Page 297 - Advances in Textile Biotechnology

278 Advances in textile biotechnology

(a)
White light

(b)
UV light

11.5 An example of the use of the XET/XG method to retain an optical
brightening agent on chemical wood pulp handsheets. Pulps were
treated with six different amounts of XG-OBA and formed into sheets.
Irradiation with ultraviolet light (b) shows a clear dose-dependent UV
brightening effect, which is not observed under normal laboratory
fluorescent tube lighting (a).

XG–NH 2 have been reacted with a number of electrophiles, including iso-
cyanates, isothiocyanates, thioesters, and activated carboxylic acids (Brumer
et al., 2004; Teeri and Brumer, 2003). For example, XG–NH 2 -modifi ed
Whatman No. 1 fi lter paper can be reacted with FITC to yield paper effec-
tively identical to that from direct XG–FITC modifi cation (Brumer et al.,

2004). Thiol groups on cellulosic fibres, from the adsorption of a thiolated
XG derivative (XG–SH), can be specifically reacted with methanethiosul-

fonate reagents or disulfides in water to form derivatives of the general
structure XG–S—S–R. Subsequently, reduction of the disulfide bond (rep-

resented by the em dash) under gentle, aqueous conditions, can be used to
remove the functional groups with concommitant regeneration of the XG–
SH thiol, which can be re-derivatized (Brumer et al., 2004; Gustavsson

© Woodhead Publishing Limited, 2010