What are the better ways to prevent silk yellowing? Refined bleached silk and silk will cause yellowing discoloration during storage or consumption, which will reduce the value of the commodity. The reason for the yellowing of silk is mainly due to the oxidation and coloration of amino acid residues such as tryptophan and tyrosine in silk proteins in the air. The existence of light can promote this phenomenon. Metal Sunglasses,Polarized Sun Glasses,Double Rim Sunglasses,Double Bridge Metal Sunglasses Wenzhou Joysee Eyewear Company Ltd. , https://www.joysee-glasses.com
There are several ways to prevent the yellowing of silk.
1 "Foreign Dye Abstracts" reported that the bleached silk was soaked in 0.5% NaOH aqueous solution for 3 s, after padding (rolling rate 80%), 1% thiourea and 1% l, 3, 5 The aqueous solution of triacryloyl hexahydro-s-triazine was immersed at 70 ° C for 30 min and then washed with water. It was further treated with 0.3% HCl at 70 ° C for 30 min, washed with water and dried. The silk treated by the above method started to have a yellowing index of 2.8. After 180 days, the yellowing index was 3.8.
2 treated with chitosan. In 300 mL of 1% acetic acid aqueous solution, 0.3-1.5 g of chitosan was added to prepare a 0.1%-0.5% chitosan solution, and the silk (10 cm×10 cm) was placed in the solution. It is padded and sufficiently dried at 80 ° C to form a chitosan film on the surface of the silk fiber. The treated silk was irradiated with carbon arc light (20 h, 40 h), and the degree of yellowing was measured by an automatic Henzo white photometer. As a result, the chitin-treated silk has a low degree of yellowing compared to the untreated silk.
3 treated with anti-yellowing agent HN-200. The anti-yellowing agent HN-200 is an antioxidant produced by Nippon Paint Industries Co., Ltd. Its function is to provide electrons to the active radical or as a hydrogen atom donor, and to terminate the chain autocatalytic photooxidation reaction, thereby providing an effective anti-yellowing effect on the silk. The method is to treat the silk from 0.2% HN-200 at 80 ° C for 5 to 10 minutes and then dry. After the treated silk was irradiated with lOOh, the yellowing index increase value (ΔY1) was only about half of the untreated. However, such anti-yellowing agents are relatively water-soluble and have little affinity with fibers, so that the washing resistance is not ideal.
4 using dimethylol ethylene urea resin and polyurethane composite processing technology. The silk is processed by a combination of dimethylol ethylene urea resin (DMEU) and polyurethane resin, which can prevent yellowing. The method comprises the following steps: immersing the white silk bismuth in the working liquid composed of DMEUl00g/L, polyurethane l0540g/L, magnesium chloride 20% (for resin weight), citric acid 5% (for resin weight), and immersing for 15 minutes at room temperature. Two dip two rolling (rolling rate 90%, bath ratio 1:50) was prebaked at 80 ° C for 4 min, 140. The mixture was baked for 3 minutes at C, then soaped at 50 ° C for 10 minutes (1 g/L of soda ash and soap tablets), washed with water at 50 ° C, thoroughly washed with water and dried. The anti-yellowing effect is: 200h light △ Y1 is 8.69, untreated sample is 15.06. The process is better if 0.5% UV-284 (anti-UV finishing agent) and 1% HN-200 are added to the composite resin working fluid.