JP2002372492A - Method for determining water in oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily and rapidly determining rustproof oil that is applied to a metal material, metal products, and metal components for giving rustproofness and/or lubrication properties, and/or rustproof oil that is applied to the lubricant by a small amount of sample, and/or water in the lubricant. SOLUTION: An infrared transmission window material whose solubility to 100 g water at 20 deg.C is 1 g or less is used to measured rustproof oil and/or its infrared absorption spectrum, thus determining water from the ratio of the absorption intensity (peak are or peak height) of O-H bond appearing at a wavenumber of 3700-2800 cm<-1> , or the absorption intensity (peak area or peak height) of C-H bond in hydrocarbon appearing at a wavenumber of 3200-2800 cm<-1> , and the absorption intensity (peak area or a peak height) of O-H bond appearing at a wavenumber of 3700-2800 cm<-1> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining moisture in oil, and more particularly to a method for applying rust-preventive oil and / or lubricity to metal materials, metal products and metal parts to impart rust-preventive properties and / or lubricity.
Or, it relates to a method for determining the moisture content of lubricating oil.

[0002]

2. Description of the Related Art When a rust-preventive oil and / or a lubricating oil exerts a function on a metal material, a metal product and a metal part, moisture contained in the oil may affect the oil. Especially in Japan, June to August is a hot and humid season, and the moisture in the air migrates into the oil, increasing the moisture in the oil and deteriorating functions such as rust prevention and lubricity. Therefore, it is very important to determine the water content in the oil.

[0003] Conventionally, as a general method of quantifying water,
Known literature (for example, “Analytical Chemistry Handbook” edited by the Japan Society for Analytical Chemistry)
As shown in (1991, Maruzen, p.111), the sample is vacuum dried, heat dried, air dried, etc., and the method of quantification by mass reduction is used. Mass spectrometry (mass spectrometry), such as a method of quantifying the increase in the mass of the absorbent by absorption into the absorbent, volumetric analysis, such as the Karl Fischer method, which measures the amount of water by titration, for specific samples Is a method of quantifying from the absorbance using a reaction that forms a color by reacting with water, a method of quantifying from the amount of gas generated using a reaction between water and carbide or calcium hydride, gas chromatography Quantitative methods by chromatography and the like are known.

[0004] In particular, the Karl Fischer method, which is one of the volumetric analysis methods, is a very important moisture determination method in practical use.
Also called aquametry, it has been widely used as a method for determining water in oil. The Karl Fischer method utilizes the reaction of water with Karl Fischer reagents containing iodine and sulfur dioxide in pyridine and methanol. This method has good sensitivity and accuracy and is widely used, but requires a sample amount of 0.5 g or more. However, metallic materials, the coating amount of the rust-preventive oil and / or lubricating oil to the product and part is several tens of mg / m ² ~ Number g / m ² approximately,
To obtain the required amount of sample by Karl Fischer method,
Samples must be collected from an area of 1 m ² or more.
In addition, when a solvent is used, the solvent may be affected by moisture in the solvent, and it is difficult to separate the solvent from the sample (moisture in the sample). Therefore, the solvent cannot be used for sampling.
In addition, the Karl Fischer reagent is unstable and must be standardized using a standard reagent each time it is used. Further, since the reagent reacts with water, the measurement must be performed in a moisture-proof system.

On the other hand, JP-A-9-96398 discloses that
A system that analyzes and manages components of a lubricating oil using an infrared spectrum has been proposed.

[0006]

The rust-preventive oil and / or lubricating oil is applied to a metal material, a metal product and a metal part to exhibit a function. Therefore, it is necessary to measure the moisture in the applied state. However, since the amount of application is very small, it is difficult to recover a large amount without using a solvent that may mix water, and a method that can quantify water with a small number of samples is desired.

In a method for measuring an infrared absorption spectrum,
The sample amount can be determined in a very small amount of several μl (corresponding to several mg). Infrared spectroscopy is a method of irradiating a sample with infrared light and measuring the absorption due to the vibration that causes a change in dipole efficiency among the molecular vibrations. It is widely used for analysis of aromatic substituents, analysis of high molecular compounds, and analysis of some inorganic compounds. In the measurement of the infrared absorption spectrum of a liquid or a liquid sample by the transmission method, the measurement is usually performed by sandwiching two infrared transmitting materials (window materials) to form a thin film or adjusting the optical path length by interposing a spacer. The optical path length at the time, that is, the thickness of the sample is 10 to 10 when the sample is measured without dilution with a solvent or the like.
In the case of measuring absorption having a large extinction coefficient such as a C—H bond of a hydrocarbon at about 100 μm, it is about 10 to 30 μm. Since the luminous flux of the infrared ray at the time of measuring the infrared absorption spectrum is about 10 to 20 mmφ, the sample amount necessary for quantifying the water content in the oil from the peak intensity is 1 to 10
It is a very small amount of μl, and if it is such a small amount, rust preventive oil and / or lubricating oil applied to metal materials, products and parts can be easily collected without using a solvent. However, the conventional window material used for measuring the infrared absorption spectrum has a problem that it is easily affected by moisture, and thus infrared spectroscopy is hardly used for water.

