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Xanthate derivative, cellulose

The next significant strength improvement followed the 1950 Du Pont (19) discovery of monoamine and quaternary ammonium modifiers, which, when added to the viscose, prolonged the life of the ziac cellulose xanthate gel, and enabled even higher stretch levels to be used. Modifiers have proliferated siace they were first patented and the Hst now iacludes many poly(alkylene oxide) derivatives (20), polyhydroxypolyamines (21—23), and dithiocarbamates (24). [Pg.349]

Cellulose (VIII) is spun into fiber or cast into film by using a chemical reaction to convert it into a soluble xanthate derivative (Turbak, 1988). This is achieved by treating cellulose with 18-20% aqueous sodium hydroxide solution at 25-30°C for about 0.5-1 h. Much of the sodium hydroxide is physically absorbed into the swollen polymer some of it may be in the form of cellulose alkoxides. The excess alkali is pressed out of the cellulose pulp and the mass aged to allow oxidative degradation of the polymer chains to the desired molecular weight. The alkali cellulose is then treated with carbon disulfide at about 30° C and the resulting mass dissolved in dilute sodium hydroxide to form the sodium... [Pg.745]

An ingenious treatment of cellulose was discovered by Charles Cross and Edward Bevan in England in 1892. It involved first preparing a chemical derivative called cellulose xanthate in a process that is conceptually no different from converting cellulose into other derivatives such as cellulose acetate or cellulose nitrate. What made this different, however, is that xan-thates are reactive chemical intermediates that can be converted easily into still different compounds, or returned to the starting material, in this case cellulose. See Equation 3. [Pg.55]

The preparation of viscose rayon fibers and cellophane proceeds via the xanthate, which therefore is an extremely important derivative of cellulose. Treatment of alkali cellulose with carbon disulfide results in the formation of cellulose xanthate (dithiocarbonate) ... [Pg.182]

In 1932 Lieser and his associates, following some work on the constitution of cellulose xanthate, which had indicated C2 as the probable position of substitution in the D-glucopyranose residue, embarked on a study of the xanthation of other carbohydrates and polyhydric alcohols. In the first paper of the new series, Lieser and Nagel, having failed to obtain an 0-(thiolthiocarbonyl) derivative of glyceritol under anhydrous conditions, introduced the use of aqueous barium hydroxide as the basic reagent. The... [Pg.135]

In their comparative studies, Rogovin and coworkers confirmed the sensitivity of 0-(methoxycarbonyl)celluloses toward aqueous alkali, noted earlier by Heuser and Schneider, but found an 0-[(methylthio)thiocar-bonyl] derivative to possess enhanced stability, similar to that of cellulose acetate. Thus, whereas the action of N sodium hydroxide at 25° causes almost complete de-esterification of O-(methoxycarbonyl) cellulose in 5 minutes, the methyl xanthate suffers only 20 % hydrolysis during 1 hour. No quantitative data of this nature are available for the corresponding mono-thiocarbonate. The product from its iodine oxidation was far more stable than that (see p. 147) derived from cellulose xanthate. The 0-[(methyl-thio)thiocarbonyl] derivative of methyl a-D-glucopyranoside was seemingly more alkali-sensitive than the cellulose analog described above, possibly on account of its higher solubility. [Pg.149]

Cellulose is the most abundant naturally oeeurring polysaccharide formed out of glucose-based repeat imits, connected by 1,4-beta-glucosidic linkages. Cellulose and its derivatives are widely used as tough versatile materials. Cellulose nitrate, cellulose acetate (CA) and cellulose xanthate (rayon) can be easily molded or drawn into fibers for textile applications, for designing composite materials (safety glass), as thermoplastics etc [80]. [Pg.140]

Cellulose is a fibrous, tough, water-insoluble, and crystalline substance. As a result of these characteristics, it is often converted to its derivatives in order to make it more useful. The most commonly used derivatives of cellulose are carbox-ymethylcellulose, methylcellulose, hydroxyethylceUulose, hydroxypropylcellulose, cellulose acetate, and cellulose xanthate (12). Among these derivatives, cellulose acetate and cellulose xanthate are cellulose esters, which are now widely used in the manufacturing of fibers, films, and in injection molding thermoplastics. [Pg.3260]

In contrast to the polymeric products derived from fossil fuels, the production of synthetic polymers from biomass—the rayons and cellulose acetates—is quite small despite the fact that cellulose is one of the world s most abundant raw materials. The rayons are any of a variety of regenerated celluloses manufactured via intermediates such as alkali salts and cellulose xanthates. The process... [Pg.506]

