Polybutene/liquid polydiene hot melt adhesive

Abstract

It has been surprisingly found that certain properties including adhesion strength to smooth surfaces may be improved by making hot melt adhesives from blends comprising a poly-1-butene polymer, a tackifier resin, and from 3 wt. % to 25 wt. % of a liquid or semi-liquid, hydrogenated or partially hydrogenated low molecular weight conjugated diene polymer prepared by anionic polymerization. Any one of the following three polymers can be used in the adhesive formulation of this invention: 1) a hydrogenated styrene isoprene diblock copolymer having a number average molecular weight from 4000 to 30,000, preferably 6000 to 15,000, a polystyrene content of 5 to 15 percent by weight, preferably 8 to 12 percent by weight, which is at least 75 percent hydrogenated, preferably at least 85 percent hydrogenated; or 2) a hydrogenated polydiene polymer which may have one diene block of either isoprene or butadiene or maybe a diblock polymer wherein one block is of isoprene and the other block is of butadiene, and wherein the polymer may have a terminal hydroxy group, and wherein the polymer has a number average molecular weight of 500 to 20,000, preferably 1000 to 10,000, and is at least 75 percent hydrogenated, preferably at least 85 percent hydrogenated; or 3) a polyisoprene homopolymer having a number average molecular weight of 15,000 to 40,000, preferably 20,000 to 30,000 which is at least 75 percent hydrogenated, preferably at least 85 percent hydrogenated.