WO2003103729A1 - Method and apparatus for gas sterilization - Google Patents

Abstract

A method for gas sterilization which comprises a pre-treatment step of feeding a gas containing an oxygen element into a sterilization chamber under a reduced pressure and generating a plasma, a sterilization step of feeding a sterilization gas into the sterilization chamber under a reduced pressure, and a post-treatment step of again feeding a gas containing an oxygen element into a sterilization chamber under a reduced pressure and generating a plasma. The pre-treatment step significantly enhances the chemical reactivity of the surface of an article to be sterilized, and thus allows a rapid sterilization treatment by the use of a sterilization gas of a reduced concentration. The post-treatment step allows the rapid detoxification and removal of a sterilization gas. The above method combines a conventional gas sterilization method using a sterilization gas such as ethylene oxide and a polyphase alternating current discharge plasma treatment, and allows a rapid sterilization with no residual sterilization gas using a sterilization gas of a low concentration.

Description

 Specification

 Gas sterilization method and apparatus.

 Technical field

 The present invention mainly relates to gas sterilization technology for medical devices, but can be widely used for sterilization of devices such as pharmaceuticals, foods, and cosmetics. Background art

 In the medical and food fields, high-pressure steam sterilization, hydrogen peroxide gas-plasma sterilization, and ethylene oxide gas sterilization have been known in the past. It is also harmless to the environment, but has the drawback of not being able to treat poor heat and moisture resistance.

 The hydrogen peroxide gas plasma sterilization method can perform high-speed sterilization at low temperature and low humidity and has no harmful gas residue, but cannot process textiles, sponges, and celluloses that absorb or adsorb hydrogen peroxide. Hydrogen peroxide gas has low permeability and is not suitable for sterilization of long narrow cavity structures.

 In the ethylene oxide gas sterilization method, since ethylene oxide gas has better permeability than hydrogen peroxide gas' and can be sterilized even at low temperature and humidity, it is difficult to sterilize a long narrow cavity structure or steam sterilization. It has been widely used for sterilization of plastic and rubber products, but has toxicity such as carcinogenicity.

 When sterilizing medical equipment using the conventional ethylene oxide gas sterilization method, the concentration is 450 to l OOOmg / litre, humidity is 50 to 60%, and temperature is 40 to 60. Under the conditions of C, the sterilization treatment itself took 4 to 6 hours, and then the removal of harmful adsorbed residual ethylene oxide by aeration took 8 to 12 hours. For this reason, there was a problem that a long time was required for the entire process.

In addition, a large amount of highly explosive and toxic ethylene oxide gas must be used, and special care must be taken when handling it. Special equipment was required to recover the titanium gas.

 On the other hand, the inventor of the present invention has proposed a low-frequency AC power supply capable of stably generating a low-cost, large-capacity discharge (weakly ionized low-temperature plasma) disclosed in Japanese Patent Application Laid-Open No. 8-330079, A phase-controlled multi-output type AC power supply composed of a plurality of arranged (controlled / adjusted) AC outputs was filed first and further disclosed in Japanese Patent Application Laid-Open No. 10-130836 using this power supply. And a method for constructing a magnetic field disclosed in Japanese Patent Application Laid-Open No. 10-134994.

 With these power sources and electrodes, power is distributed and supplied in a time-sharing manner to a plurality of electrodes whose phases have been adjusted. Plasma generated by the phase alternating current is generated while rotating at the power supply frequency.

 Therefore, the present invention aims at realizing high-speed, residue-free sterilization using a low-concentration sterilizing gas by applying this multi-phase AC discharge plasma to a conventional gas sterilizing method using a sterilizing gas such as ethylene oxide gas. It was done. Disclosure of the invention

 In order to achieve such an object, the sterilization method of the present invention has the following constitution. First, the surface of the object to be sterilized is cleaned with chemically active oxygen to significantly enhance the chemical reactivity of the surface of the object to be sterilized. (760 atm-1/76 atm) Enables high-speed sterilization with a sterilizing gas such as ethylene oxide gas.

Next, a gas such as air is exhausted from the sterilizer, a sterile gas such as a low-concentration ethylene oxide gas is sealed in the sterilizer in a state where the gas is easily diffused under reduced pressure, and only the sterile gas such as the ethylene oxide gas is covered. Easily reach near the sterile material and sterilize with gas. Then, the remaining sterilized gas such as ethylene oxide gas is decomposed into harmless carbon dioxide and water by chemically active oxygen, and then exhausted outside the machine. As a result, the concentration of the gas used is reduced and the persistence is kept low, and the sterilization gas is made non-residual.

 [0 0 0 7]

 Here, chemically active oxygen can be easily generated in plasma in a gas atmosphere containing an oxygen element under reduced pressure (1/7600 to 1/760 atm).

 Therefore, high-speed gas sterilization without harmful residues is possible by the following steps.

 In other words, a process is provided in which the object to be sterilized (microorganisms) (stored in a sterilization pack) is left for a certain period of time in a plasma in a gas atmosphere containing oxygen element under reduced pressure (1/7600 atm / 1/760 atm). This significantly enhances the chemical reactivity of the surface of the object (microorganism) to be sterilized, and enables high-speed sterilization with a low-concentration sterilizing gas such as ethylene oxide gas.

Chemically oxygen in an active state, which is generated in plasma in a gas atmosphere containing oxygen element under reduced pressure, the pores of the sterile pack; surface of the object to be sterilized (microorganisms) passes through (~ 10 mu _m) And acts to gasify and remove water and oily layers covering the surface of microorganisms (cleaning of the surface), significantly increasing the chemical reactivity of microorganism surfaces with sterilizing gas such as oxidized titanium gas.

 The pore size of the sterilization pack is smaller than the minimum plasma size (Debye length) in ordinary weakly ionized low-temperature plasma. Therefore, the plasma cannot penetrate the pores of the sterilization pack and cannot act directly on the material to be sterilized. This is an important point to understand before applying plasma to sterilization.

[0 0 0 8] Further, the gas sterilization method of the present invention provides a step of dispersing and adsorbing a sterilizing gas such as a low-concentration ethylene oxide gas in a short time to perform a sterilization treatment, thereby greatly reducing the amount of the adsorbed and remaining sterilizing gas, and Continuously, a process is provided to decompose and desorb the adsorbed and residual sterilizing gas in plasma in a gas atmosphere containing oxygen element under reduced pressure, and the adsorbed and remaining sterilizing gas is accelerated by chemically active oxygen. Gasifies into carbon dioxide and water vapor. These two processes enable short-time sterilization and high-speed detoxification and residue-free treatment. Adsorption '' Residual sterilizing gas such as ethylene oxide gas and formaldehyde is gasified to carbon dioxide and water vapor by chemically active oxygen through the following reactions.

 For ethylene oxide:

_{2 (CH 2) 2 0 +} 50 2 → 4C0 2 + 4H 2 0 ( reaction with excited oxygen molecules)

_{(CH 2) 2 0 + 50} → 2 C0 2 + 2H 2 0 ( reaction with oxygen atoms la radical)

For Holmaldehyde:

_{HCH0 + O 2 → C 0 2} + H 2 O ( reaction with excited oxygen molecules)

_{HCH0 + 20 → C 0 2 +} H 2 0 ( reaction with oxygen radicals)

 However, carbon dioxide and water vapor can be easily dissociated into carbon monoxide, oxygen and hydrogen in the plasma.

 Here, the processing time of all the steps (about 20 minutes for the plasma pretreatment step in a gas atmosphere containing an oxygen element, about 20 minutes for the sterilization treatment step using a sterilizing gas such as ethylene oxide gas, and plasma in a gas atmosphere containing an oxygen element) About one hour is enough for the post-processing step (about 5 minutes), and the time can be greatly reduced.

 [0 0 0 9]

For replacement 規則 (rule ^ In addition, the use of low-concentration sterilizing gas such as ethylene oxide gas can reduce the danger of explosion and the toxicity of leaked gas when sterilizing gas such as ethylene oxide gas leaks out of the equipment. did.

 In addition, sterilizing gas such as water and ethylene oxide gas is passed by passing sterilizing gas through water during the process of evacuating sterilized gas such as low-concentration ethylene oxide gas used in the sterilization process using a vacuum pump. The gas was reacted to form water-soluble ethylene glycol or formalin, which made it possible to absorb and recover sterilized gas into water. Therefore, no harmful sterilizing gas is released into the atmosphere (environment), so it does not pollute the environment.

 The reaction formula of ethylene oxide or formaldehyde with water is shown below.

(CH ₂ ) ₂₀ + H _20- H0CH2CH20H (Ethylene glycol) HCH0 + ¾0-> HCH0 aqueous solution (formalin). As a method of treating sterilizing gas, in addition to the method of passing through water as described above, there is also a method of reacting with air (oxygen) to decompose into carbon dioxide and water. This decomposition is performed by a method using glow discharge air plasma under atmospheric pressure or a method in which air and low-temperature combustion are performed under atmospheric pressure using a platinum catalyst used in an exhaust gas purification system for vehicles. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partial cross-sectional view of a plasma sterilization apparatus embodying the present invention. FIG. 2 is a partial longitudinal sectional view of a plasma sterilizer embodying the present invention. FIG. 3 is a schematic diagram of a symmetrical 12-phase AC power supply embodying the present invention. FIG. 4 is a configuration diagram of a gas supply device embodying the present invention. FIG. 5 is a process curve diagram of the gas sterilization method according to the present invention. Figure 6 is a sterilization graph using D values. Figure 7 shows the sterilization reaction alkylated by ethylene oxide gas. It is a chemical formula. FIG. 8 is a graph showing the relationship between the number of bacteria and the culture time. FIG. 9 is a bar graph of N arrival time to confirm the sterilization effect of air plasma. Figure 10 is a graph of the relationship between temperature of biological indicators and air plasma discharge time. Fig. 11 is a bar graph of N arrival time to confirm the sterilization effect by heating. Fig. 12 is a bar graph of N arrival time to confirm the sterilization effect of mixed gas plasma. Figure 13 is a graph showing the relationship between the temperature of the biological indicator and the plasma discharge time of the mixed gas. FIG. 14 is a graph showing the time change characteristics of the ethylene oxide gas pressure. FIG. 15 is a table showing the amount of ethylene oxide gas adsorbed. FIG. 16 is a process curve diagram of an experiment for examining the disinfection effect of ethylene oxide gas diffusion. FIG. 17 is a bar graph of N arrival time confirming the bactericidal effect of FIG. FIG. 18 is a bar graph of the N arrival time when the discharge current in FIG. 17 is set to 60 [mA]. FIG. 19 is a process curve diagram of an experiment for examining the bactericidal effect of the air plasma post-treatment process. FIG. 20 is a bar graph of N arrival time for confirming the bactericidal effect of FIG. FIG. 21 is a process curve diagram of an experiment for examining the bactericidal effect in all treatment steps. FIG. 22 is a bar graph of N arrival time for confirming the bactericidal effect of FIG. FIG. 23 is a bar graph of N arrival time for confirming the sterilization effect when the discharge current is increased. FIG. 24 is a gas mass spectrometry spectrum in the air plasma pretreatment process. Figure 25 shows gas mass spectrometry data that constitutes air. FIG. 26 is a gas mass spectrometry spectrum without the biological indicator of FIG. 24 inserted. FIG. 27 is a gas mass spectrometry spectrum in a mixed gas plasma. Figure 28 shows mass spectrometry spectrum data for ethylene oxide gas, carbon dioxide, and carbon monoxide. FIG. 29 is a gas mass spectrometry spectrum in the air plasma post-processing step. BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

 FIGS. 1 and 2 show a partial cross-sectional view (A-A ′ plane in FIG. 2) and a partial longitudinal cross-sectional view (B-plane in FIG. 1) of the gas sterilizer embodying the present invention.

