Sythesis And Application Of Improver For Washing Fastness Of Acid Dyes-Dyed Fabrics

Color fastness to washing is one of the most important fastnesses of fabrics.It depends on the forces between dyes and fibers and the solubility of dyes in water.Silk is usually dyed by acid dyes,but color fastnesses of silk dyed by acid dye varied widely.Silk in dark shade always exhibit low fastness,and the washing fastness is only grade 1-2 and some kinds of dyes even achieve just grade 1.There are ways to improve the fastness of dyed silk,such as applying tannic acid and synthetic improvers,both of which have unappreciated characteristics.Imposing tannic acid on fabrics will result in yellowing while the hand of fabrics tends to become worse.Nowadays there are many kinds of finishing agents to silk,however,there are seldom methods which can improve fastness at least 3 grades without any influences on other wearabilities.We devoted to synthesize a polyurethane improver,blocking prepolymer with two kinds of blocking agents-oximes and amino silane coupling agent,got different kinds of improvers which showed different effects on washing fastness of dyed silk.Polyurethane blocked by oximes was much stable after long-time storage.They could improve color fastness to washing of dyed silk a lot.Owing to low hydrophilicity,its aqueous solution would become unstable as time went on.We took measures to solve this problem,but failed in increasing the hydrophilicity while still keeping the lifting effect of improver simultaneously.Polyurethanes blocked by amino silane coupling agents had high hydrophilicity,so their aqueous solutions were more stable in certain condition.Silane coupling agents had special groups, which could turn to hydroxyl after hydrolysis.They could form hydrogen bonds between fabrics and improver.In that way it was more difficult for dyes to fall off.Several amino silane coupling agents were chosen to block prepolymer.Finally KH550 was found performed better,so specific conditions of this blocking reaction,such as reaction temperature,time and pH value of hydrolysis,were discussed.After polyurethane blocked by KH550 was sythesized,the optimum technological condition of this improver was determined.Under this condition,bothof the color fastness to washing of dyed silk and dyed polyamide fiber could be improved.A good finishing agent could not have a bad effect on other characteristics.So we test other fastnesses of dyed fabric before and after imposing on this improver,only to find that this improver affect these fastnesses a little.Besides,the crease recovery angle of the finishing silk was found bigger than that of the unfinished.