JPH08168516A - Sterilization method - Google Patents

Abstract

(57) [Summary] [Purpose] This is a sterilization method that is safe and easy to sterilize articles such as packaging materials, and that does not deteriorate the sterilized articles efficiently, even with a smaller device. Providing a method for sterilization. A sterilization method in which a mixture of a gas and a liquid at least a portion of which is ionized by an electric field is brought into contact with an object to be sterilized, and the electric field is generated by a pulsed electric field.

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.

[0006]

A method using plasma is known as a sterilization method capable of solving the problems of these conventional techniques [JP-A-5-229530]. This method is, for example, irradiating an energy converter made of a complex oxide with electromagnetic waves, bringing the excited energy converter and a rare gas or the like into a plasma state, and contacting the plasma-containing rare gas or the like with an object to be sterilized It is what makes me.

The above-mentioned method using plasma is an excellent method since it is safe and easy to sterilize articles such as packaging materials, and the quality of the sterilized articles is small. 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 once, it is necessary to obtain a large amount of gas in a plasma state,
For that purpose, the energy converter for making a plasma state was enlarged, and the electromagnetic wave of large output was required. 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.

In addition to the above method, a sterilization method using ozone is well known. Above all, a method using a pulse power source has been proposed in order to efficiently generate ozone. For example, a sterilization method by pulse discharge [JP-A-63-3189]
47] or a method using a pulse voltage for the purpose of generating ozone by corona discharge [JP-A-1-153504]
Is mentioned. Both methods use oxygen as ozone by electric discharge, but sterilization by ozone is not so strong against Bacillus subtilis, and it is desired to provide a more powerful sterilization method.

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. It is to provide a method that can sterilize well and strongly.

[0010]

SUMMARY OF THE INVENTION The present invention is a sterilization method in which a mixture of a gas and a liquid at least a portion of which is ionized by an electric field is brought into contact with a substance to be sterilized, and the electric field is generated by a pulse voltage. The present invention relates to a sterilization method characterized by the above. The present invention will be described in detail below.

The sterilization method of the present invention is characterized in that sterilization is performed by using a pulse voltage for generating an electric field and a mixture of a gas and a liquid at least a part of which is ionized.

In the present invention, the rising speed of the pulse voltage is 0.01 kV / ns to 10 kV / ns in all cases.
It is suitable to be in the range. When the rising speed of the pulse voltage is less than 0.01 kV / ns, the bactericidal effect tends to decrease. The rising speed of the pulse voltage is 10k
Exceeding V / ns does not adversely affect the bactericidal effect, but makes voltage generation difficult. The preferable range of the rising speed of the pulse voltage is 0.1 kV / ns to 1 kV / ns.

In the method of the present invention, the pulse width of the pulse voltage is preferably in the range of 10 ^-9 seconds to 10 ^-1 seconds. The pulse width does not have a great effect on the bactericidal effect,
The pulse width that can be oscillated is within the above range. A preferred range of pulse width is 10 ^-8 seconds to 10 ^-6 seconds.

The peak voltage of the pulse voltage is 1 kVp to 10
It is suitable to be in the range of 0 kVp. When the peak voltage is less than 1 kVp, the electric field strength is small and the peak voltage is 1
If it exceeds 00 kVp, there is a problem that the device needs to be upsized. The preferred range of peak voltage is 8 to 50
kVp.

The frequency of the pulse voltage is 1 Hz to 100 kHz
Suitably it is in the range of z. If the frequency is less than 1 Hz, the sterilization efficiency is lowered, and if it exceeds 100 kHz, the temperature of the gas in the electric field is significantly increased. The preferable range of the frequency of the pulse voltage is in the range of 50 Hz to 500 Hz.

In the method of the present invention, at least a part of the mixture of gas and liquid is ionized by using the above pulse power source, and the resulting ionized mixture is sterilized. The ionization method includes a method of passing at least a part of the mixture by passing a mixture of gas and liquid in an electric field (first method).
And a method of mixing at least a portion of a gas obtained by passing a gas through an electric field and ionizing the mixture and a mixture of the gas and the liquid outside the electric field to obtain a mixture of a gas and a liquid at least a portion of which is ionized (second Method).

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. Such an electric field generator can use the high-voltage electrode and the ground electrode used for corona discharge or the like as they are, for example,
The surface of at least one of the high voltage electrode and the ground electrode may be covered with a solid dielectric.
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. Further, both the high voltage electrode and the ground electrode may be metal electrodes.

The number and shape of the high voltage electrode and the ground electrode are not particularly limited, and can be appropriately determined depending on how much the gas or the mixture of the gas and the liquid passing through the generated electric field needs to be ionized. . For example, when the flow rate of a gas or a mixture of a gas and a liquid is high, it is possible to adjust the residence time in the electric field to be long for the purpose of ionizing at a certain rate or more. A plurality of ground electrodes may be provided in parallel, or at least one of the high voltage electrode and the ground electrode may have a strip shape. Further, in order to prevent local discharge, in order to increase the surface area of the high voltage electrode, the electrode may be provided with protrusions or irregularities.