 In the gas sterilizer, twelve divided electrodes 3 having an arcuate cross section are fixed to the inner wall of a cylindrical vacuum vessel 1 via an insulating sheet 2 in close contact therewith.

 The divided electrodes 3 are circumferentially arranged with a slight gap a along the length of the vacuum vessel 1.

 The outer circumference of the vacuum vessel 1 is formed by a double tube 4, and cooling water is flowed at the time of discharge to cool the twelve pieces of divided electrodes 3 which are in close contact with the inner wall. ·

 A cylindrical metal mesh basket 5 is inserted into the inside of the vacuum vessel 1 along the axis, and an object 6 to be sterilized is put therein.

 In addition, a power receiving terminal 7 and a gas inlet 8 are provided at one end of the vacuum vessel 1, and a gas pressure gauge 9 is attached to the other end.

 The power receiving terminal 7 is connected to a symmetrical 12-phase AC power supply 10 shown in FIG.

 At this time, each phase component of the symmetrical 12-phase AC power supply 10 is connected to twelve divided electrodes 3 attached to the inner wall of the vacuum vessel 1 (inner diameter 100 mm, length ~ 500 mm).

 Furthermore, the neutral point b of the symmetrical 12-phase AC power supply 10 is connected to a mesh basket 5 (inner diameter ~ 50 mm, stainless steel 20 mesh) inserted concentrically.

 However, the neutral point b is not grounded and is kept at the floating potential. This is so that a potential difference is generated only between each divided electrode 3 and the mesh basket 5 and between the divided electrodes 3.

 Electrode numbers are given clockwise in the circumferential direction, and a phase voltage having a corresponding number is supplied to each divided electrode 3.

 As a result, a symmetrical 12-phase alternating current having a phase shifted by 1 Z 12 periods and the same amplitude is supplied to the twelve divided electrodes 3.

The main discharge occurs between each divided electrode 3 and the mesh basket 5 at neutral point potential, Both move in the direction of phase delay and rotate by the power supply frequency (60 [Hz]) per second. The plasma generated by the discharge passes through the mesh of the mesh basket 5 and enters (diffuses) concentrically toward the center.

 The plasma generation method using multi-phase AC discharge has the following features.

(a) It is possible to generate DC-like plasma with little time fluctuation without discharge pause despite low frequency.

 (b) Electric power is distributed and supplied to a plurality of electrodes having different phases in a time-divisional manner, and uniform plasma can be generated over a wide space area on a time-average basis. Plasma is generated while rotating at the power frequency.

(c) Since the frequency is low, the power supply is low cost and large capacity is easy. Large volume plasma can be generated at low cost.

 The gas inlet 8 is connected to a gas supply pipe 12 of a gas supply device 11 shown in FIG.

 Gas supply device 11 Aseptic from which various bacteria and water are removed through finoleta (HEPA: High EfficieNcy Particle Air filter, a filter with a collection rate of 0.3 μra of particles of 99.97% or more) 13 and an air drying tube 14 filled with silica gel Is introduced into the vacuum vessel 1.

 When a certain amount of air is allowed to flow and the gas pressure in the vacuum vessel 1 is kept constant:-Do not close the vacuum valve (not shown) on the exhaust side, and introduce air from the side with the flow meter 15. At this time, open plug valve V I and close plug valve V 2.

 As for the ethylene oxide gas, a liquid liquefied ethylene oxide 16 is once introduced into the vaporizer 17, gasified at room temperature, and then introduced into the vacuum vessel 1. At this time, close the plug valve V1 and open the plug valve V2.

When introducing a mixed gas of 80% carbon dioxide and 20% ethylene oxide gas into the vacuum vessel 1, reconnect the piping before the vaporizer. The gas injection speed is Adjust with plug valve V2.

 FIG. 5 shows a process curve diagram of the gas sterilization method according to the present invention.

 The gas sterilization method includes a pretreatment step of supplying plasma containing an oxygen element to a sterilization chamber under low pressure to generate plasma, a sterilization step of supplying a sterilization gas to the sterilization chamber at low pressure, and a low pressure again. It consists of a post-processing step (3) in which a gas containing oxygen element is supplied to the lower sterilization chamber to generate plasma.

 The pretreatment step (1) is a step of increasing the chemical reactivity of the surface of the material to be sterilized (microorganisms) by oxygen in a chemically active state generated in the plasma. Place the object to be sterilized 6 into the container and close the vacuum vessel 1. Here, at the time of decompression, in order to prevent water adhering to the inner wall of the apparatus from adhering to the inner wall surface of the apparatus from evaporating, the heat of vaporization prevents condensation or freezing on those surfaces. Pour hot water and preheat the inner wall temperature of the equipment to about 45 ° C.

 Next, the pressure inside the vacuum vessel 1 is reduced to about 0.02 Torr (1 / 38,000 atm) as shown by a curve 21, and the outside air is removed while removing water and bacteria through a hepa filter 13 and an air drying pipe 14. Air) into vacuum vessel 1 and fill to 0.25 Torr (1 / 3,000 atmospheres) as shown by curve 22. At this time, a gas containing an oxygen element such as oxygen or carbon dioxide other than air may be introduced into the vacuum vessel 1.

 The reason why the pressure is set at about this pressure value is that when the gas is air, the discharge starting voltage becomes minimum near this pressure value.

Next, the 12-phase AC power supply 10 was turned on to generate a 12-phase AC discharge between the divided electrode 3 and the mesh basket 5, and the plasma was generated in the _c- plasma, which diffused the plasma into the mesh basket 5. Chemically active oxygen (oxygen atomic radicals and excited oxygen molecules) penetrates the pores of the sterilization pack and acts on the surface of the object 6 to be sterilized. Desorb adsorbed substances (oil, water, etc.) from the surface of the material to be sterilized 6 Then, the surface is cleaned, and the surface of the object to be sterilized 6 is chemically activated. In this process, a certain degree of sterilization of the material 6 to be sterilized is performed. The discharge power at this time is about 150W.

 If discharge is performed continuously, problems such as an increase in gas pressure due to gas release during discharge and melting of a plastic sample due to generation of heat during discharge will occur.

 Therefore, as shown by the curves 22, 23, and 24, the discharge is performed several times intermittently in order to prevent the change of the discharge condition due to the generation of gas during the discharge plasma generation and to suppress the heating inside the device. Discharge for about 5 minutes, once exhaust the gas inside the device, reduce the pressure to about 0.02 Torr, and then introduce air to atmospheric pressure.

 This is performed about four times in one cycle, and discharge is performed for a total of about 20 minutes. This time is a length based on the assumption that the entire sterilization time is about 1 hour. Here, when the problem of generation of gas or heat is small, discharge plasma may be continuously generated.

 The sterilization process (1) is a process in which low-concentration ethylene oxide gas is diffused and adhered to the vicinity of the material to be sterilized (6). Exhaust the accumulated gas and reduce the pressure to 0. * 02 Torr as shown in curve 24.

 Next, an ethylene oxide gas (purity 100100%) is introduced into the vacuum vessel 1 and filled up to a maximum gas pressure of 7.6 Torr (1/100 atm) as shown by a curve 25. Here, when the ethylene oxide to be introduced is in a liquid state, it is received and gasified in a vaporization dish, and is prevented from being injected as a liquid into the vacuum vessel.

Next, the temperature of the double tube 4 of the vacuum vessel 1 is kept within a range of 45 to 50 degrees, and while the ethylene oxide gas is activated by heat, the ethylene oxide gas is diffused and penetrated deep inside the object 6 to be sterilized, and pretreatment 6 The surface of the object to be sterilized cleaned in the process Adsorb Len gas. In this process, the material to be sterilized by ethylene oxide gas

6. Main sterilization and sterilization are performed. Assuming that the entire processing time is about 1 hour, the diffusion time is about 20 minutes.

 In the case where the material 6 to be sterilized is a tube such as an elongated catheter having a stenotic structure, the oxidized titanium gas can be pushed into the entire stenosis structure by using the vacuum impregnation method. The vacuum impregnation method is a well-known method used to impregnate insulating oil into the interior of a transformer or a capacitor. In this case, after supplying a sterilized gas to a evacuated low-pressure sterilization chamber, the vacuum impregnation method is used. After about a minute, air at atmospheric pressure is blown into the sterilization chamber at once to push the sterilizing gas deep into the material to be diffused and permeate. After the diffusion is completed, exhaust the ethylene oxide gas inside the device and reduce the pressure to about 0.02 Torr. Here, the ethylene oxide gas that goes out of the device during the exhaust process is bubbled into water and collected as ethylene glycol.

 As shown in curve 26, the ethylene oxide gas pressure value decreases exponentially with time immediately after filling. This indicates that the ethylene oxide gas is adsorbed on the sample surface while diffusing into the vacuum vessel 1. Ethylene oxide gas is known as a highly adsorptive gas. The amount of gas reduction, that is, the amount of adsorption increases as the initial filling pressure of the ethylene oxide gas increases. In addition, the amount of adsorption when the pretreatment step (1) is performed is larger than when the pretreatment step is not performed.

 If a metal thin film (zinc, copper, iron, etc.) whose resistance changes depending on the degree of oxidation by ethylene oxide is used, the achievement of sterilization can be monitored. The degree of oxidation can be detected from the resistance value of the metal thin film, and the degree of sterilization can be estimated from the degree of oxidation. If the degree of sterilization is not sufficient, take measures such as extending the treatment time.

