Crosslinkable composition cross-linkable by real Michael addition reaction and resins for use in said composition
An RMA crosslinkable composition having at least one crosslinkable component including reactive components A and B each including at least 2 reactive groups, the at least 2 reactive groups of component A being acidic protons (C—H) in activated methylene or methine groups and the at least 2 reactive groups of component B are activated unsaturated groups (C═C) and a base catalyst (C) which reactive components A and B crosslink by Real Michael Addition (RMA) reaction under action of the base catalyst, characterised in that the at least one crosslinkable component including reactive components A and B in the composition have a total hydroxy number of less than 60, preferably less than 40 and more preferably less than 20 mg KOH/g solids. Further, specific resins A and B having a low hydroxy number for use in RMA cross-linkable compositions and a process for the manufacture thereof.
1. A polymeric or oligomeric resin A, comprising one or more reactive components A having a structure according to formula 1:
wherein R is hydrogen or an alkyl, aralkyl or aryl substituent and Y and Y′ are same or different alkyl, aralkyl or aryl (R*), alkoxy (—OR*) groups or a polymer backbone or wherein the —C(═O)—Y and/or —C(═O)—Y′ is replaced by CN or phenyl,
wherein the polymeric or oligomeric resin A is a polyester, polyether, polyepoxy, polyurethane or polycarbonate, comprising reactive component A,
wherein the resin A is produced by transesterification of a polyester, polyether, polyepoxy, polyurethane, or polycarbonate polyol with an acetoacetate or malonate reactive component A in the form of a carboxylic acid ester,
and wherein the obtained resin A has a hydroxy number of less than 60 mg KOH/g solids, has a number average molecular weight between 100-20000 g/mol, an equivalent weight per reactive component A of 100-2000 g/mol and an acid number less than 4 mg KOH/g.
2. The resin A according to claim 1 , wherein more than 50% of the reactive components A in the polymeric or oligomeric resin A are malonate groups.
3. The resin A according to claim 1 , wherein more than 60% of the reactive components A in the polymeric or oligomeric resin A are malonate groups.
4. The resin A according to claim 1 , comprising an average of 2 to 20 active C—H functions per molecule.
5. The resin A according to claim 1 , comprising an average of 4 to 10 active C—H functions per molecule.
6. The resin A according to claim 1 , having a hydroxy number of less than 40 mg KOH/g solids.
7. The resin A according to claim 1 , comprising both malonate and acetoacetate groups.
8. The resin A according to claim 1 , wherein the polymer or oligomer resin A is produced by transesterification of a polyester polyol.
9. The resin A according to claim 1 , wherein the polymer or oligomer resin A is produced by transesterification of a polyester polyol with esters of malonic acid or ethylacetoacetic acid.
10. The resin A according to claim 8 , wherein the polyester polyol is prepared by reacting a hydroxyl functional polyester polyol with lactone chain extenders or by reacting a polyester bearing both hydroxyl and acid groups with one or more mono- or polyfunctional epoxy compounds.
11. The resin A according to claim 1 , having a glass transition temperature between −25 and +25° C.
12. The resin A according to claim 1 , comprising at most 60 wt. % aromatic constituents.
13. The resin A according to claim 1 , comprising at most 40 or at most 5 wt. % aromatic constituents.