GB803057A - Dyed resinous pigments - Google Patents

Abstract

Finely-divided resinous particles of copolymers containing 70 to 96.5 per cent vinyl chloride, 1.5 to 25 per cent vinyl acetate and 2 to 20 per cent vinyl alcohol and obtained by the partial hydrolysis of vinyl chloride-vinyl acetate copolymers are dyed by immersing in a dye bath comprising a solvent, e.g. water, kerosene and mineral spirits, for the dye in which the resinous particles are insoluble. Hydrolysis may be effected by dissolving the vinyl chloride-vinyl acetate copolymers in solvents, e.g. methyl ethyl ketone and ethyl acetate, and heating with an aliphatic alcohol, e.g. methanol, ethanol and propanol, in the presence of a catalyst, e.g. sulphuric acid and sodium methylate. The modified copolymers may be recovered by precipitation with methanol. The dye-bath may contain wetting agents, e.g. iso-octyl phenyl ether of polyethylene glycol, and higher fatty acids, e.g. oleic acid, or metal soaps thereof, e.g. calcium oleate, which may be formed in situ. Daylight fluorescent dyes, e.g. rhodamine B base or hydrochloride and 4-amino-1,8-naphthol-21,41-dimethyl phenyl imide, may be used and the pigments mixed with varnish vehicles, e.g. an oil-modified alkyd resin derived from phthalic anhydride, polyhydric alcohols and soya fatty acids, mixed with aluminium stearate, a metal naphthenate and kerosene, and used in silk screen and letterpress inks and paints. Alternatively the resinous particles may be dyed in situ in the varnish vehicle.