Viscose

As viscose fibers ( cellulose fibers ) can be referred to, which today are based on cellulose, predominantly in the form of wood pulp by means of the viscose process, the most widely used wet spinning process, spun industrially. The pulp is converted by treatment with sodium hydroxide solution, whereby alkali cellulose is formed, and their subsequent reaction with carbon disulfide to form cellulose xanthate in successive process stages. By a further addition of sodium hydroxide, the viscose dope is generated is pumped through the holes of showerhead spinneret into the spinning bath. There he produced by coagulation per spinneret hole a viscose filament. By stretching and further processing steps and the merging of the individual filaments producing viscose arise or by additional cutting Viskosespinnfasern. Previously, viscose filament yarns were described as rayon or artificial silk, the staple fibers as rayon staple.

The chemical composition of the viscose ( basic component of cellulose ) is similar to the case of cotton.

Use

The use of viscose fibers is similar because of the common base cellulose and thus the connected clothing physiological characteristics of cotton fibers. However, because of the much greater possibility of variation in the fiber geometry (length, crimp, fineness, cross-sectional shape ) surpasses it in many applications, the properties of cotton fibers. Significant for the processing and thus for use is that of viscose staple fibers not only stand as cotton available, but filaments ( continuous fibers ) can be produced.

• Examples for use in apparel and home textiles sector are: Yarns made ​​from 100 % viscose staple fibers or mixed with cotton, wool, polyester or polyacrylonitrile on fabrics for outerwear, such as dresses, blouses, shirts, suits and coats,
• Because of their high absorbency also to substances for undergarment,
• Processed into decorative and upholstery fabrics and fabrics for bed linen and table linen.

• Association and compression materials such as gauze of plain weave Visksosefasergarn fabrics, viscose - cotton wool pleat, Viskosefaservliesstoffe for compression and Saugkissenfertigung, Viskosefaservliesstoffe as Sekretverteilschicht ( acquisition layer ) in multi-layer absorbent dressings, gauze bandages from Viskosfasergarn fabrics for bandages and circular knitted, transverse and longitudinal elastic jersey Tubular bandages from Viskosefasergarnen
• Hospital textiles such as multi-layer mattress pads with Viskosfaser / cotton fiber knitted terry towels as absorbent layer, binder solidified Viskosfaservliesstoffe as absorbent layer in multi-layer surgical drapes, Hydroentangled Polyester-/Viskosefaser-Vliesstoffe as surgical gowns
• Hygiene and body care products such as Dry and wet wipes from different bonded nonwovens (increasing by solidification with water jets, as spunlace nonwovens called ) on the basis of 100 % viscose or blends with polyester fibers or defibrillated pulp
• Absorbent cores of tampons which are produced from strips of needle or hydroentangled nonwovens, where 100% modified cross-section ( multilobal ) viscose can be used to increase the suction force
• Cotton swab

• From generated for a special spinning process solemnity - Viskosefilamenten ( Viscosecord ) made ​​as Radialkarkassen in tire cord fabric, hoses, such as for fuel and lubricating oils used in automobiles, fabrics for conveyor belts and cords and strings
• High-strength viscose filaments, but also as a short cut fibers for reinforcement fibers in PP compounds, which are processed by injection molding, extrusion or extrusion (eg for components in the automotive interior )
• Binder solidified Viskosfaservliesstoffe as filter materials in the liquid filtration ( waste water, cooling lubricants, milk)
• Tea bags and paper for notes

Production ( viscose )

As starting material for viscose is cellulose, which in turn comes from wood of beech, spruce, eucalyptus, pine, bamboo or similar. The pulp quality used differs from the paper pulp quality by the fact that the chain length of the cellulose molecules shorter and the purity is higher. The pulp for viscose production contains less residual lignin and hemicelluloses or less pentosans. It has a better reactivity with sodium hydroxide and carbon disulfide and a better solubility in aqueous sodium hydroxide after Xanthogenierungsreaktion.

