| 摘要 |
In a process for preventing or reducing discoloration by coloured liquids of polyamide articles having reactive groups capable of acting as carriers for colorants, the articles are treated with a selective light absorbing substance whose light absorption lies beyond the visible range and which has like dyestuffs an affinity for the reactive groups of the polyamide. Specified light absorbing substances are aralkylsulphonic acid salts, dialkylsulphonic acid salts, naphthalene sulphonic acid salts and tannin. The articles may contain pigments which are not chemically reactive with the polyamides, e.g. titanium dioxide. In the examples, cups made of polyamides: (1) are treated with a boiling aqueous condensate of naphthalene sulphonic acid, oxydianyl sulphone and formaldehyde containing acetic acid; (2) which have been dyed yellow are treated with a boiling solution of "Nylotan" (Registered Trade Mark) containing acetic acid. |