The post-treatment process ③ consists of chemical activation of the adsorbed ethylene oxide by the initial plasma and sterilization by it, and residual (adsorbed) ethylene oxide by the plasma. In the process of decomposing and desorbing gas, with the double pipe 4 of the vacuum vessel 1 heated, the oxidized titanium gas filled in the sterilization process was exhausted, and the pressure was reduced to 0.02 Torr as shown by curve 27. I do.

 Next, after removing water and various bacteria through a hepa filter 13 and an air drying tube 14, outside air (air) is introduced into the vacuum vessel 1 and filled up to 0.25 Torr as shown by a curve 28.

 At this time, similarly, a gas containing an oxygen element such as oxygen or carbon dioxide other than air may be introduced into the vacuum vessel 1.

 Next, air plasma is generated inside the device, and the chemically active oxygen generated in the plasma acts on the ethylene oxide remaining on the inside of the device and on the surface of the object to be sterilized 6 to be harmless to the environment. Decomposes into clean water and carbon dioxide. Since the residual ethylene oxide is small in the first place, a discharge plasma is generated for about 5 minutes.

 Here, in the initial stage of plasma generation, oxygen in a chemically active state that has passed through the pores of the sterilization pack acts on the ethylene oxide adsorbed on the surface of the material 6 to be sterilized in the diffusion process of the sterilization process. Then, it chemically activates ethylene oxide (opening the carbon-oxygen bond). As a result, a chemical reaction occurs between the surface of the object 6 and the adsorbed ethylene oxide, and the object 6 is sterilized and sterilized.

 The air plasma treatment is repeated a plurality of times as necessary. For example, if the amount of the material to be sterilized is large and the amount of ethylene oxide remaining on the surface of the material to be sterilized is large, a single air plasma treatment for 5 minutes will decompose and detoxify the remaining oxidized titanium components. May not be sufficient. In such a case, perform air plasma treatment twice or more for 5 minutes.

After one or more air plasma treatments have been completed, the gas accumulated in the vacuum vessel 1 is exhausted and reduced to 0.02 Torr as shown by a curve 29. After the pressure is applied, outside air (air) is introduced into the vacuum vessel 1 while removing water and various bacteria through a hepa filter 13 and an air drying tube 14, and the pressure is returned to the atmospheric pressure as shown by a curve 30.

 Finally, open the vacuum container 1 and remove the material 6 to be sterilized.

 Hereinafter, examples of the present invention will be described. "Sterilization in this example refers to the process of killing all microorganisms, including viruses. In practice, sterilization is operated as a probabilistic concept. erility As suraNc e Level (SAL) is set and the number and type of microorganisms (bioburden) that survive on the material to be sterilized per unit area (bioburden) and the mortality rate (required to reduce the number of bacteria to 1/10) The sterilization conditions to achieve SAL are calculated from the appropriate time and called the D value.

 Figure 6 shows an example of a sterilization graph using D values.

Now is as a SAL 10- ⁶ (100 per million) has been adopted internationally, even in the Japanese Pharmacopoeia 13 stations add catching was adopted on the same concept of "terminal sterilization how". This means that the probability that a single microorganism survives on the material to be sterilized per unit area after the sterilization operation is once in 1,000,000 times. Although the know Baioba one den be assumed to be performed beforehand a suitable microbial monitoring-rings often assumed number of bacteria of ¹⁰⁶ per unit (one million), or One lethal The speed is measured by using bacteria that are most resistant to the sterilization method, that is, indicator bacteria.

 The sterilization effect of oxidized titanium gas in this example is based on the fact that proteins (prote iN) constituting microorganisms are alkylated by ethylene oxide gas, and the chemical formula of the sterilization reaction is shown in FIG. Show.

The confirmation of the sterilization effect in this example was performed by inserting a biological indicator into the sterilizer. 3M Test TM1264 was used as a biological indicator. Oxidation inside the container with a sterile filter lid on this indicator Bacillus subtilis and against the ethyl Rengasu the most resistant strong strain (Bacillus subtil is) is 3.2x 10 ⁶ cells stored in spores state.

 After sterilization, the cells are cultured at 37 ° C for 48 hours. If the culture solution does not change color, sterilization at an international level of sterility assurance has been achieved. If not sterilized, it will turn yellow when fully grown. The ratio of the number of remaining bacteria to the initial number of bacteria, that is, the bactericidal effect in each sterilization step, can be determined by the time difference until the biological indicator is fully grown at the time of culturing.

 Here, the spore state is briefly described.

 Bacterial cells generally die when the surrounding environment is detrimental to their growth. However, certain types of bacteria survive in poor conditions, such as drought and high temperatures, when they become spores. Its resistance is strong against physical and chemical stimuli. It is covered with a thick shell with a low density of dense protoplasm and nucleus, and has strong resistance to drying heat, chemical treatments such as disinfectants, ultraviolet rays, and radiation. At 120 ° (:, 15 minutes autoclaving, all spores are completely killed, but can withstand boiling at 100 ° C.

 In bacterial culture, the bacterial growth dn at dt time is proportional to the number of bacteria and the growth time at that time.

 dn = andt

 Can be expressed as Where a is the bacterial growth constant.

 By integrating equation (1),

Replacement form (Rule 2Θ

Inn = at + c

n ^ n _Q exp (i) (2), and the equation (2) is obtained. Where n. Is the initial number of bacteria during culture.

Here, when the biological indicator is cultured, the number of bacteria when the color of the culture solution changes to yellow in a fully grown state is calculated, and the biological indicator is cultured according to the difference in the initial value of the number of bacteria. Consider the difference in the time until the solution turns yellow. Initial values are n _Q1 and n. In the case of _2, when the time until you grow bacteria count up # respectively and t _2,

N = n ₀₂ exp (af ₂ ) (4)

It is expressed as

 Figure 8 shows a graph showing the relationship between the number of bacteria and the culture time.

Paper (Rule 2 From equations (3) and (4)

Becomes According to equation (5), the time difference t ₂ _ t J in the culture result is the initial value n of the number of bacteria.

0 1, n _{Q 2} of seen to be proportional to the logarithm of the ratio.

 Therefore, the bactericidal effect in each step can be quantitatively determined from the ratio of the number of residual bacteria to the initial number of bacteria, that is, the time difference until the biological indicator is fully grown during culture.

 (Experimental example 1)

 The following experiment was performed to confirm the sterilization effect of air plasma.

 The biological indicator was set in a sterilizer, a treatment experiment using only air plasma was performed, and the sterilizing effect was examined by cultivating the biological indicator.

 On the other hand, in order to measure the temperature rise of the biological indicator due to the discharge and plasma generation, and to examine the sterilization effect due to the temperature rise, the biological indicator was put in a constant temperature bath at atmospheric pressure and heated. Confirmation of the effect An experiment was performed.

 a. Experimental method

During depressurization, the sterilizer is operated at 45 ° C under atmospheric pressure to prevent water adhering to the inner wall of the device or the surface of the basket for inserting sterilized materials from condensing on the surface due to heat of vaporization during evaporation. Preheat to a degree. Hot water is poured into the double wall of the device, or the device is heated by a strip heater wound on the outer wall of the device. Once the entire device has warmed up, insert the biologic indicator to be sterilized into the basket inside the device and insert the replacement paper (Rule 2). Then, put the biological indicator, which is the object to be sterilized, into the basket inside the device and reduce the pressure inside the device to about 0.02 [Torr] using an oil rotary vacuum pump.

 Then, air is introduced through a hepafilter and silica gel to 0.25 [Torr] while removing various bacteria and moisture. Generate a discharge, and after continuing for 5 minutes, evacuate and reduce the pressure to 0.02 [Torr], and introduce air again to 0.25 [Torr].

 This is repeated several times as one cycle of discharge treatment. The reason for performing the discharge intermittently is to prevent the discharge conditions from changing due to the pressure rise due to gas generation during the discharge, and to set the biological indicator set inside to the discharge plasma. This is to prevent overheating.

 When the discharge treatment cycle is completed, air is introduced into the experimental device (2) through the hepafilter and the silica gel until the atmospheric pressure is reached. Remove biological indicators while opening device. At this time, the surface temperature is measured with a thermocouple.

 b. Confirmation of sterilization effect by biological indicator

 The biological indicator after treatment was placed in a specified incubator, and the time required for complete propagation was observed, and the bactericidal effect in the treatment process was examined.

 Figures 9 (a) and 9 (b) show the sterilization effect of air plasma. Here, Fig. (A) shows that the effective values of the first phase discharge current (hereinafter referred to as discharge current) and discharge voltage (hereinafter referred to as discharge voltage) are 50 [mA], 270 [V], and The results are for the case where the average value of the total power over all phases (hereinafter referred to as the discharge power value) is 120 [W]. On the other hand, FIG. 7B shows the case where the discharge current value, the discharge voltage value and the discharge power value are 60 [mA], 285 [V] and 150 [W], respectively.

In FIG. 9 (b), a set of three bar graphs means that three biological indicators were simultaneously inserted into the apparatus. This is because we want to obtain the correct result from the average value of the culture data because the initial bacterial count of the biological indicator varies. According to Fig. 9 (a), when the total treatment time of air plasma is up to 15 minutes, the time to reach full propagation is slightly longer than that without treatment, but the total treatment time is 20 minutes. It can be seen that the arrival time becomes longer in a stepped manner until it reaches 7 mm. Since an increase in the time to complete reproduction ^ indicates a sterilizing effect, it is shown that a certain degree of sterilization can be achieved simply by leaving the sterile-packed object in an air plasma atmosphere for a certain period of time. However, even if this air plasma treatment time is extended, the sterilization effect does not increase.

 As shown in Fig. 9 (b), when the total treatment time of the air plasma exceeds 10 minutes, the time to reach full propagation becomes longer in a stepwise manner, and the sterilization effect is obtained in a shorter treatment time than in Fig. 9 (a). You can see that. The length of the arrival time where the processing time is longer than 15 minutes is about two hours longer than in the case of Fig. 9 (a), but there is no significant difference. Here, the discharge power to generate plasma is 150 [W], which is 25% larger than that in Fig. 9 (a). It can be said that increasing the discharge power can shorten the air plasma treatment process time as pretreatment for sterilization.

 Figure 10 shows the relationship between the container surface temperature and the discharge time of the biological indicator taken out immediately after the experiment. Here, the discharge current value is 50 [mA]. The temperature was measured by returning the thermometer to the atmospheric pressure and then pressing a thermocouple thermocouple against the surface of the indicator container that was removed.

