JPH0823031B2 - Lubricating oil composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lubricating oil composition having good dispersibility of fluorinated graphite.

[Prior Art] Various solid or liquid additives have been conventionally added to lubricating oils such as mineral oils, synthetic oils and animal and vegetable oils for the purpose of improving abrasion resistance and extreme pressure resistance. As an agent (C
The fluorinated graphite represented by F) _n and (C ₂ F) _n is a typical one. Attempts have been made to add fluorinated graphite to lubricating oils to improve lubrication properties such as load seizure prevention and friction reduction.For example, it is not possible to disperse fluorinated graphite in a ball mill using various dispersants. It is known from JP-B-60-56760, JP-B-62-61638, etc., but since the performance of the dispersant used is inferior, the fluorinated graphite in the dispersed liquid undergoes aggregation, sedimentation and separation within a few hours, resulting in fluorination. The fluorinated graphite precipitated due to the shape of the graphite (granular or flake-like) solidified and became clay-like, which sometimes made redispersion impossible.
These tendencies are especially pronounced for non-polar lubricating oils.

[Problems to be Solved by the Invention] Similar to water, fluorinated graphite itself has a property of being extremely hard to adapt to oil. Therefore, there is a problem that the dispersion stability is particularly poor in a non-polar lubricating oil, and the particles immediately aggregate and settle. For example, in order to obtain a practical lubricating oil with improved extreme pressure resistance and abrasion resistance, fluorinated graphite should be blended in an amount of about 0.05 to 2% (% by weight, the same applies hereinafter) to the base oil. However, even if such an amount of fluorinated graphite is mixed with the base oil and mechanically dispersed, the fluorinated graphite is agglomerated and settled just by allowing it to stand for a while.

Various studies have been conducted to improve the dispersion stability of such fluorinated graphite in oil. For example, Japanese Examined Patent Publication No. 60-56760 proposes an oil composition for lubrication in which fluorinated graphite particles are dispersed in a lubricating oil by a dispersant containing at least one propylene oxide group in the molecule. . However, the dispersant containing a propylene oxide group described in the above publication is extremely limited in practical use because it usually has low temperature stability. That is, there is a fatal defect in engine starting at low temperatures and lubrication for refrigerators.

The present invention is to provide a lubricating oil composition in which fluorinated graphite is dispersed in a non-polar base oil in a stable state without agglomerating and settling, and exhibits similar properties even at low temperatures.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and a lubricating oil obtained by dispersing fluorinated graphite in a nonpolar base oil using a dispersant containing an oxybutylene group. A composition is provided.

In order to further stabilize the dispersibility of the present invention, the present invention also provides a lubricating oil composition in which a surfactant containing a carboxyl group is used at the same time as the dispersant.

The dispersant of the present invention contains at least one oxybutylene group in one molecule, preferably three or more oxybutylene groups. As a preferable example, for example,
General formula (I) R ¹ OC ₄ H ₈ O _m H or general formula (II) R ¹ OC
₄ H ₈ O _m XOC ₄ H ₈ O _n OR ² [wherein R ¹ and R ² are the same or different alkyl groups, alkylphenyl groups or acyl groups (preferably each group having 1 to 20 carbon atoms), X Represents an alkylene group (preferably having 1 to 4 carbon atoms), and m and n are each an integer of 1 or more (preferably 3 or more). The dispersant (I) or (II) exhibits favorable performance because it is highly soluble in nonpolar base oil and wettable by fluorinated graphite. These dispersants may be those in which oxyethylene groups or oxypropylene groups are further added in a random or block form. On the other hand, the surfactant used in combination with the above dispersant is a carboxylate-based surfactant. Preferred are those represented by the general formula (III) (RCOO) _p M (wherein R is
Is an alkyl group having 10 or more, preferably 20 or more carbon atoms, p is an integer of 1 to 2, and M is an alkali metal or alkaline earth metal), and a surfactant or lanolin fatty acid salt is preferable for the reason of low temperature stability. . The base oil in the present invention, the fluorinated graphite and the dispersant, if necessary further the amount of the dispersant in the lubricating oil composition consisting of the surfactant is 0.1 to 5
0%, preferably 1.0-20%, and surfactant
0.005 to 10%, preferably 0.01 to 7% is preferable for the reason that the uniformly dispersed state of the lubricating oil composition can be kept stable for a long period of time.

Next, the fluorinated graphite used in the present invention is preferably in the form of particles, and the particle size is not particularly limited, but it is usually in the range of 0.02 to 10 microns in average particle size, and the particle distribution is as uniform as possible. Those are preferable. Further, the amount of fluorinated graphite in the lubricating oil composition according to the present invention is preferably 0.05 to 50%, and if it is less than 0.05%, the lubricating performance is insufficient and 50%.
If the amount is larger, the price is higher than the performance, which is not preferable.

