JPH10192377A - Method for environmental sterilization by gaseous chlorine dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable rapid microorganism sterilization and access right after the sterilization without the change of equipment by hermetically closing devices and equipment in a simple booth and supplying gaseous chlorine dioxide to sterilize these devices and equipment, then removing the residual gaseous chlorine dioxide by a removing device. SOLUTION: The devices and equipment are hermetically closed by the simple booth; for example, a bag-shaped object consisting of the materials formed by using films of nylon, etc., having a high gas barrier property on the inner side and superposing polyolefin films on the outer side thereof. The gaseous chlorine dioxide is introduced from a chlorine dioxide generator into this booth in such a manner that the concn. of the gas attains about 1 to 500ppm, by which the devices and equipment are sterilized for about 1 to 24 hours. The residual gaseous chlorine dioxide is introduced into a the gaseous chlorine dioxide removing device and is removed by an oxidative gas removing agent after the sterilization treatment. For example, a two- stages system, etc., of forming an absorbent liquid by movable aq. soln. gas cleaning and sweep system and using this system together with active carbon are usable. The rapid sterilization and the immediate access after the end of the sterilization are made possible by this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The technical field to which the present invention pertains is:
The present invention relates to a method for sterilizing food processing plants, medical facilities, and equipment and machinery in these facilities.

[0002]

_2. Description of the Related Art Chlorine dioxide is a substance represented by the chemical formula ClO ₂ and is a gaseous substance at a normal temperature of a melting point of −59 ° C. and a boiling point of 11 ° C. It shows a solubility of 7000 ppm (mg / l), and the gas exists in a form dissolved in water like dissolved oxygen in water.
It has the property of being easily gasified as compared with dissolved oxygen. Further, it is a substance having strong oxidizing power and bactericidal property, and is useful for gas sterilization in food processing plants, medical facilities, and the like where it is necessary to maintain a high sanitary environment. However, chlorine dioxide is highly toxic, and the standard value for short-term working environment is 0.1 p.
At a very low concentration of pm (ml / m ³ ), it is particularly irritating to mucous membranes and eyes and corrosive. In addition, since it exhibits explosive properties at a gas concentration of 10% or more, there is no practical example of using chlorine dioxide gas by generating a large amount of gas other than bleaching pulp.

As a method for generating chlorine dioxide gas, chlorine dioxide gas produced by reacting solid chlorite with chlorine gas diluted with an inert gas is introduced into a gas chamber, and a gas containing moisture in advance is used. A method has been proposed in which an object to be sterilized is diluted with an inert gas or the like on a humidified surface and guided to sterilize bacterial spores (Japanese Patent Publication No. 5-86233, Japanese Patent Application Laid-Open No. 7-1636).
39) However, there is also a process of humidifying to a predetermined humidity, and the pilot stage, including the control of the concentration of chlorine dioxide, becomes a complicated system and becomes very expensive. There is no conceivable adaptation. On the other hand, a number of products referred to as stabilized chlorine dioxide are commercially available, including products intended to be used for sterilization by generating gas in a cardboard box for transportation or a small refrigerator. For example, a solution in which a 3% inorganic pH buffer substance or the like is added to a 5% sodium chlorite solution, is impregnated with zeolite, diatomaceous earth, or a hydrophilic resin, and dried to generate several ppm to several tens ppm of free chlorine dioxide gas. However, since the concentration of released chlorine dioxide is determined by factors such as the temperature and moisture concentration in the air, reliable sterilization cannot be guaranteed, and therefore, it can be used only in a limited small-scale specific state.

[0004] Bacterial spores are as difficult to sterilize as or more than mold spores, and are the two most important in the problem and difficulty of resistant bacteria in microbial control. Chlorine gas is an excellent disinfectant having the same disinfecting performance as chlorine dioxide, but it produces hydrochloric acid in the presence of moisture and is highly corrosive enough to make holes in stainless steel. They are usually used in cylinders and are no longer used due to dangers during transportation and earthquake countermeasures during use. Therefore, hypochlorite is widely used in food processing and general sterilization. Hypochlorite is highly corrosive to metals and sterilization is 10 to 100 times lower than that of chlorine, so it will necessarily be applied at a high concentration.
Since it is applied by wiping with a pm aqueous solution or spraying into the environment, metal products such as food processing machines have a drawback that significant corrosion occurs and the durability is reduced.

