JPH06102177A - Measuring method for saponification value, acid value and fatty acid iron of oil - Google Patents

Abstract

PURPOSE:To obtain a method capable of easily and shortly measuring the saponification value, acid value and fatty acid iron in oil. CONSTITUTION:Measured are the infrared absorption spectrum in between 1600 to 3200 kayser of measured oil, saponification value from the ratio of absorption intensity between characteristic absorption of hydrocarbon and that of carbonyl base, acid value from the fraction of absorption intensity of the characteristic absorption of carbonyl base in fatty acid in that of the carbonyl base, or acid value from the ratio of absorption intensity between the characteristic absorption of hydrocarbon and that of fatty acid and thus the simultaneous quick analysis of saponification value and acid value becomes possible. Also, from the difference in the acid value between before and after acid decomposition of the measured oil, the measurement of the fatty acid becomes possible. Owing to the drastic shortening of analysis, the management of rolling oil and the like becomes easy, and the soil of the steel plate and plating, poor quality and others decrease.

Description

Detailed Description of the Invention

[0001]

This invention relates to oils (eg cold rolling oils,
Bearing oil, machining oil, etc.) and a method for measuring fatty acid iron in oil.

[0002]

2. Description of the Related Art As a conventional method for measuring the saponification value / acid value of oil, an indicator titration method is used to determine the number of milligrams of potassium hydroxide that saponifies 1 g of a sample or the number of milligrams of potassium hydroxide that neutralizes it. Was there. However, the titration method largely depends on the skill of the individual, and the measurement value may vary depending on the person. Further, the saponification value and the acid value must be titrated by different methods, which is disadvantageous in that it takes time to work. As a method for measuring the saponification value / acid value with an infrared spectrophotometer, JP-A-59-219598 discloses a method in which the components of lubricating oil are separated by a liquid chromatograph and the wave number is set to 1740 cm ^-1 by an infrared spectroscopic detector. It is disclosed that the characteristic absorption of the carbonyl group is fixed, the amount of each separated component is determined, and the saponification value / acid value is determined by calculation from these amounts.
Since it is not necessary to obtain only the saponification value and the acid value, it takes time and effort to separate them by liquid chromatography. Moreover, since the amount of oil sample must be kept constant, it cannot be said to be a simple measurement method.

[0003]

The present invention is directed to the saponification value of oil
This is a method of simultaneously and simply and accurately measuring the acid value using an infrared spectrophotometer. The deterioration state of the lubricating oil and the estimation of the performance of the lubricating oil can be grasped from the fluctuation of the saponification value / acid value of the lubricating oil and the amount of fatty acid iron produced, but the saponification value / acid value can be measured by the individual difference according to the present invention. It is possible to carry out quickly without any information, and to know information for oil management quickly and accurately. Further, by shortening the measurement time, it becomes possible to detect and deal with the trouble of the lubricating oil such as mixing of other kinds of oil quickly.

[0004]

The gist of the present invention is to measure the infrared absorption of the oil to be measured at 1600 to 3200 cm ^-1 ,
The saponification number is quantified from the absorbance ratio between the characteristic absorption of hydrocarbons and the characteristic absorption of carbonyl groups, and the acid value is quantified from the ratio of the characteristic absorption of carbonyl groups of fatty acids to the characteristic absorption of carbonyl groups, or the characteristic absorption of hydrocarbons. A method for measuring the saponification value / acid value of oil, which comprises quantifying the acid value from the absorbance ratio of the characteristic absorption of fatty acids, and the infrared absorption of 1600 to 3200 cm ^-1 before and after acid decomposition of the measured oil. The acid value is determined by measuring the ratio of the characteristic absorption of the carbonyl group of the fatty acid to the characteristic absorption of the carbonyl group, or the acid value is determined by the absorbance ratio of the characteristic absorption of the hydrocarbon and the characteristic absorption of the fatty acid. fatty acid iron measurement method in oil which comprises determining the fatty acid iron from the difference in acid value after acid decomposition, i.e. the infrared absorption 1600～3200Cm ^-1 in infrared spectrophotometer measures, hydrocarbons and Ca By utilizing the characteristic absorption of Boniru group is to quantify the saponification value-acid value.

