Acetate and triacetate
The term acetate fibres is used to describe fibres made from cellulose acetate. The difference between acetate and triacetate fibres lies in the number of the cellulose hydroxyl groups that are acetylated. For acetate fibres the number lies between 75% and 92%, for triacetate fibres it is more than 92%.
Wood cellulose is swollen by acetic acid and then converted to cellulose acetate using acetic anhydride and it is then dissolved in acetone. The resulting viscous solution is pumped through spinnerets into warm air to form filaments. The acetone evaporates and is recovered. The filaments are then wound up as filament yarns or collected as a tow.
Properties and End-Uses
These fibres are different from viscose in that they are thermoplastic. They are generally dyed using disperse dyes, absorb little water and can be textured. Although the dry strength of the two types are similar, triacetate has a higher wet strength. It also has a high melting point, 300 degrees C, compared with 250 degrees C for diacetate. Main end-uses for the filament yarns are linings and dresswear. There is very little staple fibre made from these fibres but acetate tow is the major product used for cigarette filters.