WO2011073349A1

WO2011073349A1 - Lubricating composition

Info

Publication number: WO2011073349A1
Application number: PCT/EP2010/069974
Authority: WO
Inventors: David Colbourne; Keith Selby; Noriaki Shinoda
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2009-12-16
Filing date: 2010-12-16
Publication date: 2011-06-23
Also published as: JP2013514416A; EP2186872A1; JP5718358B2

Abstract

The present invention provides a lubricating composition comprising a base oil and one or more additives, the lubricating composition comprising at least : - from 40.0 to 60.0 wt.% of a mineral derived Group I base oil, based on the total weight of the lubricating composition, and - from 10.0 to 40.0 wt.% of a Fischer-Tropsch derived base oil, based on the total weight of the lubricating composition, wherein the lubricating composition has a kinematic viscosity at 100°C (according to ASTM D 445} of below 26.1 cSt.

Description

LUBRICATING COMPOSITION

The present invention relates to a lubricating composition comprising a Fischer-Tropsch derived base oil and one or more additives for particular use in the crankcase of an internal combustion engine, in particular a diesel engine such as a heavy duty diesel engine.

Lubricating compositions comprising a Fischer-Tropsch derived base oil and one or more additives are known in the art. As an example, WO 2008/055975 discloses a so- called low-SAPS lubricating composition comprising a Fischer-Tropsch derived base oil and having a sulphur content of from 0.01 to 0.3 wt.%, a phosphorus content of form 0.01 to 0.1 wt.% and a sulphated ash content of from 0.1 to 1.2 wt.%, based on the total weight of the

lubricating composition. In the actual examples of WO 2008/055975, SAE 5W-40 lubricating compositions are disclosed, comprising either a mixture of Fischer-Tropsch derived base oils or a mixture of Group III base oils.

US 2004/0094453 Al relates to the blending of a low viscosity Fischer-Tropsch derived base oil fraction with a higher viscosity conventional petroleum derived base oil fraction to produce a lubricating base oil that is useful for preparing commercial finished lubricants such as crankcase engine oils. Blend 6 of Example 6 comprises 20 wt.% of a Fischer-Tropsch derived base oil and 80 wt.% of a Group I base oil.

US 2005/0258078 Al relates to lubricant blends and finished gear oils comprising these lubricant blends, wherein the lubricant blends comprise a Fischer-Tropsch derived base oil, a petroleum derived base oil and a pour point depressant. In Table V a lubricant blend is shown, comprising 55.8 wt.% of a Fischer-Tropsch derived base oil, 43.9 wt.% of a Group I base oil and 0.3 wt.% of a pour point depressant. The blend has a kinematic viscosity at 100°C of 5.514. As explained in paragraph [0157] of US 2005/0258078 Al, blends containing Group I base oil are not optimal when compared with blends containing Group II base oil.

WO 2009/071609 Al relates to base oil formulations and to their preparations an uses. Examples 2 and 3 of WO 2009/071609 Al discloses base oil formulations {i.e. not containing additives); Example 2 contains 22.7 wt.%

Fischer-Tropsch derived base oil and 77.3 wt.% of a Group I base oil, whilst Example 3 contains 41 wt.% Fischer-

Tropsch derived base oil and 59 wt.% of a Group I base

US 2003/0100453 relates to a blend of base oils which provides improved oxidation stability. In Table II of US 2003/0100453 shows various blend combinations (not containing additives) of a Fischer-Tropsch derived base oil and a Group I base oil, including a blend containing 48.5 wt.% Fischer-Tropsch derived base oil and 51.5 wt.% of a Group I base oil.

US 2007/0142242 Al relates to high kinematic

viscosity lubricating oils and lubricating oil

formulations and the improvement of the oxidative

stability/resistance to weight loss thereof. Table A of US 2007/0142242 Al discloses a (not-preferred) lubricant formulation having a kinematic viscosity at 40 °C of 230 mm²/s containing 16.6 wt.% of a Fischer-Tropsch derived base oil, 40.1 wt.% of a heavy Group I base oil (bright stock), 20.0 wt.% of PIB and 23.3 wt.% additives.

