Printing form and process for preparing the printing form with curable composition having solvent-free epoxy resin
The invention pertains to a printing form and a process for preparing the printing form from a solvent-free curable composition that includes, in prescribed relative amounts, an epoxy novolac resin; a bisphenol-A epoxy resin or a bisphenol-F epoxy resin; a monofunctional reactive diluent; a multifunctional reactive diluent; and a stoichiometric amount of an amine curing agent. The ratio of the epoxy novolac resin to the bisphenol epoxy resin is 1:3 to 3:1 by weight. The process includes applying the curable composition to a supporting substrate to form a layer, curing the layer at one or more temperatures in a temperature range, and engraving to form at least one cell in the cured layer. The process prepares printing forms, particularly gravure printing forms, having a cured resin composition layer that is engravable, resistant to solvent inks and to mechanical wear, and capable of printing gravure-quality images.
1. A printing form comprising a continuous print surface adjacent to a supporting substrate, wherein the continuous print surface is a cured epoxy composition prepared from a solvent-free curable composition comprising:
i) an epoxy novolac resin having a softening point less than 60° C.,
ii) a bisphenol-A epoxy resin or a bisphenol-F epoxy resin, having a softening point less than 60° C.,
iii) a monofunctional reactive diluent,
iv) a multifunctional reactive diluent, and
v) a stoichiometric amount of a multifunctional amine curing agent having an amine hydrogen equivalent weight less than 40 g/equivalent; and
wherein i) and ii) together are at least 70 wt % of i), ii), iii), and iv) together; the ratio of i) to ii) is 1:3 to 3:1 by weight; and the ratio of iii) to iv) is 4:1 to 1:4 by weight.
2. The printing form of claim 1 wherein iii) and iv) together are at least 10 wt % of i), ii), iii), and iv) together.
3. The printing form of claim 1 wherein the curable composition further comprises up to 30 wt % nanoparticles.
4. The printing form of claim 1 wherein the curable composition further comprises up to 30 wt % filler.
5. The printing form of claim 1 wherein the printing form is in the shape of a cylinder or plate.
6. The printing form of claim 1 wherein the substrate is metal al or a polymer.
7. The printing form of claim 1 wherein the printing form is a gravure printing cylinder.
8. The printing form of claim 7 wherein the printing form is free of copper and chrome layers.