Patent GB-685146-A (GB)
Title: Water-resistant greases
Filed: 1950-03-13
Abstract: A grease composition comprises a lubricating oil (other than a lubricating oil containing free hydroxy or mercapto groups), 1 to 20 per cent by weight, based on the lubricating oil, of an inorganic gel and 0.5 to 40 per cent, based on the gel, of a non-metallic aliphatic hydroxy or mercapto compound containing at least 8 carbon atoms in the molecule.  The lubricating oil may be a mineral oil or a synthetic oil prepared by cracking and polymerizing products of the Fischer-Tropsch process or a synthetic oleaginous compound within the lubricating oil viscosity range such as the alkyl esters of sebacic acid, high molecular weight aliphatic ethers such as n-hexyl ether, the aromatic acid esters such as the alkyl esters of benzoic and phthalic acids, and other compounds such as tri-cresyl phosphate, tributyl phosphate, butyl dibenzyl phosphate and the silicone oils. The gels include silica gel and the oxides and hydroxides of aluminium, chromium, copper, iron, manganese, titanium, nickel, calcium, germanium, molybdenum, thorium, tin and lead. Sulphide gels may also be used.  Preferably the gel is in the "aerogel" state.  The bulk density of the aerogel may be reduced by wetting it with acetone, isopentane, butyl alcohol, acetaldehyde or other low boiling liquid having no solvent or chemical action upon the aerogel, and then removing the solvent by warming or by vacuum.  Suitable hydroxy compounds include the hydroxy fatty acids, monohydric alcohols, monohydric alcohol-hydroxy fatty acid esters, polyhydric alcohols, esters of glycol and glycerol with hydroxy fatty acids, partial esters of polyhydric alcohols with any fatty acid and natural or modified natural products containing these compounds.  Specifically mentioned are 12-hydroxystearic acid, 9, 10-dihydroxystearic acids, 3, 12-dihydroypalmitic acid, 9, 10, 16-trihydroxypalmitic acid, ricinoleic acid, 19 - hydroxy - nonadecenoic acid, hydrogenated castor oil, glycerides of fatty acids containing more than 8 carbon atoms in the molecule and one or more OH groups separated from the -COOH group by at least one carbon atom, glycerides of hydroxy fatty acids produced by catalytic oxidation of hydrocarbon oils and waxes, mono-esters of glycerol with acids containing at least 8 carbon atoms in the molecule such as glyceryl monostearate, ethers of glycerol with alcohols containing 8 or more carbon atoms in the molecule such as the mono-decyl ether of glycerol, esters of C4-C16 monohydric alcohols with hydroxy fatty acids such as butyl 12 - hydroxystearate, 1, 4 - dodecanadiol, octanediol, 1, 2-decanediol, 1, 10-decanediol, lower polymers of polyethylene glycol and polymethylene glycol of molecular weight between 200 and 800, the monoethers of polyalkylene glycols such as the monobutyl ether of tetraethylene glycol, and octyl, decyl, dodecyl, octadecyl and other high molecular weight alcohols.  The corresponding mercapto compounds such as dodecyl mercaptan may also be used.  The grease may be prepared by dispersing an alcoholate of the metal of the gel in the lubricating medium and hydrolyzing to form the gel in situ and removing the alcohol, or by forming the hydrogel of the metal, dehydrating it by azeotropic distillation with alcohol, adding the alcohol suspension of the gel to the lubricating medium and removing the alcohol by distillation, preferably under vacuum.  The hydroxy or mercapto compound may be added to the prepared grease, or it may be dissolved in the lubricating oil and the gel dispersed or formed therein to give the grease.  The grease composition may be improved by heating at 100 DEG -200 DEG C for about 0.5-4 hours.  Other ingredients such as auxiliary gelling agents, corrosion inhibitors, extreme pressure additives (sulphurized lard oil, chlorinated paraffin wax), and oxidation inhibitors (phenylalpha- or beta-naphthylamine, alpha-naphthol, and the calcium salt of the condensation product of formaldehyde with p-tert-octyl phenol) may be present.  In an example grease is made by incorporating 10 per cent by weight of a silica aerogel in a low viscosity lubricating oil, and to this grease is added (based on the weight of the gel) (a) 10-25 per cent glycerol monostearate, (b) 9-21 per cent 12-hydroxystearic acid, (c) 10-22 per cent hydrogenated castor oil, (d) 20 per cent cetyl alcohol, (e) 20 per cent 1, 2-dodecanediol and (f) 20 per cent 1, 10 decamethylenediol.  U.S.A.  Specifications 2,260,625 and 2,449,253 are referred to.