STUDIES OF SOME BASIC ASPECTS IN EASY-CARE COTTON FINISHING .4. EFFECT OF ACID SCAVENGERS ON FREE FORMALDEHYDE IN AND STRENGTH OF CROSSLINKED COTTON

When cotton fabric was padded with a solution containing dimethylol dihydroxy ethylene urea (DMDHEU) (200 g/l) at pH 2.5, batched for one hour, given a wash through padding with water, dried and cured, the crosslinked cotton showed a crease recovery of 287° and 307° in the dry and wet state respectively and a retained strength of ca. 68%. Incorporation of sodium hydroxide in the washing pad accentuates the retaining strength. The latter attained a value of ca. 90% without seriously affecting the dry and wet crease recovery. However, the amount of free formaldehyde in the crosslinked cotton was quite substantial. Increasing the concentration of NaOH up to 2 g/l in the washing pad caused a significant decrease in crease recovery of and a considerable increase in the amount of free formaldehyde in the crosslinked cotton fabric. Replacement of sodium hydroxide by sodium carbonate at a concentration of up to 2 g/l reduced the amount of free formaldehyde without adversely affecting the crease recovery. Utilization of urea in the washing pad at a concentration of up to 16 g/l provided advantages in terms of lesser amount of free formaldehyde (388 ppm), higher retaining strength (ca. 80%)and excellent crease recovery (above 280°). On the other hand, addition of sodium sulphite at a concentration of up to 8 g/l in the washing pad was accompanied by a significant decrease in crease recovery, and a significant increase in the amount of free formaldehyde. Nevertheless the role of sodium sulphite as acid and formaldehyde scavanger could be ameliorated through lowering the pH of DMDHEU padding bath or addition of sodium chloride or sodium dihydrogen phosphate to this bath. © 1979 Hüthig & Wepf Verlag, Basel