Patent GB-963338-A (GB)
Title: Cadmium dialkyl dithiophosphate additives for lubricating oil compositions
IPC: C10M137/10
Filed: 1960-10-04
Abstract: The invention comprises a cadmium dialkyldithiophosphate prepared by reacting a secondary alkanol having 3 to 20 carbon atoms per molecule with phosphorus pentasulphide having a phosphorus content of from 26.0 to 27.8 weight per cent to form the corresponding dialkyl dithiophosphoric acid and converting this acid into the corresponding cadmium dialkyl dithiophosphate either by (a) neutralising it directly with a basic cadmium compound e.g. cadmium oxide or (b) by converting the acid into an alkali metal dialkyl dithiophosphate and reacting this by double decomposition with an inorganic cadmium salt. The secondary alkanol is preferably one containing 4 to 6 carbon atoms per molecule e.g. a mixture of secondary butanol and methyl isobutyl carbinol, and it is preferred to blow the intermediate dialkyl dithiophosphoric acid free of H2S with an inert gas, e.g. nitrogen, before reacting with the cadmium compound. When the neutralisation is carried out with cadmium oxide it is suitably effected at between 80 and 200 DEG F. Elemental sulphur may be added to the dialkyl dithiophosphoric acid immediately before the neutralisation step.  The dialkyl dithiophosphoric acid is suitably prepared by reacting 4 moles of the alkanol with 1 mole of phosphorus pentasulphide at 160 to 200 DEG F. for about 1 to 6 hours and the product is generally filtered before the neutralisation step. Examples are given in which cadmium oxide is used in the neutralisation step, the phosphorus pentasulphide used has a phosphorus content of 27.5% and the secondary alkanols are methyl isobutyl carbinol and a mixture of secondary butanol and methyl isobutyl carbinol. A comparative example is also given in which a mixture of primary isobutyl and primary amyl alcohol is reacted with the P2S5 of 27.5% P content and the product neutralised with CdO to form the cadmium dialkyl dithiophosphate. The products are useful as additives for lubricants (see Division C5). Specification 932,961 is referred to.ALSO:A lubricating oil contains as additive a cadmium dialkyl dithiophosphate prepared in a specific manner (see Division C2). The lubricating oil is preferably a mineral oil, but may also be an animal, vegetable or synthetic oil. Examples of synthetic oils are diesters, complex esters, silicone oils and phosphorus derivatives, e.g. a C8 oxo diphenyl phosphate.  Other additives may be present, e.g. corrosion or rust inhibitors, oxidation inhibitors, extreme pressure agents, pour point depressants, viscosity index improvers, detergent additives and antifoamants (e.g. a silicone fluid). Specified corrosion or rust inhibitors are mercaptoacetic acids of the formula R.S.CH2.COOH, wherein R is a branched C9-C17 alkyl group, monoalkenyl substituted succinic acids in which the alkenyl substituent contains 10 to 22 carbon atoms, and dinonyl naphthalene sulphonates. Specified oxidation inhibitors are the conventional phenolic and amine inhibitors and suitable extreme pressure additives are halogen-containing organic compounds, e.g. chlorinated wax and chlorinated camphene.  Specification 932,961 is referred to.