Polyisocyanates containing allophanate groups

US5672736A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Martin Brahm · Siegen, DE
• Lutz Schmalstieg · Neunburg vorm Wald, DE
• Josef Pedain · Cologne, DE

Key dates

• Filing date: Nov 8, 1995
• Grant date: Sep 30, 1997
• Expiry date: Nov 8, 2015

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C275/60
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The present invention relates to a process for preparing polyisocyanates containing allophanate groups by reacting compounds a), which PA1 i) contain urethane groups, but which are substantially free of hydroxyl groups and isocyanate groups, PA1 ii) have an average of at least two urethane groups per molecule, PA1 iii) are prepared by reacting organic isocyanates a1) with organic hydroxyl compounds a2) and PA1 iv) have an average molecular weight of at most 2,500, with excess quantities, based on the urethane groups, of distillable organic polyisocyanates b) to form polyisocyanates containing allophanate groups and subsequently removing by distillation the unreacted excess of component b) to a residual content of less than 0.5 wt. %, provided that polyisocyanates a1) and polyisocyanates b) are different. The present invention also relates to the products obtained from this process and to their use as binders or binder components in coating compositions.