 From FIG. 10, it can be seen that since the biological indicator container is in direct contact with the air plasma, it is heated by the plasma as the total discharge processing time becomes longer. However, the heating temperature is at most about 90 ° C, and it is considered that the effect (killing) on the biological indicator (Bacillus subtilis) in this test in a spore state by this heating is small.

c. Bactericidal effect of heating the biological indicator under atmospheric pressure. To determine whether the biological indicator is sterilized by heating the container, place the biological indicator in a thermostat at atmospheric pressure. Insert indicator Tested. A biological indicator was introduced into a thermostat at the set temperature for 30 minutes, taken out, and placed in an incubator to examine the sterilizing effect. Figure 11 shows the change in the time required to reach full breeding with respect to the temperature of the thermostat. When the temperature of the thermostat containing the biological indicator is set to 100 ° C or more, the value of the arrival time becomes longer than that of the case without treatment, and it can be seen that the sterilization effect by heating is obtained. Here, when the temperature of the thermostat reaches 130 ° C or more, the container of the biological indicator starts to deform and melt.

 Comparing the results in Fig. 11 with the air plasmas in Figs. 9 (a) and (b), the temperature and the length of time at which the time to reach full breeding begins to increase are higher and shorter, respectively.

 From this result, the bactericidal effect observed in the air plasma treatment of FIGS. 9 (a) and 9 (b) is not caused by the plasma heating of the biological indicator container, but by the presence of the air plasma itself. Can be brought about by something related to it.

 (Experimental example 2)

 The following experiment was performed to confirm the bactericidal effect when a mixed gas of 80% carbon dioxide and 20% ethylene oxide gas was used. We investigated what changes in the germicidal effect were caused by the different gases that generated the plasma.

 a. Experimental method

 After pre-heating the sterilizer at about 45 ° C under atmospheric pressure, insert a biological indicator into the experimental equipment, and depressurize the inside of the equipment to about 0.02 [Torr] using an oil rotary vacuum pump. A gas mixture of 80% carbon dioxide and 20% ethylene oxide gas is introduced into the equipment up to 0.25 [Torr]. After the discharge was generated and continued for 5 minutes, the pressure was evacuated and reduced to 0.02 [Torr], and the mixed gas was introduced again to 0.25 [Torr]. This is repeated several times as one cycle of discharge treatment.

At the end of the discharge cycle, pass through a hepafilter and silica gel. Then, air is introduced into the experimental apparatus until the pressure becomes atmospheric pressure. The indicator was removed from the instrument and the surface temperature was measured with a thermocouple. Here, considering that the initial bacterial count of the biological indicator varies, three indicators were simultaneously inserted into the apparatus.

 b. Confirmation of sterilization effect by biological indicator

 Fig. 12 shows the experimental results of the time required to reach complete propagation with respect to the total discharge time. Here, the discharge current, discharge voltage value and discharge power value are 50 [mA], 285 [V] and 125 [W], respectively.

 The discharge voltage is larger than in the case of air plasma (270 [V]). Carbon dioxide is dissociated into carbon monoxide, and some of the discharge energy is taken away, so the voltage is likely to rise to compensate for this.

 From Fig. 12, it can be seen that the total breeding arrival time ^ becomes longer than the non-treatment time when the total treatment time exceeds 10 minutes. Compared to the case of the air plasma shown in Fig. 9 (a), in the case of the mixed gas, the arrival time is longer and the processing time to start is shorter by about 5 minutes, and the arrival time after the processing time is 15 minutes or more Is about 2 hours longer. However, they are almost the same value.

 Figure 13 shows the relationship between the vessel surface temperature and the discharge time of the biological indicator taken out immediately after the experiment. Here, the data are varied because they show the values in several experiments. The discharge current value is 50 [mA]. The increase in the indicator surface temperature with respect to the total processing time is the same as that in the case of the air plasma in Fig. 10.

 The results shown in Fig. 12 and Fig. 13 show that almost the same germicidal effect can be obtained with the mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide gas as with the air plasma. . This suggests that sterilization was caused by a factor common to the two cases.

In each case, the cause of the sterilization effect is determined. It is thought to be due to oxygen being in a chemically active state. In air plasma, oxygen in a chemically active state is generated from the constituent oxygen molecules. In a mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide, carbon dioxide is dissociated into carbon monoxide and oxygen, and oxygen that is chemically active is generated.

 (Experimental example 3)

 The following experiment was performed to confirm the disinfection effect by diffusion of ethylene oxide gas.

 First, the adsorption characteristics of ethylene oxide gas in the ethylene oxide gas diffusion process were examined. Next, in a sterilization experiment by diffusion of ethylene oxide gas, the effect was examined in two cases, with and without air plasma pretreatment. (1) Adsorption characteristics of ethylene oxide gas

 a. Experimental method

 After pre-warming the sterilizer to approximately 45 ° C under atmospheric pressure, insert a biological indicator into the experimental device, and depressurize the inside of the device to approximately 0.02 [Torr] using an oil rotary vacuum pump. did.

 First, ethylene oxide gas was introduced into the apparatus to 0.25 [Torr], sealed and diffused for 20 minutes, and the adsorption characteristics of ethylene oxide gas without air plasma pretreatment were examined.

 Next, after pretreatment with air plasma, ethylene oxide gas was introduced into the apparatus up to 0.25 [Torr], sealed and diffused for 20 minutes, and the adsorption characteristics of ethylene oxide gas were examined.

 Furthermore, after pretreatment with air plasma for 10 minutes, ethylene oxide gas was introduced to several pressure values, sealed and diffused for 10 minutes, and the change in the adsorption characteristics of ethylene oxide gas due to the difference in initial concentration was investigated. Was.

b. Experimental results Figure 14 shows the change over time (adsorption characteristics) of the ethylene oxide gas pressure. Here, the data connected by the broken line is the pressure value when the oxidized titanium gas is sealed and diffused without performing the air plasma pretreatment. On the other hand, the data connected by the solid line is the data when ethylene oxide gas is encapsulated and diffused after air plasma pretreatment (total treatment time: 20 minutes).

 From Fig. 14, it can be seen that the decrease in oxidized titanium gas pressure is greater with and without air plasma pretreatment than without. The amount of ethylene oxide gas adsorbed at the end of diffusion (after 20 minutes) was calculated from the decrease in gas pressure. The calculated value was 11.6 mg for air plasma pretreatment and 4.8 mg for no air plasma pretreatment. Become. Here, the capacity in the apparatus was set to 5.5 liters, and the temperature of the ethylene oxide gas in the apparatus was set to 45 ° C.

 The increase in the amount of ethylene oxide adsorbed by the air plasma pretreatment is due to the fact that the inside of the device is cleaned by the air plasma and the surface of the object (including the biological indicator, which is the object to be sterilized) inside the device. This is probably because the chemical reactivity increased and ethylene oxide gas was easily adsorbed.

 Figure 15 shows the change in the amount of ethylene oxide gas adsorbed against the initial filling pressure. Here, the total time for air plasma pretreatment is 10 minutes, and the encapsulation and diffusion time is 10 minutes. From Fig. 15, it can be seen that the lower the initial filling pressure, the smaller the adsorption amount of ethylene oxide gas.

On the other hand, the gas pressure value after 10 minutes when the initial filling pressure value in Fig. 15 is 0.76 [Torr] and the gas pressure value at the same filling time with air plasma pretreatment shown in Fig. 14 are compared. It can be seen that the case of FIG. 14 is lower. This difference is thought to be due to the difference in the total time of air plasma pretreatment. This is because in Fig. 15 it is 10 minutes and in Fig. 14 it is 20 minutes. If the air plasma pretreatment is short (but during the time when the inside of the equipment is not sufficiently cleaned), the activation of the chemical reactivity of the inside surface is insufficient and ethylene oxide is not used. Is considered to be difficult to be adsorbed.

 (2) Sterilization effect of ethylene oxide gas diffusion

 a. Experimental method

 Fig. 16 (a) and (b) show the experimental steps for examining the bactericidal effect of ethylene oxide gas diffusion.

 Here, the initial filling pressure of ethylene oxide gas is 7.6 [Torr] and the diffusion time is 20 minutes.

 Fig. 16 (a) shows the case without air plasma pretreatment, which is a process using pure ethylene oxide gas diffusion alone. Fig. 16 (b) shows the process when air plasma pretreatment and oxidation gas diffusion are performed.

 In FIG. 16 (a), when the sterilizer was previously heated to about 45 ° C. under atmospheric pressure, a biological indicator was inserted into the apparatus in advance and heated. This is to make the temperature conditions the same in consideration of the biological indicator being heated in the air plasma pretreatment step in the step of FIG. 16 (b).

 In Fig. 16 (b), the total time of air plasma pretreatment was set to 20 minutes (4 cycles of discharge).

 b. Experimental results

 FIG. 17 shows the time to reach full propagation ^ of the biological indicator after each step treatment. Step 1 represents the air plasma pretreatment (total time 20 minutes) step, and step 2 represents the ethylene oxide gas diffusion treatment step. Step 1 + Step 2 means that two processing steps are performed successively. Here, the discharge current and the discharge voltage value in step 1 are 50 [mA] and 270 [V], respectively. The discharge power value is about 120 [W].

From FIG. 17, it can be seen that the bactericidal effect in the combined step 1 and step 2 is greater than the bactericidal effect of each step alone. Step 2, i.e., preheat the biological indicator to about 45 ° C and clean the device. In the process of introducing and diffusing low-concentration (7.6 [Torr]) ethylene oxide in the state of empty (0.02 [Torr]), even a single process has a certain sterilization effect.

 The reason why the two processes combine to provide a large sterilization effect is that the air plasma pretreatment in process 1 cleans the inside of the equipment (including the material to be sterilized) and increases the chemical reactivity of its surface. In addition, it is probable that the adsorption amount of oxidized titanium gas in step 2 increased, and the sterilization effect of ethylene oxide gas increased.

 Figure 18 shows the time required for the biological indicator to reach full propagation after each process when the discharge current was 60 mA in the air plasma pretreatment process (total time 20 minutes). Here, the discharge voltage value in step 1 is 285 [V]. The discharge power value is about 150 [W].

 As can be seen from FIG. 18, when the discharge voltage is increased, that is, when the input power is increased, in the process of combining the air plasma pretreatment step 1 and the ethylene oxide diffusion treatment step 2, the time required to reach full propagation N 48 hours or more No change for many days), indicating that complete sterilization is achieved.

