TREA

Lubricating Oil Composition

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Information

  • Patent Application
  • 20080020951
  • Publication Number
    20080020951
  • Date Filed
    July 10, 2007
    17 years ago
  • Date Published
    January 24, 2008
    17 years ago
Information
Abstract
A lubricating oil composition for a heavy duty diesel engine comprises a base oil, at least 0.6 mass % of an ash-free antioxidant and an overbased magnesium-containing detergent. The detergent provides greater than 0.05 mass % Mg based on the mass of the composition. Bore polishing in the engine is reduced for a given level of exhaust gas ash production.
Description

A first aspect of the present invention provides, a lubricating composition for a diesel engine, particularly a heavy duty diesel engine (“HDD”), comprising the following components:

    • (a) a lubricating oil basestock of lubricating viscosity;
    • (b) an antioxidant component;
    • (c) a detergent component;


optionally (d) one or more metal hydrocarbyl dithiophosphate compounds in an amount of from 0.0 to 1.8 mass %; wherein the antioxidant component (b) is selected from one or more ash-free aminic and/or sulfur-free phenolic compounds in an amount of at least 0.6 mass % and up to 3.0 mass % based on the total mass of the lubricating composition; and the detergent component (c) is an overbased magnesium compound having a total base number (TBN) exceeding 350 mg/g KOH selected from one or more magnesium sulfonates, magnesium salicylates, magnesium phenates and which provide the composition with greater than 0.05 mass % Mg based on the mass of the composition and optionally a calcium detergent compound, and wherein the sulfated ash content of the composition is at least 0.6 mass % and not more than 2.0 mass % as determined by ASTM D874.


A second aspect of the present invention provides a method of operating a heavy duty diesel engine which comprises lubricating the engine with a lubricating oil composition according to the first aspect.


A third aspect of the invention provides a method of reducing bore polishing in a heavy duty diesel engine, which method comprises lubricating the engine with a lubricating oil composition according to the first aspect.


The base oil is an oil of lubricating viscosity and may have characteristics in the following ranges. The base oil contains one or more of Groups I, II, III or IV base stocks as defined in API Engine Oil Licensing and Certification System (EOLCS), Industry Services Department, 14th edition, December 1996, Addendum 1, Dec. 1998 and ATIEL code. The base oil sulphur content may be between 0.00 and 1.00 wt. % and the KV @100° C. may be from 3.8 mm2/s to 21.9 mm2/s. More preferably the base oil sulphur content may be from 0.00 to 0.80 wt. % and the KV @100° C. may be from 3.8 mm2/s to 8.0 mm2/s.


The antioxidant component may be one or more of an amine or an aminic compound and/or a sulfur-free phenol or a sulfur-free phenolic compound. Suitable amines include (but are not restricted to) Irganox L67 and Irganox L57 available from Ciba and Naugalube 438L available from Chemtura. Suitable sulfur-free phenols include (but are not restricted to) Irganox L135 available from Ciba and HITEC 4782 and 4727 available from Afton Chemicals. “Irganox”, “Naugalube” and “HITEC” are trade-names.


The one or more antioxidant component comprise at least 0.6 mass % of the lubricating oil composition, based on the total mass of the lubricating oil composition. Suitably the one or more antioxidant components provide at least 0.75 mass % of the lubricating oil compositions based upon the total mass of the lubricating oil composition. The one or more antioxidant components comprise up to 3.0 mass % of the lubricating oil composition based upon the total mass of the lubricating oil composition. The one or more antioxidant components suitably provide up to 2.75 mass % of the lubricating oil composition, based upon the total mass of the lubricating oil composition.


Suitably, the lubricating oil composition comprises only ash-free antioxidant components.


The overbased magnesium compound provides the composition with greater than 0.05 mass % Mg, based upon the mass of the composition. Suitably, the magnesium compound provides the composition with at least 0.06 mass % Mg, based on the mass of the composition. The magnesium compound may provide the composition with at least 0.063 mass % Mg, based upon the mass of the composition. Suitably, the overbased magnesium compound provides the composition with no more than 0.3 mass % Mg, based upon the mass of the composition. The Mg content of the composition is suitably up to 0.15 mass %, based upon the mass of the composition. The composition suitably comprises up to 0.14 mass % Mg from the magnesium compound, based upon the total mass of the composition.


Lubricating compositions according to the invention may have a TBN (total base number as determined by ASTM D2896) of at least 8.0, preferably 9.0 or higher. The maximum TBN is not likely to exceed 20.0, and 15.0 may be regarded as a practical maximum TBN for many compositions.


