Patent GB-776669-A (GB)
Title: Improvements of low temperature stability of synthetic lubricants
Inventor: FOWLER BENJAMIN THOMAS
Filed: 1954-06-04
Abstract: A composition adapted to lubricate aviation gas turbine engines comprises a complex ester as defined below and a minor proportion of a compound (other than N-acyl-p-amino-phenol) having the formula Ar(R1)R2 wherein R1 and R2 are each chosen from hydroxy, mercaptan, amine and esterified carboxyl groups and Ar is an aromatic nucleus, or alternatively R1 and R2 are replaced by a heterocyclic ring fused to the aromatic nucleus and comprising two of the carbon atoms of the aromatic nucleus together with a plurality of hetero atoms chosen from oxygen, nitrogen and sulphur.  The compounds Ar(R1)R2 may carry additional substituents such as alkyl, amine or amide groups.  The complex ester has one of the following formul : - R2OOCR1COOR4OOCR3 ; R3COOR4OOCR13; R2(OOCR1COOR4)n; OOCR11COOR12; or R3COOR4(OOCR1 COOR14)nOOCR13.  In these complex ester formul  R1 and R11 are the residues of dicarboxylic acids HOOCR1COOH; R2 and R12 are the residues of monohydric alcohols R2OH; R3 and R13 are the residues of monocarboxylic acids R3COOH; R4 and R14 are the residues of glycols or polyglycols; and n is a number from 1 to 6.  Examples of compounds Ar(R1) R2 are phenothiazine, benzoxazole, 1, 4, 2-benzoxazine, thianthrene, quinoxaline, and the corresponding naphthalene derivatives, ethyl or butyl salicylate, mono- or di-butyl phthal ate, salicylanilide, N,N1-di-tert.-butyl-p-phenylene diamine and 2, 3-dihydroxynaphthalene.  The composition may also contain diesters which may have the formula R2OOCR1COOR12 or R3COOR4-OOCR13 wherein R1, R2, R3 and R4 have significance mentioned in connection with complex esters, R4 being an alkylene group.  Preferred diesters are dioctyl and dinonyl sebacate.  Compositions consisting of complex esters, diesters and phenothiazine, wherein phenothiazine is the only compound in the composition having the general formula Ar(R1)R2 as above defined are disclaimed.  In the examples, compositions are described consisting of a complex ester (derived from sebacic acid, 2-ethyl hexanol and a polyglycol of molecular weight about 200), dioctyl sebacate, dinonyl sebacate, "Acryloid 710," phenothiazine and one of:-ethyl or butyl salicylate, butyl phthalate, salicylanilide N,N1-di-tert.-butyl-p-phenylene diamine, 2, 3-dihydroxy naphthalene and pyrogallol.  For comparison purposes, similar compositions are described in which glycerol monostearate or hexachlorobenzene replaces the compound of formula Ar(R1)R2.  According to the Provisional Specifications, the composition may comprise a diester and/or a complex ester together with a minor proportion of the compound Ar (R1)R2, and the complex ester may contain sulphur in thioether linkages, while additional examples of compound Ar(R1)R2 are catechol, hydroquinone, o - aminothiophenol, o - aminophenol, and mercaptobenzthiazole.  In the first Provisional Specification, compositions are described consisting of a complex ester (derived from sebacic acid, 2-ethyl hexanol and polyglycol 200), dioctyl sebacate, dinonyl sebacate, "Acryloid 710" (a polymethacrylate ester) and one of catechol, o-aminophenol and mercaptobenzthiazole.  In the second Provisional Specification, compositions are described consisting of the same complex ester, dioctyl sebacate, dinonyl sebacate, "Acryloid 710," phenothiazine and one of catechol, hydroquinone and resorcinol.  Specifications 711,211 and 716,732 are referred to.  Reference has been directed by the Comptroller to Specification 743,571.