Patent GB-804256-A (GB)
Title: Lubricating grease compositions
Filed: 1956-04-26
Abstract: A lubricating grease composition comprises a mineral lubricating oil which contains at least 1 wt. per cent of constituents which react with saturated aqueous mercuric chloride solution at 20 DEG  C. in 10 minutes to form solid matter removable by filtration (such as red and black oils), an inorganic gelling agent and at least 2.5 per cent by weight of a water-soluble aliphatic hydroxy carboxylic acid or the heat condensation product thereof with an aliphatic polyhydric alcohol.  The inorganic gelling agents may be clays such as bentonites or amorphous colloids such as silica, magnesia, alumina, silica-lime, and silica-magnesia aerogels.  The acids may be mono-hydroxy, e.g. glycollic, lactic, ethylene lactic, hydroxy caproic, alpha hydroxy butyric, acetonic, leucic, alpha hydroxy crotonic and alpha hydroxy valeric acids, poly hydroxy, e.g. glyceric, arabonic, gluconic, gulonic, galactonic, talonic and mannonic acids, or hydroxy polycarboxylic, e.g. citric, tartaric, tri-hydroxy glutaric, saccharic, tartronic and malic acids.  Many examples of alcohols suitable for forming the heat condensation products include lower alkylene glycols and carbohydrates.  The mixture subjected to heat condensation should contain a preponderance of the acid.  The predominating reactions of the condensation comprise the polymerization of the acid and the simultaneous esterification of both the acid and its polymer.  Optional ingredients include surface-active agents such as aliphatic amines containing at least one alkyl group of at least 10 carbon atoms and the corresponding ammonium salts, and polyamino hydroxy compounds, anti-oxidants such as aryl amines, strong acids such as HCl, H2SO4 and H3PO4 to improve the hydrophobic characteristics of the grease, and emulsifying agents such as alkali metal soaps to assist in the incorporation of the additives.  The gelling agent may be superficially reacted with an alcohol to form "ester sils."  Examples are given having the following constituents: (1) Hectorite clay, the amino amide formed between tall oil acids and a condensation product of epichlorhydrin and ammonia, phosphoric acid, black oil, and tartaric acid or lactic acid or a complex of tartaric acid and propylene glycol; (2) citric acid, silica aerogel, and a mineral lubricating oil; (3) finely divided tartaric acid, sodium stearate, colloidal bentonite and a red oil.  Specifications 672,650, 703,169, 728,779 and 778,822 are referred to.ALSO:The heat condensation products of watersoluble aliphatic hydroxy carboxylic acids with aliphatic polyhydric alcohols are added to mineral lubricating greases (see Group III).  The physical mixture, in which the acids should predominate (preferably 75 to 90 per cent weight acid with 25 to 10 per cent weight alcohol) is simply heated to 100 DEG  to 200 DEG  C. for 1/2 to 4 hours.  The predominating reactions of the condensation are polymerization of the acids and esterification of the acids and/or their polymers.  The course of its condensation is followed by measuring the water evolved which should preferably amount to 5 to 12 per cent of the original mixture.  Acids mentioned are monohydroxy carboxylic acids, e.g. glycollic, lactic, ethylene lactic, hydroxy caproic, acetonic, leucic and alpha-hydroxy butyric, crotonic and valeric acids; polyhydroxy carboxylic, e.g. glyceric, arabonic, gluconic, gulonic, galactonic, talonic and mannonic acids; and hydroxy polycarboxylic acids, e.g. citric, tartaric, trihydroxy glutaric, saccharic, tartronic and malic acids.  The preferred polyhydric alcohols are the C2-C6 alkylene glycols, but carbohydrates, e.g. ribose, arabinose, glycose, fructose, galactose, mannose, sorbitol and mannitol are also suitable.  Specifications 672,650, 703,169, 728,779 and 778,822, [all in Group III], are referred to.