Patent GB-805864-A (GB)
Title: Process for the preparation of lubricating grease compositions
IPC: C04B33/13
Filed: 1956-12-10
Abstract: A process for the preparation of lubricating grease compositions comprises adding an aminoplast-forming amino compound or hexamethylenetetramine to a fluid clay hydrogel, mechanically separating a substantial proportion of water from the hydrogel, displacing the remaining water by a volatile water-miscible organic liquid, adding a water-insoluble lubricating oil and evaporating the water-miscible organic liquid. The lubricating oil may be a paraffinic, naphthenic or asphaltic base lubricating oil or blend thereof or a synthetic oil such as the esters of phosphorus or silicon-containing acids and esters of aliphatic dicarboxylic acids with monohydric alcohols, e.g. tritolyl phosphate, dioctyl phthalate, bis-(2-ethyl hexyl) and bis-(3,5,5-trimethylhexyl) sebacates and tetrakis (2-ethyl hexyl) silicate.  Suitable base oils for high temperature greases are the halocarbon oils such as the fluorocarbons and the organisilicone liquids such as polymers of dimethyl silicone which are extensively described and exemplified.  The clay is preferably a high base exchange clay such as Wyoming bentonite or hectorite, though low base exchange clays such as Georgia clay and attapulgite may be used.  Suitable amino compounds include those with at least 2 amino groups per molecule, each being attached to an unsaturated carbon atom, e.g. urea, thio-urea, guanidine, melamine, and dicyandiamide and the compounds obtained by replacing one hydrogen atom in such compounds by an alkyl group, e.g. methyl, ethyl and propyl urea, thioureas and guanidines; aryl primary amines, e.g. aniline and its alkyl derivatives; and alkyl sulphonamides, e.g. benzene, toluene, and other alkaryl sulphonamides.  In all these compounds at least one amino group is attached to an unsaturated carbon or sulphur atom.  Volatile water-miscible organic liquids are those which are more volatile than the lubricating oil and preferably have a relatively low boiling point such as alcohols and ketones, e.g. methanol, ethanol, isopropyl alcohol, acetone and methyl ethyl ketone, esters, e.g. ethyl acetate, and mixtures of the above.  An optional feature of the invention is to treat the clay hydrogel with a mineral acid, e.g. phosphoric (which is preferred), hydrochloric or sulphuric, preferably before adding the amino compound.  A further optional feature of the invention is to use the process to prepare the aminoplast-coated clay greases of Specification 793,092 by subsequently adding an aldehyde, preferably with the lubricating oil, to react with the amine already present.  Suitable aldehydes include saturated and unsaturated aliphatic aldehydes or cyclic derivatives thereof, e.g. formaldehyde, acrolein, furfural, crotonaldehyde and acetaldehyde.  When hexamethylene tetramine is used, it may be decomposed to formaldehyde by heating the clay hydrogel and a phenoplast resin formed by adding a phenol, e.g. phenol, resorcinol, the cresols and alkyl phenols such as t-butyl phenol and t-amyl phenol.  Alternatively the amino compound added initially may not, or may only partially be used, to form the resin, which may be formed by subsequently adding an aldehyde and an amine or phenol, e.g. with the lubricating oil.  In several examples, the amino compounds used are aniline, melamine, hexamethylene tetramine, and benzidine and the oil in each is a dimethyl silicone fluid, the aldehydes used are paraformaldehyde and furfural and, where hexamethylene tetramine is decomposed, phenol is used to form a phenoplast resin.  Specification 736,270 also is referred to.ALSO:A process for the preparation of lubricating grease compositions (see Group III), comprises adding an aminoplast-forming amino compound or hexamethylene tetramine to a fluid clay hydrogel, mechanically separating a substantial proportion of water from the hydrogel, displacing the remaining water by a volatile water-miscible organic liquid, adding a water-insoluble lubricating oil and evaporating the water-miscible organic liquid. An optional feature of the invention is to use the process to prepare the aminoplast coated clay greases of Specification 793,092 by subsequently adding an aldehyde, preferably with the lubricating oil, to react with the amine and form an aminoplast resin in situ on the clay.  The clay is preferably a high base exchange clay such as Wyoming bentonite or Hectorite, though low base exchange clays such as Georgia clay and Attapulgite may be used.  The clay may be treated with a mineral acid, e.g. phosphoric, hydrochloric or sulphuric before adding the amino compound.  Suitable amino compounds include those with at least two amino groups per molecule, each being attached to an unsaturated carbon atom, e.g. urea, thiourea, guanidine, melamine and dicyandiamide and the compounds obtained by replacing an hydrogen atom in such compounds by an alkyl group, e.g. methyl, ethyl and propyl urea, thioureas and guanidines; aryl primary amines, e.g. aniline, its alkyl derivatives and benzidine; and alkyl sulphonamides, e.g. benzene and toluene and other alkaryl sulphonamides.  In all these compounds at least one amino group is attached to an unsaturated carbon or sulphur atom.  Aldehydes which may be added to form the aminoplast resin include saturated and unsaturated aliphatic aldehydes or cyclic derivatives thereof, e.g. formaldehyde, acrolein, furfural, crotonaldehyde and acetaldehyde. When hexamethylene tetramine is used it may be decomposed to formaldehyde by heating the clay hydrogel and a phenoplast resin formed in situ by adding a phenol, e.g. phenol, resorcinol, the cresols, and alkyl phenols such as t-butyl phenol and t-amyl phenol. The lubricating oil used as the basis for the greases may be paraffinic, naphthenic, asphaltic, halocarbon (e.g. fluorocarbon), synthetic (e.g. tritolyl phosphate, tetrakis (2-ethyl hexyl) silicate, dioctylphthalate, bis(2-ethyl hexyl) sebacate, bis(3,5,5-trimethylhexyl) sebacate); or silicones which may be prepared by the hydrolysis and condensation of compounds of the average formula R4-zSiXz wherein 2.25 \sF z \s0 1.5, R is a lower alkyl radical and X is a hydrolysable halogen or alkoxy group.  In the examples, the oil is a dimethyl silicone fluid and the clay is Hectorite in a 2 per cent slurry acidified with H3PO4; the resins are as follows, the amines being added first: (1) and (2) aniline-paraformaldehyde, (3) aniline-formalin, (4) anilinemelamine-paraformaldehyde, (5) hexamethylene tetramine-phenol-paraformaldehyde, (6) hexamethylene tetramine-phenol, (7) aniline-furfural, (8) melamine-paraformaldehyde, and (9) benzidine-paraformaldehyde. Specification 736,270, [Group III], also is referred to.