Aqueous cross-linking compositions and methods

A method of coating a surface, which consists essentially of:

• applying a water-borne polymeric composition to a surface, the composition comprising an aqueous polymeric dispersion including water, one or more polymers for coalescence or drying into polymer solids when applied to a surface, a cross-linking agent, a blocked cross-linking agent comprising at least one hydrazone group, and ketone or aldehyde, the blocked cross-linking agent being the reaction product of the ketone or aldehyde with the cross-linking agent;
• in which composition, prior to being applied to the surface, an equilibrium is established such that the amount of the cross-linking agent is greater than 0% and less than or equal to 3% in said water-borne composition;
• wherein at least one of the polymers comprises one or more carbonyl groups, one or more epoxy groups both one or more carbonyl groups and one or more epoxy groups, and said cross-linking agent is reactive with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups;
• and
• after said composition's application to the surface subjecting said composition to conditions inducing a reduction of the amount of ketone or aldehyde which causes a shift toward production of the cross-linking agent and a resultant completion of its reaction with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups, to yield a cross-linked water-resistant scrubable polymeric material.

A water-borne composition suitable for application to a surface, which consists essentially of:

• water;
• at least one polymer for coalescence or drying into polymer solids, each said polymer having functionality capable of reacting with a cross-linking agent wherein said functionality is one or more carbonyl groups, one or more epoxy groups, or both one or more carbonyl groups and one or more epoxy groups;
• and
• a cross-linking agent capable of reacting with said functionality, and a blocked cross-linking agent having at least one hydrazone group that is not capable of reacting with any carbonyl or epoxy groups of the polymer but is convertible to an alternate functional group to provide the cross-linking agent which is capable of reacting with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups;
• the composition further comprising ketone or aldehyde, the blocked cross-linking agent being the reaction product of the ketone or aldehyde with the cross-linking agent;
• in which composition, before its application to the surface, a reversible reaction of said blocked cross-linking agent produces said ketone or aldehyde and said cross-linking agent, with the reaction being at equilibrium such that the amount of the cross-linking agent is greater than 0% and less than or equal to 3% in the water-borne composition;
• said reversible reaction being such that after said composition's application to the surface a reduction of the amount of ketone or aldehyde causes a shift toward the production of the cross-linking agent and a resultant completion of its reaction with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups, to yield a cross-linked water-resistant scrubable polymeric material.

A water-borne primer latex, which consists essentially of:

• water;
• a plurality of polymers for coalescence or drying into polymeric solids, each said polymer having a number average molecular weight less than 100,000 Daltons, and a glass transition temperature less than 10° C., and each said polymer comprising one or more carbonyl groups, one or more epoxy groups, or both one or more carbonyl groups and one or more epoxy groups:
• and
• a cross-linking agent which reacts with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups, a blocked cross-linking agent having at least one hydrazone group incorporated therein, and ketone or aldehyde, the blocked cross-linking agent being the reaction product of the ketone or aldehyde with the cross-linking agent;
• in which latex, before application to the surface, a reversible reaction of said blocked cross-linking agent produces said ketone or aldehyde and said cross-linking agent, with the reaction being at equilibrium such that the amount of the cross-linking agent is greater than 0% and less than or equal to 3% in the water-borne composition;
• said reversible reaction being such that after said latex's application to the surface a reduction of the amount of ketone or aldehyde causes a shift toward the production of the cross-linking agent and a resultant completion of its reaction with said carbonyl or epoxy groups or with both said carbonyl and epoxy groups, to yield a cross-linked water-resistant scrubable polymeric material.