Catonic urea/formaldehyde resins, their preparation and their use in the paper industry

US5554718A · kind A · utility

Assignee

• BASF SE

Inventors

• Klaus Flory · Leimen, DE
• Andreas Stange · Mannheim, DE
• Michael Kroener · Mannheim, DE
• Norbert Sendhoff · Havelsee, DE

Key dates

• Filing date: Nov 6, 1991
• Grant date: Sep 10, 1996
• Expiry date: Nov 6, 2011

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/31964
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

Cationic urea/formaldehyde resins are obtainable by condensing urea and formaldehyde in a molar ratio of from 1:1.5 to 1:3 in the presence of polymers which contain not less than 1 mol % of polymerized vinylamine units and have Fikentscher K values of from 5 to 300, in an amount of from 5 to 50 g per mole of urea in the end product, where the mixture is first a) precondensed at a pH of from 8 to 14, then acidified and b) condensed at a pH of from 1 to 5 until gel formation begins, c) then from 0.3 to 1.5 moles of formaldehyde are added per mole of urea used, d) post-condensation is carried out and e) the resin solution is subsequently neutralized. The resins thus obtained are used in papermaking as assistants for increasing the dry and wet strength of paper and result in less dulling of the whiteness of the paper.