Regenerated cellulose product

The use of membranes for separating particles of colloidal dimensions is termed dialysis. The most commonly used membranes are prepared from regenerated cellulose products such as collodion (a partially evaporated solution of cellulose nitrate in alcohol plus ether), Cellophane and Visking. Membranes with various, approximately known, pore sizes can be obtained commercially (usually in the form of sausage skins or thimbles ). However, particle size and pore size cannot be properly correlated, since the permeability of a membrane is also affected by factors such as electrical repulsion when. the membrane and particles are of like charge, and particle adsorption on the filter which can lead to a blocking of the pores. 

Heteropolysaccharides are, in general, highly desirable components of paper-grade pulps while they are not tolerated in dissolving-grade pulps used for the production of regenerated cellulose products and cellulose derivatives. A vast body of literature exists on the effects of hemicellu-loses on the papermaking process. 

Rubber from trees has been used in both solid and latex form, and also converted further into isomerized and chlorinated polymers of very different properties and uses. Wood from trees is used directly for plywood, composition board, and wood-flour reinforcement of phenolic resins. The cellulose from wood is purified and used for laminates and for regenerated cellulose products such as cellophane, viscose rayon, and vulcanized fibre. The lignin from wood has been explored for use in plastics, but never carried through to complete commercial success. 

Regenerated cellulose fibers are uniform in diameter. This permits a tmiform oxidation and imparts uniform chemical and physical characteristics to the pharmaceutical material. In the early 1960 s, Johnson Johnson entered the market with an oxidized knitted rayon fabric, SURGICEL Absorbable Hemostat. Since then, Johnson Johnson has dev eloped a few other oxidized knitted rayon products. A list of currently av ailable bioabsorbable oxidized cellulose and oxidized regenerated cellulose products, and the respecthe manufacturer is contained in TkdUe 1. A list of relevant patents for oxidized cellulose technology is contained in IkUe 2. 

Table 1. 1990 World Production of Regenerated Cellulose Fibers...

Sulfates of sodium are iadustriaUy important materials commonly sold ia three forms (Table 1). In the period from 1970 to 1981, > 1 million metric tons were consumed aimuaHy ia the United States. Siace then, demand has declined. In 1988 consumption dropped to 890,000 t, and ia 1994 to 610,000 t (1,2). Sodium sulfate is used principally (40%) ia the soap (qv) and detergent iadustries. Pulp and paper manufacturers consume 25%, textiles 19%, glass 5%, and miscellaneous iadustries consume 11% (3). About half of all sodium sulfate produced is a synthetic by-product of rayon, dichromate, phenol (qv), or potash (see Chromium compounds Fibers, regenerated cellulosics Potassium compounds). Sodium sulfate made as a by-product is referred to as synthetic. Sodium sulfate made from mirabilite, thenardite, or naturally occurring brine is called natural sodium sulfate. In 1994, about 300,000 t of sodium sulfate were produced as a by-product another 300,000 t were produced from natural sodium sulfate deposits (4). 

Production of cellulose esters from aromatic acids has not been commercialized because of unfavorable economics. These esters are usually prepared from highly reactive regenerated cellulose, and their physical properties do not differ markedly from cellulose esters prepared from the more readily available aHphatic acids. Benzoate esters have been prepared from regenerated cellulose with benzoyl chloride in pyridine—nitrobenzene (27) or benzene (28). These benzoate esters are soluble in common organic solvents such as acetone or chloroform. Benzoate esters, as well as the nitrochloro-, and methoxy-substituted benzoates, have been prepared from cellulose with the appropriate aromatic acid and chloroacetic anhydride as the impelling agent and magnesium perchlorate as the catalyst (29). 

Cellulose may be solubilised by treatment with sodium hydroxide and carbon disulfide. It can be regenerated by acidification of the solution. This is the basis of the production of regenerated cellulose fibre, so-called viscose rayon , which is a major textile fibre. The technique is also used for the production of continuous cellulose-derived film, so-called cellophane (from cellulose and diaphane , the latter being French for transparent). 

Membranes UF membranes consist primarily of polymeric structures (polyethersulfone, regenerated cellulose, polysulfone, polyamide, polyacrylonitrile, or various fluoropolymers) formed by immersion casting on a web or as a composite on a MF membrane. Hydrophobic polymers are surface-modified to render them hydrophilic and thereby reduce fouling, reduce product losses, and increase flux [Cabasso in Vltrafiltration Membranes and Applications, Cooper (ed.). Plenum Press, New York, 1980]. Some inorganic UF membranes (alumina, glass, zirconia) are available but only find use in corrosive applications due to their high cost. 

Cellulose in the form of cotton linters, wood pulp or regenerated cellulose is used as the raw material for the commercial production of cellulose ethers. The advantage which linters possess over wood pulp in the manufacture of cellulose esters is not so apparent in the case of the ethers. 

In the original process the cellulose nitrate itself was used as the fiber (hence its satirical description as mother-in-law silk ). The regenerating agent is ammonium hydrosulfide. The basic process was first demonstrated by J. W. Swan in London in 1885 but commercialized by Count L. M. H. B. de Chardonnet ( Father of the rayon industry ) in France in 1891 and operated there until 1934. The last working factory, that in Brazil, was burnt down in 1949. The other processes for making rayon fibers by regenerating cellulose ( viscose, cupram-monium) gave superior products. See also Rayon. 

Viscose Also known as the Cross-Bevan-Beadle process. A process for making regenerated cellulose fibers. The product has been known by the generic name rayon since 1924. Cellulose, from cotton or wood, is first reacted with sodium hydroxide ( mercerization), yielding alkali cellulose. This is dissolved in carbon disulfide, yielding cellulose xanthate, which is dissolved in sodium hydroxide solution. Injection of this solution (known as viscose... 

China. See also People s Republic of China acrylic fiber production in, 11.T89, 220 adhesive joint ventures, 1 526 advanced materials research, 1 696 aquaculture history, 3 183 aquaculture production, 3 189t ascorbic acid synthesis in, 25 754 demand for oil in, 23 530 nanocomposite development, 1 717 natural graphite in, 12 780 oil recovery program in, 23 534 olefin fiber production in, 11 243 production and consumption of regenerated cellulose fibers in,... 

Direct current closed furnace technology, in silicon production, 22 506 Direct digital control (DDC), 20 668 Direct dissolution processes, for regenerated cellulose fibers,... 

France. See also French Patent Office aquaculture production, 3 189t piezoelectric ceramics research, 1 708 regenerated cellulose fibers in, 11 249 Franck-Condon shift, 22 215 Frank-Caro cyanamide process, 17 292 Frankia species, in nitrogen fixation, 17 299... 

Manual code system, in searching patent literature, 18 223-225 Manual of Classification, 18 209 Manuals of Policies and Procedures (MAPPs), 13 688 Manufactured carbon, 4 735 Manufactured fibers, 11 165, 174-175 24 613-614, 616-618. See also Regenerated fibers Synthetic fibers olefin, 11 231-242 regenerated cellulose, 11 247 Manufactured graphite, 4 735 Manufactured products, nanotechnology and, 17 44-45 Manufactured water, 26 96 Manufacturing... 

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