Compositions – Electrolytes for electrical devices
Patent
1988-04-11
1990-11-06
Chaudhuri, Olik
Compositions
Electrolytes for electrical devices
252 56R, C10M10532
Patent
active
049684523
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to a lubricating oil composition and more particularly to a lubricating oil composition which is suitably used for lubrication of parts including a wet brake or a wet clutch of automatic transmissions and tractors.
BACKGROUND TECHNOLOGY
Lubricating oil for wet brake or wet clutch which is used in lubrication of parts including a wet brake or a wet clutch is required to be low in low temperature viscosity in view of starting performance. In general, the low temperature viscosity of lubricating oil can be easily decreased by decreasing the viscosity of the total base oil. In this case, however, the viscosity of the lubricating oil is too low at high temperatures, thereby producing a problem that the lubrication performance is decreased and the lubricating oil is unsuitable for practical use.
Therefore a method of compounding viscosity index improvers such as polymers to the low viscosity base oil has been widely used. This method, however, fails to solve the above problem because such polymers undergo viscosity reduction under shearing.
The first object of the present invention is to provide a base oil which holds a constant viscosity at high temperatures as one of the characteristics thereof and which is low in low temperature viscosity. It is, of course, required for the base oil to be excellent in oxidation stability and also in rubber swelling properties (seal rubber compatibility).
The second object of the present invention is to provide a lubricating oil composition in which friction characteristics for wet brakes or wet clutches are increased by the base oil itself.
SUMMARY OF THE INVENTION
The present invention provides a lubricating oil composition comprising 97 to 60% by weight of mineral oil and 3 to 40% by weight of polyester, wherein the mineral oil has a kinematic viscosity at 100.degree. C. of 2 to 50 centistokes (cSt), a pour point (as determined by JIS K-2269) of -5.degree. to -30.degree. C, a viscosity index (as determined by JIS K-2283) of not less than 80 and % C.sub.A (content of aromatic hydrocarbon) of not more than 3.
The lubricating oil composition of the present invention has a suitable viscosity at high temperatures and further is low in low temperature viscosity.
Further, the lubricating oil composition of the present invention is excellent in friction characteristics.
In addition, the lubricating oil composition of the present invention is excellent in oxidation stability and also in seal rubber compatibility.
DETAILED DESCRIPTION
Mineral oil as the major component of the lubricating oil composition of the present invention has a kinematic viscosity at 100.degree. C. of 2 to 50 cSt, preferably 5 to 30 cSt, a pour point of -5.degree. to -30.degree. C, preferably -7.5.degree. to -30.degree. C., a viscosity index of not less than 80, preferably not less than 85, and % C.sub.A of not more than 3, preferably not more than 1, if the above physical values are not within the above defined ranges, the desired lubricating oil composition cannot be obtained.
From a viewpoint of oxidation stability, mineral oil having a sulfur content of not more than 0.01% by weight, especially not more than 0.001% by weight is preferred.
Mineral oil having the properties as described above can be obtained by refining to a high extent a distillate (having a boiling point under atmospheric pressure of 250.degree. to 450.degree. C.) which has been obtained by distilling a paraffin base crude oil or an intermediate base crude oil.
This distillate means an oil obtained either by atmospheric distillation of crude oil or by vacuum distillation of residual oil resulting from atmospheric distillation of crude oil. A method of high refining is not critical, and any of the methods (1) to (5) as described below can be employed.
(1) The distillate is subjected to hydrogenation treatment, or alternatively, after hydrogenation treatment, the distillate is subjected to alkali distillation or sulfuric acid washing (treating).
(2) The distillate is subjected to sol
REFERENCES:
patent: 3640858 (1972-02-01), Harr
patent: 3649570 (1972-03-01), Boehringer
patent: 3962071 (1976-06-01), Itoh et al.
*USP 3,962,071 Claims of Priority of 48-55765 (60-2771).
**GB 2134538 Claims the Priority of 58-6657 (59-133297).
Chaudhuri Olik
Hunter, Jr. James M.
Idemitsu Kosan Company Limited
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