Patent GB-796505-A (GB)
Title: Improved synthetic lubricant
Inventor: HOARE MICHAEL FREDERICK
IPC: C10M169/00
Filed: 1955-07-11
Abstract: The invention comprises a blend of complex esters in which the dicarboxylic acid component used to prepare the complex ester blend is a mixture of aliphatic dicarboxylic acids and either aromatic dicarboxylic acids or the anhydrides of aromatic dicarboxylic acids. The esters for use as lubricants are of general formul : R1COOR2OOCR3COOR4 R1COOR2OOCR3COOR12OOCR11 R4OOCR3COOR2OOCR13COOR14 where R1 and R11 are the residues of monocarboxylic acids, R2 and R12 are the residues of diols, R3 and R13 are the residues of dicarboxylic acids, and R4 and R14 are the residues of monohydric alcohols.  R1 may be a straight or branched chain saturated hydrocarbon radical of 1 to 22 carbon atoms, or a series of saturated hydrocarbon radicals interlinked by 1 to 5 oxygen atoms, there being at least two carbon atoms between each pair of oxygen atoms and at least one carbon atom between the carboxyl group and the nearest oxygen atom, there being 3 to 22 carbon and oxygen atoms in the radical, or it may be a saturated aliphatic hydrocarbon chain containing a single interlinked sulphur atom which is separated from the carboxyl group by at least one carbon atom, the total number of carbon and sulphur atoms in the radical being 3 to 22.  R2 may be a straight or branched chain saturated aliphatic hydrocarbon group of 2 to 18 carbon atoms, or a series of such hydrocarbon radicals linked by oxygen and/or ether sulphur, provided that there are at least two carbon atoms between each carboxyl group and the nearest oxygen and sulphur groups, or between each oxygen and sulphur atom, and that the total number of atoms in the radical is from 5 to 80, not more than 2 being sulphur.  R3 may be a straight or branch-chained saturated aliphatic hydrocarbon radical containing up to 26 carbon atoms, or a series of hydrocarbon radicals linked by oxygen and/or sulphur, provided that there are at least two carbon atoms between each pair of oxygen or sulphur atoms and that the total number of atoms in the radical is from 30, there not being more than 2 sulphur atoms.  R4 may be a saturated, straight or branched chain aliphatic hydrocarbon radical of 1-20 carbon atoms, or a series of such radicals, interlinked by oxygen and/or sulphur atoms, the total number of atoms in the radical being from 4 to 20, there not being more than 5 oxygen, or oxygen and sulphur, atoms in the radical, and the number of sulphur atoms does not exceed 2.  The molecular weight of the entire ester should be at least 300 and the viscosity at 210 DEG  F. should not be greater than 150 seconds (Saybolt).  The complex esters may be prepared either by the monohydric alcohol half ester method or by refluxing all the components together in the presence of an esterification catalyst and water entrainer. Suitable temperatures of reflux are 150-200 DEG  C., using an esterification catalyst such as sulphuric acid, sodium bisulphate, or an aryl sulphonic acid and a water entrainer such as an aromatic hydrocarbon.  Any residual reactants should be removed, e.g. by vacuum stripping.  Preferred starting materials are aliphatic straight or branched chain primary alcohols, containing no oxygen or sulphur atoms and having from 6 to 10 carbon atoms per molecule, fatty acids containing 2-10 carbon atoms per molecule, straight or branched chain dibasic acids of the paraffinic group having 6-10 carbon atoms per molecule, and ethylene glycol or any of its paraffinic homologues having up to 18 carbon atoms.  Numerous examples of these are given.  Suitable compounds which may be used to introduce an aromatic residue into the molecule are phthalic acids, or anhydrides, phenylenediacetic acids and higher phenylene alkanoic acids.  The proportion of such material should preferably be less than 20 per cent.  An example is given of the preparation of a blend of a complex ester and a diester (viz. di-(2-ethylhexyl) sebacate) using tetraethylene glycol, sebacic acid, and 2-ethylhexanol, and of a similar ester blend when part of the sebacic acid is replaced by phthalic anhydride.  Various addition agents may be incorporated in the esters, e.g. antioxidants, thickeners, viscosity index improvers, pour-depressants and dyes.