JPH11187872A - Sterilization by pulse high-voltage corona discharge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sterilizing an article by high-voltage pulse impression corona discharge in high sterilization efficiency and a method for sterilizing an article especially in a covered state with a packing material or the like. SOLUTION: This method for sterilizing an article comprises exposing articles 2 and 2' to a corona discharge generated by a pulse high-voltage having >=0.1 μsec pulse width, 4-100 kv/cm electric field strength and >=10 pps pulse frequency. In the case in which the articles 2 and 2' contain a metal part, a discharge electrode 3 is covered with a dielectric substance to uniform a discharge state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sterilizing articles by corona discharge applying a high voltage pulse, and more particularly to a method for sterilizing an article present inside a container or an article surrounded by packaging material.

[0002]

2. Description of the Related Art There has been known a method of sterilizing articles to which microorganisms such as bacteria and mold are adhered by using corona discharge. For example, Japanese Patent Application No. 63-318947 discloses a sterilization method in which an object to be treated is introduced while flowing a gas containing oxygen in a discharge space to generate pulse corona discharge to kill microorganisms. Patent Publication No. 2651740
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a method of applying a high-voltage pulse to the surface of a liquid whose pH has been adjusted to a range of 5 to 9 to sterilize microorganisms existing in the liquid. As described above, sterilization by corona discharge can be performed at room temperature, and there is no need to use a chemical or the like, and the treatment can be completed in a short time. Therefore, these methods do not have to worry about the deterioration of the substance due to heat,
It is attracting attention as a sterilization treatment method that is excellent in safety and efficiency, for example, because an accompanying post-process such as drying is not required.

However, the method disclosed in Japanese Patent Application Laid-Open No. 63-318947 is characterized in that oxygen flowing together with an article is activated by corona discharge, and sterilization is performed by the activated gas. It is essential. Therefore, this method cannot sterilize articles in enclosed spaces, such as articles being packaged. The method disclosed in Japanese Patent Publication No. 2651740 is designed for the purpose of sterilizing microorganisms in a liquid, and does not describe sterilization of articles present in the atmosphere. In both cases, the distance between the electrodes is limited because the applied voltage is low. Therefore, it cannot be applied to tall articles or articles having complicated shapes. Furthermore, the conventional corona discharge has a problem that articles contained in a container or the like cannot be sterilized.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for disinfecting an article with high efficiency by corona discharge applying a high voltage pulse, and more particularly, a method for disinfecting an article surrounded by a packaging material or the like.

[0005]

According to the present invention, the pulse width is set to 0.1.
The present invention relates to a method for sterilizing an article by exposing the article to a corona discharge generated by a pulsed high voltage having a field intensity of 4 to 100 kv / cm and a pulse frequency of 10 pps or more, for 1 μsec or more. In particular, the present invention relates to a method for sterilizing an article in an enclosed space according to the above method. In addition, the present invention relates to the above-mentioned method for sterilizing an article, in which the discharge electrode is made uniform by covering the discharge electrode with a dielectric when the article contains a metal portion.

A feature of the present invention is that the pulse width is 0.1 μsec.
As described above, the electric field strength is 4 to 100 kv / cm, and the pulse frequency is 10
Since corona discharge having high energy generated using a pulse high voltage of pps or more is used, the degree of freedom with respect to the height and shape of the article to be processed is large. A distinctive feature of the present invention is that the use of high energy corona discharge also allows for sterilization of articles present inside the container or articles surrounded by packaging material. In this specification, “enclosed” refers to a state in which the surface (usually the upper surface) of the article with respect to the discharge electrode is covered with some material. At this time, the side surface may be open. Further, according to the method of the present invention, the pulse waveform as described above is selected in spite of generating a discharge having a strength effective for sterilization, and does not exert a thermal effect on the object to be processed. .

The excellent bactericidal action of the present invention is achieved by a corona discharge generated from a pulsed high voltage characterized by a steep rise and a high peak value, by an article inserted into the discharge area and further by a dielectric material. It is based on the fact that a strong electric field can be applied to bacteria and mold spores adhering to an enclosed article, and at the same time, an active atmosphere consisting of ozone and active ions is generated inside the container surrounding the article and near the surface. A strong germicidal action is produced by the synergistic action of these electric fields and active atmosphere. Therefore, the sterilization method of the present invention, instruments and waste materials used in medical institutions and biological research institutions, such as petri dishes and pipettes used in microbial experiments,
It is particularly useful for sterilizing used injection needles and the like.

By applying a pulse high voltage having a unique waveform shown in FIG. 4, a stable corona discharge is maintained between the discharge electrode and the counter electrode. In this discharge, a high voltage is applied in the form of a pulse with an extremely short rise time, so that it does not induce molecular motion in the object to be processed, but only accelerates electrons to generate an active atmosphere. The resulting heat generation is small, and the temperature of the object to be processed hardly rises.
In addition, since the pulse voltage used for the main discharge reaches 200 kV or more at maximum, the space where the active atmosphere is generated (distance between electrodes)
Can be made larger than a normal corona discharge.

