JPH0583117B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for sterilizing microorganisms generated in metalworking fluids by irradiating them with radiation. Prior Art When performing metal processing such as metal cutting, rolling, polishing, and heat treatment, metal processing fluids (hereinafter referred to as coolants) are used for purposes such as lubrication and cooling.
As the coolant, water-soluble oil agents such as emulsion type, soluble type, and solution type are often used. In addition, the above-mentioned coolant has suitable conditions for the growth of microorganisms, such as water, organic oil, heat generated during metal processing, and a moderate temperature due to temperature rises in summer, etc. Problems such as metal processing failure and metal corrosion occur. Conventional measures to prevent the above problems include the aeration method by blowing air to suppress the growth of anaerobic bacteria, the ozone sterilization method by blowing ozone-containing air, the heat sterilization method by heating using steam or electric heat, and the preservative and antifungal agent. A drug addition method that adds . Problems to be Solved by the Invention Among the conventional coolant sterilization methods described above, the aeration method, ozone sterilization method, and heat sterilization method have problems such as increased equipment and operating costs, bacterial growth inhibiting effect, and effect sustainability. has the disadvantage of low
Furthermore, the heat sterilization method may destroy the emulsion in an emulsion-based coolant. The drug addition method has disadvantages such as the tendency to react with additives such as surfactants in the coolant, the fact that certain drugs have a growth inhibiting effect only on certain bacteria, and the duration of the effect is short. There is also contamination of the working environment due to evaporation and scattering of chemicals. The present invention has been made to eliminate the drawbacks of the conventional methods described above, and it has a bactericidal and growth inhibiting effect regardless of the type of microorganism, has a stable effect, and does not cause the coolant itself to denature or change in quality. This was developed with the aim of providing a method for sterilizing microorganisms generated in coolant. Means for Solving the Problems The present invention provides a method for sterilizing microorganisms generated in a coolant by irradiating them with radiation, at an irradiation dose rate of 40 to 10,000 kiloroentgen/hour (KR/Hr) and a total absorbed dose of 10 to 5,000. It is characterized by continuous processing under Krad sterilization conditions. still,
In the above, the irradiation dose rate refers to the irradiation dose per unit time, and the total absorbed dose refers to the cumulative absorbed dose of the absorbed dose absorbed by the coolant at one time in the irradiation section. In the above, it is preferable to irradiate radiation by continuously circulating the coolant to the irradiation part from the viewpoint of radiation shielding and operability ^.
It is better to use The method of the present invention will be explained in detail below based on the drawings.
FIG. 1 is a diagram of an apparatus applied to an embodiment of the method of the present invention, and is a system diagram of a continuous circulation type apparatus. FIG. 2 is a cross-sectional view of a batch-type device as a comparative example. FIG. 3 is a cross-sectional view of a preferred irradiation container used in a continuous circulation system. In FIG. 1, reference numeral 1 denotes a constant temperature tank in which a coolant stock solution A is maintained and stored at a constant temperature, and the constant temperature tank 1 is equipped with a temperature controller 6 and an agitator 7 to make the liquid temperature uniform. 2 is a supply pump that extracts the stock solution A from the constant temperature bath 1 and supplies it to the irradiation unit from the supply channel 8; The flow rate is adjusted by the flow control valve 3b. Reference numeral 4 denotes an irradiation container that is surrounded by an irradiation part shielding material such as lead and irradiates the raw solution A with radiation, and there is a spiral supply channel 8 in the container 4, and a supply channel 8 in which radiation is supplied from the outside of the supply channel 8. It is equipped with a radiation source 5 provided to irradiate.
Reference numeral 10 denotes a circulation channel for circulating the irradiated stock solution A to the constant temperature bath 1. In FIG. 2 of the batch-type comparative example, the irradiation container 4 is equipped with a stock solution container 11 filled with stock solution A, and a radiation source 5 provided to irradiate radiation from the outside of the stock solution container 11. ing. Figure 3 shows the Utility Application filed in 1983 by the present applicant.
This is a radiation processing container according to an embodiment of No. 83019, in which a radiation source 5 is disposed in the middle of the flow path for the stock solution A in which the inlet side flow path 12 and the outlet side flow path 13 are each bent multiple times, It is an irradiation container in which the outer periphery of the flow path and the radiation source 5 are enclosed by a lead body and lid. By using the irradiation container 4 for implementing the present invention,
This is a very suitable irradiation container because it simplifies the processing work, greatly reduces radiation exposure to workers, and ensures sufficient safety. In the method of sterilizing microorganisms generated in the coolant by irradiating it with radiation, first of all, in the continuous circulation type,
The stock solution A kept at a constant temperature inside is supplied into the irradiation container 4 by the supply pump 2, and after a certain residence time is irradiated with radiation by the radiation source 5, it is transferred to the circulation channel 1.
0 and returned to constant temperature bath 1. The above residence time, that is, the flow rate of the stock solution A can be adjusted by appropriately adjusting the flow path control valves 3a and 3b. In addition, in the batch method of the comparative example, a certain amount of stock solution A is placed in stock solution container 1.
This is carried out by filling the radiation source 1 into the irradiation container 4 and placing it in a fixed position where the outer surface faces the radiation source 5 in the irradiation container 4. In the above, the radiation source 5 has a radiation source capacity of 5 to 50
Kilokily (Kci), preferably 10-30Ki
It is better to use a ⁶⁰ Co source. If the radiation source capacity is less than 5Kci, the radiation is too weak, the sterilization effect is low, and the processing time is long.If it is more than 50Kci, the shielding of the radiation will be large-scale, and the transportation of the irradiation container and the equipment will be large-scale. The irradiation dose rate of the radiation to be irradiated is 40 to 10,000 KR per hour, preferably 500 to 2,000 KR,
Also, the total absorbed dose that stock solution A absorbs in the irradiated area is
It is good to set it to 10-5000 Krad, preferably 50-1000 Krad. If the irradiation dose rate is less than 40KR/Hr or the total absorbed dose is less than 10Krad, the sterilization effect will be low;
The antiproliferative effect is also difficult to sustain. The irradiation dose rate
If the total absorbed dose is 10,000KR/Hr or more or the total absorbed dose is 5,000Krad or more, the bactericidal effect will increase, but it is useless for purposes such as preventing bad odors by suppressing the growth of bacteria and preventing metal processing problems, and it may also cause denaturation and deterioration of the coolant itself. There is a risk of Example 1 Table 1 shows the results of a sterilization test on used coolant using the continuous circulation type device shown in FIG. A ⁶⁰ Co source with a source capacity of 20 Kci was used as the source. The number of viable bacteria was measured using the agar plate smear method under the following conditions. Culture conditions Aerobic culture medium; Try Pticase Soy Agar Temperature: 30-32°C Time: 1-2 days Comparative Example 1 Sterilization test of used coolant using the batch type device shown in Figure 2 The results are shown in Table 2. A ⁶⁰ Co source with a source capacity of 20 Kci was used as the source. The measurement of viable bacteria was the same as in Example 1.