Lubricating compositions according to the invention may comprise phosphorus moieties. The phosphorus moieties may be antiwear components such as one or more salts of one or more dihydrocarbyldithiophosphoric acids. A typical salt of a dihydrocarbyldithiophosphoric acid employed as an antiwear component is zinc dihydrocarbyldithiophosphate, ZDDP. The lubricating compositions may comprise phosphorus moieties from other components, such as certain phosphites which may be employed as antiwear components. Phosphorus may be present in the lubricating compositions (e.g. from ZDDP) in amounts up to 2000 ppm by mass. The maximum phosphorus level is preferably lower, e.g. 1400 ppm or less, such as 1200 ppm or 1000 ppm. The minimum phosphorus level is zero, but may be 80 ppm by mass or higher, e.g. 100 ppm. Phosphorus levels in the range of 200 to 800 ppm may be used in lubricating compositions according to the invention. Suitably, the amount of phosphorous provided by the metal hydrocarbyl dithiophosphate is in the range of 0.05 to 0.20 mass %, based on the mass of the composition.


Lubricating compositions according to the present invention may optionally comprise additional additives, including one or more dispersants. The one or more dispersants are suitably nitrogen containing dispersants. The one or more dispersants may provide the lubricating composition with at least 0.07 mass % nitrogen, based upon the mass of the composition. The one or more optional dispersants suitably provide the lubricating oil composition with between 0.07 to 0.25 mass % nitrogen, based upon the mass of the lubricating oil composition.


The sulphated ash content of the lubricating oil composition is at least 0.6 mass %, based upon the mass of the composition. The lubricating oil composition suitably has a sulphated ash content of at least 0.8 mass %, based on the mass of the composition. A lubricating oil composition according to the present invention suitably has a sulphated ash content of no lower than 1.0 mass %. A lubricating oil composition according to the present invention has a sulphated ash content of not more than 2.0 mass % based on the total mass of the composition. A lubricating oil composition according to the present invention may have a sulphated ash content no greater than 1.6 mass %, preferably no greater than 1.5 mass %, and more preferably no greater than 1.2 mass % based on the mass of the composition.


The invention is now further described with reference to some examples.


A number of lubricating oil compositions were formulated, all suitable for lubricating a heavy duty diesel engine. The compositions contained, inter alia, the following components:

    • (i) base oil
    • (ii) detergent;
    • (iii) dispersant
    • (iv) antioxidant
    • (v) anti-wear component


Some further details of the foregoing components are now provided:

    • (i) base oil: the base oils were hydrocarbon oil base stocks with a sulphur content of 0.0 to 0.8 wt. %, a Viscosity Index of 95 to 129 and a base blend KV @100° C. of 5 to 7 mm2/s.
    • (ii) detergents: the detergent components comprised a mixture of calcium sulphonate, calcium phenate, magnesium sulphonate and calcium salicylate. The combined calcium and magnesium content in the lubricating oil was in the range of from 0.18 to 0.36 mass %. All such detergents are commercially available materials from Infineum UK Ltd.
      • (a) The magnesium detergent was a magnesium sulfonate with a Mg content of 9.1 mass % and a TBN of 405.
    • (iii) dispersant: the ashless dispersants were polyisobutylenesuccinic anhydride-polyamine, usually known as PIBSA-PAM type dispersants. The combined N derived from the dispersant in the lubricating oil was 0.06 to 0.12 mass %. Such dispersants are commercially available from Infineum UK Ltd.
    • (iv) antioxidant: the antioxidant was an aminic component, referred to below as AntiOxidant A, and consisted of Irganox L67 (tradename) available from Ciba and/or Naugalube 438L (tradename) available from Chemtura, and/or a sulfur-free phenolic component, referred to below as AntiOxidant B, consisting of Irganox L135 (tradename) available from Ciba and/or HITEC 4782 (tradename) available from Afton Chemicals. For the purposes of the comparisons below, the concentration in weight % of each is based on 100% active ingredient material.
    • (v) anti-wear component: the antiwear component was zinc dihydrocarbyldithiophosphate (ZDDP), wherein the hydrocarbyl group(s) had carbon chain lengths of 4 and 8 and included primary and secondary alkyl groups. The ZDDP component used in the Examples had a phosphorous content of 8.0 mass %. This type of anti-wear component is commercially available from various sources.


