Cellulose modified, degradation

The cellulose modified of such a kind is resistant to degradation by cellulases. Corresponding finishes are much faster to washing or bleaching and to solvents than those achieved by simple impregnation procedures. 

Both the sulfite and alkaline (kraft) methods can be modified to produce high purity chemical ceUulose. These pulps, usuaUy in the form of "dissolving pulps," are not only mosdy free of lignin and hemiceUulose, but the molecular weight of the ceUulose is degraded. This increases solubUity in alkah and provides desired viscosity levels in solution. These dissolving pulps are used to make derivatives such as sodium ceUulose xanthate [9051 -13-2] via alkah ceUulose, and various esters and ethers (see Cellulose esters Cellulose ethers). 

Because of high interchain bonding, cellulose is insoluble in solvents and is incapable of flow on heating, the degradation temperature being reached before the material starts to flow. It is thus somewhat intractable in its native form. Cellulose, however, may be chemically treated so that the modified products may... 

Modifications of the organochemical properties of cellulosic fibers by graft polymerization with selected monomers impart new chemical properties. The microbiological and light resistances of cellulosic fibers to degradation are increased by grafting (3). Surface properties of modified fibers are changed to impart soil-release (35), dyeability (36), and flame-resistance (37, 38) properties. 

Bronsted acids such as sulfuric and hydrochloric acids and their ammonium salts, while serving as excellent catalysts, also lead to undesirable fibre degradation and unstable finish baths. Often citric acid is combined with a Lewis acid to provide an additional boost to the reaction, especially for the short shock condensation. A particularly powerful co-catalyst for ether modified DMDHEU products is sodium borotetrafluoride Na(BF ). But this flash catalyst may cause cellulose depolymerisation leading to high strength loss. 

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