Pressure-sensitive polyurethane adhesive for sensitive surfaces

摘要

A polyurethane based adhesive composition is prepared by catalytic reaction of at least one aliphatic or alicyclic polyisocyanate having a functionality of no greater than 3 and a combination of at least one polypropylene glycol diol and at least one polypropylene glycol triol. A polyurethane based adhesive composition (I) is prepared by catalytic reaction of at least one aliphatic or alicyclic polyisocyanate having a functionality of no greater than 3 and a combination of at least one polypropylene glycol diol and at least one polypropylene glycol triol whereby the ratio of the number of hydroxyl groups of the diol component to the number of hydroxyl groups of the triol component is less than 10, preferably 0.5-5 and the number of isocyanate groups to the total number of hydroxyl groups is 0.8-1.15 (1.0-1.05) whereby the catalyst is a bismuth carboxylate or corresponding derivative and whereby the diol and triol are combined as diols having a mol. wt. of no greater than 1000 with triols having a mol. wt. of at least 1000, preferably at least 3000 or as diols having a mol. wt. of greater than 1000 combined with triols having a mol. wt. of less than 1000. An independent claim is included for a process for the production of the adhesive composition (I) comprising placing a premixed mixture of isocyante-reactive material (polyol component) in a vessel with the isocyante component in a separate vessel optionally premixed with other components; dosing of both components via precision pumps through a mixing head or tube to form a homogeneous mixture ; immediate application of the mixed and reacted components onto a sheet-like support material having a second adhesive layer at a constant rate; passage of the coated support material through a heated channel to harden the polyurethane composition to form the adhesive; and rolling the coated support material.