The Dow Chemical Company

Clayton W Hoornstra

Violete L Stevens

Donald L Schmidt

Demetrius Urchick

William E Broxterman

A negative-working, reversibly gelled composition is disclosed, suitable for use as the photocurable component in a blank for preparation of an article in relief, such as a printing plate. Uncured portions of the composition are removed with an aqueous solution following imagewise modulated exposure of such a blank to actinic radiation. The composition comprises a first organic polymer bearing per molecule, at least one ethylenically unsaturated group which is polymerizable by a free radical source; and a second organic polymer bearing per molecule, at least two Z groups, Z being a primary hydroxyl or mercapto group, with the proviso that when said first organic polymer bears at least two Z groups per molecule, said second organic polymer may be omitted; said Z groups being reacted by contact with a dialdehyde to produce the reversibly gelled composition.

Gelled photopolymer composition for article in relief

AR-Cyclic sulfonium, fused polynuclear areneoxides exemplified by the structural formula: ##STR1## polymerize readily upon exposure to ultraviolet light and/or heat to yield water-insoluble resins useful as adhesives, coatings, films and the like. Fused polynuclear zwitterions containing more than one areneoxide and cyclic sulfonium group per molecule crosslink under such conditions.

Fused poly-nuclear aromatic cyclic sulfonium zwitterions and polymers

A negative-working, reversibly gelled composition is disclosed, suitable for use as the photocurable component in a blank for preparation of an article in relief, such as a printing plate. Uncured portions of the composition are removed with an aqueous solution following imagewise modulated exposure of such a blank to actinic radiation. The composition comprises a first organic polymer bearing per molecule, at least one ethylenically unsaturated group which is polymerizable by a free radical source; and a second organic polymer bearing per molecule, at least two Z groups, Z being a primary hydroxyl or a mercapto group, with the proviso that when said first organic polymer bears at least two Z groups per molecule, said second organic polymer may be omitted; said Z groups being reacted by contact with a dialdehyde to produce the reversibly gelled composition.

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Midland, MI, United States of America

Clayton W Hoornstra