【table】

[Table] From the table above, when the irradiation dose rate is 50KR/Hr and the total absorbed dose is around 10Krad or more, the number of viable bacteria decreases.
That is, it can be seen that it has bactericidal and growth inhibiting effects. Although we have not measured anaerobic bacteria, they are less resistant to radiation than aerobic bacteria, so they can be as effective as or even more effective than aerobic bacteria. Effects The radiation sterilization method for metal working fluids of the present invention has the following effects. B. It has a bactericidal and growth-inhibiting effect regardless of the type of microorganism, and has a stable and long-lasting effect. (b) Since sufficient radiation shielding can be easily performed, there is less contamination of the working environment compared to sterilization methods using chemicals, and health hazards to workers can be prevented. C. Because the equipment used is simple, equipment costs are low, and drug costs can also be reduced. D. Since stable effects can be obtained, the property management of the coolant can be simplified and the yield of metal processed products can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a continuous circulation type device applied to an embodiment of the method of the present invention, and FIG. 2 is a sectional view of a batch type device as a comparative example. FIG. 3 is a cross-sectional view of one embodiment of an irradiation container in a continuous circulation system. DESCRIPTION OF SYMBOLS 1... Constant temperature bath, 2... Supply pump, 3a, 3b... Flow rate control valve, 4... Irradiation container, 5... Radiation source, 6... Temperature controller, 7... Stirrer, 8... Supply channel, 9... Bypass channel, 10 ... Circulation channel, 11... Stock solution container,
12... Inlet side flow path, 13... Outlet side flow path.

Claims (1)

[Claims] 1. In a method of sterilizing microorganisms occurring in metalworking fluids by irradiation, metalworking fluids are continuously circulated to the irradiated area and used as a radiation source.
A method for radiation sterilization of metalworking fluids, which uses ⁶⁰ Co and is characterized by irradiation treatment under sterilization conditions at an irradiation dose rate of 40 to 10,000 kiloroentgens/hour and a total absorbed dose of 10 to 5,000 kilorads.