ENGINE LUBRICANTS FOR SILOXANE DEPOSIT CONTROL

Abstract

A zinc free or substantially zinc free lubricant having a sulfated ash content of less than about 1.0 percent and including (a) an oil of lubricating viscosity; (b) 0.03 to about 3.0 weight percent of a phosphite compound; (c) an metal containing detergent; (d) a polyisobutylene succinimide dispersant derived from an ethylene polyamine and having a carbonyl to nitrogen ratio equal or greater than 1; (e) at least one other dispersant; (f) a boron containing compound in amount to provide at least 25 ppm boron to the lubricant composition is useful for inhibiting siloxane deposits in a stationary gas engine fueled by natural gas having a high silicon concentration.

Claims

1. A method for lubricating a natural gas fueled, sump-lubricated, stationary gas engine comprising supplying to the engine a lubricant composition comprising: (a) an oil of lubricating viscosity; (b) 0.03 to about 3.0 weight percent with respect to the lubricant of a phosphite compound; (c) a metal containing detergent; (d) at least a first dispersant, wherein the first dispersant is a polyisobutylene succinimide dispersant derived from an ethylene polyamine and having a carbonyl to nitrogen ratio equal or greater than 1; (e) at least one other dispersant selected from the group consisting of a succinimide dispersant having a carbonyl to nitrogen ratio less than 1, a Mannich dispersant, a succinamide dispersant, and a polyisobutylene succinic acid ester dispersant; a boron containing compound in amount to provide at least 25 ppm boron to the lubricant composition; wherein the lubricant composition is free or substantially free of zinc, and wherein the lubricant composition has a sulfated ash content of less than about 1.0 wt. %.

2. The method of claim 1 wherein the phosphite compound comprises a phosphite ester selected from the group consisting of phosphite diesters, phosphite triesters and mixtures thereof.

3. The method of claim 1 wherein the phosphite compound comprises a phosphite having the following formula
(R.sup.1O).sub.3P wherein each le independently is hydrogen or a hydrocarbyl group having 1 to 36 carbon atoms.

4. The method of claim 1 wherein the phosphite compound comprises a phosphite diester having ester groups of 2 to 10 carbon atoms and a phosphite diester having ester groups of 12 to 30 carbon atoms.

5. The method of claim 1, wherein the phosphite compounds comprises dibutyl phosphite.

6. The method of claim 1 wherein the phosphite compound provides 0.001 wt. % to 0.05 wt. % phosphorus to the lubricant composition.

7. The method of claim 1, wherein the total amount of dispersant is 1.0 wt % to 6.0 wt. % of the lubricant composition.

8. The method of claim 1, wherein the first dispersant is present in an amount of 0.1 wt % to 2 wt % of the lubricant composition.

9. The method of claim 1, wherein the second dispersant comprises a succinimide dispersant having a carbonyl to nitrogen ratio less than 1.

10. The method of claim 1, wherein the metal containing detergent is selected from the group consisting of phenate detergents, sulphonate detergents, salicylate detergents, salixarate detergents, saligenin detergents and mixtures thereof.

11. The method of claim 1, wherein the metal containing detergent comprises a salicylate detergent.

12. The method of claim 1, wherein the salicylate detergent has a Total Base Number of about 200 to about 700 on an oil free basis.

13. The method of claim 1, wherein the metal of the metal containing detergent is selected from the group consisting of magnesium, and calcium and mixtures thereof.

14. The method of claim 1, wherein the lubricant composition comprises at least a third dispersant, wherein the third dispersant is a polyolefin succinic acid ester dispersant.

15. The method of claim 1, wherein the lubricant composition has a silicon concentration greater than 125 ppm.

16. The method of claim 1, wherein the engine is fueled by natural gas having a silicon concentration greater than about 10 mg/m.sup.3 as measured by gas chromatography mass spectrometry.

17. The method of claim 1, wherein the boron containing compound comprises a borate ester having at least one hydrocarbyl group of 8 to 30 carbon atoms.

18. The method of claim 1, wherein the boron containing compound comprises a borated dispersant.

19. The method of claim 1, wherein the lubricant composition has 50 to about 500 ppm phosphorus.

20-21. (canceled)

22. A lubricant comprising: (a) an oil of lubricating viscosity; (b) 0.03 to about 3.0 weigh percent with respect to the lubricant composition of a phosphite compound; (c) a metal containing detergent; (d) at least a first dispersant, wherein the first dispersant is a polyisobutylene succinimide dispersant derived from an ethylene polyamine and having a carbonyl to nitrogen ratio equal or greater than 1; (e) at least one other dispersant selected from the group consisting of a succinimide dispersant having a carbonyl to nitrogen ratio less than 1, a Mannich dispersant, and a polyolefin succinic acid ester dispersant; (f) a boron containing compound in amount to provide at least 25 ppm boron to the lubricant composition; wherein the lubricant composition is substantially free of zinc, wherein the lubricant composition has a sulfated ash content of less than about 1.0 percent.

Description

EXAMPLES

[0096] Reference Example 1 (RE1). A low-ash stationary-gas engine lubricant may be prepared comprising an oil of lubricating viscosity, 2.54 wt. % of a succinimide dispersant (chlorine-route); 0.74 wt. % of overbased Ca sulfonate detergent(s); 0.97 wt. % overbased Ca phenate detergent(s), 0.27 wt. % zinc dialkylthiophosphate(s); 2.85 wt. % antioxidants (phenolic, aminic, and/or sulfurized olefin); 0.35 wt. % of a borate ester, and 0.007 percent by weight of polydimethylsiloxane antifoam agent (commercial material, about 10% in oil, corresponding to 7 ppm antifoam agent on an active chemical basis).

[0097] Preparative Example 1 (PE1). A low-ash stationary-gas engine lubricant may be prepared comprising an oil of lubricating viscosity, 0.24 wt. % of a phosphite compound(s), 1.8 wt. % of a succinimide dispersant (chlorine-route); 0.6 wt. % of a polyisobutylene succinimide dispersant with a carbonyl to nitrogen ratio of 4:3, 0.34 wt.% of a borated succinimide dispersant, 0.28 wt. % succinic acid ester dispersant, 0.1 wt. % of a polypropylene oxide, 1.2 wt. % of overbased Ca salicylate detergent; 2.95 wt. % antioxidants (phenolic, aminic, and/or sulfurized olefin); 0.35 wt. % of a borate ester, 0.01 wt. % of a corrosion inhibitor, 0.05 wt. % of a titanium alkylate and 0.007 percent by weight of polydimethylsiloxane antifoam agent (commercial material, about 10% in oil, corresponding to 7 ppm antifoam agent on an active chemical basis).

[0098] Each of the documents referred to above is incorporated herein by reference. The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word about. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression consisting essentially of permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration.

[0099] As used herein, the term substantially free of means that the material in question is only present in amounts consistent with contamination and/or by-products present in commercial grades of desired components.

[0100] As used herein, the term hydrocarbyl substituent or hydrocarbyl group is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include hydrocarbon substituents, including aliphatic, alicyclic, and aromatic substituents; substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; and hetero substituents, that is, substituents which similarly have a predominantly hydrocarbon character but contain other than carbon in a ring or chain. A more detailed definition of the term hydrocarbyl substituent or hydrocarbyl group, including permissible amounts of other atoms, is found in paragraphs [0118] to [0119] of International Publication WO2008147704 as well as paragraphs [0137] to [0141] of published application U.S. 2010-0197536.