The compositions also included components which are usually included in HDD lubricant compositions, such as one or more of the following: friction modifier, viscosity modifier, anti-foamant, demulsifier, pour point depressant (inter alia). Since these components are well-known and are not believed to be significant in relation to the bore-polishing benefits of the lubricating compositions of the invention, they will not be further discussed herein.


Lubricant oil compositions suitable for use with HDDs were formulated from the components (i) to (v) mentioned above, together with other well-known lubricant oil components. The oils were formulated in the well-known manner to have viscosity characteristics of 10W-40 or 15W-40. The lubricant viscosity was SAE 40 grade and all samples had an approximately equal kinematic viscosity at 100° C., thereby factoring out base stock effects and giving a robust comparison between the samples. The compositions had varied concentrations of the following components: the calcium and magnesium detergents, the dispersant, the antioxidant and the ZDDP antiwear component.


Samples of the thus formulated compositions were evaluated for bore polish characteristics in accordance with the well-known test: CEC-L-52-T-97 (OM441LA). The test method is available from the CEC (Coordinating European Council).


The results of the tests are shown in Table 1.









TABLE 1







Bore Polish Test Results - (Test Procedure according to CEC-L-52-T-97)












Low % Mg, Low AO**
High % Mg, Low AO**
High % Mg Oil, High AO**




PASSING Oil Bore Polish
Fail on Bore Polish
Pass on Bore Polish









Sample No.























1
2
3
4
5
6
7
8
9
10
11
12
13
14










Viscosity Grade























10W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
15W-
10W-




40
40
40
40
40
40
40
40
40
40
40
40
40
40











Formulation Summary (mass %)






















Ca
0.332
0.235
0.329
0.299
0.295
0.107
0.204
0.204
0.272
0.155
0.156
0.057
0.170
0.172



Mg
0.026
0.026
0.029
0.053
0.056
0.075
0.102
0.102
0.053
0.065
0.066
0.134
0.138
0.074


P
0.12
0.10
0.12
0.12
0.10
0.08
0.12
0.12
0.13
0.11
0.12
0.12
0.12
0.08


TBN*
13.0
10.1
11.6
11.7
11.1
8.3
12.2
12.2
12.5
9.8
9.5
11.2
14.3
12.2


Sulphated
1.4
1.1
1.4
1.5
1.4
0.8
1.3
1.3
1.4
1.0
1.0
1.0
1.4
1.0


Ash**


N derived
0.096
0.084
0.105
0.085
0.061
0.078
0.105
0.105
0.117
0.108
0.108
0.108
0.124
0.106


from


Dispersant


AntiOxidant -
0.30
0.30
0.00
0.00
0.00
0.40
0.00
0.00
0.39
0.00
0.00
0.00
0.90
1.50


A


AntiOxidant -
0.00
0.00
0.42
0.17
0.17
0.00
0.42
0.42
0.44
1.60
1.60
1.60
1.30
1.00


B



Total
0.30
0.30
0.42
0.17
0.17
0.40
0.42
0.42
0.83
1.60
1.60
1.60
2.20
2.50


Ashless


AO***







Engine Test CEC-L-52-T-97 (OM441LA)






















Pass/Fail
PASS
PASS
PASS
FAIL
FAIL
FAIL
FAIL
FAIL
PASS
PASS
PASS
PASS
PASS
PASS
LIM-


vs ACEA














IT


E7-04


Bore Polish
1.1
0.2
0.6
3.6
2.7
2.4
2.6
2.9
1.4
0.5
0.0
0.5
0.3
1.1
2.0

















max





*TBN refers to Total Base Number in mgKOH/g as measured by ASTM D2896.


**Sulphated Ash as measured by ASTM D874.


***AO = Anti-Oxidant






Referring to Table 1, oil samples 1, 2 and 3 are illustrative of compositions having low magnesium contents and low antioxidant contents. The magnesium contents are in the range of 0.26 to 0.29 mass %. The antioxidant contents are in the range of 0.30 to 0.42 mass %. The other components of these three samples are in concentrations which do not significantly affect the Bore Polish test results. A skilled person would know how to adjust the concentrations of the other components to achieve this effect. It is seen that the compositions all have bore polish results below the maximum limit (2.0) and that therefore, all of the samples 1, 2 and 3 pass the Bore Polish test.


