CA2285138C - A partly synthetic multigrade crankcase lubricant - Google Patents

Abstract

A base oil for an SAE OW-40 lubricant composition comprises a mineral basestock, a polyalpha-olefin and a synthetic ester lubricant The SAE OW-40 lubricant comprises the base oil and a viscosity index improver selected from the group consisting of polymethacylatc, olefin polymer, hydrogenated diene, copolymer mixtures of all three or mixtures of olefin polymer and hydrogenated diene copolymer.

Description

A PARTLY SYNTHETIC MULTIGRADE CRANKCASE LUBRICANT
FIELD OF THE I7%T*-~ON

The present invention relates to a multigrade crankcase lubricant that has good low and high t,emperataze properties. More particularly the present invention relates to an S.AE OW-401ubricant that contains both a conventional mineral basestock and a nonconventional or synthetic lubricant.
BACKGROUND OF 'tHE IlWEN1'ION

Crankcase lubricating oils must provide minimal frictioasl wear in an engine ovcr a wide range of operating temperatures. These engine tempera-turcs can range from below freezing during cold weather starting to above 400 F
(200 C) during severe usage. Lubricants wbich mcet SAE viscosity specifica-tions for both low and high temperatures are known as multigrade oils.

Blending basestocks of different viscosities is one way of formulat-ing a multigradc oil. Merely blending basestocks of different viscosities, howcver, may not enable the form.ulators to meet the low aud high tempcrature viscosity requirements of some multigrade oils Iet alone othcr properties such as volatility and seal compatibility. The formnlator'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 cmploy so-called non-conventional lubricants (or NCL). Examples of NCL's are synthetic basestocks such as polyalpha-olcfin oligomcrs (PAO) and diesters and speciaUy processed mineral basestocks such as basestocks that have been hydro-cracked or hydroisomerised to give greater paraffmic content and lower aromatic content. These NCL's, 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 SAE OW-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 conven-tional and non-conventional lubricants.

These and other objects will become apparent upon rcading the description which follows.

SUIVIlVIAIZY OF THE INVENTION

A base oil for an SAE OW-40 lubricant is provided comprising a mixture of mineral basestock, a poXyalpba-olefin and a synthetic ester lubricant.
The SAE OW-40 lubricant includes a vi,scosity improver, especially a mixture of VT i.mprovers- OptiioAaIly, the lubricant includes antioxidant additives.

Engine lubricants containing the base oil of the present invention are capable of improving the fuel effiieiency of an engine under conditions of use.
DETAILED T)ESCRIPTION OF THE I]VYENTIO1y 1. THE BASE O.II.

A. Mineral Basestock Tb.e basestock used in the base oil may be selected from any of the natural m.ineral oils of API Groups I, II, III, IV or m.i.xtures of these used in cranlccase lubricating oils for spark-ignited and compression-ignited engines, Preferably, the mineral basestock is a Group II or III
bascstock having the properties shown in Tablc 1.

KV @ KV ~ Pour Flash KV Q, 100 C 100 F Point, Sararates, Sulfur, COC, 40 C cSt eSt SUS VI C wt% wt% C
13.0-23.0 3.5-5.0 70-125 90-150 ~-12 >75 < 0- X> 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 c3t Prcferably the polyalpha-olefin is one having the propertics shown in Table 2.

K'V @ Pour FLas,h KV @ KV @ 100 F Point, Saturates, Sulfur, COC, 40 C cSt 100 C cSt SU5 VI C wt% wi !o C
16Ø18.0 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 exannples include didodecyl adipate, diisodecyl adipate, penta-erythritol 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-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 5 to 90 vol% of the mineral base-stock, 5 to 90 vol% of the polyalpha-olefin and 1 to 30 vol% of the ester. Preferably, the base oil comprises 20 to 50 vol% of the basestock, 30 to 75 vo1% polyalpha-olefin and 3 to 20 vo1% estcrs. In a particularly preferred embodiment the base oil comprises 25 to 45 vol% of the mineral base stock, 40 to 70 vol% of the polyalpha-olefin and 3 to 20 voI% esters.

