Spots are a single color mixed with various spots or markings such as white, light, dark, dark or black. They come in various shapes and sizes, most of which are irregular and have many causes.
Causes
1. White stains
Such as wax spots, pulp spots, etc., water droplets , hard water and sand weaving defects; 2) The blank is not fully soaked before dyeing, causing white spots after dyeing; 3) There are calcium spots and alkali spots on the cotton fabric; 4) Calcium hypochlorite is used in the bleaching process to decompose it The lime residue remains on the fabric and has not been washed, resulting in white spots that resist dyeing after dyeing; 5) The semi-finished product is partially air-dried after mercerization, and the fabric is partially alkali-containing.
2. Light stains
There are dye repellents on the fabric, causing semi-repellency, or water dripping from the fabric during the dyeing process The dye solution is diluted, and the fabric is stained with floral wool; 1) The fabric is not cooked through, and the dye base contains dye-repellent substances; 2) When the rough fabric is rolled and dyed, there are water stains on the fabric, and it is rolled into the roll and left If used for too long, it will cause shallow water stains; 3) When dispersed blue dye is used, very light shadow stains will often appear on the cloth surface; 4) Reactive dyes are stacked in rolls and wrapped with films not tightly enough, causing condensation water to penetrate into the cloth rolls. Light-colored stains; 5) Light-colored stains caused by direct dye dyeing that has not been fixed and encounters water droplets.
3. Dark stains
The causes are related to whether the fabric is desized before dyeing, whether it is clean with alkali, and dyeing The chemical operation, the foam condition of the dye liquor, whether there are colored cilia on the drying cylinder, the execution of the dyeing process, and whether there are impurities such as heavy metal salts on the fabric and the dye liquor are closely related. 1) There are starch stains on the fabric, which turn into dark stains after dyeing; 2) The fabric appears as cloud-like stains on the foam in the indytin chromogenic solution; 3) The polyester-cotton blended fabric is dried in a dryer after dyeing , the drying cylinder is stained with colored cilia, which turns into dark stains after hot melting; 4) The phenol color base is poorly dissolved and is brought to the fabric, and becomes irregular dark stains after pad dyeing. In addition, the roller has scars and is difficult to pad. It will also occur when drying; 5) The temperature and pH value of the ice dye developing solution are high, forming tar-like scum; 6) The naphthol primer dries too fast, which can easily cause dark spots; 7) Calcium, magnesium, zinc, The effect of metal ions such as aluminum on diazonium salts; 8) Fabrics are in long-term contact with copper during the bleaching process and when priming with naphtha; 9) Neutral dyes are dissolved in hot water and are easy to condense and adhere to the fabric ;10) When dyeing with sulfur dyes, the semi-finished product will be unevenly desized, dirty, or have local air-drying alkali spots, which will cause erythema after dyeing; 11) During use, the cylinder of the cylinder singeing machine will gradually produce an oxide film, And affect the quality of singeing.
4. Rust spots: related to rust
There is rust on the cloth before scouring and bleaching, but it has not been removed by pre-treatment; 2 ) in contact with ironware during dyeing and finishing; 3) when jig dyeing with direct dyes, salt contains too much impurities, corroding ironware and causing rust; 4) water used in processing contains rust.
5. Spots
Mainly occur during cooking. Uneven cooking causes poor circulation. In addition, Insufficient materials, too short time, dirty desizing before scouring, too low temperature during scouring, etc.
6. Alkali spots
Mainly occur in the scouring process. The scouring liquid contains a lot of impurities and the pot cover is not After laying, the circulation of the scouring liquid is poor, and the residual liquid is not drained cleanly when the cloth is boiled, causing local air drying and causing alkali-containing impurities to stick to the fabric. After scouring and steaming, it is not washed clean, and the moisturizing and heat preservation during desizing is not enough, causing air drying. Or if it is not dried in time after mercerization, air drying occurs.
7. Calcium plaque
It is related to the existence of calcium ions. Use hard water for scouring and bleaching, and the remaining calcium in the fabric will not Go clean.
8. Mildew spots
There is slurry on the fabric, and mildew spots can easily form under certain temperature and humidity.
