Sika Technology Ag

David Hofstetter

Jan Olaf Schulenburg

Christian Krüger

Tina Voci

Johann Ulrich Winteler

An epoxy group-terminated impact modifier is described, comprising the reaction product of a) two or more polyols, b) one or more polyisocyanates, and c) at least one epoxy resin comprising a primary or secondary hydroxy group-containing epoxy compound, wherein the polyols comprise a1) at least one polyether polyol and a2) at least one OH-terminated rubber, wherein the weight ratio of polyether polyol to OH-terminated rubber is in the range from 7:3 to 2:8; an isocyanate-terminated prepolymer as possible intermediate product is described; furthermore a method for producing same is described. The products obtained are suitable for improving the impact resistance of epoxy resin compositions, in particular of 1K or 2K epoxy resin adhesives.

Impact modifiers for epoxy-based adhesives

A method is described for producing liquid rubber containing an impact-resistance modifier terminated by epoxy groups, the method including the reaction of an isocyanate-terminated prepolymer with an epoxy resin, which includes an epoxy compound including a primary or secondary hydroxyl group, in the presence of a compound selected from anhydrides, ketones and aldehydes as glycol scavengers, wherein the isocyanate-terminated prepolymer, the epoxy resin and the glycol scavenger are mixed with one another, or the epoxy resin is reacted with the glycol scavenger, before they are mixed with the isocyanate-terminated prepolymer. Gelling in the reaction mixture is avoided by the method. The resulting products are suitable for improving the impact resistance of epoxy resin compositions, particularly one-component or two-component epoxy resin adhesives.

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Winterthur, Switzerland

David Hofstetter