Curable epoxy-based multilayer coatings on substrates using a polythiol and methods of forming the same

Abstract

This disclosure describes a multilayer coating comprising: (I) a substrate, (II) an epoxy primer layer, and (III) an optional, but preferably colored, acrylic topcoat layer, wherein the epoxy primer layer (II) is formed by curing a curable composition comprising: (a) an epoxy-containing compound, at least partially aromatic, and at least 90% bifunctional based on the total weight of all epoxy-containing compounds; (b) a substantially ester-free curing agent comprising a polythiol having at least three thiohydric groups and comprising a cyclic isocyanurate ring structure having three nitrogen atoms and three carbon atoms, wherein at least two of the three cyclic nitrogen atoms have a side chain group containing 2 to 8 carbon atoms and a thiohydric group; and (c) a curing-enhancing catalyst. Methods for preparing multilayer coatings and desired properties of individual layers and / or multilayer coatings are described herein. The present disclosure describes a multilayer coating comprising (I) a substrate, (II) an epoxy-based primer layer, and (III) an optionally but preferably pigmented acrylic topcoat layer, wherein the epoxy-based primer layer (II) is made by curing a curable composition comprising: (a) an epoxy-containing compound that is at least partially aromatic and is at least 90% difunctional, based on the total weight of all epoxy-containing compounds; (b) a substantially ester-free curing agent comprising a polythiol having at least three sulfhydryl moieties and comprising a cyclic isocyanurate ring structure containing 3 nitrogen atoms and 3 carbon atoms, with at least 2 of the three ring nitrogens having a pendant group containing from 2 to 8 carbon atoms and a sulfhydryl moiety; and (c) a curing enhancement catalyst. Methods of making the multilayer coatings are described herein, as well as desirable characteristics of the layers and / or the multilayer coating.

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