WO2012017023A1

WO2012017023A1 - Lubricating composition

Info

Publication number: WO2012017023A1
Application number: PCT/EP2011/063397
Authority: WO
Inventors: Gilbert Robert Bernard Germaine; David John Wedlock
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2010-08-03
Filing date: 2011-08-03
Publication date: 2012-02-09
Anticipated expiration: 2013-02-03
Also published as: JP2013532760A; JP5865907B2

Abstract

The present invention provides a lubricating composition comprising a base oil and one or more additives, wherein the base oil comprises a residual Fischer-Tropsch derived base oil and wherein the lubricating composition has a kinematic viscosity at 0°C (according to ASTM D 445) of above 16.3 cSt.

Description

LUBRICATING COMPOSITION

The present invention relates to a lubricating composition comprising a base oil and one or more

additives for particular use in the crankcase of an engine .

In order to formulate engine oils having a high kinematic viscosity at 100°C (such as SAE xW-50 and SAE xW-60 grades of the so-called SAE J300 Specifications as revised in January 2009; SAE stands for Society of

Automotive Engineers) a formulator typically has the choice of using mineral bright stock or heavy poly-alpha olefins (heavy PAOs; heavy PAOs typically have a kinematic viscosity at 100°C of above 20 cSt) .

A problem of the use of mineral bright stock, a residual mineral base oil, is the inherently lower quality thereof, resulting in e.g. limited oxidation stability. A problem of the use of heavy PAOs is the inherent high cost thereof. Attempts have been made in the past to solve this problem by combining the desirable cost-effectiveness of lighter distillate GTL base oils with a minimal amount of heavy PAO.

It is an object of the present invention to minimize one or more of the above problems.

It is another object of the present invention to provide alternative lubricating compositions, in

particular for use in the crankcase of an engine, in particular as SAE xW-50 and SAE xW-60 or even heavier formulations, more in particular SAE 20W-50 and SAE 20W-60 and heavier formulations.

One or more of the above or other objects can be obtained by the present invention by providing a lubricating composition comprising a base oil and one or more additives, wherein the base oil comprises a residual Fischer-Tropsch derived base oil and wherein the

lubricating composition has a kinematic viscosity at 100°C (according to ASTM D 445) of above 16.3 cSt .

It has now surprisingly been found according to the present invention that suitable lubricating compositions (in particular engine oils) having a high kinematic viscosity at 100°C (such as SAE xW-50 and xW-60

formulations) can be formulated, without the need of using mineral bright stock or heavy poly-alpha olefins (PAOs) .

An advantage of the present invention is that the lubricating compositions have surprisingly low Noack volatility values (according to ASTM D 5800), in some embodiments as low as below 3.5 wt . % .

There are no particular limitations regarding the base oil used in lubricating composition according to the present invention (provided that the base oil comprises at least a residual Fischer-Tropsch derived base oil and provided that the requirements in respect of the

lubricant composition according to the present invention are met), and various conventional mineral oils,

synthetic oils as well as naturally derived esters such as vegetable oils may be conveniently used.

The base oil used in the present invention may - in addition to the residual Fischer-Tropsch derived base oil - conveniently comprise mixtures of one or more mineral oils and/or one or more synthetic oils; thus, according to the present invention, the term "base oil" may refer to a mixture containing more than one base oil, including at least one residual Fischer-Tropsch derived base oil. Mineral oils include liquid petroleum oils and solvent- treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

Suitable base oils for use in the lubricating oil composition of the present invention are Group I-III mineral base oils (preferably Group III), Group IV poly- alpha olefins (PAOs), Group II-III Fischer-Tropsch derived base oils (preferably Group III) and mixtures thereof .

By "Group I", "Group II" "Group III" and "Group IV" base oils in the present invention are meant lubricating oil base oils according to the definitions of American Petroleum Institute (API) for categories I, II, III and IV. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

Fischer-Tropsch derived base oils are known in the art. By the term "Fischer-Tropsch derived" is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil in the lubricating composition of the present invention are those as for example disclosed in EP 0 776 959, EP 0 668 342, WO

97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO

00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166.

Synthetic oils include hydrocarbon oils such as olefin oligomers (including polyalphaolefin base oils; PAOs), dibasic acid esters, polyol esters, polyalkylene glycols

(PAGs), alkyl naphthalenes and dewaxed waxy isomerates. Synthetic hydrocarbon base oils sold by the Shell Group under the designation "Shell XHVI" (trade mark) may be conveniently used.

