Hydroxides cuprammonium

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. 

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... 

In 1886, Brown11 discovered an organism which formed extremely tough membranes when cultivated m suitable nutrient solutions containing carbohydrates such as D-fructose, D-mannitol or D-glucose ethanol, sucrose or starch did not support membrane formation by this organism which Brown called Bacterium xylinum ) (Acetobacter xylinum). The membranes were readily soluble in cuprammonium hydroxide solution and yielded a dextrorotatory sugar upon acid hydrolysis. These properties and the results of combustion analysis led him to believe that the membrane was cellulose. 

Cuprammonium hydroxide Cu(NH3)41(OH)2 Cuoxam Good solvating properties, extensive oxidative degradation1), rather unstable, clear, coloured (blue)... 

Cellulose is insol in w, ale, eth all known simple org solvs. The best solv for it is cuprammonium hydroxide, [Cu(NH3)4(OH)2], also called Schweitzer s Reagent. It is also sol in a coned soln of Ca thiocyanate alone or in combination with formaldehyde. Other solvs gelatinizers for cellulose include zinc chloride (in 40% soln on heating), basic beryllium perchlorate, 84% phosphoric acid, selenic acid, arsenic acid, sulfurous acid, 66% HBr, 70-75% HF, coned HI, chloral with pyridine, chloral hydrate in H2S04, and inorg salts(such as NaCl) in coned solns at high temps. Coned solns of NaOH at ca -10° only partially dissolve cellulose while the remainder is swelled "mercerized . 

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. 

Recent studies on complexing of w c-diols with borate and with cuprammonium hydroxide have also suggested that there is little correlation between 0—0 distance and complex formation H. Kwart and G. C. Gatos, J. Am. Chem. Soc., 80, 881 (1958). 

Among the most ancient solvents for cellulose we find cuprammonium hydroxide and cupriethylenediamine, but only the former was used industrially to give the CUPRO fibre. 

Using the sedimentation velocity procedure, Stamm found the average degree of polymerization of purified cotton linters dispersed in cuprammonium hydroxide solution to be 346. It was subsequently shown by Svedberg, however, that reliable values for the diffusion constant could not.be obtained in the ultracentrifuge and consequently the results of Stamm are probably in error. 

The need for greater accuracy in determining the intrinsic viscosity, [ij], of cellulose dispersed in cuprammonium hydroxide solution led... 

Among the best-known nonderivatizing solvent systems is a combination between copper, alkali, and ammonia termed Schweizer s reagent. Solutions of cuprammonium hydroxide have been used for both analytical and industrial cellulose dissolution. Regenerated fibers with silk-like appearance and dialysis membrane have been (and partially continue to be) industrial products on the basis of cellulose dissolution in cuprammonium hydroxide. The success of this solvent is based on the ability of copper and ammonia to complex with the glycol functionality of cellulose as shown inO Fig. 11. Because of the potential side reactions (oxidation and crosslinking, Norman compound formation), alternatives to both ammonia as well as copper have been developed. Cuen and cadoxen are related formulations based on the use of ethylene diamine and cadmium, respectively. The various combinations of alkali, ammonia. 

Complexatlon principle of cellulose with derivatizing solvent molecules illustrated for the case of cuprammonium hydroxide. Solvent molecules replace the existing hydrogen bonds with solvating Cu-complexes. (After Burchardt et al. [47])... 

The third type of cellulose regenerate with commercial significance operates on the basis of cuprammonium hydroxide (Schweizer s reagent). The process had significance for fibers in the first half of the 20th century, but it started to decline in the 1960s due to insurmountable obstacles in the recovery of copper ions. The main producer of cuprammonium fibers... 

The spinning of cuprammonium hydroxide fibers involved solutions of 4-11% cellulose, 4-6% Cu, and 6-10% NH3. Solution viscosities were 200 Pa x s at 20 °C. 

Cellulose can be dissolved in cuprammonium hydroxide, generating cuproxam lignin. ... 

Properties Tenacity, 3-6 g/denier (dry), 4—8 g/de-nier (wet) elongation 3-7% d 1.54 moisture regain 7% (21C, 65% relative humidity) yellows slowly at 121C decomposes at approximately 148C low permanent set decomposed by acids swells in caustic but is undamaged. Soluble in cuprammonium hydroxide. Subject to mildew. May be dyed by direct, vat, azoic, sulfur, and basic dyes. Combustible. 

The kinetic energy correction is unnecessary for times of flow greater than 200 sec. In actual practice 0.5 g of finely cut dry cotton sample is dissolved in 100 ml of standardised cuprammonium hydroxide solution. The viscometer (Fig. 16-2) is... 

Mehta H U, Ravikrishnan M R and Chitale A G, A study of the abnormal viscosity of Procion-dyed cellulose in cuprammonium hydroxide , 7. Soc. Dyers Colourist, 1962,78, 552. 

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