Cellulose addition compounds

Of somewhat greater technical interest are the addition compounds and the cellulose esters and ethers. Of the apparent addition compounds the most important is alkali cellulose produced by steeping cellulose in caustic soda and considered to be of general form (CgHioOs), (NaOH) ) rather than a sodium alcoholate compound. Alkali cellulose is a particularly important starting point in the manufacture of cellulose ethers. The ability of aqueous cuprammonium hydroxide solutions to dissolve cellulose appears to be dependent on addition compound formation. 

As a result of development work between the Battelle Institute in Frankfurt and a German candle-making company, Aetema, biodegradable cellulose acetate compounds have been available since 1991 from the Rhone-Poulenc subsidiary Tubize Plastics. They are marketed under the trade names Bioceta and Biocellat. The system is centred round the use of an additive which acts both as a plasticiser and a biodegrading agent, causing the cellulose ester to decompose within 6-24 months. 

In 1991 Rhone-Poulenc offered biodegradable cellulose acetate compounds in which an additive acts both as plasticiser and biodegrading agent (see Section 22.2.2.1). 

Cellulose regenerated from the addition compound may demonstrate a certain degree of nitration (0.5—2.2% N). The properties of the compound are similar to those of hydrocellulose, eg, glittering fibers, increased hygro-scopicity and higher reactivity ... 

Hydrocellulose is formed when pure cellulose is subjected to the action of cold mineral acids solutions. Hydrolysis then proceeds by stages to yield glucose as the final product. It is possible to stop the hydrolysis at any desired moment, for example by diluting the reaction mixture with water. Hydrocellulose then remains in the form of non dissolved fibres or as powder (Girard [47]). The hydrolysis is usually performed by means of hydrochloric acid or with hydrogen chloride in an anhydrous medium. In the latter case, a water-soluble addition compound (C6H10O5)2.3HCl may occur as a transient product, as reported by Hess and M. Ullman [48]. 

Moreover, there is some evidence that the addition compound is also formed as a transient product in the first stage of nitrating cellulose by means of a mixed nitric and sulphuric acid. 

According to the present theory (e.g. Zherebov [1]) most of the hemicelluloses, pentosans and hexosans are removed during sulphitation, because calcium sulphite is capable of forming addition compounds with pentosans. Complete removal of hemicelluloses is only possible however after lignins have been removed, as lignin seems likely to be chemically combined with hemicellulose and thus with pentosans or hexosans. Only rupture of these bonds and the separation of lignins makes it possible to attack the non-cellulosic polysaccharides (Heuser and Haug [2]). 

Champetier and Yovanovitch108 treated com starch with aqueous sodium hydroxide solutions of various concentrations, and obtained three adducts having 1 2, 1 1, and 2 1 ratios of sodium hydroxide to D-glucose residue. No 2 3 or 3 4 adducts, such as those reported for cellulose, could be obtained. As the hydroxide concentration is changed, the transition from one addition compound to another is abrupt, thus showing an absence of topochemical fixation. 

Cellulose dissolves in Schweitzer s reagent, an ammoniacal solution of cupric oxide. After treatment with an alkali, ibe addition of carbon disulfide causes formation of sodium xanihate. a process used in the production of rayon. Sec also Fibers. The action of acetic anhydride in the presence of sulfuric acid produces cellulose acetates, the basis for a line of synthetic materials. See also Cellulose Ester Plastics (Organic). Nitrocelluloses are produced hy ihc action of nitric acid and sulfuric acid on cellulose, yielding compounds that are highly flammable and explosive. See also Explosives. 

Many thousands of phosphorus compounds have been described as having flame-retardant utility. The compounds demonstrating commercial utility arc much more limited in number. They include inorganic phosphorus compounds [red phosphorus, ammonium phosphates. insoluble ammonium polyphosphate, phosphoric acid-bascd systems for cellulosics). additive organic phosphorus flstme retardants... 

During the dissolution, an intermediate compound between cellulose and TFA is formed, which is described in the literature as an addition compound (II) and as a monoester (12). These compounds should give different theoretical yields—170% for the addition compound and 159% for the monoester (based on cellulose charge)—and different fluorine contents—20.6% and 22.1%, respectively. To check this, a-cellulose and glucose were treated with concentrated TFA at 120°C. After removing the TFA by evaporation, the reaction products were dried carefully at 40°C in vacuo over KOH pellets for 44 hr. The products were weighed and their fluorine contents determined. Another part of the reaction product was treated with water, dried, weighed, and analyzed for fluorine. 

Fluorescence can be used for detection in two different ways. Firstly, the separated compounds could be labeled with a fluorescent label (if not fluorescent as such), or UV absorbing compounds could be visualized as dark bands in matrices to which a fluorescent chromophore was added (fluorescence quenching). A variation of the second method was worked out by Eisinger [201] for polyacrylamide gel the gel was placed between a quartz and a fluorescent glass plate and then illuminated with UV light. Ultraviolet absorbing compounds appear as dark bands on the glass plate. When electrophoresis is done on sihca gel thin layer or cellulose, addition of a fluorescent indicator to the sorbent can be made use of in the conventional way. 

Of particular interest in connexion with our subject is the case of compound formation by a macromolecular solid e. g., the hydrate formation by cellulose and gelatin or the formation of an addition compound between nitrocellulose and acetone. Whereas in ordinary low molecular hydrates the composition of the successive compounds X, X. HgO, X. 2HaO etc. differs considerably as regards the percentage of water and, hence, the Gibbs potentials of these compounds differ by considerable jumps, the situation is different in macromolecular substances. If e.g., each monomeric residue R of a molecule consisting of a chain of n residues can bind one water molecule, the following hydrates are possible ... 

Qualitatively, the system rubber-benzene behaves exactly like the system consisting of the addition compound of nitro-cellulose with 6 molecules acetone and acetone (see proceeding section). 

Since swelling is intrinsically a process of dissolution, be it one of partial dissolution, or even, in its initial phases bound up with the formation of addition compounds (or hydrates if water is concerned), the volume contractions do not represent any new or specific phenomenon In cellulose and gelatin gels, by far the main part of the total contraction coincides with the range of hydrate formation. (cf. p. 541) and hence, may be connected with a chemical reaction, like the contraction occurring in the system sulphuric acid-water, or upon formation of crystalline hydrates of salts. It is known from numerous other examples that compound formation gives rise to a volume contraction. 

Staudinger formulated his ideas from studies of natural products (amylose, cellulose) and compounds obtained by addition polymerization. According to these ideas, addition polymerization is an event which causes... 

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