WO2017158894A1

WO2017158894A1 - Lubricant oil

Info

Publication number: WO2017158894A1
Application number: PCT/JP2016/079171
Authority: WO
Inventors: 和枝栗原; 雅史水上; 白澤　大輔
Original assignee: 国立大学法人東北大学
Priority date: 2016-03-16
Filing date: 2016-09-30
Publication date: 2017-09-21
Also published as: JPWO2017158894A1

Abstract

[Problem] To provide a lubricant oil that is able to achieve low frictional properties in fluid lubrication and boundary lubrication without using any additives. [Solution] The present invention has a normalized peak intensity ratio, as obtained by a resonant shear measuring method, of at least 0.4 at a surface-to-surface distance not less than 20 nm, and of at most 0.2 under a load of greater than 0 mN and at most 5 mN. The present invention preferably includes: a low-viscosity base oil having a bulk viscosity not higher than a prescribed value; and a high-viscosity base oil having a bulk viscosity at least 10 times as high as that of the low-viscosity base oil. Furthermore, the low-viscosity base oil preferably has a bulk viscosity of 100 mPa·s or lower. The high-viscosity base oil preferably has a viscosity in boundary lubrication lower than that of the low-viscosity base oil.

Description

Lubricant

The present invention relates to a lubricating oil.

The energy produced by automobiles is lost as heat in various parts. In particular, it is said that the loss due to the friction of the engine and the drive part ranges from about 20% to 30% of the total loss. In addition to automobiles, about 70% of machine performance deterioration and damage are caused by the surface and the contact portion, and are highly related to friction. Therefore, it is considered that the friction and wear control can greatly contribute to the improvement of the energy efficiency of the mechanical system and the improvement of the quality and life of the product.

Friction can be broadly classified into fluid lubrication and boundary lubrication according to load and speed, and coexistence of low friction in each region is a major issue. Low friction in fluid lubrication requires a reduction in fluid resistance, that is, a low viscosity lubricant. However, the lubricating oil having a low viscosity in the fluid lubrication region is easily discharged from the boundary portion with a load, and molecules remaining in the boundary portion without being discharged are also structured. For this reason, in the boundary lubrication region, an increase in the viscosity of the lubricating oil, an increase in friction due to collision between the surfaces, and seizure are caused.

In order to prevent such an increase in friction and seizure, conventionally, an additive that adsorbs to the surface or an additive that induces a reaction on the surface has been used to reduce friction in the boundary lubrication region (for example, Non-Patent Documents 1 to 4).

Note that a resonance shear measurement method has been developed by the present inventors as a method for measuring the characteristics of a liquid in a minute space (see, for example, Non-Patent Document 5). In this resonance shear measurement method, the distance between the surfaces (liquid thickness) can be continuously controlled at the nanometer level from the micrometer order to the contact, and the liquid characteristics are determined from the intensity and frequency of the resonance peak. It has the characteristics that it can be evaluated with high sensitivity, and the characteristics of the liquid between the surfaces can be quantitatively evaluated by physical model analysis. Specifically, by changing the thickness of the liquid sandwiched between two smooth solid surfaces on the order of nanometers, the upper and lower surfaces vibrate relatively in parallel, and the shear response is measured by the resonance method. The characteristic change of the sandwiched liquid can be evaluated from the measured resonance frequency and response intensity. The present inventors use this resonance shear measurement method to measure the viscosity parameters of four phenyl ether-based lubricants from the fluid lubrication region to the boundary lubrication region (for example, see Non-Patent Document 6). ).

In the method of adding an additive or the like to the low-viscosity lubricating oil as described in Non-Patent Documents 1 to 4, there is a problem that the formulation is complicated when the number of blending components is large. Moreover, since the reactive additive does not easily react under low temperature conditions, there is a problem that the friction reducing effect becomes insufficient. Moreover, although a phosphorus type additive and a sulfur type additive may be used as an additive, there also existed the subject that it was necessary to reduce phosphorus and sulfur from a viewpoint of environmental impact. From such a problem, there is a demand for a lubricating oil that keeps the viscosity of the lubricating oil in the fluid lubrication region low and suppresses an increase in viscosity in the boundary lubrication region without using an additive or the like as much as possible.

Therefore, an object of the present invention is to provide a lubricating oil that can realize low friction in fluid lubrication and boundary lubrication without using an additive.

