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[0356] Preparing a batch of intermediate product for app 600 aerosol cans of 400 ml 

[0357] Mixing barrel 200 L 

[0358] Following amount are added to the mixing barrel: 

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[0359] After this mixing the product is ready tom be filled in an aerosol can, to be closed with a valve and filled till 400 ml with the liquefied propellant. Above mentioned example was based on following principles: 

[0360] solvents are filled in a barrel paint additives are added the amount water present is defined by taking a sample of water presence with Karl Fisher Method based on the exact amount of water the needed amount of precursor hardener is calculated to react the water away and give a rest amount of precursor hardener that is sufficient to give full hardening of the binder. The precursor hardener is added to the solvent/additive mix and stirred gently for app 2 min. After 20 min a sample is analyzed to check that all the water has reacted is no longer present as water in the mixture. Based on the measured amount of water at the start the precursor hardener over dose is calculated and also gives the amount of rest product (amine containing). 

[0361] The amount carbolic acid needed to react the amine away to an ammonium-carboxylate. After adding the car› bolic acid the mixture is stirred gently for app 10 min. The binders can be added to a water free solvent/additive/ precursor hardener/amino-carboxylate mixture. The free alcohol formed at the hydrolyzing of the precursor hardener will be used as terminator of the highly reactive HDI monomer of the pu binder. After stirring this mixture gently for app 5 min the product is ready to be filled in an aerosol can, closed with a valve and be filled with the propellant 

[0362] In case of colored top coats the colorants will be added to the mixture together with the binders. 

1. A method for preventing hardener compounds to be formed from hardener precursors and extending shelf life of the dispersion in a sealed and pressurized aerosol can comprising a paint forming dispersion which contains after sealing the can: liquefied propellant, polyurethane resins of an amount W2, hardener precursor of said polyurethane resins of an amount W3, 

wherein said polyurethane hardener precursors are selected from the group comprising of an imine, an enamine, a Mannich base, a Schiff’s base, an aldimine, an azole preferable an oxazole such as an oxazolidine and mixtures thereof, 

free water of amount Wl, which amount Wl is in the range of 1-10000 ppm, preferable 1-6000 ppm and brought into said can alongside with said other paint dispersion forming chemicals before sealing the can, characterized thereof, that 

polyurethane resins are selected from the group which composes of MDI, HDI, IPDI, TDI and phenol blocked TDI prepolymers, 

the dispersion contains also ketones, and a weak acid, as a catalyst, to prevent formation of the polyurethane hardeners from said polyurethane hardener precursors, 

the amount of said weak acid in adjusted so, that it catalyzes the reaction (2; 2al) shifting the equilibrium of the reversible reaction (2a;2al ), in alternative path› ways A or B, between the free water present in said dispersion and polyurethane hardener precursor back to formation of said initial polyurethane hardener precur› sor: 

A) 

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B) 

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wherein said polyurethane hardener is a compound with at least an amine and possible also a hydroxyl function› ality and wherein said reversible reaction (2; 2al) takes place during the entire retention time of the dispersion in the sealed can, so that the amount of free water (Wl) is unchanged and remains between 1-10000 ppm, pref› erably 1-6000 ppm between two successive uses of the can. 

2. A method for preventing hardener compounds to be formed from hardener precursors and extending shelf life of the dispersion in a sealed and pressurized aerosol can comprising a paint forming dispersion which contains after sealing the can: liquefied propellant, polyurethane resins of an amount W2 epoxy resins of an amount W 4, hardener precursor of an amount W3 of said polyurethane resins and hardener precursors of said epoxy resins of an amount W5, 

wherein said polyurethane hardener precursors and epoxy hardener precursors are selected from the group com› prising of an imine, an enamine, a Mannich base, a Schiff’s base, an oxazole, preferable an oxazolidine, an aldimine and mixtures thereof, free water of amount Wl, which amount Wl is in the range of 1-10000 ppm, preferably 1-6000 ppm and brought into said can 

