Carboxylated detergent-dispersant-containing compositions having improved properties in lubricating oils

Abstract

A lubricant additive composition comprising (a) a carboxylated detergent-dispersant obtained by (i) neutralizing alkylphenols using an alkaline earth base in the presence of at least one carboxylic acid that contains from one to four carbon atoms but in the absence of alkali base, dialcohol, and monoalcohol, forming an intermediate product, then (ii) carboxylating the intermediate product using carbon dioxide so that at least 20 mole percent of the original alkylphenol starting material has been converted to single aromatic-ring hydrocarbyl salicylate; and (b) an overbased, non-sulfonate-containing detergent such as, for instance, a hydrocarbyl phenate-carboxylate; a medium overbased salicylate having a total base number of about 50 to 170; a high overbased salicylate having a total base number greater than 170; or an overbased sulfurized hydrocarbyl phenate of alkaline earth metals; and combinations and mixtures thereof. Also provided for are additive packages and finished lubricating oil compositions comprising the same. The compositions of this invention reduce sludge and contaminant formation, especially in low and medium speed diesel engines and in marine diesel engines.

Description

[0001] This invention is directed, in part, to novel lubricant additive compositions comprising an unsulfurized, alkali metal-free, carboxylated detergent-dispersant, as well as additive packages and finished oil compositions comprising the same. The compositions, which combine the carboxylated detergent-dispersant with overbased, non-sulfonate-containin-g detergents, exhibit increased control of deposits in internal combustion engines, especially diesel engines, and most especially heavy marine and powerplant diesel engines compared to conventional compositions. This invention is also directed, in part, to methods for preparing novel additive compositions including the carboxylated detergent-dispersant and overbased non-sulfonate-containing detergents.REFERENCES[0002] The following references are cited in this application as superscript numbers:[0003] .sup.1Cane, European Patent Application 87310460.8, Alkaline earth metal hydrocarbyl phenates, their sulphurised derivatives, their ...

AI Technical Summary

Problems solved by technology

Contamination of lubricating oils, particularly for lubrication of internal combustion engines operating under severe conditions such as high blow-by gases or for engines operating on poor quality fuels is a recognized problem in the industry.

Lubricating oils contaminated with unburned residues lead to black paint deposits in piston undercrowns, as well as deposits and dirt in cam boxes and crankcases, in diesel engines.

The deposit and contamination problems occur with four stroke and two stroke engines.

Such fuels may contaminate lubricating oils either by leakage of the raw fuel or through blow-by gases entering the crankcase and causing dirt and deposits.

Contamination of lubricating oil in such a way makes the engine and oil highly prone toward forming deposits, often called black sludge or black paint.

Such sludge, in turn, causes numerous mechanical and cosmetic problems including sticky deposits, undercrown deposits, and fuel pump plunger sticking.

Railroad engines and automotive engines are also prone to sludge deposits under typical conditions of operation which can cause decreased oil life or degradation in engine performance.

A main difficulty with salicylate technology is the complexity of salicylate synthesis and the resulting high cost of manufacturing such materials.

However, these salts are not desirable in the final lubricant additive so they must be removed by an aqueous process, and residual water is an undesirable contaminant as it collects acids which can corrode engine parts.

However, the presence of relatively heavy linear alkyl radicals in the alkylphenols makes the latter less reactive than branched alkylphenols, hence the need to use harsher reaction conditions to bring about their neutralization by an alkaline earth metal base.

This makes them much less reactive towards an alkaline earth metal base since the phenol function is much less accessible due to considerable steric hindrance, due to the presence of closer and generally heavier alkyl substituents.

Being alkali-metal free, this detergent-dispersant can be used in applications, such as marine engine oils, where the presence of alkali metals have proven to have harmful effects.

It is unimportant when the treatment with long-chain carboxylic acid, anhydride, or salt thereof occurs relative to the overbasing step.

Lubricating oils for slow and medium speed diesel engines will typically be contaminated with a fuel oil that has a residual oil content.