Patent GB-761211-A (GB)
Title: Improvements in or relating to synthetic lubricants
Filed: 1954-11-24
Abstract: The invention comprises the reaction product of from one to two molar proportions of carboxymethyl mercaptosuccinic acid with from one to four molar proportions of a monohydric alcohol and/or a monobasic acid, each containing from 3 to 16 carbon atoms, preferably from 6 to 10 carbon atoms, and from one to three molar proportions of a glycol, preferably a polyethylene glycol.  A preferred complex ester has the general formula <FORM:0761211/IV(b)/1> wherein R, R1, R2 and R3 are the radicals of aliphatic alcohols containing 3 to 16, preferably 6 to 10, carbon atoms each, such as the oxo alcohols, and wherein n is a number from 2 to 10, preferably 2 to 8, and x is a number from 1 to 10, preferably 1 to 6.  Such a compound is obtained when four mols. of the alcohol are reacted with two mols. of the mercapto acid and the partial ester is further reacted with one mol. of a glycol. Various complex ester structures may be obtained depending on the molar ratios of the various components, e.g. (1) (alcohol)2-mercaptoacid - glycol - monobasic acid; (2) monobasic acid - glycol - <FORM:0761211/IV(b)/2> acid - glycol - monobasic acid; (3) (alcohol2 - mercapto - acid - glycol - mercaptoacid - (alcohol)2; (4) (monobasic acid - glycol)3 - mercapto acid.  The alcohols terminating the complex esters may be the same or different, straight chain or branched and may also be ether alcohols.  Oxo alcohols are preferred. The monobasic acids may also be of straight or branched chain type and include butyric, hexanoic, octanoic, decanoic, dodecanoic and tetradecanoic acids, as well as acids desired from the oxo process by caustic fusion of oxo alcohols or by reacting olefins with carbon monoxide and water.  The complex esters may be prepared by known methods, for example, by first forming the partial ester of the mercapto acid and the alcohol and then reacting the product with the glycol, or by partially esterifying the glycol with the monobasic acid and then reacting with the mercaptoacid.  The reaction temperature may vary from reflux temperature to 400 DEG  C., preferably from 100 DEG  to 230 DEG  C., and the reaction time may be from 2 to 10 hours.  Catalysts such as sodium acid sulphate, toluene sulphonic acid or sulphuric acid, and water entrainers, in an amount of 15 to 40 per cent based on the weight of the glycol, such as heptane, hexane, toluene or xylene, may be used.  In an example, carboxymethyl-mercaptosuccinic acid is partially esterified with a C7 oxo alcohol in the presence of NaHSO4 and heptane and then polyethylene glycol 200 is added and the esterification completed. The complex esters of the invention may be used directly as lubricants or may be blended with other mineral or synthetic lubricants and various additives.ALSO:Lubricating compositions comprise a complex ester which is the reaction product of one to two moles of carboxymethyl mercaptosuccinic acid with from one to four moles of monohydric alcohol and/or a monobasic acid, each containing 3 to 16, preferably 6 to 10, carbon atoms and from one to three moles of a glycol, preferably a polyethylene glycol (see Group IV(b)), blended with mineral oils or synthetic lubricants such as C6 to C16 diesters of adipic, suberic, azelaic or other dibasic acids, simple or complex formals, and other complex esters.  A suitable blend comprises 2.0 to 50 per cent by weight of complex ester.  In addition, viscosity index improvers such as C8-18 acrylate and methacrylate esters and polymers, pour point depressors such as copolymers of fumarate and/or maleate esters with C2-10 vinyl esters, oxidation inhibitors, detergents and corrosion resisting agents, may be added.  An example is given of 10 wt. per cent of a complex ester obtained from carboxymethyl mercaptosuccinic acid, a C7 oxo alcohol and polyethylene glycol 200, blended with dioctyl sebacate.