Although no actual value is given for the kinematic viscosity at 100°C of this (not-preferred) high kinematic viscosity lubricant formulation, this will be well above 26.1 cSt.

It is an object of the present invention to improve the seal compatibility of a lubricating composition, in particular for use in an internal combustion engine such as a diesel engine.

The above or other objects are achieved by the present invention by providing a lubricating composition comprising a base oil and one or more additives, the lubricating composition comprising at least:

- from 40.0 to 60.0 wt.% of a mineral derived Group

I base oil, based on the total weight of the lubricating composition, and

- from 10.0 to 40.0 wt.% of a Fischer-Tropsch derived base oil, based on the total weight of the lubricating composition,

wherein the lubricating composition has a kinematic viscosity at 100°C {according to ASTM D 445) of below 26.1 cSt.

It has surprisingly been found according to the present invention that use of a Fischer-Tropsch derived base oil and a lubricating composition containing it results in an improved seal compatibility properties, in particular as determined by AK6 (7 days at 150°C) and ACM

E7503 (7 days at 150°C) according to the VDA 675301

Daimler specification.

In this respect it is noted that WO 2006/003119 discloses the use of Fischer-Tropsch derived base oils for improving seal swelling properties, in particular in crankcase gear oil applications and hydraulic fluids.

However, WO 2006/003119 does not teach a lubricating composition containing additives and a combination of a

Fischer-Tropsch derived base oil and a mineral derived Group I, let alone for improving seal compatibility properties other than average volume and hardness in the

NBR nitrile rubber seal swell test as measured by

BS903:Part A16:1987/ISO 1817-1985 (see Table 2 on page 27 of WO 2006/003119) . The person skilled in the art readily understands that an improvement in average volume and hardness in the NBR nitrile rubber seal swell test does not automatically lead to a general increase in other seal compatibility properties (such as tensile strength and elongation rupture in the NBR nitrile rubber test or properties as measured using a different material than used in the above NBR nitrile rubber seal swell test) . Furthermore, WO 2006/003119 focuses on crankcase gear oil applications and hydraulic fluids, rather than on

internal combustion engine oils such as diesel engine oils.

There are no particular limitations regarding the base oil used in the lubricating composition according to the present invention (provided that the base oil

comprises at least a Fischer-Tropsch derived base oil and a mineral derived Group I base oil) , 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 Fischer-Tropsch derived base oil and mineral derived Group I 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 Fischer-

Tropsch derived base oil and one mineral derived Group I and/or Group II 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, Group IV poly-alpha olefins (PAOs) , Group III Fischer-Tropsch derived base oils 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 category I and II. These API categories are defined in API Publication 1509,

15th Edition, Appendix E, April 2002.

A mineral derived Group I base oil typically has a Viscosity Index in the range from 95 to 105 and typically contains less than 90 wt . % saturates {according to ASTM D 2007) and at least 0.03 wt.% sulphur {according to ASTM D

1552). A mineral derived Group II base oil typically contains more than 90 wt.% saturates (according to ASTM D 2007) and at most 0.03 wt.% sulphur {according to ASTM D 1552) .

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 C₁₆, 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 {Group IV) PAO base oil, in view of the high cost of manufacture of the PAOs .

Thus, preferably, not more than 5 wt.%, preferably not more than 2 wt.%, of the base oil is a PAO base oil. It is even more preferred that no PAO base oil is present.

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.%, based on the total weight of the lubricating composition.

Preferably, as the mineral derived base oil, a Group

I base oil is used. If present, the mineral derived Group

II base oil is present in an amount of 0.1 - 80 wt.%, preferably in an amount below 60 wt.%, based on the total weight of the lubricating composition.

According to a preferred embodiment of the present invention, the composition comprises from 30.0 to 80.0 wt.%, preferably from 40.0 to 60.0 wt.% of the mineral derived Group I base oil, based on the total weight of the composition. Also it is preferred that the

composition comprises from 10.0 to 40.0 wt.%, preferably from 15.0 to 35.0 wt.%, of a Fischer-Tropsch derived base oil, based on the total weight of the lubricating

composition.

