JPH08126686A - Sterilization - Google Patents

Abstract

PURPOSE: To sterilize a packing material or the like safely, handily and efficiently by a method wherein a gas is passed through an electric field to ionize at least a part thereof and the gas thus obtained is mixed with a mixture of a gas and a liquid to keep the mixture obtained in contact with an object to be sterilized outside the electric field. CONSTITUTION: A gas for ionization (gas for excitation) is supplied via an introduction pipe 5 from a supply source 11 to a space between a high voltage electrode 15 and a ground electrode 3 where an electric field is generated. At least a part of the gas is ionized when passing between the high voltage electrode 15 and the ground electrode 3. The gas partially ionized is mixed with a mixture of a gas and a liquid obtained as misty matter, where the latter gas is produced by passing a gas through a bubbling container 13 with a nebulizer 10 being introduced from an introduction tube 16. The mixture thus obtained moves toward an object 8 to be sterilized and discharged from an exhaust pipe 9 after the sterilization of the object to be sterilized 8. The object 8 to be sterilized is arranged in a separate chamber from a housing 4 and the gas obtained in the housing 4 can be introduced into the separate chamber housing the object 8 to be sterilized for its sterilization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a sterilization method. More specifically, the present invention relates to a sterilization method capable of safely, simply and efficiently sterilizing packaging materials, medical materials, containers and the like.

[0002]

2. Description of the Related Art As a sterilizing method for articles, there are known a method of using a sterilizing agent such as ethylene oxide gas, a method of irradiating radiation rays such as gamma rays and electron beams, and a method of using glow discharge under low pressure. .

In the sterilization method using a disinfectant such as ethylene oxide gas, the disinfectant such as ethylene oxide gas used often has toxicity. Therefore, the treatment must be performed in a closed system, and the treatment apparatus itself becomes large. Further, there is a possibility that the disinfectant remains on the object to be disinfected.

In the method of irradiating radiation such as gamma rays and electron rays, there is no fear that the germicide remains. However, there is a problem that the mechanical strength of the sterilized article is lowered, and when the article is a resin, the resin is decomposed and a bad odor is attached to the article or discolored (Japanese Patent Publication No. 3-73309). See the bulletin).

The sterilization method by glow discharge needs to be performed under vacuum in order to cause glow discharge. Therefore, there are problems in equipment, cost, workability, productivity, and the like.

A method using plasma is known as a sterilization method capable of solving the problems of these conventional techniques [Japanese Patent Laid-Open No. 5-229530]. This method, for example, irradiates an energy converter made of a composite oxide with electromagnetic waves,
The excited energy converter and the rare gas or the like are brought into contact with each other to form a plasma state, and the rare gas or the like in the plasma state is brought into contact with the object to be sterilized.

[0007]

The above-mentioned method using plasma can safely and easily sterilize articles such as packaging materials,
Moreover, it is an excellent method because it is less likely to deteriorate the sterilized article. The present inventor has conducted further studies in order to put this method into practical use. As a result, in order to process a large amount of articles at one time, it is necessary to obtain a large amount of gas in the plasma state, and for that reason, the energy converter for bringing into the plasma state is enlarged, and electromagnetic waves of higher output are generated. Was needed. However, practically, it is difficult to counter the conventional method with a large-sized device. Furthermore, in the case where the sterilized object has a thick structure, it may not be able to sterilize sufficiently to the inside, or if it is brought close to the energy converter in order to increase the sterilizing power, the temperature of the sterilized object may rise and the quality may change. I also understood.

Therefore, an object of the present invention is to provide a sterilization method that is safe and easy to sterilize articles such as packaging materials, and that does not deteriorate the sterilized articles, and that requires a smaller device, that is, more efficient. It is to provide a method that can sterilize well and strongly.

[0009]

According to the present invention, at least a part of a gas is passed through an electric field to be ionized, and the obtained at least a part of the ionized gas is mixed with a mixture of a gas and a liquid. The present invention relates to a sterilization method, which comprises contacting an object to be sterilized with outside of an electric field. The present invention will be described in detail below.

In the method of the present invention, first, at least part of the gas is ionized by passing the gas through an electric field. The electric field can be generated, for example, by using at least one pair of high-voltage electrode and ground electrode and applying a voltage of a certain level or more between the electrodes. In such an electric field generator, for example, a high voltage electrode and a ground electrode used for corona discharge or the like can be used as they are, and at least one surface of the high voltage electrode and the ground electrode is covered with a solid dielectric. It is a thing. The solid dielectric is not particularly limited, but for example, a ceramic such as quartz, a hypalon rubber, a laminated body of polyester such as polyethylene terephthalate, or the like can be used.