For the preparation of a dope for spinning of viscose fibers in the classic viscose process, the cellulose is first treated with sodium hydroxide solution. In the aqueous sodium hydroxide solution swells the cellulose ( mercerization ). This allowed to carbon disulfide (CS2 ) act. This creates Natriumxanthogenat ( xanthate ). The orange-yellow xanthate forms in aqueous, dilute sodium hydroxide solution, a viscous solution. Hence the name of the viscose solution comes in this stage of the reaction. This mass with a consistency similar to that of warm honey, the viscose dope dar. After two or three times filtration, after-ripening and vent then has this dope suitable viscosity for reprecipitation of cellulose as viscose. This alkaline solution is forced through dies to in sulfuric acid salt solutions.

For the viscose fibers in the traditional production process, a sulfuric acid bath is used, which is almost to the saturation limit includes in addition a small amount of sodium sulfate and zinc sulfate to retard cellulose precipitation reaction. Is pressed by the viscose spinning gear pump through the spinneret. The typical diameter of a single hole the hole of the spinneret is about 50 microns. By neutralization of the sulfuric acid forms from the Natriumxanthogenat both sodium sulfate and the volatile cellulose xanthogenic, which in turn immediately decays to cellulose and carbon disulfide. By-products in this case are small amounts of carbon dioxide and malodorous hydrogen sulfide, which must be removed in an elaborate gas scrubbing. Alternatively, the bio-trickling filter process ( Lenzing AG) can be applied, a simple and reliable biological cleaning technology.

The water and sodium sulfate are removed in the recovery for the reprocessing of the spinning bath from the spent bath. Sodium sulfate is thus a by-product in the traditional viscose process and is mostly sold to the detergent industry. Liberated in the spinning process, carbon disulfide is the one extracted from the spinning lines and either directly recovered by adsorption on activated carbon or burnt for the purpose of production of sulfuric acid. Secondly, the CS2 is recovered directly due to its low boiling point of 46 ° C by expulsion from the freshly spun fibers by means of vapor and subsequent condensation of the vapors and returned to the process. This expulsion CS2 is usually after the fresh tow was previously stretched to increase the strength and yet cut to the desired fiber length. Since the carbon disulphide is a relatively expensive raw material, the complete recovery is sought. On the other hand, carbon disulfide is difficult to handle safely due to its extremely low ignition temperature of 102 ° C in plants.

Packaging

For one, cotton -like appearance, the viscose fibers are washed and bleached in a post-treatment process. Chlorine - free bleaching and the use of chlorine-free pulp in Europe is already the rule. To give the viscose fibers for further processing favorable sliding characteristics are prior to drying or finishing agents - soap-like substances - applied to the surface of the fibers in the parts per thousand range.

The viscose fibers ( staple fiber ) come in bales with a weight of about 250 to 350 kilograms and a recapitulation (commercial residual moisture) of about eleven percent of the market. Viscose are wound with coils weights of about 1.5 to 6.0 kg. This usually titer 40-660 dtex are spun.

From viscose can be fundamentally different products of daily life, such as staple fibers, filament fibers, packaging films and casings with and without make nonwoven reinforcement.

Related Products

Modal

A similar product such as viscose are modal. They are also 100 percent of cellulose such as viscose and are made ​​from virgin pulp, the raw material has been stripped and then to separate the lignin into matchstick- sized pieces is crushed eucalyptus, pine or beech wood. Starting material for the extraction of modal fibers, however, is always only beech wood. By a somewhat different process is achieved for the modal higher fiber strength and improved fiber properties. Modal fibers has a higher moisture absorption and dries quickly.

Tencel and lyocell

Also in the class of cellulosic fibers are the Tencel and lyocell fibers to classify. These are made with the same basic process. After buying the brand Tencel by the Austrian Lenzing AG ( lyocell) the brand name Tencel was acquired by Lenzing, because these have a higher level of awareness than the lyocell brand. The Tencel-/Lyocellfasern the pulp is dissolved directly and unchanged from the xanthate by the non-toxic solvent NMO (N -methylmorpholine- N-oxide) without prior reaction with sodium hydroxide solution and derivatization. The spinning of the Tencel-/Lyocellfasern carried out in a dilute aqueous NMO bath, wherein the solubility of the cellulose exceeded, thereby forming a thread.