[0005] In gas sterilization, ethylene oxide, formalin, and sodium hypochlorite, which is not in a gaseous state, are also often used for environmental sterilization. However, ethylene oxide is likely to be a carcinogen and its use is being restricted. Formalin usually has a gas concentration of 6 g / m ³ (450
0 ppm) If it is not used for more than 7 hours, a sufficient bactericidal effect cannot be obtained, and if water vapor is not generated at the same time, paraformaldehyde crystals will be formed, which will condense on instruments and reduce the bactericidal effect, and it will take troublesome post-treatment of paraform. . 200
It has been reported that if 0 ppm gas was inhaled into rabbits, the animals died in 4 to 13 days. It is also well known that repeated contact at a low concentration causes symptoms of allergic contact dermatitis. Closely related to the danger, after formalin sterilization, aeration must be sufficient to eliminate formalin odor.Ammonia gas neutralization as a formalin treatment immediately after sterilization produces a large amount of hexamethylenetetramine. To adhere to instruments, etc. There is a major disadvantage that it requires deformalization treatment for a long time after sterilization and can be applied only to places with low productivity. In environmental sterilization by spraying sodium hypochlorite, sterilization of spores can hardly be expected, and severe damage to instruments due to high metal corrosiveness.

As described above, a gas which is low in corrosiveness, sterilizes microorganisms containing bacterial spores and mold spores in a relatively short time without changing existing equipment, leaves no odor after sterilization, and can enter immediately after sterilization. There has been no proposal for a method of sterilizing a gas environment which can be carried out inexpensively and easily, or a method of sterilizing an unportable machine or the like as it is.

[0007]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is that the corrosiveness is small and without changing the existing equipment,
A method of gas environment sterilization that can be performed easily and inexpensively by using a gas that can sterilize microorganisms containing bacterial spores and mold spores in a relatively short time, leave no odor after sterilization, and can enter immediately after sterilization, or a machine that is not portable It is an object of the present invention to provide a method for sterilizing gas or the like without any treatment.

[0008]

As a result of research conducted by the present inventors to solve the above-mentioned problems, equipment for sterilizing a chlorine dioxide gas generator and a remover by bringing them into an environment for sterilization, or by using a simple booth. The present invention has been completed by conceiving that sterilization can be easily performed by removing the residual chlorine dioxide gas after sterilizing with chlorine dioxide gas after sealing the airtight. That is, the present invention includes the following items 1 and 2. (1) bacteria, bacterial spores, mold,
In the method for disinfecting filamentous fungi, viruses or protozoa, the device and equipment are hermetically sealed by a simple booth, and then the inside of the booth is sterilized by chlorine dioxide gas generated by a chlorine dioxide gas generator shown in FIG. A method for removing chlorine dioxide gas remaining in a gas using the chlorine dioxide gas removal device shown in the figure. (2) The sterilization method according to the above (1), wherein a simple booth having a replaceable water tube at the lowermost portion and having a water inlet / outlet made of nylon inside and a polyolefin sheet outside is used. (3) bacteria, bacterial spores, mold,
A method for disinfecting a filamentous fungus, a virus or a protozoan by bringing a chlorine dioxide gas generating device shown in FIG. 1 and a chlorine dioxide gas removing device shown in FIG. 2 into a room.

[0009]

Embodiments of the present invention will be described below.

The concentration of chlorine dioxide gas suitable for sterilization by the method of the present invention is 1 to 500 ppm (ml / ml) in air.
m ³ ), and the contact time between bacteria and chlorine dioxide gas is 1
In order to obtain a more reliable effect, it is preferable that the chlorine dioxide gas concentration is 10 to 100 ppm and the contact time with the bacteria is 1 to 10 hours. Particularly desirable is 30 to 60 ppm for 3 to 6 hours. Bacteria, filamentous fungi, molds and viruses can be sterilized by using the sterilization method of the present invention, but they are particularly effective against spores and molds of Bacillus cereus (B. Cereus).

The method of the present invention is suitable for sterilizing medical equipment rooms such as a cool room for food processing, a clean room for pharmaceutical production, and an operating room. Specific examples of the food processing machine to which the method of the present invention can be preferably used include a crusher, a squeezer, a filling machine, and the like. Among them, a chopper as a meat processing machine that can be more preferably used,
Examples include a silent cutter, a stuffer, a slicer, a tumbler, and a packaging machine. It is particularly effective when careful sterilization of pack rice, a cool room for producing rice cake, an operating table, a patient transfer bed, and the like is required.

The simple booth used for sealing the object to be sterilized used in the method of the present invention can be a bag-like material, the material of which is a film-like material having a high gas barrier property such as nylon on the inside and a material on the outside. It is a laminated or laminated polyolefin film, which has a replaceable water tube at the bottom mainly for the purpose of keeping the airtightness with the floor surface. it can. Further, it is preferable that the simple booth has an entrance for water. The tightness of the simple booth can be improved by bonding the water tube and the floor with an adhesive tape or the like.