The numbers and shapes of the high voltage electrodes and the ground electrodes are not particularly limited, and can be appropriately determined depending on how much the gas passing through the generated electric field needs to be ionized. For example, when the flow rate of gas is high, it is possible to adjust the stay time in the electric field to be long for the purpose of ionizing at a certain rate or more. In such a case, a plurality of high voltage electrodes and ground electrodes are arranged in parallel. It is also possible to provide them, or at least one of the high-voltage electrode and the ground electrode may have a band 9 shape.

The voltage supplied between the high voltage electrode and the ground electrode is preferably an alternating voltage having a frequency in the range of 50 to 1,000 kHz. The frequency of the AC voltage can be determined in consideration of the distance between the electrodes, the dielectric material, and the like. The preferred frequency is in the range 1-100 kHz. Furthermore, the voltage between the high-voltage electrode and the ground electrode can be appropriately determined in consideration of the type and flow rate of the gas to be used or the mixture of gas and liquid, the distance between the electrodes, and the like, for example, 2000-2.
It is suitable to set it in the range of 10,000V. The preferred voltage is in the range of 4000-8000V.

In the present invention, the gas that passes the electric field is
It is a gas that can be ionized in an electric field. Examples of such a gas include oxygen, nitrogen, rare gases (argon, helium, and neon), hydrogen, air, and the like. Among rare gases, argon is preferable because it is easily ionized and is excellent in cost. Further, helium is preferable from the viewpoint that ionization tends to be continuous. In particular, argon has a specific gravity closer to that of air than helium and is easy to handle under atmospheric pressure, so that it can be used more preferably. Further, two or more kinds of the above gases can be mixed and used together.

Further, a minute amount of a ketone compound such as acetone can be added to argon or a mixture of argon and helium among the above gases. Glow discharge is easily generated by adding a small amount of a ketone compound.
The amount of the ketone compound added is 0.1: 99.9 to 9 in terms of the volume ratio of argon or a mixed gas of argon and helium.
It is appropriate that the range is 0:10 (ketone compound: argon or a mixed gas of argon and helium). Further, it is appropriate that the volume ratio (argon: helium) in the mixed gas of argon and helium is in the range of 100: 0 to 10:90. The addition of the ketone compound is
It can be carried out by passing argon or the like through a washing bottle or the like filled with a ketone compound. Further, it is also possible to heat the washing bottle or the like to vaporize the ketone compound and add it to argon or a mixture of argon and helium.

At least a part of the gas passing through the electric field needs to be ionized. Therefore, the gas flow rate, the amount of voltage and current (power) applied to generate an electric field, the number and shape of electrodes, etc. are appropriately determined so that at least a part of the gas can be ionized.

In the present invention, a gas which is at least partially ionized through an electric field (hereinafter referred to as an excited gas) is mixed with a "mixture of gas and liquid". Here, the gas of the “mixture of gas and liquid” can be the same as the gas that can be ionized in the electric field. Further, the liquid can be, for example, water, hydrogen peroxide or hydrogen peroxide solution, ethanol, a mixture of ethanol and water, or the like. When using hydrogen peroxide water, the concentration of hydrogen peroxide is
From the viewpoint of being commercially available and easily available, it is suitable that the hydrogen peroxide concentration is, for example, 50% or less, preferably 35% or less. When the concentration is lower than that, commercially available hydrogen peroxide solution may be diluted with water to appropriately adjust the concentration in consideration of sterilization conditions and the like. However, considering the bactericidal effect, it is preferable to use 1% or more hydrogen peroxide solution.

The liquid is preferably in the form of a mist,
The atomized liquid can be generated by passing the gas as a carrier gas through a nebulizer connected to a liquid supply source. The atomized gas can also be generated by bubbling a carrier gas through them. The ratio of the gas as the carrier gas and the liquid in the "mixture of gas and liquid" is not particularly limited, but the range of 1 mg to 100 mg per liter of gas is considered to be the pressure to be sterilized. Appropriate. Furthermore, the particle size of the mist is, for example, about 50 to
The range of 3000 μm is preferable from the viewpoint of preventing local discharge.

