Patent GB-397470-A (GB)
Title: Improvements in or relating to the production of colourations on textile materials made of or containing cellulose esters
IPC: D06P5/15
Filed: 1932-02-19
Abstract: In the production of discharge effects on materials made of or containing cellulose esters, the materials are saponified after colouration with a ground colour but prior to discharge thereof. Suitable saponifying agents are caustic soda, caustic potash, sodium or potassium carbonate, sodium silicate or trisodium phosphate, which may be employed if desired in aqueous or alcoholic solution, and if desired in conjunction with other substances, e.g. swelling agents. The saponifying agent may be applied by any convenient method, e.g. by padding or other method of mechanical impregnation.  After application of the saponifying agent the material is preferably steamed, aged or dried to bring about or to complete saponification to the desired extent.  The amount of saponification necessary is small, but it is desirable to saponify so that there is a loss of weight of at least 5 per cent, e.g. 10-15 per cent or more in the case of cellulose acetate, or the equivalent in the case of other esters.  The discharge of the ground colouration may be effected with the aid of any suitable discharging agents, e.g. reducing discharging agents such as aldehyde or ketone sulphoxylates, particularly zinc formaldehyde sulphoxylate, hydrosulphites, stannous salts, e.g. stannous chloride, or oxidation discharges such as chlorates or chromates.  The discharge compositions may contain other desired ingredients, e.g. substances which assist the action of discharging agents, e.g. anthraquinone or hydroquinone, and swelling or delustring or relustring agents for the cellulose ester portion of the material, e.g. alcohols, phenol or urea. Coloured pattern effects may be produced by incorporating in the compositions dyestuffs resistant to the discharging agent but having an affinity for or capable of being fixed on the saponified fibre, or dyestuff components or leuco compounds which may subsequently be developed or oxidized on the fibre.  Where saponification has been carried out only to a small extent, dyestuffs employed in the colouration of cellulose ester materials may be used, whereas where saponification has been carried out to a greater extent, dyestuffs having an affinity for cotton may be employed.  The discharge composition may be applied in any convenient manner, e.g. by printing or stencilling. The process is applicable to material of any cellulose ester capable of saponification, e.g. materials made of or containing cellulose acetate, formate, propionate, or butyrate, alone or in admixture with other textile fibres, e.g. cellulose ether fibres, regenerated cellulose, cotton, wool or silk fibres.  By suitably adjusting the degree of saponification of the cellulose ester, valuable effects may be obtained on materials containing other fibres in addition to the cellulose ester, e.g. a mixed fabric containing cellulose acetate and cotton may be cross dyed with dyestuffs having an affinity for cellulose acetate and with dyestuffs having an affinity for cotton, the cellulose acetate saponified until it acquires affinity for cotton dyestuffs, and the material then printed with a discharge composition containing a dyestuff resistant thereto and having an affinity for cotton, producing a coloured pattern effect on a cross dyed ground.  In examples: (1) a woven cellulose acetate fabric dyed a red shade with 4-nitro-2-methoxybenzene-1-azo-4<1>-dimethylaminobenzene is saponified to an extent corresponding to a loss of weight of about 10 per cent by cover padding with a solution of sodium carbonate containing starch thickening and then drying and steaming, and is then washed off, dried, printed with a paste containing zinc formaldehyde sulphoxylate, methylated spirits, ethyl lactate and gum arabic thickening, dried, aged, washed and dried, yielding a white discharge on a red ground; (2) a woven cellulose acetate fabric dyed a red-violet shade with 2 : 4-dinitrobenzeneazo-4<1>-diethylaminobenzene is padded with caustic soda solution, squeezed, passed over heated drums to effect simultaneous drying and saponification corresponding to a loss of weight of about 5 per cent and is then printed, if desired after washing and drying, with a paste containing sodium formaldehyde sulphoxylate, potassium carbonate, methylated spirit, gum thickening and water, dried, steamed, washed off and dried, yielding a white discharge on a red-violet ground; coloured discharges may be obtained by incorporating vat dyestuffs in the printing paste; (3) a fabric consisting of equal parts of cotton and cellulose acetate and dyed in contrasting shades with 2-nitro-4-methylbenzeneazo-p-xylidine or the acetate and Chlorazol Fast Blue 2 BNS on the cotton, is padded with sodium carbonate solution, dried on a stenter, steamed, printed as in (1) or (2), steamed or aged, washed and dried yielding discharges on a two colour ground.