Ambient temperature curable isocyanate-free compositions for preparing crosslinked polyurethanes
The present invention provides a multicomponent composition that is substantially isocyanate-free and comprises a polycarbamate as a first component and a polyaldehyde or an acetal or hemiacetal thereof as a second component and further comprises an effective amount of a triggering agent such that the first and second components to cure at a temperature of from 0C to less than 80C to form a crosslinked polyurethane. The multicomponent composition forms an ambient temperature curable composition when all of its components are combined that has a pH of 7.0 or less. The present invention also provides processes crosslinked polyurethanes, and the crosslinked polyurethanes prepared by the processes.
1. A substantially isocyanate-free and substantially formaldehyde free multicomponent composition comprising a polycarbamate having an average of 2.5 or more carbamate functional groups as a first component and a polyaldehyde, which polyaldehyde is a dialdehyde, a trialdehyde or an acetal or hemiacetal thereof having from 2 to 20 carbon atoms as a second component, wherein the multicomponent composition futher comprises an effective amount of a trigger a gent such that the first and second components when combined form a composition that react to cure at a temperature of from 0° C to less than 80° C to form a crosslinked polyurethane and a curing inhibitor chosen from water, an alcohol or a mixture thereof, and, further wherein, the composition resulting when all components of the multicomponent composition are combined has a pH of 7.0 or less.
2. A substantially isocyanate-free and substantially formaldehyde free multicomponent composition comprising a polycarbamate having an average of 2.5 or more carbamate functional groups as a first component and a polyaldehyde chosen from (cis,trans)-1,4-cyclohexanedicarboxyaldehydes, (cis,trans)-1,3-cyclohexanedicarboxyaldehydes and mixtures thereof as a second component, wherein the multicomponent composition further comprises an effective amount of a triggering agent such that the first and second components when combined form a composition that reacts to cure at a temperature of from 0 C to less than 80° C to form a crosslinked polyurethane, and, further wherein, the composition resulting when all components of the multicomponent composition are combined has a pH of 7.0 or less.
3. The multicomponent composition as in claim 1 , wherein the triggering agent is an acid with a pKa of less than 6.0 or a Lewis Acid.
4. The multicomponent composition as in claim 1 , wherein the polycarbamate is the condensation product of one or more polyols with an unsubstituted carbamic acid alkyl ester or urea.
5. The multicomponent composition as in claim 4 , wherein the polyol is an acrylic, saturated polyester, alkyd, polyether or polycarbonate.
6. The multicomponent composition as in claim 5 , wherein the polycarbamate of the first component has carbamate groups and hydroxyl groups in a ratio of the equivalents of carbamate groups to the number of equivalents of hydroxyl functional groups of from 1:1 to 20:1.
7. The multicomponent composition as claimed in claim 1 , further comprising from 3 to 20 wt.%, based on the total weight of solids in the composition, of a pigment for increasing flexibility, adhesion, or both of a cured and dried coating prepared therefrom.
8. A process for preparing a crosslinked polyurethane comprising mixing a polycarbamate having an average of 2.5 or more carbamate functional groups as a first component and a polyaldehyde, which polyaldehyde is a dialdehyde, a trialdehyde or an acetal or hemiacetal thereof having from 2 to 20 carbon atoms as a second component to form an ambient temperature curable composition having a pH of 7.0 or less, and curing the resulting composition at a temperature of from 0° C to less than 80° C , wherein the ambient temperature curable composition has an effective amount of a triggering agent and has a curing inhibitor chosen from water, an alcohol or a mixture thereof.
9. The crosslinked polyurethane of claim 8 which has at least one geminal bis(urethane) group.