The present invention relates to an additive

concentrate comprising a base oil and a viscosity modifier, for the incorporation into a lubricant

composition .

Lubricant compositions, in particular for automotive crankcase or transmissions, are employed to reduce wear at metal-to-metal contact between moving parts, as well as to remove heat. In many applications, the lubricant compositions require the presence of polymeric viscosity modifier additives to obtain the desired viscometric properties over a broad range of shear and/or

temperatures. These additives are usually highly viscous liquids or solids at room temperature. In order to be able to achieve homogenous distribution, avoid handling of solids and to be able to administer the amounts of additives added into lubricant compositions and thus ensure consistent product quality, these additives are usually added as an additive concentrate.

Example 6 of US 2005/0133407 discloses a OW-20 engine oil (i.e. a fully formulated lubricating composition, not an additive concentrate) containing 86.30 wt . % of a Fischer-Tropsch derived base oil, 0.3 wt . % of a pour point depressant and 13.4 wt . % of a PCMO DI additive package. As is clear from paragraph [0147] of US

2005/0133407, the OW-20 formulation of Example 6 does not contain a viscosity index improver.

Example 3 of WO 02/064710 discloses a 0W30 engine oil (i.e. a fully formulated lubricating composition, not an additive concentrate), containing 76.4 wt . % of a Fischer- Tropsch derived product, 14.6 wt . % of a detergent inhibitor additive package, 0.25 wt . % of a corrosion inhibitor and 10.56 wt . % of a viscosity modifier.

Example 2 of EP 1 688 476 Al discloses a lubricating composition (i.e. not an additive concentrate) containing 18 wt . % of an additive package (see Example 1 of EP 1 688

476 Al) blended with (90% x 82 wt . % =) 73.8 wt . % of a Fischer-Tropsch derived base oil and (10% x 82 wt . % =) 8.2 wt . % of Emery 2925 (a triesterified polyol ester derived from C ₈ -Ci ₀ acids) available from Cognis

Corporation. As can be learned from Table II of US

2007/0093396, Emery 2925 has an aniline point (according to ASTM D 611) of 0°C and is therefore seen as a solvency booster as meant according to the present invention.

Example 7 of US 2009/0088352 discloses a lubricating composition (i.e. not an additive concentrate) prepared to meet the John Deere J20D specification, containing 86.81 wt . % Fischer-Tropsch derived base oil, 8.10 wt . % of an additive package, 4.94 wt . % of a viscosity modifier, 0.15 wt . % of a pour point depressant and 0.07 wt . % of a foam inhibitor.

As acknowledged in WO 2009/074572, Fischer-Tropsch derived base oils are usually not suitable as base oils to prepare additive concentrates for additives such as polymeric viscosity modifiers due to the low solvency of these Fischer-Tropsch derived base oils. Therefore,

WO 2009/074572 suggests to include an alkylated aromatic compound (e.g. "KR 008", commercially available from King Industries) as a solvency booster in the additive concentrate. According to WO 2009/074572, the solvency booster is preferably present in an amount of from

25 wt . % to 75 wt.%, based on the weight of the additive concentrate . The present applicant has now surprisingly found that it is possible to prepare additive concentrates

containing a viscosity modifier using Fischer-Tropsch derived base oils, which additive concentrates are suitable for use in e.g. transmission oils and engine oils and other lubricants (including industrial

lubricants such as hydraulic oils) for which a viscosity modifier is desired, but without the need of significant amounts of solvency boosters, or even without the need of solvency boosters at all.

To this end the present invention provides an additive concentrate comprising:

- at least 90 wt . % of a Fischer-Tropsch derived base oil, based on the total weight of the additive concentrate; - at least 3.0 wt . % of a viscosity modifier, based on the total weight of the additive concentrate; and

- less than 5.0 wt . % of a solvency booster, based on the total weight of the additive concentrate.

Fischer-Tropsch derived base oils are known in the art. In the present context, the term "Fischer-Tropsch derived" means that a material is, or derives from, a synthesis product of a Fischer-Tropsch condensation process. The term "non-Fischer-Tropsch derived" may be interpreted accordingly. A Fischer-Tropsch derived base oil will therefore be a hydrocarbon stream of which a substantial portion, except for added hydrogen, is derived directly or indirectly from a Fischer-Tropsch condensation process. A Fischer-Tropsch derived base oil may also be referred to as a GTL ( Gas-To-Liquids ) base oil. The term "base oil" may refer to a mixture

containing more than one base oil.

For further information on the Fischer-Tropsch derived base oil and the preparation thereof reference is made to the above-mentioned WO 2009/074572, the teaching of which is hereby incorporated by specific reference.