In the first method of obtaining the ionized body of the mixture of gas and liquid in the present invention, the gas of the "mixture of gas and liquid" which is passed through the electric field is a gas which can be ionized in the electric field. As such a gas, for example, oxygen,
Nitrogen, noble gases (argon, helium and neon), hydrogen, air and the like can be mentioned. 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.

The liquid is, for example, water, hydrogen peroxide,
It can be hydrogen peroxide water, ethanol, a mixture of ethanol and water and the like. When hydrogen peroxide water is used, it is suitable that the concentration of hydrogen peroxide is, for example, 50% or less from the viewpoint of being commercially available and easily available. 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. Also, "a mixture of gas and liquid"
Can also be prepared by using a part of the gas as a carrier gas and mixing the atomized substance obtained by the gas and the carrier gas with the rest of the gas. The ratio of the gas (all gases including the carrier gas) and the liquid is not particularly limited, but the range of 1 mg to 100 mg per liter of gas is considered to be the discharge continuation and the pressure on the sterilized object. Appropriate. Further, the particle size of the atomized material is preferably in the range of, for example, about 5 to 3000 μm from the viewpoint of preventing local discharge.

In the second method of obtaining the ionized body of the mixture of gas and liquid in the present invention, the gas passing through the electric field is a gas ionizable in the electric field. Such a gas can be appropriately selected from the gases that can be used for the “mixture of gas and liquid”. In the second method, a gas that is at least partially ionized and a mixture of a gas and a liquid are mixed to obtain a mixture of a gas and a liquid that is at least partially ionized. The mixing ratio of the gas at least a part of which is ionized and the mixture of the gas and the liquid can be appropriately determined depending on the desired degree of sterilization.

At least a part of the gas or the mixture of the gas and the liquid which is passed through the electric field needs to be ionized. Therefore, at least a part of the gas or the mixture of the gas and the liquid can be ionized, such as the flow rate of the gas or the mixture of the gas and the liquid, the amount of voltage and current (electric power) applied to generate the electric field, the number and shape of the electrodes, and the like. As appropriate. Further, it is preferable that the gas pressure is usually around atmospheric pressure because the operation is easy. However, as described later, 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). It is preferable from the viewpoint that it is possible to sterilize the inside of a thick body to be sterilized.

The at least partially ionized gas / liquid mixture obtained by the first or second method is brought into contact with the substance to be sterilized. The contact with the substance to be sterilized can be performed inside or outside the electric field in the first method, and outside the electric field in the second method. The contact method is not particularly limited. However, it is also possible to bring the gas stream of the ionized mixture into contact with the fixed substance to be sterilized (inside or outside the electric field) or to introduce the substance to be sterilized into the container filled with the ionized mixture (outside the electric field). In particular, it is possible to enhance the sterilizing effect by operating the inside of the chamber in which the object to be sterilized is set so that the pressure is slightly higher than atmospheric pressure (up to 1 atm from atmospheric pressure), as described above. It is preferable from the viewpoint that it is possible to sterilize the inside of a thick body to 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. FIG. 1 is a cross-sectional explanatory view. In the figure, 1 is a quartz-coated electrode, 2 is a metal electrode, and 1 and 2 form a cylindrical ground electrode 3. Reference numeral 4 is a rod-shaped metal electrode, which constitutes a high-voltage electrode. Reference numeral 5 is an introduction pipe (pipe A) of a gas or a mixture of gas and liquid, 6 is an introduction pipe of a mixture of gas and liquid (pipe B), 7 is an object to be sterilized, 8
Is an exhaust pipe. Although not shown, the pipe A communicates with a gas supply source via a nebulizer filled with a liquid such as hydrogen peroxide, or directly. In addition, the pipe B is
Although not shown, the gas supply source is communicated with a nebulizer filled with a liquid such as hydrogen peroxide.

In the first method of directly ionizing a mixture of gas and liquid, a nebulized mixture obtained by passing the gas through a nebulizer filled with a liquid such as hydrogen peroxide is supplied from a pipe A into an electric field. . Ground electrode 3 and high voltage electrode 4
At least a part of the gas passing through the space is ionized, the gas moves toward the sterilized object 7, sterilizes the sterilized object, and then is exhausted from the exhaust pipe 8. A second step of ionizing the gas and then mixing the ionized gas with a mixture of the gas and the liquid
In the above method, the gas for ionization is introduced from the pipe A, and from the vapor B, the atomized mixture obtained by passing the gas through a nebulizer filled with a liquid such as hydrogen peroxide is introduced. At least a part of the gas passing between the ground electrode 3 and the high-voltage electrode 4 is ionized, the ionized gas is mixed with the mist-like mixture supplied from the pipe B, and further moved to the sterilized object 7. Then, after sterilizing the sterilized object, it is exhausted from the exhaust pipe 8.