In the non-patent document 6, the present inventors described monoalkyl diphenyl ether (MADE; monoalkydiphenyl ether), dialkyl diphenyl ether (DADE), m-phenoxyphenoxy m-biphenyl (m-4P2E; m-phenoxyphenoxy m-biphenyl). , M-bis (m-phenoxyphenoxy) benzene (m-5P4E; m-bis (m-phenoxyphenoxy) benzene) was evaluated for viscosity parameters from the fluid lubrication region to the boundary lubrication region. As shown in FIG. 1, the viscosity parameter in the fluid lubrication region was found to be m-5P4E> m-4P2E> DADE> MADE, which was found to be in good agreement with the bulk viscosity. In addition, the viscosity parameter in the boundary lubrication region was MADE> DADE> m-4P2E> m-5P4E, and it was found that the viscosity was reversed. The present inventors have repeated trial and error based on the results shown in FIG.

That is, in the lubricating oil according to the first aspect of the present invention, the normalized peak intensity ratio obtained by the resonance shear measurement method is 0.4 or more when the surface-to-surface distance is 20 nm or more, and the load is greater than 0 mN and 5 mN or less. It is characterized by being 0.2 or less.

The lubricating oil according to the first aspect of the present invention has a low viscosity in the fluid lubrication region where the distance between the surfaces is 10 nm or more and a small friction force in the boundary lubrication region where the load is 5 mN or less. For this reason, low friction can be realized in fluid lubrication and boundary lubrication.

The lubricating oil according to the second aspect of the present invention is characterized in that it contains two base oils having different bulk viscosities by 10 times or more. In particular, the lubricating oil according to the second aspect of the present invention comprises a low-viscosity base oil having a bulk viscosity of a predetermined value or less, and a high-viscosity base oil having a bulk viscosity 10 times or more higher than the low-viscosity base oil. It is preferable to include. The lubricating oil according to the second aspect of the present invention includes a first base oil and a second base oil having different viscosity characteristics, and the second base oil has a viscosity in fluid lubrication of the first base oil. It is preferably higher than the base oil and lower in viscosity at the boundary lubrication than the first base oil.

As shown in FIG. 1, among two base oils having different bulk viscosities by 10 times or more, a base oil having a high bulk viscosity (high viscosity base oil or second base oil) has a bulk viscosity of Compared with a low base oil (low viscosity base oil or first base oil), the viscosity parameter in the boundary lubrication region is low. That is, the high-viscosity base oil has a lower viscosity at the boundary lubrication than the low-viscosity base oil. The lubricating oil according to the second aspect of the present invention includes such two base oils, exhibits the viscosity performance of the base oil having a low bulk viscosity in the fluid lubrication region, and the bulk viscosity in the boundary lubrication region. By exhibiting the high viscosity performance of the base oil, it is possible to achieve low friction in fluid lubrication and boundary lubrication. Moreover, it is not necessary to use an additive by this, and prescription becomes complicated, and it can prevent applying a load to an environment using a phosphorus type additive and a sulfur type additive.

In the lubricating oil according to the second aspect of the present invention, the low viscosity base oil preferably has a bulk viscosity of 100 mPa · s or less. In this case, the viscosity can be lowered in a balanced manner by fluid lubrication and boundary lubrication. The lubricating oil according to the second aspect of the present invention may have the characteristics of the lubricating oil according to the first aspect of the present invention.

According to the present invention, it is possible to provide a lubricating oil that can realize low friction in fluid lubrication and boundary lubrication without using an additive.

It is a graph which shows the distance dependence between mica of lubricating oil viscosity regarding this invention (cited from nonpatent literature 6). It is a graph which shows the resonance curve which expanded the vertical axis | shaft of (a) resonance shear measurement of the phenyl ether type lubricating oil of embodiment of this invention, and (b) (a). FIG. 2 shows (a) the relationship between the distance between surfaces on the air separation (AS) side and the normalized peak intensity ratio, and (b) the load on the mica contact (MC) side and the standard obtained based on the resonance curve shown in FIG. It is a graph which shows the relationship with a conversion peak intensity ratio. It is a graph which shows the relationship between the load calculated | required based on the resonance curve shown in FIG. 2, and a frictional force. Based on the resonance curve obtained by the resonance shear measurement of the PAO lubricant according to the embodiment of the present invention, (a) the distance between the surfaces on the air separation (AS) side and the normalized peak intensity ratio; (B) is a graph showing the relationship between the load on the mica contact (MC) side and the normalized peak intensity ratio. It is a graph which shows the relationship between the load and frictional force which were calculated | required based on the resonance curve obtained by the resonance shear measurement of the PAO type | system | group lubricating oil of embodiment of this invention.