Typically, the aromatics content of a Fischer-Tropsch derived base oil, suitably determined by ASTM D 4629, will typically be below 1 wt.%, preferably below 0.5 wt . % and more preferably below 0.1 wt.%. Suitably, the base oil has a total paraffin content of at least 80 wt.%, preferably at least 85, more preferably at least 90, yet more preferably at least 95 and most preferably at least 99 wt.%. It suitably has a saturates content (as measured by IP-368) of greater than 98 wt.%. Preferably the saturates content of the base oil is greater than

99 wt.%, more preferably greater than 99.5 wt.%. It further preferably has a maximum n-paraffin content of 0.5 wt . % . The base oil preferably also has a content of naphthenic compounds of from 0 to less than 20 wt.%, more preferably of from 0.5 to 10 wt.%.

Typically, the Fischer-Tropsch derived base oil has a kinematic viscosity at 100°C (as measured by ASTM D 7042) of from 1 to 25 mm^/s (cSt), preferably above 2.5 more preferably above 3.0 mm^/s. Preferably, the Fischer- Tropsch derived base oil has a kinematic viscosity at 100°C of below 5.0 mm ² /s, preferably below 4.5 mm ² /s, more preferably below 4.2 mm ² /s.

Further, the Fischer-Tropsch derived base oil typically has a kinematic viscosity at 40°C (as measured by ASTM D 7042) of from 10 to 100 mm ² /s (cSt), preferably from 15 to 50 mm^/s.

Also, the Fischer-Tropsch derived base oil preferably has a pour point (as measured according to ASTM D 5950) of below -30°C, more preferably below -40°C, and most preferably below -45°C. The flash point (as measured by ASTM D92) of the Fischer-Tropsch derived base oil is preferably greater than 120°C, more preferably even greater than 140 °C.

The Fischer-Tropsch derived base oil preferably has a viscosity index (according to ASTM D 2270) in the range of from 100 to 200. Preferably, the Fischer-Tropsch derived base oil has a viscosity index of at least 125, preferably 130. Also it is preferred that the viscosity index is below 180, preferably below 150.

In the event the Fischer-Tropsch derived base oil contains a blend of two or more Fischer-Tropsch derived base oils, the above values apply to the blend of the two or more Fischer-Tropsch derived base oils.

In addition to the Fischer-Tropsch derived base oil, the additive concentrate may comprise one or more non-

Fischer-Tropsch derived base oils, such as mineral derived base oils and so-called synthetic base oils (such as PAOs) including Group I-V base oils according to the definitions of American Petroleum Institute (API). These API categories are defined in API Publication 1509, 15th

Edition, Appendix E, July 2009.

Preferably the additive concentrate according to the present invention comprises at least 80 wt . % of the Fischer-Tropsch derived base oil, preferably at least 90 wt.%, based on the total weight of the additive concentrate. Also it is preferred that the additive concentrate comprises less than 10.0 wt.% of a non-FT- derived base oil, preferably less than 5.0 wt.%, more preferably less than 2.0 wt.%, even more preferably less than 1.0 wt.%, based on the total weight of the additive concentrate. Most preferably the additive concentrate comprises no non-Fischer-Tropsch derived base oils at all . There are no particular limitations regarding the viscosity modifier as used in the additive concentrate according to the present invention. As a person skilled in the art is familiar with the term "viscosity

modifier", this is not further discussed in detail.

Viscosity modifiers (also known as VI improvers,

viscosity index improvers or viscosity improvers) provide lubricants with high- and low-temperature operability; these additives impart acceptable viscosity at low temperatures and are preferably shear stable. Typically, and as meant according to the present invention, a viscosity modifier improves (e.g. by at least 5 units) the viscosity index (e.g. as determined by ASTM D 2270) by its incorporation in the additive concentrate (and/or a fully formulated lubricant composition in which the viscosity modifier is incorporated) .

According to the present invention, the additive concentrate comprises at least 3.0 wt . % of a viscosity modifier, based on the total weight of the additive concentrate. Preferably, the additive concentrate comprises at least 5.0 wt . % such as from 5.0 to 10.0 wt.%, preferably from 6.0 to 10.0 wt . % of the viscosity modifier, based on the total weight of the additive concentrate .

Non-limiting Examples of viscosity modifiers are linear or star-shaped olefin copolymers,

polyisobutylenes , polymethacrylates , polymers of a diene such as isoprene or butadiene, or a copolymer of such a diene with optionally substituted styrene. These

copolymers are preferably hydrogenated to such an extent as to saturate most of the olefinic unsaturation . A number of other types of viscosity modifier are known in the art, and many of these are described in Proceedings of Conference "Viscosity and flow properties of

multigrade engine oils", Esslingen, Germany, December 1977. It is also known in the art that viscosity

modifiers can be functionalised to incorporate

dispersancy (e.g. dispersant viscosity index improvers based on block copolymers, or polymethacrylates ) and/or antioxidant functionality as well as viscosity

modification and they can also have pour point

depressants mixed in to give handleable products in cold climates .

