GB847629A - Improvements relating to synthetic lubricants - Google Patents

Abstract

A lubricating composition comprises a blend of a liquid aliphatic diester of a saturated aliphatic dicarboxylic acid, and a polyester, soluble in the diester, and having the general formula : <FORM:0847629/IV(a)/1> where n is an integer, the Rs are alkyl groups having 4-18 carbon atoms, the R1S are either alkylene groups having 4-14 carbon atoms or phenylene groups, and the R7S are either methyl or ethyl groups, the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 DEG F is 4-30 centistokes. The diesters may have the formula R4OOCR5COOR4 where R5 is an alkylene group having 4-14 carbon atoms and the R4S are alkyl groups, preferably branched-chain, having 4-18 carbon atoms. The polyesters may be prepared by reacting, in one or more stages, one or more dicarboxylic acids HOOCR1COOH or the anhydrides of such acids (where they exist), one or more monohydric alcohols ROH and one or more diols HOCH2C(CH3)(R7)CH2OH. The lubricating composition may also contain an antioxidant, such as phenothiazine, or a crystallization suppressant, such as a polymerized alkyl ester of acrylic or methacrylic acid. In the examples, lubricating compositions are described consisting of a diester (a blend of octyl nonyl sebacate, dioctyl sebacate and dinonyl sebacate prepared from sebacic acid, 2-ethylhexanol and 3,5,5-trimethylhexanol), a polyester and phenothiazine. In the preparation of the polyester, HOOCR1COOH is one or more of sebacic acid, phthalic anhydride, 1,1,3- or 1,3,3-trimethyladipic acid or commercial isosebacic acid (a blend of 1-ethylsuberic acid, 1,4-diethyladipic acid and sebacic acid), ROH is 2-ethylhexanol and the diol is 2,2-dimethyl- 1,3-propanediol or 2-methyl-2-ethyl-1,3-propanediol. Specification 824,249 is referred to.ALSO:A polyester, which is employed as an ingredient of a lubricating composition (see Group III), has the formula: ROOCR1 COO[CH2C(CH3) (R7) CH2OOCR1 COO]nR where n is an integer, the Rs are alkyl groups having 4-18 carbon atoms, the R1s are either alkylene groups having 4-14 carbon atoms or phenylene groups, and the R7s are either methyl or ethyl groups. The polyester may be prepared by reaction, in one or more stages, of one or more dicarboxylic acids HOOCR1 COOH or the anhydrides of such acids (where they exist), one or more monohydric alcohols ROH and one of more diols HOCH2 C(CH3) (R7)CH2OH. In the preparation of the polyesters employed in the examples, HOOCR1COOH is one or more of sebacic acid, phthalic anhydride, 1, 1, 3-or 1, 3, 3-trimethyladipic acid or commercial isosebacic acid (a blend of 1-ethylsuberic acid, 1, 4-diethyladipic acid and sebacic acid), ROH is 2-ethylhexanol and the diol is 2, 2-dimethyl-1, 3-propanedio or 2-methyl-2-ethyl-1, 3-propanediol. For comparison purposes, polyesters are described prepared from (i) sebacic acid (with or without phthalic anhydride), 2-ethylhexanol and 1, 2-propylene glycol or (ii) sebacic acid, 2-ethylhexanol and tetraethylene glycol. Specification 824,249 is referred to.ALSO:A lubricating composition, suitable for the lubrication of aero gas turbine engines, comprises a blend of a liquid aliphatic diester of a saturated aliphatic dicarboxylic acid, and a polyester, soluble in the diester, and having the general formula: ROOCR1COO[CH2C (CH3)(R7)CH2OOCR1COO]nR where n is a integer, the Rs are alkyl groups having 4-18 carbon atoms, the R1s are either alkylene groups having 4-14 carbon atoms or phenylene groups, and the R7s are either methyl or ethyl groups, the relative proportions of diester and polyester in the blend being such that the viscosity of the blend at 210 DEG F. is 4-30 centistokes. The diesters may have the formula R4OOCR5COOR4 where R5 is an alkylene group having 4-14 carbon atoms and the R4s are alkyl groups, preferably branched-chain, having 4-18 carbon atoms. The polyesters may be prepared by reacting, in one or more stages, one or more dicarboxylic acids HOOCR1COOH or the anhydrides of such acids (where they exist), one or more monohydric alcohols ROH and one or more diols HOCH2C(CH3)(R7)CH2OH. The lubricating composition may also contain an antioxidant, such as phenothiazine, or a crystallization suppressant, such as a polymerized alkyl ester of acrylic or methacrylic acid. In the examples, lubricating compositions are described consisting of a diester (a blend of octyl nonyl sebacate, dioctyl sebacate and dinonyl sebacate prepared from sebacic acid, 2-ethylhexanol and 3,5,5-trimethylhexanol), a polyester and phenothiazine. In the preparation of the polyester, HOOCR1COOH is one or more of sebacic acid, phthalic anhydride, 1,1,3- or 1,3,3-trimethyladipic acid or commercial isosebacic acid (a blend of 1-ethylsuberic acid, 1,4-diethyladipic acid and sebacic acid), ROH is 2-ethylhexanol and the diol is 2,2-dimethyl-1,3 - propanediol or 2 - methyl - 2 - ethyl - 1,3 - propanediol. For comparison purposes, similar lubricating compositions are described wherein the polyester is derived from sebacic acid (with or without phthalic anhydride), 2-ethylhexanol and 1,2-propylene glycol, a crystallization suppressant (alkyl methacrylate polymer) also being present in one instance. Lubricating compositions are also described consisting of dioctyl or dinonyl sebacate and a polyester prepared from sebacic acid, 2-ethylhexanol and tetraethylene glycol. Specification 824,249 is referred to.