Method for quantifying foreign oil mixed in rolling oil

Abstract

To solve the problem that it is difficult to determine the amount of foreign oil mixed in the used rolling oil by measuring the saponification value or by analysis using IR or GC and to provide a new method for quantifying the amount of foreign oil contained in a used rolling oil even when the foreign oil and the rolling oil have an equivalent saponification value or the same compositions.SOLUTION: The method for quantifying foreign oil mixed in rolling oil includes the steps of: performing thermogravimetric measurement of a used rolling oil (or an extracted oil in the case of an emulsion type); and calculating the ratio of the foreign oil based on a TG curve of the oil component in the used rolling oil and TG curves of a fresh rolling oil and each foreign oil expected to be mixed, the TG curves having been obtained in advance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for quantifying the rate of mixing of different oils, such as hydraulic oil, into rolling oil using a thermogravimetric measuring device. [Background technology]

[0002] As rolling oil is used, it may become contaminated with other oils, such as hydraulic oil, due to equipment trouble or aging. Such liquids will be referred to as "used liquid" below. If other oils become mixed into rolling oil, it will have a negative effect on lubrication, and in the case of rolling oils that are mixed with water and used as emulsions, there is also concern about the impact on emulsification.

[0003] A decrease in lubricity can lead to defects in the shape of the rolled material, such as burn marks, chattering marks, and edge elongation. It also increases the likelihood of metal powder being generated, which can cause contamination of the rolled material and the area around the rolling mill. Contamination around the rolling mill can cause dripping onto the steel plate, resulting in spot-like stains and unevenness known as mottling. Heat treatment and surface treatment are required to remove these defects and contamination, which consumes extra effort and energy.

[0004] When emulsion emulsification is poor, the amount of plate-out increases due to the enlargement of particle size and a decrease in ESI (emulsion stability index). In this case, excessive lubrication can occur, causing slippage between the rolled material and the rolls, making rolling impossible. When slippage occurs between the rolled material and the rolls, tension and thickness become unstable, and chattering can occur. Furthermore, poor emulsification can cause the oil film on the rolled material to become uneven, increasing the number of oil pits and resulting in surface defects.

[0005] If the amount of foreign oil mixed into the coolant becomes too large, the above problems are more likely to occur, so as a countermeasure, it is necessary to partially dump out and replace the coolant. In view of the above-mentioned problems, the present invention aims to grasp the amount of foreign oil mixed into the coolant and to appropriately manage the properties of the rolling oil.

[0006] Conventional methods for analyzing foreign oils mixed into rolling oil include a method for measuring the saponification value, a method using IR (infrared absorption spectroscopy) analysis (Non-Patent Document 1), and a method using GC (gas chromatography) analysis.

[0007] While rolling oil is primarily composed of fats and synthetic esters, other oils such as hydraulic oil are primarily composed of mineral oils. Therefore, rolling oil often has a higher saponification value than other oils, and the amount of mixed-in oil can be determined from the rate of decrease in the saponification value of the used fluid. However, in recent years, the use of flame-retardant hydraulic oils has increased as a countermeasure against the Fire Service Act. Because its constituent components are esters, the saponification value of rolling oils with esters as the main component is almost the same as that of other oils, making it difficult to determine the mixed-in rate from the saponification value. Furthermore, while the saponification value is generally determined by neutralization titration, it is highly dependent on individual skill and can vary greatly depending on the individual.

[0008] When comparing the IR peaks of rolling oil and other oils, most of the absorption bands of the other oils are hydrocarbon absorptions, so many of the absorption peaks of the other oils are included in the absorption spectrum of the rolling oil. Therefore, it is difficult to derive the amount of contamination from a specific peak derived from the other oil. Therefore, it is common to determine the contamination rate of other oils by focusing on one absorption band of the rolling oil and comparing the absorption intensity of the rolling oil alone, which has been measured in advance, with the absorption intensity of the used liquid. However, the amount of other oils contaminated with rolling oil in actual work sites is usually small, and analysis based on the absorption intensity ratio is prone to error.

