Pulps, acetylation grade

On the other hand, certain types of wood pulp, prepared by se((uences involving both acidic and alkaline treatments, show a linear relationship between gamma-cellulose and non-cellulosic polyoses. This may be illus-strated from the studies of White, Steinman and Work on acetylation pulps. Acetylation-grade pulps are usually prepared from softwoods by sulfite cooking followed by hot-caustic refining. When the total polyose content of a number of such pulps was compared with their gamma-cellulose content, a linear relationship was obtained (see Fig. 3). In spite of this excellent correlation, it cannot be assumed that all of the non-cellulosic polyoses are contained in the gamma fraction of these pulps (see below). 

Activation of Cellulose. The activation required depends on the source of cellulose (cotton linter or wood pulp), purity, and drying history. Typical specifications for an acetylation-grade cellulose are given in Table 5. Cellulose that has never been dried or has been mildly dried to ca 5% moisture requires Htde, if any, further activation. 

Table 5. Typical Specifications for Acetylation-Grade Pulp ...

In order to equate the consumption of lead tetraacetate to the mannan content of the pulp, Steinmann and coworkers analyzed a series of pulps for mannan, by hydrolysis and subsequent precipitation of mannose phenyl-hydrazone. A satisfactory correlation was observed between the two methods. Since this work was restricted to a study of acetylation-grade pulps, which are generally low in mannan, the correlation between consumption of lead tetraacetate and mannan content did not extend beyond 2 % of mannan. Further studies on this method, to determine whether or not it can be applied to less refined pulps, would be of great interest. 

Cotton linters and viscose grade wood pulp were partially acetylated and carboxymethylated. The samples were grafted under the same conditions with acrylamide. Grafting yield and efficiency depend on several factors, such as the kind of pulp, chemical and physical structure, type of the introduced substituent, and degree of substitution (DS). 

The wood species and the type of pulp manufacturing process relate to the reactivity of the cellulose in acetylation. For example, a highly purified acetate-grade wood pulp from hardwoods manufactured by the prehydrolyzed kraft (PHK) process has about the highest reactivity. Within the category of softwood pulps, there are different levels of reactivity depending on the wood species and the extent of purification. The importance of cellulose... 

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