The excitation gas and the "mixture of gas and liquid" can be mixed outside the electric field or near the exit of the electric field by the gas to be ionized. Only the gas is supplied into the electric field, and the "mixture of gas and liquid" is performed after the excitation gas substantially passes through the electric field, thereby covering the surface of the high-voltage electrode among the electrodes for generating the electric field. There is an advantage that damage to the solid dielectric can be prevented. When a liquid aggregate introduced as a mist adheres to the solid dielectric covering the surface of the high voltage electrode,
Discharge may concentrate on that portion and damage the solid dielectric.

Further, in the method of the present invention, when a plurality of electrode pairs are arranged in series in the flow direction of the exciting gas, the "mixture of gas and liquid" can be introduced in the middle of the exciting gas in the electric field. . By introducing in the middle, it is possible to prevent damage to the solid dielectric in the high voltage electrode upstream of the introducing portion. Mixing the excited gas with the "mixture of gas and liquid"
This can be done by merging the flow of the "gas and liquid" with the flow of the excitation gas. The mixing ratio of the exciting gas and the “mixture of gas and liquid” is 0.1 to 10 parts by volume of the “mixture of gas and liquid” when the flow rate of the exciting gas per unit time is 1 part by volume. It is appropriate to set the range.

The mixture of excitation gas and "mixture of gas and liquid" is then brought into contact with the material to be sterilized. The contact method is not particularly limited. However, it is also possible to bring the gas stream of the mixture into contact with the fixed substance to be sterilized or to introduce the substance to be sterilized into a container filled with the mixture. In particular, it is preferable that the inside of the chamber in which the substance to be sterilized is installed is usually near atmospheric pressure because the operation is easy. However, it is possible to enhance the sterilization effect by operating the sterilization container so that the inside of the sterilization container is slightly pressurized (atmospheric pressure up to 1 atm from atmospheric pressure). It is preferable from the viewpoint that the inside of the body can be sterilized.
In addition, it is possible to maintain a sterile condition in the chamber by setting the positive pressure in the chamber.

The sterilization method of the present invention can be carried out, for example, by the apparatus shown in FIG. In the figure, 1 is a quartz-coated electrode, 2 is a metal electrode, and 1 and 2 are high-voltage electrodes 15.
Is configured. Reference numeral 3 is a metal electrode, which constitutes a ground electrode. Reference numeral 4 is a housing, 5 is an exciting gas introduction pipe, 6 is a high-pressure bushing (insert made of a high-voltage insulating material), 7 is a high-voltage power supply, 8 is an object to be sterilized, 9 is an exhaust pipe, 10 is a nebulizer, 11 is a gas. A supply source, 12 is a supply source of a liquid (for example, hydrogen peroxide solution), 13 is a bubbling container filled with a liquid, 14 is an ionized gas, and 16 is a nebulizer 10.
Alternatively, it is an introduction pipe for a mixture of a gas and a liquid generated in the bubbling container 13.

The gas for ionization (excitation gas) is supplied from the supply source 11
High voltage electrode 15 from which the electric field is generated through the introduction tube 5
And the ground electrode 3. At least a part of the gas passing between the high-voltage electrode 15 and the ground electrode 3 is ionized. The gas, which is at least partially ionized in the electric field between the high-voltage electrode 15 and the ground electrode 3, passes through the nebulizer 10 or the bubbling container 13 introduced from the introduction pipe 16 and is obtained as a mist. Mixed with. The obtained mixture moves toward the sterilized object 8, sterilizes the sterilized object, and then is exhausted from the exhaust pipe 9.

The apparatus shown in FIG. 1 is one embodiment for carrying out the method of the present invention. For example, the body to be sterilized 8 is arranged in a room separate from the housing 4, and the gas obtained in the housing is sterilized. The body 8 can be introduced into a separate room for sterilization. Further, the scale of the housing can be appropriately changed in consideration of the flow rate of gas, the residence time thereof, and the like.

The substance to be sterilized is not particularly limited, but for example,
Examples include an article made of various types of plastics alone, a plurality of these plastics laminated, or a laminated material obtained by laminating these plastics and a metal foil. Moreover, the form of these articles can be a sheet or roll of packaging for food or medicine, or a container tray, a bottle, or the like. Further, examples of the sterilization object include woven or non-woven fabric made of natural fibers or synthetic resin fibers, and paper or clothes made of the above fibers. In particular, the method of the present invention is effective for sterilizing thick articles such as gauze, masks and cotton.

When the substance to be sterilized is a packaging material, its form is, for example, a bag, a self-standing bag, a molded container, a molded sheet,
It can be a bottle or the like. The method of the present invention comprises a food,
Require sterility of chemicals, etc.
It has a wide application range to fields requiring sanitary sterility.

