Ozone resistant, cationic dyeable nylon containing lithium, magnesium or calcium salts of sulfonated polystyrene copolymers

Claim 1

In a method to make a fiber-forming synthetic linear polyamide having a repeating structure of ##STR4## where R and R' are radicals of 3 to 13 carbon atoms, receptive to cationic dyes by the addition of a sulfonated polystyrene or salt thereof, said polyamide having from about 10 to about 60 amine gram equivalents per 10 6 grams of polymer and a ratio of less than ten sulfonate gram equivalents per amine gram equivalents, the improvement comprising adding to said polyamide a water soluble salt selected from the group consisting of the lithium, magnesium and calcium salts of a sulfonated copolymer, said salt sulfonated to over 90 percent of the theoretical maximum of complete monosulfonation of each styrene residue moiety and having a pH of between about 3 and 8, said sulfonated copolymer is selected from the group consisting of a copolymer containing at least 50% by weight of styrene or vinyl toluene reacted with each other or at least one of the following monomers or their next adjacent homologs, acrylonitrile, acrylate esters, methacrylate esters, acrylic acid, methacrylic acid, butene, methyl vinyl ether, ethylene, propene, 2-pentene, 2-methyl propene, said salt has a molecular weight of from about 15,000 to about 300,000 and the concentration of sulfonates present in the polyamide containing the salt is between about 50 and about 150 gram equivalents per 10 6 l grams polymer, and shaping said polyamide into a shaped article, whereby said dyed polyamide article has highly improved resistance to fading of the cationic dye due to exposure to ozone.