[0009] Similarly, in gas chromatography analysis, the peaks of the mineral oil components in the rolling oil and the peaks of the other oils may overlap, making it impossible to determine the contamination rate of the other oils. [Prior art documents] [Non-patent literature]

[0010] Japan analyst, Vol.20(1971), P.813-818 Summary of the Invention [Problem to be solved by the invention]

[0011] When the main components of rolling oil and other oils are both esters, their saponification values ​​are similar, making it difficult to determine the contamination rate of other oils using the saponification value. Furthermore, when the main components of rolling oil and other oils are both mineral oils and the IR and GC peaks overlap, it is difficult to determine the contamination rate of other oils using IR or GC. Therefore, the present invention aims to provide a new method for quantifying the amount of other oils mixed in without measuring the saponification value or using IR or GC. [Means for solving the problem]

[0012] In the present invention, we focused on the difference in thermogravimetric change between rolling oil and other oils. When measuring thermogravimetric change, the more foreign oils that evaporate at lower temperatures than rolling oil are mixed in, the lower the temperature at which the used liquid evaporates. On the other hand, the more foreign oils that evaporate at higher temperatures than rolling oil are mixed in, the higher the temperature at which the used liquid containing the foreign oil mixed in the rolling oil evaporates. Therefore, we investigated whether it would be possible to derive the contamination rate of foreign oils contained in rolling oil by measuring the thermogravimetric change of rolling oil, other oils, and these used liquids using a thermogravimetric measuring device, and this led to the development of the present invention described below.

[0013] 1. The present invention is a method for quantifying foreign oils mixed into rolling oil, in which thermogravimetric measurement is performed on the used rolling oil (or the extracted oil in the case of emulsion types), and the proportion of foreign oil is calculated from the thermogravimetric change (TG) curves of the new rolling oil, which has been previously subjected to thermogravimetric measurement, and the thermogravimetric change (TG) curve of the foreign oil that is expected to be mixed in, and the thermogravimetric change (TG) curve of the oil content of the used oil.

[0014] 2. The thermogravimetric measurement in the present invention is a method for quantifying foreign oils mixed into rolling oil according to Item 1, in which the weights of the oil components in all samples of the used liquid, new rolling oil, and foreign oils that are expected to be mixed in are unified and the weights are 5 mg to 20 mg.

[0015] 3. The thermogravimetric measurement in the present invention is a method for quantifying foreign oils mixed into the rolling oil according to item 1 or 2, in which the temperature rise rate is 2° C. / min. to 20° C. / min.

[0016] 4. The thermogravimetric measurement in the present invention is a method for quantifying foreign oils mixed into rolling oil according to item 1 or 2, in which the measurement atmosphere is an inert gas.

[0017] 5. The thermogravimetric measurement in the present invention is a method for quantifying foreign oils mixed into rolling oil according to item 1 or 2, in which the atmospheric gas flow rate is less than 1 L / min and is constant during measurement. [Effects of the Invention]

[0018] In the present invention, the series of steps for determining the contamination rate of foreign oils only uses a thermogravimetric measuring device and is not affected by an individual's analytical skills. Furthermore, unlike the measurement of saponification value, there is no need to use dangerous reagents such as hydrochloric acid (HCl) or potassium hydroxide (KOH), which are highly toxic substances, and the analysis can be carried out safely. Thermogravimetry requires only a small amount of sample for analysis. By controlling rolling oil using the method of the present invention, signs of trouble such as lubrication abnormalities and poor emulsification can be detected early, enabling stable operation. [Brief explanation of the drawings]

[0019] [Figure 1] This figure shows the TG curves of three types of oil: rolling oil A, hydraulic oil A, and a 90:10 mixture of rolling oil A and hydraulic oil A. [Figure 2] FIG. 1 shows infrared absorption spectra of three types of oil: rolling oil A, hydraulic oil A, and a mixture of rolling oil A and hydraulic oil A at a ratio of 99:1. DETAILED DESCRIPTION OF THE INVENTION

[0020] Specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0021] Thermogravimetry in the present invention is performed with sample weights ranging from several mg to several tens of mg. Since typical thermal behavior exhibits sample weight dependence, the greater the sample amount, the more significant the weight loss, but the greater the variance. Furthermore, the rate of loss per unit time is lower than when there is less sample, and the peak temperature shifts to the higher temperature side. Since this sample weight dependence is more pronounced for samples with poorer thermal conductivity, it is desirable to standardize the sample weight. A sample weight of 5 mg to 20 mg is preferable, and considering experimental reproducibility and resolution, a sample weight of approximately 10 mg is desirable.

