Patent GB-844781-A (GB)
Title: Method of resisting radiation damage to organic fluids and compositions therefor
Filed: 1957-06-14
Abstract: Lubricating oil and grease compositions comprise a base oil and a homopolymer of an alpha lower alkyl (C1-C4) styrene which polymer is soluble in said base oil and more viscous than the oil; the polymer renders the oil resistant to nuclear radiations.  The base oil may be a petroleum-derived hydrocarbon fraction of suitable viscosity for the desired service or a synthetic oil such as hydrocarbons, esters, diesters and polyesters of suitable viscosity and preferably having 5% boiling points above 500 DEG F.  These include alkylbenzene mixtures of molecular weights of 250-400 such as are obtained as bottoms in detergent alkylbenzene production, octadecylbenzene, amylbiphenyl, hexadecane, polyamylnaphthalenes and esters of dicarboxylic aromatic or aliphatic acids with aliphatic alcohols, acid and alcohol each preferably containing 6 to 12 carbon atoms, such as di-(2-ethylhexyl), sebacate, didecylterephthalate and di-(2-ethylhexyl) orthophthalate.  As described below the oil may be partially or wholly replaced by polyethers.  The alkyl styrene polymers are preferably liquid polymers of alpha-methyl styrene. Suitable polymers usually have viscosities from 100 cps. to very high viscosities and should have a 5% boiling point above 300 DEG F. The mixture of polymer and base oil may contain 1-70% by weight of the polymer.  There is also preferably added to the mixture a minor amount of a polymeric material which tends to decrease in p viscosity with exposure to nuclear radiation; this decrease compensates for the increase in viscosity of the base oil and polymeric alkyl styrene on exposure to radiation, and the material should be added in an amount to offset substantially this thickening effect.  Suitable polymeric materials include polymers of acrylate added in amounts of 0.2-20% of the initial volume of the base fluid or methacrylate esters such as didodecylmethacrylate, and polymers of isobutyl, octyl or cetyl acrylate or amyl or n- or iso-hexyl methacrylate, copolymers of styrene and isobutylene, polymers of olefins such as propylene, butylene or isobutylene, polymers of vinyl ethers and polyethers which may wholly or partially replace the base oil as mentioned above.  Such polyethers should contain at least 3 ether linkages and molecular weights of 400-3000 are suitable. Polymers of 1,2-propene oxide are mentioned wherein the polymerization is initiated with aliphatic or aryl monohydric alcohols or esters, the terminal hydroxy groups of the polymer being esterified or etherified.  Generally amounts of 2-20% by weight of the base oil of the polymeric material is employed.  Other normal additives may be used such as antioxidants, e.g. 2-10% of organo selenides, metal deactivators, e.g. alizarin, quinizarin and mercaptobenzothiazole and free radical reaction inhibitors e.g. 0.2-8% of iodobenzene, iodonaphthalene and iodobiphenyl; such additives are generally used in amounts of 0.005-10% by weight of the oil composition.  Greases are prepared from the liquid compositions by incorporating a gelling agent such as aluminium or sodium soaps, fumed silica, graphite, carbon black, organophilic treated bentonites and the various gelforming finely divided oxides e.g. silica aerogels, silica hydrogels and estersils, used in amounts of 1-20% by weight of the final grease.