The saponification value means the number of milligrams of potassium hydroxide required for saponifying 1 g of the sample, and the acid value means the number of milligrams of potassium hydroxide required for neutralizing the free fatty acid contained in 1 g of the sample. . Conventionally, the saponification value / acid value was measured by the amount of potassium hydroxide consumed as defined by the indicator titration method, but in the present invention, functional groups such as esters and fatty acids that react with potassium hydroxide are used. (Carbonyl group) is measured from the infrared absorbance,
The saponification value and acid value are indirectly determined by measuring the sample amount from the absorbance of hydrocarbons.

That is, according to the present invention, the saponification value =
The value calculated by (amount of potassium hydroxide consumed) / (amount of sample collected) was calculated from the ratio of absorption intensity of (carbonyl group) / (hydrocarbon), and the acid value was determined by the conventional titration method.
The ratio calculated by (amount of potassium hydroxide consumed by fatty acid) / (amount of sample collected) calculated by (amount of carbonyl group of fatty acid) / (total carbonyl group) or (amount of carbonyl group of fatty acid) ) / (Hydrocarbon) absorption intensity ratio.

The details of the present invention will be described below. Generally, compounds having a carbonyl group such as esters (animals, vegetable oils and fats, synthetic esters, etc.) and fatty acids are commonly used for lubricating oils. Therefore, the infrared absorption spectrum of lubricating oil is 1
When measured in the range of 600 to 3200 cm ^-1 , 2750 to 3100 based on the stretching vibration of CH of hydrocarbon as shown in FIG.
Absorption near cm ^-1 and carbonyl group 1670-180
Absorption near 0 cm ^-1 appears. Of these, hydrocarbon CH
It is known that binding uptake can be used to measure oil content.

That is, since the absorption strength of the CH bond of the hydrocarbon corresponds to the oil content, the value of the area ratio of the absorbance of the carbonyl group or the peak height ratio when this is set to 1 has a certain quantity of oil. The saponification number can be quantified by correlating with the amount of the functional group capable of reacting with potassium hydroxide and measuring the value of this ratio. Since this measurement method is an internal standard method, even if the oil content changes, the CH bond absorption and the carbonyl group absorption increase / decrease at the same rate, so the ratio value does not change and the measurement is not affected by the sample concentration. It can be called a law.

Regarding the acid value, a method of quantitatively determining how much of the absorption of the carbonyl group of the fatty acid is absorbed in the carbonyl group is determined from the ratio of the total absorption intensity of the carbonyl group of the fatty acid and the absorption of the carbonyl group. Then, there is a method of quantifying from the amount of fatty acid capable of reacting with potassium hydroxide having a fixed amount of oil, that is, the ratio of the carbonyl group of the fatty acid and the absorption intensity of hydrocarbon.

[0010] near the carbonyl group of the fatty acid is 1710 cm ^-1, the carbonyl group of the ester is having the peak of each absorbance near 1740 cm ^-1, it is difficult separation because the absorption wavelengths are close. If the separation is possible, either the area ratio or the peak height ratio may be used, but if it is not possible, the absorption intensity of the free fatty acid is obtained from the peak height ratio to calculate the acid value.

