GB824388A - Improvements in or relating to dye solutions for the dip-staining of polyvinyl acetal sheets - Google Patents

Abstract

A dye solution for staining a sheet of plasticized polyvinyl acetal comprises an unsulphonated pyrazolone azo dye, a non-ionic wetting agent and a solvent consisting essentially of 23 to 27 volume per cent water and 73 to 77 volume per cent ethylene glycol monoethyl ether, said solution having a pH of 9-10.5 Specified unsulphonated pyrazolone azo dyes are 4-phenyl-azo-1-phenyl- (or o : m-dichlorophenyl) - 3 - methyl - 5 - hydroxypyrazol, 4 - o : m - dimethylphenyl - azo - 1 - phenyl - 3 - methyl - 5 - hydroxypyrazol, 4 - alpha - naphthyl - azo - 1 - phenyl - 3 - methyl - 5 - hydroxypyrazol, 4 - p - diphenyl - azo - 1 - phenyl - 3 - methyl-5-hydroxypyrazol and 4-phenylazo-diphenyl - azo - 1 - o : m - dichlorophenyl - 5 - hydroxypyrazol-3-carboxylic acid. These dyes are water-insoluble and provide the yellow component to the colouring of the dye solution. Preferably the dye solution is prepared so as to stain the plasticized polyvinyl acetal sheet a green colour and in this case a blue unsulphonated quinizarin-type dye (e.g. Nacelan Blue KB) is also present and a pink unsulphonated anthraquinone-type due (e.g. Nacelan Pink B) may be present. Specified non-ionic wetting agents are polyoxyethylene sorbitol tetralaurate, polyoxyethylene lauryl ether and a polyoxyethylene ether of sorbitan monolaurate. The solution is prepared by making concentrates of the dyes in ethylene glycol monoethyl ether and diluting suitable quantities of these concentrates together with the wetting agent with appropriate amounts of water and the glycol ether. Adjustments of pH during the preparation of the solution may be made with sodium hydroxide and acetic acid. The concentration of the wetting agent is about 0.05 to 0.5 weight per cent and the concentration of the yellow azo dye is preferably 0.17-0.18 weight per cent.