Cuprammonium

Cellulose dissolves in strong mineral acids, in NaOH and in cuprammonium solution. It forms a triacetate (tri-ethanoate), a trinitrate... 

Schweizer s reagent The dark blue solution obtained by dissolving Cu(OH)2 in concentrated ammonia solution. Used as a solvent for cellulose, the cellulose is precipitated on acidification. Used in the cuprammonium process for the manufacture of rayon. 

Butadiene Separation. Solvent extraction is used in the separation of butadiene (qv) [106-99-0] from other C-4 hydrocarbons in the manufacture of synthetic mbber. The butadiene is produced by catalytic dehydrogenation of butylene and the Hquid product is then extracted using an aqueous cuprammonium acetate solution with which the butadiene reacts to form a complex. Butadiene is then recovered by stripping from the extract. Distillation is a competing process. 

The second ceUulosic fiber process to be commercialized was invented by L. H. Despeissis (4) in 1890 and involved the direct dissolution of cotton fiber in ammoniacal copper oxide Uquor. This solvent had been developed by M. E. Schweizer in 1857 (5). The cuprammonium solution of ceUulose was spun into water, with dilute sulfuric acid being used to neutralize the ammonia and precipitate the ceUulose fibers. H. Pauly and co-workers (6) improved on the Despeissis patent, and a German company, Vereinigte Glanstoff Eabriken, was formed to exploit the technology. In 1901, Dr. Thiele at J. P. Bemberg developed an improved stretch-spinning system, the descendants of which survive today. 

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. 

The dark blue solution containing 5—10% of cellulose with a DP of 1000—2000 is filtered through a series of plate-and-frame filter presses using fine mesh metal screens to remove any particles that might block the spinneret holes. It is then deaerated under vacuum and stored ready for spinning. Unlike viscose dope, the cuprammonium cellulose [9050-09-3] solution is relatively stable. 

Asahi s innovations have done much to transform the cuprammonium process from an uneconomic competitor for viscose and synthetics into the fastest wet-spinning system in the world. They now cl aim it to be competitive both economically and environmentally with the viscose filament process. 

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. 

Of somewhat greater technical interest are the addition compounds and the cellulose esters and ethers. Of the apparent addition compounds the most important is alkali cellulose produced by steeping cellulose in caustic soda and considered to be of general form (CgHioOs), (NaOH) ) rather than a sodium alcoholate compound. Alkali cellulose is a particularly important starting point in the manufacture of cellulose ethers. The ability of aqueous cuprammonium hydroxide solutions to dissolve cellulose appears to be dependent on addition compound formation. 

Dissolution of the cellulose in cuprammonium solution followed by acid coagulation of extruded fibre ( cuprammonium rayon —no longer of commercial importance). In this case the acid converts the cuprammonium complex back into cellulose. 

Copper and compounds SPA Copper sulphate Copper pyrophosphate Cuprammonium compounds Electroplating Electrical and electronics Etching Pesticides... 

Metal salts in alkaline solution Cuprammonium complex Nickel and cobalt ammonia complex Cyanides (q.v.) Copper pyrophosphates Plumbites Zincates... 

Glam-silber, n. polished silver (Min.) silver glance, argentite. -stahl, m. polished steel, -stkrke, /. gloss starch, -stoff, m. trade name of a cuprammonium rayon glazed or glossy fabric. 

Kupferoxyd, n. cupric oxide, copper(II) oxide, -ammoniak, n. ammoniacal copper oxide, cu-prammonium. -ammoniakkunstseide, -am-moniakzellulose, /. cuprammonium rayon, -hydrat, n. cupric hydroxide, copper(II) hydroxide. -salz, n. cupric salt, copper(II) salt. 

The presence of free sulphuric acid in rayon-spinning baths limits application of the austenitic steels, but they are used for acetylation of cellulose in the acetate process. They are also used for dissolving and spinning solutions in the cuprammonium processes. 

Copper sulphate Copper pyrophosphate Cuprammonium compounds... 

Chitosan features far more than chitin in research into applications. This is largely due to their difference in solubility characteristics, chitosan being more amenable to practical manipulation. Chitin is in fact rather more intractable than cellulose, since it is insoluble in those solvents, such as cuprammonium hydroxide, that are commonly used to dissolve cellulose. Chitin is soluble in hot concentrated solutions of certain inorganic salts capable of... 

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