A Corona Discharge Method of Producing Shrink-Resistant Wool and Mohair

Abstract

The felting shrinkage resistance imparted to wool by an air-corona field increases to a maximum near 100°C, decreases to a minimum at about 115-120°C, and then increases at higher temperatures. At 100°C and 415 Hz, the shrinkage resistance increases to a maximum at about 17.5 kV, then decreases rapidly. Ozone is believed not responsible for the shrinkage resistance because corona cells operating at about 90°C or higher generate little ozone. Chlorine gas in the air-corona field markedly increases the rate at . which wool is made shrink-resistant. An air/chlorine volume ratio of about 14/1 gives excellent results. If either nitrogen or oxygen, instead of air, is mixed with chlorine, only about half as much shrinkage resistance is achieved. A contribution of oxides of nitrogen to shrink resistance is suggested. Treatment effectiveness of an air-chlorine corona field is increased by adding hydrated salts to the wool or by the presence of water or HCI in the gas. Under conditions which produce satisfactory shrink resistance, the air-chlorine corona treatment causes no change in dyeing rate or in the solubility in acid or base. A continuous reactor is described which uses plane Pyrex cell electrodes. The thin webbing of fibers is transported through the cell by an endless belt. Several metals are satisfactory as belt material, but must be insulated electrically from grounded parts or high-voltage conductors so that arcing will not occur. In the presence of chlorine, the metal should be Teflon-coated.