Patent GB-627569-A (GB)
Title: Improved lubricating oil compositions
IPC: C10M143/12
Filed: 1946-06-12
Abstract: Lubricating oil compositions of improved viscosity index (and sometimes also of improved pour point) comprise a mineral lubricating oil containing from 0.05-10 per cent by weight and preferably about 0.15-1.5 per cent by weight based on the oil of an oil soluble addition compound of a rubbery polymer of a conjugated diolefin (or copolymer thereof with another copolymerizable compound) with a primary aliphatic mercaptan containing from 8-18, and preferably from 12-18 carbon atoms per molecule (see Group IV (a)).  The term " primary mercaptan " refers to mercaptans in which the SH group is attached to a terminal carbon atom of the aliphatic radical.  The mercaptan may be primary n-tetradecyl mercaptan, n-hexadecyl mercaptan, or a mixture of primary mercaptans containing predominantly mercaptans having 12 carbon atoms in the molecule.  The additive may be a mixture of a compound obtained by condensing the olefine copolymer or polymer with n-tetradecyl mercaptan and a compound obtained by condensing the polymer or co-polymer with n-hexadecyl mercaptan. The proportion of mercaptan condensed with the polymer or copolymer may be such that 50-100 per cent of the double bonds in the polymer or copolymer are reacted with mercaptan.  The conjugated diolefine hydrocarbons may contain from about 4 to 6 carbon atoms in the molecule and may be butadiene, isoprene, piperylene, methyl pentadiene, or dimethylbutadiene.  The copolymerizable compounds may be alpha methyl styrene, para methyl styrene, alpha methyl para methyl styrene, vinyl naphthalene, vinyl pyridine, methyl acrylate, methyl methacrylate, or ethyl fumarate. If the polymer or copolymer is highly unsaturated, the addition compound may be substantially saturated, e.g. by hydrogenation.  In an example 0.4 per cent by weight of an addition compound prepared from high molecular weight polybutadiene and a mercaptan mixture containing predominantly n-dodecyl mercaptan (see Group IV (a)) is dissolved in a solvent extracted mid-continent neutral SAE-10 viscosity grade oil.  The V.1. of the latter is thereby raised from 114 to 130 and its pour point lowered from +5 DEG  F. to - 15 DEG  F. Other examples are furnished, showing that the extent to which the pour point is lowered is dependent both upon the nature of the mineral oil and of the additive, certain mixtures of different types of the additive being in some cases more effective than individual additives in this respect.ALSO:Oil-soluble addition compounds of a rubbery polymer of a conjugated diolefine (or a copolymer thereof with another copolymerizable compound) with a primary aliphatic mercaptan containing 8-18 carbon atoms in the molecule, suitable for use as additives in lubricating oils, (see Group III), are prepared by reacting the mercaptans with the solid polymer, e.g. in a rubber mill, or with a solution of the polymer (or copolymer) in a solvent such as benzene, or with a latex of the polymer, in the presence of catalysts of the per compound type.  The proportion of mercaptan condensing with the polymer or copolymer may be varied from zero to substantially 100 per cent, the product in the latter case being substantially completely saturated.  In an example, 200 grams of fresh high mol. wt. polybutadiene in the form of a latex containing about 25 per cent of solid polymer, is diluted to about 500 mls. with 2 1/2 per cent Na soap solution containing 0.2 gram K2S2O8, and reacted at 50 DEG  C. for several days with 200-250 grams of a mercaptan mixture made from alcohols derived from coconut oil, and consisting chiefly of n-C12 mercaptan.  The latex is coagulated and the product kneaded with isopropyl alcohol to remove unreacted mercaptan.  In a further example, a dry solid copolymer of butadiene and styrene is reacted with n-tetradecyl mercaptan in the presence of sulphur as catalyst by heating with agitation for 66 hours at 180-190 DEG  C. in a vessel sealed from the atmosphere.  The copolymer-mercaptan addition compound is isolated by dissolving the reaction mixture in light petroleum ether and precipitating the impure addition compound by means of an excess of 99 per cent isopropyl alcohol. The compound is freed from mercaptan by repeated solution in petroleum ether and precipitation by isopropyl alcohol. Further examples are given of the preparation of addition products from copolymers of butadiene and styrene with n-hexadecyl mercaptan, and with mercaptans derived from coconut oil alcohols, also of addition products from polybutadiene latex and n-octyl mercaptan, and from butadiene-alpha methyl, para methyl styrene copolymer and n-hexacecyl mercaptan by similar methods.