Next, preferable non-polar base oils used in the present invention are, for example, mineral oils such as paraffinic hydrocarbon oils and naphthenic hydrocarbon oils, olefin polymerized oils, alkylated aromatic oils and synthetic hydrocarbon oils. Oils and animal and vegetable oils, etc., which are usually liquids having a viscosity of 5 to 3000 cp (normal temperature).

[Operation] Since the dispersant obtained according to the present invention is well dissolved in a non-polar base oil and has a high wettability to fluorinated graphite, it is excellent in dispersion stability of fluorinated graphite in oil, for example, 80 even if left for a long time such as 6 months or more
Even at a high temperature of ~ 90 ℃, for example -20 ~ 30 ℃
The precipitation of fluorinated graphite is extremely low even at such low temperatures.

Examples Reference Example 1 Dispersant A [Structure: CH ₃ (CH ₂ ) ₁₁ O (C ₄ H ₈ ) ₁₀ H)] 90 g,
10g of fluorinated graphite (grain size 0.2μ) at room temperature in a ball mill
After being uniformly dispersed for a period of time, the dispersion was put into a glass tube having an inner diameter of 27 mm, and the dispersion stability was observed. Dispersion stability is 27 mm inside diameter
The dispersion liquid to be tested was placed in a stoppered test tube of No. 1 up to a height of 150 mm and allowed to stand at room temperature to measure the height of the precipitate.

Reference Example 2 Dispersing agent A (85 g), surfactant (lanolin fatty acid calcium salt) (5 g), and fluorinated graphite (10 g) were dispersed by a ball mill to observe dispersion stability.

Reference Examples 3 to 6 Dispersant B [CH ₃ (CH ₂ ) ₁₇ O (C ₄ H ₈ O) ₂₀ H], Dispersant C The fluorinated graphite was dispersed with a combination of lanolin fatty acid calcium salt surfactant and the dispersion stability was observed.

Reference Comparative Examples 1-2 Dispersant containing propylene oxide group and having good compatibility with machine oil [Structure: R ¹ O (CH ₂ CH ₃ CHO) _n HR: CH ₃ (CH _{2 11} n = 10] 90
Table 1 shows the dispersion stability of g and 10 g of fluorinated graphite together with the results of Reference Examples 1 to 6.

Examples 1 to 6 and Comparative Examples 1 to 2 Reference examples 1 to 6 and reference comparative examples 1 and 2 with 97 g of spindle oil.
3 g of each of the fluorinated graphite dispersion liquids were added and mixed. The dispersion stability, friction coefficient, and ultimate load bearing pressure of the adjusted lubricating oil composition were measured. The lubricating oil composition was transferred to a 100 ml graduated cylinder and stored in a thermostat for 90 days, and the sedimentation layer in the graduated cylinder was observed to determine the dispersion stability.

 The results are shown in Table 2.

 The symbols in the table mean the following.

◯: No sediment is observed.

Δ: A small amount of sediment is observed.

X: Sediment is observed.

Pendulum type oil friction tester (Shinko Seizo Co., Ltd.)
Manufactured by K.K.) and used under standard test conditions. The ultimate load bearing pressure was measured by a step method in which a four-ball friction tester (manufactured by Soda Shinko Seizo Co., Ltd.) was used and a load of 0.5 kg was applied every minute at a spindle speed of 200 rpm.

[Effects of the Invention] The lubricating oil composition of the present invention is excellent in the effect of dispersion stability of fluorinated graphite, and therefore is excellent in extreme pressure and has a low coefficient of friction. Therefore, refrigerating machine oil, various engine oils, spindle oil, dynamo Oil, machine oil, turbine oil, gear oil, cylinder oil, hydraulic oil, etc. or metal working oil etc. are excellent in reducing, reducing and preventing seizure of sliding cotton. Further, it is also effective as an additive such as metal working oil and lubricating oil for fiber treatment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C10M 129: 40) C10N 10:02 10:04 30:04 30:06 40:25 40:30 ( 72) Inventor Hiroshi Kimura 2-30, Futamatagawa, Asahi-ku, Yokohama-shi, Kanagawa (56) References Japanese Patent Publication No. 49-964 (JP, B2) Japanese Patent Publication No. 55-2223 (JP, B2) Japanese Patent Publication No. 60-56760 JP, B2)

Claims (2)

[Claims] 1. A lubricating oil composition comprising fluorinated graphite dispersed in a nonpolar base oil using a dispersant containing an oxybutylene group. 2. The lubricating oil composition according to claim 1, wherein a carboxylate-based surfactant is used together with a dispersant containing an oxybutylene group.