US 2020/0190338 Al  19  Jun. 18,2020  [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:  [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:  [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.  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,  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 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  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,  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.  [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).  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:  the dispersion contains also ketones, and a weak acid, as  a catalyst, to prevent formation of the polyurethane  hardeners from said polyurethane hardener precursors,  polyurethane resins are selected from the group which  composes of MDI, HDI, IPDI, TDI and phenol blocked  TDI prepolymers,  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  benzyl alcohol  Anti-foam additive  Acetone  Methoxy propylether  Hardener precursor  flow additive  slip additive  1.6902 kg  0.7512 kg  51.8891 kg  9.3900 kg  8,1581 kg  0.1878 kg  0.1878 kg  3.7560 kg  Solvesso 100 (100% aromatic solvent)  Xylene  22.5360 kg  These ingredients will be mixed with a  mixer (rotation speed ca 800 rpm)  Carboxylic acid  1.1750 kg  After adding the carbolic acid, the mix will  gain be mixed for app 5 min (800 rpm)  Epoxy binder  9.6259 kg  Poly Urethane prepolymer (HD!)  13.6159 kg  After adding the binders, the total will be  mixed for app 5 min (800 rpm)  Polyurethane  +  ketone  hardener  Weak  acid  --------- Polyurethane  hardener  precursor  (2a; 2al)  H20  (free water)  or  Polyurethane  Azole  H$_{2}$0  -- hardener  precursor  (2b)  Weak  acid  (2a; 2al)  Polyurethane  +  ketone  - Polyurethane  +  H20  (free water)  hardener  hardener  precursors  A)  B) 