Patent GB-708035-A (GB)
Title: Improvements in or relating to reduction of acidity in synthetic ester lubricants bytreatment with olefin oxides
IPC: C07C69/34
Filed: 1952-01-22
Abstract: The residual acidity of a synthetic lubricant of the complex ester type as defined below is reduced by reacting the complex ester with propylene oxide or ethylene oxide, the reaction being carried out under pressure at between 150 DEG  and 300 DEG  C., preferably between 200 DEG  and 250 DEG  C., for a period of time sufficient to reduce the residual acidity of the complex ester to a value not exceeding 0.5 mg. KOH/g.  The complex ester lubricants are defined as those formed by reacting three or more of the following compounds: monohydric alcohols; monobasic acids; dibasic acids; and glycols (including polyglycols); at least one glycol and one dicarboxylic acid being employed, and are grouped under one of three types as follows: (I) wherein the ester has the formula R1COOR2OOCR3COOR4OOCR5 wherein R1 and R5 are the residues of the monocarboxylic acids, R2 and R4 are the residues from the glycols and R3 is the residue of the dicarboxylic acid; this type of ester is prepared by admixing the calculated amounts of the various compounds and carrying out a straightforward esterification of the reaction mixture or as in Specification 659,103 by reacting a monobasic acid with a glycol to form the half ester and then reacting two mols. of the half ester with one mol. of a dibasic acid; (II) wherein the ester has the formula R1OOCR2COOR3OOCR4COOR5 in which R1 and R5 are the residues of the alcohol, R2 and R4 are the residues of the dibasic acids and R3 is the residue of the glycol; these esters are prepared either by a straightforward esterification as for those of type (I), or by reacting an alcohol with a dibasic acid so as to form the half ester and then reacting two mols. of the half ester with one mol. of a glycol as in Specification 680,438; (III) having the formula R1OOCR2COOR3OOCR4 wherein R1 is the residue of the aliphatic alcohol, R2 the residue of the dibasic acid, R3 is the residue of the glycol and R4 the residue of the monobasic acid.  These esters may be prepared by reacting a dibasic acid and a glycol to form a half ester and then reacting the latter with a molar proportion each of a monohydric aliphatic alcohol and a monobasic acid as in Specification 662,650.  Specified monohydric alcohols whch may be used to prepare the complex esters employed in the invention include methyl, ethyl, n-butyl, n-hexyl, n-octyl, 2-ethylhexyl, cetyl, and oleyl alcohols, b -n-butyl (or dodecyl-) mercapto ethanol, b -tert.-octylmercapto ethanol, certain monoalkyl ethers of ethylene glycol, and of propylene glycol, diethylene glycol, dipropylene glycol and tripropylene glycol; propylene glycol monobutyl thioether, propylene glycol mono-tert.-octylthioether, propylene glycol mono-n-dodecylthioether, n-butyl (or tert.-octyl- or n-dodecyl) mercaptoethoxy ethanol, n-butyl (n-dodecyl- or tert.-octyl-) mercaptopropoxy propanol, and "Oxo" alcohols, e.g. those obtained from diisobutylene and C7 olefines.  Specified monobasic acids are acetic, propionic, butyric, valeric, caproic, caprylic, lauric, palmitic, stearic, oleic, b -methoxypropionic, b -ethoxypropionic, b -tert.-octoxypropionic, b -ethylmercaptopropionic, b -tert.-octylmercaptopropionic, and b -tert.-dodecylmercaptopropionic acids, and the various "Oxo" acids.  Dibasic acids specified are malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, and brassylic acids, pentadecanedicarboxylic acid, tetracosane dicarboxylic acid, C4-C24 alkenyl succinic acids (which may be obtained by condensing olefines or mixtures of olefines with maleic anhydride), diglycollic acid, thiodiglycollic acid, and C-alkyl derivatives of the above acids, e.g. 2-methyl adipic acid. The glycols employed in preparing the esters include ethylene glycol and any of its paraffinic homologues containing up to 18 carbon atoms, e.g. propylene, and butylene glycols, pinacone, and tri- (tetra- or penta-) methylene glycol.  The glycols may contain ether-oxygen and/or thioether sulphur atoms, thus di- (or tri-) ethylene glycol, or polyethylene glycols of the general formula HO(CH2CH2O)nCH2CH2OH where n is 1 to 26 and the polypropylene glycols of the general formula <FORM:0708035/IV (b)/1> where either R1 or R2 is a methyl group and the other is hydrogen and n is 1 to 20; thiodiglycol; 1,2 - bis - (2 - hydroxyethylmercapto) ethane, and bis-2-(2-hydroxyethoxy) ethyl sulphide may be used.  In carrying out the process the complex ester is placed in a pressure bomb, and the olefin oxide added. The bomb is then sealed and the temperature raised to the desired point and the reaction allowed to proceed until the acidity does not exceed 0.5 mg. KOH/g.  The amount of olefin oxide used is generally between 2 and 20 per cent, preferably from 4 to 8 per cent, by weight of the ester material.  In examples: (1) a mixture of iso-octyl alcohol, triethylene glycol, sebacic acid, adipic acid and xylene (as water entrainer) is refluxed until esterification is complete and the ester product then treated with ethylene oxide in a sealed bomb at 200 DEG  C. to reduce the acidity of the ester product to 0.1 mg. KOH/g.; (2) and (6) the ester product obtained by esterifying a mixture of iso-octyl alcohol, triethylene glycol and adipic acid as in (1) is treated with ethylene oxide at 250 DEG  C.; (3) as in (2) the ester being obtained from isodecyl alcohol (derived from the "Oxo" process), diethylene glycol and adipic acid; (4) as in (2) the ester being prepared from butanediol-1,3, caprylic acid, and adipic acid; (5) as in (2) the ester being prepared from butanediol-1,3, isooctyl alcohol and diglycollic acid; (7) an ester prepared as in (1) from tetramethylene glycol, iso-octyl alcohol and adipic acid is treated with propylene oxide at 225 DEG  C. to reduce the acidity to 0.5 mg. KOH/g.