 This result indicates that if the pretreatment process using air plasma is performed effectively, sterilization can be performed at a high speed (about 20 minutes) using low-concentration ethylene oxide gas. This is one of the most important results in the present invention.

 (Experimental example 4)

 The following experiment was conducted to confirm the sterilization effect in the air plasma post-treatment process.

The experimental results (1) when only the ethylene oxide gas diffusion step (2) and the air plasma post-treatment step (3) were performed without performing the air plasma pre-treatment step (1), and the results of steps (2), (3), and (3) Experimental results when all processes were performed (2) Is shown.

 (1) Experimental results with only ethylene oxide gas diffusion and air plasma post-treatment

 Figures 19 and 20 show the experimental process for examining the sterilizing effect of the short-time air plasma post-treatment process ③ added after the ethylene oxide gas diffusion process ②, and the experimental results at that time, respectively.

 Here, the initial filling pressure of ethylene oxide gas is 7.6 [Torr], and the diffusion time is 20 minutes. The air plasma post-treatment time is 5 minutes, the discharge current is 50 [mA], the discharge voltage is 270 [V], and the discharge power is about 120 [W].

 From the results shown in FIG. 20, it can be seen that the sterilizing effect that appears after the air plasma post-treatment step 3 increases as the initial filling pressure in the ethylene oxide gas diffusion step 2 increases.

 Here, when the initial pressure of filling ethylene oxide gas is 7.6 [Torr], the time to reach full propagation is 28 hours. On the other hand, 18.5 hours when only the ethylene oxide diffusion step 2 under the same conditions shown in Fig. 17 was used, and 18.5 hours when the air plasma pretreatment steps 1 (total 20 minutes) and step 2 shown in Fig. 17 were used. 28 hours. From the comparison of these arrival times, it can be seen that the sterilization effect in this step is very large and efficient, although the air plasma post-treatment step time is as short as 5 minutes.

 Practically, the point to be noted in Fig. 20 is that although the data varies, the sterilizing effect is obtained even at a sealing pressure of 3.8 [Torr]. The ethylene oxide gas concentration at this pressure is equivalent to about 1/100 of the conventional ethylene oxide gas concentration.

It is unclear how much residual ethylene oxide adsorbed in the device immediately before air plasma post-treatment process 3. The reason is that the oxidizer that was adsorbed in the process of diffusion and decompression (0.02 [Torr]) of ethylene oxide gas diffusion and adsorption process This is because part of the styrene is likely to be gasified and discharged.

 As a sterilization mechanism in the air plasma post-treatment process, the remaining ethylene oxide is activated by chemically active oxygen and the like generated in the air plasma, causing a chemical reaction with non-sterile substances. The following scenarios can be considered in which the nature is promoted.

 (1) Ethylene oxide is adsorbed in the vicinity of the material to be sterilized in the ethylene oxide gas diffusion step 2, and a part of it remains without vaporization even after evacuation.

 (2) Ethylene oxide remaining in the vicinity of the material to be sterilized impinges on high-energy electrons and ions that behave as chemically active oxygen and particles generated in the air plasma in the post-treatment process (3). Action).

 ③ The residual ethylene oxide obtains the activation energy necessary for the chemical reaction with the material to be sterilized by impact.

残留 The residual ethylene oxide that has obtained the activation energy immediately causes a chemical reaction with the nearby sterile object, and sterilizes the sterile object.

 (2) Experimental results of air plasma post-treatment when all treatment steps were performed a. If the discharge currents in the air plasma pre-treatment and post-treatment steps were the same,

Fig. 21 and Fig. 22 show the experimental process for examining the disinfection effect of the air plasma pretreatment process (1) + ethylene oxide gas diffusion process (2) + air plasma post-treatment process (3), and the disinfection results at that time, respectively.

 Here, in the air plasma pretreatment step (2) and the post-treatment step (3), the discharge current is 50 [mA], the discharge voltage is 270 [V], and the discharge power is about 120 [W].

From the results in Fig. 22, it can be seen that the addition of a short time (5 minutes) of the air plasma process (3) to the two treatment steps increases the time to complete reproduction by 6 hours. In other words, it can be seen that an efficient sterilizing effect occurs in the last step (3). It is considered that the following scenario will be added to the forefront of the scenario described above as a sterilization mechanism for the entire process.

 (1) Inside the device (including the material to be sterilized), the impact (action) of high-energy electrons and ions that behave as chemically active oxygen and particles generated in the air plasma in the pretreatment process 1 is generated. receive.

 (2) The inside of the device (including the object to be sterilized) is cleaned by the above impact (action), and the chemical reactivity inside the device is enhanced. At this time, a certain bactericidal effect also appears.

 (3) If ethylene oxide gas is diffused into the equipment with enhanced chemical reactivity in step 2, the ethylene oxide gas is likely to be adsorbed inside the equipment (including the material to be sterilized). At this time, a strong sterilizing effect, that is, a sterilizing effect appears.

 b. When the discharge current is increased in the air plasma post-treatment step Figure 23 shows the sterilization effect when the discharge current in the air plasma post-treatment step 3 is increased in all the treatment steps. Here, when the discharge current is 50 [mA], 60 [mA] and 70 [mA], the discharge voltage is 270 [V], 285 [V] and 300 [V] respectively, and the discharge power is approximately 120 [V], respectively. W], 150 [W] and 180 [W].

 From the experimental results in Fig. 23, it can be seen that if the discharge current in step 3 is too high, the time to complete propagation 〃 will be shorter, and the bactericidal effect will be reduced.

 In process (3), decomposition (to carbon dioxide, water, carbon monoxide, and hydrogen) and desorption of residual ethylene oxide in the air plasma occur simultaneously. Therefore, if the discharge current in step (3), that is, the discharge power, becomes too large, the desorption and decomposition actions become greater than the action of activating the residual ethylene oxide by the plasma, and as a result, in step (3), It is thought that the sterilization effect is reduced.

(Experimental example 5) In the air plasma post-treatment process (3), how the residual ethylene oxide is decomposed and made harmless was analyzed by analyzing the gas components in the equipment below.

 First, we investigated how the gas composition in the system changes due to the generation of air plasma in the pretreatment process. At this time, the difference in gas components between the case where an object to be sterilized (actually, a biological indicator) is inserted into the apparatus and the case where nothing is inserted is examined. The effects that occur are discussed.

 Next, gas analysis was performed on plasma using a mixed gas of 80% carbon dioxide and 20% ethylene oxide. This is for the following two reasons. One is to investigate why a sterilization effect (similar to the air plasma in the pretreatment step 1) was obtained in this mixed gas plasma as shown in FIG. The other is to understand in advance how ethylene oxide changes due to the presence of plasma under conditions where ethylene oxide gas is present at a certain known ratio. This is because the amount of ethylene oxide remaining in the apparatus after step (2) is unknown and very small, so it was expected that it would be difficult to correctly know the change in step (3). Finally, the gas analysis in the air plasma post-treatment process 3 was performed. Then, based on the data including the results of the two cases described above, based on the data, how the oxidized titanium remaining in the device is decomposed and made harmless in step (3). In this study, the reason why the bactericidal effect occurs was examined.

 The momentary gas analysis during the generation of discharge plasma was performed using a video camera to capture the mass spectrometry spectrum displayed on the monitor screen of a quadrupole mass spectrometer (Nidec ANELVA, AQA-100MPX). After the experiment was completed, the images were captured on a computer via a video capture board. Identification of gas species was performed by referring to the database of gas mass spectrometry spectra.

(1) Air plasma in pretreatment process (1) First, we investigated what changes would occur in the gas components in the equipment due to the generation of air plasma in the pretreatment step (1). At this time, the difference in gas components between the case where an object to be sterilized (actually, a biological indicator) is inserted into the device and the case where nothing is inserted is examined, and the difference is generated in the air plasma pretreatment process. The effect was studied.

 a. When biological indicators are introduced into the device

 Figures 24 (a), (b), (c) and (d) show the transition of gas mass spectrometry results in the air plasma pretreatment step when a biological indicator was introduced into the experimental apparatus. Is shown.

 Figure 24 (a) shows the mass spectrum of the gas species remaining in the analysis system (piping, exhaust, and analysis pipe), which is the base level for gas analysis.

 Figures 24 (b), (c) and (d) show the mass spectra immediately before, immediately after, and 5 minutes after discharge, respectively. Here, the horizontal axis is M / Z, M is the mass number and Z is the ionic valence. However, Z = l when neutral and Z = 2 when monovalent ions.

The initial containment gas pressure of air is 0.25 [Torr], the discharge current is 60 [mA], and the discharge voltage is 293 [V]. 'In FIG. 24 (a), a so small peak at M / Z = 18 is observed, slightly water vapor gas analysis system _{(H 2 0 = 1 X 2} + 16 = 18, Z = l) is You can see that it exists. In general, water is stably adsorbed on most vacuum equipment walls, and does not easily desorb even after long evacuation. According to Fig. 24 (b), peaks are observed at M / Z-14, 18, 28, 32, and 40 in the mass spectrometry spectrum before discharge. Here, the composition of air is 78.084% nitrogen, 20.948% oxygen, 0.938% argon, and 0.033% carbon dioxide.

Figure 25 shows the mass spectroscopy spectrum data for these gas species. Here, the reason that the spectrum peculiar to the gas type appears is that the gas is an electron beam. This is because a unique dissociation component is generated during the process of ionization and analysis. The spectrum that appears in addition to the peak that should be detected is called a fragment component.

Referring to the data in FIG. 25, in FIG. 24 (b), M / Z = 14, 28 of the scan Bae-vector in the corresponding gas species molecular nitrogen _{(N 2 = 14X2 = 28,} Z = l), M You can see that / Z = 18 is water vapor, M / Z = 32 is oxygen molecule (0 ₂ = 16X2 = 32, Z = l) and M / Z = 40 is argon atom (Ar = 40, Z = l). .

 It was confirmed that the gas components in the equipment were steam and air introduced into the equipment.

According to Fig. 24 (c), peaks are observed at M / Z = 2, 14, 18, 28, 32, 40, and 44 in the gas mass spectrometry spectrum immediately after the generation of the discharge plasma. Compared to FIG. 24 (b), new peaks appear at M / Z = 2 and 44. Referring to the spectrum data in FIG. 25, these two peaks show that M / Z = 2 is a hydrogen molecule (H ₂ = l X 2, Z = l) and M / Z = 44 is a diacid It can be seen that this corresponds to dani carbon (C0 ₂ = 12 + 16 X 2 = 44, 1 = 1).

