Patent GB-778691-A (GB)
Title: A process for the production of complex ester lubricants
Inventor: KRISCHAI HANS GEORG
IPC: C07C69/34
Filed: 1953-12-09
Abstract: Saturated complex esters are obtained by the esterification, in one or more stages, of glycols, aliphatic dicarboxylic acids and monohydric aliphatic alcohols in such a proportion to fulfillthe equation x+2y=2z, where x represents the total moles. of alcohol residues, y represents the total moles. of glycol residues and z represents the total moles. of dicarboxylic acid residues, in the presence of more than 10 per cent by weight of the reactants of a water carrier having a mid-boiling point that is higher than 20 DEG C., preferably 10 DEG  C., below the melting point of the dicarboxylic acids to remove the water formed during the esterification.  A suitable proportion of water carrier is such that the volume of water carrier in mls. divided by the weight of dicarboxylic acid in grams is greater than 0.8 and is preferably about 1.  Examples of water carriers that may be used are naphtha, and blends of toluene with xylene or of hydrocarbon commercial solvents.  The proportion of the reactants used may be adjusted to give a mixture of the complex ester and a diester.  Three methods are suitable for carrying out the above complex ester formation as follows: (1) a one stage reaction using all the reactants; (2) the reaction of equimolar amounts of the monohydric alcohol and dicarboxylic acid to form a half-ester, followed by reaction of 2 moles, of the half-ester with 1 mole. of glycol; and (3) reaction of 2 molar proportions of the dicarboxylic acid with 1 molar proportion of the glycol followed by esterification of the acid product with the alcohol.  Suitable dicarboxylic acids are of the formula HOOC(CH2)nCOOH, wherein n is less than 20 and including oxalic acid, e.g. adipic, azelaic and sebacic acid, and mixtures thereof. Suitable glycols are alkane diols having between 2 and 16 carbon atoms, preferably having the hydroxy groups on adjacent carbon atoms, and particularly 1,2-diols and polyglycols such as polyethylene glycols up to hexaethylene glycol and polyethylene glycol fractions whose average molecular weight does not substantially exceed that of hexaethylene glycol and polyalkylene glycols of the general formula HO(CR1R2-CR3R4O)nH, wherein R1, R2, R3 and R4 represent hydrogen, or any of these groups up to 2 are methyl groups, or any one of the groups is an ethyl group, and n is a number from 1 to 12.  Suitable monohydric aliphatic alcohols are 2-ethylhexanol, fatty alcohols, branched chain C8-C9 saturated alcohols and oxo alcohols-particularly those having 6 to 20 carbon atoms, including those which such alcohols predominate.  Alcohols which do not contain straight chain groups are preferred.  The esterification is conveniently carried out under reflux at elevated temperatures in the region of 120-160 DEG C., using a light hydrocarbon as the water carrier, and an alkali, preferably sodium, bisulphate or an aryl sulphonic acid as the esterification catalyst.  It is preferable to gradually add the other reactant or reactants to a slurry of the aliphatic dicarboxylic acid in the water carrier.  The preferred complex esters have the general formula R1OOCR2COOR3OOCR4 COOR5, wherein R1 and R5 are derived from the monohydric alcohol, R2 and R4 are derived from the dicarboxylic acids, and R3 is derived from a glycol such as a polyglycol.  In the example, a complex ester is formed by reacting sebacic acid with a commercial polyethylene glycol having a molecular weight of about 200, and the product is reacted with 2-ethylhexanol, naphtha having a mid-boiling point of 120 DEG  C. being used as the water carrier in a quantity of about 100 volume per cent based on the weight of sebacic acid, and sodium bisulphate as the catalyst.  A complex ester formed from the same reactants using a conventional quantity of the above naphtha as the water carrier is referred to. Specifications 659,103, 662,650, 664,992, [Group IV (a)], 666,697, 668,663, 699,402, 733,098 and 778,132 are referred to.ALSO:A lubricating composition comprises a mixture of a diester and a saturated complex ester obtained by the esterification, in one or more stages, of glycols, aliphatic dicarboxylic acids and monohydric alcohols in such a proportion to fulfill the equation x + 2y = 2z, where x represents the total moles of alcohol residues, y represents the total moles of glycol residues and z represents the total moles of dicarboxylic acid residues, in the presence of more than 10 per cent, based on the weight of the reactants, of a water carrier having a midboiling point that is higher than 20 DEG C., preferably 10 DEG C., below the melting point of the dicarboxylic acids to remove the water formed during the esterification (see Group IV(b)).  The proportion of the reactants (for example sebacic acid, polyethylene glycol and 2 - ethylhexanol) in the process referred to above may be adjusted to form a blend of a diester and the complex ester. Specifications 659,103, 662,650, 664,692, 666,697, 668,663, 699,402, 733,098 and 778,132 [Group IV(b)] are referred to.