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.
01 Cause
1. White Spots
1) Such as wax spots, pulp spots, etc., water droplets, hard water and sand defects;
2) The blank is not fully soaked before dyeing, resulting in white spots after dyeing ;
3) There are calcium spots and alkali spots on cotton fabrics;
4) When calcium hypochlorite is used in the bleaching process, the decomposed lime remains on the fabric and has not been washed. , a kind of white spot that resists dyeing is produced 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 cloth during the dyeing process dilutes the dye solution, and the fabric is stained Stained with floral wool;
1) The fabric is opaque after scouring, and the dyed base contains dye-repellent substances;
2) When the rough fabric is rolled and dyed, there are water stains on the fabric , and rolled into a cloth roll and left for too long, causing light water stains;
3) When dispersed blue dye is used, very light color shadow stains often appear on the cloth surface;
4) Reactive dyes are rolled and stacked, and the film is not wrapped tightly enough. Condensation water penetrates into the cloth rolls, causing light stains;
5) Direct dyes are not fixed after dyeing and encounter water droplets, causing light stains. .
3. Dark stains
The causes are related to whether the fabric is desized before dyeing, the alkali condition, the dyeing material operation, and the dye liquor The foam condition, whether there are colored cilia on the drying cylinder, the execution of the dyeing process, and whether there are heavy metal salts and other impurities on the fabric and in the dye liquor are all 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 indylin chromogenic solution ;
3) The polyester-cotton blended fabric is dyed and dried in a drying cylinder. The drying cylinder is stained with colored cilia, which turns into dark stains after hot melting;
4) Color phenol color base Poor dissolution is brought to the fabric and becomes irregular dark dye spots after pad dyeing. In addition, it will also occur if the roller has scars and is difficult to pad dry;
5) Temperature and pH of the ice dye developing solution The value is higher, forming tar-like scum;
6) The naphthol primer dries too quickly, easily causing dark spots;
7) Calcium, magnesium, zinc, aluminum, etc. The effect of metal ions 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 used It dissolves in hot water and is 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, which will affect the quality of the singeing.
4. Rust spots: related to rust
1) There is rust on the cloth before scouring and bleaching, which has not been removed by pre-treatment;
2) Contact with ironware during dyeing and finishing;
3) When dyeing with direct dyes, salt contains too much impurities, which corrodes the ironware and causes rust;
4) During processing Water contains rust.
5. Spots
Mainly occur during cooking. Uneven cooking causes poor circulation. In addition, insufficient materials are used and time is passed. Short, dirty desizing before scouring, too low temperature during scouring, etc.
6. Alkali spot
Mainly occurs in the scouring process. The scouring liquid contains a lot of impurities, the pot cover is not laid properly, and the scouring liquid circulates Defective, the residual liquid is not drained out completely after cooking the cloth, causing local air-drying, causing alkali-containing impurities to stick to the fabric. After scouring and steaming, it is not washed clean, the moisturizing and heat preservation during desizing is insufficient, air-drying occurs, or the fabric is not dried in time after mercerization. Dry, air-drying occurs.
7. Calcium spots
It is related to the presence of calcium ions. Hard water is used for scouring. When bleaching, the remaining calcium in the fabric is not removed.
8. Mildew spots
There is slurry on the fabric, and mildew spots can easily form under certain temperature and humidity.
02 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;
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) Adding sodium silicate to the scouring liquid can stabilize the iron contained in the scouring water;
2) The guide rollers and cloth rolls can be coated with baked ethylene oxide resin to prevent rust;
3) If there are rust spots on the fabric, wash them off with warm oxalic acid solution, and then wash them with clean water, otherwise the fibers will be brittle and damaged.
6. Measures and methods to prevent spots, alkali spots, calcium spots and mildew spots
1) Spots: Cook evenly, if not, cook 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 baking, 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. Add soap, etc. If calcium spots are found before dyeing, they can be washed with dilute hot hydrochloric acid;
4) Mildew spots;
7. Strictly control the quantity of products in process and try to avoid Stained with stains during transportation;
8. Pay attention to the chemical material operation to ensure that the dye is fully dissolved;
9. During dyeing, ensure that the process is on the truck;
10. Pay attention to the influence of foam during the dyeing process;
11. Try to��Remove the interference of heavy metal ions;
12. Clean the equipment;
03 Spot identification
1 2. Characteristics of mildew spots: different shapes, dotted and lumpy, and colors including yellow, green and black. Mild ones can be removed by cooking, while severe ones are difficult to remove and damage the 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. Water-repellent stains are mostly wax spots and raw spots.
4. Identification of wax spots and raw spots
1) Different colors: wax spots have a strong anti-staining effect. After dyeing, they appear white stains, and the spots are not as good as wax spots. The spots are strong, and the stains are light in color after dyeing;
2) Different shapes: wax spots are generally smaller in shape, and the shape of the defects is related to the waxing operation. Generally, it is not dyed in the warp direction and dyed in the weft direction. It may be slightly stain-repellent, so it will appear as long strips of stains in the meridional direction, and the spots will be larger in shape, like moire.
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 fabrics, most of which occur on the pot surface. Spots are caused by uncooked cooking, and the location of occurrence is uncertain;
2) Treat with dilute hot hydrochloric acid to remove calcium spots, but spots cannot be eliminated;
3) Color is not obtained 1: Calcium plaques are darker after staining, while spots are lighter after staining.
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 smoother;
2) Alkali After treatment, oil stains can be removed;
3) Washing with oxalic acid, rust 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 repelles dyeing. The color of stains is often the same color of the dyed finished product, or a single color of the 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 bath suspensions: The roller has scars and unevenness, which means 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 oil stains and printing defects: They mostly occur on thin, tight fabrics.
1) The heavy stains are damaged due to washing, absorb more color, and have a darker color;
2) The oil detergent used for washing has not been washed, and the gray fabric There are impurities around the area where the oil was washed, and the edges of the stains are repellent and the color is lighter.
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