GB669947A - Improvements in or relating to lubricating grease compositions - Google Patents

Abstract

Salts of heterocyclic carboxylic acids are prepared by the Cannizzaro reaction from the corresponding aldehydes and strong alkali. The so-formed salts may be incorporated in lubricating grease compositions (see Group III). If desired, the reaction may be carried out in the presence of a hydrocarbon oil diluent, which oil may be the same as that to serve as the liquid phase of the grease. Furfural is preferred, but aldehydes from thiophene and alkyl substituted homologues of furfural may also be used. In an example (IX) furfural is reacted in a grease kettle with caustic soda in about its own amount of mineral oil as the first stage of a grease manufacture. The Specification as open to inspection under Sect. 91, refers also to the use of benzaldehyde and other aromatic aldehydes, glyoxal and formaldehyde as suitable for simultaneous oxidation and reduction as in the Cannizzaro reaction. Chloro- and nitro-ring-substituted aromatic aldehydes may also be used, as well as thioaldehydes. This subject-matter does not appear in the Specification as accepted.ALSO:Lubricating oil is thickened to a grease with a metal soap of a fatty acid having from 12 to 22 carbon atoms in the molecule and from 2 to 20 per cent by weight, based on the total composition, of a metal salt of a heterocyclic carboxylic acid. The lubricating oil may be a mineral base lubricating oil of viscosity from 35 to 1,000 S.S.U. at 210 DEG F. (preferably 35-200 S.S.U. at 210 DEG F.). Vegetable oils, e.g. castor oil, and synthetic oils may also be used, for instance ester oils, such as di-2-ethylhexyl sebacate and glycollates, or the esters from oxo-alcohols and dibasic acids, or fluorinated hydrocarbons, polyglycols, and silicone oils. Suitable heterocyclic acids are furoic acid and its alkyl-substituted homologues and the thiophene carboxylic acids. The metal salt and metal soap may be compounds of the same metal. Sodium, lithium and calcium salts and soaps are preferred, but potassium, strontium, magnesium and barium compounds may be employed. If desired, the metal salt of the heterocyclic acid may be prepared from the corresponding aldehyde by the Cannizzaro reaction, e.g. sodium furoate from furfural. This reaction may be controlled by a diluent such as a hydrocarbon oil, which may be the same as that to serve as the liquid phase of the grease. Any undesirable reaction products such as water may be removed by evaporation, but the alcohol produced in the reaction may be allowed to remain in the grease, where it may be esterified with the fatty acids subsequently added, or left unchanged. The alcohol may also be polymerised. At the same time, or preferably subsequently, the soap may be formed by adding the C12-C20 acids to the Cannizzaro reaction mixture and p neutralising with a base. Instead of adding furfural to a hydrocarbon oil as such, the reaction may be carried out on the raffinate from the furfural extraction of mineral lubricating oil base stocks (which raffinate contains a minor proportion of furfural) the amount of furfural being adjusted if necessary to between 2 and 20 per cent. The raffinate from refining of drying oils (which contains non-drying oils) or the furfural-containing effluent from a solvent refining of fatty oils or fatty acids may also be employed. The relative proportions of the soap and salt may be between 1 and 4 mols of soap to between 1 and 4 mols of salt. It is preferred that these proportions should be more nearly equal, 1 to 2 mols of soap being used with 1 to 1.5 mols of salt. In general the amount of soap is from 3 to 30 per cent by weight. The soap may be made from hydrogenated fish oil acids, but unsaturated or hydroxy acids of similar molecular weight may be used. Detergent materials (e.g. sodium toluene-C12-alkylate sulphonates), oxidation inhibitors (phenyl-alpha-naphthylamine), corrosion inhibitors, extreme pressure agents, and/or tackiness agents may also be added. If the Cannizzaro reaction is not used, alcohols such as oleyl and cetyl alcohols may be added to react with an excess of the C12-C20 acids forming the soap to give ester plasticizers, the amount of ester being from 0.01 to 5 per cent of the total composition. In an example a grease is prepared using 15 per cent (by weight of the total composition) of hydrogenated fish oil acids, 6 per cent of furoic acid, 5 per cent of sodium hydroxide and 74 per cent low cold test lubricating oil of 50 S.S.U. viscosity at 210 DEG F. The acids together with about one-third of the mineral oil are charged into a grease kettle and heated. The caustic soda is added as a 30 per cent aqueous solution and the temperature raised to dry out the mixed soap and salt. The remainder of the oil is added slowly with stirring, the final temperature being 480 DEG F. A further example (IX) describes the application of the Cannizzaro reaction using 10 per cent (by weight of the total composition) of furfural, 5.4 per cent sodium hydroxide, 15.0 per cent hydrogenated fish oil acids and 68.6 per cent naphtheric lubricating oil of 55 S.S.U. viscosity at 210 DEG F. The furfural, about an equal amount of the oil and about 60 per cent of the alkali as a 33.3 per cent aqueous solution are reacted in a grease kettle. After about 2 hours the fatty acids and about one-third of the mineral oil are added, the kettle heated to 150-160 DEG F. and the remainder of the caustic soda added while the temperature is raised to 350 DEG F. The remainder of the oil is then added slowly and the temperature raised to 450 DEG F. to evaporate water and other volatile constituents. The heating is discontinued, phenyl-alpha-naphthylamine added and the grease cooled while being stirred. The Specification as open to inspection under Sect. 91, refers also to the use of benzaldehyde and other aromatic aldehydes, glyoxal and formaldehyde as suitable aldehydes for simultaneous oxidation and reduction as in the Cannizzaro reaction. Chloro- and nitro-ring-substituted aromatic aldehydes may also be used, as well as thioaldehydes. This subject-matter does not appear in the Specification as accepted.