Generation of chlorine dioxide gas into the sterilizing environment is achieved by liberating chlorine dioxide in the solution by air bubbling of a movable amount of chlorine dioxide water or a two-liquid method in which chlorite is added to and reacted with an organic acid solution. This is achieved by using a chlorine dioxide gas generator of the type that generates and diffuses gas by air bubbling. Although it is not a control condition, as a secondary effect, chlorine dioxide gas contains an appropriate amount of moisture effective for sterilization and is superior because it is brought into a sterilizing environment and the aqueous solution is bubbled.

Further, in order to purify air mainly containing chlorine dioxide gas remaining after environmental sterilization with chlorine dioxide gas, a movable aqueous gas cleaning or sweep method brought in before carrying out environmental sterilization in advance is used. A two-stage method in which a deoxidizing substance from the absorbed aqueous solution is converted to activated carbon using activated carbon or a one-stage method using a scrubber of a dilute aqueous reducing solution such as thiosulfate can be used.
It is desirable to operate such a gas remover usually with a demister. Thus, humidification which is convenient for the propagation of microorganisms can be avoided when removing chlorine dioxide.

Chlorine dioxide water exhibits strong metal corrosivity like an aqueous solution of chlorine (hypochlorous acid), but metal corrosivity in a gas state at a concentration used for environmental sterilization is much smaller than that of an aqueous solution.

[0016] It is difficult to sterilize the entire environment in an environment where workers are constantly present. Therefore, in a place where machinery and operating table, etc. where microbial contamination is most likely to occur, simple packaging and sealing are performed, air is first released, then chlorine dioxide gas of a predetermined concentration is connected to the generator as bubbling gas and sealed. I do. After a predetermined sterilization time, residual gas is extracted through a gas remover.

[0017]

The present invention will be described more specifically with reference to the following examples. Reference Example 1. Sterilization effect by chlorine dioxide gas: Bacillus
B. cereus spores (hereinafter sometimes abbreviated as BC spores) and Escherichia coli (hereinafter sometimes abbreviated as ECs) 12 paper discs each inoculated with 10 ⁷ pieces of penicillium separated from rice cake production line Twelve paper disks were prepared by inoculating 50 μl of a fungus suspension of the genus Mold (hereinafter sometimes abbreviated as TP-1) with a wet cell weight of 0.135 g / 20 ml. Six of these discs were dry discs air-dried all day and night, and the remaining six discs were further sterilized with 50 μl of sterile water on the day of the test.
Was added to obtain a wet disk with 100% moisture.

[0018] A dry disk and a wet disk for each bacterial species prepared in this manner were placed in a Petri dish. Inside, chlorine dioxide gas was introduced into the desiccator. Chlorine dioxide gas was introduced as follows.

Attach a 100 L Tedlar bag at the outlet and put 1000 pp into a gas washing bottle filled with pH 8 buffer.
After adding the calculated amount of the chlorine dioxide water, air bubbling was performed to collect chlorine dioxide gas in a Tedlar bag. Immediately after sampling the concentration of the carbon dioxide gas, check with a detector tube.
After setting in one port of the desiccator, the other port was connected to an aspirator and suctioned to introduce chlorine dioxide into the desiccator. In the introduction, 80 L of air was ventilated over 1 hour, and then left for 4 hours with the cock on the aspirator side closed.

After the above operation is completed, the disk is taken out of the desiccator and placed on a sterilized nutrient medium in a thermostat.
After culturing for 20 hours, the presence or absence of bacterial growth was observed. As a control, the same culture was carried out using a disk not exposed to chlorine dioxide gas. The results are shown in Table 1. The number of bacterial propagation disks / total number of disks (6).

[0021]

[Table 1]

It can be understood from Table 1 that the sterilization by chlorine dioxide gas can be sterilized at a lower concentration in a state with moisture. However, moisture is not an absolute condition, and a more suitable condition is more desirable.

Reference Example 2 Sterilization effect by standing chlorine dioxide water: 1000 ppm chlorine dioxide water in an amount calculated so that the concentration of chlorine dioxide gas in the desiccator is 10 to 60 ppm is set on the bottom of a 40 L glass desiccator, and various kinds are placed on a plate. A paper disk inoculated with bacteria and fungi was set, covered with a desiccator, and allowed to stand for 15 hours, and the bactericidal property with naturally evaporated chlorine dioxide gas was examined. The inoculated bacteria are bacteria collected and identified from a clean room for pack rice processing, and the molds are bacteria collected and identified from a clean room for rice cake production. The number of inoculated bacteria per bacterium was 42,000 to 26 million.
And the same amount. The results are shown in Table 2.

