Patent GB-752451-A (GB)
Title: Coating fluorescent lamp tube surfaces and the like
IPC: C09K11/02
Filed: 1951-12-20
Abstract: A coating suspension, particularly for coating fluorescent lamps, comprises a copolymer of isobutyl methacrylate and methacrylic acid and a solvent therefor and a luminescent material, such as a calcium halophosphate, uniformly suspended in the resultant solution. Solvents specified are xylol and butyl acetate which may contain minor amounts of dibutyl phthalate, toluol, n-octane or nonane-naphtha.  The suspension may contain a dispersing agent such as oleic acid.  The copolymer may be produced in a batch emulsion process by the copolymerization of isobutyl methacrylate with about 0.03 per cent by weight of methacrylic acid.  Prior to polymerization the monomer is washed with a slight excess of 10 per cent sodium hydroxide, and then with water until neutral.  An emulsifying agent such as sodium lauryl sulphate and a catalyst such as benzoyl peroxide are added to the batch which is heated to about 50 DEG  to 55 DEG  C. to initiate polymerization after completion of which the batch is dried and granulated in a flaking machine fitted with a screen having 10 wires per inch, the spaces between the wires being squares of side 0.079 inches.  The emulsifying agent can be removed by swelling the copolymer in a 40 per cent mixture of alcohol in water after which a dilute solution of hydrochloric acid is added and the material washed in a mixture of alcohol and water.  Instead of oleic acid, fatty acids in general, particularly the unsaturated fatty acids, and their amines and amides can be used as dispersing agents.  Specification 638,885, [Group III], is referred to.ALSO:A coating suspension, particularly for coating fluorescent lamps, comprises a copolymer of isobutyl methacrylate and methacrylic acid and a solvent therefor and a luminescent material uniformly suspended in the resultant solution.  The suspension can contain approximately 0.01 to 0.02 grs. of the co-polymer per cc. of solvent, such as xylol, and between 1 and 5 per cent, by weight of the luminescent material, of an agent, such as oleic acid, for assisting the dispersal of the luminescent material. The co-polymer can be produced by the co-polymerization of isobutyl methacrylate with about 0.03 per cent by weight of methacrylic acid to form a substance known as Emulsion Polymer AE, benzoyl peroxide being added as a catalyst and sodium lauryl sulphate as an emulsifying agent.  About 0.6 grs. of luminescent material per cc. of solvent can be used.  The luminescent material can be tin and manganese or antimony and manganese activated calcium halophosphate or inorganic silicates, tungstates, borates or phosphates, and can be of 5 microns particle size.  The coating suspension is applied to the inside surface of a lamp tube, for example by being flowed on to the top of the tube and allowed to drain down as described in Specification 638,885.  The coated tube is dried slowly at temperatures up to 90 DEG C., for example in about 30 to 50 minutes in a sheet metal tunnel and is thereafter baked at about 450 DEG C. in air to decompose and remove the co-polymer binder.  Instead of xylol, butyl acetate can be used as solvent and there can be added thereto about 10 per cent of toluol, normal octane, nonane-naphtha or other low boiling point hydrocarbons, or 1 per cent or less, e.g. 10 grs. per 1,000 cc. of solvent, of dibutyl phthalate.  Instead of oleic acid, fatty acids in general particularly the unsaturated fatty acids, and their amines and amides can be used as dispersing agents.