Principle of color stripping
Color stripping is the use of chemical action to destroy the dye on the fiber, so that it loses its color.
There are two main types of chemical stripping agents, one is the reductive stripping agent, it is through the destruction of the dye molecular structure of the color-emitting system to achieve the purpose of fading or elimination of color, such as azo structure of the dye, the azo group may be reduced to amino and lose color. But the reductant to some structure of the dye color system damage is reversible, and therefore its fading can be restored, such as the anthraquinone structure of the color system is so. Insurance powder, carved white powder is commonly used reductive color stripping agent. Another category is the oxidizing color stripping agent, which is commonly used is hydrogen peroxide and sodium hypochlorite. The oxidizing agent can cause the destruction of certain groups that make up the coloring system of the dye molecule under certain conditions, such as azo group decomposition, amino acid oxidation, hydroxymethylation, complex metal ion detachment, etc.. These irreversible structural changes, resulting in the fading or decolorization of dyes, and therefore theoretically oxidizing agents can be completely stripped of color treatment. This method is particularly effective for dyes with anthraquinone structure.
Commonly used dyestuff stripping
2.1 Stripping of reactive dyestuffs
Any reactive dyes containing metal complexes should first be boiled in a solution of metal multivalent stinging agent (2 g/l EDTA). Then thoroughly washed before alkaline reduction or oxidation stripping treatment. Complete stripping is usually done at high temperature in alkali and insurance powder for 30 minutes. After reductive stripping, full washing. Then cold bleaching in sodium hypochlorite solution. Process example:
Example of continuous color stripping process:
Dyeing defective cloth → dipping reduction solution (caustic soda 20 g / l, powdered safety 3O g / l) → 703 reduction steamer steam (100 ℃) → washing → drying
Dyeing cylinder stripping process example:
Color blemish cloth → scroll → hot water 2 channels → caustic soda 2 channels (20 g / l) → stripping color 8 channels (insurance powder 15 g / l, 60 ℃) hot water 4 channels → cold water 2 channels on the roll → conventional sodium hypochlorite flat bleaching process (NaClO 2.5 g / l, stacked 45 minutes).
2.2 sulfide dyes stripping color
Sulfur dyes on the color fabric correction, usually they are in the reducing agent blank solution (6 grams / liter full strength of sodium sulfide), in the completion of the possible high temperature treatment, in the re-color before reaching the coloring material part of the stripping. In severe cases, sodium hypochlorite or insurance powder must be adopted.
Example of light color:
Into the cloth → more dip a roll (sodium hypochlorite 5 ~ 6 g liters, 50 ℃) → 703 steamer (2 minutes) → full washing → drying.
Example of dark color:
Color defective cloth → rolling oxalic acid (1 5 g / l 40 ℃) → drying → rolling sodium hypochlorite (6 g / l, 30 ℃ l5 seconds) → full washing and drying
Example of intermittent process:
55% crystalline sodium sulfide:5-10 g/l; soda ash:2-5 g/l (or 36°BéNaOH 2-5 ml/l).
Temperature 80-100,time 15-30,bath ratio 1:30-40.
2.3 Acid dye stripping
Use ammonia (2O to 30 g/l), and anionic wetting agent (1 to 2 g/l), and boil for 30 to 45 minutes. Before the ammonia treatment, use the insurance powder (10 to 20 g/l) at 70℃ to help completely strip the color. After that, oxidation stripping method can also be adopted.
Under acidic conditions, the addition of very surfactant also has good color stripping effect. Alkaline stripping is also used.
Silk stripping process example:
Reduction stripping bleaching (soda ash 1g / L, Ping Ping plus O 2g / L, insurance powder 2-3g / L, temperature 60 ℃, time 30-45min, bath ratio 1:30) → pre-mordant treatment (heptahydrate ferrous sulfate 10g / L, 50% hypophosphoric acid 2g / L, formic acid pH 3-3.5, 80 ℃ to maintain 60min) → rinsing (80 ℃ cleaning 20min) → oxidation stripping Bleaching (35% hydrogen peroxide 10mL/L, sodium silicate 3-5g/L, temperature 70-8O ℃, time 45-90min, pH 8-1O) → cleaning
Example of wool color stripping process:
Nifantine AN:4; oxalic acid:2%; raise the temperature to boiling within 30 minutes and keep it at boiling point for 20-30 minutes; then wash it clean.
Example of nylon stripping process:
36°BéNaOH:1%-3%; Pingping plus O:15%-20%; synthetic cleaning agent:5%-8%; bath ratio:1:25-1:30; temperature:98-100℃; time:20-30min(until all decolorization).
After all stripping, gradually lower the temperature, fully wash to the net, then use 0.5mL/L acetic acid, 30 ℃, 10min to fully neutralize the residual alkali on the nylon, and then wash with water.
2.4 Reduction of dye stripping
Generally in the mixed system of sodium hydroxide and insurance powder, at a relatively high temperature, the fabric dye reduction again. Sometimes it is necessary to add polyvinylpyrrolidine solution, such as BASF's Albigen A.
