Viscose rayon cellulose

During the preparation of viscose rayon, cellulose is dissolved in a bath containing sodium hydroxide and later reprecipitated as rayon using a solution of sulfuric acid. Name the salt that is a by-product of this process. Rayon production is, in fact, a significant commercial source for this salt. 

In 1989, the estimated distribution of carbon disulfide utilization was as follows 34% of production went to manufacture viscose rayon, 6% to produce cellophane, 38% to produce carbon tetrachloride, 7% to produce rubber chemicals, and 15% to produce pesticides and to solubilize waxes and oils (HSDB 1995). Future use patterns remain uncertain, although it is expected that less may be used to produce viscose rayon, cellulose, and carbon tetrachloride, products for which the demand has declined and for which alternate production processes may be found (HSDB 1995 Mannsville Chemical Products Corp. 1985 Timmerman 1978). Unless substitutes for carbon disulfide are found, its use levels may depend largely on relative import and export levels of textiles and apparel (Mannsville Chemical Products Corp. 1985). Carbon disulfide use for many other specialty industrial purposes is expected to continue (HSDB 1995 Timmerman 1978). 

Rayon. Viscose rayon is obtained by reacting the hydroxy groups of cellulose with carbon disulfide in the presence of alkali to give xanthates. When this solution is poured (spun) into an acid medium, the reaction is reversed and the cellulose is regenerated (coagulated). 

The cellulose molecule contains three hydroxyl groups which can react and leave the chain backbone intact. These alcohol groups can be esterified with acetic anhydride to form cellulose acetate. This polymer is spun into the fiber acetate rayon. Similarly, the alcohol groups in cellulose react with CS2 in the presence of strong base to produce cellulose xanthates. When extruded into fibers, this material is called viscose rayon, and when extruded into sheets, cellophane. In both the acetate and xanthate formation, some chain degradation also occurs, so the resulting polymer chains are shorter than those in the starting cellulose. 

Originally, the word rayon was appHed to any ceUulose-based man-made fiber, and therefore included the cellulose acetate fibers. However, the definition of rayon was clarified in 1951 and includes textiles fibers and filaments composed of regenerated cellulose and excludes acetate. In Europe the fibers are now generally known as viscose the term viscose rayon is used whenever confusion between the fiber and the cellulose xanthate solution (also called viscose) is possible. 

Bulky Rayons. Unlike the thermoplastic synthetic fibers, viscose rayon cannot be bulked by mechanical crimping processes. Crimpers impart crimp to a regenerated cellulose fiber but it is not a permanent crimp and will not survive wetting out. 

Neste patented an industrial route to a cellulose carbamate pulp (90) which was stable enough to be shipped into rayon plants for dissolution as if it were xanthate. The carbamate solution could be spun into sulfuric acid or sodium carbonate solutions, to give fibers which when completely regenerated had similar properties to viscose rayon. When incompletely regenerated they were sufficientiy self-bonding for use in papermaking. The process was said to be cheaper than the viscose route and to have a lower environmental impact (91). It has not been commercialized, so no confirmation of its potential is yet available. 

There was significant interest in developing commercial processes based on phenolic resins in the 1890-1910 era. By this time, cellulose nitrate, vulcanized rubber, and viscose rayon had all found places in commerce [24]. Smith patented processes for manufacture of commercially useful molded articles from phenolic in 1899-1900 [2,25-28]. His products were made with phenol, paraldehyde (2,4,6-trimethyl-1,3,5-trioxane) or parafonnaldehyde, and additives in the presence of HCl at elevated temperatures. 

Most of the above can be made into plastic films - primarily used for wrapping. Film properties vary widely from permeable for food to impermeable to preserve dryness. Paper, treated or untreated, has been used for many years as a covering film, but has low strength when wet and is difficult to make transparent. In the 1920s, the transparency of cellophane revolutionized wrap. It is regenerated cellulose, like viscose rayon, except it is extruded in sheet instead of fiber, unfortunately it is sensitive to water and humidity. 

When ethanol is replaced by cellulose, sodium cellulose xanthate is obtained this dissolves in aqueous alkali to give a viscous solution (viscose) from which either viscose rayon or cellophane can be obtained by adding acid to regenerate the (reconstituted) cellulose. Trithiocarbonates (CS3 "), dithiocarbonates (COS2 "), xanthates (CS2OR ), difhiocarbamates (CS2NR2 ) and 1,2-dithiolates have an extensive coordination chemistry which has been reviewed. ... 

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). 

Since bacterial cellulose from all suitable carbohydrate substrates i8 identical with natural cellulose, its industrial importance20 is obvious. Relatively large amounts of bacterial cellulose were produced in Germany during the first World War. More recently products similar to parchment, mercerized cotton, cellulose nitrate,21 acetate14 and viscose rayons have been produced from bacterial cellulose. 

This term was originally intended to denote all kinds of man-made textile fibres, but is now applied only to cellulose types. Viscose rayon (regenerated from a solution of cellulose xanthate in sodium hydroxide) accounts for the greater part of world rayon production. Acetate rayon and cuprammonium rayon are relatively unimportant. 

