| 摘要 |
<p>1346732 Electrostatic coating BEATRICE FOODS CO 18 Jan 1972 [18 Jan 1971] 2429/72 Heading B2E [Also in Division C3] In a method of coating a charged mixture of powders is applied to a conductive surface by electrostatic deposition on to an electrically neutral or oppositely charged surface, the mixture being subsequently fused to produce the coating. The mixture comprises: (I) a first film - forming, electrically non - conductive organic and/or inorganic powders and one or more of the following powders (II) a second film-forming electrically non-conductive organic and/or inorganic polymer, the dielectric constant of I and II differing by at least 0.1 and the specific gravity of the polymer having the higher dielectric constant being at least 0.1 greater than the specific gravity of the polymer having the lower dielectric constant; (III) at least one non-migratory electrically conductive metal having a specific gravity at least 3 times that of I, or (IV) at least one electrically conductive non-metal having a specific gravity at least 1.5 times that of I. On fusing the coating III or IV remains substantially in contact with the. substrate leaving a surface of polymer. III is defined as a metal which does not migrate to the surface during fusing. Suitable III are Fe, Zn, Cu, Ni, Sn, Cr, Ti, Zr Pb and alloys thereof, brass and stainless steel. Bronze and Al are not suitable as they migrate to the surface. In an example I is a carbon black pigmented epoxy resin containing dicyandiamide and an amine accelerator, II is polyethylene powder and III Zn dust. The mixture was coated on to an earthed steel panel which was baked at 300‹F for 3 minutes and raised to 420‹F over 10 minutes. After cooling the coating comprises a flat essentially clean coat on top overlying a zinc rich coating adjacent to the substrate.</p> |
