GB563745A - Improved method of softening silk - Google Patents

Abstract

Silk is softened by impregnating it with an aqueous liquid containing an emulsion of oil and sufficient acidic material to adjust the pH value to the range 3 to 5.8. The liquid may also contain a wetting and penetrating agent such as a surface-active alkali metal sulphate or sulphonate or a phospho-lipoid such as lecithin. Such an addition may also aid in the emulsification of the oil and may serve as a buffer for the acidic substance. Hosiery made from silk which has been softened by the liquid treatment, has improved stretch and tensile strength characteristics, improved form-fitting, and exhibits cleaner knitting stitch. Prior to the acidic softening bath treatment, the silk may be rinsed in a bath consisting essentially of an acidic material and a buffer which is present in an amount sufficient to adjust and maintain the pH value of the rinsing bath within the range 3.5-5.5. After the softening treatment and preferably after knitting, the silk may be subjected to a degumming treatment in a hot aqueous bath containing sufficient strong acid to give a pH value of 1-2.9. The softened and degummed silk may be subjected to a finishing or dyeing treatment in an aqueous bath having a pH value of about 5.2 to 6.5. In an example, the silk is softened with an aqueous emulsion of mineral oil containing the sodium salt of monoglyceryl lauryl sulphate as penetrant and emulsifying agent, and sufficient monoglyceryl lauryl sulphate to adjust the pH value. In another example, there is used an emulsion of lecithin oil (a crude lecithin composition containing coconut oil), and acetic acid buffered by sodium acetate. Instead of lecithin oil there may be used lecithin and mineral oil. In another example, there is used an emulsion of mineral oil, the sodium salt of monoglyceryl lauryl sulphate, sulphonated castor oil, and acetic acid. Instead of glyceryl lauryl sulphate there may be used sulphated cottonseed oil, sulphonated castor oil, oleyl sulphate, or an alkyl aryl sulphate. Citric acid may be used instead of acetic acid. The softening treatment is preferably carried out at elevated temperature. For the preliminary rinsing bath there may be used a solution of acetic acid buffered with sodium acetate, or of citric acid buffered with disodium hydrogen phosphate. The degumming of the softened silk may be effected by treatment with a hot dilute solution of hydrochloric acid and calcium chloride. The degummed silk may be finished by treatment with a hot dilute solution of octadecyl sulphate adjusted to a pH of 5.2-6.5. An acid dyestuff may be added and the bath may be heated to boiling point. Calcium chloride and sodium sulphate are added to the hot bath and heating is continued till the desired shade of colour is obtained. Alkyl sulphates or sulphonates may be added to retard the rate of dyeing. The dyed material is then washed.