Optische Aufhellungsmittel

摘要

Compounds of the formula wherein Y represents a -CN or a -COOR3 group, R1 and R2 each represent hydrogen or alkyl radicals containing up to 4 carbon atoms and R3 represents an alkyl radical containing up to 4 carbon atoms, may be obtained by reacting an o-aminophenol of the formula with an acid chloride of a thiophene carboxylic acid of the formula and subsequently heating the N-acyl compound thus obtained of the formula at an elevated temperature in an organic solvent boiling above 200 DEG C. The heating of the N-acyl compounds is suitably carried out under an inert gas at a temperature above 200 DEG C. in the presence of a catalyst, e.g. zinc chloride, p-toluene sulphonic acid, and the solvent is preferably 1,2,4-trichlorobenzene or a mixture of solvents containing trichlorobenzenes The compounds of the invention wherein the symbol Y represents cyano may be converted to esters wherein the radical Y is -COOR3 by hydrolysis with alcohols in the presence of hydrogen chloride, optionally followed by transesterification. The thiophene carboxylic acid starting material, which may be converted to its acid chloride by treatment with thionyl chloride, may be obtained by reacting a diazo salt of the formula wherein X represents the radical of a mineral acid with thiophene and acylating the product obtained followed by oxidation, e.g. with a hypochlorite.ALSO:Fibrous materials or foils may be optically brightened by treatment with a compound of the formula: wherein Y respresents a -CN or -COOR3 group, R1 and R2 represent hydrogen or alkyl radicals containing up to 4 carbon atoms and R3 represents an alkyl radical containing up to 4 carbon atoms, in a solution in an organic solvent or in an aqueous dispersion. The amount of the active compound employed is suitably 0.005 to 1% by weight of the material to be treated and the compositions may also include dispersing and chemical bleaching agents. The material to be treated is suitably made of or contains polyesters fibres or foils of the polyethylene terephthalate type.