Application Of Natural Dyes In Fresh Cocoon Dyeing

China is a big silk country with profound cultural background,and its silk output ranks first in the world.However,due to the backward production technology and the lack of high-grade silk brands,the added value of silk products in China is lower than that in developed countries.Therefore,China has not yet entered the ranks of the silk power,and the silk industry needs to be transformed and upgraded.At present,silk weaving enterprises in China mostly use dry cocoon silk reeling,and the quality of the products is better.Compared with dry cocoon reeling,fresh cocoon reeling saves cocoon drying process and energy consumption,and saves a lot of costs.In addition,the by-product such as fresh silkworm pupa in the process of fresh cocoon reeling has high economic value.With the maturity of silk reeling technology and freezing technology,more and more silk reeling enterprises will join the ranks of fresh silk reeling,fresh silk fabrics must have broad market prospects.Natural dyes have attracted more and more attention because of their health,environmental protection and good biocompatibility.The silk products dyed with natural dyes are popular.The application of natural dyes in fresh cocoon silk dyeing can greatly increase the added value of fresh cocoon silk products,enhance product competitiveness and draw more profits for enterprises.This paper mainly studies the application of grape skin,pomegranate skin and walnut green skin in the dyeing of fresh cocoon silk fabric.Firstly,the thermal and acid-base stability of three kinds of natural dyes were studied.The effects of dyeing method,dyeing temperature,pH value of dyeing bath and mordant on the dyeing performance and color characteristic value were analyzed.The effects of different mordants on the fastness indexes of fresh cocoon silk fabric were studied.Finally,the fastness indexes of fresh cocoon and ordinary silk fabrics were compared.The following conclusions are drawn:(1)The natural dyes of grape skin,pomegranate skin and walnut green skin have good thermal stability.They are stable in acidic condition,and unstable in alkaline condition.The natural dyes of grape skin have different degree of discoloration.Under acidic condition,the maximum absorption wavelength of natural dyes of grape skin is 445 nm,and the pH value is 7 when they are red-shifted to 502 nm.Under acidic conditions,the maximum absorption wavelength is 380 nm,and when the pH is 7,the red shift to 470 nm;under acidic conditions,the maximum absorption wavelength of walnut green skin natural dye is 511 nm,and when the pH is 7,the red shift to 516 nm.(2)Grape skin natural dyes should be used for dyeing fresh cocoon silk fabrics with post mordant dyeing method.The suitable dyeing process is as follows:dye 4%,dyeing temperature 90 C,heat preservation 60 min,dyeing bath pH 8,Yuanming powder lOg/L;appropriate mordant dyeing process is ferrous sulfate 5%,CA lg/L,temperature 60 C,time 30 min;grape skin natural dyes are directly dyed fresh.The color fastness of cocoon and silk fabrics to soaping and sunlight has not reached grade 3,and the color fastness to metal ion mordant dyeing has reached grade 3 or more.(3)Pre-mordant dyeing of fresh cocoon silk fabric with pomegranate skin natural dyestuff should be adopted,the pre-mordant dyeing process is ferrous sulfate 5%,CA 1 g/L,temperature 60 C,time 30 min;the appropriate dyeing process is:dyeing temperature 90 C,time 60 min,dyeing bath pH 5,90 C heat preservation 60 min;pomegranate skin natural dyestuff direct dyeing of fresh cocoon silk fabric resistance The color fastness to soaping and sunlight did not reach grade 3,and the color fastness to metal ion mordant dyeing was above grade 3.(4)Fresh cocoon and silk fabrics dyed with walnut green skin natural dyes should be mordant dyed in the same bath.The optimum dyeing process is as follows:dye 4%,ferrous sulfate 5%,dyeing bath pH 3,holding at 90 C for 60 min.The color fastness to soaping and sunshine of fresh cocoon silk fabric dyed with walnut green skin natural dyes has not reached grade 3,and the color fastness to metal ion mordant treatment has reached grade 3 or more.(5)Three kinds of natural dyes have good lifting power on fresh cocoon silk fabric,mordant can make fresh cocoon silk fabric get different color.(6)Under the same technological conditions,there was no significant difference in the color characteristic values between Fresh Cocoon Silk Dyed with grape skin,pomegranate skin and walnut green skin and ordinary silk fabric.