There is no particular limitation on the bacteria that can be sterilized. According to the method of the present invention, for example, E. coli,
Salmonella typhi, B. subtilis, Staphylococcus aureus (Stap)
hylococcus. aureus), Aspergillus niger (Asp. niger) and the like can be sterilized.

[0027]

EXAMPLES The present invention will be further described below with reference to examples. Examples 1 to 7 The sterilization method of the present invention was carried out under atmospheric pressure using the apparatus shown in FIG. The size of the metal electrode 3, which is the ground electrode, is 16 mmφ × 50 mm, and the high voltage electrode 1 coated with quartz is used.
The size of 5 is 19 mmφ × 150 mm. Table 1 shows the experimental conditions of voltage, output, frequency, type and flow rate of gas for ionization, type and flow rate of gas and liquid for mixture of gas and liquid, treatment time, and type of object to be sterilized. A nebulizer was used to generate the mist, and the distance between the sterilized object and the electrode was 10
cm. Further, in Example 4, acetone was added by bubbling the ionizing gas into a cleaning bottle filled with acetone. The flow rate of acetone was indicated by the amount of acetone as a liquid.

Two types of test pieces were used as the sterilized objects. Test piece A is made of sterile polyester tape and Bacillus subti.
Lis) spores (endspores) were attached so that 10 ⁶ pieces per piece (spore diameter 5 mm
φ). As the test piece B, Tesper G (trade name, manufactured by Eiken Kikai Co., Ltd.) (for sterilization effect measurement for OG sterilization dry heat) was used.

Evaluation method (inspection of the number of remaining spores) The test piece A used in the sterilization test was sterilized to 0.2%.
1 in 10 ml of Tween 80 saline
After immersion for a period of time, the mixture was stirred to extract residual spores. The residual spores of the test piece B were extracted with a physiological saline amount of 50 ml. The obtained residual spore extract was cultured at 35 ° C. for 48 hours using a standard agar medium. After culturing, the remaining spores per piece were calculated from the number of colonies that appeared. The results are shown in Table 1. In Table 1, the number of residual spores of control was 4.2 × 10 ⁶ (number of spores / piece),
The sterilization number was expressed as -log (number of treated spores / number of control spores).

[0030]

[Table 1]

[0031]

According to the present invention, JP-A-5-22953
Similar to the sterilization method using plasma described in No. 0, articles such as packaging materials can be safely and easily sterilized, and the sterilized articles are less likely to deteriorate. That is, it is possible to provide a method capable of performing sterilization more efficiently and strongly.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sterilizer used in an example of the present invention.

[Explanation of symbols]

 1 ... Quartz-covered electrode 2 ... Metal electrode 3 ... Metal electrode (ground electrode) 4 ... Housing 5 ... Gas introduction tube 6 ... High-voltage bushing 7 ... High-voltage power supply 8.・ ・ Sterilizer 9 ・ ・ ・ Exhaust pipe 10 ・ ・ Nebulizer 11 ・ ・ Gas supply source 12 ・ ・ Liquid (for example, hydrogen peroxide solution) supply source 13 ・ ・ Bubbling container 14 ・ ・ Ionized gas 15 ..High-voltage electrode 16..Introduction tube for mixture of gas and liquid

Claims (7)

[Claims] 1. A gas is passed through an electric field to ionize at least a part of the gas, and the obtained gas, at least a part of which is ionized, is mixed with a mixture of a gas and a liquid, and the obtained mixture and a substance to be sterilized are separated from the electric field. A sterilization method comprising contacting with. 2. The sterilization method according to claim 1, wherein the gas passed through the electric field is at least one selected from the group consisting of oxygen, nitrogen, argon, helium and neon. 3. The gas constituting the mixture of gas and liquid is the gas according to claim 2, and the liquid is water, hydrogen peroxide, hydrogen peroxide solution, ethanol, or a mixture of ethanol and water. Item 1. The sterilization method according to Item 1. 4. The sterilization method according to claim 1, wherein the liquid is in a mist state. 5. The gas passing through the electric field is argon or helium containing a ketone compound.
The sterilization method according to any one of 1. 6. An electric field is generated between at least one pair of a high voltage electrode and a ground electrode, and the surface of at least one of the high voltage electrode and the ground electrode is covered with a solid dielectric. The sterilization method according to any one of 5 above. 7. Between the high voltage electrode and the ground electrode, 50 Hz
7. The method according to any one of claims 1 to 6, wherein an alternating current in the range of ~ 1,000 kHz is supplied.