lyocell

Lyocell is a generic name for a class of cellulose fibers produced by the lyocell process. It is a type of rayon made from dissolving grade cellulose, usually derived from wood pulp. The process uses N-methylmorpholine N-oxide (NMMO) as a solvent to dissolve cellulose, forming a viscous solution that can be spun into fibers. The technology was developed in the 1970s and 1980s, and is marketed commercially under brand names such as TENCEL by Lenzing AG.

In production, dissolving pulp is treated with NMMO to form a homogeneous solution. The solution is extruded through spinnerets into a non-solvent coagulation bath, yielding continuous filaments or staple fibers. The NMMO solvent is recovered in a nearly closed loop and is recycled; typical recovery rates exceed 99%, reducing emissions and solvent loss. The process is less chemically intensive than viscose rayon and avoids carbon disulfide.

Properties and performance: Lyocell fibers are strong, especially when wet; they are soft with a smooth, cool feel, and have good moisture absorption and breathability. They drape well and can be produced in various deniers for apparel and home textiles. The fibers take up dyes well and produce fabrics with a silky appearance and good translucency. They can be produced in filament or staple form and blended with other fibers.

Environmental aspects: The lyocell process is generally considered more sustainable than traditional viscose rayon because of the closed-loop solvent system and relatively low toxicity. However, the environmental impact depends on feedstock sourcing, energy use, and chemical handling. Lyocell fibers are biodegradable and compostable under appropriate conditions.