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

摘要

Lignin-containing fibrous materials, in particular paper and card, are treated with whiteness stabilizers for the purpose of reducing light-induced yellowing. The whiteness stabilizer are (i) thiols with at least one additional hydrophilic group from the series consisting of OH, NH₂, NHR¹m NR¹R², COOH, SO₃H and PO₃H₂ and an amino acid/peptide structure (ii) thiols with a CC double bond (iii) or heteroaromatic thiols and (iv), heteroaromatic disulfides or polysulfides. HALS light stabilizers and/or UV stabilizers are advantageously additionally employed. The stability is increased further by a TiO₂-containing coat on the fibrous material. Stabilzer compositions and fibrous material stabilized according to the invention, containing a whiteness stabilizer of group (i) to (iv) are also disclosed.