Overcoming methods
Dyeing finished products show white stains, light or dark stains
1. There should be no wax spots on the dyed base;
2. The desizing of semi-finished products must be clean;
3. Pay attention to the quality of the dyeing water;
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4. Prevent water droplets from dripping on the dyed base or during the dyeing process;
5. The following methods can be used to prevent and remove rust stains: 1) Add silicic acid to the scouring solution Sodium can stabilize the iron contained in the scouring water; 2) Apply baking ethylene oxide resin on the guide roller and cloth roller to prevent rust; 3) If there are rust spots on the fabric, wash them away with warm oxalic acid. After that, wash it with clean water, otherwise the fiber will be brittle;
6. Measures and methods to prevent spots, alkali spots, calcium spots, and mildew spots 1) Spots: Cooking should be even, such as If it is not good, cook it again; 2) Alkali spots: The pot cover should be laid out to prevent the cloth from floating out of the liquid. The residual liquid should be washed in time to prevent the cloth on the walls of the pot from being heated and baked, and the alkali on the cloth will Concentration will turn into uneven stains. Once found, they can be washed away with dilute hot hydrochloric acid; 3) Calcium spots: The scouring water should be softened before use. A water softener should be added to the scouring liquid first, and then soap, etc., such as If calcium spots are found before dyeing, they can be washed with dilute hot hydrochloric acid; 4) Mildew spots:
7. Strictly control the number of products in process and try to avoid stains during transportation;
8. Pay attention to the chemical material operation to ensure that the dye is fully dissolved;
9. Ensure that the process is on board during dyeing;
10. Pay attention to the influence of foam during the dyeing process ;
11. Try to eliminate the interference of heavy metal ions;
12. Clean the equipment well.
Identification of stains
1. Characteristics of mildew spots: different shapes, dotted and lumpy, and colors including yellow, green and black. The light ones can be removed by cooking, but the severe ones are difficult to remove.��Removed and damaged fibers. You can smell varying degrees of musty smell before the formation of mildew. It is especially easy to produce mildew during the yellow mold season, and the mildew is continuous and large in number.
2. Stains seen on semi-finished blanks and dyed finished products: stains on fabrics, some of which can be seen on semi-finished blanks, such as: stains, rust spots, calcium spots , mildew spots, raw spots (vaguely visible), alkali spots (after air-drying), but some stains are difficult to find even if they already exist before dyeing, such as wax spots and pulp spots.
3. Characteristics of water-repellent stains: As long as the quick hair method is used to identify the stains, water cannot wet the stains, and water-repellent stains are mostly wax spots or spots.
4. Identification of wax spots and raw spots 1) Different colors: wax spots have a strong anti-staining effect. They appear white stains after dyeing. Raw spots are not as strong as wax spots, and stains after dyeing. The color is light; 2) The shape is different: wax spots are generally small in shape, and the shape of the defects is related to the waxing operation. Generally, it is not dyed in the warp direction, but it is dyed in the weft direction or has slight dye repellency, so it is in the warp direction. The stains are long strips, and the raw spots are larger in shape, like cloud patterns.
5. Identification of raw spots and alkali spots 1) The locations of defects are different: Calcium spots are mainly the deposition of impurities on the surface of the fabric, most of which occur on the surface of the pot, while raw spots are caused by uncooked spots. So far, the location of occurrence is uncertain; 2) Treatment with dilute hot hydrochloric acid can remove calcium spots, but existing spots cannot be eliminated; 3) The color obtained is different: the calcium spots are darker after dyeing, while the spots are lighter after dyeing.
6. Identification of alkali spots: Alkali spots turn into yellow stains after drying, which can be seen on white cloth, and the pH value is above 7.
7. Identification of rust stains and oil stains 1) The shapes are different, the periphery of rust stains is irregular, while the outer contour of oil stains is smooth; 2) Oil stains can be removed after alkali treatment; 3) Washing with oxalic acid, rust stains Stains can be washed away, but oil stains cannot.
8. Identification of oil stains and color stains 1) Slight oil stains can be removed with detergent, but color stains cannot; 2) Colors vary, oil stains are light yellow or brown, and oil has a dye-repellent effect, while The color of stains is often the same color of the dyed finished product, or a single color of color matching dye.
9. Identification of stains caused by floral wool before and after pad dyeing: Before pad dyeing, there is floral wool on the fabric, resulting in a light color in some parts. After pad dyeing, there are stains on the drying cylinder. Colored piebald hair, which appears as dark spots after dyeing.
10. The difference between roller stains and dye liquor suspensions: The roller has scars and unevenness, which shows that the fabric is not easy to dry, the stains are regular, the stains and color stains are consistent in depth, and the dye is poorly dissolved Or there are suspended solids, causing stains on the fabric.
11. Characteristics of washing oil stains and printing defects: mostly occur on thin and tight fabrics 1) Heavy stains are damaged due to washing, absorb more color, and have a darker color; 2) Washing The detergent used has not been used, and there are impurities around the washed area of the gray fabric. The edges of the stains are resistant to dyeing, and the color is lighter.
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