Tackified star block copolymer pressure-sensitive adhesive composition and the sheet materials coated therewith

Claim 1

A coated sheet material comprising a backing member and a nornally tacky and pressure-sensitive adhesive composition covering at least a portion of one major surface thereof, said normally tacky and pressure-sensitive adhesive composition having a melt Brookfield viscosity in the range of about 25-100 Pa.s and comprising: (1) star block copolymer having the general formula (A-B) n C wherein: "(A-B)" represents one of "n" polymeric arms, as measured by size exclusion chromatography with low-angle laser light-scattering detection, radiating from a nucleus represented by "C"; "A" represents a terminal polymeric block consiting essentially of polymerized monovinyl aromatic monomer having 8 to 8 carbon atoms and being selected from a group consisting of styrene and alkylated styrene; "B" represents a polymeric block consisting essentially of a polymerized conjugated diene monomer having 4 to 12 carbon atoms; "C" represents the residue of a polyvinyl aromatic compound which provides a nucleus which links together at least 12 polymeric arms of said star block copolymer; and "n" is an interger of at least 12; and wherein: "A" comprises about 5-25 weight percent of the total weight of A plus B in said polymer; "B" comprises about 75 to 95 weight percent of the total weight of A plus B in said polymer; and "C" comprises no more than about 3 weight percent of the total weight of said star block copolymer; and (2) sufficient adhesive tackifier resin to maintain in said adhesive composition a balance of pressure-sensitive adhesive properties wherein the shear holding power is at least 1,000 minutes.