Patent GB-687845-A (GB)
Title: Synthetic lubricating oil
Filed: 1949-02-02
Abstract: The invention comprises the di-n-decyl esters of m- and p-phenylenediacetic acids, which are used as lubricants.  Details are given of their physical properties and preparation from the acid and alcohol with an esterification catalyst such as p-toluenesulphonic acid.  The acid may be prepared from xylylene dichloride by conversion into the dicyanide and hydrolysis.  The xylylene dichloride may be obtained by (1) chlorinating xylene; (2) chloromethylating benzene in two stages; or (3) chlorinating toluene and chloromethylating the resulting benzyl chloride.  An example is given of the chloromethylation of benzyl chloride to p-xylylene dichloride, conversion to p-xylylene dicyanide with aqueous alcoholic sodium cyanide, hydrolysis to p-phenylenediacetic acid and esterification with 1-decanol. Specification 583,633 is referred to. The Provisional Specification describes similar esters of the general formula <FORM:0687845/IV (b)/1> where Ar is a benzene or diphenyl nucleus which may contain alkyl side chains with not more than 16 carbon atoms in such chains, and may be partially or fully hydrogenated, n and m are 1-9 and R and R1 are straight or branched chain saturated or unsaturated hydrocarbon radicals or consist of a series of saturated aliphatic hydrocarbon radicals linked through 1-5 oxygen or sulphur atoms (not more than 2 sulphur in each group), each pair of oxygen and/or sulphur atoms being separated from each other and from the carboxyl group by at least 2 carbon atoms, the total number of carbon, oxygen and sulphur atoms in the two ester groups being 8-40.  There are included mixtures of esters in which the carboxyalkyl groups are attached to the nucleus in different positions.  The esters are prepared by the same general methods as above, including Friedel-Crafts condensation with dibasic acid anhydrides or mono-chlorides and reduction of the ketonic groups. Specified additional acids for esterification are m-phenylene-di-propionic and nuclear ethyl derivative, 1-methyl and 1-tert.-octyl-2 : 4 - phenylenediacetic, hexahydro - m - phenylenediacetic and tert.-butyl derivative, 1 : 2 : 3 : 4 - tetrahydro - p - phenylenediacetic and 4 : 41 - diphenylenediacetic and its perhydrogenated derivative. Specified alcohols for esterification are methyl, ethyl, n-propyl, n- and iso-butyl, n- and iso-amyl, n-octyl, 2-ethylhexyl, cetyl, oleyl alcohols; the mono n-butyl, 2-ethylbutyl, 2-ethylhexyl and iso-octyl ethers of ethylene glycol; n-butyl, tert.-octyl and n-dodecyl-mercaptoethanols; mono n-butyl, 2-ethylbutyl and 2-ethylhexyl ethers of diethylene glycol; mono isopropyl and n-butyl ethers of propylene glycol, also the mono butyl, tert.-octyl and n-dodecyl thioethers; mono methyl, ethyl, isopropyl and n-butyl ethers of di- and tri-propylene glycols; n-butyl, tert.-octyl and n-dodecyl-mercaptoethoxyethanols and mercaptopropoxypropanols.  Also suitable are OXO alcohols prepared from C7, C8 and higher olefines.ALSO:Di n-decyl m-phenylenediacetate and di n-decyl p-phenylenediacetate may be blended with mineral lubricating oils to give lubricants.  According to the Provisional Specification there may be used any ester of the formula <FORM:0687845/III/1> where Ar is a benzene, diphenyl or other aromatic nucleus which may be partially or full hydrogenated, n and n1 are 1-9 and R and R1 are aliphatic radicals the chains of which may be interrupted by oxygen and/or sulphur; Ar may have alkyl side chains of not more than 16 carbon atoms in all; certain restrictions are placed on R and R1.  Mixtures of such esters may be used with or without mineral oils.  Suitable alcohols and dibasic acids are listed from which esters may be made.