Example of continuous color stripping process:
Dyeing defective fabric → dip rolling reduction solution (caustic soda 20 grams / liter, insurance powder 3O grams / liter) → 703 reduction steamer steam (100 ℃) → washing → drying
Example of intermittent color stripping process:
Pingping plus O:2-4g/l; 36°BéNaOH:12-15ml/l; insurance powder:5-6g/l.
The temperature of stripping treatment is 70-80℃, time is 30-60 minutes, bath ratio is 1:30-40.
2.5 Color stripping of disperse dyes
The following methods are usually adopted for stripping disperse dyes on polyester.
Method I: formaldehyde combined with sodium hyposulfite (carved white powder) and carrier, at 100 ℃ and pH 4-5 treatment; at 130 ℃, the treatment effect is more significant.
Method II: Sodium chlorite and anthranilic acid, treated at 100℃ and pH3.5.
The best results were obtained by method one treatment, followed by method two treatment. After treatment, it is possible to finish the set of black.
2.6 Stripping of cationic dyes
Disperse dyestuff stripping on polyester is usually done by the following methods:
In the bath containing 5 ml / l monoethanolamine and 5 g / l sodium chloride, at boiling point for 1 hour. The fabric is then cleaned and bleached for 30 minutes in a bath containing 5 ml/l sodium hypochlorite (150 g/l active chlorine), 5 g/l sodium nitrate (corrosion inhibitor), and pH adjusted to 4 to 4.5 with acid. After the fabric with sodium chloride sulfite (3 grams / liter) at 60 ℃ for 15 minutes, or 1-1.5 grams / liter of insurance powder at 85 ℃ for 20 to 30 minutes. And after washing clean.
Adopt clean detergent (0.5 to 1 gram / liter) and acetic acid boiling solution, at pH 4 under the treatment of colored fabrics l-2 hours can also achieve partial stripping effect.
2.7 insoluble azo dyes stripping
5 to l0 ml / l 38 ° Bé caustic soda, l to 2 ml / l of heat-stable dispersant, and 3 to 5 g / l of insurance powder treatment, plus 0.5 to l g / l anthraquinone powder. If there is enough insurance powder and caustic soda, anthraquinone will make the color stripping solution turn red. If it changes to yellow or brown, further caustic soda or safe powder must be added. The fabric should be washed well after stripping.
2.8 Paint stripping
Paint is difficult to peel off, generally adopt potassium permanganate to peel light.
Color blemish fabric → rolling potassium permanganate (18 grams / liter) → washing → rolling oxalic acid (20 grams / liter, 40 ℃) → washing → drying.
Commonly used finishing agent stripping
3.1 The stripping of color fixing agent
Color fixing agent Y can be stripped with a small amount of soda ash and Pingping plus O; polyamine cationic color fixing agent can be stripped by boiling with acetic acid.
3.2 Silicone oil and softener stripping
General softener can be removed by cleaning agent cleaning method, sometimes also adopt the method of soda ash plus cleaning agent; some softener must adopt the method of ant acid plus surfactant removal. Removal methods and process conditions must be tested by small samples.
Silicone oil is difficult to remove, but with a very surfactant, under strong alkaline conditions, the method of boiling can remove most of the silicone oil. Of course, these are subject to small sample test.
3.3 Resin finishing agent stripping
Resin finishing agent generally adopts the method of acid steam cleaning to remove, its typical process is: dip rolling acid (hydrochloric acid concentration of 1.6 grams / liter) → stacking (85 ℃ 10 minutes) → hot water washing → cold water washing → drying. With this process on the continuous flat track practice bleaching machine can strip the resin on the fabric.
Color completion correction principle and technology
4.1 color finish correction principle and technology
When the color weave finish does not meet the requirements, the need for correction. The principle of color correction is the principle of residual color. The so-called residual color, that is, two colors have the characteristics of mutual abatement. Mutual after-color pairs of colors are: red a green, orange a blue, yellow a purple. For example, if the red finish is too heavy, you can add a small amount of green paint to cut down. But the residual color is only used to adjust the color finish in small amount, if the amount is too large, it will affect the depth and vividness of the color, generally the amount is about lg / L.
Generally speaking, reactive dyestuff coloring fabric is more difficult to repair, reduction dyestuff coloring fabric back to repair convenient; sulfur dyestuff back to repair the color is difficult to manipulate, generally use reduction dyestuff plus or minus color; direct dyestuff can be used to add color back to repair, but the amount should be less than 1 g / L.
The common methods of color finish correction are water washing (for the finished color fabric color finish slightly deep, floating color more and water washing, soap washing fastness is not ideal back repair cloth repair color), shallow stripping (with reference to the stripping process of dyestuff, conditions than the normal stripping process is slight), rolling alkali steam cleaning (for alkali-sensitive dyestuff, mostly used for reactive dyestuff; such as with reactive black KNB coloring cloth such as color finish blue, then by rolling the appropriate amount of Caustic soda, supplemented by steam washing method to achieve the purpose of blue finish to light), rolling whitening agent (for the finished red cloth, very for the finished cloth dyed by reducing dyes, the color is more effective when the color is medium and light. Normal color finished shriveled dark can consider re-bleaching, but should be based on hydrogen peroxide bleaching, can avoid unnecessary color change.) The color of the paint, paint sets, etc.
