Method for preventing hardener compounds to be formed from hardener precursors and extending shelf life of the dispersion

A method for preparing a paint forming dispersion having extended shelf life, into a sealed and pressurized aerosol can, said dispersion preventing hardener compounds to be formed from hardener precursors, said method comprising:

• bringing into said can a paint forming dispersion which contains after sealing the can:
• liquefied propellant, polyurethane resins of an amount W2, epoxy resins of an amount W4, hardener precursor of an amount W3 of said polyurethane resins, hardener precursors of said epoxy resins of an amount W5 and ketones;
• and
• wherein free water of amount W1, which amount W1 is a range of 1-10000 ppm, is brought into said can alongside with said other paint dispersion forming chemicals before sealing the can;
• and
• wherein said polyurethane hardener precursors and epoxy hardener precursors are selected from an imine, an enamine, a Mannich base, a Schiff's base, an oxazole, an oxazolidine, an aldimine, and mixtures thereof, wherein
• polyurethane resins are selected from a group comprising of MDI, HDI, IPDI, TDI, and phenol blocked TDI prepolymers, wherein
• the paint forming dispersion further contains a weak acid, as a catalyst, to prevent formation of the polyurethane hardeners from said polyurethane hardener precursors and the formation of epoxy hardeners from said epoxy hardener precursors, wherein said polyurethane hardener is a compound with at least amine and possibly also a hydroxyl functionality and epoxy hardener is a compound with amine functionality,
• the weak acid (XCOOH), selected from a group having a pKa value in a range from 1.2 to 9, and the amount of said weak acid being in a range of 0.01-10% (w/w) of the dispersion and is adjusted so, that it catalyzes the reaction (2;
• 2a2), by shifting of the equilibrium of reversible reaction (2;
• 2a2) between the free water present in said dispersion and polyurethane hardener and epoxy hardener back to formation of said initial polyurethane hardener precursors and epoxy hardener precursors, in alternative pathways A or B:
• wherein said reversible reaction (2a;
• 2a2) takes place during the entire retention time of the dispersion in the sealed can so that the amount of free water is unchanged and remains between 1-10000 ppm, between two successive uses of the can.