum vessel 1 having a gas introduction port 2, a vacuum exhaust port 3, and an opening / closing door 4, and a surface. A plasma generation device including the wave plasma conversion device 6 is provided. The microwave introduction device 5 includes a cooling fan 8 for cooling the waveguide 7 and the quartz plate 11 and a short-circuit plunger 9.
[0019]
The surface wave plasma converter 6 includes a slot antenna 10 for plasma conversion and a quartz plate 11. Further, a pedestal 12 for mounting and holding the object to be sterilized is provided at a central portion in the vacuum vessel 1, and a metal plate 13, a ceramic 14, and a mounting table 15 for mounting the object to be sterilized are arranged on the pedestal 12. ing.
[0020]
The microwave generator used in the present invention can use an oscillator equivalent to that of a microwave oven, and the price is about the same as that of a microwave oven. Further, the manufacture of the vacuum vessel 1 may have a structure that is much easier than an ethylene oxide gas sterilization apparatus or an autoclave apparatus requiring a high-temperature steam facility.
[0021]
A specific example of the sterilization method of the present invention is performed as follows. First, the object to be sterilized is placed on the mounting table 15 of the pedestal 12 arranged at the center in the cylindrical vacuum vessel 1 having a diameter of 40 cm and a height of 40 cm. As the sterilization test samples, Bacillus subtilis and Bacillus stearothermophilus, which are the most powerful Bacillus subtilis, are used, and 48 hours for subtilis bacteria and 48 hours for Stearothermophilus bacteria. Was used for 7 days after confirming the survival and culture of the bacteria.
[0022]
After the vacuum vessel 1 is evacuated to a predetermined pressure by a vacuum pump (not shown) through a vacuum exhaust port 3, oxygen gas is introduced from a gas inlet 2. The microwave of 2.45 GHz introduced from a microwave generator (not shown) via a waveguide 7 is applied to a microwave introduction device 5 disposed at an upper portion in the vacuum vessel 1. After the microwave is supplied to the plasma conversion slot antenna 10 and guided into the vacuum chamber 1 through the quartz plate 11, microwave discharge plasma is generated.
[0023]
The discharge conditions for plasma generation at this time are: microwave incident power of 700 W, reflection power of 20 to 30 W, oxygen gas pressure of 10 to 20 Pa (Pascal), and gas flow rate of 100 to 200 sccm. The object to be sterilized mounted on the mounting table 15 was sterilized at a low temperature (70 ° C. or lower) by the oxygen plasma thus generated. In the plasma irradiation, the irradiation time was changed from 1 minute to 10 minutes.
[0024]
As a result, it was confirmed that the sample, which was a sterile substance having a bacterial concentration of 10 or more to the sixth power, was completely sterilized by irradiation for 3 minutes or more. Analysis of the sterilized sample by a scanning electron microscope revealed that the size of the bacteria was extremely small and thin due to plasma irradiation. This is thought to be due to the fact that the surface of the bacteria was decomposed by the oxygen plasma and changed its shape, and good results were obtained that were not attained in the conventional research results.
[0025]
FIG. 2 is an outline of a more practical embodiment of the device of the present invention, and shows a front sectional view. In the figure, the same members as those in FIG. 1 are denoted by the same reference numerals. 1 is a vacuum vessel, 2 is a gas introduction port, 3 is a vacuum exhaust port, 4 is an opening / closing door, 5 is a microwave introduction device, 6 is a surface wave plasma conversion device comprising a slot antenna, 7 is a direct-axis type waveguide, Reference numeral 15 denotes a mounting table on which the object to be sterilized is mounted, and 16 denotes a means for elevating the mounting table 15.
[0026]
Since the sterilization method is the same as that of the embodiment of FIG. 1, the description is omitted. However, after the object to be sterilized is placed on the mounting table 15 from the opening / closing door 4, it is generated again to move it to an appropriate position. In order to adjust the position of the mounting table 15 for the object to be sterilized according to the state of the plasma, the object is vertically movable by an elevating means 16.
[0027]
In the case of performing a large amount of sterilization, the mounting table 15 may be divided into a plurality of stages, an object to be sterilized may be placed on the mounting table 15, and the gas flow rate may be appropriately increased to perform appropriate sterilization. As a result, the sterilization can be performed at a higher speed (several minutes) and safely than the conventional method, despite the simple device.
[0028]
The microwave plasma sterilization method and apparatus of the present invention can be used for disinfecting and sterilizing medical instruments such as metal medical instruments, glass medical instruments, and resin medical instruments, for food packaging containers, bags or foodstuffs, or for general household use. It is suitable for application to air sterilizers, sterilization of new pathogens such as mad cow prions and MRS bacteria, and application as sterilizers in manufacturing processes related to medicine.
[0029]
In addition, due to future technical improvements, it is possible to sterilize microstructures such as thin tubes and to develop it into an atmospheric pressure sterilizer of any shape (pen, line, or sheet). The same effect can be expected even if it is used, and a wide range of applications and markets can be considered, such as use in public facilities as well as food manufacturing factories and medical sites.
[0030]
【The invention's effect】
As described above, according to the microwave plasma sterilization method and apparatus of the present invention, it is possible to lower the temperature of sterilization (70 ° C. or lower) by using microwave plasma, and to handle the apparatus by using oxygen gas. Safety is improved, and high pressure steam and high temperature steam need not be handled. In addition, since a large-volume sterilization process and a high-speed (several minutes) can be realized by using the high-density microwave plasma, the manufacturing cost of the apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an embodiment of the device of the present invention.
FIG. 2 is a schematic view of another embodiment of the device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Gas introduction port 3 Vacuum exhaust port 4 Opening / closing door 5 Microwave introduction device 6 Surface wave plasma conversion device 7 Waveguide 8 Fan 9 Short-circuit plunger 10 Slot antenna 11 Quartz plate 12 Base 13 Metal plate 14 Ceramic 15 Mounting table 16 lifting means

Claims (6)

A microwave plasma sterilization method comprising sterilizing an object to be sterilized by high-density microwave plasma generated using oxygen gas. The discharge conditions for generating the high-density microwave plasma are as follows: microwave incident power is 1 KW at maximum, reflected power is 20 to 30 W, oxygen gas pressure is 10 to 200 Pa (Pascal), and gas flow rate is 100 to 200 sccm. The microwave plasma sterilization method according to claim 1, wherein Plasma consisting of a microwave introduction device for introducing microwaves from a microwave generator and a surface wave plasma conversion device having a slot antenna in the upper part of a vacuum vessel having an oxygen gas inlet, a vacuum exhaust port, and an opening / closing door. A microwave plasma apparatus, wherein a generator is arranged, and a mounting table for mounting and holding an object to be sterilized is arranged at a central portion in the vacuum vessel. The microwave plasma sterilizer according to claim 3, wherein the microwave from the microwave generator has a frequency of 2.45 GHz. 4. The microwave plasma sterilizer according to claim 3, wherein the mounting table is connected to a lifting means for adjusting a position. 4. The microwave plasma sterilizer according to claim 3, wherein the mounting table is divided into a plurality of stages.

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