A specific measuring method will be described below. First, the oil content in the sample is extracted into a solvent that does not affect the measurement wavelength range, such as carbon tetrachloride or chloroform.
When the sample contains water, the accuracy is improved by dehydrating with a dehydrating agent such as sodium sulfate, anhydrous zinc chloride, diphosphorus pentoxide, and anhydrous copper (II) sulfate. The solvent from which the oil is extracted is put in, for example, a square cell, a test tube type cell, a cylindrical cell, a flow cell, a micro cell, etc.
The absorbance in the wavelength range of ⁰ to 3200 cm ^-1 is measured. An appropriate baseline wavenumber is selected in advance for the absorption measurement to be used. The ratio of the integrated intensity of the absorption spectrum of the CH bond and 1670～1800Cm ^-1 vicinity of the carbonyl group in the vicinity of 2750～3100Cm ^-1, or by measuring the ratio of the peak height, to quantify the saponification number from separately prepared calibration curve.

[0012] For the acid value, the absorption of the ester in the vicinity absorption and 1740 cm ^-1 of the fatty acids in the vicinity of 1712 cm ^-1, the area intensity or peak height intensity is measured, among the absorption of the carbonyl group from separately prepared calibration curve Quantify what percentage of this is due to free fatty acids. This value represents what percentage of the saponification value obtained from the infrared spectrum corresponds to the neutralization of fatty acid, that is, the acid value. Therefore, the acid value can be quantified by multiplying the saponification value obtained by the above method by the proportion of this fatty acid.
Or, with CH bond near 2750-3100 cm ^-1 and 1
The ratio of the area intensity to the absorption of fatty acids near 712 cm ⁻¹ or the ratio of the peak height is measured, and the acid value is quantified from a separately prepared calibration curve.

Further, fatty acid iron can also be measured by this acid value determination method. In the lubricating oil used for cold rolling, etc., oil and iron often react to produce fatty acid iron,
By acid decomposition, fatty acid iron becomes a free fatty acid, so that the absorbance of the carbonyl group of the fatty acid increases and the acid value increases.
Fatty acid iron is quantified by calculation from this increase compared with the acid value before acid decomposition.

[0014]

【Example】

(Example 1) 2 ml of the emulsion-state coolant used for cold rolling of steel was sampled, dehydrated with sodium sulfate, and then solvent-extracted into 20 ml of carbon tetrachloride. This was placed in a square cell and measured by an infrared spectrophotometer, and the oil content concentration in the coolant and the saponification value / acid value were simultaneously determined. For the saponification value, the area ratio was measured, and for the acid value, it was difficult to separate the ester and the fatty acid, so the peak height ratio was measured, and the saponification value calibration curve in FIG. 3 and the acid value calibration curve in FIG. 4 were used for quantification. The results of pairing the obtained saponification value and acid value with the values obtained by the conventional titration method are shown in FIG. Although the oil content concentration in the coolant fluctuates with the day, the saponification value and acid value could be measured stably without being affected by this method, and the transition of the lubricating oil state could be observed.

Example 2 Lubricating oil used for cold rolling of steel was sampled, oil content was extracted with carbon tetrachloride, and measured with an infrared spectrophotometer to quantify the acid value. Another sample was taken from the same lubricating oil, and the fatty acid iron produced during use was decomposed to return it to fatty acid, dissolved in carbon tetrachloride and measured with an infrared spectrophotometer to quantify the acid value. . Subtract the acid value before acid decomposition from the acid value obtained in the acid decomposed sample,
The amount of fatty acid iron was calculated from the difference in acid value. Regarding the measurement of the acid value at the time of acid decomposition, the absorption of fatty acid is relatively large as shown in FIG. 5, and the fatty acid peak and the ester peak can be divided using a data processing device. The acid value was quantified by calculating the ratio of carbonyl groups of fatty acids to the area of the absorption intensity of all carbonyl groups. When the amount of fatty acid iron in the lubricating oil was measured for one month, the content of fatty acid iron gradually increased to nearly 2%, so new oil was added to keep the lubricating oil in a normal state, We were able to prevent problems such as steel plate stains and plating defects due to oil deterioration.

(Example 3) When the saponification value and acid value of the cold rolling oil were measured for 3 weeks, the measured values suddenly dropped by 10% or more in the 3rd week. It was possible to detect the mixing of oil quickly and replace the lubricating oil to prevent problems such as seizure and slippage of the steel plate. The change in the infrared absorption spectrum at this time is shown in FIG.