Preferably, the viscosity modifier is selected from the group consisting of olefin copolymers, polyisoprene polymers and diene-styrene copolymers. Olefin copolymers are commercially available from Chevron Oronite Company LLC under the trade designation "PARATONE®" (such as

"PARATONE® 8921" and "PARATONE® 8941") ; from Afton

Chemical Corporation under the trade designation "HiTEC®" (such as "HiTEC® 5850B"; and from The Lubrizol

Corporation under the trade designation "Lubrizol®

7067C". Polyisoprene polymers are commercially available from Infineum International Limited, e.g. under the trade designation "SV200"; diene-styrene copolymers are commercially available from Infineum International

Limited, e.g. under the trade designation "SV 260".

The additive concentrate according to the present invention comprises less than 5.0 wt . % of a solvency booster, based on the total weight of the additive concentrate. Preferably, the additive concentrate comprises less than 2.0 wt.%, preferably less than 1.0 wt.%, more preferably less than 0.5 wt.%, of the solvency booster, based on the total weight of the additive concentrate. It is even more preferred that the additive concentrate contains no solvency booster at all. There are no particular limitations regarding the solvency booster as meant according to the present invention. As a person skilled in the art is familiar with the term "solvency booster", this is not further discussed in detail. Typically, and as meant according to the present invention, a solvency booster is a compound having an aniline point (according to ASTM D 611) of less than 100°C.

Preferably, the solvency booster is an alkylated aromatic compound. Alkylated aromatic compounds include alkylated benzenes, alkylated anthracenes, alkylated phenanthrenes , alkylated biphenyls, and alkylated naphthalenes or any mixtures thereof. For further description of the alkylated naphthalenes, reference is made to WO 2009/074572.

The additive concentrate may further contain a pour point depressant to improve pumpability. If present, the pour point depressant preferably is present in a range of from 0.5 to 3 wt.%, more preferably from 1 to 2 wt.%, and most preferably from 1.1. to 1.4 wt.%.

The additive concentrate preferably has - when normalized at a concentration of viscosity modifier of 1.0 wt.% - a dynamic viscosity at -30°C (according to ASTM D 5293) of below 3000 cP and a kinematic viscosity at 100°C (according to ASTM D 7042) of at least 5.5 cSt .

Preferably the dynamic viscosity at -30°C is below

2000 cP, more preferably below 1500 cP . Additive

concentrates containing different amounts of viscosity modifier can be normalized to a concentration of 1.0 wt.% by diluting the concentrate with the appropriate amount of the same base oil (or base oil blend) used to make the additive concentrate. Further it is preferred that the additive concentrate comprises from 5 to 500 ppm of an anti-oxidant,

preferably selected from a phenolic and an aminic antioxidant, or a mixture thereof.

In a further aspect the present invention provides a lubricant composition comprising a base oil, one or more additives other than a viscosity modifier and the additive concentrate according to the present invention.

There are no particular limitations regarding the base oil as used in the lubricant composition according to the present invention. This base oil may be a Fischer- Tropsch derived base oil, a non-Fischer-Tropsch derived base oil or a mixture thereof.

The one or more additives other than a viscosity modifier may be selected from a broad range of additives such as anti-oxidants , anti-wear additives, dispersants, detergents, over-based detergents, extreme pressure additives, friction modifiers, 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.

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

Additive Concentrates

Various additive concentrates were formulated.

Table 1 indicates the properties for the base oils used in the additive concentrates. Tables 2-5 indicate the composition and properties of the formulated additive concentrates that were tested; the amounts of the components are given in wt.%, based on the total weight of the additive concentrate. Table 6 exemplifies the storage stability properties of an additive concentrate according to the present invention. Further, Table 7 exemplifies a fully formulated lubricating compositions (i.e. a SAE 5W-30 engine oil), comprising the additive concentrate according to the present invention.

The viscosities and Viscosity Index as measured for the additive concentrates were all measured at a normalized Viscosity Modifier concentration of 1.0 wt.% by dilution with the same base oil used to blend the additive concentrate (as the neat concentrates were too thick and therefore outside the testing range of the indicated test methods) .

All tested additive concentrates contained a combination of a base oil and a viscosity modifier, and optionally an anti-oxidant .

"Base oil 1" was a Fischer-Tropsch derived base oil ("GTL 4") having a kinematic viscosity at 100°C (ASTM D 7042) of approx. 4 cSt (mm ² /s) . 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 " was a commercially available Group I base oil having a kinematic viscosity at 100°C (ASTM D 7042) of approx. 4 cSt . Base oil 2 is commercially available from ExxonMobil Corporation under the trade designation "Americas SN 115".

