GB770889A - Improvements relating to fluorescent pigments - Google Patents

Abstract

A pigment for forming inks, enamels and coating compositions comprises a solid solution of a water-soluble fluorescent organic dyestuff in a thermoplastic resinous substrate consisting of a polymeric product of at least one vinyl type monomer, the ratio of dyestuff to substrate being from about 0.2 to about 5 per cent based on the weight of the resin, the pigment imparting a brilliant fluorescence in daylight or in ultra-violet light to a film comprising the pigment and a suitable binder or vehicle. The resinous substrate usually consists of polyacrylonitrile or a copolymer, the major portion of which is acrylonitrile. In one example to an aqueous dispersion of polyacrylonitrile containing polymer solids in the wet gel state or water slurried state glacial acetic acid was added with stirring to form an emulsion and then a water solution of Rhodamine 6G, Rhodamine B and Uramine B-4315. The mixture was stirred, filtered and washed, and the resulting pigment air-dried and ground and made into an enamel film with a long oil alkyd resin and a urea formaldehyde resin. Hydrochloric acid can be used instead of acetic acid or the acid omitted. In other examples the resinous substrate can be a copolymer of acrylonitrile containing 10 per cent glycidyl methacrylate, 10 per cent 2-hydroxyethylmethacrylate, 10 per cent dichlorostyrene, 10 per cent maleic anhydride, 5 or 10 per cent acrylamide or 5 per cent acrylic acid, or can be polyethylene, polychlorotrifluoroethylene, polydimethylstyrene or a copolymer of acrylonitrile, vinyl acetate and vinyl pyridine. In the latter case the copolymer was pretreated in a rising temperature bath prepared by mixing with water solutions of sodium chlorite, " Calgon " (Registered Trade Mark) and sulphated dodecyl alcohol (sodium salt) and adding concentrated nitric acid. The polyethylene, polychlorotrifluoroethylene and the polydimethylstyrene can be slurried in a mixture of water and alcohol. The water dispersion of polyacrylonitrile can have added to it the sodium salt of sulphated dodecyl alcohol or polyacrylonitrile powder can be dissolved in dimethyl formamide. In another example, the dye was dissolved in acrylonitrile and the product emulsion polymerized. A water dispersion of a polyamide resin can be added to the polyacrylonitrile-dye complex. Dyes or mixtures of dyes referred to in the Specification include Rhodamine 6G, Rhodamine B, Uramine B-4315, Auramine, Calcomine Brilliant Flavine S, Brilliant Sulfoflavine FS, Calcozine Flavine TG, 4 - methyl - 7 - diethylamino coumarin, Calcocid Blue EG, Calcocid Alizarine Blue SAPG, Calcocid Green G, 4-beta-hydroxyethylamino-1,8-naphthalic N-butylimide (Calcofluor Yellow HEB), Calcocid Malling Green 6B, Calcocid Milling Fast Green CR and Phthalocyamine Green. Specification 712,219 is referred to.