Due to the large energy, not only the vicinity of the surface of the substance to which bacteria and spores are directly opposed to the discharge electrode but also the gas (usually air) atmosphere in the space surrounded by the dielectric material is activated. It is possible to state. In other words, a strong electric field that contributes to sterilization affects the enclosed space. By utilizing this characteristic, it is possible to treat the inside of a package or enclosure without necessarily facing the electrode directly to the surface to be treated or spraying an active atmosphere on the surface to be treated as in the prior art. is there. The strength of the treatment can be changed by changing the distance between the electrodes (within the range in which the article can be inserted) or by changing the discharge irradiation time, and can be freely adjusted according to the bacteria and spore species.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pulse high voltage applied for causing a discharge is selected as follows. The pulse width is 0.1
μsec or more, preferably 0.5 to 20 μsec. At less than 0.1 μsec, good corona discharge hardly occurs. On the other hand, as the pulse width becomes wider, the effective discharge energy increases, so that the sterilizing action becomes stronger. Alternatively, corona discharge extends to the surface of the object to be processed. That is, the processing efficiency is improved, and the desired bactericidal effect can be achieved in a short time. In addition, when the pulse width is large, even if the distance between the electrodes is increased, a corona discharge of sufficient strength can be generated, and a good sterilization effect is achieved. When used, a discharge electrode can be arranged at a position distant from an object to be processed. As a result, a relatively simple shape of the electrode can be adopted even if the object to be processed has a complicated shape, and it is not necessary to change the shape of each electrode for each article to be processed. However, if the pulse width is too long, harmful sparks are likely to occur and the power supply capacity increases, so it is preferable to set the pulse width to 20 μsec or less.

The discharge phenomenon is also affected by the applied voltage. The applied voltage for corona discharge is the average electric field strength (applied voltage
(Peak value)) / distance between poles) 4 to 100 kV / cm
It is. When it is lower than 4 kV / cm, good corona discharge is unlikely to be generated, and when it is higher than 100 kV / cm, it is easy to shift to spark discharge, and the insulation means is complicated and expensive for the effect. The pulse frequency is 10 pps or more, preferably 10 to 2000 pps. If it is less than 10 pps, good corona discharge is unlikely to occur, and the effective treatment energy is insufficient, so that it takes a long time for the sterilization treatment. On the other hand, if the pulse frequency is too high, heat may be generated. Also 200
It is technically difficult to generate a high-voltage pulse having a pulse frequency exceeding 0 pps with the above-described pulse width and average electric field strength. Attempting to obtain a pulse frequency of 2000 pps or more is not preferable because the high voltage generator becomes very large, the equipment cost becomes excessive, and industrial profitability becomes impossible.

As the high-voltage pulse generator, basically, a high-voltage pulse generator in a conventional corona discharge treatment method can be used.

In processing an article under the above-mentioned discharge generating conditions, the object to be processed is placed in a discharge area between a discharge electrode connected to a high voltage and a grounded counter electrode as shown in FIG. I will The workpiece may be discharged while moving in the discharge region, or may be discharged while stopped in the discharge region. If the object to be processed is a dielectric such as plastics, paper or glass, it may be placed in the discharge region as it is, or may be coated or packaged with a dielectric material (FIG. 1A). When the object to be treated contains a conductive substance such as a metal, uniformity of discharge can be maintained by coating the discharge electrode with a dielectric (FIG. 1).
(B)). The dielectric used to coat the discharge electrode is
It is necessary that the discharge electrode has such a shape and arrangement that it is completely closed in the direction facing the counter electrode. “Completely closed” means that when discharge is performed, spark discharge does not occur between the discharge electrode and the metal contained in the object to be processed. Therefore, in addition to a state in which the dielectric completely covers the discharge electrode, a state in which the dielectric has a sufficient distance in the creeping direction of the discharge electrode can be adopted. As the material of the dielectric, vinyl chloride, glass, ceramics, and the like are preferable, and these are more preferably 3 mm or more in thickness. However, this is not always necessary when the conductive object is wrapped or surrounded by a dielectric material and spark discharge does not occur.

It is preferable that an insulator is interposed between the counter electrode and the plastic to be processed. In this way, even when the applied voltage (peak value) is high and the average electric field strength is high, generation of harmful sparks can be prevented. As the insulator, a vinyl chloride resin, a Teflon resin, and other general dielectric materials can be arbitrarily used. The thickness of the insulator is 1 mm or more, preferably 5 to 20 mm. If the thickness of the insulator is less than 1 mm, the spark preventing effect is insufficient. Even if the thickness is more than 20 mm, there is no difference in the effect of the treatment. The position of the insulator is not particularly limited, and can be installed at an arbitrary position. When a relatively thin insulator layer is formed on the surface of the counter electrode, the counter electrode must be 0.1 in order to obtain sufficient mechanical strength and durability.
mm or more, desirably 1.6 mm or more is preferably used. A thin film or foil of a conductive material such as copper or aluminum formed on the back surface of the insulator may be used as the counter electrode. In this case, it is preferable that the thickness of the dielectric is made larger, for example, about 5 mm or more in order to have mechanical strength.

