Causes and countermeasures of color fastness and discoloration of fabrics:
1. Waterproof and oil-proof agent:
Different types of waterproof and oil-repellent products will cause different discolorations of the same fabric. The reason is that the molecular structures of waterproof and oil-repellent agents are different, and the solvents and emulsifiers they contain are also different. Water- and oil-repellent agents containing VCM (vinyl chloride) groups have greater discoloration effects than those without. Under acidic conditions, when the VCM group encounters water, the Cl atoms are easily dissociated to form HCl, which remains on the cloth surface. The higher the mass fraction, the greater the impact on color fastness. Therefore, high-quality products require small trials and process adjustments.
2.Dye:
Fabrics dyed with sensitive dyes need to strictly control the processing conditions during waterproof and oil-proof processing. For example, when fabrics dyed with disperse purple are set at high temperature (180-200°C), the blue light will deepen, the red light will decrease, and the color change will be above Level 1. The solution is to lower the temperature to 130-150°C and reduce the amount of waterproof and oil-repellent agent. In addition, under strong acidic conditions, the fabric dyed with disperse dye 3B red will have obvious blue spots or blue stripes after the fabric is padded and then set at high temperature. Disperse dye 3B red is not acid-resistant. It is ideal to keep the pH of the waterproof and oil-proof diluent at 6-7. It is not advisable to add too much acidic additives such as glacial acetic acid.
3. Fabric processing:
For some yarn-dyed decorative fabrics with low processing requirements, in order to reduce costs, printing and dyeing units often use gray fabrics to directly process waterproof and oil-proof fabrics, which will cause large color changes. Because there are more floating colors on the surface of the fabric, the floating colors on the fabric surface are washed away in large quantities when padding with the waterproof and oil-repellent agent working solution. The dyes used at the same time have poor sublimation fastness, and the color of the finished fabric becomes lighter. avoid. It is recommended to wash the fabric thoroughly before waterproofing and oil-proofing.
4. Compounding:
Waterproof and oil-repellent agents have a deepening effect on fabrics, and the deepening effect is more obvious when combined with softeners. For durable waterproof and oil-proof processing, cross-linking agents and catalytic additions need to be added to meet the requirements; melamine cross-linking agents are often added to chemical fiber fabrics to enhance the yellow light and reduce the red light of the fabric. Therefore, the dosage needs to be controlled when processing light-colored fabrics. Adding isocyanate to natural fiber fabrics shows better durability, but the molecules contain N elements, which will cause yellowing when set at high temperatures. The dosage should not be too high when processing white fabrics and brightly colored fabrics. It is best to conduct a small test first.
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