Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Solid hydrocarbon polymer
Reexamination Certificate
2001-09-28
2003-07-08
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Solid hydrocarbon polymer
C585S012000, C585S018000
Reexamination Certificate
active
06589920
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a viscosity modifier for lubricating oil and a lubricating oil composition. More particularly, the invention relates to a viscosity modifier for lubricating oil, by the use of which a lubricating oil composition having excellent low-temperature properties and lubricity at high temperatures can be obtained, and a lubricating oil composition containing the viscosity modifier.
BACKGROUND ART
The viscosity of petroleum products generally varies greatly with temperature change, but the temperature dependence of the viscosity of, for example, a lubricating oil for automobile is desired to be small. On this account, an ethylene/&agr;-olefin copolymer having a viscosity index improving effect has been widely used for the lubricating oil to make the temperature dependence smaller.
The lubricating oil loses flowability at low temperatures because a wax component in the lubricating oil is crystallized and solidified at low temperatures. In order to lower the solidifying temperature, a pour point depressant is contained in the lubricating oil, and the pour point depressant hinders formation of three-dimensional network that is due to crystallization of the wax component in the lubricating oil, and thereby lowers the pour point of the lubricating oil.
Of the low-temperature properties of the lubricating oil containing an ethylene/&agr;-olefin copolymer and a pour point depressant, the viscosity under the conditions of a high shear rate depends upon compatibility of a lubricating oil base with the ethylene/&agr;-olefin copolymer, while the viscosity under the conditions of a low shear rate is greatly influenced by the pour point depressant. It is known that when an ethylene/&agr;-olefin copolymer having a specific composition is used, the effect of the pour point depressant is markedly reduced by the interaction between the copolymer and the pour point depressant (see U.S. Pat. No. 3,697,429 and U.S. Pat. No. 3,551,336).
Therefore, the ethylene/&agr;-olefin copolymer added to the lubricating oil that particularly needs excellent low-temperature properties is desired not only to have an excellent viscosity index improving effect but also not to hinder the function of the pour point depressant.
In order to prevent the interaction between the pour point depressant and the ethylene/&agr;-olefin copolymer, use of an ethylene/&agr;-olefin copolymer obtained by a specific polymerizing apparatus and conditions and having an ununiform composition distribution as a viscosity index improver has been proposed (see Japanese Patent Laid-Open Publication No. 228600/1985). However, any lubricating oil having excellent low-temperature properties independent of the shear rate has not been obtained so far.
Under such circumstances as described above, the present inventor has made earnest studies and has found that by the use of a specific ethylene/&agr;-olefin copolymer, decrease of the effect of the pour point depressant caused by the aforesaid interaction is not brought about, the compatibility with the lubricating oil base at low temperatures is adjusted, and thereby a lubricating oil having excellent low-temperature properties in every shear rate region can be obtained. Based on the finding, the present invention has been accomplished.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a lubricating oil composition that is excellent in low-temperature properties, oxidative stability, lubricity at high temperatures and saving of fuel.
DISCLOSURE OF THE INVENTION
The viscosity modifier for lubricating oil according to the invention comprises an ethylene/&agr;-olefin copolymer which is a copolymer of ethylene and an &agr;-olefin of 3 to 20 carbon atoms and has the following properties:
(1) the ethylene content (E) is in the range of 40 to 77% by weight,
(2) the weight-average molecular weight (Mw) in terms of polystyrene, as measured by GPC, is in the range of 80,000 to 400,000,
(3) Mw/Mn is not more than 2.4,
(4) the melting point (Tm), as measured by DSC, is not higher than 60° C.,
(5) the ethylene content (E, % by weight) and the melting point (Tm, ° C.), as measured by DSC, satisfy the following relation (I):
3.31×
E−
186≧
Tm
(I),
and
(6) the intensity ratio, S&agr;&bgr;/S&agr;&agr;, measured by
13
C-NMR spectrum is not more than 0.5.
The ethylene/&agr;-olefin copolymer is preferably an ethylene/propylene copolymer.
