Patent ID: 6797752
Filing Date: 2004-09-28
Classification: D21H

Abstract:
A method of whitening paper, which comprises applying to paper a paper coating composition containing a whitening pigment comprising(a) a melamine-formaldehyde or phenol-formaldehyde polycondensation product and (b) a water-soluble fluorescent whitening agent of formula whereinR1 and R2 are each independently of the other â€”OH, â€”Cl, â€”NH2, â€”Oâ€”C1-C4alkyl, â€”Oâ€”aryl, â€”NHâ€”C1-C4alkyl, â€”N(C1-C4alkyl)2, â€”N(C1-C4alkyl)(C1-C4hydroxyalkyl), â€”N(C1-C4hydroxyalkyl)2 -NHâ€”aryl, morpholino, Sâ€”C1-C4alkyl(aryl), or a radical of an amino acid, which radical is substituted at the amino group, and M is hydrogen; sodium; potassium; calcium; magnesium; ammonium; mono-, di-, tri- or tetra-C1-C4alkylammonium; mono-, di- or tri-C1-C4hydroxyalkylammonium; or ammonium di- or tri-substituted by a mixture of C1-C4alkyl and C1-C4hydroxyalkyl groups.