Water soluble derivatives of cellulose have also been made through the formation of sodium cellulose xanthate (Cell-O-CS Na ) ( 12) and copper amine complexes (that is, the cuprammonlum process) ( X3). Both these derivatives require regeneration of the Insoluble cellulose structure at the time of membrane formation. Strong salt and acid solutions are used to precipitate the soluble derivatives and simultaneously recover the cellulose structure. Residues of xanthate or cuprammonlum salt decomposition must subsequently be washed out of the resulting membrane. [Pg.102]

The processes used to prepare cellulosic membranes generally lead to homogenous cross-sectional structures. Cellulose prepared from xanthate derivatives may exhibit a cuticle or skin structure however, this asymmetry does not produce significant resistance to mass transfer. Most membranes currently used for hemodialysis are prepared via the cuprammonlum process. These membranes do not form a skinned structure during coagulatlon/regeneratlon. [Pg.104]

A major industrial use of cellulose is in the preparation of various cellulose derivatives, primarily cellulose acetate, cellulose nitrate, and cellulose xanthate, each of which has a number of applications. [Pg.198]

The importance of polysaccharide derivatives to industry and society is frequently overlooked by, or even unknown to, many chemists. However, those who have an interest in the subject will know of the great economic investment involved in the industrial production of polysaccharide derivatives for inclusion in a wide variety of commodities, such as explosives, synthetic fibers and fabrics, foodstuffs, paints, and plastics. Indeed, several polysaccharide derivatives have been known and commercially exploited for a long time (for example, cellulose xanthate for rayon, and cellulose nitrate for explosives), and, just a few years ago, it might have been claimed that the use of polysaccharide derivatives had reached a peak. [Pg.306]

The modification of cellulose with alkaline carbon disulfide to introduce xanthate groups has been extensively exploited in the industrial production of viscose. Early work on the preparation and properties of starch xanthate has been discussed. Xanthate derivatives of cellulose and starch have been discussed with respect to general xanthate chemistry, and the xanthation of cellulose in homogeneous medium is known to be a second-order reaction. Cellulose xanthate shows some potential as a matrix for enzyme insolubilization, " and stable derivatives of this xanthate may be prepared by transesterification. Thermal decomposition of cellulose allyl- and benzyl-xanthates gives 5,6-cellulosene. Some thiocarbonyl derivatives of polysaccharides have been prepared. "... [Pg.346]

REACTIONS OF POLYMERS xanthate derivative of cellulose (XXFV) ... [Pg.746]

The soluble derivative, sodium cellulose xanthate, is formed by reacting alkali cellulose with carbon disulfide. The reaction has been studied for both cellulose and simple model systems [151,152]. Xanthation is normally conducted by placing alkali cellulose crumb in a reactor, pulling a vacuum, and then introducing CS2. As the reaction proceeds, CS2 is consumed and the vacuum is regained. The extent of vacuum regain is used to follow the reaction. [Pg.723]

Polyoxyalkylene derivatives are typical of the oxygen-containing viscose modifiers. In this type of modifier, association involving the ether oxygen of the polyoxyalkylene chain is believed to be part of the mechanism by which acid diffusion and cellulose regeneration are retarded. Two possibilities exist, (I) protonation of the ether oxygen [200] retards hydrogen ions from penetration into the filament and facilitates formation of zinc cellulose xanthate and (II) formation of chelate compounds with zinc and zinc salts that increase the stability of the semipermeable membrane [201]. [Pg.730]

Formaldehyde added to the spin-bath is a useful regeneration-retardant [125] that, in acidic solution, forms an S -methylol derivative (Equation 10.18) of cellulose xanthate [218]. [Pg.731]

The chemical industry s interest in polymers dates back to the 19th century. In those days it was a case of synthetically modifying natural polymers with chemical reagents to either improve their properties or produce new materials with desirable characteristics. Notable examples were nitration of cellulose giving the explosive nitrocellulose, production of regenerated cellulose (rayon or artificial silk) via its xanthate derivative, and vulcanization of rubber by heating with sulphur. Manufacture of acetylated cellulose (cellulose acetate or acetate rayon) developed rapidly from 1914 onwards with its use both as a semi-synthetic fibre and as a thermoplastic material for extrusion as a film. [Pg.66]


See other pages where Xanthate derivative, cellulose is mentioned: [Pg.33]    [Pg.368]    [Pg.540]    [Pg.33]    [Pg.368]    [Pg.540]    [Pg.347]    [Pg.367]    [Pg.118]    [Pg.297]    [Pg.215]    [Pg.746]    [Pg.746]    [Pg.21]    [Pg.34]    [Pg.133]    [Pg.145]    [Pg.150]    [Pg.367]    [Pg.507]    [Pg.60]    [Pg.140]    [Pg.280]    [Pg.196]    [Pg.238]    [Pg.7]    [Pg.10]    [Pg.121]    [Pg.197]    [Pg.746]    [Pg.729]   
See also in sourсe #XX -- [ Pg.60 ]




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Cellulose xanthate

Cellulose xanthation

Xanthates

Xanthation

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