Abstract: Photopolymerizable water-soluble or water-dispersible mixtures essentially consist of a base polymer, at least one polymerizable ethylenically unsaturated compound, at least one photoinitiator and/or photosensitizer and at least one stabilizer, the thermal polymerization inhibitor being a water-soluble salt of nitrous acid.

Abstract: Photosensitive recording materials which are suitable for the production of printing plates and relief plates and possess a photopolymerizable relief-forming layer which can be developed with water and is based on a polyvinylalcohol/monomer mixture contain, as a binder in the said layer, a polyvinylalcohol derivative which is obtained by reacting polyvinylalcohol with an acylating agent which has groups which are polymerizable by free radicals, the reaction being carried out in the heterogeneous phase, in an aprotic dispersant, using the acylating agent in an amount which corresponds to not less than twice the molar amount required to achieve the desired degree of acylation.

Abstract: A sheet-like structure is produced from a vinyl alcohol polymer by a method wherein, in a self-cleaning multi-screw extruder, the polymer is mixed with a small amount of water, the mixture is melted, homogenized, devolatilized and finally extruded as a melt, and the extrudate is shaped in a conventional manner into the sheet-like structure.

Abstract: Multi-layer photopolymer elements, which are suitable for the production of relief printing plates and contain photosensitive polyvinyl alcohol/monomer layers which can be developed with water, can be improved in respect of their production, drying and shelf life by the application of a thin layer of a highly hydrolyzed low molecular weight polyvinyl alcohol.

Abstract: Acylphosphine oxides of the general formula ##STR1## where R.sup.1 is methyl or ethyl, R.sup.2 is a branched or straight-chain alkyl radical or chlorine, alkoxy or hydrogen, R.sup.3 and R.sup.4 are identical or different, and are each alkyl, alkoxy, alkylthio or chlorine and R.sup.5 is hydrogen, chlorine, alkoxy, alkylthio or alkyl, may be used as photoinitiators in photopolymerizable materials.

Abstract: A photopolymerizable recording composition which comprises a mixture, containing a photoinitiator, of (a) a photopolymerizable olefinically unsaturated monomer and (b) an organic polymeric binder, wherein the photoinitiator is an acylphosphine oxide compound of the formula R.sup.1 R.sup.2 PO--CO--R.sup.3, where R.sup.1 and R.sup.2 are certain organic radicals and R.sup.3 is tert.-alkyl or a cyclic radical with two substituents in the ortho-position to the carbonyl group. The recording compositions have a high reactivity when irradiated with UV light and are used in particular for the preparation of printing plates, relief plates and photo-resists.

Abstract: A process for underlaying flat-bed steel rule dies prior to producing sheet-like geometrical cut blanks, preferably from multi-blank sheets, in which varying tolerances, in the punching and cutting direction, of the steel rule cutters held in a rigid plate are compensated by a sheet, corresponding to the area of the sheet being cut, placed on the back of the steel rule cutter plate and consisting of a flowable hardenable plastic, the upper and lower platen being moved together so as to close the die and the sheet of plastic, bearing the relief formed thereon, then being solidified by an after-treatment.

Abstract: A photopolymerizable recording composition which comprises a mixture, containing a photoinitiator, of (a) a photopolymerizable olefinically unsaturated monomer and (b) an organic polymeric binder, wherein the photoinitiator is an acylphosphine oxide compound of the formula R.sup.1 R.sup.2 PO-CO-R.sup.3, where R.sup.1 and R.sup.2 are certain organic radicals and R.sup.3 is tert.-alkyl or a cyclic radical with two substituents in the ortho-position to the carbonyl group. The recording compositions have a high reactivity when irradiated with UV light and are used in particular for the preparation of printing plates, relief plates and photoresists.

Abstract: A photopolymerizable composition for the production of water-developable printing plates and relief plates, based on a water-soluble or water-dispersible mixture, containing a photoinitiator, of(a) one or more water-soluble or water-dispersible polymers containing copolymerized N-vinylpyrrolidone units and/or one or more polymers containing vinyl alcohol units and(b) one or more olefinically unsaturated photopolymerizable monomers,which comprises, as an additive or as the sole polymer, a water-soluble modified vinyl alcohol polymer which contains from 5 to 75, especially from 10 to 60, % by weight of chemically bonded oxyethylene units. These modified vinyl alcohol polymers are in particular oxyethylated polyvinyl alcohol or hydrolyzed graft polymers of vinyl esters onto polyethylene glycols. The compositions are easier to process into printing plates and relief plates, and exhibit a long shelf life.