The lubricating oil composition according to the invention is a composition comprising:
(A) a lubricating oil base, and
(B) an ethylene/&agr;-olefin copolymer which is a copolymer of ethylene and an o-olefin of 3 to 20 carbon atoms and has the following properties:
(1) the ethylene content (E) is in the range of 40 to 77% by weight,
(2) the weight-average molecular weight (Mw) in terms of polystyrene, as measured by GPC, is in the range of 80,000 to 400,000,
(3) Mw/Mn is not more than 2.4,
(4) the melting point (Tm), as measured by DSC, is not higher than 60° C.,
(5) the ethylene content (E, % by weight) and the melting point (Tm, ° C.), as measured by DSC, satisfy the following relation (I):
3.31×
E−
186≧
Tm
(I),
and
(6) the intensity ratio, S&agr;&bgr;/S&agr;&agr;, measured by
13
C-NMR spectrum is not more than 0.5;
wherein the ethylene/&agr;-olefin polymer (B) is contained in an amount of 1 to 20% by weight.
Further, the lubricating oil composition according to the invention is a composition comprising the lubricating oil base (A), the ethylene/&agr;-olefin copolymer (B) and a pour point depressant (C), wherein:
the ethylene/&agr;-olefin copolymer (B) is contained in an amount of 0.1 to 5% by weight, and
the pour point depressant (C) is contained in an amount of 0.05 to 5% by weight.
The ethylene/&agr;-olefin copolymer (B) is preferably an ethylene/&agr;-olefin copolymer (B-1) having the following properties:
(1) the ethylene content (E) is in the range of 65 to 77% by weight,
(2) the weight-average molecular weight (Mw) in terms of polystyrene, as measured by GPC, is in the range of 80,000 to 400,000,
(3) Mw/Mn is not more than 2.4,
(4) the melting point (Tm), as measured by DSC, is in the range of 15 to 60° C.,
(5) the ethylene content (E, % by weight) and the melting point (Tm, ° C.), as measured by DSC, satisfy the following relation (I):
3.31×
E−
186≧
Tm
(I),
and
(6) the intensity ratio, S&agr;&bgr;/S&agr;&agr;, measured by
13
C-NMR spectrum is not more than 0.5.
Further, the ethylene/&agr;-olefin copolymer (B) is preferably an ethylene/&agr;-olefin copolymer (B-2) having the following properties:
(1) the ethylene content (E) is in the range of 40 to 55% by weight,
(2) the weight-average molecular weight (Mw) in terms of polystyrene, as measured by GPC, is in the range of 80,000 to 400,000,
(3) Mw/Mn is not more than 2.4,
(4) the melting point (Tm), as measured by DSC, is not higher than −20° C.,
(5) the ethylene content (E, % by weight) and the melting point (Tm, ° C.), as measured by DSC, satisfy the following relation (I):
3.31×
E−
186≧
Tm
(I),
and
(6) the intensity ratio, S&agr;&bgr;/S&agr;&agr;, measured by
13
C-NMR spectrum is not more than 0.5.
In the lubricating oil composition, the ethylene/&agr;-olefin copolymer (B) is preferably an ethylene/propylene copolymer.
The ethylene/&agr;-olefin copolymer (B) is preferably a copolymer having a ratio (I
10
/I
2
) of the melt index (I
10
) as measured at 190° C. under a load of 10 kg to the melt index (I
2
) as measured at 190° C. under a load of 2.16 kg ranging from 8 to 16.
Further, the ethylene/&agr;-olefin copolymer (B) is preferably a copolymer having a ratio (I
10
/I
2
) of the melt index (I
10
) as measured at 190° C. under a load of 10 kg to the melt index (I
2
) as measured at 190° C. under a load of 2.16 kg being not less than 5 and less than 8.
BEST MODE FOR CARRYING OUT THE INVENTION
The viscosity modifier for lubricating oil and the lubricating oil composition according to the invention are described in detail hereinafter.
Visco
Kaneshige Ryousuke
Okada Keiji
Birch & Stewart Kolasch & Birch, LLP
Howard Jacqueline V.
Mitsui Chemicals Inc.
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