In a preferred embodiment according to the present invention, the Fischer-Tropsch derived base oil has a kinematic viscosity at 100°C (according to ASTM D 445) of between 2.0 and 9.0 cSt, preferably between 2.5 and 5.5 cSt..

Preferably, the lubricating composition according to the present invention meets the so-called SAE J300

Specifications (as revised in January 2009) , preferably xW-y formulations wherein x represents 10 or 15 and y represents 30 or 40. SAE stands for Society of Automotive Engineers. There is special preference for 15W-40, 10W-30 and 10W40 crankcase engine oils, and in particular 15W40.

It is preferred according to the present invention that the composition has a dynamic viscosity at -20°C (according to ASTM D 5293) of below 7000 cP (1 cP is the same as 1 mPa.s). Typically, the dynamic viscosity at - 20°C of the composition is between 3000 and 7000 cP.

The kinematic viscosity at 100 °C of the composition according to the present invention is below 26.1 cSt. It is preferred that the composition has a kinematic

viscosity at 100°C (according to ASTM D 445} of at least 5.6 cSt, preferably at least 9.3 cSt, more preferably at least 12.5 cSt. Typically, the kinematic viscosity at 100°C of the composition is between 5.6 and 26.1 cSt, preferably below 16.3.

Further it is preferred that the composition has a high temperature, high shear viscosity ("HTHS"; ^' according to ASTM D 4683) of at least 2.9 cP, preferably 3.5 cP. Typically, the HTHS of the composition is between 2.9 and 4.5 cP.

Typically, the Noack volatility (according to ASTM D 5800) of the composition is between 1 and 18.0 wt.%, preferably below 15.0 wt.%, more preferably below

13.0 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. Further examples of suitable additives are disclosed in e.g. US 2008/0153722, the teaching of which is hereby incorporated by specific reference .

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.

According to an especially preferred embodiment, the lubricating composition according to the present

invention comprises at least 1.0 wt.%, preferably at least 2.5 wt.%, of a detergent and/or dispersant, 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 preferably are 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 SAPS ranges mean:

- a sulphated ash content (according to ASTM D 874) of up to 1 wt.% (low SAPS), up to 1.5 wt.% (mid SAPS) and up to 2 wt.% (regular SAPS), respectively;

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

- a sulphur content (according to ASTM D 5185) of up to 0.3 wt.% (low SAPS), up to 0.4 wt.% (mid and regular SAPS in Group II/II base oils) and over 1.0 wt.% (mid and regular SAPS in Group I base oil) respectively.

Most preferably the lubricating compositions

according to the present invention are low SAPS Duty Diesel Engine Oils.

The lubricating composition according to the present invention may meet the above SAPS ranges for engine oils, even if the lubricating composition is intended for a different application.

In another aspect the present invention provides the use of the lubricating composition according to the present invention in order to improve one or more of the following properties:

- seal compatibility properties as determined by one or more of AK6 and ACM E7503, in particular according to the VDA 675301 Daimler specification;

- dispersancy; and

- pumpability.

In a further aspect the present invention provides the use of a Fischer-Tropsch derived base oil as defined in the present invention in order to improve one or more of the following properties:

- seal compatibility properties as determined by one or more of NBR34, AK6, ACM E7503 and EAM D8948-200,

in particular according to the VDA 675301 Daimler

specification;

- dispersancy; and

- pumpability.

Although the present invention is not limited to a certain type of lubricant, the present invention is of special use as an engine oil in internal combustion engines and more in particular compression ignition engines for transportation and other means of energy generation. Compression ignition engines, or "diesel engines", feature among the main type of engines employed for passenger cars in Europe, and globally for heavy-duty applications, as well as for stationary power generation as a result of their high efficiency. A diesel engine is an internal combustion engine; more specifically, it is a compression ignition engine, in which the fuel/air mixture is ignited by being compressed until it ignites due to the temperature increase due to compression, rather than by a separate source of ignition, such as a spark plug, as is the case of gasoline engines.

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 Compositions

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

Table 1 indicates the composition and properties of the fully formulated engine oil formulations that were tested; the amounts of the components are given in wt.%, based on the total weight of the fully formulated

formulations .