Salts of the series of xanthic acids of the general formula ROCSSH. Certain xanthates such as ZIX are ultra accelerators for mbber. Cellulose xanthate is the intermediate product in the manufacture of viscose. See Viscose Rayon. Xanthogen Sulphide... 

In 1891, British chemistry Cross and Bevan discovered that wood pulp when treated with sodium hydroxide solution and carbon disulphide, gets converted into cellulose xanthate. When cellulose xanthate is dissolved in caustic soda solution it gives a viscous solution that could be spun to form fibres called Viscose Rayon. Rayon is produced in large scale today in many countries including India. Rayon (also know as viscose) is in fact regenerated cellulose. 

Rigid PVC is one of the polymers which are sometimes colored by P.R.112. Transparent systems (0.1% pigment) equal step 8 on the Blue Scale for lightfastness while the lightfastness of white reductions is only step 5-6. The spin dyeing industry employs P.R.142 for viscose rayon and viscose cellulose, in which the pigment exhibits excellent lightfastness and performs, if not perfectly, then almost satisfactorily. 

Due to the disadvantage of comparatively poor migration resistance, P.R.5 is not used in plasticized PVC, but it can be applied in rigid PVC. Its lightfastness is excellent in this medium, transparent and opaque colorations (up to 0.01% pigment + 0.5% TiOz) equal step 7 and, respectively, step 6-7 on the Blue Scale. Dispersed pigment preparations are available for the mass coloration of viscose films as well as for spin dyeing of viscose rayon and viscose cellulose. 

P.R.170 is not always heat stable enough to allow application in polyolefins. In HDPE systems formulated at 1/3 SD, the pigment tolerates exposure to 220 to 240°C for one minute. Its tinctorial strength, on the other hand, is excellent. P.R.170 is also occasionally used in polypropylene and polyacrylonitrile spin dyeing in the latter medium, it satisfies the specifications of the clothing and home textiles industries. Besides, P.R.170 lends color to viscose rayon and viscose cellulose it is used for the mass coloration of semisynthetic fibers made of cellulose last but not least, it colors yarns, fibers, and films made of secondary acetate. 

One of the earlier methods was to treat cellulose with sodium hydroxide and carbon disulfide to obtain xanthate esters which could be dispersed in water and cast into sheets or spun into fibers. Subsequent treatment with acid decomposed the xanthates and gave regenerated cellulose, either in fiber or film form. The fibers were called viscose rayon and the films were named cellophane. Cellophane is still used as a wrapping film and some of it is still manufactured by the xanthate process. By treatment with nitric acid, cellulose was converted to a trinitric acid ester, which could be cast into units which were satisfactory for making gun cotton for a smokeless powder for either artillery shells or shotgun ammunition. It was quite insoluble but it could be converted to a jelly-like mass, which could be shaped into a desired form for ammunition use. Under milder conditions, a lower nitrate... 

This is the first reported study of the spinning of mesomorphic cellulose solutions, but no fiber properties were given. Quenin et al. (14) used a d -jet, wet spinning system to spin cellulose/MMNO-H20 solutions. Fiber properties equiv dent to the best viscose rayon fiber were obtained. 

Approximately 73% of all North American sodium sulfate is obtained directly from natural salt sources in Searles Lake, California and in Texas, Mexico, and Canada. Miscellaneous methods of manufacture account for smaller percentages. This includes 5% as a by-product in the production of viscose rayon, where sulfuric acid and sodium hydroxide are used to degrade the cellulose. Sodium dichromate manufacture gives another 6% of sodium sulfate as a by-product. 

Amongst the important chemical conversions of macromolecular substances are the various reactions of cellulose. The three hydroxy groups per CRU can be partially or completely esterified or etherified. The number of hydroxy groups acetylated per CRU are indicated by the names, i.e., cellulose triacetate, cellulose 2-acetate, etc. Another commercially important reaction of cellulose is its conversion to dithiocarboxylic acid derivatives (xanthates). Aqueous solutions of the sodium salt are known as viscose they are spun into baths containing mineral acid, thereby regenerating the cellulose in the form of an insoluble fiber known as viscose rayon. 

Pacsu and coworkers144 have reported the preparation of the sodium alcoholatc of cellulose by treating either cotton or viscose rayon with either sodium methoxide or sodium 1-butoxide in anhydrous alcoholic media, at temperatures ranging from 25 to 120°. No proof of formation of alcoholate was offered. However, there is little reason to doubt its occurrence at the higher reaction temperatures. The ratio of sodium to D-glucose... 

The first application of the ferrous ion-hydrogen peroxide initiation for polymerizing vinyl monomers on and into cellulose fibers has been reported by Landeias and Whewell (41) in three successive papers. They are apparently the first who applied the "anchored catalyst technique, which other people have termed "in situ polymerization to cellulose grafting. The authors internally deposited methyl methacrylate, acrylonitrile, styrene, methyl vinyl ketone and methacrylamide in amounts between 10 and 80%. No attempt had been made to determine if actual grafting had occurred. In 1961 Richards (42) studied this question in great detail. Products obtained by polymerization of acrylonitrile and of styrene in viscose rayon were acetylated. Fractionation of... 

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