Patent ID: 7223816

Claim:
A hot melt adhesive suitable for bonding a polar leather layer to a non-polar substrate, comprising: (a) a block copolymer having at least one A block and at least one B block, wherein: (i) each A block is a mono alkenyl arene polymer block and each B block is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene; (ii) each A block having an average molecular weight between about 3,000 and about 60,000 and each B block having an average molecular weight between about 30,000 and about 300,000; (iii) each B block comprises terminal regions adjacent to the A block that are rich in conjugated diene units and one or more regions not adjacent to the A blocks that are rich in mono alkenyl arene units; (iv) the total amount of mono alkenyl arene in the block copolymer is about 20 percent weight to about 80 percent weight; (v) the weight percent of mono alkenyl arene in each B block is between about 10 percent and about 75 percent; (vi) the styrene blockiness index of the block B is less than 40 percent, said styrene blockiness index being the proportion of styrene units in the block B having two styrene neighbors on the polymer chain; and wherein the block copolymer has a Young's modulus below 25% elongation of less than 20 MPa and a rubber modulus or slope between 100 and 300% elongation of greater than 0.5 MPa; (b) a hydrogenated hydrocarbon tackifying resin, with a softening point lower than 140° C. in a weight proportion of 30 to 150 parts by weight of tackifying resin per 100 parts per weight of block copolymer; (c) a resin which is compatible with the mono alkenyl arene blocks, having a softening point lower than 140° C., in a weight proportion of from 10 to 80 parts by weight of resin per 100 parts by weight of block copolymer; (d) optionally a melt flow improving poly(alkylene) resin, which is functionalized, in a weight proportion of from 0 to 30 parts by weight per 100 parts by weight of block copolymer, and (e) stabilizers and/or additional auxiliaries in a weight proportion of from 0.1 to 1 part by weight per 100 parts by weight of block copolymer.