| 摘要 |
PURPOSE:To increase the adhesive strength between a metal and a cold-setting elastomer to that of the metal and a normal polyurethane elastomer, by using a primer provided by adding a strong acid to a stoving primer composed of a polyvinyl acetal resin modified with a formaldehyde-type resin. CONSTITUTION:A polyvinyl acetal resin is thermally reacted with a formaldehyde- condensed thermosetting resin (e.g. phenolic resin etc.) in an organic solvent, e.g. toluene etc. to give a solution of the stoving primer composed of the modified resin in the organic solvent (pref. the concentration of 3-30wt%). A strong acid, e.g. phosphoric acid, p-toluenesulfonic acid, etc., (preferably 1-15wt% on the basis of the modified resin) is added to the solution as a catalyst. The primer containing the strong acid is coated to a metal surface and if desired preheated at <=60 deg.C. A cold-setting and two-pack type polyurethane is extruded thereon, and cured and at the same time, bonded with the metal. EFFECT:Free from lowering of the adhesive strength even in dipping in water. |