The lubricating oil management system disclosed in Japanese Patent Application Laid-Open No. 9-96398 is a system for analyzing and managing components of lubricating oil using an infrared spectrum, and it is said that moisture can also be analyzed. However, it actually detects the O—H bond of a phenolic antioxidant, which is one of the lubricating oil components, and no example of detecting water is shown. Did not mention. Then, the present inventors performed a supplementary test of Japanese Patent Application Laid-Open No. 9-96398 using a conventional window material, and as a result, in many cases, it was not possible to quantify moisture.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a simple and quick method for removing moisture in a rust-preventive oil and / or a lubricating oil applied to a metal material, a metal product and a metal part. It is an object of the present invention to provide a method for quantifying moisture that can be quantitatively determined.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention uses the following means to achieve the above object. (1) The infrared absorption spectrum of the oil was measured and the wave number was 3700.
A method for determining the water content in oil, comprising determining the water content in the oil from the absorption intensity of the O—H bond appearing at ２2800 cm ⁻¹ . (2) The infrared absorption spectrum of the oil was measured and the wave number was 3200.
The water in the oil is quantified from the ratio of the absorption intensity of the C—H bond of the hydrocarbon appearing at 2800 cm ⁻¹ and the absorption intensity of the O—H bond appearing at the wave number of 3700 to 2800 cm ^−1. A method for determining water in oil. (3) The method for determining water in oil according to the above (1) or (2), wherein the absorption intensity is a peak area or a peak height in the wave number range. (4) The oil is filled in a measurement cell having an infrared transmission window material having a solubility of 1 g or less in 100 g of water at 20 ° C. and the infrared absorption spectrum is measured.
The method for determining water in oil according to any one of (3). (5) The water content in oil according to (4) above, wherein the infrared transmission window material is one or two selected from calcium fluoride, barium fluoride, lithium fluoride, magnesium fluoride, sapphire or silver chloride. Method. (6) The method according to any one of the above (1) to (5), wherein the oil is a rust-preventive oil and / or a lubricating oil.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION C—H bonds of hydrocarbons include stretching vibrations observed at wave numbers of 3200 to 2800 cm ⁻¹ and bending vibrations observed at wave numbers of 1460 and 1380 cm ⁻¹ .
The O—H bond of water also has stretching vibration observed at a wave number of 3700 to 2800 cm ⁻¹ and bending vibration observed at 1700 to 1500 cm ⁻¹ , both of which have higher strength. The absorption of the OH bond has a wave number of 3700 to 2800 cm.
^-1 and C-H bond absorption are preferably measured at wave numbers of 3200 to 2800 cm ^-1 .

Next, as for the material of the window material used for the measurement of the infrared absorption spectrum, the following characteristics were found as a result of intensive studies on the infrared transmission characteristics and mechanical strength. (1) High transmittance of infrared rays. (2) It is hardly affected by moisture. (3) Excellent mechanical strength.

The transmission of infrared radiation is determined by the Fresnel's formula (r =
{(N ₂ −n ₁ ) / (n ₂ + n ₁ )} ² ; r is the reflection loss, n ₁ is the refractive index of the medium 1, and n ₂ is the refractive index of the medium 2, and the medium is incident on the window material from the atmosphere. 1 is the atmosphere, and the medium 2 is a window material), and as long as there is no absorption, the smaller the refractive index, the higher the transmittance. Since a parallel plate has two interfaces of an entrance surface and an exit surface, even if light passes through one plate only once, reflection loss occurs on two surfaces. Actually, the infrared light applied to the sample through the window material passes through the sample surface and passes through the window material again, so that the energy substantially reaching the detector is the fourth power of the single surface transmittance. That is, the energy reaching the detector is about 80% at a refractive index of 1.6.
The refractive index decreases to about 75% at a refractive index of 1.7. In addition, bubbles may be mixed into the liquid film at the time of sample preparation. To confirm this, it is desirable that the liquid film has a high visible light transmittance. Silicon and germanium have very low solubility in water, but have a high refractive index and thus low infrared transmittance, and do not transmit visible light, so that the state of the sample cannot be confirmed.

