KATIONISCHE HARNSTOFF-FORMALDEHYD-HARZE, VERFAHREN ZU IHRER HERSTELLUNG UND IHRE VERWENDUNG IN DER PAPIERINDUSTRIE

摘要

Cationic urea formaldehyde resins are obtained by condensation of urea and formaldehyde in a molar ratio of 1:1.5 to 3 in the presence of at least 1 mol% of polymerizates, obtained by polymerization of vinyl amine units, with Fikentscher K values of 5 to 300 in a quantity of 5 to 100 g/mol of urea in the end-product. The mixture is first a) precondensed at a pH of 8 to 14, then acidified and b) condensed at a pH of 1 to 5 until the onset of gel formation, c) 0.3 to 1.5 mol of formaldehyde per mol of urea used is added, d) subsequent condensation is carried out and e) the resin solution is then neutralized. The resins so obtained are used as additives in paper manufacture to increase the dry and wet strength of paper and reduce the loss of opacity of the whiteness of the paper.