 When comparing FIGS. 24 (c) and (b), that is, looking at the changes in the gas components inside immediately before and immediately after the start of discharge, the peak of oxygen molecules decreases in FIG. It can be seen that a new carbon dioxide peak appears and the water vapor peak increases.

Fig. 24 (Accordingly, peaks were observed at M / Z = 2, 12, 14, 16, 17, 18, 28, 32, 40, and 44 in the mass spectrometry spectrum 5 minutes after the generation of the discharge plasma. Compared with Fig. 24 (c), new peaks appear at M / Z = 12, 16 and 17. According to the spectrum data in Fig. 25, M / Z = 12 is a fragment component of the spectrum of carbon dioxide and / or carbon monoxide, M / Z = 16 is a fragment component of the spectrum of water vapor and carbon dioxide and / or carbon monoxide, And M / Z = 17 are the steam spectrum flags. It can be seen that it is a ment component.

 Here, the peak of M / Z = 28 overlaps with that of the nitrogen molecule and the carbon monoxide spectrum, but the change in the peak in Fig. 24 (d) is considered to represent the carbon monoxide spectrum. Can be For the following reasons.

 ① Since there is no change in the value of M / Z = 14, which is the fragment component of the (mass spectrometry) spectrum of the nitrogen molecule, it also changes to the main spectrum of the nitrogen molecule (M / Z = 28) There is no. Therefore, the increase in the peak at M / Z-28 is due to an increase in carbon monoxide or gas species having a fragment component there, ie, carbon dioxide.

(2) The magnitude of the M / Z = 28 fragment component of the carbon dioxide spectrum is about 10% of that of the original. The increase in the peak at M / Z = 28 is larger than the size of the main spectral component of carbon dioxide at M / Z = 44.

 When comparing FIG. 24 (d) and (c), that is, looking at the change of the internal gas components with the lapse of time of the discharge plasma generation, oxygen molecules are further reduced and almost disappear, and carbon monoxide is reduced. Appears, and the peaks of molecular hydrogen and water vapor and carbon dioxide are increasing.

 The results in Fig. 24 (d), (c) and (b) indicate that oxygen, which is a component of air, is chemically activated by the generation of air plasma and reacts with organic substances including carbon and hydrogen inside the equipment. It suggests that oxygen consumption and the production of carbon dioxide and water may occur. Here, it is considered that the dissociation of carbon dioxide and water vapor and the desorption of water adsorbed on the inner wall of the device (including the object to be sterilized) are simultaneously caused by the energy of the plasma.

 The following chemical reaction formula is conceivable.

Organic substances including C and H + 0 ₂ * (or 20) → (reaction) aC 0 ₂ + bH ₂ 0 + cH ₂ H ₂₀ (adsorbed water on the inner wall of equipment) → (desorption) H ₂ 0 (water vapor )

Some 2 C0 ₂ → (dissociation) 2C0 + 0 ₂

Some 2H ₂ 0 (water vapor) → (dissociation) 2H ₂ + 0 ₂ . Here, * represents an excited state, and a, b and c represent arbitrary integers.

 b. If no biological indicator is introduced

 Figures 26 (a), (b), (c) and (d) show the transition of the results of gas mass spectrometry spectrum in pretreatment step 1 when no biological indicator was introduced into the experimental apparatus. Show. Figure 26 (a) shows the mass spectrum of the gas species remaining in the gas analysis system, and Figures 26 (b), (c) and (d) show the mass spectra immediately before, immediately after, and 5 minutes after discharge, respectively. Shows the mass spectrum. Here, the discharge plasma conditions are the same as before.

 Fig. 24 (a), (b), (c) and (d) are compared with the analysis results in the same time zone, and the change due to the presence or absence of the biological indicator is examined.

 The gas mass spectrometry results in the gas analysis system immediately before the generation of the discharge plasma are essentially the same because they are measured under similar conditions. Slight water vapor is detected in the gas analysis system, and air and water vapor are detected in the instrument.

 The results are almost the same for the mass spectrometry spectra immediately after discharge, Figure 26 (c) and Figure 24 (c). With the start of discharge, the peak of molecular oxygen decreases, the peaks of molecular hydrogen and carbon dioxide appear, and the peak of water vapor increases.

 However, there is a difference between FIGS. 26 (d) and 24 (d), which are mass spectrometry spectra 5 minutes after discharge. In the case of Fig. 26 (d) where the biological indicator is not used, the decrease in the oxygen molecular main spectrum is smaller and the newly appearing carbon monoxide main spectrum (nitrogen molecule main spectrum) is smaller. Therefore, the magnitude of the increase is small, and the increase in the main spectrum of hydrogen molecules, water vapor and carbon dioxide is small.

Sterilization · The case of the biological indicator inserted into the device during sterilization and the sterilization filter on the mouth are made of plastic. Also, Bacillus subtilis spores stored inside the case are applied to paper. Since plastics and paper are made of organic polymeric materials (composed of C, H, 0), they readily react with chemically active oxygen and are gasified into carbon dioxide and water vapor. obtain.

 Fig. 26 (According to this result, oxygen radicals generated by plasma and biological indicators of organic substances to be chemically reacted are not introduced into the apparatus, so that the consumption of oxygen is small and the reaction Here, it can be said that even if the biological indicator is not inserted, a certain amount of oxygen is consumed and carbon dioxide and water vapor are generated even when the biological indicator is not inserted because only a small amount of dirt such as oil and fat is present inside the device. It is considered that it is attached.

 c. Consideration of sterilization process in process

 The above gas analysis results suggest that the following occurs in the air plasma pretreatment step 1.

 1) Oxygen, a constituent component of air, is chemically activated by the generation of plasma.

 2) Oxygen in a chemically active state causes a chemical reaction with organic substances attached to the inside surface of the device (including the object to be sterilized), and gasifies the attached matter and desorbs from the surface. At this time, water adsorbed on the inner surface of the device (including the object to be sterilized) is also eliminated. In this process, some of the organic substances that make up the surface of the microorganisms are oxidized, and a bactericidal effect also occurs.

 3) The inside surfaces of the equipment (including those to be sterilized) are cleaned, and the chemical reactivity of the surfaces is significantly enhanced.

The surface of the inside of the device (including the object to be sterilized) whose chemical reactivity has been significantly increased reacts with the injected ethylene oxide gas very efficiently, so that the sterilization effect of diffusion of ethylene oxide gas in Example 3 was described. As in experiments, it is thought that high-speed sterilization / sterilization can be achieved even at extremely low gas concentrations. (2) Carbon dioxide 80 ° /. A. Gas analysis experiment using mixed gas of methane and 20% ethylene oxide

Figures 27 (a), (b), (c) and (d) show the changes in the results of gas mass spectrometry in a mixed gas plasma of 80% carbon dioxide + 20% ethylene oxide ₍ Fig. 27 (a) Figures 27 (b), (c), and (d) show the results for the gas in the apparatus immediately before, immediately after, and 5 minutes after the discharge, respectively. The initial containment gas pressure of a mixed gas of 80% carbon dioxide and 20% ethylene oxide gas is 0.25 [Torr], the discharge current is 60 [mA], and the discharge voltage is 299 [V].

 Fig. 27 (a) is the same as Fig. 26 (a) and Fig. 24 (a) and shows that a slight amount of water vapor remains in the gas analysis system.

 From Fig. 27 (b), in the mass spectrometry spectrum immediately before discharge, in addition to the components shown in Fig. 27 (a), M / Z = 12, 14, 15, 16, 22, 28, 29, 43 And 44 peaks are observed. Here, as reference data for confirming the gas type in the equipment, Fig. 28 (a), (b) and (c) show the ethylene oxide gas, carbon dioxide and monoxide extracted from the database. The gas mass analysis spectrum for carbon is shown. Each spectrum is scaled with the main peak at 100.

 Referring to FIGS. 28 (a) and (b), the spectrum of M / Z = 14, 15, 29, 43 and 44 in FIG. 27 (b) corresponds to ethylene oxide, and M / Z = 12, It can be seen that the peaks at 16, 22, 28 and 44 correspond to carbon dioxide. Therefore, it was confirmed that the gas component introduced into the device was a mixed gas of carbon dioxide and ethylene oxide.

From Fig. 27 (c), in the mass spectrometry spectrum immediately after the discharge, the peaks at M / Z = 2 and 28 are larger than those in Fig. 27 (b) and smaller at M / Z = 32. A new peak is emerging. Other vectors are almost the same size Therefore, when the gas species is identified from the data in Fig. 25, the gases generated immediately after the generation of the discharge plasma are hydrogen, carbon monoxide, and oxygen. These are thought to take the energy from the plasma and cause the following reactions: ft.

2C0 ₂ → (dissociation) 2C0 + 0 ₂

H ₂₀ (adsorbed water) → (desorption) H ₂₀ (steam)

2H ₂ 0 (water vapor) → (dissociation) 4H ₂ + 0 ₂

 According to Fig. 27 (d), in the gas mass spectrometry spectrum 5 minutes after the generation of the discharge plasma, the M / Z-2, 12, 14, 16, 17, 18, 27, 28, 29 and 44 Peaks are observed in places. Compared to Fig. 27 (c), the peaks at M / Z = 2, 18, and 28 are very large, and the peak at M / Z = 44 is much smaller. When gas types are identified with reference to the spectrum data in Fig. 25 and Fig. 28, it is found that the generation of hydrogen, water vapor and carbon monoxide increases, while the carbon dioxide decreases. Now, consider ethylene oxide gas. The peak at M / Z = 15 has disappeared, the peak at M / Z = 29 has become very small, and the peak at M / Z = 43 has disappeared in the statistic results in Fig. 27 (d). . Here, the fragment spectrum of carbon monoxide overlaps with the peak at M / Z = 29, and the main spectrum of carbon dioxide overlaps with the peak at M / Z = 44. Therefore, a gas mass spectrometry spectrum characteristic of ethylene oxide as shown in FIG. 28 (a) has not been observed.

On the other hand, the small peak appearing at M / Z = 27 may be the fragment vector of ethane (C ₂ H ₆ = 30). According to the database, the mass analysis spectrum of this gas species shows that the main peak force SM / Z = 28 (100 ° /.), The first secondary peak force S 27 (33%), and the second secondary peak 29 (22%), 3rd ij peak force S 26 (23%)-and 4th sub peak is 14 (3%). In Fig. 27 (d), it can be seen that all the corresponding peaks are observed. Also, ethane is Between ren and hydrogen

C ₂ H ₄₀ + 2H ₂ → C ₂ H ₆ + H ₂₀

It can be produced by the reaction of

 From the above results, it is considered that ethylene oxide gas and carbon dioxide are decomposed by the following reaction by the energy from the discharge plasma for 5 minutes.

