Patent GB-749455-A (GB)
Title: Improvements in or relating to synthetic esters
IPC: C08K5/11
Filed: 1953-05-18
Abstract: A resinous material comprises a major proportion of a plastic resinous material and a minor plasticising proportion of a complex ester obtained by esterifying a monohydric alcohol and a polyhydric alcohol with adipic acid containing a minor proportion which is more than 2 per cent by weight of an aliphatic dibasic carboxylic acid or acids of lower molecular weight (see Group IV (b)).  In an example different samples of a synthetic rubber of the butadiene-acrylonitrile copolymer type are plasticised with an ester obtained by esterifying adipic acid containing 5 per cent succinic acid and 5 per cent glutaric acid with a mixture of C8 oxo alcohol and 1,3-butylene glycol and also with an ester obtained by esterifying the crude adipic acid mixture obtained by blowing a mixture of cyclohexane, acetic acid, and cyclohexanone with air at 150 p.s.i.g. and 220-250 DEG  F. for a 2 hours, with a mixture of isooctyl alcohol and 1,3-butylene glycol. The Mooney viscosity values of the plasticised samples are lower than those of a sample plasticised with an ester obtained by esterifying commercial pure adipic acid with a mixture of C8 oxo alcohol and 1,3-butylene glycol.ALSO:The invention comprises as a new composition of matter the product of esterification of a monohydric alcohol and a polyhydric alcohol, preferably a glycol, with adipic acid containing a minor proportion which is more than 2 per cent by weight based on the total weight of the acid mixture of a dibasic aliphatic carboxylic acid or acids having less than 6 carbon atoms per molecule.  The adipic acid containing the minor proportion of aliphatic dibasic acid or acids may be obtained by the oxidation of cyclohexane at conditions conducive to the formation of adipic acid, e.g. by blowing cyclohexane with air at pressures of about 100-200 pounds per square inch gauge and temperatures of about 200-350 DEG F. for about 1 to 5 hours, if desired in the presence of a solvent such as a low molecular weight aliphatic acid.  On cooling the crude acids separate out as a solid mixture which may be filtered and dried prior to the esterification.  The crude product so formed contains about 1-5 per cent glutaric acid, 1-5 per cent succinic acid and 90-98 per cent adipic acid.  Other dibasic acids which may be present are malonic acid and the hydroxy acids corresponding to the dibasic acids.  The additional dibasic acids may be present in amounts of between 2 and 40 per cent by weight based on total acids.  The ester products are preferably the complex esters formed by reacting one mol. of the crude dibasic acid with one mol. of a monohydric alcohol and half mol. of a glycol.  Specified monohydric alcohols are branched chain aliphatic alcohols containing 7-15 carbon atoms per molecule, such as C7 oxo alcohol, 2-ethyl hexyl alcohol, iso-octyl alcohol, C8 oxo alcohol, C10 oxo alcohol, and C13 oxo alcohol. Specified glycols are tetramethylene glycol, tetrapropylene glycol and triethylene glycol.  The esters may be prepared by refluxing a mixture of the dibasic acid mixture with about an equimolar proportion of the monohydric alcohol and about half molar proportion of the glycol in the presence of a suitable diluent, preferably a hydrocarbon such as xylene or toluene, and an esterification catalyst, preferably a moderately strong acid catalyst or acid salt until the theoretical quantity of water for complete esterification is removed overhead.  The reaction mixture may be neutralized, washed and vacuum stripped to remove unconverted reactants.  In examples: (1) pure 98 per cent + adipic acid (commercial grade) is mixed with succinic acid (5 per cent) and glutaric (5 per cent) on the one hand and with 15 per cent glutaric acid on the other hand and the two acid mixtures separately esterified with a mixture of C8 oxo alcohol and 1,3-butylene glycol in the presence of xylene, sodium bisulphate and a small amount of phenothiazine.  The lubricating properties of the ester products are compared with esters prepared in the same way from the same alcohol and glycol but using pure adipic acid (commercial grade) alone; (2) a mixture of cyclohexane, acetic acid and cyclohexanone is blown with air at 150 p.s.i.g. and 220-250 DEG  F. for 2 hours and the solid products which separate out on cooling are filtered off, dried, and esterified with a mixture of iso-octyl alcohol and 1,4-butylene glycol, in the presence of xylene and 2,6 di-tertiary butyl 4-methyl phenol, the viscosity and pour point of the product being compared with those of an ester produced in a similar manner from commercial pure adipic acid, iso-octyl alcohol and 1,4-butylene glycol; (3) a complex ester is prepared as in (2) except that 1,3-butylene glycol is used instead of the 1,4-glycol and the viscosity and pour point of the product compared with those of two esters prepared from commercial pure adipic acid and the same alcohol and 1,3- and 1,4-butylene glycols respectively.  The esters are useful as lubricants (see Group III) and as plasticizers for plastic resinous materials (see Group IV (a)).ALSO:An ester lubricant comprising the product of esterification of a monohydric alcohol and a polyhydric alcohol, preferably a glycol, with adipic acid containing a minor proportion which is more than 2 per cent by weight based on the total weight of the acid mixture of a dibasic aliphatic carboxylic acid or acids having less than six carbon atoms per molecule (see Group IV(b)) may be blended with various addition agents to improve their usefulness as lubricants.  Specified addition agents are conventional anti-oxidants, viscosity index improvers, extreme pressure agents, dyes, and grease-making thickeners.  The acids present in the adipic acid are preferably succinic and glutaric acids although malonic acid and the hydroxy acids corresponding to the dibasic acids may also be present.  The preferred ester lubricants are those formed by reacting one mole of the dibasic acid mixture with one mole of a C7-C15 branched chain aliphatic monohydric alcohol and half mole of a glycol. Specified alcohols are C7 oxo alcohol, 2 - ethyl hexyl alcohol, isooctyl alcohol, C8 oxo alcohol, C10 oxo alcohol and C13 oxo alcohol and specified glycols are tetramethylene, tetra-propylene, and triethylene glycols.  The adipic acid mixture used in the esterification may be obtained by oxidizing cyclohexane at conditions conducive to the formation of adipic acid, e.g. by blowing cyclohexane with air at pressures of about 100-200 pounds per square inch gauge and temperatures of about 200-350 DEG F. for 1 to 5 hours.