2 to 5 show the lubricating oil according to the embodiment of the present invention.
Hereinafter, in order to evaluate the viscosity characteristics of the lubricating oil sandwiched between the surfaces in the fluid lubrication region and the boundary lubrication region, the resonance shear measurement is performed by continuously controlling the distance between the surfaces from micrometer to several nanometers. It was. At the same time, for each distance between the surfaces, the interaction force (load) acting between the surfaces by the lubricating oil was measured using the spring alone method. For the measurement of the resonance shear and the load between the surfaces, a resonance shear measurement device “RSM-1” (manufactured by Advance Riko Co., Ltd.), which the present inventors were involved in development, was used.

[Viscosity characteristics of phenyl ether lubricant]
As a lubricating oil according to an embodiment of the present invention, a lubricating oil obtained by adding 1.3 wt% of a base oil m-5P4E having a bulk viscosity of 1196 mPa · s to a base oil MADE having a bulk viscosity of 12 mPa · s (hereinafter referred to as “m -5P4E added MADE ").

Fig. 2 shows resonance curves for various distances between surfaces and loads obtained by resonance shear measurement. In addition, the distance between the surfaces on the air separation (AS) side and the normalized peak intensity ratio (the distance between the surfaces or the peak intensity of the resonance frequency at each load / the maximum peak intensity obtained based on the results of FIG. 3) and the relationship between the load on the mica contact (MC) side and the normalized peak intensity ratio are shown in FIGS. 3 (a) and 3 (b), respectively. For comparison, the results of only the base oil MADE and the results of the base oil m-5P4E are also shown in FIGS. 3 (a) and 3 (b). Here, the AS-side relationship shown in FIG. 3A indicates the characteristics of the fluid lubrication region, and the normalized peak intensity ratio decreases as the viscosity increases. The relationship on the MC side shown in FIG. 3B shows the characteristics of the boundary lubrication region, and the normalized peak intensity ratio increases as the frictional force increases.

As shown in FIG. 3 (a), on the AS side, the m-5P4E-added MADE has a normalized peak intensity ratio of 0.2 or more and a surface-to-surface distance of 15 It was confirmed that the normalized peak intensity ratio was 0.4 or more when it was larger than nm. The m-5P4E-added MADE has slightly lower strength than the MADE, but has properties close to that of the MADE, and is confirmed to have a low viscosity. It was also confirmed that when the surface-to-surface distance was smaller than about 10 nm, the strength decreased rapidly as in MADE. As shown in Fig. 3 (b), on the MC side, m-5P4E-added MADE is saturated at a load of 1 to 2 mN and strength of 0.1 to 0.17, similar to m-5P4E. It was confirmed that the frictional force was low. Furthermore, the thickness of the liquid film is 0.4 nm ± 0.2 nm for the base oil MADE and 1.3 nm ± 0.2 nm for the base oil m-5P4E, whereas the MADE with m-5P4E added is 1.4 nm ± 0.3 nm, It is considered that the base oil m-5P4E is concentrated in a space of several nanometers.

FIG. 4 shows the relationship between the load and the frictional force calculated based on the analysis method of Non-Patent Document 7 from the results of FIG. For comparison, the results of only base oil MADE and the results of base oil m-5P4E are also shown in FIG. As shown in FIG. 4, m-5P4E-added MADE was saturated at a load of 1 μmN or less and a frictional force of about 0.2 μmN, as with m-5P4E, and had lower friction than MADE. Moreover, this result showed the same tendency as the result obtained by the normalized strength ratio. In this way, m-5P4E-added MADE has the characteristics of MADE with a low bulk viscosity in the fluid lubrication region and the property of m-5P4E with a high bulk viscosity in the boundary lubrication region, and is low in both lubrication conditions. It was confirmed that friction was obtained.

From the above results, it can be said that m-5P4E-added MADE is highly lubricated by fluid lubrication and boundary lubrication, and can achieve low friction. In addition, m-5P4E-added MADE does not use additives such as phosphorus-based additives and sulfur-based additives, and can prevent complicated prescriptions and environmental burdens.

