Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Sulfurized compound of indeterminate structure – which is a...
Reexamination Certificate
1998-07-24
2001-06-12
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Sulfurized compound of indeterminate structure, which is a...
Reexamination Certificate
active
06245724
ABSTRACT:
The present invention is concerned with a process for preparing sulfurised phenol lubricating oil additives, lubricant oil compositions and concentrates containing such additives, with the use of such additives in lubricant oil formulations and with the preparation and use of intermediates for such additives.
Power trains, for example, automotive power trains, require shaft and bearing seals to prevent the ingress of contaminants. Seal life depends on, inter alia, the suitability of the chosen seal for the use to which it is put, the degree of care used in installing the seal, the temperature to which the seal is exposed during use, the nature of the lubricants with which the seal comes into contact during use, and the condition of the surface(s) with which the seal comes into contact during use. Seal failure will in most cases lead to a leakage of lubricant, which is increasingly regarded as unacceptable, and seals which can no longer perform their intended function must normally be replaced. There is thus a need for the life of seals to be prolonged for as long as possible.
There is also a strong desire to develop lubricating oil additives which have reduced levels of chlorine so that their use in finished oil formulations does not contribute to high levels of chlorine in the finished lubricating oil formulation. The presence of chlorine in lubricating oils is a problem from a waste disposal and environmental point of view. When lubricating oils containing high levels of chlorine are destroyed after use e.g. by incineration harmful chlorinated and polychlorinated biphenyls may be produced. Waste disposal of compositions based on chlorine-containing additives is therefore a problem; it would be advantageous to be able to produce chlorine-free additives or additives containing low levels of chlorine.
Sulfur-containing additives have been widely used in various lubricants, e.g., crankcase lubricating oils, or gear lubricants, and in various functional fluids, e.g., hydraulic fluids, automatic transmission fluids and heat transfer fluids. One of the most common of such sulfur-containing additives are the sulfurised phenols such as alkyl substituted phenolsulfides, disulphides, polysulfides, salts thereof, overbased salts thereof, and mixtures thereof. These additives function as oxidation inhibitors, antiwear additives and load carrying additives and detergents for these different category of fluids.
Whilst these sulfur-containing additives have been found to be quite effective for the above mentioned functions, they have generally been found to be corrosive to metals such as copper and copper alloys which are widely used as bearings and bearing liners. They have also been found to cause the degradation of elastomeric materials which are used as seals or sealant devices. This is a particular problem with sulfurised phenol additives. It would be desirable to be able to use higher levels of sulfurised phenols however the problems associated with copper corrosion and/or seals precludes this. It is also desirable to be able to keep the ash content of lubricating oil formulations as low as possible. It is believed that the problems associated with sulfurised phenols are due to the presence of sulfur species, including elemental sulfur, which are sometimes referred to as labile, free or active sulfur.
There have been various attempts in the prior art to provide sulfurised phenols and other sulfur containing additives for lubricating oils which do not have a detrimental effect on the compatibility of elastomeric seals when exposed to such seals in oil formulations and/or which exhibit reduced copper corrosion.
In U.S. Pat. No. 4,228,022, a process is described in which a sulfurised phenate is reacted with sufficient &agr;-olefin (C
15-18
) to ensure that the final product has substantially no residual free sulfur so that the product has anti-corrosive properties; that is, so that it does not corrode metallic engine parts. The level of &agr;-olefin which may be used is up to 25 wt % based on the amount of phenol used to prepare the phenate. More generally it is indicated that the olefins preferably contain 10 to 30 carbon atoms, especially 15 to 20 carbon atoms, and may be straight or branched chain. The performance of elastomeric materials is not discussed.
International Specification No. WO 85/04896 indicates that labile sulfur-free additives for lubricants can be obtained by treating sulfurised phenol additives containing labile or active sulfur with copper, or copper and another material reactive with labile sulfur, or with a mono-olefin, particularly an &agr;-olefin; &agr;-olefins containing 4 to 30 carbon atoms, especially 10 to 20 carbon atoms, being preferred. The olefin is used at up to 10 wt % based on the sulfurised additive and only in an amount sufficient to remove the active sulfur present. It is stated that the metal corrosivity and the degradation of elastomeric materials which are caused by labile sulfur-containing additives can be substantially eliminated. There is no reference to specific elastomeric materials and the olefins mentioned in the Examples are C
12
, C
15-18
or C
16-18
&agr;-olefins.
In U.S. Pat. No. 4,309,293, a process is described wherein sulfurised phenols derived from the reaction of sulfur monochloride and substituted phenols are further reacted with vinyl ethers. The vinyl ether reacts with the phenolic hydroxyl groups present. There is no reference to the performance of elastomeric materials.
Whilst the prior art has gone some way to overcome the problems associated with the use of sulfurised phenols in lubricating oil compositions which exhibit copper corrosion problems, there has been relatively little improvement in the compatibility of such compositions with elastomeric seals and more specifically compatibility with nitrile seals. There is a need therefore for sulfurised phenol additives which show further improvements in seal compatibility, especially nitrile seal compatibility, and for improved processes for making such additives. Furthermore there is also a need for such additives and processes which do not exacerbate the problems associated with the presence of chlorine in lubricating oil formulations and thus enable the use of high levels of sulfurised phenols. This is desirable because the use of higher levels of sulfurised phenols in lubricating oil formulations may allow the levels of metal containing detergents and other metal containing additives which contribute to the ash levels in lubricating oil formulations to be reduced. The problems are particularly severe for lubricants for heavy duty diesel engines which normally require high levels of sulfur-containing additives. A lubricant for a heavy duty diesel engine will typically contain up to 3 mass % of a sulfur-containing compound such as a sulfurised phenol. There is a need therefore for sulfurised phenol additives which can be used at high levels in lubricating oil compositions which are compatible with elastomeric seals and which also do not contribute significantly to the chlorine content of the composition.
The applicants have also surprisingly found an improved process for producing sulfurised phenol intermediates which may be advantageously used for the production of sulfurised additives of the present invention or which may advantageously be used in their own right as additives in lubricating oil compositions especially for formulating lubricating oil compositions with low levels of chlorine.
The present invention therefore provides a process for preparing an oil-soluble sulfurised phenol additive compatible with nitrile seals which process comprises the steps of:
(i) reacting together at a temperature of at least 100° C. an oil-soluble active-sulfur containing sulfurised phenol intermediate; and an olefin or an acetylenic compound in an amount in excess of that required to react with the active sulfur present in the sulfurised phenol intermediate; and
(ii) removing substantially all unreacted olefin or acetylenic compound.
The present invention also provides an oil-solu
Adams David Robert
Simpkin Dennis J.
Skinner Philip
Exxon Chemical Patents Inc.
Howard Jacqueline V.
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