Patent GB-694412-A (GB)
Title: Improvements in and relating to the preparation of lubricating greases
Filed: 1951-12-18
Abstract: A lubricating grease is prepared by dispersing a waterproofed clay or clay-like material in a lubricating oil in the presence of a polar organic compound miscible with the oil and having a dielectric constant greater than 10 at 20 DEG C.  An increase in the gelling power of the clay, and a reduction in the milling necessary are obtained.  The clay may be natural, particularly montmorillonite of high magnesia content, or synthetic clay or zeolite, e.g. made by coprecipitating silica and magnesia by adding magnesium chloride to potassium silicate solution, drying the gel, and heating with caustic soda at 240 DEG C and 450-550 p.s.i. to give a synthetic Hectorite. The magnesium chloride may be replaced by calcium, barium or aluminium chloride, and caustic soda by potash, ammonia or lithia.  A preferred class of clays contains 2-20 per cent of alkaline-earth metal.  The waterproofing may be effected by treating a clay hydrosol with a cationic surface active agent such as a quaternary ammonium compound or amine salt having at least one hydrocarbon radical of 12 or more carbon atoms or a partial amide of a fatty acid of at least 12 carbon atoms with a condensation product of ammonia or an amine with acrolein or its analogues or of ammonia with epichlorhydrin. The clay should contain at least 30 per cent by weight of hydrophobic surface active radicals.  Another method of waterproofing clays comprises treating with a solution of a salt capable upon heating of forming basic salts, e.g. lead, barium or strontium salts of fatty acids, washing out unadsorbed salt and heating at 100-435 DEG C for 1-24 hours.  Mineral lubricating oils are preferred but synthetic oils may be used such as alkylene oxide, glycol or olefin polymers, organic phosphates, silicone fluids, and carboxyclic esters.  The polar compound is preferably a liquid boiling below 150 DEG C and having a dielectric constant of 15-35 at 20 DEG C.  Typical compounds, including ketones, aldehydes, nitriles, acids, alcohols, nitrogen bases, nitro compounds, sulphates, and thiocyanates, are specified.  Oxygen-containing compounds of less than 8 carbon atoms are preferred.  Other polar compounds including hydrocarbons, esters, chlorinated hydrocarbons or phenols may also be present.  The polar compounds of dielectric constant above 10 are mixed with the waterproofed clay in a ratio between 1 : 10 and 10 : 1, and preferably amount to 10-200 per cent of the lubricating oil.  They may be mixed with the dry clay and the mixture milled with the oil, the polar compounds then being removed by heat or vacuum, followed if desired by further milling or shearing.  Alternatively, water-wet waterproofed clay is used, the ratio of polar compound to water being from 1 : 4 to 5 : 1.  In examples, a bentonite is treated with dimethyldiheptadecylammonium chloride, washed, dried, mixed with 10 per cent of isopropyl alcohol or 5 per cent of nitrobenzene, and milled with a mineral lubricating oil, the alcohol or nitrobenzene then being removed.  Other examples use as ingredients: hectorite, magnesium silicate or magnesium aluminium silicate; octadecylammonium chloride, 12-hydroxystearylammonium lactate or partial fatty acid amide of epichlorhydrin-ammonia condensation product; and methyl ethyl ketone, benzaldehyde, acetonitrile, pyridine, formic acid or dimethyl sulphate.