2. VIIlvPROVERS

An SAE OW-401ubricant of the invention comprises thc abovc base oil and VI iunpTovers. VI improvers are components of lubricants which serve to decrease the viscosity changes in a lubricant with changes in temperature.
Many different polymers auce known to function as VI improvers. See for example, Smalheer, et al., Lubricant Additives, The Lezium-Hil.es Company (1967), pagcs 8 and 9.

Of the maay coYnpounds lcnown to be useful as VI improvcrs, alkyl mcthacrylate copolymers (PMA's) are recognizcd as having especially beneficial VI improver propexti,es. Within this class, interpolymers of a short chai.n 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 olefn polymers which include olefin copolymers (OCP's) such as copolymers of ethylene, propyleuc, and diene as well as high molecular weight polyalpha-olefin. The molecular weights of the polyalpha-olefm. VI improvers are from about 3000 to 100,000, preferably from. 5,000 to 60,000.

Some of thcse, 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 dicnc copolymers whioh include styrene-hydrogenated dienc block copolymers and hydrogenated star-branched polyisoprcnc. These polymers are made by an anionic polymerization process. They are typically available as a blend wi.th a basestock and are added to the base oil as a blend..

The viscosity Index imparovers used have Shear Stability Index (SSI) determined by ASTM D3945 bctween 0 to 45, preferably between 5 and 40.

wh,en used as a mixture, the SSI of the mixture of viscosity index irnprovers should be between 0 to 45, preferably between 5 and 40.

The viscosity modifier used in the invention will be used in an amount to give the required viscosity characteristics. Since viscosity modi.fiers are often added to blends in the form of oil solutions the amount of additive employed wiU 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 generaIly from 0.01 to 25 wt%, preferably 0.1 to 15 wt!*/.% and morc preferably from 0.5 to 10 wt%.

In the present invention the above recited VI improvers can be used individually or as a mixture of all of the recited types, e.g., as a mixture of polymethacrylate, o1eSn copolyAaer, high molecular weight polyalpha-olefiia, and hydrogenated diene copolymcr VI improvers, or as a mixture of one oz morc vlefin polymcrs and the hydrogenated diene copolymer VI
umprovers, or as a mixture of polymethacrylate and high molecular wexgbht polyalpha-olefin VI improver, or as a mixture of polym.ethacryXate, high molecular weight polyalpha olefin and olefin copolym,er.

3. DDI

The motor oil of the present invention has multifumetional additives of the type found in modem oil formulations. These additives are usually not added independently, but are precombined in DDI (detergent-d.ispersant-inhibitor) packages which can be obtaincd commcrcially from suppliers of lube oil additives. DDI packages with a variety of i,ngredients, proportions and characteristics are avaiaabl.e.

4. ANTIOXIDANTS

Optionally, the motor oil may contain minor but effective amounts of antioxidants such as those used in contempozary xr-otor oil formulations. A
particularly preferred antioxidant comprises a mixturc of alkylated diphenyl amine and hindered phenols.

EXAMPLES
The invention will now be described by way of illustration only with reference to the ollowiuu,g examples. In the examples, unless otherwise noted, all treat rates of all additives are reported as volume percent Examples 1. 2. 3, and 4 and Examples A, B, C

Experimental SAE OW-40 lubricants werc madc having the compositions given in Table 4. The Table also gives thc acccptable property limits or targets and the actual mcasured properties for each formulation.