[0022] In the thermogravimetric measurement of the present invention, a substance that does not undergo thermal changes such as melting, transition, or decomposition within the measurement range is used as a reference substance. Alumina powder is generally used, but since it may absorb moisture, in such cases it is necessary to heat it in advance to the upper limit of the measurement temperature range.

[0023] In the thermogravimetry of this invention, sample containers made of materials such as Al, SiO2, Pt, Al2O3, and SUS are used. Al cups melt and are not suitable for temperatures above 500°C, and caution is required when using Pt cups as they may act as a catalyst. However, differences in the thermal conductivity of the container material can reduce peak sensitivity, so Al or Pt, which have good thermal conductivity, are desirable if the conditions are met.

[0024] In the present invention, thermogravimetry is performed up to a temperature above the temperature at which the oil completely evaporates. In order to understand the behavior of the thermogravimetric changes of the rolling oil, the different oils, and the working oil, it is necessary to completely evaporate each oil.

[0025] In the present invention, the thermogravimetric measurement is performed at a heating rate of 2°C / min to 20°C / min. As the heating rate increases, the amount of change per unit time increases, reducing the resolution and shifting the overall behavior of the measurement to higher temperatures. Therefore, a slower heating rate is desirable to increase the accuracy of the analysis. In the thermogravimetric measurement of the present invention, an inert gas is used as the measurement atmosphere. The use of an inert gas prevents oxidation and combustion during temperature rise, and allows the evaporation behavior of the oil itself to be confirmed.

[0026] In the thermogravimetric measurement of the present invention, the flow rate of the atmospheric gas is less than 1 L / min, preferably 100 to 500 ml / min, and the flow rate is constant during the measurement. The temperature at which weight loss due to evaporation or decomposition of the sample begins is affected by the gas flow rate, so as the flow rate increases, the starting temperature shifts to a lower temperature.

[0027] The method for determining the contamination rate of foreign oils in the present invention is carried out by the following steps. 1. Thermogravimetric measurements are carried out on new rolling oil and different types of oil. 2. Conduct thermogravimetric measurements of the oil content of the liquid used. (In the case of emulsion-type rolling oil, the water content is first removed using an evaporator, and then the oil is extracted.) 3. If the proportion of rolling oil components in the liquid used is x% and the proportion of mixed-in foreign oil is y%, then x+y=100. If the thermal weight change rate of the rolling oil at a given temperature is A%, the thermal weight change rate of a different oil is B%, and the thermal weight change rate of the working liquid is C%, then A×x / 100+B×y / 100=C. From these two simultaneous equations, x and y can be found, i.e. the contamination rate of foreign oils.

[0028] The arbitrary temperature to be compared in 3 is between the temperature after the oil begins to evaporate at the highest temperature and the temperature at which the oil completely evaporates at the lowest temperature. If the analysis is performed at any other temperature range, for example, at a temperature before the oil begins to evaporate at the highest temperature, the oil content will be 0%, and an accurate value cannot be obtained. Also, if the analysis is performed at a temperature higher than the temperature at which the oil completely evaporates at the lowest temperature, the oil content will be 0%, and an accurate value cannot be obtained.

[0029] When two or more different types of oil are considered, the number of variables is increased accordingly, and the equation can be derived by setting up three or more simultaneous equations by comparing two or more types of any given temperature. [Example]

[0030] The present invention will be specifically explained below based on examples, but the present invention is not limited to these examples in any way.

[0031] In this example, a plurality of hydraulic oils, etc. were treated as different oils, and samples were mixed with new rolling oil at arbitrary ratios to simulate the liquids in use. Weight changes were measured using a thermogravimetric analyzer, and the ratios of the different oils were calculated from the obtained data, and it was confirmed whether they were consistent with the adjusted ratios.

[0032] Table 1 shows the compositions (%) of the rolling oil, hydraulic oil, and additives used in this example.