As the infrared transmitting window material, potassium bromide (KBr), potassium chloride (KCl) and sodium chloride (NaCl) are generally used. These have a wide range of infrared transmission wavelengths, a high refractive index due to a small refractive index, and are transparent to visible light, but all are deliquescent and devitrified or impair the surface shape in the presence of water. Invite the problem. Therefore, the solubility of the window material in water is preferably 1 g or less with respect to 100 g of water at 20 ° C., and if it exceeds 1 g, the contact surface is easily dissolved in one use (several minutes) and the surface shape is impaired. .

Further, since the optical path length is adjusted by sandwiching the liquid between the two window members, the mechanical strength, particularly the hardness, of the window members is also important. Thallium chloride (TlCl), thallium bromide (TlB)
r), thallium chloride / thallium bromide (TlCl / TlBr: KR
S-6), thallium bromide / iodide (TlBr / TlI:
KRS-5) has low solubility in water and is often used for measurement of a sample containing water. However, KRS-5) is so soft that it is easily scratched and cannot be used repeatedly. Also, TlCl,
TlBr, KRS-6, KRS-5, zinc selenide (Z
nSe) is not preferable in use because the material is harmful.

Based on the results of the above-mentioned tests and investigations, as a result of intensive studies on window materials suitable for measuring the infrared absorption spectrum of rust-preventive oil and / or lubricating oil containing water, water 10 ° C. at 20 ° C.
The solubility to 0 g is 1 g or less, and the wave number is 4000 to 15.
Window material having a high infrared transmittance of 00 cm ^-1 , particularly CaF ₂ ,
BaF ₂ , LiF, MgF ₂ , sapphire, or AgC
1, more preferably, using CaF ₂ or BaF ₂ , it was confirmed that an infrared absorption spectrum capable of accurately quantifying the moisture in the rust preventive oil and / or the lubricating oil was obtained.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of a method for setting a sample for measuring an infrared absorption spectrum. The sample 1 is thinned by being sandwiched between two infrared transmitting window members 2, and irradiated with an infrared light beam 3 to measure a transmitted light beam 4. It is preferable to use the spacer 5 having a thickness of 10 to 30 μm. However, the sample may be thinned just by sandwiching it between two windows without using a spacer.

FIG. 2 is an infrared absorption spectrum of the rust-preventive oil measured using a 15 μm aluminum foil as a spacer. The absorption 6 of the O—H bond derived from water contained in the rust-preventive oil and the rust-preventive oil are shown. Absorption 7 of oil-derived C—H bonds is observed.
There are a vertical splitting method and a valley-baseline method for peak splitting of absorption of OH bond and absorption of C—H bond derived from rust preventive oil, and any of these methods can be used. Since is wide, it is preferable to use a valley-crossing baseline method in which valleys of peaks are connected to form a baseline as shown in FIG. When the optical path length (the thickness of the sample) is made constant by using the spacer, the water content can be quantified using the calibration curve from the intensity (peak area or peak height) of the absorption 6 of the OH bond. When the optical path length is not constant, water can be quantified from the intensity (peak area or peak height) ratio of the absorption 6 of the O—H bond and the absorption 7 of the C—H bond. As peak intensity, peak area, peak top height (peak height)
May be used, but it is preferable to use the peak area because the accuracy is high.

[0019]

(Example 1) The infrared absorption spectrum of a rust preventive oil to which water was added was measured in a cell having a fixed optical path length of 25 μm using two sheets of BaF ₂ as a window material. FIG. 3 shows the result of measuring the peak area corresponding to the absorption 6 of the bond by absorbance. There was a good linear relationship between the water and the area of the absorption peak of the O—H bond, and the water could be quantified from the absorption intensity of the infrared absorption spectrum. The window material after the measurement (Ba
Inspection of F ₂ ) revealed that the window material was not damaged at all.

(Comparative Example 1) Measurement was performed using the same sample and cell as in Example 1 using two KBr windows.
After the measurement, the surface of the KBr of the window material became cloudy, and a dent caused by the elution of KBr into water was observed in a portion in contact with the sample,
It could not be used repeatedly.

Example 2 Using two sheets of CaF ₂ as a window material, measuring the infrared absorption spectrum of a rust-preventive oil to which water was added without using a spacer and fixing the optical path length. The ratio of the peak area (absorbance) corresponding to the O—H bond absorption 6 and the peak area (absorbance) corresponding to the C—H bond absorption 7 in Example 2 was calculated. FIG. 4 shows moisture and OH / C-
The relationship of H peak area ratio is shown. There was also a good linear relationship between the water and the OH / CH peak area ratio, and the water could be quantified also from the peak intensity (area) ratio of the infrared absorption spectrum. The CaF ₂ window material after the measurement was not damaged at all and could be used repeatedly.