_ c; 1 ~~ g`,.00~=,~'= n;5~
M
..-i 'r- \p .-M-+ ..~r C*4 N
N
Q ._M. C

W o o~ o _p, s., o o r, ~
N > i > i i > i ~ m~ M
S O R tn O~ ~O t+i ~G vi N t+1 ~.r ..1 pp O 00 al ~C ~C O M ~
¾ N M -+ =~ OD V'1 Yp ~ A

b a W A A~ e~, a, a. n, v~ E-+ ~ v n A v O =~
U
o ?
M
V

* *a ~ 8 0 0 0 *5 ~ zr .~ -~
y > O O a 4 4~ ~ U~~ N 2 *

wi ;
N a=~0' c'~
ae ~
~
o T c o - o y N M =~'-~ ^~' ~ ~ u zy ~ N M `^ c-i x L-4 C

D~awCAOaaw~v~C-~~v n v ..
O o .9 ..
ca3'~cn ~" ~ =.~
~~ --~'y G` ,~0~ ~0' ~ ~ Oa a, 4~ ~

E~
jo on z H ~ y y V]
ZO .~ = U
a an J ,.~. .e~

R' of = ~ w ~ x a Wd rA
o W ~z~~~~=~
w Ii ~~

^ 9 ~

_~ ~ ~ =~ a y p4 P=1 .y. ad to ~ r .... = ..
~-;> FO ~ v v d d d d v'~
.1 cri c+; er vi ~v r oo r~;

As shown in the above table, the right balancc of the VI improvers as well as the base oil components leads to formulations with desirsble performance characteristics. Formulations A, B, and C fail to meet the targets in one or more aspects.

Examvle 3 The fueX consumption of a Detroit Diesel series 60 engine was measured ovez a range of driving conditions using the OW-401ubricant of Example 1. The results were compared with operating the same engine over the same driving conditions but using commerci.ally available 15W-40 oiJ.. The peraent increase in fuel efficiency is shown in'fable V_ IABLE V

City Stop Level Rolling Highway and Go Hi wa H~i wa Mountains Fuel Efficiency 2.2% 1.06% 0.89% 0.63%
Benefit

Claims (4)

1. An SAE OW-40 lubricant comprising:
a base oil consisting essentially of from 5 to 90 vol% of a mineral basestock having a viscosity at 100°C in the range of about 3.5 to 5.0 cSt, from 5 to 90 vol% of a polyalpha-olefin lubricant having a viscosity at 100°C in the range of about 3.5 to 4.5 cSt, and from 1 to 30 vol% of an ester lubricant having a viscosity at 100°C in the range of about 2 to about 4 cSt;
0.01 to 25 wt% of a VI improver being a polymethacrylate VI improver, an olefin polymer VI improver, a hydrogenated diene VI improver, a mixture of one or more olefin polymer VI improver and hydrogenated diene copolymer VI improver, a mixture of polymethacrylate, one of more olefin polymer and hydrogenated diene copolymer VI
improvers, a mixture of polymethacrylate and high molecular weight polyalpha-olefin VI
improvers, or a mixture of polymethacrylate, high molecular weight polyalpha-olefin, and olefin copolymer VI improvers; and a detergent-dispersing inhibitor package.

2. The lubricant of claim 1, wherein the base oil consists essentially of 20 to 50 vol%
mineral basestock, 30 to 75 vol% polyalpha-olefin and 3 to 20 vol% ester, and optionally an antioxidant additive.

3. The lubricant of claim 2, wherein the antioxidant additive is a mixture of alkylated diphenyl amine and hindered phenols.

4. An engine lubricant capable of improving the fuel efficiency of the engine, the lubricant comprising:
a base oil consisting essentially of from 25 to 45 vol% of a mineral basestock having a viscosity at 100 C in the range of about 3.5 to 5.0 cSt, from 40 to 70 vol% of a polyalpha-olefin lubricant having a viscosity at 100°C in the range of 2 to 4 cSt, and from 3 to 20 vol%
of an ester having a viscosity at 100°C in the range of 2.5 to 3.5 cSt;
0.1 to 15 wt% of a VI improver being a polymethacrylate VI improver, an olefin polymer VI improver, a hydrogenated diene VI improver, a mixture of one of more olefin polymer and hydrogenated diene copolymer VI improvers, a mixture of polymethacrylate, one or more olefin polymer and hydrogenated diene copolymer VI improvers, a mixture of polymethacrylate and high molecular weight polyalpha-olefin VI improvers, or a mixture of polymethacrylate, high molecular weight polyalpha-olefin and olefin copolymer VI
improvers; and a detergent-dispersant inhibitor package.