Cellulose, alkali investigations

Shorygin and Khait [57] first drew attention to the fact that cellulose brought into contact with nitrogen dioxide is converted into a substance totally soluble in alkali solution. This reaction was then investigated in more detail by Kenyon et al. [58] as well as by Rogovin et al. [59]. 

A much more extensive investigation of the effect of alkalies has been made in the case of polysaccharides, especially cellulose this is understandable in view of the industrial importance of mercerization, of the viscose process, and of cellulose ethers. Various complexes have been reported for cellulose and alkalies depending upon the nature of the alkali, upon its concentration, upon the washing treatment used, and upon the pretreatment of the cellulose. A discussion of this subject has been published by Nicoll and Conaway.84 There is general agreement on the formation of several compounds, which are susceptible to hydrolysis. The question as to whether these compounds are molecular complexes (XLVII), true alkoxides (XLVIII), or an equilibrium mixture of the two has not been answered. In recent studies Lauer65 has reached... 

Yong et ah [175] developed an effective omeprazole buccal adhesive tablet with excellent bioadhesive force and good drug stability in human saliva. The omeprazole buccal adhesive tablets were prepared with various bioadhesive polymers, alkali materials, and croscarmellose sodium. Their physicochemical properties, such as bioadhesive force and drug stability in human saliva, were investigated. The release and bioavailability of omeprazole delivered by the buccal adhesive tablets were studied. As bioadhesive additives for omeprazole tablet, a mixture of sodium alginate and hydroxypropylmethyl cellulose was selected. The omeprazole tablets prepared with bioadhesive polymers alone had bioadhesive forces suitable for a buccal adhesive tablet, but the stability of omeprazole in human saliva was not satisfactory. Magnesium oxide is an alkali stabilizer for omeprazole buccal adhesive tablets. Croscarmellose sodium enhanced the release of omeprazole from the tablets but it decreased the bioadhesive forces and stability of omeprazole tablets in human saliva. 

Since Mercel discovered the process of the so-called mercerization of cellulose (a process leading to cotton fabrics by treating cellulose under tension with an aqueous alkali solution), the swelling phenomena of cellulose in an aqueous alkali solution have been studied in detail, by many investigators. For example, for natural cellu-... 

Investigations of the cellulose esters of benzoic acid have so far not led to products of commercial interest. Benzoyl chloride reacts in the presence of pyridine at elevated temperatures, most suitably by the use of a higher boiling neutral solvent as diluent." Benzoyl derivatives have also been prepared by the reaction of the acid chloride on alkali cellulose. A combination of pyridine and alkali has been reported to be advantageous."... 

In the present study, the role of cellulose physical structure in alkaline reactions was investigated by comparing the alkaline degradation of highly crystalline (cellulose I) fibrous hydrocellulose with that of amorphous (noncrystalline) hydrocellulose. The amorphous substrate was taken as a cellulose model the reactivity of which would most closely approximate that of alkali-soluble cellulose. The availablity of such an approximation to the inherent reactivity of cellulose allowed evaluation of the effects of the more highly ordered structure of the fibrous hydrocellulose. 

Another way to achieve rapid depolymerization is to irradiate the cellulose with a beam of accelerated electrons [146-148]. In this case, the time required for the depolymerization is of the order of seconds. This technology has been investigated as a means to eliminate the need to age alkali cellulose in the viscose process, and rayon has been successfully made from irradiated pulp [149,150]. The process, however, has not been adopted by the industry because, like double steeping, material handling poses special requirements. 

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