Patent GB-862565-A (GB)
Title: Process for the manufacture of azo-dyestuff solutions
IPC: C09B33/147
Filed: 1957-03-05
Abstract: Filaments or films of, for example, cellulose acetate or triacetate, polyacrylonitrile or polyvinyl chloride are coloured by adding to the solutions or dopes from which they are obtained, by extrusion, casting or rolling, a solution of an azo dyestuff which is free from metal bound in complex union, which contains at least one group of weakly acid action and which is normally insoluble in water and aqueous alkaline media and normally insoluble or insufficiently soluble in organic solvents, which solution has been prepared by treating the dyestuff simultaneously with a strongly basic substance and a different weakly to moderately polar liquid which has a dielectric constant of at least 6 and an acidity less than that of ethyl alcohol.  The dyestuffs may contain one or more azo linkages and be prepared from diazo- or tetrazo-compounds free from solubilizing groups and coupling components such as aromatic hydroxy compounds, acyl-acetic acid arylides or pyrazolones which are likewise free from solubilizing groups.  The weakly acidic group is a phenolic hydroxy group, a carboxylic acid amide group attached to an aromatic nucleus or forming part of a heterocyclic ring, a cyanuric acid amide group or an enolizable group in an acyl-acetic acid arylide or in a pyrazolone derivative.  Specified strongly basic substances are the hydroxides, carbonates, alcoholates, enolates or amides of alkali metals; ammonia, hydrazine, hydroxylamine and guanidine; primary, secondary or tertiary mono- or polyamines and the corresponding quaternary ammonium bases and alkanolamines; saturated heterocyclic bases such as pyrrolidine, piperidine, piperazine and morpholine; and alkali metal salts of aminocarboxylic acids, and many examples are given. Specified weakly to moderately polar liquids are glycols, polyglycols and ethers thereof; liquid amines and alcohol amines, many of which are specified; condensation products of ethylene oxide with phenols, higher alcohols, amines or carboxylic acids; tetrahydrofurane, dimethyl sulphoxide, acetone, butyl acetate, g -butyrolactone, dimethyl formamide and acetonitrile.ALSO:Solutions of azo dyestuffs which are free from metal bound in complex union, which contain at least one group of weakly acid action and which are normally insoluble in water and aqueous alkaline media and normally insoluble or insufficiently soluble in organic solvents, are prepared by treating the dyestuff simultaneously with a strongly basic substance and a different weakly to moderately polar liquid which has a dielectric constant of at least 6 and an acidity less than that of ethyl alcohol.  The dyestuffs may contain one or more azo linkages and be prepared from diazo- or tetrazo-compounds free from solubilizing groups and coupling components such as aromatic hydroxy compounds, acyl-acetic acid arylides or pyrazolones which are likewise free from solubilizing groups.  The weakly acidic group is a phenolic hydroxy group, a carboxylic acid amide group attached to an aromatic nucleus or forming part of a heterocyclic ring, a cyanuric acid amide group or an enolizable group in an acyl-acetic acid arylide or in a pyrazolone derivative.  Specified strongly basic substances are the hydroxides, carbonates, alcoholates, enolates or amides of alkali metals; ammonia, hydrazine, hydroxylamine and guanidine; primary, secondary, or tertiary mono- or poly-amines and the corresponding quaternary ammonium bases and alkanolamines; saturated heterocyclic bases such as pyrrolidine, piperidine, piperazine and morpholine; and alkali metal salts of amino-carboxylic acids, and many examples are given.  Specified weakly to moderately polar liquids are glycols, polyglycols and ethers thereof; liquid amines and alcohol amines, many of which are specified; condensation products of ethylene oxide with phenols, higher alcohols, amines or carboxylic acids; tetrahydrofurane, dimethyl sulphoxide, acetone, butyl acetate, g -butyrolactone, dimethyl formamide and acetonitrile. Recovery, isolation or precipitation of the dyestuff from the solution may be effected by the addition of water or an acid or a non-polar solvent, or by the application of heat or reduced pressure if the basic compound is easily volatilized.  Thus, the azo dyestuffs may be purified, or converted into another crystalline form, or into a more finely dispersed form, by dissolution followed by reprecipitation.  Textile materials may be dyed or printed with the solution followed by insolubilization of the dyestuff as described above, or alternatively, the textile may be impregnated with an aqueous suspension of the dyestuff, dried, treated with the solubilizing mixture and finally treated to effect reprecipitation of the dyestuff.  The dyestuff solution may also be added to spinning solutions or dopes from which filaments or films are extruded, the so-formed products then being treated to remove the solubilizing mixture.  The solubilizing mixture may also be employed for stripping or levelling dyeings produced with the azo dyestuffs.  Examples describe the use of the solutions for dyeing cellulose acetate or triacetate, nylon, polyacrylonitrile and polyester fibres, for spindyeing cellulose acetate and polyacrylonitrile fibres and for colouring films or sheets of cellulose acetate or triacetate, polyacrylonitrile and polyvinyl chloride by adding the dyestuff solution to the dope from which the films are cast or rolled.