Poly-alpha olefin base oils (PAOs) and their

manufacture are well known in the art. Preferred poly- alpha olefin base oils that may be used in the lubricating compositions of the present invention may be derived from linear C₂ to C32, preferably C6 to Ci₆, alpha olefins.

Particularly preferred feedstocks for said poly-alpha olefins are 1-octene, 1-decene, 1-dodecene and 1- tetradecene .

There is a strong preference for using a Fischer-

Tropsch derived base oil over a PAO base oil, in view of the high cost of manufacture of the PAOs. Thus,

preferably, the base oil contains more than 50 wt.%, preferably more than 60 wt.%, more preferably more than 70 wt.%, even more preferably more than 80 wt.%. most

preferably more than 90 wt.% Fischer-Tropsch derived base oil. In an especially preferred embodiment less than 10 wt.%, preferably less than 5 wt.%, more preferably not more than 2 wt.%, of the base oil is not a Fischer-Tropsch derived base oil.

It is preferred that the lubricating composition according to the present invention contains less than 20 wt.%, preferably less than 10 wt.%, more preferably less than 5 wt.%, of a PAO base oil, based on the total weight of the composition.

It is even more preferred that 100 wt% of the base oil is based on one or more Fischer-Tropsch derived base oils.

The total amount of base oil incorporated in the lubricating composition of the present invention is preferably present in an amount in the range of from 60 to

99 wt.%, more preferably in an amount in the range of from 65 to 90 wt.% and most preferably in an amount in the range of from 70 to 85 wt.%, with respect to the total weight of the lubricating composition.

The compositions of the present invention comprise a residual Fischer-Tropsch base oil. As used herein the term "residual base oil" means a base oil where the initial boiling point can be fixed in a high vacuum column, at the heavy end or bottom end, but where the final boiling point is a resultant of the feedstock being distilled. Such final boiling point would exceed the thermal cracking temperature of the feedstock even under vacuum conditions.

A residual Fischer-Tropsch base oil gives a viscosity grade in the same range as mineral brightstock, yet while being residual, does not suffer from the compositional/ performance limitations of mineral brightstocks . A residual Fischer-Tropsch base oil is highly paraffinic with low aromatics content, high inhibited oxidational stability and of the same order of viscosity as a heavy PAO.

Typically the lubricating composition according to the present invention comprises a residual Fischer-Tropsch derived base oil having a kinematic viscosity at 100°C (according to ASTM D445) of at least 15 cSt and preferably above 18 cSt; preferably, this residual Fischer-Tropsch derived base oil has a kinematic viscosity at 100°C of below 30 cSt. Of course, the lubricating composition according to the present invention may contain one or more further Fischer-Tropsch derived base oils having a lower kinematic viscosity at 100°C, such as about 3, 5 and 8 cSt .

As mentioned above, the lubricating composition according to the present invention has a kinematic viscosity at 100°C of above 16.3 cSt . Preferably, the lubricating composition according to the present invention has a kinematic viscosity at 100°C of above 21.9 cSt, more preferably above 23.0 cSt . Typically, the kinematic viscosity at 100°C of the lubricating

composition according to the present invention is below 30.0 cSt, such as below 26.1 cSt .

Preferably, the dynamic viscosity at -15°C

(according to ASTM D 5293) of the lubricating composition according to the present invention is below 9500 cP (1 cP is the same as 1 mPa.s), preferably below 8000 cP, more preferably below 7500 cP, even more preferably below 7000 cP . Typically, the dynamic viscosity at -15°C of the lubricating composition is above 5000 cP, preferably above 6000 cP .

Preferably, the dynamic viscosity at -20°C

(according to ASTM D 5293) of the lubricating composition according to the present invention is above 7000 cP (1 cP is the same as 1 mPa.s), preferably above 8000 cP, more preferably above 9000 cP, even more preferably above 10000 cP . Typically, the dynamic viscosity at -20°C of the lubricating composition is below 15000 cP, preferably below 14000 cP .

Preferably, the high temperature, high shear viscosity ("HTHS"; according to ASTM D 4683) of the lubricating composition according to the present invention is above 3.7 cP, preferably above 4.5 cP, more preferably above 5.0 cP, or even as high as above 5.5 or 6.0 cP . Typically, the HTHS is below 8.0 cP .

Typically, the Noack volatility (according to ASTM D 5800) of the lubricating composition according to the present invention is between 1 and 15 wt.%, preferably below 14 wt.% and more preferably below 10.0 wt.%.

According to an especially preferred embodiment according to the present invention, the Noack volatility is below 6.0 wt.%, more preferably below 5.0 wt . % or even as low as below 4.0 or below 3.5 wt.%.

