Cuprammonium process

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. 

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. 

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. 

Bemberg An alternative name for the Cuprammonium process for making artificial silk, named after J. P. Bemberg who commercialized the process in the early 1900s in several countries. 

An alternate procedure used in a few specialty applications is the cuprammonium process. This involves stabilization of cellulose in an ammonia solution of cupric oxide. Solubilization occurs by complex formation of cupric ion with ammonia and the hydroxyl groups of cellulose. Regeneration of cellulose, after formation of the desired products, is accomplished by treatment with acid. The main application of the cuprammonium process is for the synthesis of films and hollow fibers for use in artificial kidney dialysis machines. The cuprammonium process yields products with superior permeability and biocompatibility properties compared to the xanthation process. Less than 1% of all regenerated cellulose is produced by the cuprammonium process. 

Today rayon is made by either the viscose or the cuprammonium process. The latter process is based on Schweitzer s discovery in 1857 that it is possible to dissolve cellulose in cuprammonium hydroxide, the soln being due to the formation of a Cu cellulose complex. The mfg procedure involves processing the cuprammonium soln by filtration and deaeration prior to pumping it thru holes in a spinneret into si alkaline w which coagulates the Cu-cellulose soln into rayon filaments. The filaments are then stretched to the desired fineness (Ref 11). The viscose process is the most widely used because of its great versatility and low cost operation. 

Establishments primarily engaged in manufacturing cellulosic fibers (including cellulose acetate and regenerated cellulose such as rayon by the viscose or cuprammonium process) in the form of monofilament, yarn, staple, or tow suitable for further manufacturing on spindles, looms, knitting machines, or other textile processing equipment. 

In 1937, Schweizer [91] discovered that cellulosic fibers such as cotton and hemp readily dissolve in copper hydroxide and ammonium hydroxide solutions. His system is recognized as the Schweizer reagent. The Bemberg Rayon Industry later utilized this solvent for the industrial production of cuprammonium fibers (or cuprammonium rayon) and developed the Bemberg process or cuprammonium process [92]. Kamide and Nishiyama [93] have recently published an excellent review on the history and science of cuprammonium technology. 

In a typical cuprammonium process, a freshly made aqueous solution of copper hydroxide (formed from cupper sulfate and caustic soda) and ammonium hydroxide is used as a direct solvent for the dissolution of activated cellulose pulp. The ammonia concentration is usually between 124 and 250 g/1 and the copper concentration must be greater than 25 g/1... 

The main disadvantage of the cuprammonium process is the toxicity of copper sulfate. Hence, it must be fully recovered from the process as a result large-scale production is limited. In 1990, annual production of cuprammonium yarns was close to 30,000 t [74,94,95]. Although, the cuprammonium process is used for making fibers, other products can also be produced. For example Akzo Nobel is using the cuprammonium process to make dialysis membranes (Cuprophane). 

Kamide, K. and Nishiyama, K., Cuprammonium Processes, Regenerated Cellulose Fibres, Wood-ings, C., Ed., Woodhead Publishing, Cambridge, U.K., 2001. 

Schwoizer s reagont A solution made by dissoiving copper( 11) hydroxide in concentrated ammonia soiution. It has a deep blue colour and is used as a solvent for cellulose in the cuprammonium process for making rayon. When the cellulose solution is forced through spinnarets into an acid bath, fibres of ceiiuiose are reformed. 

In the Cuoxam or Cuprammonium process, linters or high-quality wood pulp is dissolved in an ammoniacal copper (II) oxide solution. 

Cuprammonium Process. In the cuprammonium (cuoxam) process, linters or high-quality wood pulp is dissolved in [Cu(NH3)4] [OH] " (cuoxam). The method varies slightly according to whether copper silk (Bemberg silk) or cell glass (Cellophane ) is required. 

Regenerated cellulose films and hollow fibres used in haemodialysers have been prepared by a method known as the cuprammonium process. Cellulose is dissolved in a solution of ammonia and cupric oxide. The complex cupric salts are water-soluble and cellulose is regenerated by treatment with acid. Cuprophan is prepared by this process. 

Rayon manufactured by different processes varies both chemically and physically. Most rayon is made by the viscose process, where the cellulose is treated with caustic soda and then with carbon disulfide to form cellulose xanthate, which is dissolved in a weak caustic solution to form the viscose. With the cuprammonium process, the cellulose is digested in an ammonia solution of copper sulfate and the solution is forced through the spinnerets into dilute acid for hardening. 

L.H. Despaissis patented the cuprammonium process for the production of regenerated cellulose (rayon) from a... 

On account of this, and with the great strides being made in chemistry, research was begun to find ways of making artificial yams and fibers. The first successful artificial yam was the Chardonnet artificial silk, a cel-lulosic fiber regenerated from spun nitrocellulose. Further developments lead to the cuprammonium process and then to the viscose process for the production of another cellulosic, rayon [23]. This latter viscose was fully commercialized by Courtaulds in 1904, although it was not widely used in mbber reinforcement until the 1920s, with the development of the balloon t3 e [24]. 

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