GB767151A - Manufacture of synthetic ester lubricants - Google Patents

Abstract

A lubricating coomposition comprising a complex ester lubricant, or a saturated aliphatic diester lubricant or saturated aliphatic simple ester lubricant and a minor proportion of phenothiazine is obtained by esterifying the appropriate carboxylic acids and alcohols and adding a minor proportion by weight of phenothiazine to the ester-forming reactants before completion of the esterification reaction. The complex esters may be prepared from monohydric alcohols, polyhydric alcohols, monobasic acids, and dibasic acids and are defined as polyesters in which hypothetical replacement of the ether oxygen atoms of the ester groups and any other ether oxygen atoms and/or sulphide sulphur atoms that may be present by methylene groups would result in a polyketone having three or more carbonyl groups in the same carbon chain. The diesters may be those derived from a monobasic acid and a dihydric alcohol, e.g. a glycol or polyglycol, or those derived from a monohydric alcohol and a dibasic acid. The types of complex ester specified are (1) monobasic acid-glycol-(dibasic acid-glycol)x-monobasic acid; (2) alcohol-dibasic acid-(glycol-dibasic acid)x-alcohol; and (3) alcohol-(dibasic acid-glycol)x-monobasic acid; x in each case being 1 to 5. Esters of type (1) and (2) may be prepared by esterification of calculated amounts of the acid and alcohol reactants; type (3) may be prepared by reacting a dibasic acid and a glycol under such conditions that one hydroxyl group of the glycol reacts with one carboxyl group of the dibasic acid to form a half ester which is then reacted with a molar proportion of an aliphatic alcohol and monocarboxylic acid and type (2) in the case when x=1 may be obtained by reacting an alcohol with a dibasic acid to form a half ester and then reacting two moles. of the latter with one mole. of a glycol, e.g. as in Specification 680,438. The complex esters of type (1) in which x is 1 may also be obtained by reacting a monobasic acid with a glycol to form the half ester and then reacting two moles. of the latter with one mole. of a dibasic acid. Specified monohydric alcohols are n-hexyl, n-octyl, 2-ethylhexyl, cetyl, oleyl, 2-ethylbutyl, 2-butyloctyl, capryl, amyl and lauryl alcohols, and ether alcohols formed by reacting ethylene oxide or propylene oxide with aliphatic alcohols. Specified monobasic acids are propionic, butyric, valeric, caproic, capric, caprylic, lauric, palmitic, 2-ethylbutyric, 2-ethylhexoic and stearic acids, also oxo acids, e.g. C8, C10, C16 acids, acids produced by oxida tion of petroleum fractions and those produced by alkali fusion of alcohols. Specified dibasic acids are succinic, glutaric, adipic, pimelic, suberic, azelaic, and sebacic acids. The polyhydric alcohols include ethylene glycol and its homologues, polyethylene glycols and glycols containing interrupting oxygen or sulphur atoms, e.g. thiodiglycol, 1,2-bis-(2-hydroxy-ethylmercapto ethane and bis-2-(2-hydroxy-ethoxy) ethyl sulphide. Specified simple ester lubricants are isobutyl butyrate, n-octyl acetate, amyl caproate, n-propyl iso-octanoate, butyl laurate and ethyl nonanoate. The esterification is preferably carried out in the presence of an esterification catalyst, e.g. toluene sulphonic acid, sulphosalicylic acid, sodium acid sulphate, boric acid, phosphoric acid and zinc sulphate. In the one step, esterification procedure all of the ingredients including phenothiazine, excess alcohol (or monobasic acid), water entrainer, solvent and catalyst are heated to about 180-220 DEG C. until all the water of esterification has been removed or until a product of low acid number is obtained. The heating is then continued at about 230 DEG to 260 DEG C. to remove the solvent, water entrainer and excess reactant, usually under reduced pressure. When the esterification is carried out by a two-step procedure, the phenothiazine may be added at the start or after the first esterification stage. From 0.001 to 10 per cent and preferably from 0.05 to 2.0 per cent by weight of phenothiazine may be used. Examples are given for the production of complex esters by a one step and two step (via glycol+acid and via alcohol+acid) esterification of sebacic acid, polyethylene glycol 200, and 2-ethylhexanol in the presence and absence of phenothiazine and of sodium bisulphate as esterification catalyst and tables are given to show that the complex esters formed by esterification in the presence of phenothiazine are obtained in increased yield and have improved properties as lubricants. In other examples: (1) a mixture of butanediol-1,4, C8 oxo alcohol, adipic acid and xylene is heated for 16 hours after which an additional amount of the C8 oxo alcohol and of butanediol-1,4 is added and the mixture again heated to remove water of esterification; (2) a dibasic acid ester obtained by esterification of 2-ethylhexanol, and sebacic acid in the presence of phenothiazine and heptane is modified by carrying out the esterification in the presence of a small amount of polyethylene glycol 200; (3) and (4) as in (2) except that sodium bisulphate and lime respectively are also included in the esterification mixture as esterification catalysts. The diesters may be modified by preparing them in the presence of 0.1 to 15 per cent of a glycol or of a dibasic acid. The ester products of the invention may be mixed with other lubricants and other conventional lubricating oil additives (see Group III).ALSO:A lubricating composition comprises a complex ester lubricant, a saturated aliphatic diester lubricant or a saturated aliphatic simple ester lubricant, or lubricating mixtures thereof and a minor proportion of phenothiazine, said composition being obtained by esterifying the appropriate carboxylic acids and alcohols and adding phenothiazine to the ester forming reactants before completion of the esterification reaction (see Group IV(b)). The diesters may be those derived from a monobasic acid and a dihydric alcohol or from a monohydric alcohol and a dibasic acid. Specified simple ester lubricants are isobutyl butyrate, n-octyl acetate, n-propyl isooctanoate, butyl laurate and ethyl non-anoate. The complex esters are of the conventional synthetic lubricant type and may be prepared from dibasic acids, polyhydric alcohols, and monohydric alcohols and/or monobasic acids and they may be obtained either by the one step or two step esterification procedures. The amount of phenothiazone may be from 0.001 to 10 per cent and preferably from 0.05 to 2.0 per cent based on the weight of the product. Other additives such as silicones, phosphites, phosphates, amines, sulphonates, rust inhibitors, viscosity index improvers, pour point depressants, load carrying agents and oxidation inhibitors may be added to the products. The products may also be blended with other lubricating oils which may be mineral oils or synthetic lubricants. The esters, or blends containing them, may be used to formulate grease compositions by thickening with the common grease forming soaps. Examples are given for the production of complex esters from sebacic acid, polyethylene glycol 200, and 2-ethylhexanol and from butanediol-1, 4, C8 oxo alcohol and adipic acid the esterification being carried out in the presence of phenothiazine. Examples are also given for the production of a modified diester by esterifying 2-ethyl hexanol and sebacic acid in the presence of phenothiazine and a small amount of polyethylene glycol 200. It is stated that the diesters may be modified by preparing them in the presence of a from 0.1 to 15 per cent of a glycol or of a dibasic acid. Specification 680,438 is referred to.