GB768119A - Improvements in or relating to complex ester synthetic lubricants - Google Patents

Abstract

The invention comprises a complex ester containing at least one saturated aliphatic hydroxy monocarboxylic acid residue or at least one saturated aliphatic mercapto monocarboxylic acid residue, at least one residue selected from saturated aliphatic monohydric alcohol, saturated aliphatic monocarboxylic acid or saturated aliphatic mono mercaptan residues, and at least one saturated aliphatic dicarboxylic acid residue, the said complex ester containing at least two of the hydroxy acid or mercapto acid residues or at least one glycol residue, any glycol residue present not being joined to the hydroxy group of the hydroxy acid residue via an ether linkage, and the said complex ester being a liquid polyester containing no free hydroxyl, thiol or carboxyl groups, and in which hypothetical replacement of the ether oxygen atoms of the ester groups and of any ether oxygen atoms and any sulphide sulphur atoms that may be present in the complex ester by methylene groups would produce a polyketone with four or more carbonyl groups in the same carbon chain. The preferred complex esters are those which contain 20 to 130 carbon atoms per molecule. The complex esters may be of the following types: (1) alcohol-hydroxy acid-dibasic acid-hydroxy acid-alcohol; (2) monobasic acid-hydroxy acid-glycol-dibasic acid-alcohol; (3) monobasic acid - glycol - hydroxy acid - dibasic acid-alcohol; (4) alcohol-dibasic acid-hydroxy acid-glycol-dibasic acid-alcohol; (5) alcohol-dibasic acid-hydroxy acid-glycol-hydroxy acid-dibasic acid-alcohol; (6) alcohol-hydroxy acid-dibasic acid-glycol-hydroxy acid-dibasic acid-alcohol; (7) alcohol-dibasic acid-hydroxy acid-glycol-hydroxy acid-monobasic acid; (8) alcohol - hydroxy acid - dibasic acid - glycol-dibasic acid-hydroxy acid-alcohol; and (9) alcohol-hydroxy acid-dibasic acid-glycol-dibasic acid-alcohol. In the above types mercaptan may be substituted for the alcohol and mercapto acid may be substituted for the hydroxy acid. The ester may be prepared by a one step or two step technique. In the latter the central portion of the ester may be prepared in a first step by mixing the desired amount of the chosen reactants with a small amount of a catalyst and a water entrainer in a reaction zone and esterification effected at about 150 DEG to 220 DEG C. whilst in the second step a monobasic acid or a monohydric alcohol or mercaptan is added and esterification effected at about 200 DEG to 230 DEG C. to supply the terminating monofunctional residues of the ester. Alternatively, a half ester of one bifunctional material may be formed and then two mols. of such half ester connected with a second bifunctional material, e.g. equimolar quantities of an alcohol and a hydroxy acid may be reacted in a first step and two mols. of the resulting ester reacted with one mol. of a dibasic acid in a second step. In the one step process the desired reactants are reacted together at about 190 DEG to 230 DEG C. The complex ester product may be purified by stripping off any unreacted ingredients, water entrainer and light ends, washing with an alkaline solution to remove any residual acidity and finally filtering through an adsorbent material such as alumina or charcoal. If desired, an antioxidant, e.g. phenothiazine may be added to the esterification mixture. Specified monohydric alcohols are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, tert.-butyl, n-amyl, isoamyl, n-hexyl, isohexyl, 2-ethyl-1-butyl, 2-ethyl-1-hexyl, octyl, iso-octyl, 2-octyl, isononyl, decyl, lauryl, tetradecyl, pentadecyl, octadecyl, the C3 to C20 oxo alcohols, alcohols obtained by the catalytic reaction of carbon monoxide and hydrogen, those derived from the oxidation of petroleum fractions, from the Guerbat reaction, and from the hydration of olefins, and mixtures of such alcohols. The corresponding mercaptans may also be used. The preferred alcohols are oxo alcohols derived from polymers and copolymers of C3 and C4 monoolefins. Specified dibasic acids are malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, diglycolic, thiodiglycolic and thiodipropionic acids. Specified glycols include ethylene glycol, propane-, butane-, pentane- and hexane-diols and polyalkylene glycols, e.g. polyethylene and polypropylene glycols. Specified monobasic acids are acetic, propionic, butyric, 2-ethyl butyric, caproic, 2-ethyl hexanoic, caprylic, pelargonic, capric, lauric, myristic, stearic, methoxy propionic, ethoxyethoxy acetic, mono-2-ethyl hexyl