Method for dyeing fibrous materials

A method for dyeing fibrous material comprising the steps of:

• (a) prescouring a fibrous material selected from the group consisting of aromatic polyamide fibers, polybenzimidazole fibers, aromatic polyimide fibers, fibers of copolymers of the monomers thereof, or blends thereof, with an aqueous bath comprising a salt of an aromatic sulfonic acid having 6 to 12 carbon atoms and
• (b) contacting a fibrous material with an aqueous dyebath comprising a mixture of a dye assistant and a dye soluble or dispersed with the dye assistant in the dyebath, the dye assistant comprising a salt of an aromatic sulfonic acid having 6 to 12 carbon atoms.

A method for dyeing fibrous material which is particularly adapted for use in reducing the adverse effect of dyeing methods on the flame resistant properties of fibrous material having inherent flame resistant properties, the method comprising contacting a fibrous material selected from the group consisting of aromatic polyamide fibers, polybenzimidazole fibers, aromatic polyimide fibers, fibers of copolymers of the monomers thereof, or blends thereof, with an aqueous dyebath comprising a mixture of a dye assistant comprising a salt of an aromatic sulfonic acid having 6 to 12 carbon atoms;

• an agent for providing the dye in solution and for carrying the dye into the fibrous material, wherein said agent is selected from the group consisting of N-substituted aromatic carbonamides and N,N-disubstituted aromatic carbonamides;
• and a dye soluble or dispersed with the dye assistant in the dyebath.

A method according to claim 35, wherein the step of contacting the fibrous material with the aqueous dyebath is conducted at a temperature of above about 250.degree. F. and at a pressure of above about 2.5 atm, and held at the temperature and pressure for about 30 minutes to about 1.5 hours.