All tested engine oil formulations contained a combination of a base oil, an additive package, and a viscosity modifier, which additive package was the same in all tested compositions.

The additive package contained a combination of additives including anti-oxidants, a zinc-based anti-wear additives, an ashless dispersant, more than 1.0 wt.% of an overbased detergent mixture, about 0.2 wt.% of a pour point depressant and about 30 ppm of an anti-foaming agent .

A conventional viscosity modifier concentrate was used to adjust the viscosities.

"Base oil 1" was a Fischer-Tropsch derived base oil ( "GIL 4") having a kinematic viscosity at 100°C {ASTM

D445) of approx. 4 cSt (mm²s^_1) . This GTL 4 base oil may be conveniently manufactured by the process described in e.g. WO-A-02/070631, the teaching of which is hereby incorporated by reference.

"Base oil 2 ", "Base oil 3" and "Base oil 4" were mineral derived Group I base oils having a kinematic viscosity at 100°C {ASTM D445) of approx. 5 cSt {mm²s^_1) , 8 cSt and 11 cSt, respectively, commercially available from e.g. Shell Base Oils under the trade designations "HVI 60", "HVI 105" and "HVI 160S". "Base oil 5" and "Base Oil 6", were mineral derived Group II base oils having a kinematic viscosity at 100°C (ASTM D445) of approx, 6 cSt (mm²s^-1) and 12 cSt ,

respectively, commercially available from e.g. Motiva LLC (Port Arthur, Texas, USA} under the trade designations

"Star 6" and "Star 12".

The compositions of Examples 1-4 and Comparative Examples 1 and 2 were obtained by mixing the base oils with the additive package and viscosity modifier using conventional lubricant blending procedures. The

compositions of Examples 1-4 and Comparative Examples 1 and 2 meet the requirements of a 15W-40 formulation according to SAE J300.

According to ASTM D 5293. NB 1 cP (centi Poise) = 1 mPa.s

According to ASTM D 445

Seal Compatibility Test

In order to demonstrate the seal compatibility properties of the present invention, several measurements were performed according to the following standard tests according to the VDA 675301 Daimler specification:

- NBR34 (Nitryl) test (7 days at 100°C),

- AK6 (7 days at 150°C) ,

- ACM E7503 (7 days at 150°C), and

- EAM D8948-200 (7 days at 150°C).

The measured seal properties are indicated in Table

2 below.

Dispersancy Test

In order to demonstrate the soot dispersancy

properties of the lubricating compositions according to the present invention, measurements were performed as follows using an AR 500 rheometer available from TA

Instruments (New Castle, DE, USA} :

Carbon black {Vulcan XC72R, available from Cabot (Leuven, Belgium) ) was preheated in an oven at 140°C for at least 12 hours. 1.25 g of the carbon black and 25 g of oil sample were measured in a 150 ml bottle

(corresponding to 4.76 wt.% of carbon black). Then, a stirrer bar was added in the bottle and the bottle was closed with a lid. The bottle was placed on a heated stirrer block (at 100°C} to equilibrate overnight.

After stirring overnight, the mixture containing oil sample and carbon black was poured into the cup of the rheometer and heated to 100°C. When the mixture was achieved the temperature of 100 °C, the mixture was sheared at steady rate and the viscosity measured.

The measured dipersancy values for Examples 1 and 2 and Comparative Example 3 are indicated in Table 3 below and represented in attached Figure 1 as well.

Low Temperature Pumpability Test

In order to demonstrate the low temperature

pumpability properties of the lubricating compositions according to the present invention, measurements were performed as described in SAE paper 2000-01-1989, except for that the test was performed at -20 °C {instead of - 15 °C) . The measured pumpability values (flow times [in seconds] in Cummins M-ll at -20°C from oil sump to each part in engine) for Example 1 and Comparative Example 3 are indicated in Table 4 below.