[0024]

[Table 2]

From Table 2, it can be seen that all of the tested bacteria and fungi were completely sterilized at a chlorine dioxide gas concentration of 10 ppm or more. After 15 hours, the chlorine dioxide concentration is significantly lower than the charged amount, and an accurate CT value cannot be determined from this test. Numerous similar tests have shown that paper disks absorb significant amounts of chlorine dioxide gas, and the low concentration of chlorine dioxide after 15 hours is largely due to this absorption.

Example 1: Manufacture of Pack Rice (Measurement, Cooking, Sealing) Clean Room Sterilization of Clean Room A 80 m ³ rice washing measuring room, a 70 m ³ rice cooking room and a 70 m ³ seal room are separated by a door in a clean room (each room is manufactured at the time of manufacture). 30 to 60 m ³ / clean air blowing Yes in min) each room two chlorine dioxide generator, respectively (shown in a conceptual diagram of FIG.), chlorine dioxide remover (shown in a conceptual diagram of FIG.) Brought in. After charging 10 L of 2000 ppm chlorine dioxide water per chlorine dioxide generator, the air pump (blowing rate 15 L / min) of the chlorine dioxide gas generator was operated 30 minutes later and stopped after 5 hours.
The chlorine dioxide concentration was measured with a detector tube by suctioning room air from a Teflon tube inserted into each room. 10 minutes after the chlorine dioxide generator was stopped, the chlorine dioxide remover was operated to remove the chlorine dioxide gas. Fresh water was used as the absorbing aqueous solution used for the chlorine dioxide gas remover, and activated carbon was used as the oxidizing substance removing solid in the absorbing aqueous solution.

The start and end of the operation of the chlorine dioxide generator and the remover are automatically and appropriately performed by a timer, so that it is not necessary to perform the operation in the room during the operation. Table 3 shows the measurement results of the concentration of chlorine dioxide gas, Table 4 shows the results of the wiping test before and after sterilization in each room, and Table 5 shows the sterilization of a set of five paper disks inoculated with 10 ⁷ BC spores per disk. The results of exposure to the environment are shown.
From these results, in the actual environmental disinfection in a clean room, the disinfection effect is reduced because various manufacturing facilities are installed in the room, but the concentration of chlorine dioxide should be several times higher than the conditions in the laboratory test. It was found that BC spores having stronger viability also completely died. It was also found that the gas concentration could be reduced to a level that could be entered in a short time with the remover brought in.

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

Embodiment 2 FIG. Environmental sterilization of cut rice cake cleanroom: In a 68 m ³ rice cake cutting site, 15 L of an aqueous solution of 20% mixed organic acid and 6% chlorine compound are put into each of two chlorine dioxide gas generators shown in FIG. 60 minutes before, a 10% chlorite solution was added to each of the two generators for 65 minutes.
Then, the mixture was stirred and mixed, and then the lid was closed and transported to the quarry. After 10 minutes from the transport, an air pump (air flow rate 15 L / mi)
n) was started and the operation was stopped after 5 hours. The chlorine dioxide concentration was measured with a detector tube by sucking air from the quarry room through the inserted Teflon tube. The chlorine dioxide remover shown in FIG. 2, which was carried in at the same time as the carry-in of the generator, was operated 10 minutes after the generator was shut down. The absorption aqueous solution is 1% by weight of DMSO (dimethyl sulfoxide).
Hydrotalcite was used as fresh water to which oxidized substance was removed from the absorbing aqueous solution. The chlorine dioxide gas concentration after 1 hour was 30 ppm and 5 hours later was 22 ppm. By operating the remover, the gas concentration after 70 minutes of sterilization was 1 ppm, and after 100 minutes, 0.05 ppm.
Could be lowered to

The results of the wiping test before and after the sterilization are shown in Table 6. As is evident from the results,> 3000 (at least 3,000 or more innumerable due to propagation of mold and bacteria) before sterilization was sterilized as close to 0 as possible after sterilization.

[0033]

[Table 6]

Reference Example 3 Environmental sterilization of carcass refrigerator: When all carcasses of the carcass refrigerator of 900 m ³ used for carcass storage are removed and emptied, three plastic containers with lids containing 10 L of 2000 ppm chlorine dioxide water are brought in at 30 L /
Take two conduits from the min compressor, bubbling for 4 hours with air stones on each, then 1
The door was left open and closed for 0 hours. Confirmation of the bactericidal effect was carried out by wiping 10 cm ₂ of general viable bacteria, coliforms and molds and yeasts before and after sterilization, placing several kinds of bacteria and molds inoculated on a paper disk in a petri dish, placing them in a refrigerator, and taking out after 14 hours. It was performed by a method of culturing with an unsterilized one and confirming the remaining viable bacteria.

