The yellowing of real silk is mainly caused by the oxidation and coloring of amino acid residues such as tryptophan and tyrosine in silk protein in the air. And the existence of light can promote this phenomenon.

There are several ways to prevent silk from turning yellow:

① Foreign Dye Digest reported that bleached silk was soaked in 0.5%NaOH aqueous solution for 3s, and then (80%) was put into the aqueous solution composed of 1% thiourea and 1, 3,5-tripropenyl hexahydrotriazine, and soaked at 70℃ for 30min. Then it was treated with 0.3%HCl at 70℃ for 30 minutes, washed with water and dried. The silk treated by the above method has an initial yellowing index of 2.8. 3.8 After 180 days.

② Chitosan treatment. Add 0.3- 1.5g chitosan into 300ml 1% acetic acid aqueous solution to prepare 0. 1% ~ 0.5% chitosan solution, and soak silk (10cm× 10cm) in this solution for 80 cm. The treated silk was irradiated by carbon arc lamp (20 hours and 40 hours), and its yellowing degree was determined by automatic Hunter white photometer. The results show that the yellowing degree of silk treated with chitosan is lower than that of untreated silk.

③ Treatment with anti-yellowing agent HN-200. Anti-yellowing agent HN-200 is an antioxidant produced by Japan Hydrazine Industry Company. Its function is to provide electrons to active free radicals or as hydrogen atom donors, so as to stop the chain-type automatic catalytic photooxidation reaction, thus providing effective anti-yellowing effect on real silk. The method is to treat silk with 0.2% HN-200 at 80℃ for 5 ~ 65438 00 minutes, and then dry it. After being irradiated by 100h xenon lamp, the increase of yellowing index (△Y 1) of treated silk is only about half of that of untreated silk. However, this anti-yellowing agent is water-soluble and has little affinity with fiber, so its washing resistance is not ideal.

(4) The composite processing technology of dimethylol ethylene urea resin and polyurethane. Using dimethylol ethylene urea resin (DMEU) and polyurethane 105 resin for composite processing of real silk, the anti-yellowing effect can be obtained. Bleached 07 silk crepe was soaked at room temperature100g/L, polyurethane 10540g/L, 20% magnesium chloride (based on resin weight) and 5% citric acid (based on resin weight) in working solution13min, and then dipped and rolled twice (the residual rate was 90) If 0.5% UV-284 (anti-UV finishing agent) and 1% HN-200 are added to the composite resin working solution, the effect will be better.