GB799042A - New synthetic esters and lubricants - Google Patents

Abstract

The invention comprises diesters of average molecular weight between 600 and 1000 and having the general formula <FORM:0799042/IV (b)/1> wherein R1 and R2 are alkyl radicals having from 5 to 12 carbon atoms, r, s, t and u represent the average number of oxyalkylene units present in the groups (C2H4O)r, (C3H6O)s, (C2H4O)t and (C3H6O)u respectively and p is an integer from 4 to 11, the weight ratio of oxyethylene content to oxypropylene content in the diesters being from 1:9 to 9:1. The units represented by -(C2H4O)- and -(C3H6O) are the oxyethylene -(CH2CH2O)- and oxypropylene -[(CH3)C2H3O]- units respectively and the average values of (r+s) and (t+u) will generally not exceed about 5. The diesters may be obtained by reacting an acid of the formula HOOC(OH2)pCOOH with a glycol monoalkyl ether of the formula RO(C2H4O)r(C3H6O)8H or with two dissimilar glycol monoalkyl ethers of the formul R1O(C2H4O)r(C3H6O)8H and <FORM:0799042/IV (b)/2> Thus the diester may be obtained by reacting the acid with 2 molecular proportions of the glycol monoalkyl ether to form the symmetrical diester or by reacting the acid with one monoalkyl ether in equimolecular proportions to form a half-ester and then reacting the half-ester with another glycol monoalkyl ether in equimolecular proportions to form the asymmetrical diester. The glycol monoalkyl ethers used to prepare the diesters are alcohol-alkylene oxide condensates and are generally mixtures of compounds of varying oxyalkylene content. They may be prepared by condensing the appropriate alcohol with a mixture of ethylene oxide and 1,2-propylene oxide, specified alcohols being amyl alcohol, n-hexyl alcohol, n-octyl alcohol, 2-ethyl hexanol, nonyl alcohol (mainly 3,5,5-trimethyl alcohol and "oxo" alcohols. In one method, the alkylene oxides are introduced under pressure into the alcohol which contains from 0.2 to 1.5 per cent by weight, based on total alcohol plus oxide, of sodium hydroxide, with agitation, the alcohol being contained in a pressure reactor maintained at 100-200 DEG C. The esterification with the dibasic acid is then carried out, sufficient sulphuric acid being added to neutralize the sodium hydroxide catalyst and to provide the esterification catalyst. A water-entraining agent such as benzene, toluene or xylene is added to assist in the removal of the water formed. In another method the mixture of alkylene oxides is introduced into the alcohol dropwise at atmospheric pressure and at 60 DEG C. using stannic chloride as catalyst over a period of 1 hour and the reaction completed by further heating at about 90 DEG C. The dibasic acid is then added and esterification effected using the same catalyst and in the presence of a water-entraining agent. The residual acidity of the synthetic esters may be reduced by drying the water-entraining agent, e.g. xylene, which leaves the reaction zone before returning it to the reaction zone. Drying may be effected by means of a desiccant, e.g. calcium chloride, at room temperature or by means of an auxiliary distillation unit. Specified dibasic acids are adipic, pimelic, suberic, azelaic, sebacic and brassylic acids. The diester products are stated to be useful as synthetic lubricants (see Group III). Examples are given for the production of diesters from sebacic acid and various condensates of 2-ethyl hexanol and nonyl alcohol (mainly 3,5,5-trimethylhexanol) respectively with mixtures of ethylene oxide and 1,2-propylene oxide in a weight ratio varying from 1:9 to 9:1 and the lubricating characteristics of the products are tabulated. The Provisional Specification includes similar diesters derived from either ethylene oxide or propylene oxide alone in addition to the mixture of the two oxides and an example is given for the production of a diester from sebacic acid and various condensation products of 2-ethyl hexanol and ethylene oxide.ALSO:A lubricating composition comprises (a) at least one diester having a molecular weight between 600 and 1000 and having the general formula: <FORM:0799042/III/1> wherein R1 and R2 are alkyl radicals of 5 to 12 carbon atoms, r, s, t and u represent the average number of oxyalkylene units present in the respective oxyalkylene groups and p is an integer from 4 to 11, the weight ratio of oxyethylene content to oxypropylene content in the diester being from 1 : 9 to 9 : 1 (see Group IV (b)), and either (b) at least one dialkyl ester of a dicarboxylic acid of the formula HOOC(CH2)vCOOH in which each alkyl radical contains 5 to 9 carbon atoms and v is an integer from 4 to 10, or (c) a polyalkylmethacrylate of average molecular weight between 20,000 and 120,000. The composition may also comprise all three types of constituents (a), (b) and (c). The oxyalkylene units in the groups -(C2H4O- and -(C3H6O)-are the oxyethylene -(CH2CH2O)- and oxypropylene -[CH3)C2H3O]- units respectively. Specific compositions described are: (1) blends of 2-ethylhexyl sebacate, dinonyl (mainly 3,5,5-trimethyl) sebacate, and a poly-2-ethyl hexylmethacrylate of average molecular weight 80,000 respectively, with a diester of the first mentioned formula derived from sebacic acid and various condensates of 2-ethyl hexanol with ethylene oxide-propylene oxide mixtures; (2) a blend of a similar diester of the first-mentioned formula with di-2-ethylhexyl sebacate and a poly-2-ethylhexylmethacrylate or polynonyl (mainly 3,5,5-trimethyl) methacrylate. The lubricating characteristics of these various blends are tabulated.