(Example 4) In an online test for newly adopting A oil having a high fatty acid concentration as a lubricating oil used for cold rolling, a low fatty acid concentration remaining in the oil tank used until then was used. Oil A was added to oil B and used for rolling. The rapid measurement of saponification value and acid value by this method allows you to understand how much B oil remains in the lubricating oil under test within 30 minutes. Also, from the change of acid value and the result of rolling speed test, the fatty acid concentration It was possible to confirm how well the lubricating oil plateed out and the rolling speed could be increased without trouble. Further, in the case of the same type of oil, the higher the saponification value is, the higher the oil film strength is. Therefore, the measured saponification value is one of the indexes for judging the performance of the lubricating oil.

Example 5 In order to examine the relationship between the fatty acid concentration and the plate-out property of rolling oil, the amount of fatty acid added to rolling oil was gradually increased, and the acid value and the amount of adhering oil were examined. At that time, the acid value was measured by measuring the hydrocarbon by the absorbance ratio of the characteristic absorption of hydrocarbon and the characteristic absorption of fatty acid. As a result, only the acid value could be obtained more quickly by a simple calculation method.

[0019]

INDUSTRIAL APPLICABILITY According to the present invention, when measuring saponification value / acid value and fatty acid iron used for determining deterioration and performance of lubricating oil, it is possible to avoid variations in the measured values due to the personal technique, which tends to occur in the titration method. In addition, it was possible to obtain effects such as shortening of measurement time and improvement of workability. Further, by doing so, the lubricating oil can be managed in a normal state, troubles due to abnormalities of the lubricating oil can be prevented, and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an infrared absorption spectrum of lubricating oil at 1600 to 3200 cm ⁻¹ .

FIG. 2 is a diagram showing changes in saponification value / acid value of rolled lubricating oil by cold rolling. In the figure, a dotted line is a measured value by a titration method, and a solid line is a calculated value obtained by the method of the present invention.

FIG. 3 is a diagram showing a calibration curve showing the relationship between the area ratio of the absorbance of a carbonyl group and a hydrocarbon obtained from the infrared spectrum of a lubricating oil and the saponification value of the oil obtained by a titration method.

FIG. 4 A calibration curve showing the relationship between the peak height ratio of the total absorbance of carbonyl groups of fatty acids and the carbonyl groups of fatty acids obtained from the infrared spectrum of lubricating oil, and the acid value ratio of the same oil obtained by titration method. FIG.

FIG. 5 is a diagram showing a change in infrared absorption spectrum before acid decomposition and after acid decomposition.

FIG. 6 is a diagram showing a change in infrared absorption spectrum before and after mixing with mechanical oil.

Claims (2)

[Claims] ^1. The infrared absorption of the oil to be measured at 1600 to 3200 cm ⁻¹ is measured, and the saponification value is determined from the absorbance ratio between the characteristic absorption of hydrocarbons and the characteristic absorption of carbonyl groups. A method for measuring the saponification value / acid value of oil, which comprises quantifying the acid value from the ratio of the carbonyl group to the characteristic absorption, or quantifying the acid value from the absorbance ratio between the characteristic absorption of hydrocarbons and the characteristic absorption of fatty acids. 2. 160 before and after acid decomposition of the oil to be measured
The infrared absorption at 0 to 3200 cm ^-1 was measured and the acid value was quantified from the ratio of the characteristic absorption of the carbonyl group of the fatty acid to the characteristic absorption of the carbonyl group, or the acid value was determined from the absorbance ratio of the characteristic absorption of hydrocarbon and the characteristic absorption of fatty acid. A method for measuring fatty acid iron in oil, which comprises quantifying the value and quantifying the amount of fatty acid iron from the difference in acid value before and after acid decomposition.