Partly synthetic multigrade crankcase lubricant

Details Partly synthetic multigrade crankcase lubricant Partly synthetic multigrade crankcase lubricant

1999-03-12

2001-10-16

Medley, Margaret (Department: 1714)

Solid anti-friction devices, materials therefor, lubricant or se

Lubricants or separants for moving solid surfaces and...

Organic -co- compound

C508S463000, C585S010000

Reexamination Certificate

active

06303548

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a multigrade crankcase lubricants that have good low and high temperature properties. More particularly the present invention relates to an SAE
0
W-40 lubricant that contains both a conventional mineral basestock and a nonconventional or synthetic lubricant.
BACKGROUND OF THE INVENTION
Crankcase lubricating oils must provide minimal frictional wear in an engine over a wide range of operating temperatures. These engine temperatures can range from below freezing during cold weather starting to above 400° F. (200° C.) during severe usage. Lubricants which meet SAE viscosity specifications for both low and high temperatures are known as multigrade oils.
Blending basestocks of different viscosities is one way of formulating a multigrade oil. Merely blending basestocks of different viscosities, however, may not enable the formualtors to meet the low and high temperature viscosity requirements of some multigrade oils let alone other properties such as volatility and seal compatibility. The formulator's primary tool for meeting multigrade oil viscosity requirements is an additive referred to as a viscosity modifier.
An alternative means of reducing the basestock viscosity is to employ so-called non-conventional lubricants (or NCL). Examples of NCLs are synthetic basestocks such as polyalphaolefin oligomers (PAO) and diesters and specially processed mineral basestocks such as basestocks that have been hydro-cracked or hydroisomerised to give greater paraffinic content and lower aromatic content. These NCLs, especially the diesters, are very expensive, may not respond well to conventional antioxidant systems, and may not be fully compatible with standard sealant materials.
Accordingly, it is an object of the present invention to provide an
0
W-40 motor oil that has desirable low and high temperature properties.
It is another object to provide a motor oil that is a blend of conventional and non-conventional lubricants.
These and other objects will become apparent upon reading the description which follows.
SUMMARY OF THE INVENTION
A base oil for an SAE
0
W-40 lubricant is provided comprising a mixture of mineral basestock, a polyalpha olefin and a synthetic ester lubricant. The SAE
0
W-40 lubricant includes a viscosity improver, especially a mixture of VI improvers. Optionally, the lubricant includes antioxidant additives.
Engine lubricants containing the base oil of the present invention are capable of improving the fuel efficiency of an engine under conditions of use.
DETAILED DESCRIPTION OF THE INVENTION
1. THE BASE OIL
A. Mineral Basestock
The basestock used in the base oil may be selected from any of the natural mineral oils of API Groups I, II, III, IV or mixtures of these used in crankcase lubricating oils for spark-ignited and compression-ignited engines. Preferably, the mineral basestock is a Group II or III basestock having the properties shown in Table 1.
TABLE 1
Pour
Flash
KV @
KV @
KV @
Point,
Saturates,
Sulfur,
COC,
40° C. cSt
100° C. cSt
100° F. SUS
VI
° C.
wt %
wt %
° C.
13.0-23.0
3.5-5.0
70-125
90-150
<−12
>75
<0.1
>170
B. The Polyalpha Olefin
The polyalpha olefin (PAO) used in the base oil may be selected from any of the olefin oligomer oils used in lubricants. In general the PAO will have a viscosity at 100° C. in the range of about 3.5 to about 4.5 cSt and preferably about 3.7 to about 4.2 cSt. Preferably the polyalpha olefin is one having the properties shown in Table 2.
TABLE 2
Pour
Flash
KV @
KV @
KV @
Point,
Saturates,
Sulfur,
COC,
40° C. cSt
100° C. cSt
100° F. SUS
VI
° C.
wt %
wt %
° C.
16.0-18.0
3.7-4.2
85-100
115-135
<−60
>99.9
<0.01
>204
C. The Ester
