Abstract: Photopolymerizable compositions based on an elastomeric styrene-diene block polymer, one or more photopolymerizable olefinically unsaturated monomers and one or more photopolymerization initiators exhibit improved properties if they contain, as an essential constituent, an elastomeric block copolymer of the general structure A-B-C, where A is a thermoplastic, non-elastomeric polymer block based on styrene compounds and having a second order transition point above +25.degree. C., B is an elastomeric polymer block based on butadiene and/or isoprene and having a second order transition point below -20.degree. C. and C is a polymer block, different from B, having a second order transition point of from -30.degree. C. to +15.degree. C., C being either a homopolymer or copolymer block based on butadiene or isoprene or a random copolymer block based on conjugated dienes and styrene compounds.

Abstract: Laminates for the manufacture of flexographic printing plates and containing (a) a layer consisting essentially of a photocrosslinkable mixture of a two-block copolymer of from 30 to 95% w/w of a diene hydrocarbon and from 5 to 70% w/w of a styrene monomer or a partially hydrogenated product thereof with a compatible monomer having at least one C--C double bond, said mixture containing a photo-initiator, (b) a non-photocrosslinkable elastomeric underlayer having a Shore A hardness of from 15 to 70 and (c) a non-photocrosslinkable stablizing layer preferably between layers (a) and (b).

Abstract: An apparatus for treating photopolymer printing plates, which have already been exposed, with liquid media, in which the plate, mounted on a vertically movable holder, can be moved up and down between an upper loading and unloading chamber and a lower treatment chamber, separated from the upper chamber by a partially open partition, and in which upper and lower rim elements of the plate holder seal the aperture in the partition in a vapor-tight manner when the plate holder is in its terminal positions.

Abstract: A process for the manufacture of thin layers based on polyurethane elastomers. A liquid reaction mixture essentially consisting of (A) polyesters, polyethers, polyester urethanes or polyether urethanes, all of which contain at least two hydroxyl groups in the molecule, and diisocyanates or (B) prepolymers obtained from the hydroxyl-containing compounds mentioned under (A) above with an excess of diisocyanates, said prepolymers containing at least two isocyanate groups in the molecule, and at least one of the compounds mentioned under (A) above which are capable of reacting with isocyanates, to which reaction mixture a minor quantity of substantially compatible monomers having at least two photocrosslinkable C--C multiple bonds and optionally a photopolymerization initiator have been added, is applied to a substrate to form a coating thereon, which coating is then gelled by irradiation and finally thermocured.

Abstract: Photosensitive compositions based on soluble vinylpyrrolidone polymers, soluble or swellable polycarboxylic acids, photopolymerizable olefinically unsaturated monomers and optional additions of photoinitiators and polymerization inhibitors.The photosensitive compositions of the invention are suitable for the preparation of printing plates, particularly lithographic plates.

Abstract: The invention relates to relief plates for flexographic printing comprising a relatively soft elastomeric base (U) having a modulus of elasticity of from 10 to 200 kg/cm.sup.2 and a thickness of from 0.5 to 6 mm and, firmly bonded thereto, a thin, relatively hard, difficultly soluble intermediate layer Z having a modulus of elasticity of from 1 .times. 10.sup.3 to 2.1 .times. 10.sup.6 kg/cm.sup.2 and a thickness of from 5 to 500 .mu. and, firmly bonded to said intermediate layer Z, a relief layer P' consisting of a photocrosslinked elastomeric mixture having a modulus of elasticity of from 30 to 2000 kg/cm.sup.2 and a thickness of from 200 to 300 .mu., the modulus of elasticity of the photocrosslinked relief layer P' being the same as or higher than that of the base U and the neutral surface of the relief plate lying in or near the intermediate layer Z. The invention also relates to photosensitive laminates for the production of such plates.

Abstract: Laminates for the production of relief plates for flexographic printing, by imagewise exposure and washing out with a developer solution have, on a base optionally provided with an elastomeric layer, a photo-crosslinkable layer containing a photoinitiator and consisting of a polyurethane elastomer which has been prepared in a special manner from an aliphatic saturated polyesterglycol, an aliphatic diisocyanate, but-1-ene-3,4-diol and, if desired, another diol and which has a Shore A hardness of 30 to 90.degree. in the photo-crosslinked state, the elastomer being optionally mixed with a photo-crosslinked monomer.