..When tex cotton fabric is dyed with Haichang Blue RNX, defects such as serious color stripes and poor wet rubbing fastness appear. Which process is the cause?
Answer Haichang blue is a sulfur vat dye. Its molecular structure is similar to that of general sulfur dyes. Its coloring performance is between sulfur dyes and vat dyes. The fastness after coloring is better than that of sulfur dyes, especially the fastness to chlorine that is unmatched by ordinary sulfur dyes, and the color is bright and bright. The color fastness is inferior to vat dyes. There are generally three methods for coloring Haichang Blue, namely the alkali sulfide-safety powder method, the alkali sulfide-baking soda method, and the caustic soda-safety powder method. Among them, the caustic soda-insurant powder method has a good degree of dye reduction and bright colors after dyeing. If the caustic soda-safety powder method is used, the coloring defects are related to the drying cylinder, coloring process conditions, post-processing and other processes.
Now the precautions for each process are explained as follows: when drying the cylinder, if the dye Haichang blue is used 4.6%, 30% (36°Bé) caustic soda 5L/100kg cloth, 85% insurance powder 3%, alcohol 3%, Taikoo Oil 1.5%, liquor ratio 1:70, temperature 60~62℃, time 15min. If the amount of caustic soda and insurance powder is insufficient, the reduction temperature is too high, and the time is too short, you will find cyan foam suspended on the surface of the reducing liquid, and there are more sediments at the bottom of the reducing liquid, which is caused by insufficient reduction. During the dry vat reduction, the dry vat solution must remain clear to ensure that the coloring is defect-free. When dyeing, if the dosage of dye bath safety powder is low, the concentration of caustic soda is high, the coloring temperature is too high, the time is too long, or the safety powder is added improperly, oxidation blocks may also occur on the cloth surface, so the amount of caustic soda in the dye bath should be kept at 30%. (36°Bé) NaOH 5g/L, 85% insurance powder 11% (should be added in 4 times), and at the same time add 1.5% retarding agent bone glue. Liquor ratio 1:25, temperature 65~70℃, time 45min. During post-coloring treatment, local oxidation sometimes occurs, resulting in color wilting, color blocks, and streaking. This is due to the slow oxidation rate of the dye, uneven oxidation, and instantaneous dealkalization. For this reason, after coloring, the sweat cloth should be simmered in a tank first, then washed seven times with water, two times with HAc neutralization, four times with water, one time with 1 to 2 g/L baking soda (50°C), six times with water, dehydrated, and stacked. Leave to oxidize for more than 3 hours before soaping.
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