[0033] [Table 1]

[0034] The hydraulic oils and additives used in this example are as follows: Hydraulic oil A: Daphne Mistorbe 460N manufactured by Idemitsu Kosan Co., Ltd. Hydraulic Oil B: Daphne Hydraulic Fluid 32 manufactured by Idemitsu Kosan Co., Ltd. Additive A: Chemtura Co. / Cie BRYTON C-300

[0035] In this example, a differential thermal and thermogravimetric simultaneous analyzer, TG-DTA8122 manufactured by Rigaku Corporation, was used.

[0036] [Example 1] In this example, 10 mg of sample was placed in a Pt cup, and the reference material was Al2O3. Thermogravimetry was performed by increasing the temperature from room temperature to 700°C at a rate of 2°C / min in an N2 gas atmosphere. The thermogravimetric changes of rolling oil A and hydraulic oil A, and of a 90:10 mixture of rolling oil A and hydraulic oil A, were used to calculate the blend ratio determined by the method of the present invention. The results of the thermogravimetric measurements are shown in Figure 1. The thermogravimetric changes (TG) of each oil at 290°C and 300°C are shown in Table 2.

[0037] [Table 2]

[0038] The ratio of rolling oil A to hydraulic oil A is set to x% and the ratio of hydraulic oil A to y% in oil adjusted to a ratio of rolling oil A: hydraulic oil A = 90:10. From TG at 290℃, (-97.29)x / 100+(-8.78)y / 100=-88.32 When solving the simultaneous equations x+y=100, we get x=89.9 and y=10.1. Also, from TG at 300℃, (-97.48)x+(-10.62)y=-88.89 When solving the simultaneous equations x+y=100, we get x=90.1 and y=9.9. Two arbitrary temperatures, 290°C and 300°C, were selected, but the results were similar to those of the adjusted oil mixture ratio at both temperatures, indicating that the results are independent of temperature.

[0039] Below, the thermogravimetric change rate at 300°C was examined as an example of an arbitrary temperature. The oils shown in Table 3 below were used to prepare the oils used in the analysis of the present invention.

[0040] [Table 3]

[0041] In Table 3, the numerical values ​​for each composition are all weight ratios. Rolling oil, different oils (hydraulic oil, additives), and each oil prepared with the composition shown in Table 3 were analyzed using a thermogravimetric analyzer, and the TG (%) at 300°C is shown in Table 4. Because sample (10) uses three types of oil, it was necessary to compare it at two temperature ranges, and the TG at 290°C is summarized in Table 5, separate from Table 4.

[0042] [Table 4]

[0043] [Table 5]

[0044] The contents of each sample adjusted in Table 2, derived using the thermogravimetric change results in Tables 4 and 5, are shown in Table 6.

[0045] [Table 6]

[0046] The results for samples (1) to (4) show that it is possible to analyze foreign oils mixed into rolling oil even at a few percent, but the error becomes large when the value is measured after the decimal point. The results for samples (5) and (6) show that analysis is possible even when a large amount of foreign oil is mixed into the rolling oil. The results of sample (7) show that the different oil mixed into the rolling oil is not limited to hydraulic oil A, and other oils can also be used. The results for samples (8) and (9) show that other rolling oils are also applicable, not just rolling oil A.

[0047] When there was only one type of different oil, the error was less than 0.5%, but the results for sample (10) showed that when multiple different types of oil were mixed, the error was a few percent, and the accuracy decreased.

[0048] Additive A left a residue after thermogravimetry, with the amount of residue being approximately 20%. This result was consistent with the measurement of the ash content of Additive A in a nitrogen atmosphere. The ash content was measured by weighing a sample into a crucible and burning it in an electric furnace, after which the weight of the ash remaining was measured. Since the results of the thermogravimetry were similar to the results of other analyses, the reliability of the thermogravimetry results was increased. Furthermore, the results of sample (11) show that the present invention can be applied to oils that leave residues.

[0049] Table 7 shows the TG values ​​at 300°C when the heating rate was changed.

[0050] [Table 7]

[0051] The ratio of rolling oil A to hydraulic oil A when the temperature was increased at 5°C / min., as derived from Table 7, was 99.0% rolling oil A and 1.0% hydraulic oil A, which is consistent with the mixture ratio. Furthermore, when the temperature was raised at 10°C / min, the ratio of rolling oil A to hydraulic oil A was 98.9% rolling oil A and 1.1% hydraulic oil A, which matched the mixing ratio. Therefore, it can be seen that the present invention is not limited to a temperature rise rate of 2° C. / min. and can be carried out at other temperature rise rates.

