US 2020/0190338 Al  7  Jun.  18,2020  [0107]  The aerosol dispersion of the present invention  comprises at least one latent hardener precursor which is  selected from the group consisting of an imine, an enamine,  an oxazolidine, a Mannich base, a Schiff’s base, aldimine  and mixtures thereof.  [0094]  There is also another significant advantage since  the curing reaction begins only when the dispersion is  sprayed outside of the sealed can; the surface quality of the  paint will be better compared to prior art 2 compartment  2K-products wherein curing begins already in the can after  [0093]  As the reaction between the amine compound  and/or hydroxyl compound and the polyurethane resin and  the possible epoxy group occurs outside of the aerosol can,  the formulation inside the can stays stable. No additional  moisture from the air gets inside the can, because pressure  inside the can is greater than the pressure outside of the can.  Compared to prior art wherein a kind of stable environment  is achieved after removing water, this kind of moisture  control method have a definitive advantage of being able to  withstand moisture variations.  [0106]  In the dispersion of the present invention, the  polyurethane resin does not substantially react with the  hardener precursor or with the weak acid of the aerosol  dispersion.  [0105]  Naturally, the type of weak acid has a further  influence on the formulation properties, as well as the  amount of weak acid used.  [0104]  In another embodiment the weak acid is selected  from those having the  pKa  value within the range from 4.2  to 4.9 for optimized stability in storage and performance in  use.  [0103]  In one embodiment the weak acid is selected from  those having  pKa  value within the range from 3 to 5, for  efficiently maintaining the equilibrium of the formulation at  the hardener precursor’s side.  [0102]  More particularly, the present invention provides a  two-component aerosol dispersion containing paint forming  chemicals comprising at least one polyurethane resin and at  least one hardener precursor, and at least one propellant. The  formulation further contains at least a portion of a weak acid  having the pKa value in the range from 1.2 to 5.2.  [0092]  The stable mixture of the polyurethane resin and  the polyurethane precursor and the weak acid, together with  at least one propellant, is packed as an aerosol dispersion  into a conventional one-chamber aerosol can. As the aerosol  formulation comprising polyurethane resins and hardener  precursor is sprayed from the can, a cloud of fine particles  suspended in gas or air is formed picking up water (mois› ture) from the air. The absorbance of water will have an  effect on the hardener precursor, such as oxazole, preferable  oxazolidine or bisoxazolidine, imine, enamine, aldimine  and/or Mannich base or Schiff’s base compound. With the  relatively overload of water present in the atmospheric air,  the hardener precursor will hydrolyze and form a compound  having amine and/or hydroxyl functionality(ties) which will  react with the polyurethane resin an a possible epoxy resin  and create a cross linking film. Together with the other  paint/adhesive related ingredient this will form the eventual  end product (paint) which can be an adhesive, a colored top  coat, a varnish, lacquer, a primer or a clear coat.  [0101]  the components are brought into contact with each  other once taking the can into use.  [0099]  In one aspect, the present invention provides a  two-component aerosol formulation suitable for use in an  aerosol can, such as in a single chamber aerosol can.  Naturally, also multiple chamber cans can be used, in a case  paint forming chemicals, comprising epoxy resin and a  hardener precursor,  [0091]  The aerosol formulation may even be prepared  under ambient conditions without any particular need for  pre-drying the components of aerosol formulation before  packing them into aerosol can or operating under inert gas,  such as nitrogen, atmosphere while preparing the formula› tion from its components or filling the can. Even technical  grade or industrial quality components comprising hardener  precursors may be used although they provide water into the  formulation inside the can.  [0098]  By ambient is meant the typical environmental  conditions, temperature, pressure and humidity, prevailing at  the point of preparation of the formulation at regular indus› trial surroundings.  [0097]  The preparation of the formulation and can con› taining the formulation is essentially simplified as no pro› tection gas or pre-drying steps are necessary. The manufac› turing can take place in ambient conditions using regular  mixing and can filling techniques.  [0090]  The dry paint film prepared from said mixture  should have the adhesion >450 psi, in PosiTest.  [0089]  The dry paint film prepared from said mixture  should have the Konig-hardness over 40 after 10 hand over  100 after 120 h of drying-time, measured with pendel  hardness meter.  [0096]  Shelf life of the can containing the formulation is  at least a year, possibly up to 3 years or even more.  Moreover, an aerosol can containing the formulation is  easier and faster to use, because there is no need to first  separately mix the hardener and the binder as is the case with  known solutions.  [0088]  The dry paint film (undercoat, finishing coat or  lacquer) prepared from said mixture should have gloss in the  range of 10-100 preferable over 90, under an angle of 60°.  [0087]  The use of catalytic amount of weak acid in the  present method and the aerosol dispersion used in this  method enables making high quality paints regardless if all  it is used at once or reused after an extended time period  [0095]  As the formulation stays stable inside the can, only  a desired portion of the two-component aerosol formulation  may be used at a time. That is, the whole formulation does  not have to be used at once, since the formulation remains  stable inside the can due to reaction 2a in which hydrolyzed  products of hardener precursors will not proceed into for› mation of hardener amines but back to forming original  hardener precursors.  puncturing said compartments so that their content is mixed  (at least the hardener and the hardener precursor).  [0086]  In a preferable embodiment of the present inven› tion the weak acid is added into paint forming dispersion an  amount that will contribute to a higher adhesion to the paint  surface by etching.  amount of a weak acid means that there is 0.1 to 10% of  weak acid by weight (w/w) of the aerosol dispersion, pref› erably from 0.1 to 5%, more preferably from 0.25 to 2% of  weak acid by weight (w/w) of the aerosol dispersion.  [0100]  a weak acid and a possible solvent for obtaining  a mixture; 