Mercerizing

(from the name of the English inventor John Mercer, 1791-1866).

(1) A stage in the production of viscose; it consists in the treatment of cellulose with a concentrated aqueous solution of NaOH at 20°-60°C to produce alkaline cellulose. The process takes place in apparatus with periodic action (bath presses) or continuous action. A bath press is a metal tank in which the sheets of cellulose are pressed by a piston after treatment with alkali. The apparatus is designed for a load of 250-500 kg of cellulose; the operation cycle is approximately 2 hr. The output of a continuous mercerizing machine is usually 25 tons per day.

(2) The treatment of cotton fabrics or other cellulose fibrous materials with a concentrated aqueous solution of NaOH (usually at 15°-18°C) to add luster and increase dyeing capacity and strength. The process takes place on a machine that dips the material in the NaOH solution and then presses and washes it. Such machines have a device to stretch the fabrics, which shrink after treatment. Fabrics are mercerized in the unbleached state or after boiling or bleaching.