Cellulose components

Degradation of wood is also observed adjacent to anodic corrosion sites. Some metal ions, notably Fe, catalytically decompose the cellulose components of wood. This significantly reduces the wood s fastener-holding ability. 

If a padding process is used to brighten a polyester/cotton blend, both the disperse and anionic brighteners may be applied from the same pad bath, even when a resin finish is applied simultaneously to the cellulosic component of the blend. Similarly, both types of... 

Scholler A process for making glucose from wood by acid hydrolysis of the cellulose component under pressure. Invented by H. Scholler in Germany in 1929. Operated in Germany in the 1920s and in Russia in the 1970s. 

Considerable research effort has been devoted to developing a new generation of disperse dyes designed to optimise fastness to washing and minimise cross-staining of the cellulosic component of polyester/cellulosic blends [97,98]. Diester-containing monoazo disperse dye structures (4.91) that yield a dicarboxylic acid on hydrolysis and certain thienylazo blues... 

The hemicelluloses are soluble in alkali, and can therefore be readily separated from the cellulose component by alkali extraction. However, this can only be done when the wood has first been delignified. This is because they are probably linked to lignin via covalent ester linkages (see Chapter 3) which need to be cleaved... 

Traditionally, com is dry-milled and suspended in boiling water to free the carbohydrate-rich starch compound from the nonstarch, cellulose biomass. The starch and cellulose components at this stage carry through the process. The non-convertible cellulose biomass is later separated. The milled com-water slurry, called mash, is boiled for about 1 hour. Enzymes such as a-amylase can be added to the process to help prevent gellation of starch. 

Wood forms one of the world s most important chemical raw materials. It is the primary source of cellulose for the pulp and paper and cellulose industries. These industries are well up in the group of 10 major industries of the United Slates. For paper, rayon, films, lacquers, explosives and plastics, which comprise the greatest chemical uses of wood, it is the cellulose component (plus certain amounts of hemicellulose) of wood that is of value. The lignin forms a major industrial waste as a by-product of the paper and cellulose industries. Its major use is in its heat value in the recovery of alkaline pulping chemicals. A variety of minor uses for lignin have been developed, such as for the manufacture of vanillin, adhesives, plastics, oil-well drilling compounds and fillers for rubber. 

Cellulose Component tion Mixture) (Aeeo) (Aeeo)... 

Tt is a widely recognized fact that true cellulolytic microorganisms A produce three basic cellulase components IS), and that these enzyme components act in concert to hydrolyze crystalline cellulose to glucose (6). Many research laboratories have undertaken the task to purify cellulose components from various cellulolytic microorganisms and to study the mechanisms of cellulose hydrolysis. Much information has accumulated concerning the mode of action of cellulose hydrolysis since Reese et al. first proposed the Ci-C concept (7). In spite of this, however, conflicting reports still flourish concerning the composition of the "cellulase complex, the multiplicity of cellulase components, the biosynthesis of cellulose, and the mechanisms of cellulose hydrolysis. 

Reactive dyes are well suited to dye blends of cellulose and PA fibers. Clear shades with very good fastness are obtained. Like with vat dyes, the depth of shade of reactive dyes depends relatively strongly on the type of PA and structural differences. Dyeing is carried out in a three-step process with appropriately selected products. First, the reactive dyes in a weakly acidic liquor are allowed to absorb on the PA component. Salt is then added to improve the yield on the cellulose component. Finally, the liquor is made alkaline for reaction with the cellulose fiber. Dyes (e.g., with MTC anchor) that dye PA from a neutral liquor in the presence of salt are applied in a two-step process, as in the case of cellulose. In the reversal of this dyeing process, the cellulose component is dyed first at alkaline pH, followed by neutralization with acid, and the PA component is then covered at elevated temperature. 

Thermosol Process. The most important continuous dyeing process for PES fibers is the thermo sol process. It is applied primarily to PES-CEL blends (see Section 4.12.4). The thermosol process consists of four individual steps (1) Padding of the dye liquor on the fabric, (2) Drying, (3) Fixing of the dyes in the fiber, (4) Aftertreatment. The four individual steps usually follow one another in one pass. Systems also exist that include the subsequent overdyeing of the cellulose component in blended fabrics [e.g., by using the pad steam technique (see Section 4.1.1)]. 

After the dyes are fixed, dyes and auxiliaries that adhere superficially must be washed out, if necessary, by an alkaline reductive treatment. In the case of PES-CEL fiber blends, this washing can be combined conveniendy with afterdyeing of the cellulose component, e.g., simply by overdyeing with vat dyes (see Section 4.4.3). For details of the thermosol process, see [85, pp. 122-131],... 

The most important fiber blends consist of polyester and cellulose fibers or wool. Of the worldwide consumption of PES fibers, ca. 45 % is used in blends with cellulose fibers. In polyester-cellulose blends the cellulose component is usually cotton or viscose staple fibers The preferred mixing ratio is PES CEL 67 33 and, for textiles worn close to the skin, 50 50 to 20 80. 

Only one class of dyes is also needed when small molecular vat dyes are used. Fast dyeings are obtained in lighter shades. Padding and the thermo sol process are, if necessary, followed by vatting and normal aftertreatment to improve fastness on the cellulose component. 

PAC-CEL mixtures can also be dyed in a one-bath, two-step process with reactiveand cationic dyes. Here, too, the PAC component is predyed at pH 5 with cationic dyes, and after the pH is raised, the cellulose component is covered with reactive dyes. For the dyeing of yam, see [179],... 

Lignin was also supposed to cause steric hindrance to cellulases during softwood hydrolysis (Ramos et al., 1992 Mooney et al., 1998, 1999) due to encapsulation of the cellulose component so that the cellulose is less accessible to the biocatalyst (Fan et al., 1980). 

The surface of crystallites also represents a portion of the cellulose component readily accessible to chemical agents. Thus, the nature of crystallite surface along with crystallinity influences the apparent accessibility of cellulose, especially when measured by chemical reactions. Among major polymorphs, cellulose I and II are most important in cellulose reactions. 

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