Abstract: A composition for photosensitive flexographic plates which is capable of forming a sheet having a smooth surface and excellent antiflowing properties and less apt to have trouble caused by sticking and which further has excellent thin-line reproducibility; a block copolymer composition for photosensitive flexographic plates which is suitable for use in the composition; and a flexographic plate obtained by exposing the composition to light. Also provided are: a block copolymer composition containing a three-branched aromatic vinyl/conjugated diene block copolymer obtained with a specific coupling agent; and a composition for photosensitive flexographic plates which comprises an ethylenic compound and a photopolymerization initiator.

Abstract: A composition for photosensitive flexographic plates which is capable of forming a sheet having a smooth surface and excellent antiflowing properties and less apt to have trouble caused by sticking and which further has excellent thin-line reproducibility; a block copolymer composition for photosensitive flexographic plates which is suitable for use in the composition; and a flexographic plate obtained by exposing the composition to light. Also provided are: a block copolymer composition containing a three-branched aromatic vinyl/conjugated diene block copolymer obtained with a specific coupling agent; and a composition for photosensitive flexographic plates which comprises an ethylenic compound and a photopolymerization initiator.

Abstract: An aromatic vinyl compound-isoprene block copolymer composition comprising (i) 5-50 wt. % a branched copolymer of the formula: (A-B)nX wherein A is a polymer block of an aromatic vinyl monomer, B is a polymer block of isoprene, and X is a residue of a polyfunctional coupling agent, and (ii) 50-95 wt. % of a diblock copolymer of the formula: A-B wherein A and B are as defined above. This copolymer composition is produced by allowing an aromatic vinyl monomer to contact with an organic lithium initiator to prepare a polymer block A; incorporating isoprene thereto to prepare a diblock copolymer A-B; and then, adding a polyfunctional coupling agent to convert a part of the diblock copolymer A-B to the branched copolymer (A-B)nX. This block copolymer composition is useful for an adhesive or pressure sensitive adhesive composition.

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: 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.