Viscose filament yam

Since the early 1980s, the viscose-based staple fibers have, like the cuprammonium and viscose filament yams in the 1970s, ceased to be commodities. They have been repositioned from the low cost textile fibers that were used in a myriad of appUcations regardless of suitabUity, to premium priced fashion fibers dehvering comfort, texture, and attractive colors in ways hard to achieve with other synthetics. They are stiU widely used in blends with polyester and cotton to add value, where in the 1980s they would have been added to reduce costs. 

In plants which produce viscose fibre (stable fibre), viscose filament yam (rayon) and viscose film (cellophane), large volumes of exhaust air contaminated with carbon disulfide... 

In the production of viscose filament yam a Supersorbon -system combined with a NaOH-scmbber system (Figure 22.1.21) has been in use since 1997. A very high standard of safety engineering is implemented in the treatment system owing to the flammability of the CS2 and the toxic nature of the constituents to be removed from the exhaust air. 

Table 11.2 Emission and consumption data for viscose filament yam production [37, CIRFS,2004]...

Exhaust air from viscose filament yam plant. Design data ... 

From 1910 onward waste filament yam had been chopped into short lengths suitable for use on the machinery designed to process cotton and wool staples into spun yams. In the 1930s new plants were built specifically to supply the staple fiber markets. During World War II the production of staple matched that of filament, and by 1950, staple viscose was the most important product. The new spun-yam oudets spawned a series of viscose developments aimed at matching the characteristics of wool and cotton more closely. Viscose rayon was, after all, silk-like. Compared with wool it lacked bulk, residence, and abrasion resistance. Compared to cotton, it was weaker, tended to shrink and crease more easily, and had a rather lean, limp hand. 

Approximately 2.5 million t of viscose process regenerated ceUulose fibers were produced in 1990 (Table 1). Measured by production capacity in 1990, the leading producers of filament yams in 1990 were the Soviet Union state-owned factories (255,000 t capacity) and Akzo Fibres in Europe (100,000 t). The leading producers of staple fiber and tow were Courtaulds with 180,000 t capacity spUt between the UK and North America Formosa Chemicals and Fibres Co. with 150,000 t in Taiwan Tenzing with 125,000 t in Austria, and a 40% stake in South Pacific Viscose s 37,000 t Indonesian plant and Grasim Industries in India (125,000 t). BASF s U.S. capacity of 50,000 t was acquired by Tenzing in 1992. 

Asahi Chemical Industries (ACl, Japan) are now the leading producers of cuprammonium rayon. In 1990 they made 28,000 t/yr of filament and spunbond nonwoven from cotton ceUulose (65). Their continuing success with a process which has suffered intense competition from the cheaper viscose and synthetic fibers owes much to their developments of high speed spinning technology and of efficient copper recovery systems. Bemberg SpA in Italy, the only other producer of cuprammonium textile fibers, was making about 2000 t of filament yam in 1990. 

As for viscose fibres, these are mostly produced as staple fibres for textile and nonwoven applications. In 2011, world production was 3.246 million tons [49] while filament yam for textile and technical applications reached 332 000 tons in 2011 [49] with a share of technical yarns of 56 000 tons. Technical viscose fibres, also called rayon or viscose rayon, are used mainly as carcass reinforcing fibres in fast-running and run-flat tyres. Lyocell fibres are produced only as staple and virtually exclusively by Lenzing AG, Austria, with a production capacity of 140 000 tons in 2011 [50]. 

Approximately 3 million metric tons of regenerated cellulose fibers production capacity existed in 2000 (Table 2). The leading producers of filament yams were the Chinese state-owned factories (118,000-t capacity), Acordis in Europe (69,0001), and the Russian plants (with 44,000 t). The leading producers of staple fiber and tow were the Chinese with 480,0001, the Birla Group (India) with 408,0001, Lenz-ing (Austria, U.S.A., and Indonesia) with 315,000 t and Acordis with 170,000-t capacity split between the United Kingdom and North America, Formosa Chemicals and Fibers Co. with 162,000 t (in Taiwan). Acordis was formed in 1998 from the fiber businesses of Courtaulds and Akzo-Nobel following the takeover of Cour-taulds by Akzo, who later sold Acordis to a consortium of CVC Partners and Acordis management. (Note since these statistics were compiled, 100,000 ton of Acordis s viscose staple fiber capacity has closed.)... 

In recent history in Europe, textile viscose filament end-uses are receiving increased competition (resulting in phasing out of capacity) by cheaper competitive yams based on polyester and polyamide, whereas viscose staple fibre and viscose tyre cord keep a strong position. 

At this point, a distinction has to be made between staple fibres and filament yam. Staple fibres are cut into short pieces after the spinning bath. These short fibres, which are each approximately 4 cm long, are spun into textile yams or processed into non-woven products later on. In contrast, filament yams are spun into endless fibres which can be used immediately. Viscose products for textile usage with certain improved product characteristics are called modal fibres . 

Emission and consumption data for viscose fibre production processes were submitted by CIRFS [37, CIRFS, 2004] and a Member State [30, UBA, 2004]. Table 11.1 summarises data for staple fibres. Table 11.2 for filament yams. 

In another laboratory at Kew, C. H. Steam and C. E. Topham, who had worked for Sir Joseph Swan on lamp filaments, developed the continuous filament spinning process (8) and the machinery needed to wash and coUect (9,10) the yams. A fibermaking method was outlined in 1898, and the Viscose Spinning Syndicate was formed to develop the concept into a commercial proposition. 

Tire Ya.rns, A method to iacrease the strength of viscose yam from the 0.2 N /tex (2.2 gf/den) standard to levels needed ia tires was first patented by Courtaulds ia 1935 (18). By raising the ziac concentration ia the spia bath to 4% the thread could be stretched more by immersing it ia a hot dilute acid bath duting extension. Filament strengths iacreased to about 0.3 N/tex (3.3 gf/den), and the cross section became rounder, with a thicker skin than regular viscose. Pairs of these yams were capable of beiag twisted iato tire cords which outperformed traditional cotton cords. 

The viscose obtained from Cross and Bevan was so successful for production of lamp filaments that Steam asked Topham to try to spin it for use in textiles. The first experiments failed dismally. After several years of painstaking work, Topham made several discoveries essential to the spinning of yam from viscose aging (ripening) of the solution, filtration to remove particles, multiple-hole platinum spinnerettes, and a circular, centrifugally operated yarn collecting device that twisted the yam and packaged it in convenient cake form [117]. The Topham box, as it is still called, or variations of it are still on many of the continuous-filament rayon machines today. 

---