JPH0695952B2 - Method for evaluating microbial deterioration resistance of water-soluble oil agents for metal processing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for evaluating microbial deterioration resistance of a water-soluble oil agent for metal processing, particularly a water-soluble cutting oil agent. Therefore,
INDUSTRIAL APPLICATION This invention can be utilized in the industrial field which manufactures the oil agent for metal processing, or the industrial field of metal processing.

2. Description of the Related Art A water-soluble oil for metalworking is usually diluted with water by a factor of 10 to 100 before use. This diluted solution is called coolant. The coolant is required to have performance required for processing (primary performance) and performance related to workability (secondary performance). Among them, secondary performances include good antiseptic properties, good rust preventive properties, deterioration-resistant and easy-to-manage, harmless to human body, low foaming, etc. Is meant to prevent deterioration due to the above, and such performance is referred to as "resistance to microbial deterioration" in the following description.) Is a very important issue.

Further, in order to develop an oil agent having good resistance to microbial deterioration, it is necessary to quickly and accurately evaluate the resistance to microbial deterioration of the oil agent.

Conventionally, there are the following methods for evaluating the microbial deterioration resistance of water-soluble oil agents for metal processing.

1. A method in which the oil solution is diluted to a certain concentration, and about 1 to 2% of spoilage solution is added over time in a thermostat at 30 to 37 ° C to measure changes in properties and viable cell count. This method requires a test period of about one month.

2. A method of diluting an oil agent to a certain concentration, circulating this, and adding a certain amount of a spoilage solution in the presence of cast iron to measure changes in properties over time and the number of viable bacteria. This method also requires a test period of about one month.

3. A method in which cast iron chips, corn powder, and a spoilage solution are added to a dilute solution of a fixed concentration to measure changes in properties over time and the number of viable bacteria. This method requires a test period of 2 weeks to 2 months.

The above method has the following drawbacks.

Evaluation takes a long time.

Poor reproducibility.

Due to the relative evaluation between oil solutions, it is difficult to compare samples without simultaneous testing.

Therefore, it is desired to develop an evaluation method that can be evaluated in a short period of time and that is accurate.

Problems to be Solved by the Invention Under the circumstances as described above, the present invention aims to provide a method for rapidly and accurately evaluating the microbial deterioration resistance of a water-soluble oil agent for metalworking.

Means for Solving the Problems As a result of intensive studies on the method for evaluating the microbial deterioration resistance of a water-soluble oil agent for metalworking, the present inventors have found that a stock solution or dilution solution of an oil agent to be evaluated and a spoilage solution or a fungal dispersion solution can be used. The inventors have found that it is possible to evaluate the microbial deterioration resistance with high accuracy and in a short period of time by checking the presence or absence of viable bacteria in the mixed solution by mixing at a ratio of 1.

That is, the gist of the present invention is to mix a stock solution or a diluting solution of a water-soluble cutting fluid for metalworking to evaluate microbial deterioration resistance with a spoilage solution or a fungal dispersion of a water-soluble cutting fluid for metalworking at various ratios. After a certain condition, after collecting a part of the mixed solution and culturing in a nutrient medium, based on the result, check the presence or absence of viable bacteria in each mixed solution and prevent the growth of the bacteria. The present invention relates to a method for evaluating the microbial deterioration resistance of a water-soluble oil agent for metal processing by knowing the minimum concentration of the oil agent that can be obtained.

(Details of Operation) The present invention will be described in detail below.

The evaluation method of the present invention is carried out by the following operations.

A solution is prepared by mixing a water-soluble oil agent for metalworking (stock solution or diluted solution) and a septic solution of the water-soluble oil agent for metalworking at various ratios, which is to be evaluated for microbial deterioration resistance. For example,
A 20-fold diluted solution of the stock solutions of the water-soluble cutting fluids A and B for metalworking and an emulsion-type septic solution are mixed in the ratio shown in Table 1.

This mixed solution is allowed to stand at room temperature, and after 24 hours, one platinum loop of each mixed solution is sampled and spread on ordinary agar plate medium, and the temperature is set to 37 ° C.
Incubate for 48 hours.

The culture results are indicated as (+) when the bacteria are growing and as (...) When the bacteria are not growing. For example, suppose that the culture results of the mixed solution in Table 1 are as shown in Table 2.

From the results of the culture shown in Table 2, compare the lowest ratio (mixed sample No. 3 in the case of sample A, mixed sample No. 5 in the case of sample B) that the oil agent inhibits the growth of bacteria. By
It is possible to compare and evaluate the microbial deterioration resistance of oil solutions. In the case of this example, Sample A is superior in microbial deterioration resistance.

As can be seen from the above, the time required for the method of the present invention is about 5 days.

It is considered that the result of the culture depends on the viable cell count and bacterial flora of the putrefaction solution used, the conditions for leaving the mixed solution, and the like.

Therefore, the following experiments were conducted to investigate the influence of each.

