HIGH STRENGTH, LONG-OPEN TIME STRUCTURAL POLYURETHANE ADHESIVE AND METHOD OF USE THEREOF

摘要

Disclosed is a two-part polyurethane structural adhesive and method of bondi ng structural components, that exhibits at least 25 minutes of open time at 32 ~C in large beads and cures to high strength under ambient conditions. The adhesive composition in one part is an isocyanate or isocyanate prepolymer a nd in a second part is a polyol mixture (I) or (II), wherein 75 % to 100 % by weight of the polyol mixture (I) or (II) are polyols having secondary hydrox yl functionality and the polyol mixture (I) or (II) contains a long chain secondary polyol defined hereinbelow. The polyol mixture in one embodiment i s substantially absent short chain polyols having functionality of 2, and includes an amount from 30 % to 80 % by weight on total polyol weight in (I) of long chain secondary polyol of molecular weight from 200 to 12000 and fro m 20 % to 70 % by weight on total weight of the polyol mixture and of a short chain secondary polyol with functionality greater than 2 and a molecular weight of from 90 to 800. In another embodiment, 5 % to 80 % of a long chain secondary polyol of molecular weight of from 2000 to 12000 is present togeth er with 5 % to 70 % of a short chain secondary polyol having a functionality of greater than 2, and 5 % to 70 % of a short chain secondary polyol having a functionalityof 2 and a molecular weight of from 90-800.