2C0 ₂ → (dissociation) 2CO + 0 ₂ … dissociation of carbon dioxide, generation of oxygen

2 C ₂ H ₄ 0 + 50 ₂ → (Occasion) 4H ₂ 0 + 4C 0 ₂

… Oxidation of ethylene oxide, generation of water and carbon dioxide H ₂₀ (adsorbed water) → (desorption) H ₂₀ (water vapor)… desorption of adsorbed water

2H ₂ 0 (water vapor) → (dissociation) 4H ₂ +0 ₂ … dissociation of water vapor and generation of hydrogen and oxygen Here, oxygen generated from the dissociation reaction of carbon dioxide and water vapor depends on the energy from the discharge plasma. It is considered to be activated and converted to a molecule or atom that is chemically more reactive.

0 ₂ → (excitation) 0 ₂ … Generation of chemically active oxygen molecules

0 ₂ → (dissociation) 0 + 0… Generation of chemically active oxygen atoms b. Consideration of sterilization process from gas analysis results

 As already described with reference to FIG. 12 in Example 2, almost the same sterilizing effect was produced by air plasma and mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide gas. That is, similar sterilization results were obtained with plasmas generated in different gases. Therefore, it is considered that the bactericidal effect is caused by factors common to the two cases, and the factors are examined from the results common to the two cases in the gas analysis experiment.

Comparing the gas analysis results in the two cases 5 minutes after the generation of the discharge plasma shown in Fig. 24 (d) and Fig. 27 (d), the common points are that hydrogen, water, and monoxide replacement paper (rule ^> It is the generation of carbon. Here, comparison of carbon dioxide is difficult in the case of mixed gas plasma because carbon dioxide already exists. These gases are considered to be produced as a result of the oxidation reaction of carbon compounds by oxygen and the dissociation reaction of water vapor and carbon dioxide, as described in the respective gas analyses. On the other hand, the microorganisms to be disinfected and sterilized are organic substances (including carbon, hydrogen, oxygen, nitrogen, etc.), so it is considered that sterilization-sterilization is carried out by oxidation reaction with oxygen. Therefore, based on the results of gas analysis in the two cases, a common point that can lead to a bactericidal effect is that the oxidation reaction by oxygen is presumed to occur in the plasma.

 In air plasma, oxygen, which is a component of air, is chemically activated by plasma, and oxygen generated by dissociation of carbon dioxide is chemically activated by plasma in a mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide gas. This causes an oxidation reaction. As a result, it can be said that the same germicidal effect was obtained regardless of the gas generated by the plasma.

 Despite the fact that the mixed gas contains ethylene oxide gas, which has a germicidal effect, the only germicidal effect similar to that of the air plasma was obtained because the oxygen gas dissociated from carbon dioxide in the mixed gas plasma. This caused ethylene oxide to be decomposed. Generally, gas is converted into plasma to increase its chemical reactivity. However, since ethylene oxide gas is an unstable gas in the first place, it is not appropriate to directly increase its chemical reactivity by plasma conversion. This is one of the important results to keep in mind.

(3) Diffusion of ethylene oxide and air plasma in post-treatment step (3) after exhaust gas analysis was performed in air plasma post-treatment step (3). Then, it was examined how the ethylene oxide remaining in the apparatus is decomposed and detoxified in step (3), and why a sterilizing effect is generated in this step. a. Gas analysis experiment

 FIGS. 29 (a), (b), (c) and (d) show the transition of the results of gas mass spectrometry in the air plasma post-processing step 3. FIG. 29 (a) shows the mass spectrum of the gas species remaining in the analysis system. Figures 29 (b), (c) and (d) show the mass spectra immediately before, immediately after, and 5 minutes after discharge, respectively.

 Here, the biological indicator was inserted while the experimental apparatus was heated to about 45 ° C, and the gas in the apparatus was evacuated with a vacuum pump to reduce the pressure to 0.02 [Torr]. Ethylene oxide gas was injected up to an initial pressure of 7.6 [Torr], and was diffused and adsorbed in a sealed state for 20 minutes. Then, the gas in the apparatus was evacuated, and once reduced to 0.02 [Torr], air was introduced to a pressure of 0.25 [Torr]. The discharge current is 60 [mA] and the discharge voltage is 290 [V].

 According to Fig. 29 (b), peaks are observed at M / Z = 14, 15, 16, 18, 28, 29, 32, 40 and 44 in the gas mass spectrometry spectrum immediately before discharge. Here, referring to the table of FIG. 25 and the spectrum data of FIG. 28, the spectra of M / Z = 14 and 28 indicate nitrogen molecules, 32 indicates oxygen molecules, and 40 indicates argon. I understand. On the other hand, it can be seen that M / Z = 15, 16, 29 and 44 represent the spectrum of oxidized ethylene.

 Therefore, it can be seen that the gas components in the apparatus are the introduced air gas and the gas in which a part of the ethylene oxide adsorbed and remaining in the apparatus in the immediately preceding step 2 is vaporized.

According to Fig. 29 (c), in the gas mass spectrometry spectrum immediately after the generation of the discharge plasma, the hydrogen corresponding to M / Z = 2 suddenly increased in comparison with the result in Fig. 29 (b). Oxygen corresponding to the temperature becomes slightly smaller. Figure 29 (From Fig. 29, the M / Z = 2, 12, 14, 16, 17, 18, 26, 27, 28, 29, 40, and 44 in the mass spectrometry spectrum 5 minutes after the occurrence of discharge plasma. Compared to Fig. 29 (c), the peaks at M / Z = 2, 16, 18, 28 and 44 are larger and M / Z = 15 And the peaks at 32 and 32 disappear completely, M / Z = 12, 17, 26 and 27 appear, and the peaks at M / Z = 14 and 40 remain unchanged. Referring to the spectrum data in Fig. 25 and Fig. 28, the gas species is identified.The spectrum corresponding to M / Z = 2 is a hydrogen molecule, a part of M / Z = 17 and the spectrum of 18 Is steam, M / Z = 12, part of 14, part of 16, most of the increase of 28 and part of the spectrum of 29 are carbon monoxide, and M / Z = 12, It can be seen that some of the spectra, some of the 28 gains, and most of the 44 correspond to carbon dioxide. Here, the disappeared M / Z = 32 corresponds to an oxygen molecule, M / Z = 14 and 28 correspond to nitrogen molecules, and M / Z = 40 corresponds to argon.

 Consider the ethylene oxide component. In FIG. 29 (d), the peak at M / Z = 15 disappears, and the peak at M / Z = 29 becomes smaller and smaller. Here, the fragment spectrum of carbon monoxide overlaps with the peak at M / Z = 29, and the main spectrum of carbon dioxide overlaps with the peak at M / Z = 44. In the gas mass spectrometry spectrum of ethylene oxide in Fig. 28 (a), the spectrum component at M / Z = 15 is about 53% of the size of the main component, so Fig. 29 (d) The disappearance of the peak at M / Z = 15 is interpreted as indicating that the ethylene oxide has disappeared.

On the other hand, the spectra at M / Z = 26 and 27 in Fig. 29 (d) are shown in Fig. 27 (d) for the mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide in the previous section. As pointed out above, there is a possibility that it is ethane (C ₂ H ₆ = 30). Comparing the spectra of FIG. 29 (d) and FIG. 27 (d), the peak at M / Z = 27 and 26 is larger in FIG. 29 (d), and the peaks appear.

This is thought to be due to the difference in the amount of oxygen molecules present in both cases. In other words, it is presumed that the amount of oxygen molecules during plasma generation is smaller in the case of FIG. 29 (d) than in the case of FIG. 27 (d), and the oxidative decomposition of ethylene oxide does not proceed completely. You. The oxygen molecular partial pressure is divided into the following two cases And show the validity of this inference.

 (i) First, the amount of molecular oxygen in the case of a mixed gas plasma of 80% carbon dioxide and 20% ethylene oxide shown in Fig. 27 (d) is estimated. Although this mixed gas does not originally contain oxygen molecules, it obtains energy from plasma and generates oxygen molecules by the following two reactions.

C0 ₂ → (dissociation) C0 + (l / 2) 0 ₂ … (1)

C ₂ H ₄ 0+ (5/2) 0 ₂ → (oxidation) H ₂ 0 + 2C0 ₂

 Since the initial filling pressure of the mixed gas is 0.25 [Torr], the initial pressures of carbon dioxide and ethylene oxide gas are 0.2 [Torr] and 0.05 [Torr], respectively. Calculate the oxygen partial pressure required to completely oxidize ethylene oxide gas.

 Substituting the above equation (1) into the equation (2) and killing the oxygen molecules appearing on both sides (the carbon dioxide generated in the process of the above equation (2) is completely solved by the reaction of the above equation (1)) Is assumed to be separated),

C ₂ H ₄ 0+ (3/2) 0 ₂ → H ₂ 0 + 2C0… (3)

Becomes Therefore, in order to completely oxidize and decompose ethylene oxide gas with an initial partial pressure of 0.05 [Torr], it is understood that oxygen molecules with a partial pressure of 0.075 [Torr] must be generated. Now, assuming that all the carbon dioxide is dissociated by the above-mentioned reaction (1) by the plasma, the generated oxygen molecular partial pressure is 0.1 l [Torr], and the oxygenated titanium is completely oxidized. Larger than required for

(ii) Next, the amount of oxygen molecules in the case of the air plasma shown in FIG. 29 (d) is roughly estimated. Since oxygen accounts for 20% of the air, the partial pressure of oxygen molecules becomes 0.05 [Torr] at the initial filling pressure of 0.25 [Torr]. This partial pressure Calculating the total number of moles of oxygen molecules in the device, the 1.4X10- ⁵ mole.

However, the internal volume of the equipment was 5.5? And the temperature was 45 ° C. On the other hand, after air plasma, the replacement paper (Rule 2 I And approximately assumed 10mg extent oxidation Echiren amount remaining in the device before entering the step 3, a 2. 3 X 10- ⁴ mo le. Therefore, it can be said that the amount of oxygen molecules in the apparatus is not much larger than the amount necessary for completely oxidizing and decomposing the residual ethylene oxide.

