Cellophane, from cellulose xanthate

The dynamic mechanical properties of cellophanes (from cellulose xanthate) containing various amounts of water have been measured at 100—520 K and 10 —10 Hz. Four mechanical transitions were identified. 

Cellophane (regenerated cellulose from cellulose xanthate) is another material frequently used for dialysis. It has a pore size of approximately 4-8p and is impermeable to molecules with a relative molecular mass in excess of about 10,000. 

Viscose process A chemical process to produce viscose filaments of cellophane from cellulose pulp (e.g., treatment of cellulose with NaOH and CS2) yielding a highly viscous cellulose xanthate solution extrusion with a spinneret or splitting into a sulfuric acid bath followed by washing in water generates fibers or cellophane... 

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 is sometimes used in its original or native form as fibers for textile and paper, but is often modified through dissolving and reprecipitation or through chemical reaction. The xanthate viscose process, which is used for the production of rayon and cellophane, is the most widely used regeneration process. The cellulose obtained by the removal of lignin from wood pulp is converted to alkali cellulose. The addition of carbon disulfide to the latter produces cellulose xanthate. 

Alkali celluloses are extremely important intermediates because they exhibit a markedly enhanced reactivity compared with original cellulose. The reagents can penetrate more easily into the swollen cellulose structure and thus react with the hydroxyl groups. For instance, preparation of alkali cellulose, named mercerization after its inventor John Mercer (1844), is an important step when producing cellulose xanthate, from which viscose fibers and cellophane are prepared. 

Viscose is a solution of cellulose xanthate in caustic soda. This solution can be processed into rayon or cellophane. The production of viscose consists of two steps. First, certain forms of cellulose, mainly from sulfite pulp and cotton linters, are reacted with pure caustic soda. This reaction converts the -OH groups on the cellulose unit to -ONa. The caustic soda must be pure and is obtained from mercury cells. Caustic soda from diaphragm cells contains sodium chloride which makes it unusable without purification. This solution must be aged for 2-3 days. Aging reduces the length of the cellulose chain which makes it easier to dissolve into caustic soda. The second step involves the reaction of the alkali cellulose and carbon disulfide in excess caustic soda. The net reaction of viscose is ... 

Regenerated cellulose film, cellophane, can be cast from the solution of cellulose xanthate formed through the viscose process after which the film is subsequently hydrolyzed back to cellulose. Since the end product is essentially cellulose, it is readily biodegradable [11], Cellophane is typically plasticized with ethylene glycol, propylene glycol, or glycerol. To improve the barrier properties, cellophane is often coated with polyvinylidene chloride, which would hinder the biodegradability. 

Viscose solution The solution obtained by dissolving cellulose xanthate in caustic soda, from which viscose filaments and cellophane are produced. 

The important fiber rayon is simply regenerated cellulose from wood pulp that is in a form more easily spun into fibers. Cellophane film is regenerated cellulose made into film. One method of regeneration is formation of xanthate groups from selected hydroxy groups of cellulose, followed by hydrolysis back to hydroxy groups. 

It can also be made from sucrose by Acetobacter xylinum.71 This bacterial cellulose has high mechanical strength and might become an important material if the cost can be brought down. Regenerated cellulose fibers are known as rayon and regenerated films as cellophane. They are usually made by the xanthate process, which uses sodium hydroxide and carbon disulfide. 

A bio-derived plastic on the other hand is biopolymer that is chemically modified to improve its properties. Cellulose from plants can be acetylated to yield cellulose acetate, the bio-derived plastic used in cigarette filters. It can also be xanthated and extruded into cellophane (or Rayon), a bio-derived plastic. Chitin, a biopolymer from crab shells, can be processed (by converting the amide functionalities into amine functionalities) into its amine analog to obtain a bio-derived plastic, chitosan. 

Viscose vis- k6s [obs. viscose, adj, viscous] (1896) n. (1) A solution of xanthated cellulose in dilute sodium hydroxide from which rayon fibers and cellophane films are formed. The xanthated cellulose is produced by reacting alkali cellulose, i.e., wood fibers or cotton linters treated with sodium hydroxide, with oxygen and carbon disulfide. Rayon produced by this method is known as viscose rayon. (2) Generic name for fibers from regenerated cellulose (prepared by the xanthate method). Tortora PG (ed) (1997) Fairchild s dictionary of textiles. Fairchild Books, New York. 

Typical values for x ranged from 100 to 200. The substitutions of different hydroxyl groups, either by xanthation or by other substituents, have been related to the properties of regenerated fibers and transparent films (cellophane) produced. Solutions of cellulose zanthate were highly viscous and orange-red in color. The derivative became known as viscose. ... 

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