Patent GB-923735-A (GB)
Title: Improvements in coating and in coating compositions
IPC: C08L29/14
Filed: 1959-08-27
Abstract: A coating composition comprises a dispersion of polytetrafluoroethylene and a cellulose ester or ether, containing less than 40% of the film-forming constituent, of which the polytetrafluoroethylene comprises between 10 and 80% preferably from 40-60%.  A preferred composition comprises polytetrafluoroethylene with nitrocellulose or cellulose acetate, and optionally a cellulose ether.  Polyvinyl butyral or polyvinyl formal may also be present, and where the composition contains a cellulose ester, desirably in a proportion of 5-15% by weight thereof.  Wetting agents, and pigments of low friction characteristics, may also be present.  A preferred dispersing medium comprises a mixture of water with an organic solvent for the cellulose ester or ether present and for any modifying resin present.  The composition may be made by intimately mixing an aqueous dispersion of polytetrafluoroethylene with an organic solution of the cellulose ester or ether and any other constituents.  An adherent coating of low frictional characteristics may be formed on surfaces by applying the composition thereto, and drying at low temperature (e.g. at about atmospheric temperature) to obtain a protective and dry-film lubricant coating having as continuous phase the cellulose ester or ether and having a discontinuous phase of polytetrafluoroethylene dispersed therein. Specified cellulose esters include, in addition to nitrocellulose and cellulose acetate, cellulose acetate-butyrate, cellulose acetate-propionate, cellulose triacetate and cellulose propionate. Specified cellulose ester solvents and diluents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol, methyl acetate, ethyl acetate, n-butyl acetate, and isoamyl acetate, ethyl lactate, dioxane, methylene chloride, chloroform, mixtures of ethylene dichloride and methyl alcohol, nitropropane, tetrahydrofurane, and toluene, xylenes, heptanes, mineral spirits, ethyl alcohol, n-butyl alcohol and diethylene glycol monomethyl ether, and ethylene glycol monoethyl ether acetate.  Specified cellulose ethers include methyl cellulose, ethyl cellulose, ethyl hydroxy ethyl cellulose, carboxymethyl cellulose, carboxy ethyl cellulose and hydroxypropyl methyl cellulose.  Specified cellulose ether solvents and diluents include water (which may be used as the sole solvent where methyl cellulose, carboxy methyl cellulose and hydroxy ethyl cellulose are used), ethanol, iso-propanol, n-butanol, ethylene glycol, monoethyl ether, 1,6-hexylene glycol, ethyl acetate, n-butyl acetate, benzene, toluene, xylenes, heptanes, acetone, ethylene dichloride, methylene choloride and carbon tetrachloride. Specified wetting agents include sodium di-alkyl sulpho-succinates, polyoxyethylene lauryl ethers and stearyl dimethyl benzyl ammonium chloride.  Specified pigments of low friction characteristics include graphite, molybdenum disulphide, boron nitride, talc, vermiculite, tungsten disulphide, silver sulphate and yellow lead oxide.  The dispersions may be applied by brushing, dipping or spraying to metal, plastics, paper, glass, wood, leather, rubber or cork, and form dry-film lubricant coatings comparable in coefficient of friction with those obtained from heat-fused polytetrafluoroethylene, and having a good wear life under load.  Examples describe the application of such coatings to bearings, and to plain and phosphated steel panels.ALSO:A coating composition comprises a dispersion of polytetrafluoroethylene and a cellulose ester or ether, containing less than 40% of the film-forming constituent, of which the polytetrafluoroethylene comprises between 10 and 80% preferably from 40-60%.  A preferred composition comprises polytetrafluoroethylene with nitrocellulose or cellulose acetate, and optionally a cellulose ether.  Polyvinyl butyral or polyvinyl formal may also be present, and where the composition contains a cellulose ester, desirably in a proportion of 5-15% by weight thereof.  Wetting agents, and pigments of low friction characteristics, may also be present.  A preferred dispersing medium comprises a mixture of water with an organic solvent for the cellulose ester or ether present and for any modifying resin present.  The composition may be made by intimately mixing an aqueous dispersion of polytetrafluoroethylene with an organic solution of the cellulose ester or ether and any other constituents.  An adherent coating of low frictional characteristics may be formed on surfaces by applying the composition thereto, and drying at low temperature (e.g. at about atmospheric temperature) to obtain a protective and dry-film lubricant coating having as continuous phase the cellulose ester or ether and having a discontinuous phase of polytetrafluoroethylene dispersed therein. Specified cellulose esters include, in addition to nitrocellulose and cellulose acetate, cellulose acetate-butyrate, cellulose acetate-propionate, cellulose triacetate and cellulose propionate. Specified cellulose ester solvents and diluents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol, methyl acetate, ethyl acetate, n-butyl acetate, and isoamyl acetate, ethyl lactate, dioxane, methylene chloride, chloroform, mixtures of ethylene dichloride and methyl alcohol, nitro propane, tetrahydrofurane, and toluene, xylenes, heptanes, mineral spirits, ethyl alcohol, n-butyl alcohol and diethyleneglycol monomethyl ether, and ethylene glycol monoethyl ether acetate.  Specified cellulose ethers include methyl cellulose, ethyl cellulose, ethyl hydroxy ethyl cellulose, carboxymethyl cellulose, carboxy ethyl cellulose and hydroxypropyl methyl cellulose.  Specified cellulose ether solvents and diluents include water (which may be used as the sole solvent where methyl cellulose, carboxy methyl cellulose and hydroxy ethyl cellulose are used), ethanol, iso-propanol, n-butanol, ethylene glycol monoethyl ether, 1,6 hexylene glycol, ethyl acetate, n-butyl acetate, benzene, toluene, xylenes, heptanes, acetone, ethylene dichloride, methylene chloride and carbon tetrachloride. Specified wetting agents include sodium di-alkyl sulphosuccinates, polyoxyethylene lauryl ethers and stearyl dimethyl benzyl ammonium chloride.  Specified pigments of low friction characteristics include graphite, molybdenum disulphide, boron nitride, talc, vermiculite, tungsten disulphide, silver sulphate and yellow lead oxide.  The dispersions may be applied by brushing, dipping or spraying to metal, plastics, paper, glass, wood, leather, rubber or cork, and form dry-film lubricant coatings comparable in coefficient of friction with those obtained from heat-fused polytetrafluoroethylene, and having a good wear life under load.  Examples describe the application of such coatings to bearings.