There are four types of spinning: wet, dry, melt, and gel spinning.
|Wet Spinning (Rayon)|
Dia of holes, rate of solution feeding and rate of holes per spinneret may be 100000 numbers per squa4e inch diameter and space of holes in the spinneret could be varied.
Typical Wet Spun Fibers:
- Slow(70-150 yds/min)
- Washing to remove impurities
- Solvent and chemical recovery
- Large tows can be handled
The number of holes, dia of holes and shape of holes varies according to requirements of a spinneret. The fineness of the filament is determined partly by the diameter of the holes but primarily by the relation between the rate at which solution is forced through the spinneret and rate at which the yarn is wind up. When the fibre spinning solution emerging from spinneret meet the worm air, volatile solvent evaporates leaving the filaments, hence coagulation takes place and becomes dried before leaving the chamber.
Typical Dry Spun Fibers:
- Acetate (acetone solvent)
- Triacetate (methylene chloride)
- Spandex(some) (dimethyl formamide)
- Flammable solvent hazards
- Solvent recovery
- Slow(?) (200-400 yds/min)
- Yarn does not require purification
The melt solidifies immediately it issues from the jets and so form filaments passes through a cooling chamber in which cold air current swept across the filaments. The spinning speed is approximately 1200 meters per minute.
Melt spinning has two big advantages over dry spinning. It avoids the need for a solvent recovery plant and loss of solvent during recover. The high fibre spinning speeds that are possible here.
Typical Melt Spun Fibers:
- Seperate drawing step (unless spin draw)
- High speed (275 to 1500 yds/min)(4000 yds/min spin draw)
- No solvents
- No purification problems