Classification of dyeing defects
Generally divided into appearance defects and internal defects .
Appearance defects are divided into: color does not conform to the sample, color spots, color difference, color flower, color willow, color gap, crepe printing, weft tilt, aurora, Stains, wind marks, etc.
Intrinsic defects are divided into: color fastness does not meet the requirements, shrinkage and deformation, brittleness, etc.
Appearance defects
Color difference:
Dyeing products exhibit different shades of color and different shades. The most common defects.
Color difference between pieces: color difference between pieces, for example, vat difference, (between intermittent dyeing vats)
Color difference within the same piece: There are color differences in the left, middle, right, front and back, front and back of the same product, for example: dark head and light tail, yin and yang sides, irregular color flowers.
Causes of color difference
1. Quality problems of dyed gray fabrics: After pre-treatment, uneven impurity removal, uneven water absorption, and uneven drying degree result in uneven absorption of dye liquor; uneven whiteness and uneven PH of the cloth surface, resulting in The color changes of dyes vary.
2. Dyeing material performance issues: Unreasonable dye selection, the selected dyes have different sensitivity to temperature and additives, and the dyeing speed of the dyes varies greatly. Flat cylinders are prone to side depth or head depth, and machine cylinders are prone to cylinder differences.
3. Material and liquid problems: uneven mixing of materials and improper feeding methods. For example, unstable concentration of the material and liquid can easily cause color difference between the front and rear.
4. Dyeing equipment: Due to unsatisfactory performance of the equipment, improper maintenance, and improper use, various color differences will occur.
For example: if the flat cylinder is not covered or has poor thermal insulation performance, the edge depth will be shallow
5. Reasons for dyeing operations: Improper operation by dyers makes the dyeing process conditions unstable and causes various color differences, such as: vat difference: During dyeing, the operation is not meticulous, resulting in differences in feeding materials, differences in heating speed, and differences in dyeing temperature control. There are differences in dyeing time and color fixation in water washing.
6. Inaccurate color matching and lax control after dyeing are also important reasons for tank differences.
7. Post-dyeing treatment issues: Uneven operation effects such as washing, soaping, and color fixation after dyeing can also cause various color differences.
8. Post-finishing problems: When the fabric is heat-set, the preheating time is too short, and the unstable temperature will cause color difference, uneven finishing effect, or heat Uneven processing temperatures and unstable uniformity will produce color differences.
Problems that should be paid attention to when identifying color difference
1. Same direction: Two pieces of fabric should compare their color differences in the warp and weft directions.
2. The number of folded layers is the same: both pieces of fabric should be single or multi-layer for comparison
3. The light source and environment should be stable and consistent: standard light box, darkroom.
Sehua:
Broadly speaking, any phenomenon of uneven color in dyed products is called color flowering.
In a narrow sense, some irregular color uneven phenomena.
Cause
1. The pre-treatment of dyed products is uneven. Impurity removal, water absorption, dyeing performance, cloth surface pH, dryness.
2. Use dyes with poor diffusion and leveling properties.
3. When dyeing, the dye solution or auxiliaries are added too quickly and the dye is not stirred in time.
4. In dyeing, the bath ratio is too small, the dye liquor circulation is not smooth or too slow, and the temperature rise rate is too fast.
Seliu:
Dyeing fabrics show straight strips of uneven color in the warp direction, also called stripes and warp stripes.
Cause
1 Gray fabric factor: The warp yarn composition is uneven or different, such as blended fabrics. The meridional density is uneven.
2 Improper seam head: the most common reason.
3 Equipment factors: If the expansion effect of the expansion roller in the dyeing machine is not ideal, there will be wrinkles in the warp direction. The cloth guide roller is uneven during dyeing.
Color file:
Dyeing fabrics have straight strips of uneven color in the weft direction, also called rung marks.
Cause
1 Gray fabric factor: The warp yarn composition is uneven or different, such as blended fabrics. The meridional density is uneven.
Storing it in folded form for too long before dyeing will cause it.
2 The seam head is improper.
3 Equipment factors: If the expansion effect of the expansion roller in the dyeing machine is not ideal, there will be wrinkles in the warp direction. The cloth guide roller is uneven during dyeing
Color spots and stains:
The dots on the dyed fabric that are significantly different from the dyed color are called color dots while small ones are called color stains.
Cause
1. Incomplete dissolution or aggregation of dyes in the dye liquor due to various reasons is the main cause of color spots and color stains. For example, the dye particles are too large, the water quality is poor, the influence of auxiliaries (too much salt, too much leveling agent), and the improper mixing method (too little water, inappropriate temperature)
2. blank�Fiber and acid, synthetic fiber and alkali.
5. Incomplete water washing, especially after treatment with acids, alkalis, and redox agents. Although the concentration of residual reagents is not large, it has After drying, the reagent concentration will become very large, and the fibers will be easily brittle (air-dried)
Shrinkage deformation DISCOVERY
Definition: The fabric shrinks when exposed to water.
1 Intrinsic reasons for fabrics: fiber absorbs water and swells (strong water absorption, shrinkage Large deformation, such as cotton) yarn thickness and yarn density of the fabric, (thick yarn is prone to shrinkage and deformation, high yarn density is prone to shrinkage and deformation) yarn twist. (Fabrics with twisted yarns are prone to shrinkage and deformation)
2 Reasons for weaving gray fabrics: weaving shrinkage, the weaving shrinkage is larger, the shrinkage is smaller; if the warp and weft are weaved, Excessive tension in the direction will cause shrinkage easily
3 Improper dyeing and finishing process: the tension in some links is too high, causing the fabric to bear greater tension, etc.
Methods to overcome shrinkage:
(1) Strengthen the specification inspection of gray fabrics, especially Inspection of warp and weft density and width.
(2) Reasonably control the tension of the fabric during the printing and dyeing process.
(3) Perform necessary pre-shrinking.
(4) Synthetic fibers must be shaped and finished to improve dimensional stability and moderate overfeeding.
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