Process for stabilizing the whiteness of lignin- containing fibrous materials, stabilizer composition and fibrous materials stabilized

摘要

A process for stabilizing the whiteness of lignin- containing fibrous materials against light-induced yellowing, comprising the use of a thio compound as a whiteness stabilizer in an active amount for increasing the resistance to yellowing during the production of the fibrous material, wherein a thiol compound from the series consisting of (i) ester of a polyhydric alcohol having a cycloaliphatic, linear or branched hydrocarbon radical with 4 to 20 C-atoms, which radical can be interrupted once or several times by a -O-, -S-, -NH-, or -N(alkyl)- bridge, with a mercaptocarboxylic acid, wherein at least one hydroxyl group of the polyhydric alcohol is non esterified, (I') mercaptoamines containing a cycloaliphatic, linear or branched carbon skeleton, which can be interrupted once or several times by -O-, -S-, -NH-, or -N-alkyl-, at least one NH2, NHR-1 or NR1R2 group, wherein R1 and R2 can be identical or different and can represent a lower alkyl group, hydroxyethyl, hydroxpropyl or dihydroxypropyl with one another or can be boned together, (I'') mercaptoamino acids (ii) thiols which contain at least one aliphatically or cycloaliphatically bonded thiol group and additionally at least on CC double bond, (iii) thiols which contain at least one thiol group bonded to a heteroaromatic group, and (iv) di- and polysulfides with at least one heteroaromatic bonded to the di-/polysulfide group, is employed as the whiteness stabilizer, thioglycerol, dithiotheritol mercaptoacetic acid, 2- and 3- mercaptopropionic acid, and salts thereof being excluded as the whiteness stabilizer.