Activated Imines as Intermediates in Base-Catalyzed Crosslinking of Cotton by N-Methylol Agents

Abstract

Certain N-methylolamides crosslink cotton cellulose at very moderate temperatures (105°-130°C) in the presence of alkaline catalysts, without the fabric yellowing that is usually associated with alkaline curing. Evidence is presented that the active crosslinking agents are alpha-, beta-unsaturated imines possessing CH2=N—C=O groups, and that these undergo base-catalyzed, Michael-type addition to cellulosic hydroxyl groups. N-Methylol agents whose struc tures preclude the formation of imines invariably failed to produce base-catalyzed crosslinking of cotton. Crosslinking of methyl hydrogen silicone to form silicone elastomer on cotton fibers occurred under the same conditions of base catalysis as did cellulose crosslinking. The two processes could be carried out simultaneously to yield a multi purpose finish imparting 287°-305° wrinkle recovery and a high degree of water repellency. Bonding of a phenolic dye to cotton while imparting durable-press properties also has been demonstrated. Tri(methoxymethyl)urea was capable only of single-ended attachment to cotton by alkaline catalysis, as predicted, and could then be made to pro duce delayed crosslinking by acid catalysis.