Abstract: The esters are soluble in an aqueous solution of a base before exposure to actinic radiation but, on exposure to actinic radiation, polymerize and become insoluble in such an aqueous solution. Development of photopolymerized images does not therefore require the use of toxic or flammable organic solvents. They contain free carboxyl groups and at least one unit of the formulae I-IV ##STR1## where R.sup.1 is a carbon atom chain containing specified groupings, such as one of formula --CH.dbd.CH--CO--CH.dbd.CH--, --CH.dbd.CHCO--, --COCH.dbd.CHC.sub.6 H.sub.4 CH.dbd.CHCO--, or ##STR2## and Y is oxygen or sulfur. They are obtained by the reaction of an at least dianhydride of a polycarboxylic acid with alcoholic hydroxyl groups of an alcohol containing at least one unit of formula I-IV.

Abstract: The products, which are based on polyepoxides, polymerize on exposure to actinic radiation and are useful in the preparation of printing plates for offset printing and of printed circuits, particularly multilayer circuits. They are formed by coupling two molecules of a polyepoxide by means of a dihydric phenol which contains a chalcone or chalcone-like grouping, such as 1,3-bis(p-hydroxyphenyl)prop-1-en-3-one or 1,5-bis(p-hydroxyphenyl)penta-1,4-dien-3-one, so sensitizing the material to the radiation, and then, to achieve polymerizability, ring-opening at least some of the residual epoxide groups so as to incorporate olefinic acyloxy groups (R.sup.6 CH.dbd.C(R.sup.5)COO--), such as sorboyl groups.

Abstract: Diepoxides which may be photopolymerized in the presence or absence of a photosensitizer contain a group having conjugated unsaturation attached to a nitrogen heterocycle, such as a hydantoin or barbituric acid residue, forming part of an advanced diepoxide. The resultant photopolymer may be crosslinked by heating in the presence of a curing agent for epoxide resins.The diepoxides are of use in the production of printing plates and printed circuits, especially multilayer printed circuits.

Abstract: Epoxide resins, which polymerize on exposure to actinic radiation, have, per average molecule, at least two photopolymerizable groups and also at least two 1,2-epoxide groups, one or more such epoxide groups being contained in units of formula ##STR1## Photopolymerizable epoxide resins are commonly prepared by introduction of photopolymerizable groups into a molecule of an epoxide resin by reaction with some of the epoxide groups: the modified resin, having a low epoxide group content, usually exhibits poorer adhesion and lower glass transition temperature than would otherwise be the case. In the new resins, secondary hydroxyl groups generated on introduction of the photopolymerizable groups have been converted into glycidyl ether groups, thus they have a higher epoxide content.

Abstract: A non-stretchable reinforcing cord is wound in a helical groove in a collapsible, cylindrical metal mandrel, and the cord is then tensioned and attached to the mandrel. The mandrel, with cord is placed in an outer mold element having a complementary cylindrical mold cavity, and a curable elastomer is injection molded into the mold space between the mandrel and cavity to mold an endless belt therebetween, and to fill the helical groove and transverse slots in the mandrel so as to form spaced parallel lugs along the inner surface of the belt, in which adjacent portions of the reinforcing cord are completely embedded, the cord being partially exposed in the spaces between lugs. The elastomer is then cured, and the mandrel collapsed to permit removal of the molded belt.