Abstract: Masked isocyanates in which the isocyanate group or groups may be generated by heating above 100.degree. C are formed by tetrazolinones and bis(tetrazolinones) corresponding to the formula : ##STR1## wherein X is hydrogen, halogen, nitro, alkyl (1-4 C) or a group of formula: ##STR2## and R is an aliphatic, aromatic or araliphatic hydrocarbon radical. The bis(tetrazolinones) may be utilized to crosslink upon heating polymers containing active hydrogen atoms. The heating may occur image-wise or record-wise so that layers composed of mixtures of polymers and bis(tetrazolinones) can be used as heat-sensitive recording materials.

Abstract: Carboxylated polyethylenimines are prepared by dissolving in an inert solvent a compound of formula: ##STR1## wherein: R represents an alkyl or an aryl group,Each of R', R", and R'" represents hydrogen or methyl, andR.sup.iv represents an alkyl group.The solution is then treated between -30.degree. and 25.degree. C with a polymerization initiator. After hydrolysis the polymer yields a polyamino acid which is an amphoteric product. They may be added as plasticizers to gelatin in photographic layers.

Abstract: Linear photochrome polycondensates of the polyester type are described which contain spiropyran photochromic groups as an integral part of the main polymer chain, have a glass transition temperature lower than 120.degree. C and possess photochromic properties at or above their glass transition temperature.Manufacture of stabilized photochromic images by exposing a layer of the photochromic polycondensate at a temperature at least equal to the glass transition temperature of the photochromic polycondensate and immediately cooling the thus exposed layer below the glass transition temperature.