Oil samples 4 to 8 are illustrative of compositions having high magnesium contents and low antioxidant concentrations. The samples have Mg concentrations in the range of 0.053 to 0.102 mass %, and antioxidant concentrations in the range 0.17 to 0.42 mass % (overlapping those of Samples 1 to 3). The other components of these five Samples are present in concentrations which do not significantly affect the Bore Polish results. A skilled person would know how to adjust the concentrations of these other components to achieve this effect. It is apparent from the Test Results for Samples 4 to 8 that high Mg concentrations and low antioxidant concentrations produce Bore Polish “Fail” results above the maximum limit (2.0), in the range of 2.4 to 3.6. It is also apparent that “Fail” results were still obtained in the range despite varying the principal anti-wear additive (ZDDP-A) from 0.08 to 0.12 wt. % P.


Reference is now made to the data in Table 1 for Samples 9 to 14. These Samples have high Mg concentrations and high antioxidant concentrations. The Mg concentrations are in the range 0.053 to 0.138 mass % and overlap the Mg concentrations of Samples 4 to 8. The antioxidant concentrations are in the range 0.83 to 2.50 mass %. The other components of these six samples are present in concentrations which do not significantly affect the Bore Polish results. A skilled person would know how to adjust the concentrations of the other components to achieve this effect. It is apparent from the Test Results for Samples 9 to 14 that high Mg concentrations in combination with high antioxidant concentrations produce Bore Polish “Pass” results below the maximum limit of 2.0, and in the range 0.0 to 1.4. This range is similar to the range for Samples 1, 2 and 3 despite the fact that Samples 9 to 14 comprise from about twice to about four times as much Mg. This result is surprising since it has previously been found that lubricating oils containing magnesium tend to have a reduced performance with respect to bore polishing.


Moreover, it is seen from the data in Table 1 that relatively high concentrations of magnesium can be employed in compositions according to the invention (e.g. Samples 9 to 14) without giving rise to unacceptably high or excessively high quantities of sulphated ash. For example, Samples 12 which comprises 0.057 mass % Ca and 0.134 mass % Mg gave rise to 1.0 mass % sulphated ash, lower than the sulphated ash obtained with the low and the high Mg oils of Samples 4, 5, 7 and 8.


Sample 13, comprising 0.170 mass % Ca and 0.138 mass % Mg, gave rise to 1.4 mass % sulphated ash, no higher than the ash obtained with low Mg Samples 1 and 3 and high Mg Samples 4 and 5, which all contain relatively higher levels of calcium that Samples 13.


Generally speaking, and as is apparent from Table 1, oil compositions according to the invention provide excellent performance in terms of bore polishing results without giving rise to unacceptable levels of sulphated ash.

Claims
  • 1. A lubricating oil composition for a diesel engine, comprising the following components: (a) a lubricating oil basestock of lubricating viscosity;(b) an antioxidant component;(c) a detergent component; and
  • 2. The composition of claim 1 wherein the Mg content does not exceed 0.3 mass % based on the total mass of the composition.
  • 3. The composition of claim 1 wherein the Mg content is at least 0.06 mass up to 0.15 mass % based on the total mass of the composition.
  • 4. The composition of claim 1 comprising one or more dispersants.
  • 5. The composition of claim 4 wherein the dispersant(s) include one or more nitrogen-containing dispersants.
  • 6. The composition of claim 5 wherein the nitrogen content provided by the nitrogen-containing dispersant(s) is at least 0.07 mass % based on the total mass of the composition.
  • 7. The composition of claim 6 wherein the nitrogen content provided by the nitrogen-containing dispersant(s) is in the range of from 0.07 to 0.25 mass %.
  • 8. The composition of claim 1 wherein the antioxidant component(s) consist of ash-free antioxidant compound.
  • 9. The composition of claim 1 having a sulfated ash content no lower than 0.8 mass %.
  • 10. The composition of claim 9 having a sulfated ash content no lower than 1.0 mass %, and no greater than 1.6 mass %.
  • 11. The composition of claim 10 having a sulfated ash content no lower than 1.0 mass %, and no greater than 1.5 mass %.
  • 12. The composition of claim 1 wherein the amount of phosphorus provided by the metal hydrocarbyl dithiophosphate is in the range of from 0.05 to 0.20 mass % based on the total mass of the composition.
  • 13. The composition of claim 1 wherein the detergent component (c) comprises salicylate detergent.
  • 14. A method of operating a heavy duty diesel engine comprising lubricating the engine with a lubricating oil composition according to claim 1.
  • 15. A method of reducing bore polishing in a diesel engine comprising lubricating the engine with a lubricating oil composition according to claim 1.
Priority Claims (1)
Number Date Country Kind
06117607.9 Jul 2006 EP regional