Rayon was the first fiber to be produced commercially. By the passage of time increasing number of new fibers came into existence. A generic name is the name of a family of fibers all having similar chemical composition. All man-made fiber spinning processes are based on three general steps.
1. Preparing a viscous solution or syrup dope.
2. Extruding this solution through spinneret to form a fiber.
3. Solidifying the fiber by coagulation, evaporation or cooling.
Spinning is done by three different methods in case of man-made fibers.
1. Wet Spinning:
Examples: Acrylic, Rayon, Spandex.
2. Dry Spinning:
Examples: Acetate, Acrylic, Mod-acrylic, spandex, triacetate, vinyon.
3. Melt Spinning:
Examples: Nylon, Olefin, Polyester, Saran.
By using different chemicals and manufacturing techniques, two basic types of rayon were developed. They were viscose rayon and cuprammonium rayon. Viscose rayon can have more names like standard viscose, regular viscose and high wet modulus rayon,depending on the changes made to get different qualities. Schweitzer in 1857 dissolved in an alkaline copper solution. In 1890, Despeisse developed a method to make a filament. The method was frequently modified until now it is capable of producing the finest diameter of any of the rayons.
1. Cotton linters afford the greatest purity and are the preferred source cellulose. These fibers are cleansed by cooking in a mild caustic alkali and bleached with chlorine.
2. The purified alpha-cellulose is washed, dried and treated with basic copper sulphate and ammonia.
3. The viscose solution is forced through spinnerets into water, which removes much of the copper and ammonia.
4. The filaments are passed through a mild sulfuric acid bath to coagulate them and to remove the copper.
5. The skeins are washed and rinsed.
6. The yarns are sorted according to denier.