Prehump in the gel-permeation chromatography fractionation of pulp cellulose acetate

✍ Scribed by Tanghe, L. J. ;Rebel, W. J. ;Brewer, R. J.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1970
• Tongue: English
• Weight: 576 KB
• Volume: 8
• Category: Article
• ISSN: 0449-296X
• DOI: 10.1002/pol.1970.150081018

✦ Synopsis

Abstract

GPC chromatograms of cellulose acetate made from wood pulp customarily show a shoulder or small separate peak at the high end of the DP distribution. Material isolated from this “prehump” area is considerably enriched in mannose and xylose, and the size of the prehump in acetates from different pulps correlates with the amount of hemicellulose in the pulp. Prehump is not ordinarily found in cellulose acetate made from linters but was induced by adding mannan at the start of the acetylation, or by prolonging the acetylation beyond the time when the cellulose acetate sulfate triester is first formed. Products of poor solubility, as indicated by increased haze and false viscosity, resulted in both cases. Prehump was reduced in pulp cellulose acetate by many of the steps which give products of improved solubility: mercerization of cellulose prior to acetylation, use of more sulfuric acid catalyst, replacement of part of the acetic acid with methylene chloride during acetylation, and by removal of a small amount of high viscosity or poorly soluble material by fractional precipitation.