Chemistry of hydrocarbon compounds – Product blend – e.g. – composition – etc. – or blending process... – Component of indefinite molecular weight greater than 150
Reexamination Certificate
1999-10-27
2001-02-13
Howard, Jacqueline V. (Department: 1764)
Chemistry of hydrocarbon compounds
Product blend, e.g., composition, etc., or blending process...
Component of indefinite molecular weight greater than 150
Reexamination Certificate
active
06187979
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lubricating base oil composition and a process for producing a lubricating base oil composition, the flash point and the low temperature fluidity of which are improved, and more particularly, it relates to a lubricating base oil composition that is useful as a fluid for traction drive, the flash point and the low temperature fluidity of which are improved, and a process for producing the same.
BACKGROUND OF THE INVENTION
A base oil for a traction oil used in a traction type CVT (continuously variable transmission) for automobiles necessarily satisfies contradictory conditions, i.e., a high traction coefficient at high temperature and a low viscosity at low temperature, and at the same time, preferably has a flash point of 150° C. or more from the standpoint of safety on practical use. However, synthetic naphthenic compounds having high traction coefficients at high temperature exhibit poor low temperature fluidity. Thus, the low temperature fluidity must be preferentially realized with indispensable slight decrease of the high temperature traction coefficient. In this case, the molecular weight of the compound must be lowered, and as a result, the flash point is decreased to cause a problem of lacking practical utility. That is, because synthetic naphthenic compounds having high traction coefficients at high temperature have higher viscosity than paraffinic compounds having the same molecular weight, the molecular weight of the naphthenic compounds must be low to satisfy the low temperature fluidity. However, the low molecular weight brings about high volatility of the base oil to lower the flash point. It is generally preferred that the flash point of a lubricating oil for an automobile is maintained at 150° C. or more upon practical use. Therefore, there has been a demand that the flash point of the naphthenic synthetic lubricating oil used as a traction oil for an automobile is improved without decreasing the high temperature traction coefficient, so as to satisfy all the high temperature traction coefficient, the low temperature fluidity, and the flash point.
In order to solve the problem of the naphthenic synthetic lubricating oil, there has been conducted an attempt to add a poly-&agr;-olefin (JP-A-1-149898 and JP-A-3-103495). In these techniques, however, since the viscosity of the poly-&agr;-olefin is too high, the addition amount thereof becomes too large to improve the low temperature fluidity, and as a result, the high temperature traction coefficient is greatly decreased. Furthermore, because the poly-&agr;-olefin has a volatility (boiling point) that is greatly different from the naphthenic synthetic lubricating oil, the content of the poly-&agr;-olefin is increased by volatilization of the light component (synthetic naphthenic compound) to greatly lower the high temperature traction coefficient, which causes a problem of gross slip of a CVT.
SUMMARY OF THE INVENTION
The invention has be developed in view of the situation described above, and an object of the invention is to provide a lubricating base oil composition, the flash point and the low temperature fluidity of which are improved without decrease of the high temperature traction coefficient, and a process for producing the same.
As a result of earnest investigations made by the inventors, it has been found that the object of the invention can be effectively accomplished by adding a small amount of a specific paraffinic synthetic base oil for a lubricating oil to a naphthenic synthetic base oil for a lubricating oil, so as to complete the invention.
The invention relates to:
(1) A lubricating base oil composition comprising (a) from 80 to 98% by weight of a naphtmoenic synthetic lubricating base oil having a flash point of 180° C. or less, and (b) from 2 to 20% by weight of a paraffinic synthetic lubricating base oil having a flash point higher than that of the naphthenic synthetic lubricating base oil;
(2) A lubricating base oil composition described in item (1), wherein the naphthenic synthetic lubricating base oil (a) is a compound containing a ring selected from a cyclohexane ring, a bicycloheptane ring, and a bicyclooctane ring;
(3) A lubricating base oil composition described in item (1) or (2), wherein the naphthenic synthetic lubricating base oil (a) is a compound containing at least two rings selected from a cyclohexane ring, a bicyclo[2.2.1]heptane ring, a bicyclo[3.2.1]octane ring, a bicyclo[2.2.2]octane ring, and a bicyclo[3.3.0]octane ring;
(4) A lubricating base oil composition described in one of items (1) to (3), wherein the paraffinic synthetic lubricating base oil (b) is a poly-&agr;-olefin or an &agr;-olefin copolymer;
(5) A lubricating base oil composition described in one of items (1) to (4), wherein the paraffinic synthetic lubricating base oil (b) has from 16 to 40 carbon atoms;
(6) A lubricating base oil composition described in one of items (1) to (4), wherein the paraffinic synthetic lubricating base oil (b) has from 16 to 26 carbon atoms;
(7) A lubricating base oil composition described in items (4) to (6), wherein the poly-&agr;-olefin is a hydrogenated product of a dimer of 1-decene;
(8) A base lubricating oil composition described in one of items (1) to (7), wherein the lubricating base oil composition is a base oil composition of a fluid for traction drive; and
(9) A process for producing a lubricating base oil composition that is improved in flash point and low temperature fluidity, the process comprising a step of adding, to (a) from 80 to 98% by weight of a naphthenic synthetic lubricating base oil having a flash point of 180° C. or less, (b) from 2 to 20% by weight of a paraffinic synthetic lubricating base oil having a flash point higher than that of the naphthenic synthetic lubricating base oil.
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Ido Motohisa
Yoshida Yukio
Howard Jacqueline V.
Idemitsu Kosan Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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