Environmental and wear properties

Viscose, modal and Tencel-/Lyocellfasern are man-made fibers from natural material cellulose. Due to their water absorption capacity ( buffering, forwarding) tailored clothing is it comfortable to wear. Risks and skin irritation therefore arise in respect only because of the coloring or the equipment of the fiber. The raw material for these fibers is cellulose, which is manufactured from wood by removing the binder materials ( lignin) directly and without chemical transformation. The conversion of the cellulose to cellulose xanthogenate classic Viskosefaserprozess serves only to obtain a solubility and finally ends after spinning back in the starting material cellulose.

Compared to real synthetic fibers, the raw materials are made from petroleum or natural gas, there are viscose fibers from the renewable raw material wood. According to the manufacturer, the fibers are biodegradable. The energy and water consumption during the production and processing is substantially less than that of cotton. Moreover, accounts for the most commonly used herbicides in the cultivation of cotton and pesticides, which are reflected in the environment except sometimes in garments.

One problem is the arising during the manufacturing process materials that are partially unhealthy and harmful to the environment: hydrogen sulfide ( H2S) and carbon disulfide (CS2 ) are nerve poisons and deadly in certain amounts, carbon disulfide is also extremely flammable.

Manufacturer

Since 1908 /09 Hugo Kuttner produced in Pirna near Dresden rayon, first the Chardonnet process, and from 1910 by the viscose patent. 1911 joined them, which was founded in 1899 by Max Fremery and Johann Urban United Glanzstoffabriken AG with headquarters in Elberfeld ( today Wuppertal ) that their had the year before the " Prince Guido Donnersmarckschen rayon and Acetatwerke " in Sydowsaue near Stettin and then viscose patents had taken in order to improve it further.

The World's Largest viscose producer is today India's Grasim Industries Ltd.. , Meanwhile, the largest viscose production lines today daily from the Indonesian South Pacific Viscose in Purwakarta (Indonesia) with a daily capacity of 150 tons and by the Austrian company Lenzing AG with nearly 170 tons be operated. The latter can also claim to be, the world's largest producer of cellulosic fibers at all, so taken together, viscose, Modal and Tencel lyocell fibers or to be.

Other important European companies in the viscose industry are eg the German Kelheim Fibres GmbH as the world's largest viscose specialty fiber manufacturer that also German Cordenka GmbH, headquartered in the Industrial Center Upper Castle as the world 's largest manufacturer of high-strength viscose fibers for production and a. carcasses and tire cord as well as the German Enka GmbH in Wuppertal as Europe's largest manufacturer of textile viscose filament yarns. Another big producer of viscose filament is the company Glanzstoff Industries, based in St. Pölten, Austria and the production site Lovosice in the Czech Republic.

A merger of the manufacturer ( "tampon monopoly " ) is evaluated by the Bundeskartellamt critical.

Literature on the history of the viscose

• Lars Bluma, " L' replacement is not a substitute " - The creation of trust through technology mediation on the example of the German synthetic wool. In: Lars Bluma, Karl Pichol, Wolfhard Weber ( ed.): Technology transfer and technology popularization. Historical and educational perspectives. Waxmann, Münster 2004, ISBN 3-8309-1361-3, pp. 121-142.
• Lars Bluma: Fabric History: viscose, fashion and modernity 1920-1945. In: Elizabeth Hack game Mikosch, Birgitt Borkopp - Restle ( Eds.): Smart connections. Volume 1: interactions between technology, textile design and fashion. ( online at: smart - verbindungen.de ), accessed on December 29, 2011.
• Hans Dominik: Vistra, the white gold in Germany. The story of a world-shattering invention. Koehler & Amelang, Leipzig 1936, DNB 572,897,405th
• Kurt Götze: rayon and spun rayon by the viscose process. Springer, Berlin 1940, DNB 573,503,486th
• Jonas Schemer: Between state and market. The German semi-synthetic chemical fiber industry in the 1930s. In: Quarterly magazine for social and economic history. 89, No. 4, 2002, pp. 427-448.
• Kurt Ramsthaler: The chemical worker in Cell wool and artificial silk factory ( viscose ): An auxiliary book for chemical worker, foremen and shift supervisors. Volume 2: From the dope to the finished product. Conradin -Verlag, Berlin 1941, DNB 453,910,629th