[0052] [Comparative Example 1] The saponification values ​​of rolling oil A, rolling oil B, hydraulic oil A, hydraulic oil B, samples (2), (7) to (9) are shown in Table 8.

[0053] [Table 8]

[0054] The mixing ratios of samples (2), (7) to (9) derived from Table 8 are as shown in Table 9.

[0055] [Table 9]

[0056] For samples (2), (7), and (8), the results were almost the same as the adjusted ratio. However, for samples like sample (9), where the saponification value is the same between rolling oil and hydraulic oil, the results were not consistent with the adjusted ratio. On the other hand, as shown in Table 6, thermogravimetry was able to analyze samples with the same saponification value, such as sample (9), demonstrating the usefulness of the present invention.

[0057] Comparative Example 2 The ratio of the ester peak to the hydrocarbon peak (1720-1780 cm) obtained from the IR results of rolling oil A, rolling oil B, hydraulic oil A, hydraulic oil B, samples (2), (7) to (9) -1 and 1400-1500cm -1 The ratio of (Ratio of) is as shown in Table 10. As an example of the results of IR analysis, the IR of rolling oil A, hydraulic oil A, and sample (2) are shown in Figure 2.

[0058] [Table 10]

[0059] The mixing ratios of samples (2), (7) to (9) derived from Table 10 are as shown in Table 11.

[0060] [Table 11]

[0061] The results obtained in Table 11 had a larger error from the adjusted ratio than the results obtained in Tables 6 and 9. In particular, the results did not match the adjusted ratio when using rolling oil and hydraulic oil, which have almost the same composition, such as sample (9). On the other hand, as shown in Table 6, thermogravimetry was able to analyze samples with similar compositions, such as sample (9), demonstrating the usefulness of the present invention.

[0062] The results of Tables 6, 9, and 11 are summarized, and the mixing ratios derived from thermogravimetry, saponification value, and IR are shown in Table 12.

[0063] [Table 12]

[0064] In Table 12, when comparing the results obtained by each measurement method for the blend ratio of each sample, the results obtained by thermogravimetry were closest to the blend ratio for all samples. Sample (9) was a blend of oils with similar saponification values ​​and similar components, and the results obtained by saponification value and IR for sample (9) were less accurate than the other samples. On the other hand, the results obtained by thermogravimetry were not affected by such conditions. [Industrial Applicability]

[0065] According to the present invention, even in cases where it is difficult to measure the amount of foreign oil mixed in the rolling oil, it is possible to grasp the amount of foreign oil mixed in the rolling oil by using a thermogravimetric measuring device. Proper management of rolling oil leads to early detection of signs of trouble such as lubrication abnormalities and poor emulsification, enabling stable operation.

Claims

1. This method quantifies the amount of foreign oil mixed into rolling oil by performing thermogravimetry on the rolling oil used (or the extracted oil in the case of emulsion types), and then calculating the proportion of foreign oil from the thermogravimetry (TG) curves of the new rolling oil, which has been thermogravimetry measured in advance, and the thermogravimetry (TG) curve of the foreign oil that is expected to be mixed in, as well as the thermogravimetry (TG) curve of the oil content of the used oil.

2. The method for quantifying foreign oils mixed in rolling oil according to claim 1, characterized in that the sample weights of the used liquid, the new rolling oil liquid, and the foreign oils expected to be mixed in the thermogravimetric measurement are unified, and their weights are 5 mg to 20 mg.

3. 3. The method for quantifying foreign oils mixed in rolling oil according to claim 1, wherein the temperature rise rate in the thermogravimetric measurement is 2°C / min to 20°C / min.

4. 3. The method for quantifying foreign oils mixed in rolling oil according to claim 1, wherein the thermogravimetric measurement is carried out in an inert gas atmosphere.

5. 3. The method for quantifying foreign oils mixed in rolling oil according to claim 1, wherein the flow rate of the atmospheric gas for thermogravimetry is less than 1 L / min. and is a constant flow rate during measurement.

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