Alkoxylation Cellulose

Propylene oxide has found use in the preparation of polyether polyols from recycled poly(ethylene terephthalate) (264), haUde removal from amine salts via halohydrin formation (265), preparation of flame retardants (266), alkoxylation of amines (267,268), modification of catalysts (269), and preparation of cellulose ethers (270,271). 

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.)...

When two of the chlorine atoms are substituted, for example with amino or alkoxyl groups, monochlorotriazinyl dyes 2 are obtained. These are considerably less reactive, and hence react with cellulose in the exhaust dyeing process only at relatively high temperature (80°C). Such dyes are especially advantageous for printing [14],... 

Anthrimide Carbazoles. Fast vat dyes are produced by carbazole ring closure from a,a-dianthraquinonylamines (anthrimides). The shade is determined by the number and position of the carbazole systems and by additional substituents, especially acylamino or alkoxyl groups. Anthraquinone carbazoles make it possible to dye cellulose fibers in level, very fast yellow, orange, brown, gray, and olive shades. However, this series lacks dyes with bright shades. 

Mention has already been made of the numerous effects attendant upon chemical substitutions on the polysaccharide linear chain. Natural branches impart a dispersion stability to amylopectin that is not afforded amylose. One only has to compare cellulose ethers, deesterified chitin, and the lysis product of protopectin with the underivatized parent compound to appreciate the impact of chemical substituents on functionality. The loosening of compact, parallel structures with alkyl, hydroxyalkyl, and alkoxyl groups facilitates hydration and transforms insoluble, refractory polysaccharides to soluble, reactive polysaccharides. Not only do these substituents obstruct the crystallization tendency, they almost always confer secondary functionalities like q enhancement and foam, suspension, and freeze-thaw stabilization. 

The basic mechanism operating in the hot alkaline treatments of cellulose is the beta-alkoxyl carbonyl elimination reaction of Isbell [416] ... 

The activation treatment involves steeping cellulose (cotton or pulp fibers in sheet form) with cold 15 to 20% aqueous alkali for several hours. This alkali cellulose is subsequently reacted with reagents that consume alkali (Williamson synthesis) or alternatively in reactions in which alkali serves as catalyst (alkoxylation). Reactions are carried out between room temperature and 110 °C. Following reaction, cellulose ethers in solid fiber form (by virtue of being suspended in a small polar solvent such as isopropanol) are washed with aqueous alcohol, dried, and powdered by granulation (O Fig. 23). 

Methyl cellulose and hydroxyalky methyl cellulose manufacture involves in part Williamson synthesis with methyl chloride and alkoxylation. The various ethers are used primarily in building materials and in industrial applications (O Table 13). Higher grades with greater purities consist of modified vegetable gums, and they find uses in controlled release applications in pharmaceuticals, and in food products and cosmetics where they serve as emulsifiers and texture agents. 

Step polymers can be reacted with alkoxylignin to form alko lignin esters, thermodynamic and equilibrium forces dictate that the best products from this chemistry will come from step- reaction polymers capped with isocyanate groups. New products of alkoxylated lignin covalently bonded to cellulose acetate or caprolactam are known and are available tor utilization. 

The Ziesel reaction has been used for the determination of alkoxyl groups in cellulosic materials [65-67] and the determination of ether groups in cellulose and polyvinyl ethers [68]. However, hydriodic acid also cleaves any ester linkages on the polymer backbone, giving positive interference. 

A number of compounds of this type are in use and they consist of methyl (and in some cases ethyl or hydroxypropyl)ethers of cellulose they are characterised by their alkoxyl content. A general method for the determination of methoxyl groups is as follows ... 

H. is produced by - alkoxylation of alkali-cellulose suspended in solvents, such as acetone, isopropanol or tcrt.butanol 0.8-1.5 moles of alkali per AGU are necessary. To decrease viscosity, the alkali-cellulose is degraded by aging (- cellulose) before reaction or by adding hydrogen peroxide to the alkaline reaction mixture. For better efficiency, the addition of ethylene oxide is carried out in two stages. After the first reaction step, only catalytic amounts of alkali are necessary. Reaction takes place in 1-4 h at 30-80 °C and is stopped by neutralization with hydrochloric or acetic acid. Salts are removed by washing with alcohol/water mixtures. If retarded dissolution in water is desired, the wet product is treated with glyoxal. 

H. is manufactured (->alkoxylation) by a slurry process similar to that used for - -hydroxyethyl cellulose. A MS of >3.5 is usual. 

Cross, J., ed.. Nonionic Surfactants Chemical Analysis, Marcel Dekker, New York, 1987. Hodges, K. L., W. E. Kester, D. L. Wiederrich, J. A. Grover, Alkoxyl substitution in cellulose ethers by Zeisel-GC, Anal. Chem., 1979,51, 2172-2176. 

---