adipate, mono- C8 oxo sebacate, acids obtained by caustic fusion of alcohols, and acids obtained by oxidation of petroleum fractions, and mixtures of such acids. Hydroxy- and mercapto-acids specified include glycolic, gamma-hydroxy-butyric, alpha-hydroxy caproic, alpha-hydroxy caprylic, lactic, beta-hydroxy propionic, 12-hydroxy-stearic and the corresponding mercapto acids, e.g. thioglycolic acid. Examples are given for the production of (1) an ester of type (4) above by one step esterification of a mixture of sebacic acid, polyethylene glycol 200, glycolic acid, and 2-ethyl hexanol in the presence of sodium bisulphate, heptane and a small amount of phenothiazine; and (2) of a complex ester of type (1) above from sebacic acid, glycolic acid, and a C10 oxo alcohol derived from propylene trimer, the C10 oxo glycolate being first formed and then reacted with sebacic acid, both stages being carried out in the presence of heptane and sodium bisulphate. The ester products are stated to be valuable lubricants and may be blended with other lubricants and additives (see Group III).ALSO:A lubricating composition comprises a complex ester containing at least one saturated aliphatic hydroxy- or mercaptomonocarboxylic acid residue, and at least one residue selected from saturated aliphatic monohydric alcohol, saturated aliphatic monocarboxylic acid or saturated aliphatic monomercaptan residues, and at least one saturated aliphatic dicarboxylic acid residue, the said complex ester containing at least two of the hydroxy acid or mercapto acid residues or at least one glycol residue, any glycol residue present not being joined to the hydroxy group of the hydroxy acid residue via an ether linkage, and the said complex ester being a liquid polyester containing no free hydroxyl, thiol or carboxy groups and in which hypothetical replacement of the ether oxygen atoms of the ester groups and of any ether oxygen atoms and any sulphide sulphur atoms that may be present by methylene groups would produce a polyketone with four or more carbonyl groups in the same carbon chain (see Group IV(b)). Several types of the complex ester are specified, the preferred types being those of the formula RXC(O) . (CH2)z . CH(R1) . X . C(O) . R2 . C(O) X . CH(R3) . (CH2)z . C(O) . XR4 wherein R and R4 are C1-C20 alkyl radicals, R2 is a divalent saturated C1-C20 hydrocarbon radical, R1 and R3 are hydrogen atoms or C1-C10 alkyl radicals, X is oxygen or sulphur, and z is an integer from 1 to 12, and R1XC(O)R12C(O)XCH(R11) (CH2)z1 . C(O)OR31O . C(O) . R41 . C(O)XR51 wherein R1 and R15 are C1-C20 alkyl groups, R11 is hydrogen or a C1-C10 alkyl radical, R21 and R41 are saturated divalent C1-C20 divalent hydrocarbon radicals, R13 is a saturated divalent hydrocarbon radical containing from 2 to 20 carbon atoms or a polyethyleneoxy radical, X is oxygen or sulphur and Z1 is an integer from 1 to 12. The complex esters may be blended together or mixed with viscosity index improvers such as polybutene and polyacrylate and polymethacrylate esters containing from 8 to 18 carbon atoms in the alcohol groups, pour point depressants, e.g. wax naphthalene condensation products, acrylate and methacrylate ester polymers, fumarate-vinyl ester copolymers, detergent inhibitors, extreme pressure additives, anti-rust agents, and oxidation inhibitors, e.g. phenothiazine. They may also be blended with mineral lubricating oils or with other synthetic lubricants, e.g. formals, polyalkylene ethers, dibasic acid esters, silicones, silicates, polyglycol ethers, and ether esters. They may also be used as the base oils to form grease compositions and the greases may be thickened with the common grease-forming soaps, e.g. the oleates, stearates, or hydroxy stearates of sodium, potassium, lithium, calcium, barium or strontium, or soaps formed from animal, fish, or vegetable oils. A list of dicarboxylic acids, monocarboxylic acids, hydroxy carboxylic acids, mercapto carboxylic acids, alcohols and glycols that may be used to prepare the complex esters is given. The dicarboxylic acids may contain interrupting oxygen or sulphur atoms, the glycols include polyalkylene glycols and the monobasic acids include alkoxy substituted acids. Specific complex esters referred to are an ester of the type:-2-ethylhexanol-sebacic acid-glycolic acidpolyethylene glycol 200-sebacic acid-2-ethyl hexanol and an ester of the type: - C10 oxo alcohol-glycolic acid-sebacic acidglycolic acid-C10 oxo alcohol, the oxo alcohol being derived from tripropylene, and the properties of these esters as lubricants are given.