(Experimental conditions) Type of spoilage liquid A: Emulsion-type cutting fluid spoilage fluid (viable cell count 5 × 10 ⁶ / ml) B: Soluble-type cutting fluid spoilage fluid (viable cell count 5 × 10 ⁷ cells / ml) C: Emulsion-type cutting oil spoilage liquid (viable cell count 1 × 10 ⁸ pieces / ml) Standing temperature Room temperature, 30 ° C, 37 ° C Standing time 6 hours, 12 hours, 24 hours Sample oil sample oil S (emulsion type Cutting oil: JIS W1 type 1, 20 times liquid) Sample oil T (emulsion type cutting oil: JIS W1 type 2, 20 times liquid) Sample oil U (Soluble type cutting oil: JIS W2 type 2, 20 times liquid) (Experimental method) Mix sample oil (20 times each solution) and spoilage liquid at various ratios (volume ratio, eg, sample oil / spoilage liquid = 1/9 to 8/2) and change the temperature and time to prepare the soil. To do. After standing, collect 1 platinum loop of each mixture and apply it to agar plate medium at 37 ℃.
Incubate for 48 hours at (+) when there is bacterium growth, and (-) when there is no bacterium growth.

The results are shown in Tables 3, 4, and 5.

From the results of Tables 3 to 5, it is recognized that the standing temperature and the standing time have little effect on the results, but the effect of the viable cell count of the septic solution is large. Therefore, in the method of the present invention, it is necessary to keep the viable cell count of the spoilage solution used constant, but it is difficult to control the viable cell count. Therefore, in order to compare the test results, it is desirable to define a standard sample and compare the results. When the results of the standard samples are different, the results can be corrected to facilitate the comparison between the samples.

In addition, in the method of the present invention, resistance to microbial deterioration can be quantified.

Since the method of the present invention shows the minimum concentration (minimum ratio) of the oil agent capable of inhibiting the growth of bacteria in a certain spoilage liquid, for example, the deterioration resistance to bacteria is
(Bacteriocidal index) value, and if BI value is defined as follows, K: Constant A: Ratio of new liquid B: Ratio of spoiled liquid T: Magnification ratio of new liquid The larger the BI value, the better the deterioration resistance to bacteria. This BI value makes the comparison between samples clear.

Similarly, an index of deterioration resistance to mold and yeast (FI
Value: fungicidal index, EI value: eastocidal index) can be set.

Furthermore, by conducting the test simultaneously with the standard sample, BI
If the values, FI values, and EI values are corrected, it becomes possible to compare samples even under different conditions.

(Conventional Evaluation Method) For comparison with the method of the present invention, the resistance of the oil agent to microbial deterioration was evaluated by a conventional method.

(Experimental conditions) Sample oil Sampling oil S (emulsion type cutting oil: JIS W1 type 1, No. 20 liquid) Sample oil T (emulsion type cutting oil: JIS W1 type No. 2, 20 times liquid) Sample oil U (Soluble type Cutting fluid: JIS W2 No. 2, 20 times liquid) Septic fluid C: Emulsion type cutting fluid spoilage solution (viable cell count 1 × 10 ⁸ / ml) Test temperature 30 ℃ Sample volume 10l Test period Approx. 1 month (Experiment Method) Add 10 l of sample oil and 1 kg of cast iron chips (packed in a gauze bag) to an 18 l container and circulate with a circulation pump (10 l /
min). Every 3 to 5 days, 100 ml of spoilage solution is added and changes in properties over time and viable cell count are measured.

The experiment was performed twice under the same conditions. The results are summarized 6th
Shown in the table.

As a result of conducting the experiment twice under the same conditions, the rank of the resistance to microbial deterioration among the sample oil agents was the same as that of the method of the present invention. However, the reproducibility of PH, viable cell count, etc. was not so good.

Effect of the Invention It was confirmed that the evaluation method of the present invention has a good correlation with the conventional method.

On the other hand, the method of the present invention has the following advantages over the conventional method.

It is possible to evaluate in a short time.

Good reproducibility.

Since it is possible to quantify the resistance to microbial deterioration of oil solutions, it is possible to compare oil solutions even if they are not simultaneously compared.

Therefore, the use of the method of the present invention helps to develop an oil agent having good resistance to microbial deterioration.

Further, in practical use of the oil agent, it becomes easy to measure the oil agent having good resistance to microbial deterioration, so that the working environment is improved, the resource interval is extended and the amount of the replenished oil agent is reduced, and the resource cost is further reduced. It will be reflected in the reduction.

Claims (1)

[Claims] 1. A stock solution or diluting solution of a water-soluble cutting oil whose microbial deterioration resistance is to be evaluated is mixed with a spoilage solution or a bacterial dispersion of a water-soluble cutting oil in various ratios, and the mixture is placed under constant conditions. , Collecting a part of the mixed solution, culturing in a nutrient medium,
A method for evaluating the microbial deterioration resistance of a water-soluble oil agent for metalworking by confirming the presence or absence of viable bacteria in each mixed solution and knowing the minimum concentration of the oil agent capable of inhibiting the growth of bacteria.