Useful synthetic esters include the esters of monocarboxylic and poly-carboxylic acids with monohydroxy alcohols and polyols. Typical examples include didodecyl adipate, diisodecyl adipate, pentaerythritol tetracaproate, and dilauryl sebacate. In general, the ester used will have a viscosity at 100° C. in the range of about 2 to about 4 cSt and preferably about 2.5 to about 3.5. Preferred properties for the ester are given in Table 3.
TABLE 3
KV @
KV @
Pour Point,
Flash COC,
40° C. cSt
100° C. cSt
VI
° C.
° C.
8.5-14.0
2.5-3.5
110-160
<−60
>190
D. The Proportions
The base oil typically comprises from about 5 to 80 vol % of the mineral basestock, from about 5 to 90 vol % of the polyalpha olefin and from about 1 to 30 vol % of the ester. Preferably, the base oil comprises 20 to 50 vol % of the basestock, 30 to 75 vol % polyalpha olefin and 3 to 20 vol % esters. In a particularly preferred embodiment the base oil comprises from about 25 to 45 vol % of the mineral base stock, from about 40 to 70 vol % of the polyalpha olefin and from about 3 to 20 vol % esters.
2. VI IMPROVERS
An SAE
0
W-40 lubricant of the invention comprises the above base oil and VI improvers. VI improvers are components of lubricants which serve to decrease the viscosity changes in a lubricant with changes in temperature. Many different polymers are known to function as VI improvers. See for example, Smalheer, et al.,
Lubricant Additives
, The Lezium-Hiles Company (1967), pages 8 and 9.
Of the many compounds known to be useful as VI improvers, alkyl methacrylate copolymers (PMA's) are recognized as having especially beneficial VI improver properties. Within this class, interpolymers of a short chain alkyl methacrylate, a long chain alkyl methacrylate and N,N-dialkylaminoalkyl methacrylate and/or methacrylamide (the alkyls of the dialkylaminoalkyl moiety having 1 to 6 carbon atoms) are particularly beneficial.
Typically VI improvers are formed in a hydrocarbon solvent and it is in this form that they are blended in the base oil.
Another group of VI improvers are olefin copolymers (OCP's) such as copolymers of ethylene and propylene.
These too typically are prepared in a solvent and are blended, in this form, in the base oil.
A third group of VI improver is hydrogenated diene copolymers which include styrene-hydrogenated diene block copolymers and hydrogenated star-branched polyisoprene. These polymers are made by an anionic polymerization process. They are typically available as a blend with a basestock and are added to the base oil as a blend.
The viscosity modifier used in the invention will be used in an amount to give the required viscosity characteristics. Since viscosity modifiers are often added to blends in the form of oil solutions the amount of additive employed will depend on the concentration of polymer in the oil solution comprising the additive. However, by way of illustration, typical oil solutions of polymer used as viscosity modifiers are used in amount of from 1 to 30% of the blended oil. The amount of viscosity modifier as active ingredient of the oil is generally from 0.01 to 6 wt %, and more preferably from 0.1 to 4 wt %.
In the present invention it is preferred to use both a PMA and a OCP or hydrogenated diene VI improver in amounts ranging from about 3.0 to 7.0 vol % for the PMA VI improver and from about 4.0 to about 9.0 vol % for the OCP or hydrogenated diene VI improver.
3. DDI
The motor oil of the present invention has multifunctional additives of the type found in modem oil formulations. These additives are usually not added independently, but are precombined in DDI (detergent-dispersant-inhibitor) packages which can be obtained commercially from suppliers of lube oil additives. DDI packages with a variety of ingredients, proportions and characteristics are available.
4. ANTIOXIDANTS
Optionally, the motor oil may contain minor but effective amounts of antioxidants such as those used in contemporary motor oil formulations. A particularly preferred antioxidant comprises a mixture of alkylated diphenyl amine and hindered phenols.


REFERENCES:
patent: 3838049 (1974-09-01), Souillard et al.
patent: 4402841 (1983-09-01), Schieman
patent: 4853139 (1989-08-01), Ichihashi
patent: 4956122 (1990-09-01), Watts et al.
patent: 5108635 (1992-04-01), Gabi

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