Degradation partial cellulose

Solution Process. With the exception of fibrous triacetate, practically all cellulose acetate is manufactured by a solution process using sulfuric acid catalyst with acetic anhydride in an acetic acid solvent. An excellent description of this process is given (85). In the process (Fig. 8), cellulose (ca 400 kg) is treated with ca 1200 kg acetic anhydride in 1600 kg acetic acid solvent and 28—40 kg sulfuric acid (7—10% based on cellulose) as catalyst. During the exothermic reaction, the temperature is controlled at 40—45°C to minimize cellulose degradation. After the reaction solution becomes clear and fiber-free and the desired viscosity has been achieved, sufficient aqueous acetic acid (60—70% acid) is added to destroy the excess anhydride and provide 10—15% free water for hydrolysis. At this point, the sulfuric acid catalyst may be partially neutralized with calcium, magnesium, or sodium salts for better control of product molecular weight. 

According to Scheme 12, the alkaline peeling of cellulose should continue until the entire polymer is degraded. However, cellulose dissolves partially, but not completely, in hot alkali, and this remaining polysaccharide contains an increased carboxyl content.Thus, a second reaction is occurring that competes with the step-wise, peeling procedure. 

Typical one-step commercial mercerization of cotton yam with caustic or liquid ammonia causes only partial conversion to cellulose II or cellulose III. Cotton cellulose is partially converted to cellulose II by repeated mercerization, the swelling of cellulose in strong alkali (eg, 23% NaOH), followed by rinsing and drying. Cellulose III results from treatment of cellulose with liquid ammonia (ammonia mercerization) or amines. Cellulose III can be made from either cellulose I or II. When treated with water, cellulose III can revert to its parent stmcture. Cellulose IV can be prepared by treating cellulose I, II, or III in glycerol at temperatures 260°C. Conversion of the crystal form in cotton fibers to cellulose IV can be effected by heat treatment of ethylamine-treated cotton cellulose in either saturated steam or formamide with minimal fiber degradation (86). Like cellulose III, cellulose IV preparations can revert to their parent stmctures. 

Xandura E, Riedl B., Kokta B.Y Thermal degradation behavior of cellulose fibers partially esteri-fied with some long chain organic acids, Polym. Deg. Stab. 70 (2000) 387. 

A possible molecular structure of an element of the network is represented on the next page. When separated from cellulose by partial degradation during the manufacturing process of paper from wood, Ugnin is mainly used as fuel in paper industry. Before this ultimate stage, it would be iuterestiug to use it as material, and many attempts were performed in this respect. 

Mercerized cellulose fibers have improved luster and do not shrink further. One of the main reasons for mercerizing textiles is to improve their receptivity to dyes. This improvement may result more from the dismption of the crystalline regions rather than the partial conversion to a new crystal stmcture. A good example of the fundamental importance of the particular crystal form is the difference in rate of digestion by bacteria. Bacteria from cattle mmen rapidly digest Cellulose I but degrade Cellulose II very slowly (69). Thus aHomorphic form can be an important factor in biochemical reactions of cellulose as well as in some conventional chemical reactions. 

Acid anhydrides have been employed with, and without the use of a base catalyst. For example, acetates, propionates, butyrates, and their mixed esters, DS of 1 to ca. 3, have been obtained by reaction of activated cellulose with the corresponding anhydride, or two anhydrides, starting with the one with the smaller volume. In all cases, the distribution of both ester groups was almost statistic. Activation has been carried out by partial solvent distillation, and later by heat activation, under reduced pressure, of the native cellulose (bagasse, sisal), or the mercerized one (cotton linters). No catalyst has been employed the anhydride/AGU ratio was stoichiometric for microcrystalhne cellulose. Alternatively, 50% excess of anhydride (relative to targeted DS) has been employed for fibrous celluloses. In all cases, polymer degradation was minimum, and functionalization occurs preferentially at Ce ( C NMR spectroscopic analysis [52,56,57]). 

The drill-in fluids are typically composed of either starch or cellulose polymers, xanthan polymer, and sized calcium carbonate or salt particulates. Insufficient degradation of the filter-cakes resulting from even these clean drill-in fluids can significantly impede the flow capacity at the wellbore wall. Partially dehydrated, gelled drilling fluid and filter-cake must be displaced from the wellbore annulus to achieve a successful primary cement job. 

Two commercial disazo disperse dyes of relatively simple structure were selected for a recent study of photolytic mechanisms [180]. Both dyes were found to undergo photoisomerism in dimethyl phthalate solution and in films cast from a mixture of dye and cellulose acetate. Light-induced isomerisation did not occur in polyester film dyed with the two products, however. The prolonged irradiation of Cl Disperse Yellow 23 (3.161 X = Y = H) either in solution or in the polymer matrix yielded azobenzene and various monosubstituted azobenzenes. Under similar conditions the important derivative Orange 29 (3.161 X = N02, Y = OCH3) was degraded to a mixture of p-nitroaniline and partially reduced disubstituted azobenzenes. 

Fig. 39.—,3C-N.m.r. Spectra of A, 0-(Carboxymethyl)cellulose (d.s. 0.7), Partially Degraded by Cellulase, in D20 at 30° (R, signal of reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group) and of B, 0-(2-Hydroxyethyl)cellulose (d.s. 0.8), Partly Degraded by Cellulase, in D20 at 30°. (R, signal due to reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group.)...

Partially degraded cellulose is called hydrocellulose or oxycellulose, depending on the agent used for degradation. The term holocellulose is used to describe the residue after lignin has been removed from wood pulp. 

Recently, the effect on the nitration product of beating the cellulose prior to nitration has been studied by Ellefsen [97] who confirmed the well-known view that beating of cellulose was accompanied by partial degradation to soluble substances. However, the molecular weight was unchanged in those fractions of cellulose that did not dissolve in water. 

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