The Manufacturing Process

While there are numerous variations in the production procedure that make use of the adaptability of the fiber, the following is a description of the treatment that is utilized in making regular or viscose rayon.

No matter whether wood pulp or cotton linters are utilized, the fundamental raw material for making rayon should be processed in order to extract and purify the cellulose The resulting sheets of white, purified cellulose are then treated to form regenerated cellulose filaments In turn, these filaments are spun into yarns and ultimately made into the wanted fabric.

Processing purified cellulose

• Sheets of purified cellulose are soaked in caustic soda, which produces sheets of alkali cellulose. These sheets are dried, shredded into crumbs, and after that aged in metal containers for 2 to 3 days. The temperature level and humidity in the metal containers are thoroughly managed.
• After aging, the crumbs are integrated and churned with liquid carbon disulfide, which turns the mix into orange-colored crumbs called sodium cellulose xanthate. The cellulose xanthate is bathed in caustic soda, leading to a viscose solution that looks and feels similar to honey. Any dyes or delusterants in the design are then added. The syrupy solution is filtered for foreign substances and kept in barrels to age for 4 to 5 days.

Producing filaments

• The viscose solution is next made into strings of fibers. This is done by forcing the liquid through a spinneret, which works like a shower-head, into an acid bath. If staple fiber is to be produced, a big spinneret with big holes is utilized. If filament fiber is being produced, then a spinneret with smaller-sized holes is utilized. In the acid bath, the acid coagulates and solidifies the filaments, now called regenerated cellulose filaments.

Spinning

• After being bathed in acid, the filaments are ready to be spun into yarn. Depending upon the kind of yarn wanted, numerous spinning techniques can be used, such as Pot Spinning, Spool Spindle Spinning, and Constant Spinning. In Pot Spinning, the filaments are first extended under regulated stress onto a series of offsetting rollers called godet wheels. This extending decreases the size of the filaments and makes them more consistent in size, and it also offers the filaments more strength. The filaments are then taken into a quickly spinning cylinder called a Topham Box, resulting in a cake-like string that adheres to the sides of the Topham Box. The strings are then cleaned, bleached, rinsed, dried, and wound on cones or spools. Spool Spinning is extremely similar to Pot Spinning. The filaments travel through rollers and then are wound on spindles, where they are cleaned, bleached, rinsed, dried, and wound once again on spools or cones. In Continuous Spinning, the filaments are cleaned, bleached, dried, twisted, and wound at the same time that they are extended over godet wheels.

• Once the fibers are adequately treated, they are ready for post-treatment chemicals and the different weaving procedures essential to produce the fabric. The resulting fabric can then be offered any of a variety of finishing treatments. These consist of calendaring, to control smoothness; fire resistance; pre-shrinking; water resistance; and wrinkle resistance.

High-Wet-Modulus Rayon Manufacture

The procedure for producing high-wet-modulus rayon has similarities with that utilized for making regular rayon, with a  couple of exceptions. First, in step 1 above, when the purified cellulose sheets are bathed in a caustic soda solution a weaker caustic soda is utilized when making HWM rayon. Second, neither the alkali crumbs (step 1 above) nor the viscose solution (step 2) is aged in the HWM  procedure. Third, when making HWM rayon, the filaments are stretched to a greater degree than when making regular rayon.