Patent GB-917431-A (GB)
Title: Aromatic fluoroesters and their preparation and use
IPC: C10M105/54
Filed: 1960-02-29
Abstract: Fluoroesters of benzene tri- and tetra-carboxylic acids comprising 1, 2 or 3 groups having the structure <FORM:0917431/III/1> wherein R represents one or more CH2 radicals, X is a hydrogen or a fluorine atom, and n is an integer from 1 to 24, the esters also comprising at least one alkoxycarbonyl group, are suitable for use in the production of hightemperature lubricating oils and greases, either as sole lubricant or in admixture with conventional lubricants. Stabilizers against oxidation and corrosion may be added to the ester, such as phenyl alpha-naphthylamine, diphenylamine, phenylthio-alpha(methylnaphthyl) amine, thio(diethylphenyl) amine, N-n-valeryl4 - amino - 3 - pentadecylphenol, N - palmitoylp-aminophenol, didecyl selenide, di-lauryl diselenide, dicetyl telluride, dilauryl selenoxide, calcium petroleum sulphonates, indium 2-ethylhexanoate, indium p-octyl benzoate, and indium caprylate.  In the case of high-temperature greases the following are recommended as gelling agents:- silica aerogels, finely-divided silica prepared by burning silanes, clays, trimethyl stearyl ammonium bentonites, indanthrene dyes and indogens, clays coated with phenol-formaldehyde or aniline-formaldehyde resins, and graphite.  For the production of the fluoroesters-see Group IV(b).ALSO:Fluoroesters of benzene tri- and tetracarboxylic acids comprising 1, 2 or 3 groups having the structure <FORM:0917431/IV (b)/1> wherein R represents one or more CH2 radicals, X is a hydrogen or fluorine atom, and n is an integer from 1 to 24, the esters also comprising at least one alkoxycarbonyl group, are produced by reacting an alkyl ester of a benzene tri- or tetra-carboxylic acid with an alcohol of the structure X(CF2)nROH in the presence of an ester-interchange catalyst, the proportions of the two reactants being such that at least one of the alkyl ester groups remains unreacted.  A typical sub-group of these fluoroesters, which are useful as hightemperature lubricants (see Group III), has the structure <FORM:0917431/IV (b)/2> In Example 1, trimellitic acid is refluxed with methanol in the presence of a catalytic amount of sulphuric acid.  Trimethyl mellitate is isolated from the product, and is purified with active clay.  This trimethyl ester is mixed with 1,1,7-trihydroperfluoroheptanol and a catalytic amount of sulphuric acid, and the mixture is refluxed using a fractionating column.  The methanol, produced in the reaction is then distilled off, and the remaining mixture is taken up in ether and washed with aqueous potassium hydroxide.  The ether and excess fluoroheptanol are then stripped off under reduced pressure; and a colourless oil viz. dimethyl-1,1,7-trihydroperfluoroheptyl tri-mellitate is obtained as finished product.  The example also refers to the preparation of monomethyl-di(1,1,7-trihydroperfluoroheptyl)trimellitate.  Example 3 describes the production of a mixture more than 50% of which comprises dimethyl(1,1,9-trihydroperfluorononyl) (1,1,11 - trihydroperfluoroundecyl)pyromellitate, the remainder of the mixture comprising equimolar amounts of dimethyl di(1,1,9-trihydroperfluorononyl) and dimethyl (di 1,1,11 - trihydroperfluoroundecyl)-pyromellitates.