Table 7 shows the change in chlorine dioxide gas concentration, Table 8 shows the results of the wiping test, and Table 9 shows the results of the paper disk method. As is evident from these results, all of the general viable bacteria, coliform bacteria and molds / yeasts in the carcass refrigerator, and the bacteria and molds coated on the paper disk were completely sterilized. 1
After 4 hours, the chlorine dioxide gas concentration decreased significantly
This was due to leakage from the rubber skirt below the two refrigerator doors into the front room, and the front room was entered with an activated carbon mask.

[0036]

[Table 7]

[0037]

[Table 8]

[0038]

[Table 9]

Embodiment 3 FIG. Sterilization of meat slicer in simple booth: Slicer 700Kg / hr (7m / m thickness continuous) (NSC-C300 manufactured by Minami Jiko), which is anchored on the floor, can be expanded up to about 5m. Nylon film with a thickness of 100μ on the inside that becomes ³ ,
The outside is covered with a three-layer bag-like sheet made of a laminate film of vinylidene chloride and polyethylene with a thickness of 200μ. Tap water is placed in the water tube attached to the bottom of the sheet, and then the floor is covered with transparent vinyl tape. The tube was brought into close contact with the water tube. After a vacuum pump was connected to a gas suction port provided in advance in the sheet to remove most of the air inside, the degree of sealing was checked, and 3 m ³ of air was injected. Thereafter, air containing chlorine dioxide gas generated by bubbling a gas washing bottle containing 380 ml of 2,000 ppm chlorine dioxide water at a rate of 15 L / min is sent into the sheet at 15 L / min for 2 hours, and then the gas concentration in the sheet is detected. Was 50 ppm.
Then, after leaving it for about 3 to 10 hours, at the end of sterilization, air in the sheet was evacuated for about 1 hour by a vacuum pump connected with a large gas washing bottle containing a 10% aqueous solution of sodium thiosulfate and a mist trap. As a result of measuring the gas concentration in the sheet when it reached about 3 m ³ by sending air again, the result was 0.01%.
ppm or less. In the wiping test performed before and after the sterilization, the average of 10,000 cells / cm ² before sterilization was increased to 10 averages / cm ² after sterilization, which proved that the sterilizing effect was sufficient.

[0040]

According to the sterilization method using chlorine dioxide gas of the present invention, part or all of the environment and large machinery can be easily and reliably sterilized. Further, since chlorine dioxide gas can be removed in a short time after sterilization, the working time can be reduced. Furthermore, this method can be carried out anywhere since there is no need to disinfect microorganisms and protozoa, including bacterial spores and molds, at all. By the method of the present invention, mechanopathogenic Escherichia coli and the like can be easily removed from the food processing environment and food processing to improve food safety. Further, it is effective in preventing opportunistic infections caused by MRSA or the like, thereby realizing an environment in which medical treatment can be safely received.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a chlorine dioxide gas generator.

FIG. 2 is a conceptual diagram of a chlorine dioxide gas remover.

[Explanation of reference numerals] Gas generator main body Pump etc. storage Air pump Timer Power supply Air piping tube Air stone 1 Removal device main body 2 Water circulation pump 3 Water supply pipe 4 Remover packed column 5 Coarse particle removal filter 6 Membrane filter 7 Inlet side blower 8 Exhaust-side blower 9 Demister 10 Sprinkler tube 11 Inlet-side shutter 12 Exhaust-side shutter

Claims (3)

[Claims] 1. A method for disinfecting bacteria, bacterial spores, molds, molds, viruses or protozoa attached to equipment and equipment, wherein the equipment and equipment are hermetically sealed with a simple booth and then the interior of the booth is sterilized with chlorine dioxide gas. Later
A method of removing chlorine dioxide gas remaining in a simple booth with an oxidizing gas absorbent. 2. A replaceable water tube at the bottom made of a sheet of nylon on the inside and a sheet of polyolefin on the outside,
The sterilization method according to claim 1, wherein a simple booth having a water inlet / outlet is used. 3. A method for disinfecting bacteria, bacterial spores, molds, molds, viruses or protozoa adhering to a closed room, wherein a chlorine dioxide gas generator and a chlorine dioxide gas remover are brought into the room and disinfected. .