The reason of yarn embrittlement after dyeing with sulphur black dye: sulphur black dye is a polymer compound with more sulfur, its structure contains disulfide bond and polysulfide bond, and it is very unstable. Especially under certain temperature and humidity, polysulfide bond can be oxidized by oxygen in the air to sulfur oxide, and further react with water molecules in the air to generate sulfuric acid, thus reducing yarn strength and fiber embrittlement. In serious cases, all fibers are embrittled into powder.

In order to reduce or prevent fiber embrittlement, it is necessary to pay attention to the following points:

1. The amount of sulfur black dye should be limited, and the amount of mercerizing special color dye should not exceed 700g / bag. Because of the high amount of dye, the chance of embrittlement is large, and the dyeing fastness is reduced, so it is difficult to wash with water.

2. After dyeing, it should be fully washed to prevent unclean washing, and the floating color on the yarn is easy to decompose into sulfuric acid during storage, so as to make the fiber brittle.

3. After dyeing, it is necessary to use urea, soda ash, sodium acetate, etc. to prevent embrittlement.

4. Before dyeing, the yarn is boiled with water, and the embrittlement degree of the dyed yarn is better than that of the alkali liquor.

5. After dyeing, the yarn should be dried in time. Because the wet yarn is easy to heat during stacking, the content of embrittlement inhibitor and the pH value of the yarn will be reduced, which is not good for embrittlement prevention. After drying, the yarn should be cooled naturally to reduce the temperature of the yarn to room temperature before packing. It is not easy to emit heat because it is packed immediately without cooling after drying, which increases the energy of acid generation and decomposition of dyes and increases the possibility of fiber embrittlement.

6. Anti embrittlement sulfur black dye is selected. Formaldehyde and chloroacetic acid have been added to this kind of dye in the process of manufacture. The sulfur atom which is easy to oxidize becomes a stable structure state, thus preventing the oxidation of sulfur atom to produce acid and making the fiber brittle.

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