Abstract: A pressure sensitive adhesive composition comprising (A) 100 parts by weight of a conjugated diene-type rubber, and (B) 30 to 250 parts by weight of a hydrocarbon resin having a softening point of 60.degree. C to 140.degree. C and comprising (a) 45 to 85% by weight of a unit derived from 1,3-pentadiene, (b) 10 to 45% by weight of a unit derived from .alpha.-methylstyrene, (c) 3 to 20% by weight of a unit derived from cyclopentene, (d) 0 to 20% by weight of a unit derived from 1,3-butadiene, and (e) 0 to 5% by weight of a unit derived from a copolymerizable monomer selected from isoprene, cyclopentadiene and dicyclopentadiene.

Abstract: Hydrocarbon resins comprising (a) about 45 to 85% by weight of units derived from 1,3-pentadiene, (b) about 10 to 45% by weight of units derived from .alpha.-methylstyrene, (c) about 3 to 20% by weight of units derived from cyclopentene and (d) 0 to about 20% by weight of units derived from 1,3-butadiene and having a softening point of from about 60.degree. C. to about 140.degree. C., said hydrocarbon resins being prepared by polymerizing a monomeric mixture comprising (a) about 35 to 85% by weight of 1,3-pentadiene, (b) about 10 to 50% by weight of .alpha.-methylstyrene, (c) about 5 to 30% by weight of cyclopentene and (d) 0 to 15% by weight of 1,3-butadiene in a solvent comprising at least 50% by weight of an aromatic hydrocarbon in the presence of an aluminum halide as a catalyst.

Abstract: Hydrocarbon resins comprising about 95-35% by weight of units derived from 1,3-pentadiene, about 1-50% by weight of units derived from cyclododecatriene, and O-about 40% by weight of units derived from at least one monoolefin containing 5 carbon atoms, having a softening point of from about 100.degree. to about 160.degree. C., and being substantially gel-free. The hydrocarbon resins can be prepared by polymerizing a monomeric mixture comprising 1,3-pentadiene in the presence of a Friedel-Crafts type metal halide catalyst, said monomeric mixture comprising about 95-35% by weight of 1,3-pentadiene, about 1-50% by weight of cyclododecatriene, and 0-about 50% by weight of at least one monoolefin containing 5 carbon atoms.