"Base oil 3" was a commercially available Group II base oil having a kinematic viscosity at 100°C (ASTM D 7042) of approx. 4.7 cSt . Base oil 3 is commercially available from Motiva Enterprises LLC under the trade designation "Star 5+".

"Base oil 4" was a commercially available Group II base oil having a kinematic viscosity at 100°C (ASTM D

7042) of approx. 6.5 cSt. Base oil 4 is commercially available from Motiva Enterprises LLC under the trade designation "Star 6".

"VMl" was a commercially available olefin copolymer viscosity modifier available from Chevron Oronite Company

LLC (Richmond, California, USA) under the trade

designation "PARATONE® 8921".

"VM2" was a commercially available olefin copolymer viscosity modifier available from Afton Chemical

Corporation (Richmond, Virginia, USA) under the trade designation "HiTEC® 5850B".

"VM3" was a commercially available olefin copolymer viscosity modifier available from The Lubrizol

Corporation (Wickliffe, Ohio, USA) under the trade designation "Lubrizol® 7067C".

"VM4" was a commercially available polyisoprene polymer viscosity modifier available from Infineum

International Limited (Linden, New Jersey, USA) under the trade designation "SV 200".

"VM5" was a commercially available diene-styrene copolymer viscosity modifier available from Infineum International Limited under the trade designation "SV 260".

"Anti-oxidant" was a commercially available aminic anti-oxidant available from Ciba Corporation (Houston,

Texas, USA) under the trade designation " Ciba® IRGANOX® L57" . The compositions of Example 1-8 and Comparative Examples 1-8 were obtained by mixing the base oils with the viscosity modifier using a Silverson high shear mixer and following (conventional) blending procedures

recommended by the suppliers of the Viscosity Modifiers.

TABLE 1

According to ASTM D 5293

² According to ASTM D 7042

³ According to ASTM D 2270

According to ASTM D 611

⁵ According to ASTM D 5950

⁶ According to ASTM D 5800B

⁷ According to IP 368 (modified)

TABLE 2 - Additive concentrates containing VMl

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

According to ASTM D 7042

³ According to ASTM D 2270

TABLE 3 - Additive concentrates containing VM2

According to ASTM D 5293

According to ASTM D 7042

3According to ASTM D 2270

TABLE 4 - Additive concentrates containing VM3

According to ASTM D 5293

According to ASTM D 7042

3According to ASTM D 2270

*Not according to the present invention

TABLE 5 - Additive concentrates containing VM4 or VM5

According to ASTM D 5293

According to ASTM D 7042

3According to ASTM D 2270

*Not according to the present invention

Storage Stability

In order to demonstrate the storage stability properties of the additive concentrates according to the present invention, separate samples of the additive concentrate of Example 1 were stored for 30 days at temperatures of 70°C, ambient (20°C), 0°C and -20°C, respectively. The measured viscosities after 30 days of storage are indicated in Table 6 below. Similar good stability properties were obtained for the additive concentrates of Examples 2-8.

TABLE 6 - Storage stability of additive concentrate of Example 1

According to ASTM D 5293

According to ASTM D 7042

According to ASTM D 2270

SAE 5W30 engine oils

Whilst using the additive concentrates of Example 2 and 4 above and a conventional additive package, two SAE 5W-30 engine oil formulations (Examples 9 and 10) were prepared meeting the so-called SAE J300 Specifications

(as revised in January 2009) . SAE stands for Society of Automotive Engineers.

The amounts of the components and the properties of the 5W-30 engine oil are indicated in Table 7 below.

The additive package contained a pour point depressant and other typical additives for use in a SAE 5W-30 engine oil.

TABLE 7 - SAE 5W-30 engine oils

According to ASTM D 5293

According to ASTM D 7042

3According to ASTM D 2270

According to ASTM D 4684

According to ASTM D 4683 Discussion

As can be learned from Tables 2-5, the present invention now surprisingly provides the possibility to prepare additive concentrates containing a viscosity modifier using Fischer-Tropsch derived base oils, but without significant amounts of solvency boosters or even without the use of solvency boosters at all. Also, it can be seen that the additive concentrates according to the present invention show, when compared with conventional additive concentrates using mineral derived Group I (i.e. non-Fischer-Tropsch derived) base oils, significantly better low temperature properties, which is highly desirable for formulating multi-grade lubricants.

Furthermore, as exemplified by Table 6, the additive concentrates according to the present invention have excellent storage stability at various temperatures for extended periods of time.

The additive concentrates according to the present invention are suitable for use in a wide range of lubricants, such as in e.g. engine oils and transmission fluids and other lubricants for which a viscosity modifier is desired. As shown in Table 7, SAE 5W-30 formulations can be formulated when using the additive concentrates according to the present invention.