Purified Rayon

Note Avisco Rayon is purified rayon, a medicinal grade of rayon. 

Three forms of caustic soda are produced to meet customer needs purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Regular 50% caustic from the diaphragm cell process is suitable for most appHcations and accounts for about 85% of the NaOH consumed in the United States. However, it caimot be used in operations such as the manufacture of rayon, the synthesis of alkyl aryl sulfonates, or the production of anhydrous caustic because of the presence of salt, sodium chlorate, and heavy metals. Membrane and mercury cell caustic, on the other hand, is of superior quaUty and... 

CeUulose is the most abundant polymer, an estimated 10 t being produced aimuaUy by natural processes. SuppUes for the rayon industry can be obtained from many sources, but in practice, the wood-pulping processes used to supply the needs of the paper and board industries have been adapted to make the necessary speciaUy pure grade. Of the 3 x 10 t of wood used by the paper and board industry (13) in 1989, about 6 x 10 t were purified to provide the 2.5 x 10 t of dissolving pulp required by the viscose processes. 

Highly bleached and purified kraft process wood pulp suitable for conversion into products such as rayon, viscose, acetate, and cellophane... 

The continuous process for spinning and purifying textile-grade rayon yarn merits particular mention from the standpoint of industrial chemistry, as it is rather an axiom that a continuous process is to be preferred over a batch or discontinuous operation. This method employs advancing rolls or godets that make it possible for the yam to dwell for a sufficient length of time on each pair, thus allowing the several chemical operations to take place in a relatively small area. Their... 

After the filament rayon fiber has been spun and chemically purified, much of it passes through what are known as textile operations before it is ready to be knitted or woven. Because these steps of twisting and packaging or beaming are common to the manufacture of all manufactured fibers, it is advisable to review briefly the background and the processes. 

Platinum and palladium are useful in catalysis. Many of the elements are resistant to corrosion platinum is employed for electrodes and crucibles and extensively for spinnerets to extrude rayon, and rhodium provides a surfacing material for searchlight mirrors. Palladium is used for purifying hydrogen which diffuses rapidly and selectively through the warm metal. 

Grade Commercial, ground, flake, beads, FCC, granulated (60% and 75% NajO), rayon (low in iron, copper, and manganese), purified by alcohol (sticks, lumps, and drops), reagent, highest purity, CP, USP. 

Crude 10% sodium hydroxide containing sodium chloride is purified in a similar manner to the product of the causticization process. The water is evaporated in nickel or nickel-clad steel (to reduce corrosion) multiple-effect evaporators to about 50% sodium hydroxide concentration. At this concentration, sodium chloride is only about 1% soluble (2%, on a dry basis) in the more concentrated caustic so that the bulk of it crystallizes out and is filtered off. This quite pure sodium chloride is recycled to the cells. Lor many purposes, such as for pulp and paper production, this purity of 50% sodium hydroxide is quite acceptable. If higher purities are required, sodium hydroxide may be separated from residual water and salt by chilling to the double hydrate crystals NaOH 2HiO, m.p. about 6°C, or as NaOH 3.5HiO, with a m.p. of about 3°C, or by counter-current extraction [9]. The sodium hydroxide obtained after these steps contains 2-3 ppm sodium chloride, equivalent to the purity of the mercury cell product ( rayon grade ) [10]. Concentrations of 73% and 100% sodium hydroxide (see details, Section 7.5) are also marketed. 

In the production of Chardonnet rayon, purified cotton or linters are treated with a mixture of nitric and sulphuric acids at a temperature not exceeding 40°C for a period of between 4 and 6 hours. The excess of acid is then run off and the nitrated cotton is washed with water until free from acid. It is subsequently hydro-extracted and pressed until it contains about 30 per cent of water. This nitrocellulose is dissolved in a mixture composed of equal volumes of alcohol and ether in a closed vessel provided with a stirring mechanism. The solution is filtered under pressure and then stored. 

Cuprammonium rayon is made from scoured and bleached cotton linters or purified wood pulp with a high a cellulose content. The cellulose is washed and then pressed until it contains about 50 per cent of water. In this state, it is placed in a mechanical mixer together with cuprammonium solution and agitated until completely dissolved, whilst the temperature is maintained at 5° C (41 °F). The solution is then diluted to about 10 per cent concentration. After filtration and exposure to vacuum to remove air bubbles and dissolved gases, the solution is allowed to ripen in enclosed vessels until it is the desired viscosity. In modem practice copper carbonate is mixed intimately with the cellulose in a shredding machine and the resultant mass is then broken up and stirred for some hours with aqueous ammonia and caustic soda, when it passes into solution. 

NaS.CS.O(CeH,0,) 4-HjS04=Na2SO + CS, + 2C,Hio05 Viscose rayon may be manufactured from cotton linters but the usual starting point is wood pulp preferably derived from spruce. The crude wood chips are purified by treatment first with calcium bisulphite and then by boiling with steam under pressure for about 14 hours. This does not... 

In the preparation of secondary cellulose acetate rayon cotton linters, waste cotton or high-grade wood pulp is purified by boiling with alkali followed by hypochlorite bleaching. After purification the cellulose is dried... 

Fig, 1.—Set of F our Diagrams from Ramie and Rayon Fibers, Corresponding to the Four Principal Polymorphs of Cellulose. ((A) Cellulose I (native) from purified ramie fibers, (B) Cellulose II (mercerized or regenerated) from Fortisan fibers, (C) Cellulose III (ammonia) from ramie fibers treated with ethylamine, and (D) Cellulose IV (high temperature) from fibers of ramie cellulose III treated with gIy< rol at 280 .]... 

USE- Solvent for fats. oils, waxes, resins, rubber, plastics, lacquers, varnishes, rubber cements. Manul methyl nobutyl ketone, mesityl oxide, acetic acid (ketenc process), diacctone alcohol, chloroform, iodoform, bromoform, explosives, aeroplane dopes, rayon, phntographic films, isoprene. storing acetylene gas (takes up about 24 times its vol of the gas) extraction o various principles from animal and plant substances m paint and varnish removers, purifying paraffin, hardening and dehydrating tissues Pharmaceutic aid (solvent)... 

Dialysis (5) Liquid Difference in diffusion rate across membrane Membrane Recovery of purified caustic soda from rayon process liquid, Vol. 7, p. 14... 

Acetone is used in the manufacture of a large number of compounds, such as acetic acid, chloroform, mesityl oxide, and MIBK in the manufacmre of rayon, photographic films, and explosives as a common solvent in paint and varnish removers and for purifying paraffins. 

In the early days, viscose composition was around 7.0% cellulose, 6.0% NaOH, and 34% CS2 (based on cellulose), with a viscosity of about 50 P. Wood pulp of about 88% a-cellulose content was the typical cellulose source for ordinary rayon, although purified cotton linters were used for higher-strength rayons. With commercialization of the zinc-based process. 

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