The apparatus shown in FIG. 1 is one embodiment for carrying out the method of the present invention. For example, the object to be sterilized 7 is placed in a room separate from the ionization space, and the gas obtained in the ionization space is sterilized. The body 7 can be introduced into a separate room for sterilization. Further, the scale of the chamber 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.
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. Other examples of the sterilized product include metals and processed products (for example, injection needles) containing metal, ceramics, glass, and processed products thereof.

When the material 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 is a food,
Requires sterility of medicines, for example, in the field of aseptic,
It has a wide range of applications to fields requiring hygienic 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.

[0031]

EXAMPLES The present invention will be further described below with reference to examples. Examples 1 to 8 The sterilization method of the present invention was carried out under atmospheric pressure using the apparatus shown in FIG. However, a high voltage square wave pulse generator (peak voltage 16.4 kV, waveform: square wave, frequency: 240 Hz to 238.5 Hz) was used as a power source, and a nebulizer was used to mix the gas and the liquid, and the gas from the pipe A was used. And a mixture of liquid was fed into the electric field. The liquid supply rate was 2.5 g / hr. Experimental conditions such as gas type and flow rate, liquid type and concentration, processing time, sterilized object (specimen)
Table 1 shows the types and the number of remaining bacteria. The distance between the object to be sterilized and the electrode was 8 cm.

Two kinds 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 measuring sterilization effect of EOG / dry heat sterilization) 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 the control is 4.2 × 10 ⁶ (number of spores / piece).

Comparative Examples 1 to 14 As a power source, a power source having a commercial frequency of 50 Hz (two neo transformers (for neon signs) connected in series, voltage 15.6)
Sterilization was performed in the same manner as in Examples 1 to 8 except that a kV) (Comparative Examples 1 to 7) and a 10 kHz high frequency transformer (voltage 8 kV (sine waveform)) (Comparative Examples 8 to 14) were used. Table 1 shows the test conditions and the evaluation results.

[0035]

[Table 1]

Examples 9 to 11 Oxygen was supplied from pipe A at a flow rate of 1 liter / min,
Sterilization method of the present invention in the same manner as in Examples 1 to 8 except that an atomized product obtained by passing argon gas at a flow rate of 3 l / min through a nebulizer filled with 35% hydrogen peroxide solution was supplied from a pipe B. Was carried out. Table 2 shows the experimental conditions such as gas type and flow rate (pipe A), gas type and flow rate, liquid type and concentration (pipe B), treatment time, type of sterilized object (specimen) and residual bacterial count. .

[0037]

[Table 2]

Comparative Examples 15 to 17 Sterilization was carried out in the same manner as in Examples 1 to 8 except that only oxygen having a flow rate of 2 liter / min was supplied from the pipe A. About 1,000 ppm of ozone was generated by the supply of oxygen. Table 3 shows the type and flow rate of gas, the treatment time, the substance to be sterilized (specimen) and the number of remaining bacteria, which are the experimental conditions.

[0039]

[Table 3]

[0040]

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]

 DESCRIPTION OF SYMBOLS 1 ... Quartz coating electrode 2 ... Metal electrode 3 ... Ground electrode 4 ... Metal electrode 5 ... Introducing pipe (pipe A) 6 ... Introducing pipe (pipe B) 7 ... Covered Sterilizer 8 ... Exhaust pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeki Konno 1-4-16 Nihonbashi-Bakurocho, Chuo-ku, Tokyo Fujimori Industry Co., Ltd.

Claims (9)

[Claims] 1. A sterilizing method in which a mixture of a gas and a liquid at least a portion of which is ionized by an electric field is brought into contact with a substance to be sterilized, wherein the electric field is generated by a pulse voltage. 2. The rising speed of the pulse voltage is 0.01
The sterilization method according to claim 1, which is in the range of kV / ns to 10 kV / ns. 3. The sterilization method according to claim 1, wherein the pulse width is in the range of 10 ⁻⁹ seconds to 10 ⁻¹ seconds. 4. The peak voltage of the pulse voltage is 1 kVp-1.
The sterilization method according to any one of claims 1 to 3, which is in a range of 00 kVp. 5. The frequency of the pulse voltage is 1 Hz to 100 k.
The sterilization method according to any one of claims 1 to 4, which is in the range of Hz. 6. A mixture of gas and liquid in an electric field,
The sterilization method according to any one of claims 1 to 5, wherein at least a part of the mixture is ionized, and the mixture, at least a part of which is ionized, is brought into contact with an object to be sterilized within or outside the electric field. 7. A gas obtained by passing a gas through an electric field to ionize at least a part thereof, and a mixture of the gas and the liquid are mixed outside the electric field, and the obtained mixture is brought into contact with a substance to be sterilized. The sterilization method according to any one of 5 above. 8. The gas is at least one selected from the group consisting of oxygen, nitrogen, argon, helium and neon, and the liquid is water, hydrogen peroxide, hydrogen peroxide solution or ethanol. The sterilization method described. 9. The sterilization method according to claim 6, wherein the liquid is in a mist state.