ENHANCED BRIGHTNESS AND BRIGHTNESS STABILITY OF LIGNOCELLULOSIC MATERIALS

摘要

The present invention provides a method for the production of lignocellulosic materials, in particular, lignin-containing or lignin-free papers or paperboards, with a higher and more stable brightness. The enhanced brightness and brightness stability is achieved using pigmented coatings that also contain a water-soluble phosphine or phosphonium compound possessing at least one phosphorus hydroxymethyl bond/linkage. The pigments can also be pretreated with the phosphine or phosphonium compounds before addition as a filler or preparation of the coating colour. One example of such a water-soluble phosphine is tris(hydroxymethyl)phosphine (THP), P(CH2OH)3. One example of such a phosphonium compound is tetrakis(hydroxymethyl)phosphonium sulfate (THPS), [P(CH2OH)4]2SO4. There is a synergy between THPS and the pigment on the brightness gain and on the brightness/light stabilization of the papers or paperboards coated or filled with the pigment.