Table 4

Discussion

As can be learned from Table 2, the seal

compatibility properties for Examples 1 and 2 and

Comparative Examples 1 and 2 (all containing a

combination of a Fischer-Tropsch derived base oil and a mineral derived Group I or Group II base oil) were significantly improved when compared with Comparative

Examples 3 and 4 (only containing mineral derived Group I or II base oils) . In particular it is to be noted that Comparative Example 3 (containing mineral derived Group I base oils} did not pass the tensile strength part of the AK6 test (- 52.3%; beyond the limit of -50% min) , whilst Examples 1 and 2 {containing a combination of Fischer-Tropsch derived base oil and mineral Group I base oil) did pass. The tensile strength gives a good impression of the extent to which the mechanical properties of a test specimen change upon contact with lubricant; a large % means better results.

Also, Examples 1 and 2 exceeded Comparative Example 3 significantly in the NBR34 test with respect to volume change (2.0 and 2.5 versus 3.4) and tensile strength (2.8 and 0.4 versus -3.6); in the ACM E7503 test with respect to volume change (1.5 and 2.5 versus 3.4) and tensile strength (3.5 and 2.8 versus -1.4); and in the EAM D8948- 200 test with respect to hardness (2 and 0 versus -3) and volume change (2.9 and 6.1 versus 10.3). Seal swell or shrinkage can have an effect on the sealing performance; a minimal change in volume upon contact with lubricant is desired to ensure the seal gives the fit for which it is designed.

Further, Comparative Examples 1 and 2 (containing a combination of Fischer-Tropsch derived base oil and mineral Group I base oil) exceeded Comparative Example 4

(containing mineral derived Group II base oil)

significantly in the ACM E7503 test with respect to volume change (1.7 and 1.8 versus 2.4) and in the EAM D8948-200 test with respect to hardness (5 and 4 versus 2) and volume change (0.8 and 1.8 versus 4.8).

From the tensile strength values as determined in the ACM E7503 test, it can be established that the advantage of the present invention is more pronounced in compositions containing a combination of a Fischer- Tropsch derived base oil and a mineral Group I base oil (Examples 1 and 2) than in a combination of a Fischer- Tropsch derived base oil and a mineral Group II base oil (Comparative Examples 1 and 2) . Therefore, the present invention has found a surprising preference in using a mineral Group I base oil over a mineral Group II base oil, when combined with a Fischer-Tropsch derived base oil .

As can be seen from Table 3 and Figure 1, the lubricating compositions according to the present

invention also exhibited good dispersancy properties. Table 3 and Figure 1 show that Example 1 and 2 perform better than Comp. Ex. 3, whilst there is a preference for Example 1 in respect of dispersancy properties. Further, as can be seen from Table 4, the lubricating compositions according to the present invention further exhibited improved low T pumpability properties (as evidenced by high reduction rates} .

Claims

C L A I M S

1. A lubricating composition comprising a base oil and one or more additives, the lubricating composition comprising at least:

- from 40.0 to 60.0 wt.% of a mineral derived Group I base oil, based on the total weight of the lubricating composition, and

wherein the lubricating composition has a kinematic viscosity at 100°C (according to ASTM D 445} of below 26.1 cSt.

2. Lubricating composition according to claim 1, wherein the composition comprises from 15.0 to 35.0 wt.%, of the Fischer-Tropsch derived base oil, based on the total weight of the lubricating composition.

3. Lubricating composition according to any of the preceding claims, having a dynamic viscosity at -20°C (according to ASTM D 5293) of below 7000 cP.

4. Lubricating composition according to any of the preceding claims, having a kinematic viscosity at 100°C (according to ASTM D 445) of at least 5.6 cSt, preferably at least 12.5 cSt and preferably below 16.3 cSt.

5. Lubricating composition according to any of the preceding claims, having a high temperature, high shear viscosity ("HTHS"; according to ASTM D 4683) of at least 2.9 cP, preferably at least 3.5 cP.

6. Lubricating composition according to any of the preceding claims, comprising at least 1.0 wt.%,

preferably at least 2.5 wt.%, of a detergent and/or dispersant, based on the total weight of the lubricating composition .

7. Use of the lubricating composition according to any of the preceding claims in order to improve one or more of the following properties:

- seal compatibility properties as determined by one or more of AK6 and ACM E7503, in particular according to the

VDA 675301 Daimler specification;

- dispersancy; and

- pumpability .