4.2.2 color correction process examples: reactive dyes on the color reduction method
4.2.1 in the reduction of soap washing machine in the first five compartments flat washing tank, respectively, plus 1 g / L flat plus O boiling, after the flat wash, generally shallow 15%.
4.2.2 in the reduction soap washing machine in the first five compartments flat washing tank, respectively, plus lg / L flat plus O, 1mL / L glacial acetic acid, room temperature through the machine, can make orange finish shallow about 10%.
4.2.3 in the reduction machine rolling tank dip rolling 0.6mL / L bleach water, room temperature over the steamer, the first two frames of water washing tank without water, the last two frames of cold water washing, a frame of hot water washing, and then soap cooking, can be shallow 2 into, different concentrations of bleach water, stripping color depth is also different, bleach water stripping color finish slightly shriveled.
4.2.4 with 27.5% hydrogen peroxide 10L, hydrogen peroxide stabilizer 3L, 36 ° Bé caustic soda 2L, 209 cleaning agent 1L into 500L of water, steam in the reduction machine, and then five cells flat plus O cooking, soap cooking, can be shallow 15% into.
4.2.5 with baking soda 5-10g / L, steam stripping, washing soap cooking, can be light 10-20% into, after stripping the color finished blue.
4.2.6 with 10g / L caustic soda, steam stripping, washing soap cooking, can be shallow 20%-30% into the color finished slightly dark.
4.2.7 with sodium perborate 20g / L steam stripping color, can be shallow 10-15%.
4.2.8 roll dyeing machine with 27.5% hydrogen peroxide 1-5L, 70 ℃ run 2 channels, sampling, according to the color depth to manipulate the concentration of hydrogen peroxide and the number of channels, such as dark green go 2 channels can be shallow half into 10% or so, the color finish is not much change.
4.2.9 In the roll dyeing machine 250L water put 250mL bleaching water, room temperature go 2 channels, can strip shallow 10-15%.
4.2.1O in the volume dyeing machine can be added Pingping plus O and soda ash stripping light.
Dyeing defects back to repair process examples
5.1.1 Acrylonitrile fiber fabric color processing examples
5.1.1 Light colored flowers
18.104.22.168 Process flow:
Fabric, surfactant 1227, acetic acid → 30 minutes to 100 ℃, holding 30 minutes → 60 ℃ hot water washing → cold water washing → temperature 60 ℃, into the dye, acetic acid holding 10 minutes → gradually increase the temperature of 98 ℃, holding 40 minutes → gradually reduce the temperature of 60 ℃ out of the cloth.
22.214.171.124 stripping formula.
Surfactant 1227:2%; acetic acid 2.5%; bath ratio 1:10
126.96.36.199 Repeated dyeing formula:
Cationic dyestuff (converted to original process formula) 2O%; acetic acid 3%; bath ratio 1:20
5.1.2 Dark color flower
188.8.131.52 Process route.
Fabric, sodium hypochlorite, acetic acid → heating 100 ℃, 30 minutes → cooling water washing → sodium bisulfite → 60 ℃, 20 minutes → warm water washing → cold water washing → 6O ℃, into the dye, acetic acid → gradually rise to 100 ℃, holding 4O minutes → gradually cooling 60 ℃ out of the cloth.
5. 1. 2. 2 stripping color formula.
Sodium hypochlorite:2O%; acetic acid 10%.
Bath ratio 1:20
184.108.40.206 out of chlorine formula:
Sodium bisulfite 15%
Bath ratio 1:20
220.127.116.11 Repeated dyeing formula
Cationic dyestuff (converted to original process formula) 120%
Acetic acid 3%
Bath ratio 1:20
5.2 Nylon fabric color processing example
5.2.1 Mild color blossom
When the difference between the depth of the color flower is 20%-3O% of the depth of the color itself, generally adopt 5%-10% of Pingping plus O, bath ratio is the same as the color, heat preservation between 80℃-85℃, when the depth of the dyeing solution reaches about 20% of the depth of the color, then gradually increase the temperature to 100℃, heat preservation until the dye is completely absorbed by the fiber.
5.2.2 Moderate color flower
Medium color flower can adopt the method of partial color reduction and then add dyeing to the original depth.
Flat plus O 1O%-l5%
Bath ratio 1:20-1:25
Time 90 min-120min
After color reduction, the fabric is washed with hot water, then washed with cold water until it is clean, and then colored.
5.2.3 Grim color flower
Pingping plus O: 15%-20%
Synthetic cleaning agent: 5%-8%
Bath ratio 1:25-1:30
Time 20min a 30min (until all decolorization)
After all the color stripping, gradually lower the temperature, fully wash to the net, then use 0.5mL acetic acid, 30 ℃, 10min to fully neutralize the residual alkali, and then wash with water to re-color. Some colors should not be dyed again after stripping
Contact: Jeanne yang（MISS）
E-mail: [email protected]
Add: Room A2216/A2217,Double-Star Building,No 567 New South Middle Road, KunShan City JiangSu Province ,China.