(Example 3) Water is added to a rust-preventive lubricating oil having lubricating properties and applied to a steel pipe, and the drawing force at the time of drawing (the index of lubricity, the smaller the drawing force, the smaller the drawing force). Lubricity). FIG. 5 shows the relationship between the water content and the pull-out force. When the moisture increases, the force required for drawing increases, resulting in processing defects. This processing failure is caused by a pulling force of 4
Since water is generated at 1000 N or more, it is necessary to control the moisture in the rust preventive lubricating oil to 1.5 mass% or less. Therefore, a steel pipe was coated with a rust-preventive lubricating oil and exposed for 10 days. About 10 μl of the rust-preventive lubricating oil was sampled from the surface of the steel pipe as needed, and the water content was quantified using the calibration curve of FIG. FIG. 6 shows the transition of the water content in the rust-preventive lubricating oil applied to the steel pipe surface. Moisture after exposure for 10 days was 0.87% by mass, which was a level that could sufficiently maintain lubricity. The quantification of water in a trace amount of sample in such a coated state is difficult by the Karl Fischer method, and the present invention is effective.

[0023]

According to the present invention, the water content in the rust-preventive oil and / or the lubricating oil can be determined accurately, simply, and in comparison with the Karl Fischer method, which requires the standardization of the reagent with the standard reagent each time it is used. Not only can it be performed quickly, but also a small amount of moisture in the rust-preventive oil and / or lubricating oil applied to metal materials, metal products and metal parts, which has been difficult by the Karl Fischer method or the method disclosed in JP-A-9-96398. Can be easily and accurately quantified. Therefore, according to the present invention, it is possible to appropriately manage the function of the rust-preventive oil and / or the lubricating oil for the metal material, the metal product, and the metal component, which has been difficult in the past.

[Brief description of the drawings]

FIG. 1 is a schematic view of a sample setting method for measuring an infrared absorption spectrum.

FIG. 2 is a diagram showing an infrared absorption spectrum of a rust preventive oil measured using a 15 μm aluminum foil as a spacer.

FIG. 3 is a diagram showing the relationship between the moisture and the area of the absorption peak of the O—H bond when the optical path length is fixed.

FIG. 4 shows the relationship between water and O- when measured without changing the optical path length.
It is a figure which shows the relationship of H / CH peak area ratio.

FIG. 5 is a diagram showing a relationship between moisture and a drawing force.

FIG. 6 is a diagram showing a change in moisture in a rust-preventive lubricating oil on the surface of a steel pipe.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Sample 2 Infrared transmitting window material 3 Infrared light beam 4 Transmitted infrared light beam 5 Spacer 6 Absorption of O—H bond derived from moisture 7 Absorption of C—H bond derived from rust preventive oil

Continued on the front page (72) Inventor Shinya Sakamoto 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works (72) Inventor Hirosaku Shioda 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu F-term in the ironworks (reference) 2G057 AA01 AB02 AB06 AC01 BA01 BB10 2G059 AA01 BB04 CC09 EE01 EE12 FF04 HH01 HH06 LL02 MM12

Claims (6)

[Claims] An oil absorption spectrum of oil is measured, and the water content of the oil is determined from the absorption intensity of an O—H bond appearing at a wave number of 3700 to 2800 cm ^−1. Method. 2. The infrared absorption spectrum of the oil is measured, and the absorption intensity of the C—H bond of the hydrocarbon appearing at a wave number of 3200 to 2800 cm ⁻¹ and the O intensity appearing at a wave number of 3700 to 2800 cm ⁻¹ are measured.
-A method for determining the water content in oil, wherein the water content in the oil is determined from the ratio of the absorption intensities of -H bonds. 3. The method according to claim 1, wherein the absorption intensity is a peak area or a peak height in the wave number range. 4. The solubility in 100 g of water at 20 ° C. is 1
The method for quantifying water in oil according to any one of claims 1 to 3, wherein the oil is filled in a measurement cell having an infrared transmission window material of not more than g and the infrared absorption spectrum is measured. 5. The water in oil according to claim 4, wherein the infrared transmitting window material is one or two kinds selected from calcium fluoride, barium fluoride, lithium fluoride, magnesium fluoride, sapphire and silver chloride. Quantitation method. 6. The method according to claim 1, wherein the oil is a rust preventive oil and / or a lubricating oil.