The lubricating composition according to the present invention further comprises one or more additives such as anti-oxidants , anti-wear additives, dispersants,

detergents, overbased detergents, extreme pressure

additives, friction modifiers, viscosity index improvers, pour point depressants, metal passivators, corrosion inhibitors, demulsifiers , anti-foam agents, seal

compatibility agents and additive diluent base oils, etc.

As the person skilled in the art is familiar with the above and other additives, these are not further discussed here in detail. Specific examples of such additives are described in for example Kirk-Othmer

Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526.

Preferably the lubricating composition according to the present invention contains less than 1.0 wt.% of a Viscosity Index improver concentrate, based on the total weight of the composition. Most preferably, the

composition is free of Viscosity Index improver

concentrate .

Preferably, the lubricating composition contains at least 0.1 wt.% of a pour point depressant. As an

example, alkylated naphthalene and phenolic polymers, polymethacrylates , maleate/fumarate copolymer esters may be conveniently used as effective pour point depressants. Preferably not more than 0.3 wt.% of the pour point depressant is used.

The lubricating compositions of the present

invention may be conveniently prepared by admixing the one or more additives with the base oil(s) .

The above-mentioned additives are typically present in an amount in the range of from 0.01 to 35.0 wt.%, based on the total weight of the lubricating composition, preferably in an amount in the range of from 0.05 to 25.0 wt.%, more preferably from 1.0 to 20.0 wt.%, based on the total weight of the lubricating composition.

Preferably, the composition contains at least 9.0 wt.%, preferably at least 10.0 wt.%, more preferably at least 11.0 wt% of an additive package comprising an anti- wear additive, a metal detergent, an ashless dispersant and an anti-oxidant .

The lubricating compositions according to the present invention may be so-called "low SAPS" (SAPS = sulphated ash, phosphorus and sulphur) , "mid SAPS" or "regular SAPS" formulations .

For Passenger Car Motor Oil (PCMO) engine oils the above ranges mean:

- a sulphated ash content (according to ASTM D 874) of up to 0.5 wt.%, up to 0.8 wt.% and up to 1.5 wt.%,

respectively;

- a phosphorus content (according to ASTM D 5185) of up to 0.05 wt.%, up to 0.08 wt.% and typically up to 0.1 wt.%, respectively; and

- a sulphur content (according to ASTM D 5185) of up to 0.2 wt.%, up to 0.3 wt.% and typically up to 0.5 wt.%, respectively.

For Heavy Duty Diesel Engine Oils the above ranges mean :

- a sulphated ash content (according to ASTM D 874) of up to 1 wt.%, up to 1 wt.% and up to 2 wt.%, respectively; - a phosphorus content (according to ASTM D 5185) of up to 0.08 wt.% (low SAPS) and up to 0.12 wt.% (mid SAPS), respectively; and

- a sulphur content (according to ASTM D 5185) of up to 0.3 wt.% (low SAPS) and up to 0.4 wt . % (mid SAPS),

respectively .

The present invention is described below with

reference to the following Examples, which are not

intended to limit the scope of the present invention in any way.

Examples

Lubricating Oil Compositions

Various engine oils for use in a crankcase engine were formulated.

Table 1 indicates the properties for the base oils used. Table 2 indicates the composition and properties of the fully formulated SAE 20W-50, SAE 20W-60 and "20W- 70" engine oil formulations that were tested (SAE xW-70 grades do not exist yet; "XW-70" and "20W-70" are meant to refer to heavier grades than SAE xW-60 and SAE 20W-60, respectively) ; the amounts of the components are given in wt.%, based on the total weight of the fully formulated formulations .

"Base oil 1" was a Fischer-Tropsch derived base oil

("XHBO") having a kinematic viscosity at 100°C (ASTM D445) of approx. 19 cSt (mm2s-l) .

"Base oil 2" was a Fischer-Tropsch derived base oil ("XHBO") having a kinematic viscosity at 100°C (ASTM D445) of approx. 17 cSt (mm2s-l) .

Base oils 1 and 2 may be conveniently manufactured by the process described in e.g. US 7 354 508 B2, the teaching of which is hereby incorporated by reference.

"Base oil 3" was a commercially available PAO base oil having a kinematic viscosity at 100°C (ASTM D445) of

7.83 cSt . Base oil 3 is commercially available from e.g. ExxonMobil Chemicals (Brussels, Belgium) under the trade designation "PAO 8". "Base oil 4" was a commercially available PAO base oil having a kinematic viscosity at 100°C (ASTM D445) of 40.33 cSt . Base oil 4 is commercially available from e.g. ExxonMobil Chemicals (Brussels, Belgium) under the trade designation "PAO 40".

