Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic sulfur compound – wherein the sulfur is single bonded...
Reexamination Certificate
2000-01-03
2003-05-27
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic sulfur compound, wherein the sulfur is single bonded...
C508S435000, C508S460000, C508S574000, C508S586000
Reexamination Certificate
active
06569821
ABSTRACT:
This invention relates to colloidal overbased metal detergents stabilised by a mixture of surfactant anions, and having advantageous properties when used in oleaginous compositions, particularly in lubricating compositions, more especially compositions suitable for use in internal combustion piston engine, especially gasoline (spark-ignited) and diesel (compression-ignited), crankcase lubrication, such compositions being referred to as crankcase lubricants.
A crankcase lubricant is an oil used for general lubrication in an engine, such as an automobile or truck engine, where there is an oil sump below the crankshaft of the engine and to which circulated oil returns.
Overbased metal detergents are generally salts or complexes having a large excess of basic metal cation over that required to neutralize the oil-soluble anionic component of the detergent. They may be prepared in colloidal form by heating a mixture of an oil-soluble detergent material, such as a hydrocarbyl sulphonate or hydrocarbyl sulphonic acid, with an alkaline earth or alkali metal compound in stoichiometric excess over that required to neutralize the detergent material, and then forming a dispersion of basic particles by reacting the excess metal compound with an acidic species, preferably carbon dioxide. The resulting overbased metal detergent product consists of a colloidal dispersion of basic particles, such as calcium carbonate, stabilised by a protective layer of the detergent.
Overbased metal detergents are widely used as additive components in lubricants, particularly crankcase lubricants. Such a hostile environment subjects the base oil of the lubricant to high temperatures, high shear stress and chemical attack from fuel combustion products.
Under such conditions, the combustion products are corrosive and degrade the lubricant. Acids resulting from fuel combustion or oil oxidation are particularly damaging to the proper functioning of the engine and must be neutralised. In addition to containing overbased metal detergents to perform this function, lubricants need to contain a variety of other auxiliary additives (or co-additives) performing a variety of functions. Such additives have to be sufficiently compatible to ensure that the lubricants can be prepared without undue processing difficulties, and that the resulting products remain sufficiently compatible during storage, transport and end-use to remain effective. A particular problem is preparation of a concentrate of additives in an oleaginous carrier fluid (a so-called ‘adpack’) for subsequent introduction into a finished lubricant for use in the intended working environment.
Typically, a lubricant suitable for example, for crankcase lubrication, not only requires adequate protection against combustion and degradation products, but also includes friction modifiers to improve fuel economy. Aliphatic amides and their derivatives constitute a class of compounds that is frequently included in lubricants to provide friction modification.
The preparation of a concentrate containing both overbased metal detergents and an aliphatic amide gives rise to a number of problems. Firstly, the amides are solid at room temperature: thus, it is difficult to disperse an effective amount of the amide in the detergent-containing oil. Secondly, and of much more significance, the addition of the amide to detergent-containing oils can readily result in destabilisation of the concentrate, particularly at increased amide concentrations. The aliphatic amides have strong surface activity, so that, on addition to carrier oils containing overbased detergents, the aliphatic amide molecules will compete with the molecules of detergent for occupancy of the surface of the dispersed inorganic particles. It has been observed that, on storage of this composition, the competition and interchange between surface active molecules can result in destabilisation, manifested by haze or sediment appearing in the oil. This antagonistic effect of the amide severely limits the amount of amide that can be added to overbased detergent-containing oils, and as a consequence, limits the friction-modifying benefits that would be obtained at higher amide concentrations. Typically, concentrates containing from 1.5 to 3.0 mass % of overbased detergent start to destabilise when more than about 0.15 mass % of amide is added.
EP-A-0 645 444 discloses lubricants containing linear alkaryl overbased detergents, optionally containing friction modifiers such as fatty acid esters and amides and glycerol esters of dimerised fatty acids. Although such combinations are not exemplified there is no indication in the description that the mixtures are anything other than simple mixtures of the preformed components.
EP-A-0 609 623 discloses engine oil compositions comprising a neutral or overbased metal detergent, an ashless dispersant and an antiwear agent comprising a mixture of an aliphatic amide and either a dithiocarbamate compound or an ester derived from a fatty acid and boric acid. The compositions are described in the Examples as simple admixtures of these components and, as such, will be subject to the problems described above.
Overbased metal detergents have now been devised in which a friction-modifying amide component is incorporated as an integral step in the preparation of the overbased detergent. This procedure for introducing a friction-modifying function into the lubricant composition avoids or significantly reduces the extent of the problems referred to above and provides a number of additional unexpected advantages.
In a first aspect, the invention provides an overbased metal detergent having friction-modifying properties comprising a stable, colloidal dispersion of inorganic base particles in an oil of lubricating viscosity, wherein the detergent comprises
i) from 15 to 40 mass % of collodial particles;
ii) from 20 to 45 mass % of a stabilising system comprising the mixture obtained by combining
A) at least one oil-soluble detergent component having an anionic moiety selected from sulfonate, phenate, sulfurised phenate, thiophosphonate, salicylate, carboxylate, or naphthenate, and
B) at least one aliphatic amide having from 10 to 30, preferably 16 to 24, carbon atoms, constituting from 25 to 75, preferably 30 to 60, more preferably 35 to 55, mass % of the mixture; and
iii) the oil of lubricating viscosity as the balance.
By “stably dispersed” is meant that, after the detergent has been subject to storage at ambient temperature for extended periods, for example for 4, preferably 8, weeks, it is free from haze and contains no more than 0.05% by volume of sediment.
It will be appreciated that, although the detergent of the invention is formed by admixing the two surface active components A) and B), as defined above, it is likely that at least part of each component charge will be chemically changed as a result of subsequent reaction within the system, so that the term “the mixture obtained by combining” includes the products resulting from the subsequent reaction of the components.
In a second aspect, the invention provides a method of making an overbased metal detergent comprising stably dispersing colloidal inorganic base particles in an oil of lubricating viscosity, using a mixture of at least one oil-soluble sulphonate, phenate, sulfurised phenate, thiophosphonate, salicylate, carboxylate, or naphthenate, with at least one oil-soluble aliphatic amide having from 10 to 30, preferably from 16 to 24, carbon atoms.
The detergent of the invention not only provides a lubricant with the ability to neutralize acidic materials formed in the operation of an automotive engine, but also provides a significant measure of friction modification thereto. Surprisingly, although the amide provides a contribution to the stabilisation of the colloidal particles, and is consequently intimately associated with the stabilising layer around the colloidal particles, the amide evidently also becomes available as a friction modifier at the metal-to-metal contact areas of the operating engine. In fact, detergents of the in
Adams Christopher John
Cleverley John A
Galsworthy Jane Rachel
Ibrahim Tuncel
Skinner Phillip
Infineum USA L.P.
Johnson Jerry D.
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