The shape of the discharge electrode and the distance between the electrodes can be appropriately changed according to the shape and size of the object to be processed. Various shapes such as a spherical shape, a brush shape, and a knife edge shape are possible as shown in FIG. When a small electrode such as a spherical discharge electrode is used, a plurality of such electrodes may be used and arranged in a linear shape, a circular shape, a plurality of linear shapes, or the like. As for the distance between the electrodes, the electric field strength is 4 to 100 kv / c
It can be changed freely within the range of m. The positional relationship between the electrode and the object to be processed may be such that the discharge direction is a horizontal direction or an upward direction from the bottom as long as the object is within the discharge region.

[0016]

The present invention will be described more specifically with reference to the following examples. Example 1 An L-broth medium was spread, and E. coli ( Escherichia coli ) was spread thereon for about 1, 2, respectively.
A plurality of Petri dishes containing 000 pieces were placed in the discharge area of the corona discharge treatment device with the lid kept, and the pulse width was 2 μsec,
The discharge treatment was performed at a pulse frequency of 80 pps while changing the electric field strength and the treatment time as shown in Table 1. The electric field intensity was changed by changing the distance between the electrodes. The processing status is as shown in FIG. After the treatment, the cells were cultured at 37 ° C. for 12 hours, and the growth state of Escherichia coli was visually evaluated. Table 1 also shows the results.

[0017]

[Table 1]

Example 2 A potato dextrose medium was spread, and black mold ( Aspergillus niger ) was spread thereon for about 50 minutes each.
The plurality of petri dishes thus placed were placed in a discharge region of a corona discharge treatment device with the lid kept, and subjected to discharge treatment with a pulse width of 2 μsec and a pulse frequency of 80 pps while changing the electric field intensity and the treatment time as shown in Table 2. The electric field intensity was changed by changing the distance between the electrodes. After treatment, culture at 25 ° C for 6 days,
The growth status of black mold was evaluated by the state of colony formation. Table 2 also shows the results.

[0019]

[Table 2]

Comparative Example 1 Escherichia coli and black mold were cultured in the same manner as in Examples 1 and 2 except that the discharge treatment was not performed. As a result, both Escherichia coli and black mold bred on the entire surface of the petri dish.

In the first and second embodiments, the electric field strength is 33 kv / cm (electrode distance 3 cm), and the processing time is 120
FIG. 3 shows photographs of the breeding state after culturing the sample treated in seconds and the sample of the comparative example (no discharge treatment). Table 1,
As shown in Table 2 and FIG. 3, by selecting the electric field strength and the processing time, it is possible to sufficiently sterilize bacteria and mold even when the article is processed in a petri dish.

[0022]

By treating the article in the corona discharge region generated by the application of the high pulse voltage according to the present invention, bacteria and mold spores attached to the article can be efficiently sterilized at normal temperature and normal pressure. In the method of the present invention, the distance between the electrodes and the discharge energy can be made large, so that the size and shape of the object to be processed can be selected widely. In particular, it is possible to sufficiently sterilize articles surrounded by a dielectric material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a processing state in a sterilization method of the present invention. (A) When the article is a dielectric, (b) When the dielectric contains a conductive substance.

FIG. 2 shows an example of the shape of a discharge electrode that can be used in the present invention.
(A) a spherical electrode, (b) a brush type electrode, and (c) a knife edge type electrode.

FIG. 3 is a photograph showing the breeding state of Escherichia coli and black mold subjected to electric discharge sterilization treatment by the method of the present invention.

FIG. 4 shows an example of a high voltage pulse for corona discharge generation used in the sterilization treatment of the present invention.

[Description of Signs] 1: Petri dish (with lid), 2: Object to be treated in petri dish, 2 ': Object to be treated containing metal in petri dish, 3: discharge electrode, 4: counter electrode, 5: insulating plate,
6: high voltage power supply, 7: derivative covering the discharge electrode, 8: discharge region.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Ando 19-17 Ikedanakacho, Neyagawa-shi, Osaka Inside Nippon Paint Co., Ltd. Inside the corporation

Claims (3)

[Claims] 1. A method for sterilizing an article by exposing the article during corona discharge generated by a high voltage pulse having a pulse width of 0.1 μsec or more, an electric field strength of 4 to 100 kv / cm, and a pulse frequency of 10 pps or more. 2. The method for sterilizing an article according to claim 1, wherein the article is surrounded by a dielectric material. 3. When the article includes a metal part, the discharge electrode is covered with a dielectric to make the discharge state uniform.
A method for sterilizing an article according to the above.