Solvent spinning processes

Acrylics. The DuPont Company introduced the first commercial acrylic fiber, Orion, in 1950. Acrylics are made from the polymerization of acrylonitrile and other co-monomers to allow dyeability and to open the internal structure. The fibers are produced by either solventspinning (Orion), or wet-spinning (Acrilan). In the solvent-spinning process, the polymer is... 

Lyocell is the first in a new generation of cellulosic fibres made by a solvent spinning process. A major driving force to its development was the demand for a process that was environmentally responsible and utilised renewable resources as their raw materials. The first samples were produced in 1984 and commercial production started in 1988. A wide range of attractive textile fabrics can be made from lyocell that are comfortable to wear and have good physical performance. This physical performance combined with its absorbency also make lyocell ideal for nonwoven fabrics and papers. 

Fiber cross sections are also deterrnined by the coagulation conditions or, in the case of dry spinning, by the solvent evaporation process. The skin that forms early in the solvent removal process may remain intact as the interior of the filament deflates from solvent removal. Wet spun fibers from organic solvents are often bean shaped, while those from inorganic solvent systems are often round. Dry spun fibers, such as Du Font s Odon, are... 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

One report (13) describes the procedure for spinning dry asymmetric ceUulose acetate fiber with a bore skin. Such fibers are spun in a modified dry-spinning process in which a volatile Uquid (methyl formate) is used as the ceUulose acetate solvent. The bore coagulating Uquid is isopropyl alcohol, which is subsequentiy removed. The advantages of these dry fibers over most ceUulose acetate membranes are that they can be stored dry, they are wet-dry reversible, they can be sterilized and packed dry, and they are ready for use without removal of preservatives. 

These solvents include tetrahydrofuran (THF), 1,4-dioxane, chloroform, dichioromethane, and chloroben2ene. The relatively broad solubiHty characteristics of PSF have been key in the development of solution-based hoUow-fiber spinning processes in the manufacture of polysulfone asymmetric membranes (see Hollow-fibermembranes). The solvent Hst for PES and PPSF is short because of the propensity of these polymers to undergo solvent-induced crysta11i2ation in many solvents. When the PES stmcture contains a small proportion of a second bisphenol comonomer, as in the case of RADEL A (Amoco Corp.) polyethersulfone, solution stabiHtyis much improved over that of PES homopolymer. 

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

The use of a wet-spinning process with inorganic solvents has also been attempted. Although the details of this process are proprietary, it is clear that these inorganic wet-spun PAN fibers make higher quality carbon fiber precursors than those produeed with traditional organic solvents [5]. 

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