1, stripping principle:
Stripping is the use of a chemical action that destroys the dye on the fiber, causing it to lose color. There are mainly two types of chemical stripping agents that are commonly used. One is the reducing stripping agent, which is used to destroy or color the coloring system in the molecular structure of the dye. However, the damage of reductant to some structure dye color system is reversible, so the fading can be restored, such as the color system of the tantalum structure is the case; commonly used insurance powder, white powder and so on. The other type is an oxidative stripping agent. Under certain conditions, the oxidizing agent can cause the destruction of certain groups that constitute the dye chromophoric system. These irreversible structural changes result in fading or achromatism of the dye, so theoretically the oxidative stripping agent can be completely stripped. The use of this method for dyes with cerium structures is particularly effective. Hydrogen peroxide and sodium hypochlorite are commonly used.
2, stripping method requirements:
(1) The stripping method is simple and can effectively peel off the dye;
(2) The fibers are not severely damaged, and the stripped fibers still maintain good dyeability for re-staining;
(3) The cost of stripping is low.
3, stripping quality requirements:
The current evaluation indicators are: dye removal, feel, counterstaining performance, loss of strength and so on. Generally, in actual practice, the effect of stripping can be measured quantitatively from two aspects. First, the color becomes lighter, and second, the strength loss of dyeing products is small.
(1) Determination of lightness
The K/S value before and after stripping of the dyed product was measured on a computerized color matching system to calculate the K/S reduction percentage, and the stripping result was indicated by the K/S value and the percentage of reduction. The larger the K/S value of the stripping fabric, the deeper the color, ie, the worse the stripping effect. The greater the percent reduction in K/S, the better the stripping effect.
Decrease in K/S value = ×100%
In the formula m0-restore cleaning K/S value
M1 - K/S value after restoration and cleaning
(2) Determination of stripping strength loss
The breaking strength was measured on a fabric strength tester. The greater the difference between the values ​​before and after the strong force, the greater the damage of the stripping agent to the fabric.
Second, the domestic color removal repair
1, the domestic traditional stripping process
Up to now, the traditional stripping process is still in use. The following typical process is listed as follows:
Acrylic dye dyed acrylic fiber stripping method
Commonly used sodium hypochlorite stripping under acidic conditions: bath ratio 1:20, adding 20% ​​sodium hypochlorite, 10% acetic acid, 100 °C for 30 min, cooling and washing, then bath ratio 1:20, 15% sodium bisulfite, 60 °C 40min, then gradually cooling the cloth out of 60 °C.
According to the color depth, the actual operation process is as follows
(1) Light color flowers
Process flow:
Fabric, surfactant 1227, acetic acid → 30 minutes up to 100°C, heat 30 minutes → 60°C hot water wash → cold water wash → warm up 60°C, put dye, acetic acid to keep warm for 10 minutes → gradually warm up 98°C, keep warm for 40 minutes → gradually Cool down at 60°C.
Stripping formula:
Surfactant 1227: 2%; Acetic acid 2.5%; Bath ratio 1:10
Duplicate formula:
Cationic dye (converted to original recipe) 2O%; Acetic acid 3%; Bath ratio 1:20
(2) dark color flowers
Routing:
Fabric, sodium hypochlorite, acetic acid → heating temperature 100°C, 30 minutes → cooling and washing → sodium bisulfite → 60°C, 20 minutes → warm water washing → cold water washing → 6°C, inputting dye, acetic acid → gradually increasing to 100°C, keeping warm 40% → Gradually cool the cloth at 60°C.
Stripping formula:
Sodium hypochlorite: 20%; Acetic acid 10%; Bath ratio 1:20
Dechlorination formula:
Sodium bisulfite 15%, bath ratio 1:20
Duplicate formula:
Cationic dye (conversion to original recipe) 120%, acetic acid 3%, bath ratio 1:20
2. Domestic new stripping process:
There are many new types of decolorizers, among which WF-8836 is a stripping oil (Haisaibo Chemical Co., Ltd.), and the main component is a mixture of many high-molecular polymers. WF-8836 stripping oil can be used together with the insurance powder and caustic soda, and stripping or repairing the pure cotton and polyester-cotton blended fabric dyed with reactive dyes, vat dyes, and sulfur dyes.
The color-removing agent CY-730 (Shanghai Chuangyue Chemical Co., Ltd.) needs to be used together with the catalyst CY-770 in a ratio of 1:2. It has a wide range of applications and can be used for stripping a variety of dyes.
Cationic dye stripping agent CDA-01 (co-developed by Soochow University School of Materials and Guangdong Blue Ocean Printing and Dyeing Technology Co.) has strong stripping effect on cationic dyed acrylic fabrics, good stripping effect, timely stripping and repair, and The fabric is strong without damage.
Conclusion: There are many reasons for the color problem of acrylic fiber, and the general economic losses are relatively serious. At present, the ideal method is to strip the fabric color and re-stain, this method will not damage or change the dyeing groups inside the fiber, so If it is the color flower caused by the dyeing process, as long as it is the correct problem of the counterstaining process, it can be solved. If the raw material is caused by the process fluctuations in the production process, the color flower will still appear after the color reproduction. Therefore, such disputes can also become a test method.
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