All tested engine oil formulations contained a combination of one more base oils, an additive package, a Viscosity Index improver concentrate and optionally a pour point depressant, which additive packages were the same in all tested compositions.

The additive package contained a combination of additives including anti-oxidants , a zinc-based anti-wear additive, an ashless dispersant, an overbased detergent mixture and about 10 ppm of an anti-foaming agent.

The Viscosity Index improver concentrate contained a conventional polymeric viscosity modifier (Infineum SV- 151 [a styrene-hydrogenated isoprene diblock polymer]; available from Infineum Additives (Milton Hill, Abingdon, UK) dissolved in a mixture of Shell XHVI base oil and an ester base stock) .

The pour point depressant was a conventional

polyalkyl methacrylate (PAMA) pour point depressant, commercially available from Evonik Rohmax Additives GmbH (Darmstadt, Germany) under the trade designation

"Viscoplex® 6-054".

The compositions of Example 1-7 were obtained by mixing the base oils with the additive packages and pour point depressant, using conventional lubricant blending procedures .

Table 1

Base oil 1 Base oil 2 Base oil 3 Base oil 4 (XHBO 1) (XHBO 2) (PAO 8) (PAO 40)

Kinematic 131.9 122.8 46.5 400.6 viscosity at 40°C¹

[cSt]

Kinematic 19.0 17.2 7.8 40.3 viscosity at

lOC^C¹ [cSt]

VI Index² 163 153 138 151

Pour point³ [°C] -30 -36 -66 -45

According to ASTM D 445

^According to ASTM D 2270

According to ASTM D 5950

Table 2

According to ASTM D 445

According to ASTM D 5293. NB 1 cP (centiPoise) = 1 mPa . s (milliPascal . second) According to ASTM D 4683

According to ASTM D 5800

n.d. = not determined

Discussion

As can be seen from Table 2, the present invention surprisingly allows to formulate lubricating compositions such as engine oils having a high kinematic viscosity at 100°C (such as SAE xW-50, SAE xW-60 and "xW-70" grades), without the need of using mineral bright stock or heavy poly-alpha olefins (PAOs) .

The lubricating composition according to the present invention have surprisingly low Noack volatility values, as low as below 3.5 wt . % .

Claims

C L A I M S

1. A lubricating composition comprising a base oil and one or more additives, wherein the base oil comprises a residual Fischer-Tropsch derived base oil and wherein the lubricating composition has a kinematic viscosity at 100°C (according to ASTM D 445) of above 16.3 cSt.

2. Lubricating composition according to claim 1, wherein the lubricating composition has a kinematic viscosity at 100°C of above 21.9 cSt .

3. Lubricating composition according to claim 1 or 2, wherein the lubricating composition has a dynamic

viscosity at -15°C (according to ASTM D 5293) of below 9500 cP.

4. Lubricating composition according to any one of claims 1 to 3, wherein the lubricating composition has a dynamic viscosity at -20°C (according to ASTM D 5293) of above 7000 cP .

5. Lubricating composition according to any one of claims 1 to 4, wherein the composition has a high

temperature, high shear viscosity ("HTHS"; according to ASTM D 4683) of above 3.7 cP .

6. Lubricating composition according to any one of claims 1 to 5, wherein the composition has a Noack volatility (according to ASTM D 5800) of below 15 wt.%, preferably below 14 wt.%.

7. Lubricating composition according to any one of claims 1 to 6, wherein the base oil contains more than 50 wt.%, preferably more than 60 wt.%, more preferably more than 70 wt.%, even more preferably more than 80 wt.%, most preferably more than 90 wt.% residual Fischer- Tropsch derived base oil.

8. Lubricating composition according to any one of claims 1 to 7, wherein the composition contains less than 10 wt.%, preferably less than 5 wt.%, of a PAO base oil, based on the total weight of the composition.

9. Lubricating composition according to any one of claims 1 to 8, wherein the composition contains less than 1.0 wt.% of a Viscosity Index improver concentrate, based on the total weight of the composition.

10. Lubricating composition according to any one of claims 1 to 9, wherein the lubricating composition comprises a residual Fischer-Tropsch derived base oil having a kinematic viscosity at 100°C of above 15 cSt, preferably above 18 cSt .

11. Lubricating composition according to claim 10, wherein the residual Fischer-Tropsch derived base oil has a pour point (according to ASTM D 5950) of below -6°C.