 Here, the adsorption amount of ethylene oxide in Example 3 was estimated to be 11.6 mg. Before the depressurization step 3, the pressure in the apparatus is reduced and the part adsorbed in this process is expected to be desorbed. It is unknown what proportion of the adsorption amount will be the residual amount.

 b. Decomposition of residual ethylene oxide in process ③

 Based on the above experimental results, it is considered that the adsorbed and residual ethylene oxide is decomposed and made harmless in the discharge plasma for 5 minutes in the air plasma post-treatment process ③ in the following process.

1) Chemical activity of oxygen in air components due to energy ^s from plasma 0 ₂ → (excitation) 0 ₂ *… Generation of chemically active excited oxygen molecules

0 ₂ → (excitation) 0 + 0… Generation of chemically active oxygen atom

^# Bombarding electrons into the atmosphere gas having a temperature several tens of thousands of degrees that make up the plasma, refers to the this energy applied.

 2) Adsorption by chemically active oxygen · Oxidative decomposition of residual ethylene oxide · Gasification desorption

2C ₂ H ₄ 0+ 50 ₂ → (Occasion) 4C0 ₂ + 4H ₂ 0

C ₂ H ₄ 0 + 50 → (Occasion) 2C0 ₂ + 2H ₂ 0

 · · · Generation of carbon dioxide and water by oxidation reaction

3) Dissociation of carbon dioxide and water vapor by energy ^# from discharge plasma

Replacement form (Rules 2C0 ₂ → (dissociation) 2C0 + 0 ₂

 Generation of carbon monoxide and oxygen by dissociation of carbon dioxide

H ₂₀ (adsorbed water) → (desorption) H ₂₀ (water vapor) → (dissociation) 4H ₂ +0 ₂

 Generation of hydrogen and oxygen by dissociation of water vapor

 4) Undecomposition of ethylene oxide gas due to lack of oxygen

C ₂ H ₄ 0 + 2H ₂ → (reduced) C ₂ H ₆ + H ₂ 0… Reduction reaction generates ethane

 c. Consideration of sterilization process in process ③

 As described above in Experimental Example 4, a bactericidal effect was obtained with air plasma under the condition where residual ethylene oxide was present. The process is considered from the gas analysis results described above.

 The disinfection effect in the air plasma pretreatment process (1) and the mixed gas plasma of carbon dioxide and ethylene oxide was thought to be caused by the oxidation process of the material to be sterilized by oxygen chemically activated by the plasma. . However, it is considered that the sterilization effect in the air plasma post-treatment process ③ is brought about in a different process. Because, assuming that it is due to chemically activated oxygen as in air plasma pretreatment step (2), the processing time in step (3) is 5 minutes, so too short A bactericidal effect will be achieved over time. Moreover, in the process (2), the sterilization effect of the air plasma is already saturated.

 The important point in the air plasma post-treatment process ③ is inside the equipment (substance to be sterilized)

Replacement paper (Fine I 6) Air plasma is generated under the condition that adsorbed ethylene oxide remains in every corner of the area.

 It is conceivable that oxygen in the air chemically activated by the plasma acts on the adsorbed oxidized titanium and indirectly participates in the sterilization process.

 As shown in Fig. 29 (d), the disappearance (consumption) of oxygen components in the air and the desorption / decomposition of adsorbed oxidized titanium are observed. The results of this experiment indicate that the adsorbed ethylene oxide is affected by chemically activated oxygen.

Here, the sterilization process using the conventional method of diffusing high-concentration ethylene oxide gas for a long time is rewritten as follows. The thermal energy of about 50 ° C causes the oxygen oxide of some ethylene oxide gas ((CH ₂ ) ₂₀ ) The bond between carbon and carbon is cleaved, and the chemically activated ethylene oxide gas reacts (alkylates) with the material to be sterilized. As a result, sterilization and sterilization are performed.

 Since ethylene oxide gas can be activated with heat energy of about 50 ° C, chemically activated oxygen (this oxygen can generate more than 10,000 degrees of high energy by air plasma) ) Can be easily activated adsorbed oxidized titanium.

 In other words, most of the ethylene oxide adsorbed near the object to be sterilized receives the activation energy necessary to react with the object to be sterilized from chemically activated oxygen and reacts with the object to be sterilized. is there. Moreover, since this reaction occurs efficiently, an effective sterilizing effect is expected to appear in a short time even with a small amount of residual ethylene oxide.

Subsequent to or simultaneously with this process, a process of oxidative decomposition of ethylene oxide and residual ethylene oxide after reaction with chemically activated oxygen occurs. However, at this time, as shown in Fig. 29 (d), if the initial partial pressure of oxygen molecules is too low, the residual ethylene oxide is completely decomposed into water and carbon dioxide. It is not converted to some etanes. Industrial applicability

 As described above, according to the present invention, the use of spatially uniform plasma generated by multi-phase AC discharge and low-concentration ethylene oxide gas reduces sterilization unevenness and increases the speed of sterilization. In addition, ethylene oxide gas sterilization with low persistence can be realized.

 Compared to conventional ethylene oxide gas sterilization, ethylene oxide concentration is 1/50 or less, and sterilization time is 1/10 or less, including sterilization and residual processing time. The overall performance improvement ratio is more than 500 times. Hydrogen peroxide plasma sterilization is one of the plasma sterilization processes that have been put into practical use, but it has a drawback in that it cannot sterilize water-absorbing celluloses and has a problem in permeability. In the present invention, it is possible to use the same as those to which the conventional sterilization treatment using ethylene oxide gas with good permeability can be applied, and the applicable range is wide.

 Furthermore, the same effect can be realized even when using formaldehyde gas.

 In the gas sterilizer used in the present invention, first, chemically active oxygen is generated uniformly spatially by the spatially uniform plasma generated by the multi-phase AC discharge. By causing it to reach the surface of the object to be sterilized, the chemical reactivity of the surface of the object to be sterilized is increased, and spatially unbiased gas sterilization by injecting sterilizing gas is performed.

Connect each phase component of the polyphase AC power supply to the split electrode mounted along the inner wall of the equipment, and connect the neutral point of the polyphase AC power supply to the metal mesh basket installed at the center of the equipment that stores the object to be sterilized I do. Discharge occurs between the divided electrodes of each phase and the mesh cage, and goes around between the electrodes during one cycle of the power supply frequency. As a result, the plasma resulting from the discharge is radiated inward to the metal mesh. Spreads into the baskets. A spatially almost uniform plasma will exist around the object to be sterilized stored in the metal mesh basket.

 Chemically active oxygen is generated evenly around the object to be sterilized in the plasma, and reaches the surface of the object to be sterilized after passing through the sterilization pack surrounding the object to be sterilized. The chemically reactive oxygen enhances the chemical reactivity of the surface of the object to be sterilized evenly in space, and as a result, spatially uniform gas sterilization by injecting sterilizing gas is performed.

Claims

The scope of the claims

1. A pretreatment step in which a gas containing an oxygen element is supplied to a sterilization chamber under low pressure containing a material to be sterilized 1 P to generate plasma,

 A sterilization step of supplying a sterilization gas to a sterilization chamber under low pressure,

 A post-treatment step of supplying a gas containing oxygen element again to the sterilization chamber under low pressure to generate plasma,

 Gas sterilization method, wherein the sterilization is performed sequentially in this order.

2. The pretreatment step

 Exhausting the sterilization chamber;

 Supplying a gas containing an oxygen element to the evacuated sterilization chamber to maintain the pressure at a low pressure; and generating plasma in the sterilization chamber under the low pressure to activate oxygen in the gas;

 A step of gasifying and cleaning the deposit on the surface of the object to be sterilized by the activated oxygen;

 Exhausting a gas containing the oxygen element,

2. The gas sterilization method according to claim 1, wherein the gas sterilization method comprises:

 3. The sterilization step

 Supplying sterilized gas to the evacuated low-pressure sterilization chamber to contact the object to be sterilized;

 After a predetermined time, sterilization

2. The gas sterilization method according to claim 1, wherein the gas sterilization method comprises:

 4. The sterilization step

 Supplying sterilizing gas to the evacuated low-pressure sterilization chamber, and then introducing air at atmospheric pressure to contact the sterilizing gas with the object to be sterilized;

Exhausting the sterilizing gas after a predetermined time; 2. The gas sterilization method according to claim 1, wherein the gas sterilization method comprises:

5. The post-treatment step

 Supplying a gas containing an oxygen element to the evacuated sterilization chamber to maintain the pressure at a low pressure; and generating plasma in the sterilization chamber under the low pressure to activate oxygen in the gas;

 A step of gasifying and removing residues adhering to the material to be sterilized by the activated oxygen;

 Exhausting a gas containing the oxygen element,

2. The gas sterilization method according to claim 1, wherein the gas sterilization method comprises:

6. The gas sterilization method according to claim 2, wherein in the pretreatment step, the inside of the sterilization chamber is heated during exhaustion in the sterilization chamber.

 7. The gas sterilization method according to claim 3, wherein the sterilization chamber is heated during the sterilization gas contact in the sterilization step.

 8. The gas sterilization method according to claim 1, 2, or 5, wherein the gas containing the oxygen element is air.

 9. The gas sterilization method according to claim 1, wherein the gas containing the oxygen element is oxygen.

 10. The gas sterilization method according to claim 1, 2, or 5, wherein the gas containing the oxygen element is carbon dioxide.

 11. The gas sterilization method according to claim 1, wherein the sterilization gas is ethylene oxide gas.

 12. The gas sterilization method according to claim 1, wherein the sterilizing gas is formaldehyde.

13. The claim 1 or 2 wherein the pressure of the gas containing the oxygen element supplied to the sterilization chamber is 0.1 l Torr (1/7600 atm) to 1 Torr (1/760 atm). Or the gas sterilization method described in 5.

4. The gas sterilization method according to claim 1, wherein the pressure of the sterilization gas supplied to the sterilization chamber is lTorr (l / 760 atm) to lOTorr (1/76 atm).

 1 5. The gas sterilization method according to claim 6, wherein a temperature at which the inside of the sterilization chamber is heated is 40 to 60 ° C.

 1 6. Connect the source of sterilizing gas and the source of gas containing oxygen element to the sterilization chamber made of a vacuum vessel, and fix the multiple divided electrodes closely along the inner wall of the sterilization chamber via the insulating layer. A gas sterilizer that connects each phase component of a phase-controlled multi-output AC power supply to each split electrode to generate spatially uniform plasma in the sterilization chamber.

 1 7. Install a metal mesh basket in which the object to be sterilized is to be stored inside the sterilization chamber, and connect the neutral point of the phase control multi-output AC power supply to this mesh basket. 17. The gas sterilizer according to claim 16, wherein a spatially uniform plasma is generated in the gas sterilizer.