[Viscosity characteristics of PAO (Poly-α-orefin) lubricant]
As a lubricating oil according to an embodiment of the present invention, a lubricating oil obtained by adding 1.3 wt% of a base oil PAO40 having a bulk viscosity of 730 mPa · s to a base oil PAO4 having a bulk viscosity of 25 mPa · s (hereinafter referred to as “1.3 wt%”). PAO40-added PAO4 ") was prepared.

FIG. 5A shows the relationship between the AS-side surface distance and the normalized peak intensity ratio, and the relationship between the MC side load and the normalized peak intensity ratio, obtained based on the result of the resonance shear measurement. And shown in (b). For comparison, the results of only base oil PAO4 and the results of base oil PAO40 are also shown in FIGS. 5 (a) and 5 (b).

As shown in FIG. 5 (a), on the AS side, the 1.3 wt% PAO40-added PAO4 has a normalized peak intensity ratio of 0.3 or more when the surface-to-surface distance is greater than about 10 mm, and the surface-to-surface distance is It was confirmed that the normalized peak intensity ratio was 0.5 or more when the thickness was larger than 20 nm. 1.3 wt% PAO40-added PAO4 has characteristics close to those of PAO4 and was confirmed to have a low viscosity. It was also confirmed that when the surface-to-surface distance was smaller than about 10 nm, the strength decreased rapidly as in PAO4. As shown in Fig. 5 (b), on the MC side, the strength of 1.3 wt% PAO40-added PAO4 increases more slowly than PAO4 as the load increases, and the normalized peak strength is around 7 mN. The ratio was about 0.17, and it was confirmed that the strength was small compared to PAO4 when the load was lower than 10 mm, and the frictional force was low.

FIG. 6 shows the relationship between the load and the frictional force calculated from the result of FIG. For comparison, the results of only base oil PAO4 and the results of base oil PAO40 are also shown in FIG. As shown in FIG. 6, the frictional force of PAO4 with 1.3 wt% PAO40 increased more gently than PAO4 as the load increased, and it was lower than that of PAO4 when the load was lower than 10 mN. It was. Moreover, this result showed the same tendency as the result obtained by the normalized strength ratio. Thus, 1.3 wt% PAO40-added PAO4 has the same viscosity characteristics as PAO4 with low bulk viscosity in the fluid lubrication region, and due to the effect of PAO40 with high bulk viscosity at a load lower than 10 mm in the boundary lubrication region It was confirmed that a friction reducing effect was obtained.

From the above results, it can be said that 1.3 wt% PAO40-added PAO4 is highly lubricated by fluid lubrication and boundary lubrication with a load lower than 10 μm, and low friction can be realized. In addition, 1.3 wt% PAO40-added PAO4 does not use additives such as phosphorus additives or sulfur additives, and can prevent complicated prescriptions and environmental burdens. .

As described above, the lubricating oil according to the embodiment of the present invention can obtain the effect of reducing the frictional force in the boundary lubrication region while keeping the bulk viscosity in the fluid lubrication region low. Further, the lubricating oil according to the embodiment of the present invention does not require an additive, and a friction reducing effect can be obtained only by mixing the base oil, so that the environmental load is small. Moreover, it is possible to prevent the occurrence of unexpected phenomena such as a decrease in lubrication performance due to side reactions such as association of additives and an increase in wear.

Claims

Lubrication characterized in that the normalized peak intensity ratio obtained by the resonance shear measurement method is 0.4 or more when the distance between the surfaces is 20 nm or more and 0.2 or less when the load is greater than 0 mN and 5 mN or less. oil.
2. Lubricating oil according to claim 1, comprising two base oils having different bulk viscosities by a factor of 10 or more.
The lubricating oil according to claim 1, comprising a low-viscosity base oil having a bulk viscosity of not more than a predetermined value and a high-viscosity base oil having a bulk viscosity 10 times or more higher than the low-viscosity base oil. .
The lubricating oil according to claim 3, wherein the low-viscosity base oil has a bulk viscosity of 100 mPa · s or less.
The lubricating oil according to claim 3 or 4, wherein the high-viscosity base oil has a lower viscosity at boundary lubrication than the low-viscosity base oil.
Including a first base oil and a second base oil having different viscosity characteristics;
The lubricating oil according to claim 1, wherein the second base oil has a higher viscosity in fluid lubrication than the first base oil and a lower viscosity in boundary lubrication than the first base oil.